Interaction of N-acyl derivative of 4-phenoxyaniline spin label with bovine serum albumin in water and in trehalose solution

Abstract

The interaction between a new spin probe, prepared by spin labelling 4-phenoxyaniline with the TEMPO paramagnetic moiety, and bovine serum albumin was studied for solutions in water and in trehalose. At the same time, the interaction of this spin probe with cyclodextrin provided information on the binding affinity and on the geometry of the host–guest complex. In order to obtain conclusive information on these interactions, the following physicochemical methods were used in this study: electron paramagnetic resonance, UV-Vis spectroscopy, circular dichroism, along with microcalorimetry and molecular docking. The experimental data showed that trehalose influences the effect of the spin probe binding to albumin on the secondary structure of the protein. The competitive experiment with cyclodextrin indicated its ability to extract the spin probe from the binding pocket of the albumin. The EPR spectroscopy data, together with UV-Vis data, provided insights into how the formation of the inclusion complex occurs, specifically via the aromatic fragment.