Optical detection of photo-activated protein adsorption using Brewster angle microscopy

Bovine serum albumin (BSA) was space selectively immobilized onto a quartz substrate using photo-reactions initiated by pulsed laser irradiation of benzophenone derivatives tethered by silane coupling to the quartz. The excitation of the benzophenone with 266 nm light yields the pi-pi* triplet state with a quantum yield of 1. This triplet state then reacts with BSA in buffer solution in contact with the modified quartz. The triplet state may form a ketyl radical by reaction with the solution or it may abstract a proton directly from the BSA becoming covalently tethered to the surface. The entire deposition process was monitored in real time, in-situ using a Brewster angle microscope (BAM).