Search PubMed⌕ Search

Biomedical subjects

A G Walton

Publications and source records attributed to A G Walton.

At least 37 records · Page 2Linked to original sources
PubMed1974

The secondary structure of human Hageman factor (factor XII) and its alteration by activating agents.

Hageman factor (factor XII) is activated by exposure to surfaces such as glass or by solutions of certain compounds, notably ellagic acid. Changes in the structure of Hageman factor accompanying activation have been examined in this study by circular dichroism spectroscopy. The spectrum of unactivated Hageman factor in aqueous solutions suggests that its conformation is mainly aperiodic. Various perturbants altered the conformation of Hageman factor in differing ways, demonstrating the sensitivity of Hageman factor to its environment. After activation of Hageman factor with solutions of ellagic acid, a negative trough appeared in the region of the circular dichroism spectrum commonly assigned to tyrosine residues, along with other minor changes in the peptide spectral region. Some of these changes are similar to changes that occurred upon partial neutralization of the basic residues at alkali pH. Activation of Hageman factor by adsorption to quartz surfaces (in an aqueous environment) also produced changes similar to those in the ellagic acid-activated Hageman factor, including the negative ellipticity in the tyrosine region. These observations suggest that the activation process may be related to a change in status of some of the basic amino acid residues, coupled with a specific change in the environment of some tyrosine residues. The importance of these changes during the activation process remains to be determined. The sensitivity of Hageman factor to its environment is consistent with the view that the initiation of clotting by exposure of plasma to appropriate agents is brought about by alterations in the conformation of Hageman factor that occur in the apparent absence of Fletcher factor or other recognized clotting factors.

Adsorption↗
PubMed1971

A study of collagen and gelatin solutions by optical self beat spectroscopy.

A study of the conformation of collagen and gelatin in aqueous solution by Optical Self Beat Spectroscopy is reported. The translational diffusion coefficient of monomeric tropocollagen was experimentally measured from the half-width of the Rayleigh scattered radiation and the value obtained is shown to be in good agreement with that calculated from hydrodynamical theory for the tropocollagen rod. The Self Beat Spectrometer was also used to investigate the factors affecting the aggregation and flexing of molecules in dilute gelatin solutions and the gel-sol transition in more concentrated gelatin solutions.

Animals↗