Equilibria of distribution of amino acid side chains, between their dilute aqueous solutions and the vapor phase at 25 degrees C, have been determined by dynamic vapor pressure measurements. After correction to pH 7, the resulting scale of "hydration potentials", or free energies of transfer from the vapor phase to neutral aqueous solution, spans a range of approximately 22 kcal/mol. The side chain of arginine is much more hydrophilic than those of the other common amino acids, with an equilibrium constant of approximately 10(15) for transfer from the vapor phase to neutral aqueous solution. Hydration potentials are more closely correlated with the relative tendencies of the various amino acids to appear at the surface of globular proteins than had been evident from earlier distribution studies on the free amino acids. Both properties are associated with a pronounced bias in the genetic code.

A Lewis basic mixture of quaternary ammonium salts with glycerol has been used to extract excess glycerol from biodiesel formed from the reaction of triglycerides with ethanol in the presence of KOH. The effect of the cation on the partition coefficient of glycerol was determined, together with the time taken for the systems to reach equilibrium. Protocols were also investigated for the separation of glycerol from the quaternary ammonium salt mixtures.

Biphotonic photoionization of frozen aqueous solutions of DNA at 248 nm has been shown by EPR spectroscopy to lead selectively to the guanine cation. In H 2 18 O under these conditions high levels of [ 18 O]-7,8dihydro-8-oxo-2′-deoxyguanosine are produced in a dose-dependent manner, confirming direct formation of this oxidation product by hydration of the guanine cation. Photoionization of defined oligonucleotides did not give rise to significant levels of immediate strand breaks but generated G-specific alkali-labile sites that are readily cleaved by piperidine treatment. Authentic oligonucleotides containing 7,8-dihydro-8-oxo-2′-deoxyguanosine (8-oxodG, 5) sites are slowly cleaved at these sites on treatment with piperidine but at rates inconsistent with this being the source of the alkali-labile site. Photoionization of 7,8-dihydro-8-oxo-2′-deoxyguanosine-containing oligonucleotides demonstrated that this residue is highly susceptible to secondary oxidation and leads to formation of a markedly more alkali-labile lesion. Photoionization of 7,8-dihydro-8-oxo-2′-deoxyguanosine leads to release of 7,8-dihydro-8-oxoguanine suggesting that the alkali-labile site on photoionization of 7,8-dihydro-8-oxo-2′-deoxyguanosinecontaining oligonucleotides is an apurinic site. However, the lack of significant 7,8-dihydro-8-oxoguanine release on photoionization of the parent oligonucleotides rules out secondary oxidation of 7,8-dihydro-8-oxo-2′-deoxyguanosine as the mechanism of formation of alkali-labile sites.

The absolute affinities of amino acid side chains for solvent water closely match their relative distributions between the surface and the interior of native proteins and are associated with a remarkable bias in the genetic code.

The polyamine transport system has a surprisingly broad structural tolerance. Fluorophore-containing polyamine analogues derived from the extracellular pool are located in granular structures within the cytoplasm and not to any great extent in the nuclei of mammalian cells. These observations might be consistent with a mechanism involving receptor-mediated endocytosis, and the granular 'structures' seen might reflect polyamine compartmentalisation within vesicles.