Abstract:
:The fluorescent Mg(2+) indicator furaptra (mag-fura-2) was introduced into single ventricular myocytes by incubation with its acetoxy-methyl ester form. The ratio of furaptra's fluorescence intensity at 382 and 350 nm was used to estimate the apparent cytoplasmic [Mg(2+)] ([Mg(2+)](i)). In Ca(2+)-free extracellular conditions (0.1 mM EGTA) at 25 degrees C, [Mg(2+)](i) averaged 0.842 +/- 0.019 mM. After the cells were loaded with Mg(2+) by exposure to high extracellular [Mg(2+)] ([Mg(2+)](o)), reduction of [Mg(2+)](o) to 1 mM (in the presence of extracellular Na(+)) induced a decrease in [Mg(2+)](i). The rate of decrease in [Mg(2+)](i) was higher at higher [Mg(2+)](i), whereas raising [Mg(2+)](o) slowed the decrease in [Mg(2+)](i) with 50% reduction of the rate at approximately 10 mM [Mg(2+)](o). Because a part of the furaptra molecules were likely trapped inside intracellular organelles, we assessed possible contribution of the indicator fluorescence emitted from the organelles. When the cell membranes of furaptra-loaded myocytes were permeabilized with saponin (25 microg/ml for 5 min), furaptra fluorescence intensity at 350-nm excitation decreased to 22%; thus approximately 78% of furaptra fluorescence appeared to represent cytoplasmic [Mg(2+)] ([Mg(2+)](c)), whereas the residual 22% likely represented [Mg(2+)] in organelles (primarily mitochondria as revealed by fluorescence imaging). [Mg(2+)] calibrated from the residual furaptra fluorescence ([Mg(2+)](r)) was 0.6-0.7 mM in bathing solution [Mg(2+)] (i.e., [Mg(2+)](c) of the skinned myocytes) of either 0.8 mM or 4.0 mM, suggesting that [Mg(2+)](r) was lower than and virtually insensitive to [Mg(2+)](c). We therefore corrected furaptra fluorescence signals measured in intact myocytes for this insensitive fraction of fluorescence to estimate [Mg(2+)](c). In addition, by utilizing concentration and dissociation constant values of known cytoplasmic Mg(2+) buffers, we calculated changes in total Mg concentration to obtain quantitative information on Mg(2+) flux across the cell membrane. The calculations indicate that, in the presence of extracellular Na(+), Mg(2+) efflux is markedly activated by [Mg(2+)](c) above the normal basal level (approximately 0.9 mM), with a half-maximal activation of approximately 1.9 mM [Mg(2+)](c). We conclude that [Mg(2+)](c) is tightly regulated by an Mg(2+) efflux that is dependent on extracellular [Na(+)].
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Tursun P,Tashiro M,Konishi Mdoi
10.1529/biophysj.104.055517subject
Has Abstractpub_date
2005-03-01 00:00:00pages
1911-24issue
3eissn
0006-3495issn
1542-0086pii
S0006-3495(05)73254-9journal_volume
88pub_type
杂志文章abstract::Low frequency audible vibrations are produced by human skeletal muscles undergoing sustained contraction. The effect is easily demonstrable with an electronic stethoscope which amplifies sound below 50 Hz. Autocorrelation analysis of the signal shows that it is periodic with a frequency 25 +/- 2.5 Hz. The quality of t...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(80)85080-6
更新日期:1980-04-01 00:00:00
abstract::Pre-mRNA processing protein 40 (Prp40) is a nuclear protein that has a role in pre-mRNA splicing. Prp40 possesses two leucine-rich nuclear export signals, but little is known about the function of Prp40 in the export process. Another protein that has a role in protein export is centrin, a member of the EF-hand superfa...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2017.03.042
更新日期:2017-06-20 00:00:00
abstract::A 250 ps molecular dynamics simulation of the dimyristoylphosphatidylcholine (DMPC)-based lipid bilayer, including explicit water molecules, is reported. The solvent environment of the head groups and other structural properties of the bilayer have been analyzed and compared with experimental results as well as our pr...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(94)80889-6
更新日期:1994-04-01 00:00:00
abstract::In the outer hair cell (OHC), the extracisternal space (ECiS) is a conduit and reservoir of the molecular and ionic substrates of the lateral wall, including those necessary for electromotility. To determine the mechanisms through which molecules are transported in the ECiS of the OHC, we selectively imaged the time-d...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2009.06.011
更新日期:2009-08-19 00:00:00
abstract::A one-dimensional kinetic Ising model is developed to describe the binding of myosin subfragment 1 (SF-1) to regulated actin. The model allows for cooperative interactions between individual actin sites with bound SF-1 ligands rather than assuming that groups of actin monomer sites change their state in a cooperative ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(83)84286-6
更新日期:1983-11-01 00:00:00
abstract::A variety of experiments suggest that membrane proteins are important targets of anesthetic molecules, and that ion channels interact differently with anesthetics in their open and closed conformations. The availability of an open and a closed structural model for the KirBac1.1 potassium channel has made it possible t...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.107.119958
