SIMILARITY BETWEEN THE CLOUDING OF NONIONIC SURFACTANTS AND THE DENATURATION OF BIOPOLYMERS, AND THE EFFECT OF ANIONS ON BOTH PHENOMENA - EFFECT OF INORGANIC ADDITIVES ON SOLUTIONS OF NONIONIC SURFACTANTS .8.

The first topic is a study of the similarity between the clouding phen omenon of micellar solutions of nonionic surfactants (NS) and the ther mal denaturation of globular proteins and other native biopolymers. It was prompted by the resemblance between micelles of NS and globular p roteins, which was reported previously. The reversible precipitation o f NS at their cloud point (CP) occurs in a temperature range of congru ent to 1 degrees C. The reversible denaturation/precipitation of biopo lymers spans broader temperature ranges because of the complexity of t heir secondary and tertiary structures The main topic is a comparison of the effect of anions in salting NS in or out and in denaturing or s tabilizing native biopolymers. This extends our study of the analogy b etween protein denaturation and clouding of NS: While all organic prot ein denaturants previously studied salted NS in, many electrolytes sal t NS out and stabilize native biopolymers. According to their effect o n the structure of water, anions either disrupt or enhance the self-as sociation of water molecules via hydrogen bonds. Structure-breaking an ions salt in NS, raising their CP, and denature biopolymers, lowering their denaturation or melting temperature (T-m). Water structure-makin g anions lower the CP of NS and stabilize native biopolymer structures by raising the T-m. (The cations Na+, K+ and NH4+ enhance the structu re of water, salt out NS, and stabilize the native structure of biopol ymers, but their effects on CP and T-m, are comparatively small.) The CP moves in the opposite direction to the T-m because NS, unlike biopo lymers, have an inverse temperature - solubility relation. Linear rela tionships with excellent correlations (r congruent to -0.9) were found between the capacity of anions to shift the CP of NS, and their capac ity to alter the secondary, tertiary and quaternary structures of biop olymers as illustrated by the following examples: the denaturation/ren aturation of BSA in the presence of urea, and of DNA; the rate of form ation of collagen folds in gelatin solutions; shifts in the melting po int of gelatin gels; reduction of enzymatic activity; changes in the p olymerization of globular proteins; dissociation/association between m yosin and actin, and between antigens and antibodies; the disruption o f mitochondria. These quantitative correlations corroborate the analog y between denaturation of biopolymers and clouding of NS. They also ma ke it possible to estimate the capacity of anions to disrupt or stabil ize biopolymer structures from the anions' effect on the CP of NS. Whi le many of the biochemical procedures for assessing denaturation are c omplex and cumbersome, CP measurements are fast, easy, and reproducibl e.