Abstract:
:We measured the viscoelastic properties of the cytoplasm of J774 macrophages with a recently developed microrheometer. Ferromagnetic beads (1.3 microm in diameter) were used to determine the local viscoelastic moduli. Step-force pulses were applied to the magnetic beads and the displacement was observed by single particle tracking. By analyzing the creep response curves in terms of a triphasic mechanical equivalent circuit, we measured the shear elastic modulus, the effective viscosities, and the strain relaxation time. The values of the shear modulus vary by more than an order of magnitude within the cell population (range, 20-735 Pa; average, 343 Pa) and by a factor of 2 within single cells. The effective viscosity of the cytoplasm exhibits a relatively sharp distribution about an average of eta = 210 Pa s (+/- 143 Pa s). We measured the displacement field generated by the local forces by observing the induced motion of nonmagnetic beads. Even at distances of the order of 1 microm, no induced motion was seen, suggesting that the cytoplasm is composed of clusters of densely packed and cross-linked filaments separated by soft regions. In another series of experiments we analyzed the magnetophoretic motion of the ferromagnetic beads at a constant magnetic force. Measuring the bead velocity parallel and perpendicular to the applied force showed that local active forces on the beads varied from 50 to 900 pN.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Bausch AR,Möller W,Sackmann Edoi
10.1016/S0006-3495(99)77225-5subject
Has Abstractpub_date
1999-01-01 00:00:00pages
573-9issue
1 Pt 1eissn
0006-3495issn
1542-0086pii
S0006-3495(99)77225-5journal_volume
76pub_type
杂志文章abstract::Stearoylsphingomyelin (SSM) bilayers containing 0, 22, and 50 mol % cholesterol (Chol) and a pentadecanoyl-stearoylphosphatidylcholine (15SPC) bilayer containing 22 mol % Chol were molecular dynamics simulated at two temperatures (37 degrees C and 60 degrees C). 15SPC is the best PC equivalent of SSM. The Chol effect ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.106.080887
更新日期:2006-11-15 00:00:00
abstract::A recent thermodynamic model describes a reversible reaction between cholesterol (C) and phospholipid (P) to form a condensed complex C(nq)P(np). Here q and p are relatively prime integers used to define the stoichiometric composition, and n is a measure of cooperativity. The present study applies this model to the sc...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(01)75920-6
更新日期:2001-11-01 00:00:00
abstract::The classical cable equation, in which membrane conductance is considered constant, is modified by including the linearized effect of membrane potential on sodium and potassium ionic currents, as formulated in the Hodgkin-Huxley equations for the squid giant axon. The resulting partial differential equation is solved ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(69)86446-5
更新日期:1969-10-01 00:00:00
abstract::Migratory cells are known to adapt to environments that contain wide-ranging levels of chemoattractant. Although biochemical models of adaptation have been previously proposed, here, we discuss a different mechanism based on mechanosensing, in which the interaction between biochemical signaling and cell tension facili...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2020.08.035
更新日期:2020-10-20 00:00:00
abstract::The sequence of events involved in the transition from attached liposomes to bilayer patches on hydrophilic and hydrophobic solid supports were visualized in situ by Tapping Mode atomic force microscopy in liquid. In a smooth manner, the attached liposomes spread and flattened from the outer edges toward the center un...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(00)76549-0
更新日期:2000-12-01 00:00:00
abstract::Histograms of single-molecule Förster resonance energy transfer (FRET) efficiency are often used to study the structures of biomolecules and relate these structures to function. Methods like probability distribution analysis analyze FRET histograms to detect heterogeneities in molecular structure, but they cannot dete...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2011.01.066
更新日期:2011-03-16 00:00:00
abstract::Many essential processes in eukaryotic cells depend on regulated molecular exchange between its two major compartments, the cytoplasm and the nucleus. In general, nuclear import of macromolecular complexes is dependent on specific peptide signals and their recognition by receptors that mediate translocation through th...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.105.060160
更新日期:2005-09-01 00:00:00
