Tyrosine fluorescence probing of the surfactant-induced conformational changes of albumin.

Tyrosine fluorescence in native proteins is known to be effectively quenched, whereas its emission increases upon proteins' unfolding. This suggests that tyrosine fluorescence could be exploited for probing structural rearrangements of proteins in addition to the extensively used tryptophan emission. We studied the possibility of using tyrosine fluorescence as an indicator of surfactant-induced conformational changes in albumins. It was shown that fluorescence of tyrosine residues, which are uniformly distributed all over the protein molecules, allows the detection of subtle structural rearrangements of proteins upon surfactant binding, which do not influence the properties of a single tryptophan residue buried in the inner hydrophobic region of human serum albumin. Tyrosine fluorescence properties, including its fluorescence lifetime, revealed the multistage character of surfactant binding to albumin, consistent with the data provided by other methods. The obtained results demonstrate the possibility of probing conformational changes in proteins using tyrosine photophysical parameters as indicators.

Raman spectroscopy and fluorescence analysis in investigation of the protective action of ischemic preconditioning at ischemic insult by estimation of damage of low-density lipoprotein of blood.

OBJECTIVE AND BACKGROUND DATA: In recent years medical researchers have sought a method of ischemic preconditioning, which is training an organ for prolonged total ischemia by inducing short periods of ischemia. In this work we detail research on this modality, conducted before ischemic insult in Wistar rats, in order to quantify the amount of damage done to low-density lipoprotein (LDL) in the blood. In previous research we used optical spectral methods to ascertain changes in LDL in the blood of animals after ischemic insult. The changes in LDL incurred by ischemic insult are explained by the free radical theory of oxidative stress. METHODS: We used Raman spectroscopy and fluorescence analysis to determine if ischemic preconditioning performed before an ischemic insult renders protection against later ischemia, by analyzing reductions in damage done by free radicals to LDL. RESULTS AND CONCLUSION: The adaptive effects of preconditioning were seen as the attenuation of the generation of free radicals by mitochondria of brain cells during total ischemia. Ischemic preconditioning also activates antioxidant systems, limiting the development of radical oxidative processes.

Electronic and magnetic properties at the edges of nanostructures in an electric field: ab initio study.

State of the art ab initio calculations of the electronic and magnetic properties at the edges of magnetic nanostructures in an external electric field are presented in this paper. Our results for the Fe stripes on Fe(0 0 1) reveal the existence of spin-polarized edge states. A spatially inhomogeneous electronic structure is found at the edge. We demonstrate that the spin-dependent screening density varies greatly at the atomic scale. Tuning of the spin-polarization by the external electric field is demonstrated.