Physiological chemistry and physics最新文献

The Hodgkin, Huxley, and Katz theories of resting and action potentials are based on the membrane theory, which holds that cell K+ and water exist in the free state. Reviewed here are these theories of cellular potential along with the results of experimental testings. Reviewed also is Ling's association-induction (AI) hypothesis, which holds that all K+ is absorbed selectively and singly on anionic protein sites and that cell water is absorbed in multilayers on extended chains of "matrix proteins." In the development of the AI model, molecular mechanisms of cell permeation and electric potentials were presented according to which the potentials are surface-adsorption phenomena. Thus they resemble those suggested by Baur rather than the membrane potentials proposed by Ostwald and Bernstein. In the present review it is shown that the AI version of the surface adsorption model can account for evidence supporting the Hodgkin, Huxley, Katz approach as well as evidence against it-including extensive recent confirmation of the absorbed state of K+ in muscle.

PGBx, a polymeric prostaglandin, in chronic doses therapeutic for hereditary diabetes and hereditary obesity in mice, produces significant increases of blood neutrophils and lymphocytes in normal mice, hereditary diabetic mice, and hereditary obese mice. For lymphocytes, but not for neutrophils, the direction of the PGBx effect reverses at doses above 10 micrograms/g of body weight.

On the basis of the interaction between tritiated PGBx and rat liver mitochondria, it appears that PGBx interacts with rat liver mitochondria to form a complex. At low PGBx-mitochondrial ratios, one effect of this complex formation is to stabilize the phosphorylation activity of rat liver mitochondria when exposed for short times to hypotonic solutions. At higher PGBx-mitochondrial ratios, PGBx fails to show this effect. At low PGBx concentrations, PGBx is also shown to inhibit release of amino acids and proteins as well as glutamic acid dehydrogenase and monoamine oxidase from the mitochondria and to inhibit mitochondrial swelling.

To determine a band model for synthetic melanin obtained by autooxidation of L-dopa (3,4-dihydroxyphenyl-L-alanine), dependence of dark current on temperature in the range 298-333 degrees K was measured as well as dependence of optical absorption coefficient on wave-length in the range 250-800 nm. It was found that up to 311 degrees K thermal activation energy equals 0.1 eV and above 313 degrees K it equals 0.78 eV. The first value is connected with the band of localized states at the Fermi level. Optical gap, determined from optical absorption measurements is equal to 1.40 eV. The estimated value of sigma o, assuming the value of thermal coefficient of activation-energy to be gamma = 5 X 10(-4) eV/degrees K, is 2 X 10(-6) omega -1 cm-1 for 0.1 eV and 5 X 10(2) omega -1 cm-1 for 0.78 eV. Density of states in the valence band is N(EV) = 8 X 10(21)/cm3 X eV, and in the band of localized states at the Fermi level N(EF) = 3 X 10(13)/cm3 X eV.

The reaction kinetics of carbon monoxide and oxygen binding to slow reacting T-state "deoxy" hemoglobin (HbT) in human red blood cell (RBC) suspensions were studied with a 300-ns pulse width dye laser to photodissociate either HbCO or HbO2. The rate constants were determined using only the first 10% of the slow HbT reaction, as at longer times diffusion of ligand away from the RBC seriously affects the kinetics. The rate constants measured are similar to those in solution, indicating that the different physical environment in the RBC has little effect on the Hb kinetics.

Retina is an excitable system containing approximately 90% water. As we found that deuteration selectively changes amplitudes and latencies of retina biopotentials, specifically the ON and OFF responses, we used it to probe the role of water in those processes. A study of the retina deuteration kinetics was simultaneously performed. This revealed the existence of at least two retinal water compartments. The data suggested a third compartment also, with a lower motional "degree of freedom," existing where H2O-D2O exchange becomes important only after saturation by D2O of the first two compartments. Correlation of the electrophysiological effects of D2O with the kinetic data suggests that the ON response is related to the first water compartment and the OFF response to the third. The results point to independence on the ON and OFF response mechanisms and, very probably, to their different morphological origins.

In the process of protein evolution, amino acid residues at certain sites are fixed by natural selection, indicating that such residues are important structurally and functionally. Analysis has revealed some useful observations concerning their specificity contributions. Physicochemical and conformational characteristics of amino acid residues do not seem to fully explain their occurrence probability at the conservative sites. The relative preferences of residues at these sites could be important in the control of biochemical specificity.

Kinetic parameters of enzymatic reactions and contractile responses induced by adenosine triphosphate were studied using actomyosin suspensions or glycerinated muscle fibers. The results showed excellent correlations between the enzymatic and contractile events in both muscle models. Based on comparison of the kinetic constants of the two models, it is proposed that superprecipitation and supercontraction are similar expressions of an ATP-induced contractile response in muscle models of various levels of organization.