Abstract:
:Beat-to-beat alternation of the action potential duration (APD) in paced cardiac cells has been linked to the onset of lethal arrhythmias. Both experimental and theoretical studies have shown that alternans at the single cell level can be caused by unstable membrane voltage (V(m)) dynamics linked to steep APD-restitution, or unstable intracellular calcium (Ca) cycling linked to high sensitivity of Ca release from the sarcoplasmic reticulum on sarcoplasmic reticulum Ca load. Identifying which of these two mechanisms is the primary cause of cellular alternans, however, has remained difficult since Ca and V(m) are bidirectionally coupled. Here, we use numerical simulations of a physiologically detailed ionic model to show that the origin of alternans can be inferred by measuring the length scales over which APD and Ca(i) alternans reverse phase during spatially discordant alternans. The main conclusion is that these scales are comparable to a few millimeters and equal when alternans is driven by APD restitution, but differ markedly when alternans is driven predominantly by unstable Ca cycling. In the latter case, APD alternans still reverses phase on a millimeter tissue scale due to electrotonic coupling, while Ca alternans reverses phase on a submillimeter cellular scale. These results show that experimentally accessible measurements of Ca(i) and V(m) in cardiac tissue can be used to shed light on the cellular origin of alternans.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Sato D,Shiferaw Y,Qu Z,Garfinkel A,Weiss JN,Karma Adoi
10.1529/biophysj.106.100982subject
Has Abstractpub_date
2007-02-15 00:00:00pages
L33-5issue
4eissn
0006-3495issn
1542-0086pii
S0006-3495(07)70920-7journal_volume
92pub_type
杂志文章abstract::Many cell cytoskeletons include an aster of microtubules, with the centrosome serving as the focal point. The position of the centrosome within the cell is important in such directional activities as wound closure and interactions of immune cells. Here we analyzed the centrosome positioning as it is dictated by microt...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2010.09.017
更新日期:2010-11-03 00:00:00
abstract::A theoretical framework is developed to study the dynamics of protein folding. The key insight is that the search for the native protein conformation is influenced by the rate r at which external parameters, such as temperature, chemical denaturant, or pH, are adjusted to induce folding. A theory based on this insight...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.108.133132
更新日期:2008-09-15 00:00:00
abstract::A simple method of generating electric field-induced concentration gradients in planar supported bilayers has been developed. Gradients of charged, fluorescently labeled probes were visualized by epifluorescence microscopy and could be observed at field strengths as low as 1 V/cm. Steady-state concentration gradients ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(95)80067-6
更新日期:1995-11-01 00:00:00
abstract::Lipid droplets (LDs) are cytosolic organelles that protrude from the endoplasmic reticulum membrane under energy-rich conditions. How an LD buds off from the endoplasmic reticulum bilayer is still elusive. By using a continuous media description, we computed the morphology of a lipid droplet embedded in between two id...
