Cupricyclins, Novel Redox-Active Metallopeptides Based on Conotoxins Scaffold

Highly stable natural scaffolds which tolerate multiple amino acid substitutions represent the ideal starting point for the application of rational redesign strategies to develop new catalysts of potential biomedical and biotechnological interest. The knottins family of disulphide-constrained peptides display the desired characteristics, being highly stable and characterized by hypervariability of the inter-cysteine loops. The potential of knottins as scaffolds for the design of novel copper-based biocatalysts has been tested by engineering a metal binding site on two different variants of an ω-conotoxin, a neurotoxic peptide belonging to the knottins family. The binding site has been designed by computational modelling and the redesigned peptides have been synthesized and characterized by optical, fluorescence, electron spin resonance and nuclear magnetic resonance spectroscopy. The novel peptides, named Cupricyclin-1 and -2, bind one Cu2+ ion per molecule with nanomolar affinity. Cupricyclins display redox activity and catalyze the dismutation of superoxide anions with an activity comparable to that of non-peptidic superoxide dismutase mimics. We thus propose knottins as a novel scaffold for the design of catalytically-active mini metalloproteins

Dynamics of personality changes in prisoners as a result of the social work with them

This article deals with the dynamics of personality changes in people serving a prison sentence whereas these changes are as result of the social work performed in prisons. Analyzed are some personality characteristics displayed in the context of emotional intelligence and social empathy in people with delinquent behavior of different age and of different social, educational, psychosomatic and family status

Oxidation of oxymyoglobin by poplar plastocyanins <i style="">a</i> and <i style="">b</i>

383-388Oxidation of oxymyoglobin [MbO2 (Fe2+)] by isoplastocyanins a (PCa) and b (PCb) was experimentally investigated and the corresponding redox reaction was modeled using the physicochemical parameters of the isoforms to study the effect of the dimorphism. The kinetic curve of oxidation of MbO2 (Fe2+) by oxidized PCa [PCa(Cu2+)] and PCb [PCb(Cu2+)] and the pH-dependence of the rate constant k1 were determined. In the range of pH 4.8-9.0, PCb reacts with higher k1, compared with PCa. For example, at pH 7.0, k1(PCb) = 4 × 102 M-1s-1, whereas k1(PCa) = 2 × 102 M-1s-1. The observed values of ΔE0 for the reaction pairs Mb-PCa and Mb-PCb were -304 mV and -319 mV, respectively. The effect of the ionic strength (µ) on the rate of the electron transfer was also studied. It was found that: (i) the net charge Z1 of PCa and PCb fully corresponds to that calculated by their primary structures and Z2 of Mb corresponds to that calculated by its titration curve; (ii) the ln k as function of √¯µ was similar for both PCa and PCb; (iii) the curve of the reaction PCb Mb (pH 7.0) was shifted towards higher values of k, in agreement with the larger net negative charge of PCb; and (iv) the character of the electrostatic interactions remained unchanged by a replacement of PCa by PCb and by the change of pH from 7.0 to 4.8

Structural comparison of the poplar plastocyanin isoforms PCa and PCb sheds new light on the role of the copper site geometry in interactions with redox partners in oxygenic photosynthesis

Plastocyanin (PC) from poplar leaves is present in two isoforms, PCa and PCb, which differ in sequence by amino acid replacements at locations remote from the copper center and simultaneously act in the photosynthetic electron-transport chain. We describe ultra-high resolution structures of PCa and high-resolution structures of PCb, both under oxidizing and reducing conditions at pH 4, 6 and 8. The docking on cytochrome f and photosystem I, respectively, has been modeled for both isoforms. PCa and PCb exhibit closely similar overall and active-site structures, except for a difference in the relative orientation of the acidic patches. The isoforms exhibit substantial differences in the dependence of the reduced (Cu(I)) geometry on pH. In PCa, the decrease in pH causes a gradual dissociation of His87 from Cu(I) at low pH, probably adopting a neutral tautomeric state. In PCb, the histidine remains covalently bound to Cu(I) and may adopt a doubly protonated state at low pH. The fact that both isoforms have similar although not identical functions in photosynthetic electron flows suggests that the His87 imidazole does not play a crucial role for the pathway of electron transport from cytochrome f to oxidized PC