BIOPHYSICAL THEORY AND MODELING |
The Role of Higher CO-Multipole Moments in Understanding the
Dynamics of Photodissociated Carbonmonoxide in Myoglobin
Nuria Plattner 1 and Markus Meuwly 2*
1 Department of Chemistry
2 University of Basel
* To whom correspondence should be addressed. E-mail: m.meuwly{at}unibas.ch.
Submitted on August 23, 2007
Revised on October 18, 2007
Accepted on 6 November 2007
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Abstract |
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The influence of electrostatic multipole moments up to hexadecapole on the dynamics of photodissociated CO in Myoglobin is investigated. The CO electrostatic potential is expressed as an expansion into atomic multipole moments of increasing order up to octopole which are obtained from a distributed multipole analysis (DMA). Three models with increasingly accurate molecular multipoles (accurate quadrupole, octopole and hexadecapole moments, respectively) are developed and used in molecular dynamics simulations. All models with a fluctuating quadrupole moment correctly describe the location of the B-state whereas the sign of the octopole moment differentiates between the Fe···CO and Fe···OC orientation. For the infrared spectrum of photodissociated CO considerable differences between the three electrostatic models are found. The most detailed electrostatic model correctly reproduces the splitting, shift and width of the CO spectrum in the B-state. From an analysis of the trajectories the spectroscopic B1 and B2 states are assigned to the Fe···CO and Fe···OC substates, respectively.
Key Words:
Carboxymyoglobin, Distributed Multipole Analysis, Infrared Spectroscopy, Molecular Dynamics
