| Daisuke Mizuno | Last modified date：2023.11.22 |
Professor /
material physics /
Department of Physics /
Faculty of Sciences
Papers
| 1. | H. Ebata, K. Umeda, K. Nishizawa, W. Nagao, S. Inokuchi, Y. Sugino, T. Miyamoto, and D. Mizuno, Activity-dependent glassy cell mechanics Ⅰ: Mechanical properties measured with active microrheology , Biophysical Journal, 10.1016/j.bpj.2023.04.011, 122, 10, 1781-1793, 2023.06, [URL], Active microrheology was conducted in living cells by applying an optical-trapping force to vigorously-fluctuating tracer beads with feedback-tracking technology. The complex shear modulus G(\omega)=G'(\omega)-iG''(\omega) was measured in HeLa cells in an epithelial-like confluent monolayer. We found that G(\omega)\propto(-i\omega)^\frac{1}{2} over a wide range of frequencies (1 Hz . |
| 2. | Nonthermal Fluctuation Accelerates Molecular Motor Kinesin. |
| 3. | H. Ebata, K. Umeda, K. Nishizawa, W. Nagao, S. Inokuchi, Y. Sugino, T. Miyamoto, Daisuke Mizuno, Activity-dependent glassy cell mechanics I : Mechanical properties measured with active microrheology, bioRxiv, 10.1101/2022.09.02.506288, 122, 10, 1781-1793, 2022.09, Active microrheology was conducted in living cells by applying an optical-trapping force to vigorously-fluctuating tracer beads with feedback-tracking technology. The complex shear viscoelastic modulus Intracellular mechanical properties were measured using optical-trap-based microrheology. Despite expectations to the contrary, shear viscoelasticity was hardly affected by reorganization of cytoskeletal structures during cell-cycle progression (G1 to S and G2 phases), nor by artificial disruption of the actin cytoskeleton induced by chemical inhibitors. Rather, the mechanics of cell interiors is governed by the glassy cytoplasm. Cells depleted of ATP solidified, whereas living cells that maintained metabolic activities were more fluid-like. Instead of a completely fluid response, however, we observed a characteristic power-law viscoelasticity |
| 4. | N Honda, K Shiraki, F van Esterik, S Inokuchi, H Ebata, D Mizuno, Nonlinear master relation in microscopic mechanical response of semiflexible biopolymer networks, New Journal of Physics, 10.1088/1367-2630/ac6902, 24, 5, 053031-053031, 2022.05, Abstract A network of semiflexible biopolymers, known as the cytoskeleton, and molecular motors play fundamental mechanical roles in cellular activities. The cytoskeletal response to forces generated by molecular motors is profoundly linked to physiological processes. However, owing to the highly nonlinear mechanical properties, the cytoskeletal response on the microscopic level is largely elusive. The aim of this study is to investigate the microscopic mechanical response of semiflexible biopolymer networks by conducting microrheology (MR) experiments. Micrometer-sized colloidal particles, embedded in semiflexible biopolymer networks, were forced beyond the linear regime at a variety of conditions by using feedback-controlled optical trapping. This high-bandwidth MR technology revealed an affine elastic response, which showed stiffening upon local forcing. After scaling the stiffening behaviors, with parameters describing semiflexible networks, a collapse onto a single master curve was observed. The physics underlying the general microscopic response is presented to justify the collapse, and its potentials/implications to elucidate cell mechanics is discussed.. |
| 5. | Takayuki Ariga, Keito Tateishi, Michio Tomishige, Daisuke Mizuno, Noise-Induced Acceleration of Single Molecule Kinesin-1., Physical review letters, 10.1103/PhysRevLett.127.178101, 127, 17, 178101-178101, 2021.10, The movement of single kinesin molecules was observed while applying noisy external forces that mimic intracellular active fluctuations. We found kinesin accelerates under noise, especially when a large hindering load is added. The behavior quantitatively conformed to a theoretical model that describes the kinesin movement with simple two-state reactions. The universality of the kinetic theory suggests that intracellular enzymes share a similar noise-induced acceleration mechanism, i.e., active fluctuations in cells are not just noise but are utilized to promote various physiological processes.. |
| 6. | D Mizuno, C Tardin, C F Schmidt, Rapid local compression in active gels is caused by nonlinear network response., Soft matter, 10.1039/c9sm02362c, 2020.09, The actin cytoskeleton in living cells generates forces in conjunction with myosin motor proteins to directly and indirectly drive essential cellular processes. The semiflexible filaments of the cytoskeleton can respond nonlinearly to the collective action of motors. We here investigate mechanics and force generation in a model actin cytoskeleton, reconstituted in vitro, by observing the response and fluctuations of embedded micron-scale probe particles. Myosin mini-filaments can be modeled as force dipoles and give rise to deformations in the surrounding network of cross-linked actin. Anomalously correlated probe fluctuations indicate the presence of rapid local compression or draining of the network that emerges in addition to the ordinary linear shear elastic (incompressible) response to force dipoles. The anomalous propagation of compression can be attributed to the nonlinear response of actin filaments to the microscopic forces, and is quantitatively consistent with motor-generated large-scale stiffening of the gels.. |
| 7. | Yujiro Sugino, Masahiro Ikenaga, Daisuke Mizuno, Optimization of optical trapping and laser interferometry in biological cells, Applied Sciences (Switzerland), 10.3390/app10144970, 10, 14, 2020.07, Optical trapping and laser interferometry enable the non-invasive manipulation of colloids, which can be used to investigate the microscopic mechanics of surrounding media or bound macromolecules. For efficient trapping and precise tracking, the sample media must ideally be homogeneous and quiescent whereas such conditions are usually not satisfied in vivo in living cells. In order to investigate mechanics of the living-cell interior, we introduced (1) the in-situ calibration of optical trapping and laser interferometry, and (2) 3-D feedback control of a sample stage to stably track a colloidal particle. Investigating systematic errors that appear owing to sample heterogeneity and focal offsets of a trapping laser relative to the colloidal probe, we provide several important caveats for conducting precise optical micromanipulation in living cells. On the basis of this study, we further improved the performance of the techniques to be used in cells, by optimizing the position sensitivity of laser interferometry and the stability of the feedback simultaneously.. |
| 8. | Yujiro Sugino, Masahiro Ikenaga, Daisuke Mizuno, Optimization of Optical Trapping and Laser Interferometry in Biological Cells, Applied Sciences, 10.3390/app10144970, 10, 14, 4970-4970, 2020.07, Optical trapping and laser interferometry enable the non-invasive manipulation of colloids, which can be used to investigate the microscopic mechanics of surrounding media or bound macromolecules. For efficient trapping and precise tracking, the sample media must ideally be homogeneous and quiescent whereas such conditions are usually not satisfied in vivo in living cells. In order to investigate mechanics of the living-cell interior, we introduced (1) the in-situ calibration of optical trapping and laser interferometry, and (2) 3-D feedback control of a sample stage to stably track a colloidal particle. Investigating systematic errors that appear owing to sample heterogeneity and focal offsets of a trapping laser relative to the colloidal probe, we provide several important caveats for conducting precise optical micromanipulation in living cells. On the basis of this study, we further improved the performance of the techniques to be used in cells, by optimizing the position sensitivity of laser interferometry and the stability of the feedback simultaneously.. |
