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Biomedical subjects

A Waheed

Publications and source records attributed to A Waheed.

212 records · Page 12Linked to original sources
PubMed1977

Purification and properties of the urea amidolyase from Candida utilis.

Urea amidolyase was purified to homogeneity from extracts of Candida utilis. The purification involves protamine sulfate precipitation, ammonium sulfate precipitation, polyethylene glycol precipitation, Sepharose 6B gel filtration, DEAE-cellulose column chromatography, and hydroxylapatite column chromatography. The final preparation is pure as judged by disc-gel electrophoresis. The molecular weight of urea amidolyase, as determined by gel filtration and disc-gel electrophoresis, is between 500,000 and 520,000. Treatment with sodium dodecyl sulfate results in two peptides with molecular weights of 70,000 and 170,000. The urea carboxylase and allophanate hydrolase activities of urea amidolyase may be distinguished from one another on the basis of (a) the effect of the stabilizers, urea and glycerol, (b) the effect of storage pH on activity, and (c) selective inhibition by sulfhydryl reagents.

Candida↗
PubMed1975

Hydrogen-ion titration curve of ovomucoid.

A systematic study of the H+ titration curve of purified ovomucoid was made at three temperatures (15, 25 and 35 degrees C) and three ionic strengths (0.05, 0.15 and 1.0). In all, 49 protons were dissociated reversibly in the pH range, 2.0-12.0. From the analysis of the results up to pH 12.0, the numbers of different dissociable groups per 28 300 g protein, together with their intrinsic pK values in parentheses were found tp be' 27 sode-chain carboxyl (pKint=4.0), four imidazole (pKint=6.5), one alpha-amino (pKint=7.5), 12 epsilon-amino (pKint=9.6), one guanidino (pKint=11.8) and one alpha-carboxyl group with abnormally low pK. The total number of basic nitrogens per mole of the protein was 22 so that four guanidino groups remained untitrated up to pH 12.0. Spectrophotometric titration showed that three out of five phenolic groups were titrated reversibly up to pH 11.9 with an intrinsic pK of 10.25; the remaining two groups became accessible only on protein denaturation. Viscosity results suggested absence of conformational change in the pH range 2.0-11.2. This explains the constancy of the pK values of carboxyl groups in the pH range 2.0-5.0. The empirical value of the electrostatic interaction factor, w, was 0.04, both in the carboxyl and phenolic regions.

Amino Acids↗
PubMed1975

Isolation and characterization of a variant of ovomucoid.

A simple procedure, which can be used on a preparative scale, for the isolation and purification of a major variant of ovomucoid from egg white is described. Ovomucoid was precipitated by salt, and further fractionated by chromatography on sulphoethyl-Sephadex. It showed size homogeneity as revealed by gel chromatography and sodium dodecyl sulphate-polyacrylamide-gel electrophoresis where the mobility was consistent with a molecular weight of 28 300+/-2300. The inhibitor showed full antiryptic but no antichymotryptic activity. The u.v.-absorption and fluorescence characteristics indicated the absence of tryptophan. Polyacrylamide-gel electrophoresis in the presence of 9M-urea demonstrated absence of charge heterogeneity. The intrinsic viscosity of ovomucoid was 5.36ml/g which yielded an equivalent hydrodynamic radius (2.9nm), axial ratio (6.0) and frictional ratio (1.31) of the molecule. The Stokes radius (3.5nm), diffusion coefficient (7.8 times 10(-7 cm2/s) and frictional ratio (1.35) were calculated from gel-filtration data. These results suggest that ovomucoid exists in non-globular conformation under native conditions and that the deviation from the behaviour of a typical globular protein seems to be due both to asymmetry and hydration.

Animals↗
PubMed1974

Iron and aconitase activity.

Aconitase activated with Fe(2+), cysteine and ascorbate incorporates 1 g-atom of Fe(2+)/mol. Loss of this Fe(2+) by transfer to ferrozine, a Fe(2+) chelator, results in loss of activity. Ascorbate increases the rate of transfer of the essential Fe(2+) whereas citrate retards the rate of transfer. Transfer of Fe(2+) from inactive aconitase, 2 g-atoms of Fe/mol, can be accomplished in the presence of urea and ascorbate. The correlation of activity with the presence of an added g-atom of Fe(2+)/mol leads to the conclusion that active aconitase has only one active site per mol.

Aconitate Hydratase↗
PubMedDate not supplied

A survey about blood bank policies and procedures.

A questionnaire about blood bank policies and procedures was prepared and sent out to 170 hospitals across the nation, 50 per cent responded. There is wide variation in both technical and nontechnical policies and procedures. Serum is separated from the original tube within 8 hours by 68 per cent of the hospitals and in 32 per cent serum is never separated from the original tube. Auto-control is included by 66 per cent of hospitals in at least one phase of the antibody testing, 34 per cent do not include auto-control in any phase. Du testing of the recipient is done in 85 per cent of the hospitals and in 15 per cent Rho type is determined by the immediate spin reactions alone. Slide type is the only method used to determine ABO group of cells of the recipients in 10 per cent of the hospitals, 18 per cent use serum-cell suspension, 10 per cent use the applicator stick method and only 62 per cent use washed saline-cell suspension routinely. Compatiblity testing between a recipient and a donor vary from a one-tube major crossmatch to a three-tube major crossmatch and minor crossmatch.

ABO Blood-Group System↗
PubMedDate not supplied

Transfusion significance of Lewis system antibodies. Report on a nationwide survey.

A nationwide survey of hospital blood banks conducted in February 1979 indicated that the majority of respondents require only reagent tested Lea and/or Leb negative blood for transfusion to patients with Lewis system antibodies in their serum. The policy was followed even if the antibody(ies) no longer was demonstrable in the serum or was reactive at room temperature and below. Only 11.4 per cent select blood for these patients on the basis of major crossmatch compatibility alone; 56 per cent require only reagent tested antigen negative blood for transfusion under all circumstances. The results of this survey and a review of the literature indicate the need for further studies on the transfusion significance of Lewis system antibodies.

Blood Banks↗
PubMedDate not supplied

Delayed hemolytic transfusion reaction caused by anti-Jsb in a Js(a+b+) patient.

A 39-year-old multiparous woman developed a mixed field positive direct antiglobulin test within 15 days of receiving four units of crossmatch compatible red blood cells. Anti-Jsb was demonstrable in both the serum and the eluate. The case was further complicated by the fact that the patient's pretransfusion red blood cells typed as Js(b+). Serologic studies demonstrated that this was a case of allo-anti-Jsb in a Js(b+) patient which provides evidence of heterogeniety of the Js locus.

Adult↗