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Biomedical subjects

R J Cherry

Publications and source records attributed to R J Cherry.

At least 109 records · Page 6Linked to original sources
PubMed1976

A spectroscopic technique for measuring slow rotational diffusion of macromolecules. 1: Preparation and properties of a triplet probe.

Slow rotational diffusion may be investigated by measuring the decay of dichroism of flash-induced transient absorption changes of suitable probes. The preparation of the covalent ""triplets" probe eosin isothiocyanate is described together with investigations of spectroscopic properties of eosin-protein conjugates. Triplet state lifetimes of air-equilibrated solutions of eosin-protein conjugates are in the order of 10 mus, demonstrating that the probe is protected from oxygen quenching by the protein. Experiments with the sucrase-isomaltase complex from small intestine show that its enzymatic activity is little affected by binding up to 2 mol of eosin/mol of protein.

Animals↗
PubMed1976

A spectroscopic technique for measuring slow rotational diffusion of macromolecules. 2: Determination of rotational correlation times of proteins in solution.

Experiments have been performed to test the validity of measurements of slow rotational diffusion using eosin isothiocyanate as a probe. When eosin-protein conjugates are covalently bound to Sepharose 4B, the dichroism of the flash-induced absorption transient does not decay with time. The magnitude of the dichroism is smaller than for eosin in solid solution. These results, together with measurements with highly viscous solutions, demonstrate the existence of a rapid but restricted independent motion of the eosin probe. This causes a partial loss of pf dochroism leaving a residual dichroism whose time dependence is determined by the rotational motion of the protein. Rotational correlation times in the microsecond-millisecond time range have been determined for eosinprotein conjugates dissolved in glycerol-water mixtures of varying viscosity. The measured values are in good agreement with theoretical predictions and show the correct dependence on the viscosity of the medium and the size and state of association of the protein.

Animals↗
PubMed1973

Phase transitions and heterogeneity in lipid bilayers.

The optical reflectivity of several well-characterized lipid bilayer systems has been correlated with calorimetric studies of the membrane components. There is a large increase in mean membrane thickness when a bilayer is cooled below the transition temperature of the membrane lipid. Similar studies on membranes generated from a mixture of two lipids possessing different degrees of unsaturation suggest that between the characteristic transition temperatures of the two lipids, the bilayer contains clusters of gel and liquid crystalline lipid which coexist within the plane of the membrane.

Calorimetry↗