更新日期:2008-06-01 00:00:00
abstract::Phosphorus-31 nuclear magnetic resonance (31P-NMR) spectra were obtained from living toad retinae and toad retinal extracts at 4 degrees C. Several phosphorus metabolites--nucleoside di- and triphosphates (NTP), phosphocreatine, phosphodiesters, inorganic phosphate, and phosphomonoesters--were identified from the spec...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(89)82691-8
更新日期:1989-09-01 00:00:00
abstract::We examined the kinetics of voltage-dependent sodium currents in cerebellar Purkinje neurons using whole-cell recording from dissociated neurons. Unlike sodium currents in other cells, recovery from inactivation in Purkinje neurons is accompanied by a sizeable ionic current. Additionally, the extent and speed of recov...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(01)76052-3
更新日期:2001-02-01 00:00:00
abstract::We have used electron paramagnetic resonance (EPR) to probe the homo- and heterooligomeric interactions of reconstituted sarcoplasmic reticulum Ca-ATPase (SERCA) and its regulator phospholamban (PLB). SERCA is responsible for restoring calcium to the sarcoplasmic reticulum to allow muscle relaxation, whereas PLB inhib...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2012.08.032
更新日期:2012-09-19 00:00:00
abstract::Thermal inactivation of T(4) and lambda bacteriophage shows two components of differing sensitivity are present. These cannot be interpreted as owing to nucleic acid and protein. One protein function-the inhibition of radiation-induced DNA degradation-is lost with quite different thermal kinetics. lambda heated in the...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(71)86195-7
更新日期:1971-01-01 00:00:00
abstract::Formation of amyloid oligomers, the most toxic species of amyloids in degenerative diseases, is critically coupled to the interplay with surrounding water. The hydrophobic force driving the oligomerization causes water removal from interfaces, changing the surface-hydration properties. Here, we show that such effects ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2011.03.029
更新日期:2011-05-04 00:00:00
abstract::Integrin-mediated adhesion of circulating neutrophils to endothelium during inflammation involves multiple adhesion molecules on both neutrophils and endothelium. Most studies of neutrophil adhesion have focused on adhesion to ICAM-1 (mediated by beta(2) integrins), but interaction with the endothelial ligand vascular...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2008.10.001
更新日期:2009-01-01 00:00:00
abstract::Interactions between millimeter waves (MMWs) and biological systems have received increasing attention due to the growing use of MMW radiation in technologies ranging from experimental medical devices to telecommunications and airport security. Studies have shown that MMW exposure alters cellular function, especially ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2013.05.014
更新日期:2013-06-18 00:00:00
abstract::The crystal structure and a 96-ps molecular dynamics simulation used to analyze structural and motional contributions to spin-lattice (T1) relaxation times of phenylalanine and tyrosine C gamma carbons of the pancreatic trypsin inhibitor. The H beta and H delta protons geminal to C gamma are calculated to account for ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(82)84496-2
更新日期:1982-07-01 00:00:00
abstract::Subdenaturing concentrations of guanidine hydrochloride (GdnHCl) stabilize proteins. For ferrocytochrome c the stabilization is detected at subglobal level with no measured change in global stability. These deductions are made by comparing observed rates of thermally driven ferrocytochrome cHCO reactions with global u...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.104.044701
更新日期:2004-10-01 00:00:00
abstract::A novel system for measuring, simultaneously, ciliary beating and intracellular free calcium is presented. The advantages and dynamic nature of the system are demonstrated by measuring the effects of the calcium ionophore lonomycin and of extracellular ATP on ciliated rabbit trachea. The results are discussed with reg...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(94)80492-8
更新日期:1994-07-01 00:00:00
abstract::From the study of the kinetics of the fluorescence self-quenching of pyrene in multilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in the fluid phase we obtain the molecular diffusion parameters, diffusion coefficients, and activation energies for lateral diffusion for three probes: 1-palmitoy...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(01)76062-6
更新日期:2001-02-01 00:00:00
abstract::OVER A DECADE AND A HALF AGO, WHEN THE FIRST VISIBLE MEMBRANE SUSPENSION CIRCULAR DICHROIC (CD) SPECTRUM OF THE PURPLE MEMBRANE (PM) WAS PRESENTED, TWO MECHANISMS WERE PROPOSED TO ACCOUNT FOR THE OBSERVED BIPHASIC SHAPED CD BAND: (a) excitonic interactions among the retinals of the sole protein bacteriorhodopsin (bR) ...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(92)81701-0
更新日期:1992-11-01 00:00:00
