Abstract：
:Collagen fibrils play an important role in the human body, providing tensile strength to connective tissues. These fibrils are characterized by a banding pattern with a D-period of 67 nm. The proposed origin of the D-period is the internal staggering of tropocollagen molecules within the fibril, leading to gap and overlap regions and a corresponding periodic density fluctuation. Using an atomic force microscope high-resolution modulus maps of collagen fibril segments, up to 80 μm in length, were acquired at indentation speeds around 10(5) nm/s. The maps revealed a periodic modulation corresponding to the D-period as well as previously undocumented micrometer scale fluctuations. Further analysis revealed a 4/5, gap/overlap, ratio in the measured modulus providing further support for the quarter-staggered model of collagen fibril axial structure. The modulus values obtained at indentation speeds around 10(5) nm/s are significantly larger than those previously reported. Probing the effect of indentation speed over four decades reveals two distinct logarithmic regimes of the measured modulus and point to the existence of a characteristic molecular relaxation time around 0.1 ms. Furthermore, collagen fibrils exposed to temperatures between 50 and 62°C and cooled back to room temperature show a sharp decrease in modulus and a sharp increase in fibril diameter. This is also associated with a disappearance of the D-period and the appearance of twisted subfibrils with a pitch in the micrometer range. Based on all these data and a similar behavior observed for cross-linked polymer networks below the glass transition temperature, we propose that collagen I fibrils may be in a glassy state while hydrated.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Baldwin SJ,Quigley AS,Clegg C,Kreplak Ldoi
10.1016/j.bpj.2014.09.003subject
Has Abstractpub_date
2014-10-21 00:00:00pages
1794-1801issue
8eissn
0006-3495issn
1542-0086pii
S0006-3495(14)00933-3journal_volume
107pub_type
杂志文章abstract：:ATP synthase (F-ATPase) operates as an electrochemical-to-mechanical-to-chemical energy transducer with an astounding 360 degrees rotary motion of subunits epsilongammac(10-14) (rotor) against delta(alphabeta)(3)ab(2) (stator). The enzyme's torque as a function of the angular reaction coordinate in relation to ATP-syn...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(01)75781-5
更新日期：2001-09-01 00:00:00
abstract：:This paper describes the relation between the quantum yield of photosynthesis in the red alga Porphyridium cruentum, and the spectral composition of light, changed by filtering white light through aqueous phycobilin solutions of increasing optical density. At sufficiently high densities of the filter solution, no meas...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/s0006-3495(60)86876-2
更新日期：1960-09-01 00:00:00
abstract：:High-efficiency electrofusion between cells of different sizes was achieved by application of fusing electric pulses to cells in centrifuged pellets. Larger target cells (Chinese hamster ovary or L1210 cells) were stacked among smaller human erythrocytes or erythrocyte ghosts by sequential centrifugation at 700 g to f...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(96)79249-4
更新日期：1996-07-01 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
abstract：:To investigate the properties of a pure liquid ordered (Lo) phase in a model membrane system, a series of saturated phosphatidylcholines combined with cholesterol were examined by variable temperature multinuclear (1H, 2H, 13C, 31P) solid-state NMR spectroscopy and x-ray scattering. Compositions with cholesterol conce...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1529/biophysj.104.056499
更新日期：2006-04-01 00:00:00
abstract：:The molecular weight of single-stranded DNA from the slime mold Physarum polycephalum has been determined by alkaline gradient centrifugation. The average molecular weight during DNA synthesis ( approximately 1.5 x 10(7) D) is less than that observed in nonsynthetic periods ( approximately 4 x 10(7) D). On the basis o...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(67)86590-1
更新日期：1967-05-01 00:00:00
abstract：:We find evidence for a direct transition of insulin monomers into amyloid fibrils without measurable concentrations of oligomers or protofibrils, suggesting that fibrillogenesis may occur directly from assembly of denaturing insulin monomers rather than by successive transitions through protofibril nuclei. To support ...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2010.10.010
更新日期：2010-12-15 00:00:00
