Cyanamide mediated syntheses under plausible primitive earth conditions. II. The polymerization of deoxythymidine 5'-triphosphate

When an aqueous solution (pH 7.0) of 3H deoxythymidine 5'-triphosphate, deoxythymidine 5'-phosphate, 4-amino-5-imidazolecarboxamide, cyanamide and ammonium chloride was dried and heated at 60 degrees C for 18 h, oligomers were obtained in a yield of approximately 80%. After the chemical degradation of any pyrophosphate bonds present in these oligomers, linear polynucleotides of up to 7-8 units in length were isolated by DEAE cellulose column chromatography and identified by enzymatic digestion procedures. The di- and trinucleotide fractions were degraded 87% and 100% by snake venom phosphodiesterase and 39% and 9% by spleen phosphodiesterase. This synthesis of deoxythymidine oligonucleotides was conducted under potentially prebiotic conditions and may offer a possible method for the synthesis of deoxyoligonucleotides on the primitive Earth.

E.s.r. of spin-trapped radicals in aqueous solutions of amino acids. Reactions of the hydrated electron

The reactions of hydrated electrons (eaq-) with amino acids were investigated by the spin-trapping method and by electron spin resonance. Tertiary nitrosobutane was used as a spin-trap to stabilize the short-lived radicals. Hydrated electrons were produced by gamma-radiolysis of de-aerated aqueous solutions of amino acids in the presence of sodium formate or tertiary butanol to scavenge OH. Radicals produced by reductive deamination of 19 amino acids were identified. Radicals formed by scission of the CH3-S- and -S-CH2- bonds of methionine as well as by deamination were observed. In the case of phenylalanine the radical formed by electron addition followed by proton transfer was identified. The reaction of proline and of hydroxyproline with eaq- resulted in the opening of the cyclic structure.

E.s.r. of spin-trapped radicals in aqueous solutions of amino acids. Reactions of the hydroxyl radical

The radicals produced by reactions of hydroxyl radicals with amino acids in aqueous solutions have been investigated. Hydroxyl radicals were formed by U.V.-photolysis of hydrogen peroxide and the short-lived amino acid radicals were spin-trapped by tert-nitrosobutane and identified by electron spin resonance spectroscopy. Nineteen amino acids were studied, and several radicals were identified which have not been observed previously by other methods. Only side-chain radicals were identified for alanine, threonine, aspartic acid, asparagine, lysine, phenylalanine, tyrosine, proline and hydroxyproline; whereas for glycine the C(2) carbon radical was spin-trapped. Both C(2) carbon radicals and side-chain radicals were assigned to valine, leucine, isoleucine, serine, glutamic acid, glutamine, arginine and methionine.

Mechanism of action of miconazole: labilization of rat liver lysosomes in vitro by miconazole

Miconazole, a potent antifungal agent, labilizes rat liver lysosomes. Its labilizing effect is followed by measuring the release of lysosomal hydrolases, namely, acid phosphatase, beta-glucuronidase, and arylsulfatase A. The effect of miconazole is concentration dependent in the range of 10(-5) to 1.2 x 10(-4) M. However, at higher concentrations, miconazole inhibits enzyme release but does not inhibit enzyme activities per se. The effect of miconazole depends on the drug/lysosome ratio and is influenced by the pH of the incubation media, being minimal at alkaline pH. Membrane-active drugs such as nystatin, 2-phenethyl-alcohol, hexachlorophene, and digitonin have been compared with miconazole for their lysosome-labilizing action. The effect of miconazole on the lysosomal membrane is confirmed by a decrease in turbidity of the lysosomal suspension.