Search PubMed⌕ Search

Biomedical subjects

D J Davis

Publications and source records attributed to D J Davis.

At least 73 records · Page 4Linked to original sources
PubMed1976

Protein-protein interactions of the light-harvesting chlorophyll a/b protein. II. Evidence for two stages of cation independent association.

In a previous paper, we observed a two-stage cation-independent association of the light-harvesting chlorophyll a/b protein from spinach chloroplasts based on concentration-dependent changes in the sedimentation coefficient. The two stages of association occurred between (2-4) and (4-7) mug/ml chlorophyll. In this paper, we provide further evidence for this association. This includes: (1) A decrease in the number of divalent cation binding sites in the second stage of association. (2) A corresponding decrease in the extent of the cation-dependent association. (3) A positive deviation from Beer's law for chlorophyll b for both stages of the cation-independent association and a positive deviation for chlorophyll a for the second stage of association only. (4) A change in the fluorescence emission of both chlorophyll a and b. The change for chlorophyll b was observed for both steps of association whereas that for chlorophyll a was observed for the second step of association only. Therefore, the first stage of association affects only chlorophyll b whereas the second stage alters the environment of both chlorophyll a and b. (5) In addition, divalent cations quenched chlorophyll fluorescence. However, the quenching which required 200-300 muM divalent cation for half-maximal effects was related neither to divalent cation binding nor to the divalent cation-induced association of the protein.

Aerobiosis↗
PubMed1976

Measurements of the prevalence of viral infections.

Viral diseases exert their major impact through morbidity, impairment of personal health, loss of time at work and school, and cost of medical care. Relatively few of the known viruses cause a significant number of deaths; influenza, childhood viral pneumonia, and hepatitis are the only viral diseases causing more than 1,000 deaths per year. Data based on the National Health Interview Survey of the National Center for Health Statistics show that the common cold annually causes 35.6 acute illnesses per 100 persons. The data reported by the National Therapeutic Disease Index (on the basis of visits by patients to a sample of 1,500 private physicians) show that influenza and other acute respiratory conditions account for about one-third of all visits to physicians. Nearly all viruses first infect humans in infancy and childhood, with a relatively low fatality rate but with frequent episodes of illness.

Adenoviridae↗
PubMed1975

Protein-protein interactions of light-harvesting pigment protein from spinach chloroplasts. I.Ca-2+ binding and its relation to protein association.

The role of divalent cations in the regulation of the distribution of excitation energy between the two photosystems involved in green plants photosynthesis has led us to search for a better understanding of how such phenomena might occur at the molecular level. Since small changes in orientation of and distance between pigment molecules could greatly affect the distribution of excitation energy, we have decided to study the effects of ions on the light-harvesting pigment protein from spinach chloroplasts. The light-harvesting pigment protein is shown to have two types of binding sites for Ca-2+. Binding studies and analytical ultracentrifugation indicate that site I (K-d equals 2.5 mu-M, n equals 1.5-4.0 mu-mol Ca-2+ bound/mg chlorophyll) is lost as the protein associates. Site II (K-d equals 32 mu-M, n equals 9,5 mu-mol Ca-2+/mg chlorophyll) is not affected by the association of the protein. This site is responsible, however, for a further divalent cation-dependent association of the protein. The possible role of this protein in grana stacking and control of spillover is discussed.

Calcium↗
PubMed1975

Reflections.

Explore the source record for details and available documents.

Allergy and Immunology↗
PubMed1971

A rapid automatic technique for generating operant key-press behavior in rats.

Experimentally naive rats were trained to key press on a fixed-ratio 10 schedule of food reinforcement by a completely automatic procedure within a single, 1-hr session. Control procedures demonstrated that the resulting behavior was an operant, under control of the schedule of reinforcement and the specified reinforcing stimulus (food). A simple, combination food-tray operandum, also described, was used as the basis for the training technique.

Journal Article↗