Search PubMed⌕ Search

Biomedical subjects

K T Wang

Publications and source records attributed to K T Wang.

At least 55 records · Page 3Linked to original sources
PubMed1991

Regioselective enzymic deacetylation of octa-O-acetylsucrose: preparation of hepta-O-acetylsucroses.

Deacetylation of octa-O-acetylsucrose (1) with Alcalase or protease N gave the 2,3,4,6,3',4',6'-hepta-acetate (2) as the initial major product with the 2,3,4,6,3',4'-hexa-acetate (3) as the subsequent main product. The 2,3,4,1',3',4',6'-hepta-acetate (5) was obtained from 1 by the action of lipase OF or lipase AP6, and the 2,3,4,6,1',3',6'-(4) and 2,3,4,6,1',3',4'-hepta-acetate (7) by the action of Candida lipase and chymotrypsin, respectively. The 2,3,6,1',3',4',6'-hepta-acetate (6) was formed from 5 by acyl migration.

Acetates↗
PubMed1991

New developments in enzymatic peptide synthesis.

This review article describes new enzymatic methods developed for the efficient and irreversible synthesis of peptides based on native and modified proteases, and for the synthesis of polypeptides containing D- and/or unnatural amino acids. Potential opportunities for future developments in the field based on new enzymes, tailor-made catalytic antibodies, and on the technique of in vitro mutagenesis are also described.

Amides↗
PubMed1991

Application of industrial protease "Alcalase" in peptide synthesis.

An industrial alkaline protease "Alcalase" has been found to be very stable in organic solvents and usable as a catalyst for i) resolution of N-protected amino acids, in both aqueous solution and organic solvent with high yield and optical purity, ii) saponification of Fmoc-peptide esters in high concentration organic solvent iii) kinetically controlled peptide bond formation in ethanol solution, iv) diastereoselective hydrolysis of peptide esters, to prepare optically pure peptides.

Amino Acid Sequence↗
PubMed1990

Analgesic, receptor binding, and peripheral opioid activities of synthetic dermorphin-dynorphin hybrid peptides.

The effects of substituting the enkephalin moiety of dynorphin with the dermorphin sequence were studied on the receptor preference, analgesic, and peripheral opioid potencies by using synthetic dermorphin-dynorphin hybrid peptides as the probe. Replacement of the enkephalin moiety of dynorphin with the dermorphin or dermorphin1-5 sequences caused a remarkable increase in analgesic potency, and a 3-6 fold increase in potency of binding against [3H]-dihydromorphine. The potency of receptor binding against [3H]-EKC was also increased by incorporation of the whole dermorphin sequence into the dynorphin molecule. In the presence of NaCl (100 mM), the effect of enhancing binding against [3H]-EKC due to dermorphin substitution disappeared, suggesting the contribution of opioid mu-receptor. Peripheral opioid activities assayed by various smooth muscle preparations showed that dermorphin incorporation caused a decreased in the potency of inhibition of the contractions of the guinea pig ileum and the rabbit vas deferens, no change in potency on the mouse vas deferens, and a marked increase in the inhibition of the rat vas deferens. Among the peripheral opioid activities only that assayed with the rat vas deferens appears to correlate approximately with the analgesic and the receptor binding activities. Judging from the relative potencies obtained from all assays, it is evident that the N-terminal dermorphin moiety, but not the C-terminal dynorphin fragment, dominates the opioid activity and receptor preference of the hybrid peptide.

Amino Acid Sequence↗
PubMed1990

Side reaction in peptide synthesis. Formation of oxazolidone derivatives.

2-Oxazolidone derivatives formed through an intramolecular reaction in the process of alkaline treatment of urethane-type N-protected peptides of which the N-terminal residues were Ser or Thr having unprotected hydroxyl groups. In oder to avoid this side reaction, the esters of these peptides could be cleaved by enzymatic hydrolyses instead of saponification.

Chemical Phenomena↗
PubMed1989

[Physiological changes of the muscular system in short distance runners].

