Abstract.-Chaotropic ions (those ions which favor the transfer of apolar groups to water) provide a highly effective means for the resolution of membranes and multicomponent enzymes and for increasing the water solubility of particulate proteins and nonelectrolytes. The action of chaotropic agents is related to their effect on the structure and lipophilicity of water.The meager water solubility of particulate proteins and many biological compounds such as hemes, purines and pyrimidines, nucleosides, certain vitamins, and various structures of pharmacological interest has posed considerable difficulty in the study of their chemical and biological properties. Also, because of the predominance of hydrophobic bonds in membranes and multicomponent enzymes, the stability of these systems in aqueous media has been a major impediment in attempts at their resolution and unraveling of their molecular organization and mechanism of action.Among the forces contributing to the stability of these structures in aqueous media, hydrophobic attractions are most significant. This is because van der Waals attractions between apolar groups are weak and hydrogen bonds of the C..O ... H-N and C.0O ... H-0 type are, according to Klotz and co-workers,1 thermodynamically unstable if not protected from water. Since hydrophobic attraction is in essence a water-repulsion force, a consideration of the factors that influence the expulsion of most nonelectrolytes and the apolar regions of particulate proteins from water might provide significant clues to methods for increasing the solubility of such structures in aqueous media.According to Kauzmann,2 apolar groups form hydrophobic bonds mainly as a result of their thermodynamically unfavorable interaction with water, rather than as a consequence of interaction with each other. Thus, the transfer of an apolar molecule from a lipophilic surrounding to water is endergonic by 2-6 keal per mole because of an associated unitary entropy2 decrease of 10-20 entropy units (eu). (See, for example, the negative AH and AS values in Table 1 for the transfer of a variety of simple nonelectrolytes from benzene to water.) This large, negative entropy difference appears to be almost entirely related to the structure of water3-5 and can be diminished by changing the structure of water in the direction of greater disorder. Our studies suggest that such a condition can be created in the presence of certain inorganic anions.As shown in Table 2, the hydrated forms of anions such as SCN-, C1O-4, I-, Br-, and Cl-are associated with large, positive entropies. A simple interpretation of this large entropy increase (see also the entropies of hydration in Table 2) is the possible effect of these ions on the structure of water. This interpretation is in agreement with the conclusions of Hamaguchi and Geiduschek,6 1129

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A theory for stabilization of carbonium ions or other cations, by delocalization of neighboring bonds, is described. Such delocalization is available without changing the reactant geometry and is termed "vertical stabilization." The stabilizing influence is contrasted to the bridged-ion theory of neighboring group participation, in which the neighboring group moves toward the reaction center as the transition state is approached, and to frangomeric acceleration, in which the neighboring group moves away from the reaction center as the transition state is approached. The effects of structural changes on the magnitude of (vertical) -conjugation are discussed. In addition, further evidence is offered against significant effects of C-H hyperconjugation on bond lengths. Delocalization of bonds was first discussed in detail by Mulliken6 in his treatment of carbon-hydrogen hyperconjugation as an explanation of certain properties (1) Supported by the Air Force Office of Scientific Research, Grants AFOSR-69-1639 and AFOSR-69-1639A.(2) The effects ofconjugation on singlet neutral molecules, on free radicals, and on carbanions will be considered in subsequent papers.(3) The major part of these ideas was presented at the 155th National Meeting of the American Chemical Society, San Francisco, Calif., April 1968, p 39. Previous discussions ofconjugation in cations are found in ref 4a-g.(4) (a) W.

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The bioavailability of soil-bound polycyclic aromatic hydrocarbons (PAHs) for mammalian species was studied with rats fed with a diet containing contaminated soil preparations. The extent of cytochrome P450IA1 (CYP1A1) induction in the liver correlated with the amount of 5- and 6-ring PAHs in the soil samples but not with the total PAH content. Other cytochromes P450 were much less affected by the soil-contaminants. The highest induction of CYP1A1 was obtained with a sample containing 274 mg 5- and 6-ring PAH/kg soil, resulting in a nearly 360-fold increase in the ethoxyresorufin deethylase (EROD) activity. In a semilogarithmic plot, a linear correlation was found between the 5- and 6-ring PAH concentration in the soil and the microsomal CYP1A1 content. As a model for the action of intestinal fluids, soil samples were extracted by bile acid solution. In these experiments, the selectivity in the solubilization of individual PAHs parallels that of toluene extraction, although the yield is lower than the latter and varies with the soil sample. The bioavailability of PAHs for microorganisms, but not for mammals, was shown to be considerably reduced in the presence of high total organic carbon (TOC) values of the soil samples. This may have implications for decontamination strategies, diminishing the effectiveness of biological decontamination in cases with high TOC values. The data suggest that CYP1A1 induction in rats is a parameter that may be useful in risk assessments of contaminated soils for mammalian species.

Picrate (trinitrophenol) is a unique uncoupler of oxidative phosphorylation. Unlike the commonly used uncouplers (e.g., 2,4-dinitrophenol, pentachlorophenol, m-chlorocarbonylcyanide phenylhydrazone, and 5-chloro-3-t-butyl-2'-chloro-4'-nitrosalicylanifide), picrate seems to penetrate the mitochondrial inner membrane very slowly. Consequently, it is ineffective when added to intact mitochondria or to mitochondria depleted of their outer membranes. In contrast, when added to phosphorylating submitochondrial particles prepared by sonication in which the inner membrane orientation is inside-out, picrate binds to the uncoupler-binding sites and uncouples oxidative phosphorylation. This unique property of picrate has made it possible to compare the potencies of picrate and dinitrophenol for (a) uncoupling and (b) increasing the proton permeability of submitochondrial particle vesicles. At 50% uncoupling concentration, dinitrophenol increased the proton permeability of submitochondrial particle vesicles by 9-to 12-fold. In contrast, at 100% uncoupling concentrations or higher, picrate augmented the proton permeability of the particles by only about 3-fold. These results indicate that facilitation of transmembrane proton equilibration does not determine the degree of uncoupling, and lead to the corollary conclusion that the magnitude of transmembrane proton gradient need not be the quantitative driving force for ATP synthesis. 288 mitochondrial particles (ETPH), which are inside-out in orientation with respect to the medium, then picrate binds to the uncoupler-binding sites described above and uncouples oxidative phosphorylation. In view of these results, the effects of picrate and DNP were studied on the proton permeability of ETPH. It was found that the potencies of picrate and DNP for increasing the proton permeability of ETPH vesicles could not be correlated with their strength as uncouplers. These results are not only of interest with regard to the mechanism and site of uncoupling, but have important implications on the current theories of oxidative phosphorylation. MATERIALS AND METHODSHeavy beef-heart mitochondria and various types of submitochondrial particles were prepared according to published procedures (3-6). Rat-liver mitochondria and digitonintreated particles were prepared according to ref. 7 and 8, respectively. Protein was estimated by the biuret method (9). Oxygen uptake was measured polarographically, and Pi esterification was estimated either according to Estabrook (2) from the extent of state-3 respiration after ADP addition (Figs. 1 and 4), or with "sPi in the presence of hexokinase and glucose, as described in the legend for Fig. 2