G.W. Griffin

Singlet oxygen and biological systems

Abstract Singlet oxygen is receiving increasing attention as a reactive species in many chemical and biological systems. It can be generated easily by microwave discharge, chemically or by photosensitized irradiation and also is found to be a common reactive atmospheric pollutant generated by solar radiation. Singlet oxygen reacts with a host of materials which are unaffected by “normal” oxygen. From a biological standpoint, there is strong evidence that living systems have mechanisms for the protection of molecules such as lipids and nucleic acids which would otherwise be damaged by exogenous singlet oxygen. Interestingly, other constituents such as chlorophyll and riboflavin found in living systems, are in turn excellent singlet oxygen sensitizers. Furthermore, there are indications that living systems may produce singlet oxygen internally, for example in the enzyme peroxidase-catalase system. The presence of singlet oxygen in biological systems has led to new theories on carcinogenesis. In view of these biological implications, a selective survey has been made of the current literature on singlet oxygen concentrating on the involvement of this species in the aforementioned processes. Examples from the chemical literature are presented which illustrate the scope of singlet oxygen reactions and/or serve as models for biochemical processes.

Enhancement of Ultraviolet Detectability of Fatty Acids for Purposes of Liquid Chromatographic-Mass Spectrometric Analyses

Abstract A technique for benzyl derivatization of fatty acids which results in enhanced ultraviolet absorption with a concomittant increase in sensitivity in liquid chromatographic (LC) separations has been developed. Benzylation prior to liquid chromatographic separation also provides a uniform enhancement of response for fatty acids which permits direct relative quantization without acquisition of additional calibration data. After removal of excess solvent from eluted compounds mass spectra were determined using a direct probe which confirmed the benzyl ester structures. A discussion of spectral data and the advantages of using mass spectrometry as an ancillary tool to liquid chromatography is also discussed.

Dye-sensitized photooxidation of phenanthrene☆

Abstract The dye-sensitized photooxidation of phenanthrene has been studied in a two-phase system employing n -hexane and water. Rose bengal was used as a sensitizer. A number of volatile oxidation products are observed and characterized by GC-MS-COM methods. The data suggest that one oxidation route involves the conversion of phenanthrene to 9,10-epoxy-9,10-dihydrophenanthrene which is related to the potentially carcinogenic arene oxides of more highly condensed polynuclear hydrocarbons. These results may have significance in connection with the enhancement of aberrant effects on biological systems produced by polynuclear hydrocarbons upon exposure to light.

Reactions of Singlet Oxygen with Pine Pollen

Exposure of pine pollen to single oxygen, generated in an aqueous environment, resulted in a decrease in the relative quantities of unsaturated fatty acids that could be recovered by solvent extraction of surface and near surface pollen lipids. The involvement of excited oxygen was confirmed by substitution of deuterium oxide for water, which led to a twofold greater decrease in the unsaturated acids. The potential environmental and biomedical implications of these observations are discussed in terms of this model system.

Mass spectrometric and ultraviolet spectral studies on trimethylenecyciopropane prepared from independent sources—A confirmation of structure

Abstract Evidence is presented which demonstrates conclusively that trimethylene cyclo propane is a common product from three independent precursors. The mass spectral data are compared and contrasted with the data for benzene and points of contention in the literature are discussed with respect to infrared and ultraviolet data previously reported.

Influence of Methyl Substitution on mass Spectra of Diphenylmethanes: Analytical Applications

Abstract In connection with other studies we synthesized and obtained low resolution electron impact spectra of the 2,2′-, 2,3′-, 2,4′-, 3,3′-, 3,4′-, and 4,4′-dimethyl substituted diphenylmethanes. The results suggest that caution should be exercised in using the characteristic even mass rearrangement fragment (m/e = 104) produced by the “ortho-effect” as the only method to distinguish between ortho and non-ortho methyl substituted diphenyl-methanes. The relationship between the stability of the diphenylmethane isomers and the substitution patterns at the meta and para positions does not parallel that observed for the dimethyl substituted biphenyls.