Abstract:
:Two-dimensional solid-state 31P NMR has been used to investigate the orientational exchange of phospholipids in gel and liquid-crystalline aqueous multilamellar dispersions and oriented multibilayers, and in biological membranes. In liquid-crystalline L alpha multilamellar dispersions, orientational exchange originates from the lateral diffusion of phospholipid molecules over the curved surface of the liposomes and is manifest by an increase in off-diagonal intensity, which correlates the 90 and 0 degrees orientations of the membrane normal with respect to the magnetic field when the system is fully exchanged. Spectral simulations of the time evolution of exchange allowed determination of the correlation times tau d for lateral diffusion. For DMPC and DPPC at comparable reduced temperatures, tau d values of 44 and 8 ms were obtained, respectively. The nature and rate of exchange observed for POPE at 30 degrees C is similar to that of DMPC at the same temperature. The measured correlation times are consistent with diffusion rates obtained by FRAP for liposomes with radii in the 1 micron range. In the gel phase of DPPC (30 degrees C), little orientational exchange is observed at mixing times up to 200 ms, demonstrating that the lateral diffusion is very slow. The correlation time for orientational exchange obtained from spectral simulations was approximately 900 ms; thus, exchange in the gel state is at least two orders of magnitude slower than in the liquid-crystalline state. In the P beta (ripple) phase, at temperatures between 34 and 39 degrees C, significant exchange is observed for mixing times between 50 and 200 ms. Exchange is also observed in oriented samples of DPPC in the P beta phase for mixing times of 50 ms, but not for oriented liquid-crystalline samples for mixing times up to 100 ms. The exchange observed in the ripple phase could originate from rapid lateral diffusion of "fast" diffusing phospholipid within defect structures, and/or from "slow" lateral diffusion of ordered phospholipid over the ripples. 2D experiments were also performed on pig erythrocyte ghosts and on intact pig spinal cord. Significant orientational exchange was observed with the erythrocyte ghosts at a mixing time of 200 ms, but almost no exchange was observed with the spinal cord at the same mixing time. Spectral simulations suggest tau d values of approximately 400 ms and 1.3 s for the erythrocyte ghosts and spinal cord at 30 degrees C. The results demonstrate that exchange in the biological membranes is significantly slower than in the model membrane systems, which suggests that the cell surfaces are relatively "smooth," i.e., any local surface perturbations are either present in small number or have little effect on the mean orientation of the phospholipids with respect to the membrane normal.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Fenske DB,Jarrell HCdoi
10.1016/S0006-3495(91)82198-1subject
Has Abstractpub_date
1991-01-01 00:00:00pages
55-69issue
1eissn
0006-3495issn
1542-0086pii
S0006-3495(91)82198-1journal_volume
59pub_type
杂志文章abstract::We present a theoretical analysis of intracellular calcium waves propagated by calcium feedback at the inositol 1,4,5-trisphosphate (IP3) receptor. The model includes essential features of calcium excitability, but is still analytically tractable. Formulas are derived for the wave speed, amplitude, and width. The calc...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(97)78888-X
更新日期:1997-06-01 00:00:00
abstract::We are interested in modeling the membrane-spanning domain of the serotonin 5-HT1A G-protein coupled receptor. This superfamily of proteins is predicted to share the topology of the seven transmembrane helices of bacteriorhodopsin (BR), even though no significant sequence homology had been identified. We found signifi...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(92)81794-0
更新日期:1992-04-01 00:00:00
abstract::In this work, we present experimental data, supported by a quantitative model, on the generation and effect of potential gradients across a tethered bilayer lipid membrane (tBLM) with, to the best of our knowledge, novel architecture. A challenge to generating potential gradients across tBLMs arises from the tethering...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2013.11.1121
更新日期:2014-01-07 00:00:00
abstract::Catch bonds are characterized by average lifetimes that initially increase with increasing tensile force. Recently, they have been implicated in T cell activation, where small numbers of antigenic receptor-ligand bonds at a cell-cell interface can stimulate a T cell. Here, we use computational methods to investigate s...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2017.05.023
更新日期:2017-07-11 00:00:00
abstract::The motility of Amoeba proteus was examined using the technique of passive particle tracking microrheology, with the aid of newly developed particle tracking software, a fast digital camera, and an optical microscope. We tracked large numbers of endogeneous particles in the amoebae, which displayed subdiffusive motion...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.107.123851
更新日期:2008-04-15 00:00:00
