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Updated: May 17, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Excited-state absorption and ultrafast relaxation dynamics of protoporphyrin IX and hemin
Agnese Marcelli1, Ivana Jelovica Badovinac, Nada Orlic
1European Laboratory for Non-Linear Spectroscopy, University of Firenze, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
Abstract:
The transient evolution of protoporphyrin IX (PPIX) and hemin following the Soret band excitation was measured in the 410-600 nm spectral region with sub-picosecond time resolution. In PPIX the relaxation pathway was characterized in the femto- and picosecond time scale by two processes with time constants of 350 fs and ~6 ps, describing the evolution of the system through internal Q(y) → Q(x) conversion and vibrational relaxation and cooling in the Q(x) state. The lifetime of the Q(x) state was found to be 10.4 ns by time resolved fluorescence measurements. In hemin, the ground state is completely recovered in tens of picoseconds through pathways involving CT and (d,d) states. The experimentally observed vibrational dynamics is mainly due to "hot" ground state transitions.
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