X-Ray Diffraction Studies of the Cross-Bridge Intermediate States

1998 ◽  
pp. 271-279 ◽  
Author(s):  
S. Xu ◽  
S. Malinchik ◽  
S. Frisbie ◽  
J. Gu ◽  
T. Kraft ◽  
...  
Keyword(s):  
X Ray Diffraction ◽  
X Ray ◽  
Cross Bridge ◽  
Intermediate States ◽  
The Cross

scholarly journals Myosin Cross-Bridge Behaviour in Contracting Muscle—The T1 Curve of Huxley and Simmons (1971) Revisited

2019 ◽  
Vol 20 (19) ◽  
pp. 4892 ◽  
Author(s):  
Knupp ◽  
Squire
Keyword(s):  
Actin Filaments ◽  
Striated Muscle ◽  
Reliable Estimate ◽  
X Ray Diffraction ◽  
Step Size ◽  
X Ray ◽  
Cross Bridge ◽  
Length Changes ◽  
The Cross ◽  
Cross Bridges

The stiffness of the myosin cross-bridges is a key factor in analysing possible scenarios to explain myosin head changes during force generation in active muscles. The seminal study of Huxley and Simmons (1971: Nature 233: 533) suggested that most of the observed half-sarcomere instantaneous compliance (=1/stiffness) resides in the myosin heads. They showed with a so-called T1 plot that, after a very fast release, the half-sarcomere tension reduced to zero after a step size of about 60Å (later with improved experiments reduced to 40Å). However, later X-ray diffraction studies showed that myosin and actin filaments themselves stretch slightly under tension, which means that most (at least two-thirds) of the half sarcomere compliance comes from the filaments and not from cross-bridges. Here we have used a different approach, namely to model the compliances in a virtual half sarcomere structure in silico. We confirm that the T1 curve comes almost entirely from length changes in the myosin and actin filaments, because the calculated cross-bridge stiffness (probably greater than 0.4 pN/Å) is higher than previous studies have suggested. Our model demonstrates that the formulations produced by previous authors give very similar results to our model if the same starting parameters are used. However, we find that it is necessary to model the X-ray diffraction data as well as mechanics data to get a reliable estimate of the cross-bridge stiffness. In the light of the high cross-bridge stiffness found in the present study, we present a plausible modified scenario to describe aspects of the myosin cross-bridge cycle in active muscle. In particular, we suggest that, apart from the filament compliances, most of the cross-bridge contribution to the instantaneous T1 response may come from weakly-bound myosin heads, not myosin heads in strongly attached states. The strongly attached heads would still contribute to the T1 curve, but only in a very minor way, with a stiffness that we postulate could be around 0.1 pN/Å, a value which would generate a working stroke close to 100 Å from the hydrolysis of one ATP molecule. The new model can serve as a tool to calculate sarcomere elastic properties for any vertebrate striated muscle once various parameters have been determined (e.g., tension, T1 intercept, temperature, X-ray diffraction spacing results).

scholarly journals The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2623
Author(s):  
Monika Wójcik-Bania ◽  
Jakub Matusik
Keyword(s):  
Total Pore Volume ◽  
Cross Linking ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Cross ◽  
Chain Lengths ◽  
First Time ◽  
Substituent Influence ◽  
Benzyl Substituent

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH3)2R’NR]+, where R = C12, C14, C16, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

scholarly journals An X-ray diffraction study of the cross-circulated canine heart.

1977 ◽  
Vol 270 (2) ◽  
pp. 311-320 ◽  
Author(s):  
I Matsubara ◽  
H Suga ◽  
N Yagi
Keyword(s):  
Diffraction Study ◽  
Canine Heart ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Cross

On the Cross-Section Structure of the Mitochondrial Cristae-Membrane as Revealed by X-Ray Diffraction

1976 ◽  
Vol 31 (9-10) ◽  
pp. 612-621 ◽  
Author(s):  
W Müller-Klieser ◽  
W Kreutz
Keyword(s):  
Cross Section ◽  
Function Evaluation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Section Profile ◽  
The Cross ◽  
Diffraction Patterns ◽  
Cross Section Profile ◽  
Section Structure ◽  
Q Function

Abstract Mitochondria were isolated using sorbitol and high buffer concentration in the medium. X-ray diffraction patterns arising from the mitochondrial cristae-membrane were recorded in the fully dried state and in two different states in humidity. The Q-function evaluation of these X-ray dif­fraction diagrams resulted in electron density cross-section profiles, which consist of two main peaks of opposite sign and one, respectively two, smaller peaks. The total thickness of the membrane amounts to 120 Å in the dry and 140 Å to 160 Å in the wet state.An interpretation of the cross-section profile is tentatively proposed.

scholarly journals Cross-bridge conformation as revealed by x-ray diffraction studies on insect flight muscles with ATP analogues

1975 ◽  
Vol 15 (7) ◽  
pp. 687-705 ◽  
Author(s):  
R.S. Goody ◽  
K.C. Holmes ◽  
H.G. Mannherz ◽  
J.B. Leigh ◽  
G. Rosenbaum
Keyword(s):  
Insect Flight ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cross Bridge ◽  
Flight Muscles ◽  
Atp Analogues

X-ray diffraction studies on the cross-? form of poly (O-benzyl-L-serine)

Biopolymers ◽  
1990 ◽  
Vol 29 (8-9) ◽  
pp. 1125-1128 ◽  
Author(s):  
Yasuhiro Takeda
Keyword(s):  
X Ray Diffraction ◽  
X Ray ◽  
The Cross

scholarly journals Microbeam X-ray Diffraction from the Cross-section of Metallic Materials with Inhomogeneous Structure

1991 ◽  
Vol 77 (11) ◽  
pp. 2052-2059 ◽  
Author(s):  
Tizuko MAEDA ◽  
Keiichi MARUTA ◽  
Osamu FURUKIMI ◽  
Nobuyuki MORITO
Keyword(s):  
Cross Section ◽  
Inhomogeneous Structure ◽  
Metallic Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Cross
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