Ramos, S, Duarte RO, Moura JJ, Aureliano M.
2009.
Decavanadate interactions with actin: cysteine oxidation and vanadyl formation, Oct 14. Dalton Trans. :7985-94., Number 38
AbstractIncubation of actin with decavanadate induces cysteine oxidation and oxidovanadium(IV) formation. The studies were performed combining kinetic with spectroscopic (NMR and EPR) methodologies. Although decavanadate is converted to labile oxovanadates, the rate of deoligomerization can be very slow (half-life time of 5.4 h, at 25 degrees C, with a first order kinetics), which effectively allows decavanadate to exist for some time under experimental conditions. It was observed that decavanadate inhibits F-actin-stimulated myosin ATPase activity with an IC(50) of 0.8 microM V(10) species, whereas 50 microM of vanadate or oxidovanadium(IV) only inhibits enzyme activity up to 25%. Moreover, from these three vanadium forms, only decavanadate induces the oxidation of the so called "fast" cysteines (or exposed cysteine, Cys-374) when the enzyme is in the polymerized and active form, F-actin, with an IC(50) of 1 microM V(10) species. Decavanadate exposition to F- and G-actin (monomeric form) promotes vanadate reduction since a typical EPR oxidovanadium(IV) spectrum was observed. Upon observation that V(10) reduces to oxidovanadium(IV), it is proposed that this cation interacts with G-actin (K(d) of 7.48 +/- 1.11 microM), and with F-actin (K(d) = 43.05 +/- 5.34 microM) with 1:1 and 4:1 stoichiometries, respectively, as observed by EPR upon protein titration with oxidovanadium(IV). The interaction of oxidovanadium(IV) with the protein may occur close to the ATP binding site of actin, eventually with lysine-336 and 3 water molecules.
Ribeiro, MP, Espiga A, Silva D, Baptista P, Henriques J, Ferreira C, Silva JC, Borges JP, Pires E, Chaves P, Correia IJ.
2009.
Development of a new chitosan hydrogel for wound dressing. Wound repair and regeneration. 17(6):817–824., Number 6: Blackwell Publishing Inc
AbstractWound healing is a complex process involving an integrated response by many different cell types and growth factors in order to achieve rapid restoration of skin architecture and function. The present study evaluated the applicability of a chitosan hydrogel (CH) as a wound dressing. Scanning electron microscopy analysis was used to characterize CH morphology. Fibroblast cells isolated from rat skin were used to assess the cytotoxicity of the hydrogel. CH was able to promote cell adhesion and proliferation. Cell viability studies showed that the hydrogel and its degradation by-products are noncytotoxic. The evaluation of the applicability of CH in the treatment of dermal burns in Wistar rats was performed by induction of full-thickness transcutaneous dermal wounds. Wound healing was monitored through macroscopic and histological analysis. From macroscopic analysis, the wound beds of the animals treated with CH were considerably smaller than those of the controls. Histological analysis revealed lack of a reactive or a granulomatous inflammatory reaction in skin lesions with CH and the absence of pathological abnormalities in the organs obtained by necropsy, which supported the local and systemic histocompatibility of the biomaterial. The present results suggest that this biomaterial may aid the re-establishment of skin architecture.
Feio, G, Figueirinhas JL, Tajbakhsh AR, Terentjev EM.
2009.
Deuterium NMR study of mobility and fluctuations in nematic and isotropic elastomers. J Chem Phys. 131:074903., Number 7
AbstractOrientational ordering in polydomain nematic and isotropic elastomers with identical polysiloxane backbone and different deuterium-labeled side groups is studied by D-NMR. In the nematic elastomer the orientational order parameter grows in a critical fashion on crossing the I-N transition implying a continuous phase transition driven by critical fluctuations of local director. The orientational (nematic) ordering occurs on the background of the polymer dynamics exhibited by the backbone, which is similar in the nematic and the analogous isotropic elastomers. The temperature dependence of NMR linewidths is compatible with a Vogel-Fulcher glassy dynamics.