abstract：:Heterogeneity of ADP diffusion and regulation of respiration were studied in permeabilized cardiomyocytes and cardiac fibers in situ and in silico. Regular arrangement of mitochondria in cells was altered by short-time treatment with trypsin and visualized by confocal microscopy. Manipulation of matrix volumes by chan...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(03)70065-4
更新日期：2003-05-01 00:00:00
abstract：:Red blood cells (RBCs) have highly deformable viscoelastic membranes exhibiting complex rheological response and rich hydrodynamic behavior governed by special elastic and bending properties and by the external/internal fluid and membrane viscosities. We present a multiscale RBC model that is able to predict RBC mecha...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2010.02.002
更新日期：2010-05-19 00:00:00
abstract：:Characterizing the ionic distribution around chromatin is important for understanding the electrostatic forces governing chromatin structure and function. Here we develop an electrostatic model to handle multivalent ions and compute the ionic distribution around a mesoscale chromatin model as a function of conformatio...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2010.08.023
更新日期：2010-10-20 00:00:00
abstract：:Hint2, one of the five members of the superfamily of the histidine triad AMP-lysine hydrolase proteins, is expressed in mitochondria of various cell types. In human adrenocarcinoma cells, Hint2 modulates Ca(2+) handling by mitochondria. As Hint2 is highly expressed in hepatocytes, we investigated if this protein affec...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2013.06.048
更新日期：2013-09-03 00:00:00
abstract：:The analysis of single-molecule fluorescence resonance energy transfer (FRET) trajectories has become one of significant biophysical interest. In deducing the transition rates between various states of a system for time-binned data, researchers have relied on simple, but often arbitrary methods of extracting rates fro...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1529/biophysj.106.082487
更新日期：2006-09-01 00:00:00
abstract：:The coupling between the mechanical properties of enzymes and their biological activity is a well-established feature that has been the object of numerous experimental and theoretical works. In particular, recent experiments show that enzymatic function can be modulated anisotropically by mechanical stress. We study s...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2010.09.026
更新日期：2010-11-17 00:00:00
abstract：:In the photocycle of bacteriorhodopsin at pH 7, a proton is ejected to the extracellular medium during the protonation of Asp-85 upon formation of the M intermediate. The group that releases the ejected proton does not become reprotonated until the prephotolysis state is restored from the N and O intermediates. In con...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2012.06.022
更新日期：2012-08-08 00:00:00
abstract：:A triple mutant of sperm whale myoglobin (Mb) [Leu(B10) --> Tyr, His(E7) --> Gln, and Thr(E10) --> Arg, called Mb-YQR], investigated by stopped-flow, laser photolysis, crystallography, and molecular dynamics (MD) simulations, proved to be quite unusual. Rebinding of photodissociated NO, O2, and CO from within the prot...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(99)77289-9
更新日期：1999-03-01 00:00:00
abstract：:As double-stranded DNA is stretched to its B-form contour length, models of polymer elasticity can describe the dramatic increase in measured force. When the molecule is stretched beyond this contour length, it shows a highly cooperative overstretching transition. We have measured the elasticity and overstretching tra...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(02)75658-0
更新日期：2002-06-01 00:00:00
abstract：:Thermodynamic parameters for the binding of the monovalent cations, Li+, Na+, K+, Rb+, Cs+, NH4+, TI+, and Ag+, to gramicidin A and for the binding of TI+ to gramicidin C, incorporated into lysophosphatidylcholine, have been determined using a combination of TI-205 nuclear magnetic resonance spectroscopy and competiti...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(88)82985-0
更新日期：1988-09-01 00:00:00
abstract：:Back-of-the-envelope or rule-of-thumb calculations involving rough estimates of quantities play a central scientific role in developing intuition about the structure and behavior of physical systems, for example in so-called Fermi problems in the physical sciences. Such calculations can be used to powerfully and quant...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2014.08.040
更新日期：2014-12-02 00:00:00
abstract：:Ultrasonic relaxation of multilamellar liposomes formed from dipalmitoylphosphatidylcholine was measured near the gel-to-liquid crystal transition by a differential ultrasonic resonator. The relaxation time and strength increased remarkably near the transition temperature, indicating a pseudocritical phenomenon. A qua...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(83)84379-3
