Interaction of Silver Nanoparticles with Triosephosphate Isomerase from Human and Malarial Parasite (Plasmodium falciparum): A Comparative Study.

Recombinant triosephosphate isomerase from Plasmodium falciparum (PfTIM) and humans (hTIM) were expressed, purified and characterised. High specific activity (1207 U x mg(-1)) with a fold purification of -1.8 and a yield of 48% were obtained for hTIM after gel filtration while, in contrast PfTIM afforded a specific activity of 1387 U x mg(-1) with a fold purification of -6.8 and a yield of 57% after gel filtration and prior to dialysis. PfTIM had an optimal pH and temperature, K(m) and V(max) of 5.25, 25 degrees C, 12.8 mM and 1.13 µmol x mL(-1) min(-1) respectively while for hTIM the pH and temperature optima, K(m) and V(max) were 6.75, 30 degrees C; 8.2 mM and 1.35 µmol x ml(-1) min(-1). Polyvinylpyrrolidone stabilised silver nanoparticles (60 nM; 2-6 nm diameter) selectively inhibited PfTIM with a 7-fold decrease in enzyme catalytic efficiency (K(cat)/K(m)) over hTIM. Respective K(i) values were 283 nM [hTIM] and 85.7 nM [PfTIM]. Key structural differences between the two enzyme variants, especially with Cys13 at the dimer interface of PfTIM, were significant enough to suggest unique characteristics allowing for selective targeting of PfTIM by AgNPs.

Neighborhood-frequency effects when primes and targets are of different lengths.

The present study provides a further investigation of the neighborhood-frequency effect. Using the masked priming procedure, we found that the neighborhood-frequency effect is obtained not only with primes and targets of the same length but also with primes and targets of a different length. This result is not compatible with most current versions of the interactive activation model. Implications of the finding are discussed.

The topography of agoraphobia.

Findings from empirical research and clinical practice are comprehensively integrated into a topography of the agoraphobic syndrome. The following topics are discussed successively: the agoraphobic syndrome (core mechanism and life pattern), the pathogenesis (causal mechanism, antecedents, and predispositions), the different kinds of anxiety from which agoraphobes can suffer, and the broad-spectrum therapeutic implications.