Intramolecular interactions in aminoacyl cyclic-3',5'-nucleotides.

Polymerization of amino-acid acyl cyclic-3',5'-nucleotides is postulated to be the origin of RNA and associated protein in prebiotic molecular evolution. The enthalpy change in the intramolecular interaction between the nucleotide base and the amino-acid side chain determines the stability of the particular complex, resulting in a preferred association (or coding) of a base for a particular amino acid. The compounds studied were glycine acyl cyclic-3',5'-guanylate where the strong hydrogen bond between protonated glycine and guanine N7 gives an enthalpy change of -0.

A plausible prebiotic synthesis of pyridoxal phosphate: vitamin B6 - a computational study.

A set of chemical reactions is proposed to account for the formation of pyridoxal phosphate, Vitamin B6, from a primeval atmosphere composed of cyanoacetylene, diacetylene, carbon monoxide, hydrogen, water, and a phosphoric acid. The reactions have been shown to be feasible from the overall enthalpy changes in the ZKE approximation at the HF and MP2/6-31G* level.

Possible origin for porphin derivatives in prebiotic chemistry--a computational study.

A set of chemical reactions is postulated to account for the formation of the macrocyclic porphin structure, basic to the pyrrole derivatives chlorophyll, protoporphyrin, heme and bilirubin, important in photosynthesis, respiration and digestion. A set of equations is given for the prebiotic synthesis of porphin derivatives from the simple molecules; cyanoacetylene, diacetylene, carbon monoxide and ammonia that have been detected in space. A number of isomers of hydrogenated porphin arise which may lose hydrogen to give ultimately porphin and its dehydrogenated derivative.

The reactions of methanimine and cyanogen with carbon monoxide in prebiotic molecular evolution on earth.

A primeval atmosphere is proposed containing simple molecules such as formaldehyde, ammonia, carbon monoxide, cyanogen and hydrogen cyanide, which have been detected in space. Chemical reactions are described for the formation of aziridine-2-one and di-azirine-3-one derivatives as potential precursors for the original synthesis of amino-acids, proteins, pyrimidines, purines, nicotinamide and flavin. The reactions have been shown to be kinetically feasible from the overall enthalpy changes in the ZKE approximation at the MP2/6-31G* level.

Impact of microenvironmental nitrogen dioxide concentrations on personal exposures in Australia.

Indoor and outdoor NO2 concentrations were measured and compared with simultaneously measured personal exposures of 57 office workers in Brisbane, Australia. House characteristics and activity patterns were used to determine the impacts of these factors on personal exposure. Indoor NO2 levels and the presence of a gas range in the home were significantly associated with personal exposure.