UV-Vis spectroscopic measurements consist one of the most widely used methods for protein quantification. This is due to the fact that the tryptophan and tyrosine (and to a lesser extent the phenylalanine) residues of proteins strongly absorb at 280 nm. Hence, the corresponding absorbance is used for the calculation of protein concentration, based on specific quantification formulas. If the protein sample does not have tryptophan or tyrosine, the concentration can still be easily measured by the absorption at 205 nm in which the peptide bonds are analysed directly (Scopes method). Conformational studies can also be performed under special conditions.
Dr. Stathis Frillingos is Professor of Biological Chemistry at the University of Ioannina, Department of Medicine, and Director of the Interinstitutional Interdepartmental Programme of Postgraduate Studies in Molecular and Cellular Biology and Biotechnology at the University of Ioannina, Greece (http://msc-mcbb.ac.uoi.gr). His research team focuses on the analysis of structure-function-specificity and evolutionary relationships of membrane transporters, with current emphasis on Solute Carriers responsible for the transmembrane transport of nucleosides, nucleobases and their antimetabolite analogs. His research studies include the functional characterization of new nucleobase/nucleoside transporters from microorganisms and analysis of their binding-site interactions with inhibitors and antimetabolite compounds as potential antimicrobial drugs (http://www.frillingoslab.gr).