abstract::Observation of cell membrane buckling and cell folding in micropipette aspiration experiments was used to evaluate the bending rigidity of the red blood cell membrane. The suction pressure required to buckle the membrane surface initially was found to be about one-half to two-thirds of the pressure that caused the cel...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(83)84319-7
更新日期:1983-07-01 00:00:00
abstract::A recent theory for the long time dynamics of flexible chain molecules is applied for the first time to a peptide of biological importance, the neurotransmitter met-enkephalin. The dynamics of met-enkephalin is considerably more complicated than that of the previously studied glycine oligomers; met-enkephalin contains...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(99)77185-7
更新日期:1999-01-01 00:00:00
abstract::A detailed treatment is provided of the various free-energy terms that contribute to the transfer of a polyalanine alpha-helix from the aqueous phase into lipid bilayers. In agreement with previous work, the hydrophobic effect is found to provide the major driving force for helix insertion. However, an opposing effect...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(96)79744-8
更新日期:1996-04-01 00:00:00
abstract::It has been repeatedly noted that the change of conformation of the molecules that serve as the ion-selective channels for sodium and potassium conductance in the nerve membrane will be accompanied by a change in the dipole moment of the molecule. This time-dependent change of dipole moment will produce transient curr...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(77)85587-2
更新日期:1977-09-01 00:00:00
abstract::To give a realistic representation of the pulse propagation in arteries a theoretical analysis of the wave propagation through a viscous incompressible fluid contained in an initially stressed elastic tube is considered. The tube is assumed to be orthotropic and its longitudinal motion is constrained by a uniformly di...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/s0006-3495(68)86512-9
更新日期:1968-05-01 00:00:00
abstract::Intrinsically disordered proteins play important roles throughout biology, yet our understanding of the relationship between their sequences, structural properties, and functions remains incomplete. The dynamic nature of these proteins, however, makes them difficult to characterize structurally. Many disordered protei...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2017.06.042
更新日期:2017-08-08 00:00:00
abstract::Why is the spine of a neuron so small that it can contain only small numbers of molecules and reactions inevitably become stochastic? We previously showed that, despite such noisy conditions, the spine exhibits robust, sensitive, and efficient features of information transfer using the probability of Ca2+ increase; ho...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2016.12.043
更新日期:2017-02-28 00:00:00
abstract::The functional diversity of gap junction intercellular channels arising from the large number of connexin isoforms is significantly increased by heterotypic interactions between members of this family. This is particularly evident in the rectifying behavior of Cx26/Cx32 heterotypic channels (. Proc. Natl. Acad. Sci. U...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(99)77129-8
更新日期:1999-12-01 00:00:00
abstract::Galactose and other chemotactic attractants have been shown to trigger an apparent hyperpolarization in Escherichia coli (Eisenbach, M., 1982, Biochemistry, 21:6818-6825). The probe used to measure membrane potential in that study, tetraphenylphosphonium (TPP+), may respond also to surface-charge changes in the membra...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(84)84169-7
更新日期:1984-02-01 00:00:00
abstract::Ca2+ release from the endoplasmic reticulum (ER) contributes to Ca2+ transients in frog sympathetic ganglion neurons. Here we use video-rate confocal fluo-4 fluorescence imaging to show that single action potentials reproducibly trigger rapidly rising Ca2+ transients at 1-3 local hot spots within the peripheral ER-ric...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(04)74094-1
更新日期:2004-01-01 00:00:00
abstract::Single-molecule epifluorescence microscopy was used to observe the translational motion of GPI-linked and native I-E(k) class II MHC membrane proteins in the plasma membrane of CHO cells. The purpose of the study was to look for deviations from Brownian diffusion that might arise from barriers to this motion. Detergen...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(02)75277-6
更新日期:2002-11-01 00:00:00
abstract::A new approach to the calculation of bimolecular association constants for partially diffusion-limited reactions between asymmetric species (e.g. the ligand binding site of a macromolecule covers only a portion of its surface) is presented. The usual formulation, which is almost always analytically intractable, is bas...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(81)84759-5
更新日期:1981-12-01 00:00:00
abstract::Although both RNA and proteins have densely packed native structures, chain organizations of these two biopolymers are fundamentally different. Motivated by the recent discoveries in chromatin folding that interphase chromosomes have territorial organization with signatures pointing to metastability, we analyzed the b...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2016.04.020
