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Biomedical subjects

R Ali

Publications and source records attributed to R Ali.

At least 145 records · Page 8Linked to original sources
PubMed1988

The glycoprotein nature of pig kidney diamine oxidase. Role of disulphide groups and arginine residues in the concanavalin A-diamine oxidase interaction.

Pig kidney diamine oxidase (DAO) was found to contain 5% (w/w) natural hexose, 3.25% glucosamine, 2.61% N-acetylglucosamine and 0.25% N-acetylneuraminic acid. The enzyme exhibited strong affinity towards concanavalin A (Con A) with a stoichiometry of 1:4.6. The kinetics of interaction approached an apparent first-order rate, with a rate constant (Kapp.) value of 1.5 x 10(-2) min-1. The enzyme reduced with dithiothreitol followed by alkylation with iodoacetamide showed an increase in the stoichiometry of the Con A-DAO interaction. Similarly arginine modification by phenylglyoxal caused decreased affinity, with an altered Kapp. value of 9.09 x 10(-3) min-1. The results suggest that, besides the carbohydrate content, the protein moiety of the enzyme also plays a significant role in the Con A-DAO interaction.

Amine Oxidase (Copper-Containing)↗
PubMed1987

Immunological characterization of small nuclear ribonucleoproteins reactive with sera of patients with systemic lupus erythematosus.

We have previously reported the purification of Sm and RNP antigens from goat liver and identified two polypeptides of molecular weights 70 and 80-90 kd as RNP specific and of 14 and 30 kd as Sm specific. In this communication the effect of ribonuclease and trypsin on Sm and RNP antigens was studied at the polypeptide level. We found that the RNP antigenic determinant polypeptides of 70 and 80-90 kd are lost as a result of such treatment, whereas there is no effect on the Sm-specific 14- and 30-kd polypeptides. The role of RNA in the antigenicity of Sm and RNP was studied by dissociation and reconstitution studies. The antigens were fractionated into protein and RNA and the individual fractions were tested for Sm and RNP activity by counterimmunoelectrophoresis (CIE) and enzyme-linked immunosorbent assay (ELISA). The RNA fraction did not react alone with anti-Sm and anti-RNP sera with either of the assays. Conversely when the protein fraction was tested by CIE, only Sm antigenicity was detectable. In the ELISA both Sm and RNP activities were demonstrated in the protein fraction. These results show that the presence of RNA is important in the immunoprecipitation reactions involving only RNP antigen, whereas Sm activity is independent of RNA. In addition, when the reaction is carried out by an assay involving primary antigen-antibody reaction (e.g., ELISA), RNP antibodies react with protein fractions alone, without the presence of RNA. We also report the glycoprotein nature of Sm-specific polypeptides.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

The effect of anti-Z-DNA antibodies on the B-DNA-Z-DNA equilibrium.

Four different preparations of rabbit and goat anti-Z-DNA antibodies were examined to determine the effects of antibody binding on the B-DNA-Z-DNA equilibrium. One of the four antibodies, a goat IgG, caused a marked lowering in the ionic strength required for the B-DNA to Z-DNA transition in poly(dG-dC) X poly(dG-dC), shifting the midpoint from 2.25 to 2.0 M NaCl. This IgG had a more prominent high affinity antibody population than did the other goat IgG, which caused little change in the midpoint of this transition. The presence of anti-Z-DNA antibodies also reduced the degree of negative supercoiling required for the formation of Z-DNA in (dG-dC)n sequences inserted into closed circular plasmid DNA. The goat IgG with the more marked effect on the salt-induced transition also had a greater effect in favoring Z-DNA formation in negatively supercoiled plasmids. A shift toward Z-DNA formation was observed in circular dichroism measurements upon antibody binding to poly(dG-dC) X poly(dG-dC) in very low ionic strength solution as well. We propose that the stabilization of Z-DNA by antibody binding in poly(dG-dC) X poly(dG-dC) occurs cooperatively, several antibody molecules binding to a single polymer molecule and stabilizing the entire molecule in Z-DNA through their combined binding energies. The stabilization of Z-DNA by antibody binding in a supercoiled plasmid can be significant, and failure to consider this effect and to choose appropriate conditions for measurement can lead to errors in estimating when Z-DNA will form in response to negative supercoiling.

Animals↗
PubMed1986

Anti-DNA antibodies in autoimmune disorders by ELISA using nylon as the solid phase.

A rapid, simple and highly sensitive enzyme-linked immunosorbent assay (ELISA) utilizing nylon as the solid support is described for the detection of anti-DNA antibodies in autoimmune disorders. The optimal reaction conditions were established with an anti-DNA antibody-positive SLE serum. Fifty-three percent of systemic lupus erythematosus patients, 29 percent of patients with systemic lupus erythematosus with overlapping progressive systemic sclerosis and 10 percent of progressive systemic sclerosis patients were positive for anti-DNA antibodies. The sensitivity of the method was compared with passive hemagglutination and fluorometric assays, the latter using ethidium bromide as intercalating dye. The method described is specific, reproducible and convenient for use in clinical laboratories where large numbers of samples are to be screened for the detection of anti-DNA antibodies. The procedure requires small quantities of antigen or antibody and is, therefore, highly economical.

