LAUSR

Myoglobin has important biological functions in storing and transporting small diatomic molecules in human body. Two possible orientations of carbon monoxide (CO) in the heme distal pocket (named as B1 and B2 states) of myoglobin have been experimentally indicated. In this study, ab initio quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulation of CO in myoglobin was carried out to investigate the two possible B states. Our results demonstrate that the B1 and B2 states correspond to Fe⋯CO (with carbon atom closer to iron center of heme) and Fe⋯OC (with oxygen atom closer to Fe), by comparing with the experimental infrared spectrum. QM electrostatic polarization effect on CO brought from the protein and solvent environment is the main driving force, which anchors CO in two distinctive orientations and hinders its rotation. The calculated vibrational frequency shift between the state B1 and B2 is 13.1 cm−1, which is in good agreement with experimental value of 11.5 cm−1. This study also ...