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Biomedical subjects

S Kim

Publications and source records attributed to S Kim.

At least 1,477 records · Page 82Linked to original sources
PubMed1976

Labile protein-methyl ester: comparison between chemically and enzymatically synthesized.

The rate of hydrolysis of protein-methyl ester, the enzymatic product of S-adenosylmethionine: protein-carboxyl methyltransferase (EC.2.1.1.24) acting on oxidized ribonuclease, was measured at pH 7.1 and 8.6 at 37 degrees C. The half-life of the hydrolysis of the ester is 25 min at pH 7.1, and 4 min at 8.6. The rate of hydrolysis of the enzymatically formed esters at pH 7.0, in 0.1 M phosphate buffer, was about 25 times faster than that of esters formed chemically by reaction with methanol in HCl. The lability of the enzymatically synthesized protein-methyl ester suggests that the esterification is specific to sites such that ionization of neighboring amino acid side chains enhances the rate of the hydrolysis.

Aspartic Acid↗
PubMed1976

A comparison of kinetic parameters of polypeptide substrates for protein methylase II.

Kinetic properties of protein methylase II (S-adenosymethionine:protein O-methyltransferase, EC 2.1.1.24) which methylates (esterifies) the free carboxyl side chains of amino acids in proteins was studied using various polypeptides as methyl acceptor substrates. Bovine pancreatic ribonuclease, a model substrate for the enzyme, was subjected to specific cleavage by cyanogen bromide, trypsin, and performic acid oxidation. Several polypeptide fragments derived were then separated by molecular sieve chromatography on a column of Sephadex G-25. The method was found to be very simple and gave good yields. Km values for these polypeptides as well as a few other protein substrates were determined. While Km values for the isolated peptides range generally between 4.8 and 0.7 X 10-3 M, those of native bovine panreatic ribonuclease, luteinizing hormone, and follicle-stimulating hormone were determined to be 4.0 X 10-4, 5.0 X 10-5, and 0.77 X 10-5, respectively. Sites of enzymatic methylation of the native ribonuclease were also investigated. Although polypeptides derived from the C-terminal and N-terminal regions of the molecule were found to accept methyl groups, they were unable to under go enzymatic methylation when native molecule was used as the substrate indicating that within the native ribonuclease these regions are in a conformation which do not allow them to be methylated by protein methylase II under the present assay conditions.

Binding Sites↗
PubMed1976

Comparison of ejection fraction calculated by nine different volume calculation methods.

Single plane right anterior oblinque ventriculography was performed on 25 patients with normal left ventricular contraction and on 25 with left ventricular akinesia or dyskinesia. The value of the left ventricular ejection fraction (EF) was calculated by 9 different methods, including a new one utilizing the mathematical model of a cone. All methods tested were appropriate for inter-group comparisons of EF. For inter-individual comparisons, however, only those methods described by Davila, Chapman, Dodge, Beranek, and our new method, are appropriate.

Angiocardiography↗
PubMed1976

The effect of valium on myocardial blood flow.

The effect of Valium on coronary blood flow was studied. In 18 patients undergoing coronary angiography, total and regional myocardial blood flow was determined by the 133Xe wash-out technique. A total of 39 pre- and 39 post-Valium injection wash-out curves were constructed. Results indicate (99% confidence) that intravenous Valium injection (0.1 mg/kg body weight) decreases myocardial blood flow 12--15%.

Angiography↗
PubMed1976

A device to measure roentgenographic structures.

A simple device and a nomogram are presented to permit rapid, accurate measurement of structures shown on roentgenograms. The arrangement is designed specifically for measurement of coronary vessels, but it can be adapted to other structures.

Angiography↗
PubMed1976

[On the development of oral preparations of the combination sulfamoxole/trimethoprim (CN 3123) (author's transl)].

Within the broad range of activities in pharmaceutical research, the technological development and analytical evaluation of a new drug formulation represent only one step. The pharmaceutical development of three oral formulations of a combination product containing N1-(4,5-dimethyl-2-oxazolyl)-sulfanilamide (sulfamoxole) and 2,4-diamino-5-(3,4,5-trimethoxy-benzyl)-pyrimidine (trimethoprim) in a 5:1 ratio (investigational drug CN 3123; Nevin; Supristol), which was based on the physico-chemical characteristics of the 2 active substances, is presented. The various chemical and physical tests conducted with the drug formulations are described. The pharmaceutical or in-vitro availabilities (dissolution rate) of the active ingredients were determined by way of release-rate profiles, both of the active ingredients alone and in their final formulations. Also presented are the results of plasma level determinations following oral administration of film-coated tablets and a suspension. Finally, preliminary results of extensive stability tests with the three drug formulations are discussed.

Administration, Oral↗
PubMed1975

Studies on the kinetic mechanism of S-adenosylmethionine: protein O-methyltransferase of calf thymus.

Initial velocity studies have been carried out on protein methylase II (S-adenosyl-L-methionine:protein O-methyltransferase, EC 2.1.1.24) purified from calf thymus, using bovine pancreatic ribonuclease as the protein substrate. Initial velocity patterns converging at a point on or near the extended abcissa were obtained with either ribonuclease or S-adenosyl-L-methionine as the variable substrate. Inhibition by the product S-adenosyl-L-homocysteine was linear competitive against both S-adenysyl-L-methionine and ribonuclease, the apparent inhibition constants being dependent on the concentration of the nonvaried substrate. Adenosine was an inhibitor of the reaction, the inhibition being linear competitive against both S-adenosyl-L-methionine (Ki/1.2 times 10-3 mol/1.) and ribonuclease (Ki/4.6 times 10-3 mol/1.). These results are consistent with a random mechanism for the protein methylase II reaction in which the rate-limiting step may be the interconversion of the ternary complexes and all other steps may be in equilibrium. The limiting Michaelis constants for S-adenosyl-L-methionine and ribonuclease are 0.87 times 10-6 and 2.86 times 10-4 mol/1., respectively. The dissociation constants of S-adenosyl-L-homocysteine for its reaction with the free enzyme was 1.03 times 10-6 mol/1. Thus it has about equal affinity for calf thymus protein methylase II as S-adenosyl-L-methionine.

Animals↗