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Biomedical subjects

D W Reed

Publications and source records attributed to D W Reed.

At least 37 records · Page 2Linked to original sources
PubMed1976

Isolation and characterization of the unique prosthetic group of a green hemoprotein from human erythrocytes.

A simplified and streamlined purification scheme has been developed for the large scale isolation of a green hemoprotein from human erythrocytes. The isolation procedure involves hypotonic lysis, freezing of the hemolysate at -60 degrees, centrifugation, direct chromatography of the supernatant on DEAE-cellulose, and subsequent cation exchange, anion exchange, and gel filtration chromatography. Approximately 2 mumol of this anionic hemoprotein were isolated per liter of packed erythrocytes. The previous inability to separate the prosthetic group from the protein by conventional solvent extraction procedures was shown to be a consequence of the highly polar character of the heme and not due to covalent linkage between heme and protein. The polar nature and marked lability of the heme necessitated development of techniques for the extraction, purification, and derivatization of the prosthetic group. The heme was separated from the protein by membrane filtration in the presence of pyridine and alkali or by disc gel electrophoresis in the presence of cyanide. The heme was methylated with trimethyloxonium tetrafluoroborate and further derivatized. The heme derivatives were purified on columns of Sephadex LH-20 or alumina. Chromatography of the heme, heme methyl ester, acetylated heme ester, and the corresponding porphyrin derivatives suggests that the heme contains three carboxyl groups and one or more polar, acetylatable functional groups, probably hydroxyl groups. Spectral characterization of these compounds, as well as the derivatives resulting from reaction of the heme with NH2OH, NaHSO3, and Na2S2O4, show that the prosthetic group is a previously undescribed, formyl-containing heme that can be clearly distinguished from heme a, Spirographis heme, and all other naturally occurring prosthetic groups.

Erythrocytes↗
PubMed1975

Localization of photosynthetic reaction centers by antibody binding to chromatophore membranes from Rhodopseudomonas spheroides strain R26.

Rabbit antiserum against highly purified reaction center preparations was shown to react specifically with a single component of chromatophore membranes from Rhodopseudomonas spheroides strain R-26. The conjugate of purified gamma globulin and ferritin prepared with toluene diisocyanate was used to determine the localization of reaction centers in the chromatophore membranes. Virtually no antibody was bound by intact membranes. After removing the 9nm ATPase from these membranes by dilute EDTA treatment, a considerable amount of antibody was bound to the exposed outer membrane surface. The reaction center binding sites were estimated to be uniformly distributed with approx. 1 reaction center per 200 nm-2 of membrane surface. These results indicate that the reaction centers are located near the outer membrane surface but below the ATPase particles. Since the distribution of reaction centers and particles on rough faces seen by freeze-fracture particle may be a complex of a reaction center and other electron transfer components localized within the hydrophobic region of the membrane.

Animals↗
PubMed1972

Cyclic nucleotide phosphodiesterase: high activity in a mammalian photoreceptor.

Purified outer segments of bovine rods exhibit phosphodiesterase activity against adenosine and guanosine cyclic 3',5'-monophosphates (cyclic AMP and cyclic GMP). The enzyme hydrolyzed cyclic GMP more rapidly than cyclic AMP at low substrate concentrations. The presence of high phosphodiesterase activity in this highly specialized organelle suggests that this enzyme may function in control of cyclic nucleotide concentration during visual excitation or adaptation.

Animals↗