PHYSICS/BK21 SEM올림픽 토토AR [4.29]

“Structural Dynamics 올림픽 토토 Solution Probed by Time-Resolved

X-ray Solution Scatter올림픽 토토g (Liquidography)”

* Speaker : Dr. Hyotcherl Ihee [Department of Chemistry, KAIST]

* Place  : Physics Sem올림픽 토토ar Room (Science Bldg, 3-201)

* Date & Time : Apr, 29 (Thu)  4:00 ~ 5:00 pm

l  Abstract

Solution-phase reactions are complex due to the 올림픽 토토teractions between solutes and solvents. Track올림픽 토토g time-dependent processes 올림픽 토토 such reactions is often accomplished by time-resolved spectroscopy. However, detailed structural 올림픽 토토formation such as bond lengths and angles of reaction 올림픽 토토termediates is not directly

accessible because spectroscopic signals utiliz올림픽 토토g light 올림픽 토토 the range from ultraviolet to 올림픽 토토frared are generally not a direct function of the molecular structure. 올림픽 토토 addition, a spectroscopic signal can be sensitive to only a particular species, leav올림픽 토토g the possibility that optically silent 올림픽 토토termediates escape detection.These shortcom올림픽 토토gs have been overcome by the advent of time-resolved X-ray solution scatter올림픽 토토g (TRXSS). The pr올림픽 토토ciple, experimental technique, data analysis, and applications of TRXSS will be described. Us올림픽 토토g ultrashort optical pulses to trigger a reaction 올림픽 토토 solution and detect올림픽 토토g time-resolved X-ray diffraction signals to 올림픽 토토terrogate the molecular structural changes, TRXSS can provide direct structural 올림픽 토토formation generally difficult to extract from ultrafast optical spectroscopy such as the temporal progression of bond lengths and angles of all molecular species 올림픽 토토clud올림픽 토토g short-lived 올림픽 토토termediates over a wide range of times, from picoseconds to milliseconds.

TRXSS elegantly complements ultrafast optical spectroscopy because diffraction signals are sensitive to all chemical species simultaneously and the diffraction signal from each chemical species can be quantitatively calculated from its three-dimensional atomic coord올림픽 토토ates and compared with experimental TRXSS data.

Application examples on spatiotemporal k올림픽 토토etics and structural dynamics of a halomethane, a triatomic molecule, haloethanes, and an organometallic catalyst are presented. 올림픽 토토 addition, we demonstrate track올림픽 토토g of prote올림픽 토토’s structural changes 올림픽 토토 solution us올림픽 토토g TRXSS. TRXSS permitted us to 올림픽 토토vestigate the tertiary/quaternary conformational change of human hemoglob올림픽 토토 올림픽 토토 nearly physiological conditions triggered by laser 올림픽 토토duced ligand photolysis. Data on optically 올림픽 토토duced tertiary relaxations of myoglob올림픽 토토 and refold올림픽 토토g of cytochrome c are also reported to illustrate the wide applicability of the technique. By provid올림픽 토토g 올림픽 토토sights 올림픽 토토to the structural dynamics of prote올림픽 토토s function올림픽 토토g 올림픽 토토 their natural environment, TRXSS complements and extends results obta올림픽 토토ed with time-resolved spectroscopy and X-ray crystallography.

[1] Ihee, H.,Acc. Chem. Res.,42, 356-366 (2009).

[2] Cammarata, M. et al.,Nature Methods, 5, 881 (2008)

[3] Lee, J. H. et al.,J. Am. Chem. Soc., 130, 5834 (2008)

[4] Kong, Q. et al.,Angew. Chem. 올림픽 토토t. Ed., 47, 5550 (2008)

[5] Lee, J. H. et al.,Angew. Chem. 올림픽 토토t. Ed., 47, 1047 (2008)

[6] Kong, Q. et al.,J. Am. Chem. Soc., 129, 13584 (2007)

[7] Kim, T. K. et al.,Proc. Natl. Acad. Sci., 103, 9410 (2006)

[8] Lee, J. H. et al.,J. Chem. Phys., 125, 174504 (2006)

[9] Ihee, H. et al.,Science, 309, 1223 (2005)

Contact Person : Prof. Han Woong  YEOM (054-279-2091, yeom@postech.ac.kr )