abstract::Nitrile hydratase (NHase) is an enzyme used in the industrial biotechnological production of acrylamide. The active site, which contains nonheme iron or noncorrin cobalt, is buried in the protein core at the interface of two domains, alpha and beta. Hydrogen bonds between betaArg-56 and alphaCys-114 sulfenic acid (alp...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.107.116665
更新日期:2008-05-15 00:00:00
abstract::Experiments have shown that the ability of the HIV-1 virus to infect cells can be greatly diminished by deactivation of the N-terminal (fusion) peptide of its glycoprotein gp41. Deactivation can be achieved by the deletion of several amino acid residues, or replacement of a hydrophobic residue with a polar residue, to...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(02)75313-7
更新日期:2002-12-01 00:00:00
abstract::Synchrotron x-ray scattering measurements were performed on dilute solutions of the purified hemocyanin subunit (Bsin1) from scorpion (Buthus sindicus) and the N-terminal functional unit (Rta) from a marine snail (Rapana thomasiana). The model-independent approach based on spherical harmonics was applied to calculate ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/s0006-3495(00)76655-0
更新日期:2000-02-01 00:00:00
abstract::Zebrafish (Danio rerio) swim within days of fertilization, powered by muscles of the axial myotomes. Forces generated by these muscles can be measured rapidly in whole, intact larval tails by adapting protocols developed for ex vivo muscle mechanics. But it is not known how well these measurements reflect the function...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2020.06.036
更新日期:2020-08-18 00:00:00
abstract::The dependence of the fluorescence of catalase upon the concentration of added superoxide dismutase (SOD) indicates that SOD binds to saturable sites on catalase. The affinity of SOD for these sites varies with temperature, and with the concentration of each of three nominally inert polymeric additives--dextran 70, Fi...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2010.05.013
更新日期:2010-08-04 00:00:00
abstract::Describing and understanding the biological function of a protein requires a detailed structural and thermodynamic description of the protein's native state ensemble. Obtaining such a description often involves characterizing equilibrium fluctuations that occur beyond the nanosecond timescale. Capturing such fluctuati...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.106.094409
更新日期:2007-03-01 00:00:00
abstract::The diffusion of beta-enolase and creatine phosphokinase in muscle cells has been studied by modulated fringe pattern photobleaching. Beta-enolase is mobile in the sarcoplasm. At 20 degrees C, the diffusion coefficient is 13.5 +/- 2.5 microm2 s(-1) in the cytosol and 56 microm2 s(-1) in aqueous media. As in the case o...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(97)78295-X
更新日期:1997-11-01 00:00:00
abstract::Ubiquinol cytochrome c oxidoreductase (bc1 complex) serves as an important electron junction in many respiratory systems. It funnels electrons coming from NADH and ubiquinol to cytochrome c, but it is also capable of producing significant amounts of the free radical superoxide. In situ and in other experimental system...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2017.08.018
更新日期:2017-10-03 00:00:00
abstract::The nuclear magnetic resonance (NMR) of water protons in live and glycerinated muscle, suspensions of glycerinated myofibrils, and solutions of several muscle proteins has been studied. T(1) and T(2), measured on partially hydrated proteins by pulsed spin-echo techniques, decreased as the ratio of water to protein dec...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(71)86274-4
更新日期:1971-12-01 00:00:00
abstract::Equatorial x-ray diffraction patterns were obtained from single skinned rabbit psoas fibers during various degrees of activation under isometric conditions at ionic strength 170 mM and 6-9 degrees C. By direct calcium activation, contraction was homogeneous throughout the preparation, and by using a cycling technique ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(85)83841-8
更新日期:1985-11-01 00:00:00
abstract::DNA beacons are short single-stranded chains which can form closed hairpin shapes through complementary base pairing at their ends. Contrary to the common polymer theory assumption that only their loop length matters, experiments show that their closing kinetics depend on the loop composition. We have modeled the clos...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(03)70045-9
更新日期:2003-05-01 00:00:00
abstract::The interplay between epigenetic modification and chromatin compaction is implicated in the regulation of gene expression, and it comprises one of the most fascinating frontiers in cell biology. Although a complete picture is still lacking, it is generally accepted that the differentiation of embryonic stem (ES) cells...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2012.10.015