| 9. | Ryo Akiyama, Masahiko Annaka, Daisuke Kohda, Hiroyuki Kubota, Yusuke Maeda, Nobuaki Matsumori, Daisuke Mizuno, Norio Yoshida, Biophysics at Kyushu University, Biophysical Reviews, 10.1007/s12551-020-00643-2, 12, 2, 245-247, 2020.04. |
| 10. | Ryo Akiyama, Masahiko Annaka, Daisuke Kohda, Hiroyuki Kubota, Yusuke Maeda, Nobuaki Matsumori, Daisuke Mizuno, Norio Yoshida, Biophysics at Kyushu University., Biophysical reviews, 10.1007/s12551-020-00643-2, 12, 2, 245-247, 2020.04. |
| 11. | Takayuki Ariga, Michio Tomishige, Daisuke Mizuno, Experimental and theoretical energetics of walking molecular motors under fluctuating environments., Biophysical reviews, 10.1007/s12551-020-00684-7, 12, 2, 503-510, 2020.04, Molecular motors are nonequilibrium open systems that convert chemical energy to mechanical work. Their energetics are essential for various dynamic processes in cells, but largely remain unknown because fluctuations typically arising in small systems prevent investigation of the nonequilibrium behavior of the motors in terms of thermodynamics. Recently, Harada and Sasa proposed a novel equality to measure the dissipation of nonequilibrium small systems. By utilizing this equality, we have investigated the nonequilibrium energetics of the single-molecule walking motor kinesin-1. The dissipation from kinesin movement was measured through the motion of an attached probe particle and its response to external forces, indicating that large hidden dissipation exists. In this short review, aiming to readers who are not familiar with nonequilibrium physics, we briefly introduce the theoretical basis of the dissipation measurement as well as our recent experimental results and mathematical model analysis and discuss the physiological implications of the hidden dissipation in kinesin. In addition, further perspectives on the efficiency of motors are added by considering their actual working environment: living cells.. |
| 12. | Takayuki Ariga, Michio Tomishige, Daisuke Mizuno, Experimental and theoretical energetics of walking molecular motors under fluctuating environments, Biophysical Reviews, 10.1007/s12551-020-00684-7, 12, 2, 503-510, 2020.01, Molecular motors are nonequilibrium open systems that convert chemical energy to mechanical work. Their energetics are essential for various dynamic processes in cells, but largely remain unknown because fluctuations typically arising in small systems prevent investigation of the nonequilibrium behavior of the motors in terms of thermodynamics. Recently, Harada and Sasa proposed a novel equality to measure the dissipation of nonequilibrium small systems. By utilizing this equality, we have investigated the nonequilibrium energetics of the single-molecule walking motor kinesin-1. The dissipation from kinesin movement was measured through the motion of an attached probe particle and its response to external forces, indicating that large hidden dissipation exists. In this short review, aiming to readers who are not familiar with nonequilibrium physics, we briefly introduce the theoretical basis of the dissipation measurement as well as our recent experimental results and mathematical model analysis and discuss the physiological implications of the hidden dissipation in kinesin. In addition, further perspectives on the efficiency of motors are added by considering their actual working environment: living cells.. |
| 13. | Measuring Dissipation of Molecular Motor Kinesin. |
| 14. | T. Ariga, M. Tomishige, and D. Mizuno, Nonequilibrium Energetics of Molecular Motor Kinesin, Physical Review Letters, 10.1103/PhysRevLett.121.218101, 121, 218101 , 2018.11, Nonequilibrium energetics of single molecule translational motor kinesin was investigated by measuring heat dissipation from the violation of the fluctuation-response relation of a probe attached to the motor using optical tweezers. The sum of the dissipation and work did not amount to the input free energy change, indicating large hidden dissipation exists. Possible sources of the hidden dissipation were explored by analyzing the Langevin dynamics of the probe, which incorporates the two-state Markov stepper as a kinesin model. We conclude that internal dissipation is dominant.. |
| 15. | Takayuki Ariga, Michio Tomishige, Daisuke Mizuno, Nonequilibrium Energetics of Molecular Motor Kinesin, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.121.218101, 121, 21, 218101-218101, 2018.11, Nonequilibrium energetics of single molecule translational motor kinesin was investigated by measuring heat dissipation from the violation of the fluctuation-response relation of a probe attached to the motor using optical tweezers. The sum of the dissipation and work did not amount to the input free energy change, indicating large hidden dissipation exists. Possible sources of the hidden dissipation were explored by analyzing the Langevin dynamics of the probe, which incorporates the two-state Markov stepper as a kinesin model. We conclude that internal dissipation is dominant.. |
| 16. | Takayuki Ariga, Michio Tomishige, Daisuke Mizuno, Nonequilibrium Energetics of Single Molecule Motor, Kinesin-1, BIOPHYSICAL JOURNAL, 10.1016/j.bpj.2017.11.2783, 114, 3, 509A-509A, 2018.02. |
| 17. | Takuya Hara, Taishi Fujishiro, Daisuke Mizuno, Nobuyuki Ishikawa, Eiji Tada, Mitsuo Kimura, Determination of sour environment from equal hydrogen concentration approach, 28th International Ocean and Polar Engineering Conference, ISOPE 2018 Proceedings of the 28th International Ocean and Polar Engineering Conference, ISOPE 2018, 2018-June, 202-205, 2018.01, Severity of sour environment determined in accordance with ISO15156-2 or NACE MR0175 for carbon and low-alloy steels has been proposed. The critical line of each region which was indicated as regions 0, 1, 2 and 3 was thought to be determined based on experimental sulfide stress cracking (SSC) results of API grade N80 and P110. SSC or hydrogen induced cracking (HIC) occurs if hydrogen concentration entering into steel from the environment exceeds the critical hydrogen concentration in steel. The severity of sour environment was introduced and proposed based on equal hydrogen concentration entering into steel from the environment from the viewpoint of HIC.. |
| 18. | Kenji Nishizawa, Kei Fujiwara, Masahiro Ikenaga, Nobushige Nakajo, Miho Yanagisawa, Daisuke Mizuno, Universal glass-forming behavior of in vitro and living cytoplasm, SCIENTIFIC REPORTS, 10.1038/s41598-017-14883-y, 7, 1, 15143-15143, 2017.11, Physiological processes in cells are performed efficiently without getting jammed although cytoplasm is highly crowded with various macromolecules. Elucidating the physical machinery is challenging because the interior of a cell is so complex and driven far from equilibrium by metabolic activities. Here, we studied the mechanics of in vitro and living cytoplasm using the particle-tracking and manipulation technique. The molecular crowding effect on cytoplasmic mechanics was selectively studied by preparing simple in vitro models of cytoplasm from which both the metabolism and cytoskeletons were removed. We obtained direct evidence of the cytoplasmic glass transition; a dramatic increase in viscosity upon crowding quantitatively conformed to the super-Arrhenius formula, which is typical for fragile colloidal suspensions close to jamming. Furthermore, the glass-forming behaviors were found to be universally conserved in all the cytoplasm samples that originated from different species and developmental stages; they showed the same tendency for diverging at the macromolecule concentrations relevant for living cells. Notably, such fragile behavior disappeared in metabolically active living cells whose viscosity showed a genuine Arrhenius increase as in typical strong glass formers. Being actively driven by metabolism, the living cytoplasm forms glass that is fundamentally different from that of its non-living counterpart.. |