Fifty high school students of both sexes with an age range of 17 to 19 years were selected for this study. They included 30 males-half regularly did exercise, while half did not and 20 females-half had regularly engaged in sports activities, the other half did not. Before running, on average males had a lower respiratory rate (RR), but a higher blood pressure and serum creatinine kinase (CK) level. In both sexes, students who regularly engaged in sports habits had a lower pulse rate (PR) but higher serum CK. The latter suggested the possibility of sports injury in the males active in sports. After they ran for a distance of 400 meters, there were increased PR, RR, body temperature, skin temperature and systolic pressure; but a decreased diastolic pressure. These physiological signs recovered within the first hour after running, and then were followed by the decrement of blood pressure for two days. The physiological phenomena caused by this kind of anaerobic exercise were more prominent in the groups of students inactive in sports. As for the serum lactate, it rose immediately after running and markedly declined within the first hour. This suggests that short distance running is a typical anaerobic exercise. After their run, serum CK elevated and persisted for two days in the habitual-exercise students, which confirms again the possibility of muscle injury in these students.

Adolescent↗
PubMed1987

Rapid hydrolysis of proteins and peptides by means of microwave technology and its application to amino acid analysis.

A rapid heating method of hydrolysis by the use of microwave oven has been applied to amino acid analysis of proteins and peptides. This convenient method has been compared with the conventional 6 N HCl hydrolysis at 110 degrees for 24 h. The advantages of this new method are its expedition and the accurate and comparable results as compared to the tedious conventional technique. The method provides a rapid processing of multiple samples within minutes instead of days and inexpensive access to the important data of amino acid compositions of proteins by the commonly used microwave oven. The necessary change in the design of hydrolysis vials and the safety precautions accompanying this novel use of microwave acid-digestion method are also described.

Amino Acids↗
PubMed1987

4-Methoxybenzyloxycarbonyl amino acids in solid phase peptide synthesis.

Moz-amino acids were used in solid-phase synthesis of Leu-Ala-Gly-Val and thymosin alpha 1. It was found that the Moz-group can be removed rapidly and completely with 5-10% TFA in CH2Cl2. Some advantages of utilizing Moz-amino acids over Boc-amino acids in solid phase peptide synthesis are demonstrated.

Chromatography, High Pressure Liquid↗
PubMed1983

The modification of alpha-bungarotoxin by digestion with trypsin.

Two modified alpha-bungarotoxins (alpha-BuTX)2 were obtained by trypsin digestion. On mild tryptic digestion, alpha-BuTX could be cleaved at a single site to give the des-tetrapeptide alpha-BuTX, designated as des-(71-74)-alpha-BuTX. Further cleavage at Arg36-Gly37 yielded a double-chained product held together by five disulfides and designated double-chained des-(71-74)-alpha-BuTX. The des-(71-74)-alpha-BuTX had a similar CD spectrum and antigenicity to that of native alpha-BuTX, but had a lower toxicity and neuromuscular-blocking potency. This indicates that the C-terminal tail of alpha-BuTX had some effect on the toxin's biological activities. The double-chained des-(71-74)-alpha-BuTX also retained full antigenicity, but changed moderately in CD spectrum and decreased dramatically in toxicity and neuromuscular-blocking potency. These results suggested that the invariant region at Arg36-Gly37, previously thought to be essential for the neurotoxicity of alpha-BuTX due to its cationic group, might also play a critical role in maintaining the native conformation of the toxin.

Amino Acids↗
PubMed1982

Purification and pharmacological characterization of a cardiotoxin-like protein from Formosan banded krait (Bungarus multicinctus) venom.

By ion exchange chromatography followed by gel filtration, a polypeptide toxin was purified from Formosan banded krait (Bungarus multicinctus) venom. The toxin had a molecular weight of 7000 +/- 300 and showed an amino acid composition characteristic of cardiotoxin from cobra venom. The i.p. LD50 value of the toxin was 2.5 (1.9-3.2) mg per kg mouse. Pharmacological studies showed that the toxin (10 micrograms/ml) induced contracture in chick and mouse skeletal muscles, depolarized the cell membrane of the mouse diaphragm, arrested the contraction of spontaneously beating atria and the electrically driven ventricle strip of the rat, and caused direct hemolysis of guinea-pig erythrocytes. From these chemical and pharmacological characterizations it was concluded that this toxin has characteristics similar to those of cobra venom cardiotoxins.

Amino Acids↗