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In this article we show how the quasi-Gaussian entropy (QGE) theory can be used to treat systems of polyatomic flexible molecules, where the usual semirigid description is not always appropriate. We describe a completely general derivation of the QGE theory which does not make use of any semirigid approximation, and therefore it is very suited for large and flexible molecules. Using molecular dynamics simulations of flexible molecules in vacuo, we investigated the ability of the theory to describe intramolecular energy fluctuations and conformational equilibria of purely classical molecules in the ideal gas condition. Results show that the gamma state level of the theory and its generalization for treating conformational equilibria (multi-gamma state model) provide excellent theoretical models when applied to three polyatomic molecules of increasing conformational freedom.

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Herein we describe a novel contribution to the developing field of NN bond cleavage reactions, [1±3] in which we have for the first time cleaved the NN bond by using light and transition metal complexes. Only two groups [1, 2] have so far given detailed information on the pathways leading to the sixelectron reduction of dinitrogen. Such a reduction is a stepwise metal-assisted transformation consisting, usually, of a four-electron reduction of N 2 , leading to a dimetallahydrazone, L n MNÀNML n , followed by a final, thermally induced reductive cleavage of the residual NÀN bond. The present report focuses on the generation of the d 3 -[Mo(Mes) 3 ] frag-attraction between cationic ester 2 and vesicles rendered anionic by the presence of 1) likely augment hydrophobic association. Adjusted for the concentration differences, the intra-vesicular reaction rate is equivalent to that of the intermolecular reaction between monomeric species (Table 1, entry 2). An entropically favorable confinement of the reactants within the bilayer assembly must evidently compensate for any inhibitory rate effects inherent to the membrane environment.With all the control runs suitably investigated, we were able to examine the vesicle/vesicle reaction (Table 1, entry 7). Its t 1/2 of 4.2 min indicates a much faster reaction than vesicular 2 plus monomeric acetohydroxamate (Table 1, entry 4, t 1/2 180 min). This fact, plus the highly efficient intra-vesicular reaction evident in entry 6, suggests a reasonable mechanism for the vesicle/vesicle reaction: Collisions between vesicles containing l and vesicles containing 2 lead to a transfer of 2 from one vesicle population to the other. [18] (Potent steroidal anchoring of 1 has been shown previously to prevent a corresponding migration of the nucleophile within our timescale). [10] A fast intra-vesicular catalyzed hydrolysis, depicted schematically in Figure 1, ensues.A possible variation of the above vesicle-transfer mechanism was considered. Perhaps ester 2 departs from its vesicles, enters the water, and re-adsorbs into the vesicles containing nucleophile 1. To test this idea, we studied the vesicle/vesicle reaction with an ester in which the dodecyl chain had been replaced by an octadecyl group. Adding six more carbon atoms should seriously impede any partitioning of the ester from the membrane into the free solution.Yet the vesicle/vesicle rates with the octadecyl analogue are only fourfold smaller than with the dodecyl ester 2. This result is fully consistent with a collision-induced vesicle-to-vesicle transfer that is mildly retarded by the longer chain length. At the moment, organic reactivity among various colloidal particles is a scientific nursling. Further experimentation in the area, as colloid chemistry simulates and ultimately subsumes biology, is an easy call.

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