| 19. | Kenji Nishizawa, Marcel Bremerich, Heev Ayade, Christoph F. Schmidt, Takayuki Ariga, Daisuke Mizuno, Feedback-tracking microrheology in living cells, Science Advances, 10.1126/sciadv.1700318, 3, 9, e1700318-e1700318, 2017.09, Living cells are composed of active materials, in which forces are generated by the energy derived from metabolism. Forces and structures self-organize to shape the cell and drive its dynamic functions. Understanding the out-of-equilibrium mechanics is challenging because constituent materials, the cytoskeleton and the cytosol, are extraordinarily heterogeneous, and their physical properties are strongly affected by the internally generated forces. We have analyzed dynamics inside two types of eukaryotic cells, fibroblasts and epithelial-like HeLa cells, with simultaneous active and passive microrheology using laser interferometry and optical trapping technology. We developed a method to track microscopic probes stably in cells in the presence of vigorous cytoplasmic fluctuations, by using smooth three-dimensional (3D) feedback of a piezo-actuated sample stage. To interpret the data, we present a theory that adapts the fluctuation-dissipation theorem (FDT) to out-of-equilibrium systems that are subjected to positional feedback, which introduces an additional nonequilibrium effect. We discuss the interplay between material properties and nonthermal force fluctuations in the living cells that we quantify through the violations of the FDT. In adherent fibroblasts, we observed a well-known polymer network viscoelastic response where the complex shear modulus scales as G* ∝ (-iω)3/4. In the more 3D confluent epithelial cells, we found glassy mechanics with G* ∝ (-iω)1/2 that we attribute to glassy dynamics in the cytosol. The glassy state in living cells shows characteristics that appear distinct from classical glasses and unique to nonequilibrium materials that are activated by molecular motors.. |
| 20. | Kenji Nishizawa, Marcel Bremerich, Heev Ayade, Christoph F. Schmidt, Takayuki Ariga, Daisuke Mizuno, Feedback-tracking microrheology in living cells, SCIENCE ADVANCES, 10.1126/sciadv.1700318, 3, 9, e1700318, 2017.09, Living cells are composed of active materials, in which forces are generated by the energy derived from metabolism. Forces and structures self-organize to shape the cell and drive its dynamic functions. Understanding the out-of-equilibrium mechanics is challenging because constituent materials, the cytoskeleton and the cytosol, are extraordinarily heterogeneous, and their physical properties are strongly affected by the internally generated forces. We have analyzed dynamics inside two types of eukaryotic cells, fibroblasts and epithelial-like HeLa cells, with simultaneous active and passive microrheology using laser interferometry and optical trapping technology. We developed a method to track microscopic probes stably in cells in the presence of vigorous cytoplasmic fluctuations, by using smooth three-dimensional (3D) feedback of a piezo-actuated sample stage. To interpret the data, we present a theory that adapts the fluctuation-dissipation theorem (FDT) to out-of-equilibrium systems that are subjected to positional feedback, which introduces an additional nonequilibrium effect. We discuss the interplay between material properties and nonthermal force fluctuations in the living cells that we quantify through the violations of the FDT. In adherent fibroblasts, we observed a well-known polymer network viscoelastic response where the complex shear modulus scales as G* proportional to (-i omega)(3/4). In the more 3D confluent epithelial cells, we found glassy mechanics with G* proportional to (-i omega)(1/2) that we attribute to glassy dynamics in the cytosol. The glassy state in living cells shows characteristics that appear distinct from classical glasses and unique to nonequilibrium materials that are activated by molecular motors.. |
| 21. | Kenji Nishizawa, Marcel Bremerich, Heev Ayade, Christoph F. Schmidt, Takayuki Ariga, Daisuke Mizuno, Feedback-tracking microrheology in living cells, Science Advances, 10.1126/sciadv.1700318, 3, 9, 2017.09, Feedback-tracking microrheology, developed to study nonequilibrium mechanics of active materials, revealed glassy cell dynamics.. |
| 22. | Takashi Kurihara, Msato Aridome, Heev Ayade, Irwin Zaid, Daisuke Mizuno, Non-Gaussian limit fluctuations in active swimmer suspensions, PHYSICAL REVIEW E, 10.1103/PhysRevE.95.030601, 95, 3, 030601-030601, 2017.03, We investigate the hydrodynamic fluctuations in suspensions of swimming microorganisms (Chlamydomonas) by observing the probe particles dispersed in the media. Short-term fluctuations of probe particles were superdiffusive and displayed heavily tailed non-Gaussian distributions. The analytical theory that explains the observed distribution was derived by summing the power-law-decaying hydrodynamic interactions from spatially distributed field sources (here, swimming microorganisms). The summing procedure, which we refer to as the physical limit operation, is applicable to a variety of physical fluctuations to which the classical central limiting theory does not apply. Extending the analytical formula to compare to experiments in active swimmer suspensions, we show that the non-Gaussian shape of the observed distribution obeys the analytic theory concomitantly with independently determined parameters such as the strength of force generations and the concentration of Chlamydomonas. Time evolution of the distributions collapsed to a single master curve, except for their extreme tails, for which our theory presents a qualitative explanation. Investigations thereof and the complete agreement with theoretical predictions revealed broad applicability of the formula to dispersions of active sources of fluctuations.. |
| 23. | Irwin Zaid, Daisuke Mizuno, Analytical Limit Distributions from Random Power-Law Interactions, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.117.030602, 117, 3, 030602-030602, 2016.07, Nature is full of power-law interactions, e.g., gravity, electrostatics, and hydrodynamics. When sources of such fields are randomly distributed in space, the superposed interaction, which is what we observe, is naively expected to follow a Gauss or Levy distribution. Here, we present an analytic expression for the actual distributions that converge to novel limits that are in between these already-known limit distributions, depending on physical parameters, such as the concentration of field sources and the size of the probe used to measure the interactions. By comparing with numerical simulations, the origin of non-Gauss and non-Levy distributions are theoretically articulated.. |
