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Biomedical subjects

J B Robinson

Publications and source records attributed to J B Robinson.

At least 91 records · Page 5Linked to original sources

Affinity chromatography in nonionic detergent solutions.

Anionic dye affinity chromatography is commonly unproductive in the presence of nonionic detergents used to extract particulate proteins. Using lactate dehydrogenase as a model protein, Cibacron blue F3GA as a model dye, and Triton X-100 as a model detergent, we find that the dye is encapsulated in nonionic detergent micelles, rendering the dye incapable of ligation with the enzyme. However, the dye can be liberatd from the micelles without altering the nonionic detergent concentration by addition of an anionic detergent, such as deoxycholate or sodium dodecyl sulfate, forming mixed anionic/nonionic micelles that displace the anionic dye. Encapsulation of the anionic detergents prevents their activity as protein denaturants. These observations have been successfuly translated to the dye affinity chromatography of a detergent extract of brain particulate cyclic nucleotide phosphodiesterase.

Animals↗

Differentiation-linked expression of cell surface markers on HL-60 leukemic cells.

The cell surface antigenic phenotype of HL-60, a human acute promyelocytic leukemia cell line, has been analyzed before and after maturation induction with dimethylsulfoxide (DMSO) using a panel of markers including a "library" of monoclonal antibodies and "conventional" antisera in conjunction with the fluorescene-activated cell sorter. HL-60 cells express granulocyte and "leukocyte" differentiation antigens but not antigens of the lymphoid, platelet, and erythroid lineages. DMSO-induced morphological maturation was found to be associated with a decrease in the proportion of cells in mitotic cycle, induction of C3d receptors, increased expression of granulocytic and leukocyte antigens, and diminished expression of HLA-A,B,C and beta 2-microglobulin determinants. HL-60 cells have no detectable expression of HLA-DR-associated determinants as assayed by rabbit anti-p28,33 monoclonal anti-HLA-DR (monomorphic determinant), and HLA-DRw typing alloantisera. The relationship of these changes in cell surface properties to normal granulocytic differentiation is discussed.

Animals↗

Studies on human heart citrate synthase.

Citrate synthase from human heart was purified by affinity chromatography with Sepharose-ATP. The molecular weight (100,000) and the presence of two presumably identical subunits do not differ from other mammalian citrate synthases. However, the kinetics constants and immunologic characteristics of the enzyme differed from other mammalian citrate synthases. The Km values for acetyl-CoA (0.4 microM) and oxaloacetate (0.25 microM) were about an order of magnitude lower than those previously found for other mammalian (and eucaryotic) citrate synthases. The kinetics constants for the reverse reaction Km for citrate (420 microM) and CoA (70 microM), were of similar magnitude to the values for other mammals. Anti-human heart antiserum developed a single precipitin line in an Ouchterlony plate against a heart extract, no precipitin line with brain, and a precipitin line with spurs against liver and kidney extract. Following myocardial infarction in men, the enzyme appeared in peripheral blood rarely and in low concentration in contrast with earlier experiences with experimental infarction in dogs.

Animals↗

Lazy leucocyte syndrome--disorder of the granulocyte membrane?

An adult with long-standing neutropenia had the functional granulocyte abnormalities typical of the lazy leucocyte syndrome. Scanning electron microscopy of the patient's neutrophils showed alteration in the surface configuration of the cell with coarsening of the normal fine ruffles and the appearance of knob-like projections. Similar functional and anatomical changes were induced in normal neutrophils by treatment with vinblastine. The lazy leucocyte syndrome may be a consequence of altered membrane microfilamentous protein structure or function, and undue rigidity of the affected neutrophils may explain the clinicopathological features of the disease.

Adult↗

On the structure of the prosthetic group of citrate (pro-3S)-lyase.

The prosthetic group of citrate (pro-3S)-lyase from Klebsiella aerogenes as well as Streptococcus diacetilactis was obtained eigher by beta elimination or pronase digestion of the enzyme and purified by DEAE-cellulose chromatography. The compound was shown to contain 3 mol of PO4, 2 mol of ribose, and 1 mol of sulfhydryl/mol of adenine. 5'-AMP and dephospho-CoA are components of the prosthetic group. The evidence obtained so far support our proposed structure of 3' (or 2') leads to 1''-(5''-phosphoribosyl)dephospho-CoA for the prosthetic group of citrate lyase. The presence of one phosphomonoester group in the compound isolated after beta elimination and the absence of the same in the compound isolated after pronase digestion indicated that the prosthetic group is attached to the enzyme through a phosphodiester bond. Analyses of the pyruvate released by beta elimination and subsequent acid hydrolysis of the peptide-bound prosthetic group and its degradation products showed that the phosphodiester linkage is between the hydroxyl group of a serine residue of the protein and the 5''-PO4 group of the second ribose.

ATP Citrate (pro-S)-Lyase↗

Structure of the prosthetic group of Klebsiella aerogenes citrate (pro-3S)-lyase.

The prosthetic group of citrate (pro-3S)-lyase [citrate oxaloacetate-lyase (pro-3S-CH2COO- leads to acetate); EC 4.1.3.6] from Klebsiella aerogenes was obtained by mild alkaline hydrolysis of the enzyme and purified by DEAE-cellulose chromatography. Several chemical and enzymatic degradation products of the compound have been isolated, and analyses of these have shown the structure of the prosthetic group to be 3'(or 2') leads to 1 inch-(5 inches-phosphoribosyl) dephosphocoenzyme A. Proof as to the exact linkage between the two ribose moieties and the anomeric configuration of the glycosidic bonds has not yet been obtained. A similar analysis was obtained for a product isolated after Pronase digestion of the enzyme (without alkaline hydrolysis). The isolated prosthetic group also can serve as a substrate for a crude preparation of acetate:-SH-(acyl carrier protein) enzyme ligase (AMP) from K. aerogenes, pure pig heart citrate (si)-synthase (EC 4.1.3.7), and pure rat liver ATP citrate (pro-3S)-lyase (EC4.1.3.8). This compound is the first shown to substitute for coenzyme A in the latter reaction.

Carbohydrates↗

Alpha-methyl derivatives of biogenic amines as inhibitors of monoamin oxidase.

The values of Km app and Vmax for three natural substrates of monoamine oxidase have been determined at various stages in the isolation of the enzyme from rat liver tissue. The results are consistent with the presence in the enzyme preparation of at least two distinct molecular forms of the enzyme. Using the alpha-methyl derivatives of the natural substrates as inhibitors of the enzyme, the substrate dependence of Ki further substantiates this view. In addition, the kinetics of the inhibition suggest that the value of Km app may not for all substrates, necessarily be a measure of the affinity of the substrate for the enzyme.

Amphetamines↗

Granulocyte function in untreated acute and chronic granulocytic leukemia.

Untreated patients with acute granulocytic leukemia showed impairment of microbicidal activity and,, in one, this was associated with myeloperoxidase deficiency and staphylococcal infection. In chronic granulocytic leukemia, there was no significant impairment of microbial killing. However, reduction in the capacity to reduce nitro-blue tetrazolium indicated some disturbance of neutrophil function in this disorder.

Adolescent↗