Biomedical subjects
Publications and source records attributed to R L Hamill.
Narasin is a new polyether antibiotic produced by a strain of Streptomyces aureofaciens. It is purified by organic solvent extraction and silica gel chromatography. Narasin is active in vitro against gram-positive bacteria, anaerobic bacteria, and fungi and is effective in protecting chickens from coccidial infections.
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Using electron impact and field desorption mass spectrometry, structures are proposed for narasin and a related ionophore, A28086B, derived from fermentation. The ionic fragmentation of these compounds and their derivatives is discussed and compared with that of salinomycin, whose structure has been determined by X-ray diffraction.
A new antibiotic, designated A30641, having in vitro activity against Gram-positive bacteria and fungi has been isolated from a strain of Aspergillus tamarii. Chemical and physical characterization indicate that it is a member of the class of antibiotics containing the epidithiodiketopiperazine moiety.
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A novel group of antibiotics, comprising microbiologically-active structurally-related factors A25822A, B, D, H, L, M and N, produced by culturing Geotrichum flavo-brunneum NRRL 3862 under submerged aerobic fermentation conditions was isolated by extraction. The individual factors were separated and purified by chromatography and crystallization. The major factor, A25822B, a 15-aza-24-methylene-D-homocholestadiene is a white crystalline compound, C25H45NO. The antibiotics are highly active against fungi and marginally active against bacteria.
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The biosynthesis of monensin by Streptomyces cinnamonensis was studied by using (14)C-labeled glucose, acetate, propionate, butyrate, and methionine. The results indicated that the antibiotic is synthesized from five acetate, seven propionate, and one butyrate molecules. The o-methyl group of monensin is derived from methionine, whereas the terminal hydroxymethyl group is incorporated from acetate.
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