更新日期：1983-05-01 00:00:00
abstract：:The cellular response to external mechanical forces has important effects on numerous biological phenomena. The sequences of molecular events that underlie the observed changes in cellular properties have yet to be elucidated in detail. Here we have detected the responses of a cultured cell against locally applied cyc...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2010.12.3693
更新日期：2011-02-02 00:00:00
abstract：:We used optical tweezers to analyze the effect of jasplakinolide and cyclodextrin on the force exerted by lamellipodia from developing growth cones (GCs) of isolated dorsal root ganglia (DRG) neurons. We found that 25 nM of jasplakinolide, which is known to inhibit actin filament turnover, reduced both the maximal exe...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2012.04.036
更新日期：2012-06-06 00:00:00
abstract：:Proteins fold and function in cellular environments that are crowded with other macromolecules. As a consequence of excluded volume effects, compact folded states of proteins should be indirectly stabilized due to destabilization of extended unfolded conformations. Here, we assess the role of excluded volume in terms ...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2012.12.020
更新日期：2013-02-05 00:00:00
abstract：:Homooligomerization of proline utilization A (PutA) bifunctional flavoenzymes is intimately tied to catalytic function and substrate channeling. PutA from Bradyrhizobium japonicum (BjPutA) is unique among PutAs in that it forms a tetramer in solution. Curiously, a dimeric BjPutA hot spot mutant was previously shown to...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2018.04.046
更新日期：2018-06-19 00:00:00
abstract：:Molecular sensors based on intramolecular Förster resonance energy transfer (FRET) have become versatile tools to monitor regulatory molecules in living tissue. However, their use is often compromised by low signal strength and excessive noise. We analyzed signal/noise (SNR) aspects of spectral FRET analysis methods, ...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2010.07.053
更新日期：2010-10-06 00:00:00
abstract：:Various differential polarization images or Mueller images of model objects are generated using the equations derived in the previous paper (paper I of this series). These calculated images include models of the higher-order organization of metaphase chromosomes, and show the applicability of the differential polariza...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(87)83286-1
更新日期：1987-12-01 00:00:00
abstract：:The mechanism of the "ground permeability" of the human erythrocyte membrane for K+ and Na+ was investigated with respect to a possible involvement of a previously unidentified specific transport pathway, because earlier studies showed that it cannot be explained on the basis of simple electrodiffusion. In particular,...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(97)78106-2
更新日期：1997-08-01 00:00:00
abstract：:Rates of diffusion through the extracellular space of thin sheets of myocardium from the right ventricular outflow tract of kittens were estimated at 23 degrees C for 45Ca2+ and an inert reference tracer, [14C]sucrose. The myocardial sheets were mounted in an Ussing chamber and equilibrated with Tyrode solution with v...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(77)85539-2
更新日期：1977-10-01 00:00:00
abstract：:Photoinduced electron transfer in photosystem I (PS I) proceeds from the excited primary electron donor P700 (a chlorophyll a dimer) via the primary acceptor A0 (chlorophyll a) and the secondary acceptor A1 (phylloquinone) to three [4Fe-4S] clusters, Fx, FA, and FB. Prereduction of the iron-sulfur clusters blocks elec...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(98)78023-3
更新日期：1998-06-01 00:00:00
abstract：:Calcium is essential for many biological processes involved in cellular motility. However, the pathway by which calcium influences motility, in processes such as muscle contraction and neuronal growth, is often indirect and complex. We establish a simple and direct mechanochemical link that shows how calcium quantitat...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/j.bpj.2009.02.069
更新日期：2009-08-19 00:00:00
abstract：:The physical characteristics which govern the water relations of the giant-celled sporangiophore of Phycomyces blakesleeanus were measured with the pressure probe technique and with nanoliter osmometry. These properties are important because they govern water uptake associated with cell growth and because they may in...
journal_title：Biophysical journal
pub_type： 杂志文章
doi：10.1016/S0006-3495(87)83363-5
更新日期：1987-03-01 00:00:00
