The stretching frequencies of bound alkyl isocyanides indicate two distinct ligand orientations within the distal pocket of myoglobin

A study is conducted to gain insight into the low- and high-frequency peaks observed for the alkyl isocyanides upon binding to sperm whale myoglobin (Mb). The internal rebinding for in alkyl side chain conformation is promoted by the photodissociated ligand which is stuck in the distal pocket while the out conformation that inhibited geminate recombination is attributed to the part of the ligand that is already in an open E7 channel, poised for rapid escape.