In vitro study of drug-protein interaction using electronic absorption, fluorescence, and circular dichroism spectroscopy

In the near future, design of a new generation of drugs targeting proteins will be required. Considering the complex bond between the drug and protein, the structure and stability of the target protein should be considered. So far, a series of in vitro investigations have been conducted with the aim of predicting drug-biological medium interactions. In these studies, use of spectroscopic methods, such as electronic absorption, fluorescence, and circular dichroism spectroscopy, which are briefly discussed in the present study, has been highlighted. The binding affinity of drug(s) to protein(s) and their binding mechanism(s) can be clearly determined by these methods, which reveal reactions in biological systems at low concentrations under physiological conditions. Ultraviolet-visible spectroscopy can be used as an accessible tool to measure slight changes in protein structure. Moreover, fluorescence spectroscopy provides tertiary structural information. On the other hand, circular dichroism spectroscopy in far-ultraviolet regions (180–260 nm) yields suitable information about different secondary structures of proteins. Conformational changes of proteins due to alterations such as physicochemical conditions, in vitro chemical modifications, and drug binding could impact ultraviolet-visible absorption, circular dichroism, and fluorescence spectra. Therefore, the study of changed spectra could reveal the structure-activity relationship of drug compounds and target proteins. In the present study, a short description of the mentioned methods, along with some related equations which are usually used to analyze and discuss the preliminary data, is presented. Overall, the obtained results could facilitate the development of biological and pharmaceutical potentials of drugs in the future.