Synthesis and redox characterization of the polyoxo anion, gamma*-[S2W18O62]4-: a unique fast oxidation pathway determines the characteristic reversible electrochemical behavior of polyoxometalate anions in acidic media.

The synthesis and characterization of (Bu4N)4[S2W18O62].1.23MeCN.0.27H2O are reported. It crystallizes in the monoclinic space group C2/c with a = 22.389(6) A, b = 22.104(3) A, c = 25.505(5) A, beta = 95.690(15) degrees, V = 12560(5) A3, and Z = 4. The anion exists as the gamma* isomer, the second example of this isomer type to be characterized structurally. The equivalent molybdenum salt occurs as the alpha isomer. gamma*-[S2W18O62]4- in MeCN solution displayed four electrochemically reversible one-electron redox processes at E1/2 values of -0.24, -0.62, -1.18, and -1.57 V versus the Fc+/Fc couple. Upon addition of acid in MeCN/H2O (95/5 v/v), the two most cathodic processes converted to an overall two-electron process at -0.71 V. The total data suggested that this process actually comprises two one-electron transfer processes, occurring at different potentials, with associated proton-transfer reactions. The interpretation is supported by simulation of the effect of acid titration upon the cyclic voltammetry. While multiple pathways for correlated reduction and protonation are present in both the molybdenum and tungsten systems, only a single fast oxidation pathway is available. As the reduced forms of [S2W18O62]4- are much weaker bases than those of [S2Mo18O62]4-, the individual oxidation pathways are not the same. However, their existence determines the highly reversible electrochemical behavior that is characteristic of these anions, and that of polyoxometalate systems in general.

Design and synthesis of type-III mimetics of omega-conotoxin GVIA.

Our interest lies in the rational design and synthesis of type-III mimetics of protein and polypeptide structure and function. Our approach involves interactive design of conformationally defined molecular scaffolds that project certain functional groups in a way that mimics the projection of important binding residues as determined in the parent structure. These design principles are discussed and applied to the structurally defined polypeptide, omega-conotoxin GVIA, which blocks voltage-gated, neuronal N-type calcium channels. These ion channels represent therapeutic targets for the development of new analgesics that can treat chronic pain. It is shown how a discontinuous, 3-residue pharmacophore of GVIA can be mimicked by different molecular scaffolds. It is illustrated how such 1st generation leads must necessarily be weak and that optimisability must therefore be built-in during the design process.

Evaluating development programs: administrative self-assessment in four Asian nations.

PIP: In the belief that self-assessment is a valid technique of evaluation, self-assessments were gathered in the effort to help evaluate the administrative capabilities of specific programs essential to the economic development of Indonesia, Korea, the Philippines, and Thailand. The government of each country established agricultural development programs in the late 1960s in order to improve the production of rice, the major food crop. The data for analysis were collected by means of lengthy interviews with a random sample of rice production officials in the 4 countries. By using the self-anchoring scale, administrative personnel evaluated their administrative systems in their own terms. The free-answer responses demonstrated that, even at the local level, program personnel are aware of the major issues which confront policy-makers and administrators in their countries. Their criteria for assessing administrative capability emphasize different aspects of resource inputs, administrative procedures, and policy outputs. Significant differences emerged in the degree to which administrative practices measured up to the ideals of rice program officials in the 4 countries. Officials in the Philippines were consistently more optimistic and assessed their conditions more favorably than respondents in other countries, and this is particularly true of assessments of the capabilities of the rice program itself. Indonesian rice officials were less enthusiastic about their own program in comparison to government programs as a whole. The Koreans found that current government performance in general came closest to their expectations. The Thais were more favorable in their assessments of their personal situations and of the rice program.^ieng