ИСТИНА

Fluorescent proteins (FPs) have advanced our understanding of basic biology. FPs have been adopted for routine monitoring of gene activation as well as the selective labelling and analysis of single proteins, cellular organelles and whole cells; for the investigation of protein-protein interactions and other biologically-relevant events occurring in living cells; to sense many important properties of the cellular environment, including pH, ion flux, redox potential. Photoactivatable FPs have enabled multicolour imaging of fixed and live cells with resolution over the difraction limit. Far-red and near-infrared FPs and FPs with large Stokes shifts have greatly facilitated deep-tissue imaging in living animals. The application of FPs as a fluorescent tag for investigation of numerous cellular processes requires a carefull examination of the influence of surrounding environment on FP structure and function. We have shown previously that small concentration of chemical denaturant guanidine thiocyanate (GTC) exerts a pronounced effect on spectral features of super-folder GFP with no evident changes of protein’s tertiary structure. As molecule of GTC contains negatively charged ion of thiocyanate and positively charged ion of guanidine, observed changes can be defined by impact of one or both of these ions. To identify which of them are the main players we undertook the study of sfGFP dynamics by spectroscopic methods in the presence of other agents such as guanidine hydrochloride, sodium chloride and sodium thiocyanate. Our results revealed that observed changes are mainly induced by the negatively charged ions of thiocyanate that presumably bind near the chromophore and inhibit its anionic form.