journal_title:Biophysical journal
pub_type: 信件
doi:10.1016/j.bpj.2017.05.045
更新日期:2017-07-11 00:00:00
abstract::The investigation of the mechanism of protein folding is complicated by the context dependence of the rates of intramolecular contact formation. Methods based on site-specific labeling and ultrafast spectroscopic detection of fluorescence signals were developed for monitoring the rates of individual subdomain folding ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2017.01.037
更新日期:2017-05-09 00:00:00
abstract::Direct spectroscopic measurements of rotational motions of proteins and large protein segments are crucial to understanding the molecular dynamics of protein function. Fluorescent probes and spin labels attached to proteins have proved to be powerful tools in the study of large-scale protein motions. Fluorescence depo...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(78)85394-6
更新日期:1978-11-01 00:00:00
abstract::The partition coefficients (K(P)) of a series of single-chain and double-chain fluorescent amphiphiles, between solid ordered (P(beta') and L(beta)) and liquid disordered (L(alpha) of the type l(d)) lipid phases coexisting in the same lipid bilayer, was studied using steady-state fluorescence emission anisotropy. The ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(00)76840-8
更新日期:2000-06-01 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::We have used chemical synthesis, electron paramagnetic resonance (EPR), and circular dichroism to detect and analyze the structural dynamics of a ryanodine receptor (RyR) peptide bound to calmodulin (CaM). The skeletal muscle calcium release channel RyR1 is activated by Ca2+-free CaM and inhibited by Ca2+-bound CaM. T...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2016.10.025
更新日期:2016-12-06 00:00:00
abstract::In permeabilized single fibers of fast (psoas) and slow (soleus) muscle from the rabbit, the effect of pH on isometric myofibrillar ATPase activity and force was studied at 15 degrees C, in the pH range 6.4-7.9. ATPase activity was measured photometrically by enzymatic coupling of the regeneration of ATP to the oxidat...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(94)80727-1
更新日期:1994-12-01 00:00:00
abstract::We present a method for calculating the configurational-dependent diffusion coefficient of a globular protein as a function of the global folding process. Using a coarse-grained structure-based model, we determined the diffusion coefficient, in reaction coordinate space, as a function of the fraction of native contact...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2010.04.041
更新日期:2010-07-21 00:00:00
abstract::Myoglobin (Mb) is a model system for ligand binding and migration. The energy barriers (ΔG) for ligand migration in Mb have been studied in the past by experiment and theory and significant differences between different approaches were found. From experiment, it is known that Mb can assume a large number of conformati...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2011.10.058
更新日期:2012-01-18 00:00:00
abstract::This article describes the application of a change-point algorithm to the analysis of stochastic signals in biological systems whose underlying state dynamics consist of transitions between discrete states. Applications of this analysis include molecular-motor stepping, fluorophore bleaching, electrophysiology, partic...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2015.05.038
更新日期:2015-07-21 00:00:00
abstract::The effect of aggregation of gramicidin A' (GA) on the phase structure of dipalmitoylphosphatidylcholine (DPPC) multilamellar vesicles was studied by cw-ESR using a chain-labeled lipid (16PC) at temperatures between 30 degrees and 45 degreesC that span the main phase transition of DPPC. Boundary lipids were observed o...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(99)77195-X
更新日期:1999-01-01 00:00:00
abstract::Myo1b is a myosin that is exquisitely sensitive to tension. Its actin-attachment lifetime increases > 50-fold when its working stroke is opposed by 1 pN of force. The long attachment lifetime of myo1b under load raises the question: how are actin attachments that last >50 s in the presence of force regulated? Like mos...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2012.05.014
更新日期:2012-06-20 00:00:00
abstract::The current-voltage (I-V) relation of the background current, IK1, was studied in isolated canine cardiac Purkinje myocytes using the whole-cell, patch-clamp technique. Since Ba2+ and Cs+ block IK1, these cations were used to separate the I-V relation of IK1 from that of the whole cell. The I-V relation of IK1 was mea...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(87)83241-1
更新日期:1987-10-01 00:00:00
abstract::We present a combined experimental and computational study of the bundling of F-actin filaments induced by lysozyme proteins. Synchrotron small-angle x-ray scattering results show that these bundles consist of close-packed columnar complexes in which the actin is held together by incommensurate, one-dimensional arrays...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.105.078253
更新日期:2006-06-15 00:00:00
abstract::Phosphorescence spectroscopy on mouse myeloma IgA J539 in rigid solution at 77K revealed the type of anomalous short-lived component in the tryptophan decay originally observed with lysozyme (Churchich, J.E., 1966. Biochim. Biophys. Acta. 120:406-412) and seen in a large number of Bence Jones proteins (Longworth, J.W....
