Purification, general procedures nucleic acids

Naturally occurring bacterial endotoxins contain the lipid, carbohydrate, and protein makeup of the outer cell membrane of GNB (Fig. 1). However, most of the commercial endotoxin preparations have been purified by various extraction procedures and are generally free of nucleic acids, proteins, phospholipids, and other bacterial cell components. The primary chemical configuration that remains after purification is apolysaccharide structure that is covalently bound to a lipid component called Lipid A. Based on its chemical nature, which is common to various bacterial families, this substance is referred to as lipopolysaccharide (LPS). Although the terms endotoxin and LPS are often used interchangeably, most reference endotoxin standards are purified preparations that are more correctly described as LPS. 

Analytical procedures for foods are generally based on extraction with purified solvents following saponification with alcoholic potash. Purification of the extracts by chromatography on column or plates is followed by analysis of the purified extract using TLC, GLC or HPLC. Spectrophotometric or spectrofluorimetric methods may be used for quantitation of the hydrocarbons a collaborative study of a spectrophotometric method showed it to be applicable at the 2 fig/kg level. HPLC techniques using spectrofluorimetric detection have been described for which improved levels of detection are claimed. Benzo(a)pyrene produces substitution products with nucleic acids. Hydrocarbon deoxyribonucleoside adducts may be isolated from DNA by gel permeation chromatography, and the formation of hydrocarbon epoxides by mammalian enzyme reaction has also been demonstrated . The limit of detection of spectrophotometric and fluorimetric methods has been improved by three orders of magnitude by the use of laser-induced fluorescence procedures for the... 

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