Search PubMed⌕ Search

Biomedical subjects

B C Das

Publications and source records attributed to B C Das.

At least 109 records · Page 6Linked to original sources
PubMed1981

Culture media and species-related variations in the requirement of 5-bromodeoxyuridine for differential sister-chromatid staining.

Various concentrations of 5-bromodeoxyuridine (BdrU) ranging from 0.01 to 10.0 microgram/ml were tried for finding the minimal concentration required for differential staining of sister chromatids in lymphocytes of man, muntjac and cattle grown in three commonly used culture media, namely TC 199, Dulbecco's MEM and Ham's F-10. The lymphocytes grown in TC 199 required the lowest concentration of BrdU whereas it was highest for the lymphocytes grown in F-10. The minimal concentration varied for the 3 species studied, and it was not related to their DNA content. The differing amounts of thymidine and folic acid present in the various culture media seemed to account for the difference in the quantity of BdrU required for eliciting differential staining. Staining may also have depended on the intracellular nucleotide pool and/or on the difference in the substitutable dT sites of the genomes.

Animals↗
PubMed1980

Release of 1-O-alkylglyceryl 3-phosphorylcholine, O-deacetyl platelet-activating factor, from leukocytes: chemical ionization mass spectrometry of phospholipids.

Evidence is presented for the simultaneous release of platelet-activating factor (PAF-acether) and of its deacetylated derivative (lyso-PAF-acether) from hog leukocytes. On the basis of spectroscopy and chemical reactions, the structure of O-deacetyl-PAF is shown to be 1-O-alkylglyceryl 3-phosphorylcholine, an alkyl ether analog of lyso-phosphatidylcholine. Acetylation of lyso-PAF yields a compound with biological activity and chromatographical behavior indistinguishable from those of native PAF. Lyso-PAF may be considered to be either the precursor or the enzymatic degradation product of PAF. The usefulness of chemical ionization mass spectrometry for structural determination of phospholipids is also demonstrated.

Leukocytes↗
PubMed1979

Congeners of etamycin produced by Streptomyces griseoviridus.

Streptomyces griseoviridus produces in addition to etamycin several related compounds which can be separated by partition chromatography. One of these has been characterized by amino acid analysis and mass spectrometry and shown to have the same structure as etamycin except for replacement of the hydroxyproline residue by proline. Evidence was obtained for additional congeners similarly related to etamycin by amino acid exchange. The relative proportions of such congeners produced by S. griseoviridus depends upon the medium in which the culture is grown. Certain amino acids support good yields of the metabolites and the culture appears to be steered towards the synthesis of congeners containing such amino acids.

Anti-Bacterial Agents↗
PubMed1979

The identification of depsipeptides by chemical ionisation mass spectroscopy.

The chemical ionisation mass spectra of seven naturally occurring depsipeptides and some of their permethylated derivatives have been measured. The primary ionisation process involves an ester group and not an amide or other functionality. It probably occurs randomly when the molecule contains more than one ester link. Unlike electron impact mass spectra, those obtained under chemical ionisation conditions gave sequence information for all of the depsipeptides examined or their permethylated derivatives. A mechanism for the primary fragmentation is proposed.

Anti-Bacterial Agents↗
PubMed1978

Structure of iturine A, a peptidolipid antibiotic from Bacillus subtilis.

A mixture of iturines extracted from Bacillus subtilis gave, on column chromatography, iturine A, iturine B, and iturine C. Iturine A has the entire antifungal activity. It is a mixture of two homologous peptidolipids C48,H74N12O14 and C49H76N12O14 (mp 177 degrees C, [alpha]D-1.7 degrees in methanol (c 0.05 g/mL); mol wt 1042 and 1056). The lipid moiety is a mixture of 3-amino-12-methyltridecanoic acid and 3-amino-12-methyltetradecanoic acid. The peptide moiety contains 7 mol of amino acids: D-Asn2, L-Asn, L-Gln, L-Pro, L-Ser, and D-Tyr. A cyclic structure for iturine A with the serine residue linked to the fatty amino acids through a peptide bond has been domonstrated. By mild HCl hydrolysis, lipid-soluble and water-soluble peptides were obtained. They were analyzed by chemical methods and by mass spectrometry. Permethylated and perdeuteriomethylated derivatives of iturine A were also subjected to mass spectrometric analysis. Both chemical analysis and mass spectrometry led to the cyclic structure I for iturine A.

Amino Acid Sequence↗
PubMed1976

Sulfatides of Mycobacterium tuberculosis: the structure of the principal sulfatide (SL-I).

The gross structural features of five families of multiacylated trehalose 2-sulfates elaborated by Mycobacterium tuberculosis strain H37Rv are described. The principal sufatide SL-I is a 2,3,6,6'-tetraacyl-alpha,alphs'-D-trehalose 2'-sulfate, whose component carboxylate substituents (and homolgy) were previously established. In the present study the specific locations of the acyl substituents were assigned. The desulfated glycolipid (SL-I-CF) was methanolyzed on a column of diethylaminoethylcellulose (free base form), affording tri-, di-, and monoacylated trehalose mixtures. The most abundant diacyltrehalose generated was identified as 6,6'-bis-(2,4,6,8,10,12,14,16-octamethyl-17-hydroxydotriaconta-noyl)trehalose (6,6'-bis(C40-hydroxyphthioceranoyl)trehalose), along with lower and higher homologues.A small amount (about 15%) of the unhydroxylated analogue (phthioceranate) was also recognized. From the monoacylated carbohydrate mixture (chiefly 6-(C40-hydroxyphthioceranoyl)trehalose) surviving trehalose monopalmitate(s) were isolated by preparative gas chromatography of the trimethylsilylated products. Trehalose 2-palmitate was identified as the principal component. Small amounts of the 3 isomer may also be present, but no 6-palmitate was detectable. Gentle acidic solvolysis, which minimizes the possibility of acyl migrations, afforded a different diacyltrehalose, identified by mass spectrometry of the permethylated derivative as principally 2-palmitoyl(stearoyl)-3-phthioceranoyltrehalose. A variant in which hydroxyphthioceranate substitutes at the 3 position was also recognized. The results indicate that the biological acylation processes at the trehalose core are not entirely specific, but instead yield an SL-I family, for the chief member of which a logical structural expression is deduced.

Chromatography, Gas↗
PubMed1975

Cancer tonsil.

Explore the source record for details and available documents.

Adolescent↗