更新日期:2012-11-21 00:00:00
abstract::Stabilization of the lipid bilayer membrane in red blood cells by its association with an underlying membrane-associated cytoskeleton has long been recognized as critical for proper red blood cell function. One of the principal connections between skeleton and bilayer is via linkages between band 3, the integral membr...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.108.129163
更新日期:2008-08-01 00:00:00
abstract::DNA release from lipoplexes is an essential step during lipofection and is probably a result of charge neutralization by cellular anionic lipids. As a model system to test this possibility, fluorescence resonance energy transfer between DNA and lipid covalently labeled with Cy3 and BODIPY, respectively, was used to mo...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.104.042895
更新日期:2004-08-01 00:00:00
abstract::Bacteriorhodopsin proteoliposomes were used as a model system to explore the applicability of micromechanical cantilever arrays to detect conformational changes in membrane protein patches. The three main results of our study concern: 1), reliable functionalization of micromechanical cantilever arrays with proteolipos...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.105.072934
更新日期:2006-04-15 00:00:00
abstract::Previously, we discussed the calculation of the dipole moments of small proteins using the three-dimensional protein data-base. Our results demonstrate that the calculated dipole moments are in acceptable agreement with measured values. We, however, noted the difficulty of the calculation with larger proteins, in part...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(93)81524-8
更新日期:1993-05-01 00:00:00
abstract::Knowledge about the influenza fusion peptide (FP) membrane insertion mode is crucial for understanding its fusogenic mechanism. NMR and electron paramagnetic resonance experiments showed that in micelles, the FP inserted as a fixed-angle inverted V. In membranes, however, it was shown to insert as a straight α-helix (...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2012.04.003
更新日期:2012-05-16 00:00:00
abstract::Transcription factors use both protein-DNA and protein-protein interactions to assemble appropriate complexes to regulate gene expression. Although most transcription factors operate as monomers or dimers, a few, including the E26 transformation-specific family repressors Drosophila melanogaster Yan and its human homo...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2016.11.901
更新日期:2017-01-10 00:00:00
abstract::We have studied the photoinduced volume changes, energetics, and kinetics in the early steps of the bacteriorhodopsin (BR) photocycle with pulsed, time-resolved photoacoustics. Our data show that there are two volume changes. The fast volume change ( < or = 200 ns) is an expansion (2.5 +/- 0.3 A3/molecule) and is obse...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(96)79235-4
更新日期:1996-07-01 00:00:00
abstract::Iberiotoxin, a toxin purified from the scorpion Buthus tamulus is a 37 amino acid peptide having 68% homology with charybdotoxin. Charybdotoxin blocks large conductance Ca(2+)-activated K+ channels at nanomolar concentrations from the external side only (Miller, C., E. Moczydlowski, R. Latorre, and M. Phillips. 1985. ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(92)81630-2
更新日期:1992-08-01 00:00:00
abstract::We manipulate lipid bilayer surface charge and gauge its influence on gramicidin A channel conductance by two strategies: titration of the lipid charge through bulk solution pH and dilution of a charged lipid by neutral. Using diphytanoyl phosphatidylserine (PS) bilayers with CsCl aqueous solutions, we show that the e...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(98)77620-9
更新日期:1998-10-01 00:00:00
abstract::We introduce dual-color time-integrated fluorescence cumulant analysis (TIFCA) to analyze fluorescence fluctuation spectroscopy data. Dual-color TIFCA utilizes the bivariate cumulants of the integrated fluorescent intensity from two detection channels to extract the brightness in each channel, the occupation number, a...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.106.086181
更新日期:2006-10-01 00:00:00
abstract::The shapes of fluorescence induction curves in spinach chloroplasts, measured using double-flash pump-probe techniques, are shown to depend on the duration of the actinic flashes. For flash durations tau(0) = 2 mus, the variable fluorescence F(nu) grows exponentially (or nearly so) with increasing fluence J of the a...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(91)82233-0
更新日期:1991-02-01 00:00:00