abstract::Two modes of behavior of single human red cells in a shear field have been described. It is known that in low viscosity media and at shear rates less than 20 s-1, the cells rotate with a periodically varying angular velocity, in accord with the theory of Jeffery (1922) for oblate spheroids. In media of viscosity great...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(86)83734-1
更新日期:1986-05-01 00:00:00
abstract::Alamethicin and its analogs from cation selective, multi-conductance channels in lipid bilayers. The conductance levels have been thought to be due to a barrel-stave structure where conducting pores (barrels) are formed by the self-assembly of a variable number of alpha-helical rods (staves). The conductance transitio...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/s0006-3495(94)80784-2
更新日期:1994-02-01 00:00:00
abstract::The properties of vesicle membranes prepared from 16:0-SM, 16:0-DHSM, or DPPC were characterized using steady-state and time-resolved fluorescence spectroscopy and different fluorescent reporter molecules. The acyl-chain region was probed using free and phospholipid-bound 1,6-diphenyl-1,3,5-hexatriene. 16:0-DHSM was f...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(03)74915-7
更新日期:2003-02-01 00:00:00
abstract::The mechanical properties of cross-linked microtubule bundles were measured from outer pillar cells isolated from the mammalian inner ear. Measurements were made using a three-point bending test and were incorporated into a mathematical model designed to distinguish between the stiffness contributions from microtubule...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(97)78255-9
更新日期:1997-10-01 00:00:00
abstract::The molecular cascade that controls switching of the direction of rotation of Escherichia coli flagellar motors is well known, but the conformational changes that allow the rotor to switch are still unclear. The signaling molecule CheY, when phosphorylated, binds to the C-ring at the base of the rotor, raising the pro...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2017.12.001
更新日期:2018-02-06 00:00:00
abstract::The fusion peptides of HIV and influenza virus are crucial for viral entry into a host cell. We report the membrane-perturbing and structural properties of fusion peptides from the HA fusion protein of influenza virus and the gp41 fusion protein of HIV. Our goals were to determine: 1), how fusion peptides alter struct...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1529/biophysj.105.063032
更新日期:2005-11-01 00:00:00
abstract::A voltage clamp study has been performed in the presynaptic terminal of the squid stellate ganglion. After blockage of the voltage-dependent sodium and potassium conductances, an inward calcium current is demonstrated. Given a step-depolarization pulse, this voltage- and time-dependent conductance has an S-shaped onse...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(81)84898-9
更新日期:1981-03-01 00:00:00
abstract::Spin inversion transfer (SIT) NMR experiments are reported probing the thermodynamics and kinetics of interconversion of two folded forms of a GCN4-like leucine zipper near room temperature. The peptide is 13Calpha-labeled at position V9(a) and results are compared with prior findings for position L13(e). The SIT data...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/s0006-3495(99)77428-x
更新日期:1999-05-01 00:00:00
abstract::Fibrillar aggregation of the protein ataxin-3 is linked to the inherited neurodegenerative disorder Spinocerebellar ataxia type 3, a member of the polyQ expansion disease family. We previously reported that aggregation and stability of the nonpathological form of ataxin-3, carrying an unexpanded polyQ tract, are modul...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2011.02.056
更新日期:2011-04-20 00:00:00
abstract::Cryo-electron microscopy is rapidly emerging as a powerful technique to determine the structures of complex macromolecular systems elusive to other techniques. Because many of these systems are highly dynamical, characterizing their movements is also a crucial step to unravel their biological functions. To achieve thi...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/j.bpj.2018.02.028
更新日期:2018-04-10 00:00:00
abstract::We have developed a novel, spectroscopic technique for high-sensitivity, label-free DNA quantification. We demonstrate that an optical resonance (whispering gallery mode) excited in a micron-sized silica sphere can be used to detect and measure nucleic acids. The surface of the silica sphere is chemically modified wit...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(03)74625-6
更新日期:2003-09-01 00:00:00
abstract::Methods are described for discrimination of models of the gating kinetics and permeation of single ionic channels. Both maximum likelihood and regression procedures are discussed. In simple situations, where models are nested, standard hypothesis tests can be used. More commonly, however, non-nested models are of inte...
journal_title:Biophysical journal
pub_type: 杂志文章
doi:10.1016/S0006-3495(87)83331-3
更新日期:1987-02-01 00:00:00