Ieva R. Politzer

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.

IDENTIFICATION OF PETROLEUM RESIDUE SOURCES AFTER A FIRE AND OIL SPILL

ABSTRACT The evaluation of the environmental impacts resulting from an oil spill and fire at the West Hackberry Strategic Petroleum Reserve Complex was particularly challenging. The fire and spill resulted in two distinctive types of chemical releases into the environment. The spill released a large quantity of Arabian light crude oil into an area that had been exposed to Louisiana sweet crude oil during 40 years of production. The fire produced significant quantities of pyrogenic polycyclic aromatic hydrocarbons that were dispersed over a large area by wind. New methods were developed to identify samples, and consequently the areas, that were affected by these releases. Samples of sediment affected by the oil spill were distinguished from nonaffected samples by comparing the ratios of the alkyl phenanthrenes to the alkyl dibenzothiophenes (C1, C2, and C3) in a gas chromatography–mass spectrometry analysis of the extractable hydrocarbons. These ratios effectively identified affected sediment even when the...

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.