Biomedical subjects

S A Yazynin

Publications and source records attributed to S A Yazynin.

5 recordsLinked to original sources

PubMed1998

Ribonuclease-charged vector for facile direct cloning with positive selection.

Plasmid vectors for positive selection of cloned inserts in Escherichia coli were devised, based on an expression plasmid (pMT416) for the bacterial ribonuclease barnase. In addition to the barnase gene under control of a synthetic tac promoter, these plasmids carry the gene for the barnase inhibitor, barstar, the constitutive expression of which protects the bacterium from the detrimental effects of moderate barnase production. Full expression of the barnase gene overcomes protection by barstar and becomes lethal. Having a unique SmaI/XmaI site in the barnase structural gene, pMT416 itself can be used as a selective vector: uncut or religated pMT416 will preclude growth while plasmids with inserts in the barnase gene will allow the cells to survive. The entire pUC polylinker was inserted into the barnase gene in place of the Val-36 codon. This insert of nineteen largely hydrophilic amino acids does not prevent the lethal effect of full expression of the gene. The resulting plasmid, pMT440, is a generally useful selective cloning vector representing the "kill-the-rest" approach.

Amino Acid Sequence↗

PubMed1996

Recombinant barnase as a label in ELISA.

Recombinant barnase was proposed as a label in the enzyme-linked immunosorbent assay (ELISA). Barnase-conjugated pig transferrin was prepared by the periodate oxidation procedure. Solid-phase bound barnase activity was determined from the change in RNA-ethidium bromide complex fluorescence upon RNA hydrolysis. The sensitivity of transferrin-barnase conjugate determination in ELISA was no less than 5 ng per well. The conjugate was applied in competition ELISA for free transferrin determination.

Animals↗

PubMed1996

A plasmid vector with positive selection and directional cloning based on a conditionally lethal gene.

A plasmid vector with a multiple cloning site (MCS) for positive selection of cloned inserts in Escherichia coli (Ec) has been devised, based on the expression plasmid (pMT416) for the bacterial ribonuclease barnase (Barn). The host is protected from the lethal effect of moderate expression of barn by expression of the gene bars, encoding its inhibitor, barstar (Bars), placed on the same plasmid. Full expression, however, is lethal. Induction is also lethal with the derived plasmid, pMT440, which has the pUC19 MCS inserted into barn. Under inducing conditions, transformation by the vector is lethal unless the product of the modified barn is inactivated by insertion of cloned DNA fragments into the MCS. Plasmid pMT440 is, therefore, a generally useful selective cloning vector not requiring any special strain of Ec.

Amino Acid Sequence↗

PubMed1994

Group-selective immunoassay.

A new solid-phase immunoassay technique has been applied for anti-digoxin monoclonal antibodies (Mabs) detection. At the first assay step, anti-digoxin Mabs (IgG1, Kaff = 9.2 x 10(9) M-1) were bound to a specially prepared immunosorbent, the microtiter plates coated with digoxin-human serum albumin conjugate (Dig-HSA), in which free amino groups were protected by a glutaraldehyde cross-linking modification. The modification did not essentially influence the antibody-binding capacity of the immunosorbent. After antigen-antibody reaction, free amino groups were located only on the anti-digoxin Mabs, bound to chemically modified immunosorbent. At the second assay step, free amino groups of anti-digoxin Mabs were biotinylated by N-hydroxysuccinimide-biotin ester. Then the biotin residues were detected by the streptavidin-peroxidase conjugate. The method does not require second labeled antibodies and may be used for anti-hapten hybridoma screening.

Antibodies, Monoclonal↗

PubMed1992

Fast filtration enzyme immunoassay for haptens.

An immunometric method for determination of hapten concentration in fluids has been developed. High-affinity hapten-specific enzyme-labeled monoclonal antibodies are mixed with a sample containing hapten, then the mixture is filtered through a membrane with immobilized hapten. The level of enzyme activity retained by the membrane is inversely proportional to the concentration of hapten in a sample. The assay has been developed for theophylline, digoxin and phenobarbital. The coefficient of variation is less than 5% and the test takes about 2 min.

Animals↗