| 24. | Daisuke Mizuno, Suguru Kinoshita, Lara Gay Villaruz, High-frequency affine mechanics and nonaffine relaxation in a model cytoskeleton, PHYSICAL REVIEW E, 10.1103/PhysRevE.89.042711, 89, 4, 2014.04, The cytoskeleton is a network of crosslinked, semiflexible filaments, and it has been suggested that it has properties of a glassy state. Here we employ optical-trap-based microrheology to apply forces to a model cytoskeleton and measure the high-bandwidth response at an anterior point. Simulating the highly nonlinear and anisotropic stress-strain propagation assuming affinity, we found that theoretical predictions for the quasistatic response of semiflexible polymers are only realized at high frequencies inaccessible to conventional rheometers. We give a theoretical basis for determining the frequency when both affinity and quasistaticity are valid, and we discuss with experimental evidence that the relaxations at lower frequencies can be characterized by the experimentally obtained nonaffinity parameter.. |
| 25. | David A. Head, Emi Ikebe, Akiko Nakamasu, Peijuan Zhang, Lara Gay Villaruz, Suguru Kinoshita, Shoji Ando, Daisuke Mizuno, High-frequency affine mechanics and nonaffine relaxation in a model cytoskeleton, PHYSICAL REVIEW E, 10.1103/PhysRevE.89.042711, 89, 4, 042711-042711, 2014.04, The cytoskeleton is a network of crosslinked, semiflexible filaments, and it has been suggested that it has properties of a glassy state. Here we employ optical-trap-based microrheology to apply forces to a model cytoskeleton and measure the high-bandwidth response at an anterior point. Simulating the highly nonlinear and anisotropic stress-strain propagation assuming affinity, we found that theoretical predictions for the quasistatic response of semiflexible polymers are only realized at high frequencies inaccessible to conventional rheometers. We give a theoretical basis for determining the frequency when both affinity and quasistaticity are valid, and we discuss with experimental evidence that the relaxations at lower frequencies can be characterized by the experimentally obtained nonaffinity parameter.. |
| 26. | Irwin Zaid, Heev L. Ayade, Daisuke Mizuno, Athermal Fluctuations of Probe Particles in Active Cytoskeletal Network, BIOPHYSICAL JOURNAL, 10.1016/j.bpj.2013.11.973, 106, 2, 171A-171A, 2014.01. |
| 27. | Masato Aridome, Takashi Kurihara, Heev Ayade, Irwin Zaid, Daisuke Mizuno, Non-Gauss Athermal Fluctuations in Bacterial Bath, BIOPHYSICAL JOURNAL, 10.1016/j.bpj.2013.11.3218, 106, 2, 580A-580A, 2014.01. |
| 28. | David A. Head, Daisuke Mizuno, Local mechanical response in semiflexible polymer networks subjected to an axisymmetric prestress, PHYSICAL REVIEW E, 10.1103/PhysRevE.88.022717, 88, 2, 022717-022717, 2013.08, Analytical and numerical calculations are presented for the mechanical response of fiber networks in a state of axisymmetric prestress, in the limit where geometric nonlinearities such as fiber rotation are negligible. This allows us to focus on the anisotropy deriving purely from the nonlinear force-extension curves of individual fibers. The number of independent elastic coefficients for isotropic, axisymmetric, and fully anisotropic networks are enumerated before deriving expressions for the response to a locally applied force that can be tested against, e.g., microrheology experiments. Localized forces can generate anisotropy away from the point of application, so numerical integration of nonlinear continuum equations is employed to determine the stress field, and induced mechanical anisotropy, at points located directly behind and in front of a force monopole. Results are presented for the wormlike chain model in normalized forms, allowing them to be easily mapped to a range of systems. Finally, the relevance of these findings to naturally occurring systems and directions for future investigation are discussed.. |
| 29. | Nadja Nijenhuis, Daisuke Mizuno, Jos A. E. Spaan, Christoph F. Schmidt, High-resolution microrheology in the pericellular matrix of prostate cancer cells, JOURNAL OF THE ROYAL SOCIETY INTERFACE, 10.1098/rsif.2011.0825, 9, 73, 1733-1744, 2012.08, Many cells express a membrane-coupled external mechanical layer, the pericellular matrix (PCM), which often contains long-chain polymers. Its role and properties are not entirely known, but its functions are believed to include physical protection, mechanosensing, chemical signalling or lubrication. The viscoelastic response of the PCM, with polysaccharides as the main structural components, is therefore crucial for the understanding of its function. We have here applied microrheology, based on optically trapped micrometre-sized colloids, to the PCM of cultured PC3 prostate cancer cells. This technology allowed us to measure the extremely soft response of the PCM, with approximately 1 mu m height resolution. Exogen-ously added aggrecan, a hyaluronan-binding proteoglycan, caused a remarkable increase in thickness of the viscoelastic layer and also triggered filopodia-like protrusions. The viscoelastic response of the PCM, however, did not change significantly.. |
| 30. | N. Nijenhuis, D. Mizuno, J. A. E. Spaan, and C. F. Schmidt, "High-resolution microrheology in the pericellular matrix of prostate cancer cells", J. Royal Society Interface, 2012.06, Many cells express a membrane-coupled external mechanical layer, the pericellular matrix (PCM), which often contains long-chain polymers. Its role and properties are not entirely known, but its functions are believed to include physical protection, mechanosensing, chemical signalling or lubrication. The viscoelastic response of the PCM, with polysaccharides as the main structural components, is therefore crucial for the understanding of its function. We have here applied microrheology, based on optically trapped micrometre-sized colloids, to the PCM of cultured PC3 prostate cancer cells. This technology allowed us to measure the extremely soft response of the PCM, with approximately 1 µm height resolution. Exogenously added aggrecan, a hyaluronan-binding proteoglycan, caused a remarkable increase in thickness of the viscoelastic layer and also triggered filopodia-like protrusions. The viscoelastic response of the PCM, however, did not change significantly.. |
| 31. | T. Toyota, D. A. Head, C. F. Schmidt and D. Mizuno , Non-Gaussian athermal fluctuations in active gels, Soft Matter, 10.1039/c0sm00925c , 7, 7 , 3234-3239 , 2011.04. |
| 32. | Toshihiro Toyota, David A. Head, Christoph F. Schmidt, Daisuke Mizuno, Non-Gaussian athermal fluctuations in active gels, Soft Matter, 10.1039/c0sm00925c, 7, 7, 3234-3239, 2011, Dynamic networks designed to model the cell cytoskeleton can be reconstituted from filamentous actin, the motor protein myosin and a permanent cross-linker. They are driven out of equilibrium when the molecular motors are active. This gives rise to athermal fluctuations that can be recorded by tracking probe particles that are dispersed in the network. We have here probed athermal fluctuations in such "active gels'' using video microrheology. We have measured the full distribution of probe displacements, also known as the van Hove correlation function. The dominant influence of thermal or athermal fluctuations can be detected by varying the lag time over which the displacements are measured. We argue that the exponential tails of the distribution derive from single motors close to the probes, and we extract an estimate of the velocity of motor heads along the actin filaments. The distribution exhibits a central Gaussian region which we assume derives from the action of many independent motor proteins far from the probe particles when athermal fluctuations dominate. Recording the whole distribution rather than just the typically measured second moment of probe fluctuations (mean-squared displacement) thus allowed us to differentiate between the effect of individual motors and the collective action of many motors.. |