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(89)82681-5
更新日期:1989-08-01 00:00:00
abstract::This study reports the solid-state NMR spectroscopic characterization of the amino-proximate transmembrane domain (TM-A) of a diverged microsomal delta12-desaturase (CREP-1) in a phospholipid bilayer. A series of TM-A peptides were synthesized with 2H-labeled side chains (Ala-53, -56, and -63, Leu-62, Val-50), and the...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.105.067884
更新日期:2006-02-15 00:00:00
abstract::The M2 protein from the influenza A virus forms a proton channel in the virion that is essential for infection. This tetrameric protein appears to form a four-helix bundle spanning the viral membrane. Here the solid-state NMR method, 2D polarization inversion spin exchange at magic angle (PISEMA), has been used to obt...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(00)76334-X
更新日期:2000-08-01 00:00:00
abstract::Gramicidin is a polypeptide antibiotic that forms monovalent cation-specific channels in membrane environments. In organic solvents and in lipids containing unsaturated fatty acid chains, it forms a double-helical "pore" structure, in which two monomers are intertwined. This form of gramicidin can bind two cations ins...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(96)79213-5
更新日期:1996-07-01 00:00:00
abstract::A new kinetic model of the Na(+)/H(+) exchanger (NHE) was developed by fitting a variety of major experimental findings, such as ion-dependencies, forward/reverse mode, and the turnover rate. The role of NHE in ion homeostasis was examined by implementing the NHE model in a minimum cell model including intracellular p...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2009.08.053
更新日期:2009-11-18 00:00:00
abstract::Despite the spontaneity of some in vitro protein-folding reactions, native folding in vivo often requires the participation of barrel-shaped multimeric complexes known as chaperonins. Although it has long been known that chaperonin substrates fold upon sequestration inside the chaperonin barrel, the precise mechanism ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.108.131037
更新日期:2008-10-01 00:00:00
abstract::Video-based particle tracking monitors the microscopic movement of labeled biomolecules and fluorescent probes within a complex cellular environment. Information gained from this technique enables us to extract the dynamic behavior of biomolecules and the local mechanical properties inside the cell from a tracked part...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2009.03.029
更新日期:2009-06-17 00:00:00
abstract::Two mesophilic/thermophilic variants of the G-domain of the elongation factor Tu were studied via molecular dynamics simulations. By analyzing the simulation data via the Voronoi space tessellation, we have found that the two proteins have the same macromolecular packing, while the water-exposed surface area is larger...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.105.078972
更新日期:2006-06-01 00:00:00
abstract::DNA represents a promising therapeutic and prophylactic macromolecule in treating genetic diseases, infectious diseases and cancers. The therapeutic potential of DNA is directly related to how DNA transports within the targeted tissue. In this study, fluorescence photobleaching recovery was used to examine the diffusi...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.105.077404
更新日期:2006-07-15 00:00:00
abstract::Proteolysis of the multimeric blood coagulation protein von Willebrand Factor (VWF) by ADAMTS13 is crucial for prevention of microvascular thrombosis. ADAMTS13 cleaves VWF within the mechanosensitive A2 domain, which is believed to open under shear flow. In this study, we combine fluorescence correlation spectroscopy ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2015.12.023
更新日期:2016-02-02 00:00:00
abstract::Evidence is presented for the existence of two forms of low-potential cytochrome a3. One appears to be similar to the low-spin form reported by Nicholls, P., and V. Hildebrandt (1978 Biochem. J. 173:65-72) and Wrigglesworth, J. M., J. Elsden, A. Chapman, N. Van der Water, and M. F. Grahn (1988. Biochim. Biophys. Acta....
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(90)82633-3
更新日期:1990-06-01 00:00:00
abstract::In this work, boundary element modeling is used to study the transport of highly charged rod-like model polyions of various length under a variety of different aqueous salt conditions. Transport properties considered include free solution electrophoretic mobility, translational diffusion, and the components of the "te...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(01)75900-0
更新日期:2001-11-01 00:00:00
abstract::Structural transition can be induced in charged micelles by increasing the ionic strength of the medium. We have monitored the organization and dynamics of the functionally important tryptophan residues of gramicidin in spherical and rod-shaped sodium dodecyl sulfate micelles utilizing a combination of wavelength-sele...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.105.060798
更新日期:2005-11-01 00:00:00