Myoglobin-CO conformational substate dynamics: 2D vibrational echoes and MD simulations

Area of Science:

• Biophysics
• Protein Dynamics
• Spectroscopy

Background:

• Horse heart carbonmonoxymyoglobin (MbCO) is a model system for studying protein dynamics.
• Understanding conformational substates is crucial for protein function.
• Two-dimensional (2D) infrared vibrational echo spectroscopy offers insights into ultrafast molecular motions.

Purpose of the Study:

• To investigate the dynamics of MbCO conformational substates using 2D infrared vibrational echoes.
• To determine the temperature dependence of dephasing rates for different MbCO substates.
• To validate molecular dynamics simulations against experimental spectroscopic data.

Main Methods:

• Performed 2D infrared vibrational echo experiments on horse heart MbCO in water across various temperatures.
• Utilized molecular dynamics simulations to derive frequency-frequency correlation functions.
• Calculated vibrational echo decay based on simulation data.

Main Results:

• Identified distinct dephasing rates for the A(1) and A(3) conformational substates of MbCO.
• Observed different temperature dependencies for the dephasing rates of these substates.
• Demonstrated substantial agreement between calculated and experimentally measured vibrational echo decays.

Conclusions:

• 2D vibrational echo spectroscopy is a powerful tool for probing protein dynamics.
• The study provides experimental evidence for distinct dynamics of MbCO conformational substates.
• The results support the use of 2D vibrational echoes for testing structural assignments of protein substates.