Antibodies, Antinuclear↗
PubMed1986

Antigenicity, catalytic activity and conformation of Agaricus bisporus tyrosinase: interaction of conformation-directed antibodies with the native and irradiated enzyme.

The antiferromagnetically spin-coupled Cu2+ pair present in the active center of tyrosinase was found to be indispensable for its catalytic function. However, the metal ion did not contribute to the conformational integrity or antigenicity of the enzyme molecule. Irradiation of tyrosinase with 254 nm light resulted in dose dependent, essentially irreversible losses of its catalytic and antigenic functions. The apparent first order rate constants for the two processes were 17.6 X 10(-2) min-1 and 28.1 X 10(-2) min-1, respectively. The approximately 1.6-fold difference between the two rate constants suggests that the sites of antigenic determinants in tyrosinase are distinguishable from the enzymic active site by their higher photosensitivity. Kinetic analysis of the data as to photoinactivation, and the UV induced losses of antigenicity and structural integrity revealed that UV radiation disrupts the short-range noncovalent interactions occurring within the enzyme molecule. The disruption of the noncovalent interactions results in partial unfolding of the tyrosinase structure which in turn leads to the progressive loss of its catalytic activity and antigenicity. The anti-tyrosinase antibodies raised in rabbits were found to be directed against the native conformation of the enzyme. It is speculated that these antibodies might be useful in exploring the tyrosinase conformation and in studying the effects of various factors on the enzyme surface and molecular structure.

Agaricales↗
PubMed1985

Isolation of the first trypsin inhibitor from the genus Aspergillus.

The fungus Aspergillus flavipes was grown on a Czapeck sucrose medium; the biomass so obtained was treated with high concentration of sucrose to release intracellular metabolites. Sephadex G-75 chromatography of the latter yielded a pure protein having anti-trypsin activity in vitro.

Amino Acids↗
PubMed1985

Binding of monoclonal anti-native DNA autoantibodies to DNA of varying size and conformation.

A microchemical assay for phosphorus was applied to the measurement of DNA in immune complexes formed with monoclonal or serum anti-DNA autoantibodies and DNA of varying size and conformation. Two monoclonal antibodies were produced by hybridomas derived from spleen cells of autoimmune MRL-lpr/lpr mice and were purified from culture fluid by affinity chromatography on columns of goat anti-mouse Ig-Sepharose. Double-helical DNA fragments were prepared by brief digestion of calf thymus DNA with micrococcal and S1 nucleases and fractionation on Sepharose 4B; their double-stranded structures was confirmed by measurement of thermal denaturation. Immune complexes were formed with monoclonal or serum antibodies and native DNA or DNA fragments or denatured DNA; the complexes were precipitated with goat anti-mouse IgG and washed, and DNA phosphorus content of the precipitates was measured. With one monoclonal autoantibody (H241), there were discontinuous increases in the amount of DNA that could be bound (and decreases in the antigen concn required for half-maximal binding) as the DNA size increased. There were especially marked increases in binding efficiency as fragment size increased from an average of 100 (range 85-105) to an average of 150 (range 105-170) base pairs, and again between 450 (range 360-620) and 600 (range 425-825) base pairs. A second monoclonal antibody (H143) did not show significant variation in binding with DNA fragments larger than 300 base pairs. With smaller fragments, the amount of DNA bound by H143 was reduced, but the DNA concn required for half-maximal binding was not. Affinities of these monoclonal antibodies were within the spectrum of human systemic lupus erythematosus serum IgG anti-DNA autoantibodies. The dependence of binding on mol. wt is important in the evaluation of these monoclonal antibodies as biochemical reagents and as potential participants in formation of immune complexes in vivo.

Animals↗
PubMed1984

Detection of anti-RNA antibodies in systemic lupus erythematosus by ELISA using nylon as solid support.

A highly sensitive and reproducible enzyme-linked immunosorbent assay (ELISA) for the detection of anti-RNA antibodies is described. The assay procedure involves adsorption of total cellular RNA on nylon beads which could be conveniently stored for a considerable period of time without loss in antigenicity. Sixty-four percent of systemic lupus erythematosus (SLE) sera were positive for anti-RNA antibodies with fluorogenic substrate against 48% with colorigenic substrate.

Antibodies, Antinuclear↗
PubMed1984

Fluorescence studies on the interaction of furocoumarins with DNA in the dark.

The dark interaction of furocoumarins with DNA has been studied by a fluorescence quenching technique. The intrinsic fluorescence of psoralen, 4,5', 8-trimethylpsoralen (TMP) and 8-methoxypsoralen (8-MOP) was quenched to an appreciable extent upon their noncovalent binding to DNA molecule. The analysis of the binding data revealed that TMP binds to DNA with higher efficiency than 8-MOP and psoralen, their apparent Scatchard binding constants being 13.2 X 10(5) M-1, 7.1 X 10(5) M-1, and 12.2 X 10(5) M-1, respectively. The interaction of furocoumarins with DNA was strongly dependent on the conformational stability of DNA in the particular interaction media. The perturbation of DNA structure by changing the ionic environment decreased its interaction with furocoumarins. However, the interaction was facilitated by the presence of an electron-donating moiety in the parent compound, psoralen.

Animals↗