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A A Joshi

Publications and source records attributed to A A Joshi.

7 recordsLinked to original sources
PubMed2001

Consequence of beta 16 and beta 112 replacements on the kinetics of hemoglobin assembly.

The rates of alpha/beta monomer combination of four beta(A) variants (beta 112C --> S, beta 112C --> D, beta 112C --> T, and beta 112C --> V) in the presence and absence of beta 16G --> D (beta(J)) were measured in an attempt to assess the consequences of amino acid substitution at both a surface (beta 16) and an alpha(1)beta(1) interface (beta 112) residue on oxyhemoglobin assembly. Rates of alpha/beta monomer combination determined spectrally in 0.1 M Tris-HCl, 0.1 M NaCl, 1 mM EDTA, pH 7.4, at 21.5 degrees C differed by over 40-fold (22 +/- 2.0 to 0.49 +/- 0.1 x 10(5) M(-1) s(-1)), and were in the order: HbA beta 112S = HbJ beta 16D, beta 112S > HbA beta 112D = HbJ beta 16D, beta 112D > HbA > Hb J > HbA beta 112T = HbJ beta 16D, beta 112T > HbJ beta 16D, beta 112V > HbA beta 112V. This extensive kinetic investigation of single/double amino acid-substituted recombinant hemoglobin molecules, in conjunction with molecular modeling studies, has allowed examination of an array of unique alpha/beta subunit interactions and assembly processes.

Amino Acid Substitution↗
PubMed1994

Effect of carboxyterminal modification on the oligomeric structure of human beta hemoglobin.

A broad beta chain band region containing multiple components was observed with both native beta and Des(His-146, Tyr-145) beta chains following isoelectric focusing on agarose gels (pH 6.0-8.0). In contrast to the tetramer-monomer system of beta chains, a distinct separation of three components (tetramer, dimer and monomer) was seen for Des(His-146, Tyr-145) beta chains indicative of an oligomeric structural beta model with a stable dimer species. Protein dilution (500 to 15.6 microM in heme) amplified the more cathodic (presumably dimeric and monomeric) components of these chains, and titration with partner alpha chains resulted in a selective depletion of the monomer (most cathodic) component which could be quantitatively correlated with assembly of the hemoglobin tetramer.

Crystallography, X-Ray↗
PubMed1994

Role of alpha and beta carboxyl-terminal residues in the kinetics of human oxyhemoglobin dimer assembly.

Human oxyhemoglobin assembly was evaluated in the Soret region by rapidly mixing normal and carboxypeptidase-digested chains (1-10 x 10(-6) M, heme basis) in 0.1 M Tris-HCl, 0.1 M NaCl, 1 mM EDTA, pH 7.4, at 21.5 degrees C. Rate constants of 1.14 (+/- 0.09) and 2.11 (+/- 0.06) x 10(5) M-1 S-1 were measured for the association of Des(Arg-141) alpha with beta A and alpha A with beta A chains, respectively. The slower combination rate of Des(Arg-141) alpha with beta A chains is in agreement with that predicted solely on the basis of electrostatic considerations, as are the measured rate constants of 0.75 (+/- 0.12) and 1.86 (+/- 0.08) x 10(5) M-1 S-1 obtained for the combination of Des(Arg-141) alpha with variant beta S (Glu-6-->Val) and beta N Baltimore (Lys-95-->Glu) chains, respectively. However, the combination rates of alpha A and Des(Arg-141) alpha with beta A chains measured in the pH range from 7.0 to 9.0 demonstrated that the altered overall surface charge was not the only determinant of the assembly rates observed for Des(Arg-141) alpha chains. Furthermore, a rate constant of 11.3 (+/- 0.05) x 10(5) M-1 S-1 (which is 5.4-fold faster than the rate of alpha A beta A dimer assembly) was observed for Des(His-146,Tyr-145) beta chains. These kinetic studies suggest a critical role for the carboxyl-terminal domain in the assembly of human hemoglobin in vitro and perhaps in vivo.

Amino Acid Sequence↗
PubMed1993

Baby enemy cots.

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Beds↗
PubMedDate not supplied

Effects of enfenamic acid on renal electrolyte excretion in hypertensive patients.

Single and multiple doses of enfenamic acid were compared in hypertensive patients with those of hydrochlorothiazide using urinary output and electrolytes as parameters. With enfenamic acid, excretion of Na+, K+, and Cl- was significantly decreased in the multiple-dose study; after single doses, there was a significant decrease in the excretion of Na+ and Cl- only.

Adult↗