| 33. | D. A. Head, D. Mizuno, Nonlocal fluctuation correlations in active gels, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 10.1103/PhysRevE.81.041910, 81, 4, 2010.04, Many active materials and biological systems are driven far from equilibrium by embedded agents that spontaneously generate forces and distort the surrounding material. Probing and characterizing these athermal fluctuations are essential to understand the properties and behaviors of such systems. Here we present a mathematical procedure to estimate the local action of force-generating agents from the observed fluctuating displacement fields. The active agents are modeled as oriented force dipoles or isotropic compression foci, and the matrix on which they act is assumed to be either a compressible elastic continuum or a coupled network-solvent system. Correlations at a single point and between points separated by an arbitrary distance are obtained, giving a total of three independent fluctuation modes that can be tested with microrheology experiments. Since oriented dipoles and isotropic compression foci give different contributions to these fluctuation modes, ratiometric analysis allows us characterize the force generators. We also predict and experimentally find a high-frequency ballistic regime, arising from individual force-generating events in the form of the slow buildup of stress followed by rapid but finite decay. Finally, we provide a quantitative statistical model to estimate the mean filament tension from these athermal fluctuations, which leads to stiffening of active networks.. |
| 34. | 21pEF-3 Nonequilibrium Mechanics of Life. |
| 35. | D. Mizuno, R. G. Bacabac, C. Tardin, D. Head, C. F. Schmidt, High-resolution probing of cellular force transmission, Physical Review letters, 10.1103/PhysRevLett.102.168102 , 102, 16 , 168102 , 2009.08. |
| 36. | Nadja Nijenhuis, Daisuke Mizuno, Jos A. E. Spaan, Christoph F. Schmidt, Viscoelastic response of a model endothelial glycocalyx, PHYSICAL BIOLOGY, 10.1088/1478-3975/6/2/025014, 6, 2, 025014-025014, 2009.06, Many cells cover themselves with a multifunctional polymer coat, the pericellular matrix (PCM), to mediate mechanical interactions with the environment. A particular PCM, the endothelial glycocalyx (EG), is formed by vascular endothelial cells at their luminal side, forming a mechanical interface between the flowing blood and the endothelial cell layer. The glycosaminoglycan (GAG) hyaluronan (HA) is involved in the main functions of the EG, mechanotransduction of fluid shear stress and molecular sieving. HA, due to its length, is the only GAG in the EG or any other PCM able to form an entangled network. The mechanical functions of the EG are, however, impaired when any one of its components is removed. We here used microrheology to measure the effect of the EG constituents heparan sulfate, chondroitin sulfate, whole blood plasma and albumin on the high-bandwidth mechanical properties of a HA solution. Furthermore, we probed the effect of the hyaldherin aggrecan, a constituent of the PCM of chondrocytes, and very similar to versican (present in the PCM of various cells, and possibly in the EG). We show that components directly interacting with HA (chondroitin sulfate and aggrecan) can increase the viscoelastic shear modulus of the polymer composite.. |
| 37. | Daisuke Mizuno, Rommel Bacabac, Catherine Tardin, David Head, Christoph F. Schmidt, High-Resolution Probing of Cellular Force Transmission, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.102.168102, 102, 16, 168102-168102, 2009.04, Cells actively probe mechanical properties of their environment by exerting internally generated forces. The response they encounter profoundly affects their behavior. Here we measure in a simple geometry the forces a cell exerts suspended by two optical traps. Our assay quantifies both the overall force and the fraction of that force transmitted to the environment. Mimicking environments of varying stiffness by adjusting the strength of the traps, we found that the force transmission is highly dependent on external compliance. This suggests a calibration mechanism for cellular mechanosensing.. |
| 38. | Nadja Nijenhuis, Daisuke Mizuno, Jos A. E. Spaan, Christoph F. Schmidt, Microrheology of the pericellular matrix, BIOPHYSICAL JOURNAL, 96, 3, 523A-523A, 2009.02. |
| 39. | S. Jabbari-Farouji, M. Atakhorrami, D. Mizuno, E. Eiser, G. H. Wegdam, F. C. MacKintosh, Daniel Bonn, C. F. Schmidt, High-bandwidth viscoelastic properties of aging colloidal glasses and gels, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 10.1103/PhysRevE.78.061402, 78, 6, 2008.12, We report measurements of the frequency-dependent shear moduli of aging colloidal systems that evolve from a purely low-viscosity liquid to a predominantly elastic glass or gel. Using microrheology, we measure the local complex shear modulus G* (ω) over a very wide range of frequencies (from 1 Hz to 100 kHz). The combined use of one- and two-particle microrheology allows us to differentiate between colloidal glasses and gels-the glass is homogenous, whereas the colloidal gel shows a considerable degree of heterogeneity on length scales larger than 0.5 μm. Despite this characteristic difference, both systems exhibit similar rheological behaviors which evolve in time with aging, showing a crossover from a single-power-law frequency dependence of the viscoelastic modulus to a sum of two power laws. The crossover occurs at a time t0, which defines a mechanical transition point. We found that the data acquired during the aging of different samples can be collapsed onto a single master curve by scaling the aging time with t0. This raises questions about the prior interpretation of two power laws in terms of a superposition of an elastic network embedded in a viscoelastic background.. |
| 40. | D. Mizuno, D. A. Head, F. C. MacKintosh, C. F. Schmidt, Active and passive microrheology in equilibrium and nonequilibrium systems, Macromolecules, 10.1021/ma801218z, 41, 19, 7194-7202, 2008.10, Quantitatively measuring the mechanical properties of soft matter over a wide range of length and time scales, especially if a sample is as complex as typical biological materials, remains challenging. Living cells present a further complication because forces are generated within these nonequilibrium materials that can change material properties. We have here developed high-bandwidth techniques for active one- and two-particle microrheology to tackle these issues. By combining active micromanipulation of probe particles with an optical trap with high-resolution tracking of thermal motions of the very same particles by laser interferometry, we can both measure the mechanical properties of and, at the same time, identify nonequilibrium forces in soft materials. In both simple liquids and equilibrium cytoskeletal actin networks, active microrheology (AMR) proves to be less noise sensitive than and offers extended bandwidth (0.1 - 100 kHz) compared to passive microrheology (PMR), which merely tracks thermal motions. We confirm high-frequency power-law dynamics in equilibrium actin networks with two-particle AMR and also discuss low-frequency local mechanical response near probe particles which shows up in one-particle AMR. The combination of AMR and PMR allowed us to quantify nonthermal force fluctuations in actin networks driven by myosin motor proteins. Our approach offers a new direct way to investigate the nonequilibrium dynamics of living materials.. |
