Photosensitized Formation of Soluble Bionanoparticles of Lysozyme

Abstract

AbstractPhotosensitized crosslinking of hen egg‐white lysozyme (LZ) in buffer solutions was obtained by blue‐LED excitation of ruthenium (II) tris‐bipyridyl dication (Ru(bpy)32+) in a molar excess of persulfate anion (S2O82−), both in the absence and presence of dissolved oxygen. The results show a rapid monomer consumption of >75 %, with sequential formation of soluble LZ nanoparticles, e. g., dimers (LZ2),…n‐mers (LZn≥6) with diameters from 6 to 13 nm, regardless of the presence of dissolved oxygen in solution. The bionanoparticles are crosslinked through 3,3'‐dityrosine (diTyr) bonds, by the recombination of tyrosyl radicals of Y20, Y23, and Y53 residues of different protein molecules, produced by intermediated oxidants Ru(bpy)33+ and SO4.− generated after excitation. Furthermore, under aerobic conditions, photosensitized formation of singlet molecular oxygen (1O2) also results in the oxidative transformation of tryptophan residues into fluorescent kynurenine‐type derivatives. These findings may contribute to the rational development of functional protein bionanoparticles.