Maleimido-proxyl as an EPR spin label for the evaluation of conformational changes of albumin

• Published in: European biophysics journal Vol. 46; no. 8; pp. 773 - 787
• Main Authors: Pavićević, Aleksandra, Luo, Jinghui, Popović-Bijelić, Ana, Mojović, Miloš
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2017; Springer Nature B.V
• Subjects: Animals; Binding; Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biophysics; Bovine serum albumin; Cattle; Cell Biology; Change detection; Cyclic N-Oxides - chemistry; Cysteine; Drug development; Electron paramagnetic resonance; Electron spin; Electron Spin Resonance Spectroscopy; Ethanol; Ethanol - pharmacology; Fatty acids; Fatty Acids - pharmacology; Hydrogen peroxide; Hydrogen Peroxide - pharmacology; Hydrogen-Ion Concentration; Labeling; Labels; Life Sciences; Membrane Biology; Models, Molecular; Monitoring; Nanotechnology; Neurobiology; Original Article; pH effects; Protein Conformation - drug effects; Protein Unfolding - drug effects; Proteins; Reactive oxygen species; Serum albumin; Serum Albumin, Bovine - chemistry; Spectroscopy; Spin labeling; Spin Labels; Superoxide; Superoxides - pharmacology; Temperature; Albumin; Maleimido-proxyl; Spin labeling; Electron paramagnetic resonance; Conformational changes; Reactive oxygen species (ROS)
• ISSN: 0175-7571; 1432-1017; 1432-1017
• DOI: 10.1007/s00249-017-1257-z

Albumin is the most abundant plasma protein and as such has been the subject of many studies using a variety of techniques. One of them, capable of monitoring the conformational changes and the binding capacity of proteins, is electron paramagnetic resonance spectroscopy (EPR) spin labeling. To date, albumin has been investigated using a number of different spin labels, mostly spin-labeled fatty acids (SLFAs). However, albumin can bind up to seven equivalents of fatty acids, making it difficult to determine which parts of the molecule undergo conformational changes. To obtain information from a specific site on a protein, spin labels that bind to free cysteine residues may be used. In this work, the applicability of such a label, 3-maleimido proxyl (5-MSL), was evaluated for monitoring conformational changes of bovine serum albumin (BSA) at different temperatures and pH values. Also, the effect of ethanol, reactive oxygen species (hydrogen peroxide and superoxide radical), and the binding of ligands specific for albumin, namely fatty acids, and several drugs were evaluated. The results indicate that the labeling of albumin at its free cysteine residue (Cys-34) using 5-MSL may successfully be used for the detection of conformational changes, even in the case of the subtle alterations induced by ligand binding.