| 41. | S. Jabbari-Farouji, D. Mizuno, D. Derks, G. H. Wegdam, F. C. MacKintosh, C. F. Schmidt, D. Bonn, Effective temperatures from the fluctuation-dissipation measurements in soft glassy materials, EPL, 10.1209/0295-5075/84/20006, 84, 2, 2008.10, We have investigated the validity of the fluctuation-dissipation theorem (FDT) and the applicability of the concept of effective temperature in a number of non-equilibrium soft glassy materials. Using a combination of passive and active microrheology to measure displacement fluctuations and the mechanical response function of probe particles embedded in the materials, we have directly tested the validity of the FDT. Our results show no violation of the FDT over several decades in frequency (1-104 Hz) for hard-sphere colloidal glasses and colloidal glasses and gels of Laponite. We further extended the bandwidth of our measurements to lower frequencies (down to 0.1 Hz) using video microscopy to measure the displacement fluctuations, again without finding any deviations from the FDT.. |
| 42. | Nadja Nijenhuis, Daisuke Mizuno, Christoph F. Schmidt, Hans Vink, Jos A. E. Spaan, Microrheology of hyaluronan solutions: Implications for the endothelial glycocalyx, BIOMACROMOLECULES, 10.1021/bm800381z, 9, 9, 2390-2398, 2008.09, The endothelial glycocalyx (EG) is a complex biopolymer network produced by vascular endothelial cells that forms a layer with Multiple functions at the luminal side of blood vessels. The EG acts as an anti-adhesive protection layer, as a molecular sieve, as a chemical sensor site, and as a mechanotransducer of fluid shear stress to the underlying cell layer. A major component involved in these processes is the highly hydrated glycosaminoglycan (GAG) hyaluronan (HA). Here we used laser interferometry to measure the broadband mechanical response of reconstituted HA Solutions at close to physiological conditions. HA showed rheological behavior consistent with that of a flexible polymer. The elastic behavior observed for entangled HA networks showed reptational relaxation with a large distribution of time scales, which disappeared quickly (15 min) with the addition of hyaluronidase (HAase). We conclude that the broadband mechanical probing of model systems (HA solutions) provides quantitative data that are crucial to understand the mechanical response of the EG in vivo and its role in mechanosensing.. |
| 43. | R. G. Bacabac, D. Mizuno, A. Vatsa, C.F. Schmidt, F.C. MacKintosh, J. Van Loon, J. Klein-Nulend, and T. Smit, "Round versus flat : bone cell norphology, elasticity, and mechanosensing" Journal of biomechanics 41, (7), pp.1590-pp.1598b (2008), Journal of biomechanics, 2008.08. |
| 44. | Rommel G. Bacabac, Daisuke Mizuno, Christoph F. Schmidt, Fred C. MacKintosh, Jack J. W. A. Van Loon, Jenneke Klein-Nulend, Theo H. Smit, Round versus flat: Bone cell morphology, elasticity, and mechanosensing (vol 41, pg 1590, 2008), JOURNAL OF BIOMECHANICS, 10.1016/j.jbiomech.2008.01.035, 41, 12, 2786-2786, 2008.08. |
| 45. | M. Atakhorrami, D. Mizuno, G. H. Koenderink, T. B. Liverpool, F. C. MacKintosh, C. F. Schmidt, Short-time inertial response of viscoelastic fluids measured with Brownian motion and with active probes, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 10.1103/PhysRevE.77.061508, 77, 6, 2008.06, We have directly observed short-time stress propagation in viscoelastic fluids using two optically trapped particles and a fast interferometric particle-tracking technique. We have done this both by recording correlations in the thermal motion of the particles and by measuring the response of one particle to the actively oscillated second particle. Both methods detect the vortexlike flow patterns associated with stress propagation in fluids. This inertial vortex flow propagates diffusively for simple liquids, while for viscoelastic solutions the pattern spreads superdiffusively, depending on the shear modulus of the medium.. |
| 46. | D. Mizuno, M. Atakhorrami, K. M. Addas, J. X. Tang, G. H. Koenderink, F. C. MacKintosh, C. F. Schmidt, Laser trapping and laser interferometry for high-bandwidth micromechanical probing of biomaterials, Asia Optical Fiber Communication and Optoelectronic Exposition and Conference, AOE 2008 Asia Optical Fiber Communication and Optoelectronic Exposition and Conference, AOE 2008, 10.1364/aoe.2008.sap1, 2008, We present techniques based on optical trapping of micron-sized particles as probes and detecting their motion with sub-nanometer accuracy at 100 kHz bandwidth that can measure viscoelastic properties of biomaterials and cells on micrometer scales.. |
| 47. | Rommel G. Bacabac, Daisuke Mizuno, Christoph F. Schmidt, Fred C. MacKintosh, Jack J.W.A. Van Loon, Jenneke Klein-Nulend, Theo H. Smit, Round versus flat Bone cell morphology, elasticity, and mechanosensing, Journal of Biomechanics, 10.1016/j.jbiomech.2008.01.031, 41, 7, 1590-1598, 2008, There is increasing evidence that cell function and mechanical properties are closely related to morphology. However, most in vitro studies investigate flat adherent cells, which might not reflect physiological geometries in vivo. Osteocytes, the mechanosensors in bone, reside within ellipsoid containment, while osteoblasts adhere to flatter bone surfaces. It is unknown whether morphology difference, dictated by the geometry of attachment is important for cell rheology and mechanosensing. We developed a novel methodology for investigating the rheology and mechanosensitivity of bone cells under different morphologies using atomic force microscopy and our two-particle assay for optical tweezers. We found that the elastic constant of MLO-Y4 osteocytes when flat and adherent (>1 kPa) largely differed when round but partially adherent ( |
| 48. | Sara Jabbari-Farouji, Daisuke Mizuno, Maryam Atakhorrami, Fred C. MacKintosh, Christoph F. Schmidt, Erika Eiser, Gerard H. Wegdam, Daniel Bonn, Fluctuation-dissipation theorem in an aging colloidal glass, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.98.108302, 98, 10, 108302-108302, 2007.03, We provide a direct experimental test of the fluctuation-dissipation theorem (FDT) in an aging colloidal glass. The use of combined active and passive microrheology allows us to independently measure both the correlation and response functions in this nonequilibrium situation. Contrary to previous reports, we find no deviations from the FDT over several decades in frequency (1 Hz-10 kHz) and for all aging times. In addition, we find two distinct viscoelastic contributions in the aging glass, including a nearly elastic response at low frequencies that grows during aging.. |
| 49. | D. Mizuno, C. Tardin, C. F. Schmidt, and F. C. MacKintosh , Nonequilibrium mechanics of active cytoskeletal networks , Science, 10.1126/science.1134404 , 315 , 5810 , 370-373 , 2007.01. |
| 50. | Yasuyuki Kimura, Daisuke Mizuno, Microrheology of a swollen lyotropic lamellar phase, Molecular Crystals and Liquid Crystals, 10.1080/15421400701739170, 478, 1, 3/[759]-13/[769], 2007.01, Dynamics of nano-sized colloidal particles in a swollen lyotropic lamellar phase of a nonionic surfactant has been studied by three methods of microrheology. By electrophoretic microrheology (EPM), we find two relaxation processes respectively relating to the fluctuation of membranes and topological defects in lamellar structure. By direct tracking of particles under a microscope and manipulating them with an optical tweezers, we obtained detailed information on diffusion of a particle at low frequencies. We observed the jump-trap motion of a particle and the non-Newtonian rheological behavior at low frequencies.. |
