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1.
Solution-phase secondary-ion mass spectrometry of protonated amino acids.
Pettit, G R; Cragg, G M; Holzapfel, C W; Tuinman, A A; Gieschen, D P.
Anal Biochem ; 162(1): 236-41, 1987 Apr.
Article in English | MEDLINE | ID: mdl-3037939

ABSTRACT

Although sulfolane proved unexpectedly to be a poor solvent for solution-phase secondary-ion mass spectrometry of underivatized amino acids in the presence of thallium(I) salts, glycerol was somewhat more effective. Also, the addition of trifluoromethanesulfonic acid proved more effective than addition of the metal in generating molecular ion complexes. A convenient and reliable method for rapidly determining amino acid molecular ions is based on these observations.


Subject(s)
Amino Acids/analysis , Glycerol , Mass Spectrometry/methods , Protons , Salts , Solutions
2.
A study of the mutagenicity of irradiated sugar solutions: implications for the radiation preservation of subtropical fruits.
Niemand, J G; den Drijver, L; Pretorius, C J; Holzapfel, C W; van der Linde, H J.
J Agric Food Chem ; 31(5): 1016-20, 1983.
Article in English | MEDLINE | ID: mdl-6630740

Subject(s)
Dietary Carbohydrates/radiation effects , Food Irradiation/adverse effects , Mutagens , Fruit , Glucose/genetics , Ketoses/pharmacology , Mutagenicity Tests , Salmonella/drug effects
3.
The role of essential histidines in the mechanism of catalysis of the flavoenzyme, beta-cyclopiazonate oxidocyclase.
Steenkamp, D J; Schabort, J C; Holzapfel, C W; Ferreira, N P.
Biochim Biophys Acta ; 358(1): 126-43, 1974 Jul 17.
Article in English | MEDLINE | ID: mdl-4855062

Subject(s)
Histidine , Oxidoreductases , Binding Sites , Enzyme Activation , Flavoproteins , Formates/pharmacology , Heterocyclic Compounds , Hydrogen-Ion Concentration , Hydroxylamines/pharmacology , Indoles , Isoenzymes , Oxidoreductases/antagonists & inhibitors , Oxygen , Pyrroles , Quinones , Spectrophotometry , Temperature , Thermodynamics , Tryptamines , Tryptophan
4.
-cyclopiazonate oxidocyclase from Penicillium cyclopium. I. Assay methods, isolation and purification.
Schabort, J C; Wilkens, D C; Holzapfel, C W; Potgieter, D J; Neitz, A W.
Biochim Biophys Acta ; 250(2): 311-28, 1971 Nov 13.
Article in English | MEDLINE | ID: mdl-5143339

Subject(s)
Oxidoreductases/isolation & purification , Penicillium/enzymology , Ammonium Sulfate , Cell Fractionation , Chromatography, DEAE-Cellulose , Chromatography, Gel , Chromatography, Ion Exchange , Chromatography, Paper , Colorimetry , Electrophoresis , Heterocyclic Compounds , Hydrogen-Ion Concentration , Isoenzymes/isolation & purification , Mass Spectrometry , Methods , Molecular Weight , Mycotoxins , Oxidoreductases/analysis , Spectrophotometry , Ultracentrifugation , Ultraviolet Rays
5.
The isolation and structure of two new indole derivatives from Penicillium cyclopium westling.
Holzapfel, C W; Hutchison, R D; Wilkins, D C.
Tetrahedron ; 26(22): 5239-46, 1970 Nov.
Article in English | MEDLINE | ID: mdl-5499899

Subject(s)
Chemical Phenomena , Chemistry
6.
The isolation and structure of cyclopiazonic acid, a toxic metabolite of Penicillium cyclopium Westling.
Holzapfel, C W.
Tetrahedron ; 24(5): 2101-19, 1968 Mar.
Article in English | MEDLINE | ID: mdl-5636916

Subject(s)
Mycotoxins , Penicillium/metabolism , Chemical Phenomena , Chemistry , Heterocyclic Compounds , Indoles
7.
The synthesis of ochratoxins A and B metabolites of Aspergillus ochraceus Wilh.
Steyn, P S; Holzapfel, C W.
Tetrahedron ; 23(11): 4449-61, 1967 Nov.
Article in English | MEDLINE | ID: mdl-6077765

Subject(s)
Mycotoxins/chemical synthesis , Aspergillus/metabolism , Chemical Phenomena , Chemistry , Coumarins , Phenols
8.
The toxicity and chemical assay of sterigmatocystin, a carcinogenic mycotoxin, and its isolation from two new fungal sources.
Holzapfel, C W; Purchase, I F; Steyn, P S; Gouws, L.
S Afr Med J ; 40(45): 1100-1, 1966 Dec 17.
Article in English | MEDLINE | ID: mdl-6006093

Subject(s)
Carcinogens/analysis , Carcinogens/toxicity , Mycotoxins/analysis , Mycotoxins/toxicity , Animals , Aspergillus , Female , Injections, Intraperitoneal , Male , Mitosporic Fungi , Rats
9.
Isolation and structure of aflatoxins M1 and M2.
Holzapfel, C W; Steyn, P S; Purchase, I F.
Tetrahedron Lett ; 25: 2799-803, 1966 Jun.
Article in English | MEDLINE | ID: mdl-5962836

Subject(s)
Aflatoxins/urine , Animals , Chromatography, Thin Layer , Magnetic Resonance Spectroscopy , Sheep
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