PubMed Health⌕ Search

Biomedical subjects

A S Chakraborti

Publications and source records attributed to A S Chakraborti.

8 recordsLinked to original sources
PubMed1996

Trifluoperazine is more effective than chlorpromazine in releasing oxygen from haemoglobin and myoglobin.

The extent of oxygen release from two heme proteins, haemoglobin and myoglobin have been studied in the presence of trifluoperazine and chlorpromazine (5-1000 microM). At a molar ratio (drug:protein) of 1.5, the release of oxygen from haemoglobin was 4 and 15% in the presence of chlorpromazine and trifluoperazine respectively, while from myoglobin the corresponding values were 20 and 40%. The findings were attributed to the greater extent of local conformational change around tryptophan moieties of each of the proteins induced by trifluoperazine.

Adult↗
PubMed1996

Comparative studies on the interaction of protoporphyrin with hemoglobin and myoglobin.

The binding parameters of protoporphyrin IX (PPIX) with hemoglobin (Hb) were studied spectrofluorimetrically and the results were compared with those of PPIX interacting with myoglobin (Mb). Two concentration ranges of PPIX (0.3 microM-1.5 microM and 1.5 microM-3.0 microM) were used. For both hemoglobin and myoglobin, the binding affinity constant (K) decreased while the number of binding sites (p) increased as the concentration range of PPIX increased. The interactions occurred in non-cooperative mode. Over a particular PPIX range, the interaction of PPIX with hemoglobin decreased significantly with increasing NaCl molarity indicating a trend in electrostatic interaction, whereas PPIX binding with myoglobin did not change significantly indicating mostly non-electrostatic mode of interaction. Total bound charge (z psi) decreased significantly with increased PPIX concentration range in case of hemoglobin-PPIX interaction, but remained almost same in case of myoglobin-PPIX interactions. Thermodynamic analysis revealed that binding of PPIX to hemoglobin was mostly electrostatic at lower concentration range of PPIX but became less electrostatic at higher concentration range and myoglobin-PPIX interaction, predominantly hydrophobic in nature, became more hydrophobic with increased range of PPIX concentration. The difference in binding modality between PPIX-Hb and PPIX-Mb has been discussed in relation to the state of aggregation of porphyrin as well as the subunit interaction property present and absent in hemoglobin and myoglobin, respectively.

Binding Sites↗
PubMed1986

Characterization of microsomal ATPases from developing human placenta.

Activities and some properties of microsomal ATPases have been studied in developing human placenta. The enzyme activities (Na+ + K+ + Mg2+, Mg2+, and Ca2+ dependent) in the placenta increase steadily with gestational age until the 18th to 21st week, and decrease in the second half of pregnancy. Mg2+-dependent and Na+ + K+ + Mg2+-dependent ATPases possess nearly the same Km (apparent) for ATP, while the Ca2+-dependent enzyme shows a different one. Mg2+-dependent ATPase shows higher substrate affinity than Ca2+-dependent ATPase, although the Vmax of the Mg2+-dependent enzyme is lower than that of the latter. However, for each enzyme, the Km remains almost constant and Vmax varies during ontogenic development. Vmax of the enzymes decline at term. The enzymes are heat-labile, unaffected by amino acids, namely, L-phenylalanine, L-leucine, and L-tryptophan, and deoxycholate inhibits the enzyme activities by about 50%.

Adenosine Triphosphatases↗
PubMed1986

Accumulation of a murein-membrane attachment site fraction when cell division is blocked in lkyD and cha mutants of Salmonella typhimurium and Escherichia coli.

Membrane fractionation studies were performed on Salmonella typhimurium lkyD(Ts) and E. coli cha(Ts) mutants that appeared to be blocked at a late stage of the cell division cycle. In both cases growth of the mutant strains at nonpermissive temperatures was associated with accumulation of a characteristic cell envelope fraction (fraction OML) that contained inner membrane, murein, and outer membrane components. The isolated fraction corresponded in composition and bouyant density to a fraction from wild-type strains that had previously been suggested (M. H. Bayer, G. P. Costello, and M. E. Bayer, J. Bacteriol. 149:758-767, 1982; K. Ishidate, E. S. Creeger, J. Zrike, S. Deb, B. Glauner, T. J. MacAlister, and L. I. Rothfield, J. Biol. Chem. 261:428-443, 1986) to contain adhesion sites between inner membrane, murein, and outer membrane. The accumulation of OML in LkyD- and Cha- cells was prevented by treatments that blocked DNA synthesis. The effects of interference with DNA synthesis did not appear to involve the SOS response.

Bacterial Outer Membrane Proteins↗
PubMed1982

Rate of formation of hydrogen peroxide (H2O2) in IUD-fitted human endometrium--a preliminary report.

Endometrial biopsy samples of (i) women (20-40 yr) using no contraceptive methods and (ii) women (25-45 yr) fitted with intrauterine contraceptive devices (CuT/Lippes loop) were analysed for the rate of H2O2 formation. The mean value for a normal proliferative endometrium was 10.56 +/- 1.45 nmoles H2O2 per milligram protein per 2 min, whereas the rate observed for samples of the same phase of the IUCD-fitted group without any bleeding episodes was 14.76 +/- 1.28 and that for members of the same group but who experienced excessive menstrual blood loss (menorrhagia) was 17.26 +/- 2.00, which was significantly higher than that of the control group.

Adult↗
PubMed1980

Relationship between mitochondrial ATPase and membrane lipids from developing human placenta.

Mitochondrial lipids and ATPase activity have been studied in developing human placenta. The enzyme activity in the placenta increases steadily with gestational age until the 18th to 21st week, and decreases in the second half of pregnancy. Both Mg2+ and Ca2+ ions have been found to activate the enzyme system. The solubilization of membrane lipids by deoxycholate inhibits the enzyme activity. Total lipid and total phospholipid contents of the mitochondrial membranes also increase during the early development of the placenta with peaks in the 14th to 17th week, after which the levels decrease. However, the percentage composition of individual phospholipids remains almost the same throughout pregnancy. The profile of the ATPase activity exhibits a correlation with that of membrane lipids in human placenta during intrauterine development of the tissue.

Adenosine Triphosphatases↗