| 51. | Daisuke Mizuno, Catherine Tardin, C. F. Schmidt, F. C. MacKintosh, Nonequilibrium mechanics of active cytoskeletal networks, SCIENCE, 10.1126/science.1134404, 315, 5810, 370-373, 2007.01, Cells both actively generate and sensitively react to forces through their mechanical framework, the cytoskeleton, which is a nonequilibrium composite material including polymers and motor proteins. We measured the dynamics and mechanical properties of a simple three-component model system consisting of myosin II, actin filaments, and cross-linkers. In this system, stresses arising from motor activity controlled the cytoskeletal network mechanics, increasing stiffness by a factor of nearly 100 and qualitatively changing the viscoelastic response of the network in an adenosine triphosphate-dependent manner. We present a quantitative theoretical model connecting the large-scale properties of this active gel to molecular force generation.. |
| 52. | Daisuke Mizuno, Catherine Tardin, Beth Percha, Frederick MacKintoshi, Christoph Schmidt, Non-equilibrium mechanics of in-vitro and in-vivo active cytoskeletal networks, BIOPHYSICAL JOURNAL, 315, 5810, 304A-304A, 2007.01, Cells both actively generate and sensitively react to forces through their mechanical framework, the cytoskeleton, which is a nonequilibrium composite material including polymers and motor proteins. We measured the dynamics and mechanical properties of a simple three-component model system consisting of myosin II, actin filaments, and cross-linkers. In this system, stresses arising from motor activity controlled the cytoskeletal network mechanics, increasing stiffness by a factor of nearly 100 and qualitatively changing the viscoelastic response of the network in an adenosine triphosphate-dependent manner. We present a quantitative theoretical model connecting the large-scale properties of this active gel to molecular force generation.. |
| 53. | Aviral Vatsa, Daisuke Mizuno, Theo H. Smit, Christoph F. Schmidt, Fred C. MacKintosh, Jenneke Klein-Nulend, Bio imaging of intracellular NO production in single bone cells after mechanical stimulation, JOURNAL OF BONE AND MINERAL RESEARCH, 10.1359/jbmr.060720, 21, 11, 1722-1728, 2006.11, We show the intracellular upregulation of NO production after mechanical stimulation, an essential chemical signal in bone remodeling. This is done in real time using the fluorescent chromophore DAR-4M AM. Differences in cellular response to mechanical stimulation of different regions of a single cell were observed.Introduction: Osteocytes are the most abundant bone cells that are believed to be the mechanosensors of bone, responding to mechanical stresses in interstitial fluid flow through the canaliculi. Under mechanical load, chemical signals such as NO play a key role in the activity of osteoblasts/osteoclasts that regulate bone remodeling. Despite the importance of NO in signaling, its real-time detection has proved challenging. This is largely because of the short NO half-life (typically similar to 0.1-5 s). Here, we show the upregulation of intracellular NO production in single osteocytes under localized mechanical stimulation.Materials and Methods: We used the chromophore DAR-4M AM for NO detection. This is loaded into surface-attached MLO-Y4 osteocyte-like and MC3T3-E1 osteoblast-like cells that are subjected to a localized mechanical stimulation using optical tweezers or a microneedle tip. DAR-4M AM is membrane-permeable and chelates NO, forming a stable, fluorescent compound, which is visible with a rhodamine filter.Results: Nonstimulated MLO-Y4 and MC3T3-E1 cells showed basal NO production levels, as indicated by a gradual increase in their fluorescence intensity. Localized mechanical stimulation of single MC3T3-E1 cells and MLO-Y4 cells by optical tweezers (150-550 pN, 0.5-3 Hz, 1 minute) showed a nearly 15-30% increase, whereas MLO-Y4 cells stimulated by a microneedle (10-20 nN, 1 minute) showed nearly 15-16% increase relative to their nonstimulated state. Furthermore, stimulation of a single cell process by a microneedle resulted in a 2-10% increase in the fluorescence intensity.Conclusions: NO is essential for mechanically induced bone remodeling and is a meaningful parameter for measuring bone cell activation after mechanical loading. Here we show NO upregulation in individual bone cells after a localized mechanical stimulation. We also show that both the cell body and the cell processes might be involved in mechanosensing. This technique allows characterization of the mechanosensitivity of different parts of a single osteocyte. This opens up the possibility to uncover the complexities and function of single osteocytes in the dynamic process of bone remodeling.. |
| 54. | Yasuyuki Kimura, Teppei Mori, Akira Yamamoto, Daisuke Mizuno, Hierarchical transport of nanoparticles in a lyotropic lamellar phase, Journal of Physics Condensed Matter, 10.1088/0953-8984/17/31/021, 17, 31, S2937-S2942, 2005.08, The dynamics of nanosized colloidal particles dispersed in a hyper-swollen lyotropic lamellar phase of a nonionic surfactant has been studied by ac electrophoretic light scattering and direct tracking of particles under a microscope. The frequency spectrum of electrophoretic mobility shows two relaxation processes. These are originated from the hindrance of free diffusion of particles by the interaction between membranes and particles. By direct tracking measurement, we find that particles jump from site to site where they stay for a long time. This trap-jump process greatly decreases the mobility at low frequencies.. |
| 55. | Yasuyuki Kimura, Teppei Mori, Akira Yamamoto, Daisuke Mizuno, Hierarchical dynamics of nano-particles in lyotropic lamellar phase, Molecular Crystals and Liquid Crystals, 10.1080/15421400590956324, 435, 51/[711]-61/[721], 2005, Dynamics of nano-sized colloidal particles dispersed in a dilute lyotropic lamellar phase of a nonionic surfactant has been studied experimentally by ac electrophoretic light scattering and direct tracking under a microscope. The obtained frequency spectrum of complex electrophoretic mobility shows two relaxation processes at about 1 kHz (HF relaxation) and a few Hz (LF relaxation). These relaxations are due to the hindrance of free diffusion of particles by the hierarchical local static and dynamical structures of lamellar phase. From the direct tracking of fluorescent-labeled particles under a microscope, we find that particles show jump from sites to sites where they stay for a long time. This trap-jump process extremely decreases their mobility at low frequencies.. |
