**************** The 3rd., Lab Seminar *****************

Date: Mon, May 31, 2004  PM 1:30-

Place: No.616 Seminar room
　　　　　　 Graduate School of Information Science

Speaker: Masayoshi Takayanagi

Title: Transient Thermal Expansion of a Protein in Solution after
Photo-Excitation of the Chromophore: Deoxymyoglobin
　　　　　　Ryoji Miyata and Masahide Terazima
             Bulletin of the Chemical Society of Japan (BCSJ), 76, 1707-1712
　　　　　
Abstract:
 The energy releasing process from a photo-excited chromophore embedded in
a protein structure to the surrounding protein matrix and to the solvent is
studied for deoxymyoglobin by the acoustic peak delay method with the
transient grating technique. The acoustic peak delay time is usually a good
indicator of the solvent heating time by the nonradiative transition after
the photoexcitation and should be a positive value. However, the peak delay
after the photoexcitation of deoxymyoglobin was found to be -15 ps. The
observed negative peak delay was interpreted in terms of interference
between two acoustic waves: an acoustic wave due to the thermal expansion of
the protein and a wave of the medium. A theoretical calculation suggests
that most of the energy of the heme is first transferred to the protein part
and subsequently dissipates into the solvent. During this energy-releasing
process, the protein experiences the transient thermal expansion and it
creates an acoustic wave.

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