更新日期:2016-06-07 00:00:00
abstract::We derive the statistics of the signals generated by shape fluctuations of large molecules studied by feedback tracking microscopy. We account for the influence of intramolecular dynamics on the response of the tracking system and derive a general expression for the fluorescence autocorrelation function that applies w...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2010.03.045
更新日期:2010-07-07 00:00:00
abstract::The binding constants, K(1) and K(2), and the number of Ca(2+) ions in each of the two high affinity sites of Ca(2+)-regenerated bacteriorhodopsin (bR) are determined potentiometrically at different pH values in the range of pH 3.5-4.5 by using the Scatchard plot method. From the pH dependence of K(1) and K(2), it was...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(92)81929-X
更新日期:1992-05-01 00:00:00
abstract::Open channel properties of canine cardiac Purkinje cell Na+ channels were studied with single channel cell-attached recording and with whole cell macroscopic current recording in internally perfused cells. Single channel currents and membrane currents increased with an increase in Na+ concentration, but showed evidenc...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(87)83183-1
更新日期:1987-07-01 00:00:00
abstract::Calmodulin (CaM) is a highly flexible calcium-binding protein that mediates signal transduction through an ability to differentially bind to highly variable binding sequences in target proteins. To identify how binding affects CaM motions, and its relationship to conformational entropy and target peptide sequence, we ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2012.08.037
更新日期:2012-10-03 00:00:00
abstract::We have studied the large increase in macroscopic potassium channel current caused by catecholamines in mammalian cardiac cells. An increase in macroscopic K current could result from either an increase in the single-channel current or by an increase in the number of channels that are open. Therefore, we have measured...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(89)82872-3
更新日期:1989-04-01 00:00:00
abstract::Although actin and myosin are important contributors to cell-force generation, shape change, and motility, their contributions to cell stiffness and frequency-dependent rheology have not been conclusively determined. We apply several pharmacological interventions to cultured epithelial cells to elucidate the roles of ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.106.091264
更新日期:2006-11-15 00:00:00
abstract::The mechanisms that limit the speed at which striated muscles relax are poorly understood. This work presents, to our knowledge, novel simulations that show that the time course of relaxation is accelerated by interfilamentary movement resulting from series compliance; force drops faster when myosin heads move relativ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2015.12.024
更新日期:2016-02-02 00:00:00
abstract::Dendrites of cerebellar Purkinje cells (PCs) respond to brief excitations from parallel fibers with lasting plateau depolarizations. It is unknown whether these plateaus are local events that boost the synaptic signals or they propagate to the soma and directly take part in setting the cell firing dynamics. To address...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2010.04.056
更新日期:2010-07-21 00:00:00
abstract::The time dependence of magnetic field effects on light absorption by triplet-state and radical ions in quinone-depleted reaction centers of Rhodopseudomonas sphaeroides strain R-26 has been investigated. Measurements on the time scale of the hyperfine interaction in the radical pair [(BChl)2+. ...BPh-.)] provided kine...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(82)84494-9
更新日期:1982-07-01 00:00:00
abstract::A fundamental question concerning the ClC Cl-/H+ antiporters is the nature of their proton transport (PT) pathway. We addressed this issue by using a novel computational methodology capable of describing the explicit PT dynamics in the ClC-ec1 protein. The main result is that the Glu203 residue delivers a proton from ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2009.04.038
更新日期:2009-07-08 00:00:00
abstract::We have examined the morphology and osmotic properties of large unilamellar vesicles (LUVs) prepared by extrusion. Contrary to expectations, we observe by cryo-electron microscopy that such vesicles, under isoosmotic conditions, are non-spherical. This morphology appears to be a consequence of vesicle passage through ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(93)81385-7
更新日期:1993-02-01 00:00:00
abstract::A delay ( approximately 10 min) in the appearance of intracellular phage is caused by preincubating the infecting phage T4o(1) in proflavine, acridine orange, or ethidium, but not polyamines. No significant delay in attachment is observed. Apparently the presence of the dye is required inside the permeability barrier ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(72)86144-7
更新日期:1972-08-01 00:00:00