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Biomedical subjects

M M Long

Publications and source records attributed to M M Long.

At least 37 records · Page 2Linked to original sources
PubMed1978

Cyclic analog of elastin polyhexapeptide exhibits an inverse temperature transition leading to crystallization.

The cyclic dodecapeptide analog of the linear polyhexapeptide of tropoelastin crystallizes from water on raising of the temperature and thereby demonstrates an inverse temperature transition implying dominant intermolecular hydrophobic interactions. The temperature profiles of turbidity (TP tau) of the cyclododecapeptide are analogous to those of the polyhexapeptide where increases in concentration lead to translations of the profiles to lower temperature without sharpening of the transition. The demonstration of increase in order with increase in temperature for the cyclododecapeptide in water and the similarity of TPtau's lends credence to the view that increases in temperature lead to increases in order, specifically, for the linear polyhexapeptide and, generally, for the precursor protein of the elastic fiber wherein the repeating hexapeptide occurs.

Crystallization↗
PubMed1976

Synthetic, cross-linked polypentapeptide fo tropoelastin: an anisotropic, fibrillar elastomer.

Physical properties of the cross-linked polypentapeptide of tropoelastin are reported along with chemical characterization of key intermediates in its synthesis. 220 MHz proton magnetic resonance spectra are reported on the constituent pentamers and their respective high polymers which verify structural and conformational integrity. Scanning electron microscopy of the cross-linked material formed without orientation and with flow orientation is reported. The former demonstrates the inherent fibrillar and anisotropic nature of the synthetic product. Stress-strain studies show the cross-linked polypentapeptide to exhibit elastomeric properties that are dependent on the water content of the matrix. At high water contents the elastic modulus is less than that of wet native aortic elastin and becomes greater on drying.

Binding Sites↗
PubMed1976

Cross-linked polypentapeptide of tropoelastin: an insoluble, serum calcifiable matrix.

The synthetic, cross-linked polypentapeptide of tropoelastin has been shown to calcify from serum alone even when separated from the serum medium by a dialysis membrane with a low-molecular-weight cut off. By microprobe analysis, it appeared that the only serum elements required for the calcification were calcium and phosphorus. Furthermore, thin sections of the calcified matrix showed the calcification to occur throughout the matrix, and thereby verified that it is a bulk property of the matrix and not an interfacial property. To our knowledge this is the first demonstration of an insoluble, synthetic polypeptide to function as a serum calcifiable matrix and by doing so it opens the door to potential medical applications.

Binding Sites↗
PubMed1976

Calcification of alpha-elastin coacervates: a bulk property of elastin.

Scanning electron microscopy and electron probe microanalysis studies are reported on thin sections of calcified coacervates of alpha-elastin. It is found that the capacity of elastin coacervates to initiate calcification is a bulk property of the coacervate and not limited to the serum-coacervate interface, that the calcium phosphate deposits act to bind the protein units together and slow the dissolution and spreading of the coacervate as it floats on an airwater interface, and that, within the limits of detectability, there is no involvement of sulfur. As the charged groups of alpha-elastin had been blocked, the initiation of deposition is due to neutral sites in the protein which are tightly bound to the calcium phosphate deposits.

Animals↗
PubMed1975

Studies on the conformation and interactions of elastin: nuclear magnetic resonance of the polyhexapeptide.

Synthesis, proton magnetic resonance and carbon-13 magnetic resonance characterizations, including complete assignments, are reported for the polyhexapeptide of elastin, HCO-Val(Ala1-Pro2-Gly3-Val4-Gly5-Val6)18-OMe. Temperature dependence of peptide NH chemical shifts and solvent dependence of peptide C-O chemical shifts have been determined in several solvents and have been interpreted in terms of four hydrogen bonded rings for each repeat of the polyhexapeptide. The more stable hydrogen bonded ring is a beta-turn involving Ala1C-O--HN-Val4. More dynamic hydrogen bonds are an 11-atom hydrogen bonded ring Gly3NH--O-C Gly5, a 7-atom hydrogen bonded ring (a gamma-turn) Gly3 C-O--NH-Gly5, and a 23-atom hydrogen bonded ring Val6inH--O-C Val6(i+1). This set of hydrogen bonds results in a right-handed beta-spiral structure with slightly more than two repeats (approximately 2.2) per turn of spiral. The beta-spiral structure is briefly discussed relative to data on the elastic fiber.

Amino Acid Sequence↗