| 56. | Daisuke Mizuno, Yasuyuki Kimura, Reinosuke Hayakawa, Electrophoretic microrheology of a dilute lamellar phase: relaxation mechanisms in frequency-dependent mobility of nanometer-sized particles between soft membranes., Physical review. E, Statistical, nonlinear, and soft matter physics, 70, 1 Pt 1, 011509-011509, 2004.07, Viscoelastic properties of complex fluids in the microscopic scale can be studied by measuring the transport properties of small, embedded probe particles. We have measured the complex electrophoretic mobility micro*(omega) of nanometer-sized particles dispersed in a lyotropic lamellar phase, which shows two relaxation processes at approximately 1 kHz (high frequency relaxation, HF) and 1 Hz (low frequency relaxation, LF). It is shown quantitatively that these processes are caused by the trapping of particles within two local structures of characteristic size in the lamellar phase: the interbilayer distance and the persistence length. The origin of observed relaxations is further investigated and augmented in this study with data obtained by two other complementary methods, dielectric spectroscopy and the direct observation of fluorescently labelled probe particles under an optical microscope. It is shown that the local distortion field of the lamellar phase is induced by the extra steric interaction involving the collision of a colloidal particle with the membrane. The resulting distortion field hinders the Brownian motion of colloidal particles parallel to the membranes (not vertical), and causes the observed HF relaxation. On the other hand, the origin of LF relaxation is presumably a result of the defects in the lamellar structure. Since the results of this study show that the transport property is strongly influenced by microscopic environments, this method is referred to as electrophoretic microrheology.. |
| 57. | Daisuke Mizuno, Yasuyuki Kimura, Reinosuke Hayakawa, Electrophoretic microrheology of a dilute lamellar phase Relaxation mechanisms in frequency-dependent mobility of nanometer-sized particles between soft membranes, Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 10.1103/PhysRevE.70.011509, 70, 1, 2004.01, Viscoelastic properties of complex fluids in the microscopic scale can be studied by measuring the transport properties of small, embedded probe particles. We have measured the complex electrophoretic mobility [Formula presented] of nanometer-sized particles dispersed in a lyotropic lamellar phase, which shows two relaxation processes at approximately [Formula presented] (high frequency relaxation, HF) and [Formula presented] (low frequency relaxation, LF). It is shown quantitatively that these processes are caused by the trapping of particles within two local structures of characteristic size in the lamellar phase: the interbilayer distance and the persistence length. The origin of observed relaxations is further investigated and augmented in this study with data obtained by two other complementary methods, dielectric spectroscopy and the direct observation of fluorescently labelled probe particles under an optical microscope. It is shown that the local distortion field of the lamellar phase is induced by the extra steric interaction involving the collision of a colloidal particle with the membrane. The resulting distortion field hinders the Brownian motion of colloidal particles parallel to the membranes (not vertical), and causes the observed HF relaxation. On the other hand, the origin of LF relaxation is presumably a result of the defects in the lamellar structure. Since the results of this study show that the transport property is strongly influenced by microscopic environments, this method is referred to as electrophoretic microrheology.. |
| 58. | Daisuke Mizuno, Takuji Nishino, Yasuyuki Kimura, Reinosuke Hayakawa, Dielectric response in dilute lyotropic lamellar and sponge phases of a nonionic surfactant, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 67, 6 1, 2003.06, The dielectric response in lyotropic lamellar and sponge phases made up of a nonionic surfactant and water was measured. A Maxwell-Wagner relaxation influenced by the charge accumulation at the interface between membrane and water was observed. Overall, results give some basic information for understanding the dynamic electrical properties of other complex systems composed of lipid membranes.. |
| 59. | Daisuke Mizuno, Takuji Nishino, Yasuyuki Kimura, Reinosuke Hayakawa, Dielectric response in dilute lyotropic lamellar and sponge phases of a nonionic surfactant., Physical review. E, Statistical, nonlinear, and soft matter physics, 67, 6 Pt 1, 061505-061505, 2003.06, We study the dielectric response in lyotropic lamellar and sponge phases made up of a binary mixture of a nonionic surfactant and water. A single relaxation is observed in both phases within the measured frequency range of 10-10(7) Hz. This relaxation originates from the obstruction of electric current by insulating membranes. In the sponge phase, it depends on surfactant concentration and conductivity of solvent. The observed dependence is well-described quantitatively by the equivalent electric circuit of the sponge structure, including the effect of accumulation of ions at the interface between water and membrane. In the lamellar phase, there is little dependence of dielectric relaxation on surfactant concentration. This is presumably due to the fact that submicrometer-sized defects play a more important role in the electrical property in this phase than the lamellar structure in smaller length scales does. Our results offer some basic information to study more complicated systems composed of charged membranes in aqueous solution.. |
| 60. | Mizuno, D (Mizuno, D); Kimura, Y (Kimura, Y); Hayakawa, R (Hayakawa, R), Wide-band spectroscopy of dynamic electrophoretic mobility and its application to microrheology., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 225, U631-U631, 2003.03. |
| 61. | Daisuke Mizuno, Takuji Nishino, Yasuyuki Kimura, Reinosuke Hayakawa, Dielectric response in dilute lyotropic lamellar and sponge phases of a nonionic surfactant, Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 10.1103/PhysRevE.67.061505, 67, 6, 2003.01, We study the dielectric response in lyotropic lamellar and sponge phases made up of a binary mixture of a nonionic surfactant and water. A single relaxation is observed in both phases within the measured frequency range of [Formula presented] This relaxation originates from the obstruction of electric current by insulating membranes. In the sponge phase, it depends on surfactant concentration and conductivity of solvent. The observed dependence is well-described quantitatively by the equivalent electric circuit of the sponge structure, including the effect of accumulation of ions at the interface between water and membrane. In the lamellar phase, there is little dependence of dielectric relaxation on surfactant concentration. This is presumably due to the fact that submicrometer-sized defects play a more important role in the electrical property in this phase than the lamellar structure in smaller length scales does. Our results offer some basic information to study more complicated systems composed of charged membranes in aqueous solution.. |
| 62. | Daisuke Mizuno, Yasuyuki Kimura, Reinosuke Hayakawa, Electrophoretic microrheology in a dilute lamellar phase of a nonionic surfactant, Physical Review Letters, 10.1103/PhysRevLett.87.088104, 87, 8, 88104-1-88104-4, 2001.08, We measured the complex electrophoretic mobility μ*(ω) of nanometer-sized particles dispersed in a lyotropic lamellar phase, and observed two relaxation processes corresponding to the two characteristic lengths of lamellar structure. Faster relaxation is caused by the distortion field of lamellar phase induced by the colloidal particles, and slower relaxation is presumably due to the defects in lamellar structure. Since the dynamic transport property is strongly influenced by the microscopic circumstances as shown in this paper, this method is referred to as electrophoretic microrheology.. |
| 63. | Mizuno, D (Mizuno, D); Hattori, K (Hattori, K); Sakai, K (Sakai, K); Takagi, K (Takagi, K), Dynamic measurement of surface properties with Ripplon spectroscopy, 1998 IEEE ULTRASONICS SYMPOSIUM - PROCEEDINGS, VOLS 1 AND 2, 1121-1124. |
Unauthorized reprint of the contents of this database is prohibited.