抄録
The specificity of endotoxin (lipopolysaccharide, LPS) in the carbocyanine dye reaction was investigated, and then a stoichiometric study of the dye-LPS interaction was conducted with attention to the relationship of biological activities of LPS to the reactivity with the dye. Absorption maxima of some bacterial components in the dye reaction were as follows; LPS from both Escherichia coli and Pseudomonas aeruginosa and lipid A from E. coli LPS, 465nm; Shigella flexneri LPS, 460nm; Salmonella minnesota R595 glycolipid, 470nm; polysaccharide from E. coli LPS, 650nm; yeast RNA, 620nm: streptococcal M protein and pyrogenic exotoxin, 610nm; and free fatty acids, 445-450nm. The absorbance at 465nm was increased approximately threefold by sonicating LPS for 1-3min, which roughly paralleled the decrease in turbidity of the LPS aqueous solution. The Limulus amoebocyte lysate (LAL) gelation activity of LPS increased 10-fold when LPS was sonicated for 0.5-5min, but it decreased to the control level after further treatment. This decrease, however, was overcome by sonication in the presence of 5mmol of L-ascorbic acid used as an antioxidant. The LAL gelation activity of LPS was inactivated in parallel with an increase in the ratio (w/w) of dye to LPS from 1.73 to 6.90 in the dye-LPS mixture. Pyrogenicity of LPS was also clearly inactivated when the ratio was over 1.73. The ratios of the height of the β band at 465nm (dye-LPS complex) to that of the α band at 510nm (free dye) were increased by sonicating LPS, indicating that the binding character, or stacking tendency, was increased by sonicating LPS.
