Ultrafast dynamics of hemin aggregates

Area of Science:

• Physical Chemistry
• Biophysical Chemistry
• Spectroscopy

Background:

• Hemin conformation and dynamics are influenced by solvent environments.
• Understanding heme self-assembly is crucial for biological systems.
• Nonlinear optical properties of hemin are not fully characterized.

Purpose of the Study:

• To investigate the impact of solvents on hemin conformation and dynamics.
• To measure the nonlinear electronic susceptibility (χ(3)) of hemin solutions.
• To identify novel dynamic processes in hemin solutions.

Main Methods:

• Time-resolved optical Kerr effect (OKE) spectroscopy.
• Ultrafast laser pulses (35 fs, 800 nm).
• Analysis of nonlinear electronic susceptibility (χ(3)).

Main Results:

• Hemin solutions exhibit a significantly smaller χ(3) compared to thin films.
• Negative real and imaginary components of χ(3) indicate one- and two-photon absorption.
• A novel femtosecond libration process, possibly due to π-π hemin oligomers, was detected.

Conclusions:

• Solvent interactions significantly affect hemin's conformational dynamics.
• The study reveals a previously undetected libration process in hemin oligomers.
• Findings provide insights into heme self-assembly and potential roles in pathogenic conditions.