The influence of donor substituents on spectral properties and biological activities of fluorescent markers conjugated with protein

Abstract

In the modern biological-chemical research, a strong emphasis is put on the design and synthesis of new fluorescent markers used for protein labelling. This involves molecular design taking into account the best selection of the fluorophore structure reactive group, through which conjugation with protein occurs. Very often, the procedure of introducing activating groups into the fluorophore structure is used to obtain required spectral properties. For this reason, the presented studies are aimed at identifying the groups that cause the smallest spectral and biological changes in fluorescent labels after conjugation with the protein, based on the chalcone analogous compounds (ChD). Detailed analysis of the effect of the strength of donor substituents on the spectral properties, two-photon absorption cross section, in combination with assessment of their impact on the site of active binding to the protein and biological activities highlighted that the presence of medium-strong activating substituents, in particular OH and OCH3, will be the factor optimizing the desired photophysical and biological features, and therefore required in the structure of the marker. In addition, this work presents a simplified protein model that allows precise determination of spectral properties for the bimolecular MARKER-PROTEIN complex.