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Artemin is an abundant thermostable protein in Artemia embryos and it is considered as a highly efficient molecular chaperone against extreme environmental stress conditions. The conformational dynamics of artemin have been suggested to play a critical role in its biological functions. In this study, we have investigated the conformational and functional changes of artemin under heat and oxidative stresses to identify the relationship between its structure and function. The tertiary and quaternary structures of artemin were evaluated by fluorescence measurements, protein cross-linking analysis, and dynamic light scattering. Based on the structural analysis, artemin showed irreversible substantial conformational lability in responses to heat and oxidant, which was mainly mediated through the hydrophobic interactions and dimerization of the chaperone. In addition, the chaperone-like activity of heated and oxidized artemin was examined using lysozyme refolding assay and the results showed that although both factors, i.e. heat and oxidant, at specific levels improved artemin potency, simultaneous incubation with both stressors significantly triggered the chaperone activation. Moreover, the heat-induced dimerization of artemin was found to be the most critical factor for its activation. It was suggested that oxidation presumably acts through stabilizing the dimer structures of artemin through formation of disulfide bridges between the subunits and strengthens its chaperoning efficacy. Accordingly, it is proposed that artemin probably exists in a monomer–oligomer equilibrium in Artemia cysts and environmental stresses and intracellular portion of protein substrates may shift the equilibrium towards the active dimer forms of the chaperone. [ABSTRACT FROM AUTHOR]

Future biomedical applications of nanoparticles will encounter these particles with patients' serum which might affect the properties and stability of quantum dots and serum proteins at the desired site of action. Therefore, it is essential to clarify the patient-specific serum components, serve as major interaction partners, the spatial distribution of these, and consequently the time-dependent effects of nanoparticle–protein interaction. Here, a biochemical and structural study was performed on the protein corona formation and the corresponding interaction of different sizes of CdTe QDs with human serum proteins to determine if the mutual effects on optical properties by using electrophoresis, chemiluminescence, and fluorescence spectroscopy. The results revealed that interaction with human serum significantly enhanced the stability and photoluminescence of quantum dots. Structural studies of HSA-coated CdTe QDs also showed that corona formation has no adverse effects on protein structure, and the reduction in fluorescence emissions of HSA is due to the direct quenching of aromatics residues by the quantum dot. Improving nanoparticle properties, as well as the lack of structural changes in HSA, can be very useful in biomedical applications and in vivo studies where stability is important. Image 1 • The structural changes and optical properties of protein and CdTe QDs upon corona formation were investigated. • Interaction of quantum dots with human serum albumin significantly enhanced the stability and photoluminescence of QDs. • Structural studies of HSA-coated CdTe QDs showed that corona formation has no adverse effects on protein structure. • This study will help to predict the nanoparticle–cell interaction and to rate the biocompatibility of nanoparticles. [ABSTRACT FROM AUTHOR]

Apoptosis, a physiologic mechanism to eliminate unwanted cells, is also induced by ionizing irradiation, through production of free radicals. It has been demonstrated that antioxidants such as vitamin E are able to protect cells from damage caused by free radicals. Taken together we found it reasonable to make an attempt to evaluate the protective effect of vitamin E against apoptosis. The irradiated mice received 1 Gy/day gamma radiation for one day (low dose) or for three successive days (high dose, 3Gy). The splenocytes were then isolated at 6, 14 and 24 h after exposure. DNA gel electrophoresis and DNA fragmentation assay were done in addition to the evaluation of splenocytes cytology.Our results showed that Vitamin E can reduce apoptosis against low dose irradiation. However it is not able to completely block programmed cell death in high dose irradiation.