Biomedical subjects

L S Batchelder

Publications and source records attributed to L S Batchelder.

3 recordsLinked to original sources

PubMed1983

Mobility and function in elastin and collagen.

13C- and 2H-labelled amino acids have been incorporated into elastin and collagen and rotational correlation times of the labelled sites have been derived from an analysis of nuclear magnetic resonance relaxation parameters and line-shapes. The elastin experiments were designed to discriminate between the various models that have been proposed to account for the rubber-like elasticity of elastin. The correlation times of carbonyl carbons of the elastin backbone show that elastin chains are very flexible at the molecular level. In addition, the molecular dynamics and viscoelastic behaviour of elastin are well correlated over a wide range of temperatures and solvents. These results all support the rubber-like network model of elastin structure. The collagen experiments were designed to investigate the intermolecular interactions between molecules in collagen fibres. Correlation times of labelled sites in the collagen backbone and side-chains show that substantial flexibility, especially of the side-chains, takes place in reconstituted (non-cross-linked) collagen fibrils. Therefore, the interactions between side-chains that presumably direct and stabilize the fibrillar assembly take place in fluid domains. The molecular flexibility is not affected by the presence of cross-links but is absent when the collagen is mineralized.

Animals↗

PubMed1982

Characterization of leucine side-chain reorientation in collagen-fibrils by solid-state 2H NMR.

We have used 2H quadrupole-echo NMR spectroscopy to study the molecular dynamics of the leucine side chain in collagen fibrils labeled with [2H10]leucine. X-ray crystallographic studies of leucine and small leucyl-containing peptides and proteins [Benedetti, C. (1977) in Proceedings of the Fifth American Peptides Symposium, eds, Goodman, M. & Meienhofer, J. (Wiley, New York), pp. 257--274; Janin, J., Wodak, S., Levitt, M. & Maigret, B. (1978) J. Mol. Biol. 125, 357--386] show that the amino acid side chain exists predominantly in only two of the nine possible conformations. 2H NMR spectra of polycrystalline D,L [2H10]leucine obtained from -45 degrees C to +100 degrees C showed that interconversion of the two conformations did not take place on the 2H NMR timescale in this temperature range. In contrast, experimental lineshapes observed for [2H10]leucine-labeled collagen fibrils from -85 degrees C to +30 degrees C were simulated by using a model in which the side chain hops at various rates between the two predominant conformations found by the x-ray studies. A small difference between calculated and observed linewidths above the freezing point of water can be accounted for by backbone reorientation or by the presence of a small percentage of other side-chain conformations. Thus, these results provide strong evidence that the two predominant x-ray conformations not only exist in the fibrils as the preferred orientations but interconvert at rates that are proportional to temperature over the range - 85 degrees C to +30 degrees C. These observations concur with previous NNR studies of collagen fibrils that demonstrated a mobile contact region between collagen molecules.

Animals↗

PubMed1980

Deuterium nuclear magnetic resonance of specifically labeled native collagen. Investigation of protein molecular dynamics using the quadrupolar echo technique.

Collagen was labeled with [3,3,3-d3]alanine and with [d10]leucine via tissue culture. 2H nuclear magnetic resonance (NMR) spectra were obtained of collagen in solution and as fibrils using the quadrupolar echo technique. The 2H NMR data for [3,3,3-d3]alanine-labeled collagen fibrils were analyzed in terms of a model for motion in which the molecule is considered to jump between two sites, separated azimuthally by an angle 2 delta, in a time which is rapid compared with the residence time in both sites. The data suggest that the molecule undergoes reorientation over an angle, 2 delta, of approximately 30 degrees in the fibrils, and that the average angle between the alanine C alpha--C beta bond axis and the long axis of the helix is approximately 75 degrees. Reorientation is possibly segmental. The T2 for [3,3,3-d3]alanine-labeled collagen fibrils was estimated to be 105 mus. The 2H NMR data for the methyl groups of [d10]leucine-labeled collagen were analyzed qualitatively. These data established that for collagen in solution and as fibrils, rotation occurs about the leucine side-chain bonds, in addition to threefold methyl rotation and reorientation of the peptide backbone. The T2 for the methyl groups of leucine-labeled collagen is estimated to be approximately 130 mus. Taken together, these data provide strong evidence that both polypeptide backbone reorientation and amino acid side-chain motion occur in collagen molecules in the fibrils. Stabilizing interactions that determine fibril structure must therefore depend upon at least two sets of contacts in any given local region.

Alanine↗