Search PubMed⌕ Search

Biomedical subjects

C C Yang

Publications and source records attributed to C C Yang.

At least 307 records · Page 17Linked to original sources
PubMed1982

Production of deferriferrioxamines B and E from a ferroverdin-producing Streptomyces species.

When Streptomyces sp. strain Wak. A-305 is cultured in iron (III)- or cobalt (II)-containing media, tris(p-vinylphenyl-4-hydroxy-3-nitrosobenzoato-N3, O4)ferrate(II) (ferroverdin) or the analogous tris-cobalt(III) complex, respectively, is produced intracellularly. In contrast, when cultured in transition metal ion-limiting media. Streptomyces sp. strain Wak. A-305 did not produce p-vinylphenyl 4-hydroxy-3-nitrosobenzoate (deferroferroverdin). Instead, deferriferrioxamines B and E, which have been characterized from other streptomycetes, were isolated extracellularly and may act as siderophores in this organism.U

Chlorides↗
PubMed1981

Reversed unfolding-refolding process of cobra neurotoxin.

Circular dichroism and nuclear magnetic resonance spectroscopies have been used to study the unfolding process of cobrotoxin upon addition of fluoro alcohols/or sodium dodecyl sulfate to its aqueous solution. In each final unfolded state, the protein had its disulfide bonds intact. The unfolding process has been found to be reversible in the case of fluoro alcohol/water mixtures, while no such reversibility was found in the case of sodium dodecyl sulfate. However, when hexafluoro-2-propanol is added to the sodium dodecyl sulfate unfolded protein, refolding is induced. The mechanism of unfolding is discussed in terms of the different interactions which govern the protein conformation in solution.

Chemical Phenomena↗
PubMed1981

Crystallographic studies of snake venom proteins from Taiwan cobra (Naja nana atra). Cardiotoxin-analogue III and phospholipase A2.

Orthorhombic crystals of cardiotoxin-analogue III from Taiwan cobra have been grown from 2-methyl-2,4-pentanediol solution. The space group is P222 with 2 molecules/asymmetric unit. Several different crystal forms of phospholipase A2 from Taiwan cobra have been produced with or without Ca2+ ion. One of them, grown from 30 mM sodium cacodylate buffer (pH 6 to 7) and 30% 2-methyl-2,4-pentanediol with 20 mg/ml of protein, diffracts well to 2 A resolution. It crystallizes in space group P3112 or P3212 with 2 molecules/asymmetric unit, but it can be related to a quasi-cubic space group P213.

Animals↗
PubMed1981

Lack of correlation between anticoagulant activity and phospholipid hydrolysis by snake venom phospholipases A2.

The anticoagulant effects and the simultaneous plasma phospholipid hydrolysis induced by three purified phospholipases obtained from snake venoms, i.e., the basic, relatively toxic N. nigricollis, the neutral, relatively nontoxic H. haemachatus, and the acidic, relatively nontoxic N. n. atra, have been compared. The N. nigricollis phospholipase has a very strong anticoagulant effect at concentrations which induce relatively low levels of phospholipid hydrolysis in plasma. The H. haemachatus and N. n. atra phospholipases become anticoagulant only at high concentrations, and the associated phospholipid hydrolysis is also very high. It is concluded that, while all phospholipases are likely to inhibit coagulation if used in amounts sufficiently large to deplete plasma of phospholipids, strongly active phospholipases, such as N. nigricollis, interfere nonenzymatically with the clotting process before any appreciable phospholipid hydrolysis is reached.

Animals↗
PubMed1981

Mode of antibiotic action of 4-hydroxy-3-nitrosobenzaldehyde from Streptomyces viridans.

The free ligand, deferroviridomycin A, and its iron(II) complex, viridomycin A, were detected in culture supernatant fluids of Streptomyces viridans 1671 and were structurally characterized as 4-hydroxy-3-nitrosobenzaldehyde and tris(4-hydroxy-3-nitrosobenzaldehydato-N3,O4)ferrate(II), respectively. We investigated the antibiotic activity of the above compounds and of the chemically synthesized bis copper(II), tris cobalt(III), and tris nickel(II) complexes against Escherichia coli NIHJ, Salmonella typhimurium LT-2Z, Staphylococcus aureus 209P, Streptococcus faecium 10541, and Bacillus cereus, T. The free ligand and its kinetically labile copper(II) and nickel(II) complexes displayed activity against all of the above organisms, whereas the kinetically inert iron(II) and cobalt(III) complexes displayed activity only against S. aureus and B. cereus. The antibiotic activity of the substitutionally labile metal complexes was attributed to dissociation of the free ligand. The mode of antibiotic action of the free ligand against E. coli appears to be interference with the structural and functional integrity of the cell membrane.

Bacillus cereus↗
PubMed1980

Chemical modification of the histidine residue in basic phospholipase A2 from the venom of Naja nigricollis.

Phospholipase A2 from Naja nigricollis venom was separated into three fractions by chromatography on a column of CM-Sephadex C-25. The pI values of fractions CMS-5, CMS-6 and CMS-9 were determined to be 7.6, 8.3 and 10.6, respectively. Fraction CMS-9 was further purified on a DEAE-Sephacel column and the homogeneity was verified. The specific activity of CMS-9 was found to be 1300 units per mg and lethal toxicity 0.3 mg per kg mouse. The most basic and toxic fraction, CMS-9, was subjected to chemical modification with p-bromophenzcyl bromide. The enzyme lost both the enzyme activity and lethal toxicity, however, the antigenicity remained unchanged. Although both 8-anilinonaphthalenesulfonate and Ca2+ showed pronounced protection on the inactivation process, the mechanism of 8-anilinonaphthalene-sulfonate protection is different from that of Ca2+. Amino acid analysis showed that only one (His-47) out of three histidine residues was modified. Although both native and His-modified CMS-9 were perturbed by the presence of Ca2+, the modified enzyme lost the characteristic tryptophan blue shift suggesting that the modified enzyme is unable to exert a charge effect upon Ca2+ binding in the vicinity of the tryptophan group. Scatchard plots revealed only one type of binding sites for 8-anilinonaphthalenesulfonate in the presence of Ca2+. On the other hand, the modified enzyme lost the ability to bind 8-anilinonaphthalene. It is suggested tentatively that the hydrophobic pocket in which 8-anilinonaphthalenesulfonate is bound may be the site of the enzyme that interacts with phospholipid.

Acetophenones↗
PubMed1978

Laser Raman studies on cobrotoxin.

Laser Raman spectra of cobrotoxin under various conditions have been obtained. Comparison of the spectra of native cobrotoxin in lyophilized form and in aqueous solution indicates that the secondary structures of cobrotoxin are not significantly affected by the removal of the aqueous solvent. On going from the native to the partially reduced and the completely reduced, carboxy-methylated forms, characteristic peaks of the C-S-S-C and tyrosine ring in the region of 500--900 cm-1 showed definite changes in structure. The partially reduced form gave two peaks at 502 and 524 cm-1, suggesting difference in the conformation of the remaining disulfide bonds. As indicated by the present work, the conformation of the main chain of cobrotoxin in the native unperturbed state, in the partially reduced and in the completely reduced forms are the coexistence of beta-pleated sheet with random-coil structure, predominantly random coil, and predominantly random coil with the existence of an alpha-helix type structure, respectively. The effect of pH on the conformation of cobrotoxin in solution appeared to give rise to the change of the local structure of two aromatic residues common to all snake neurotoxins.

Animals↗