2001 Fiscal Year Final Research Report Summary
Structure and reaction dynamics in gas phase solute-solvent heteroclusters
| Project/Area Number |
10206209
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas (B)
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| Allocation Type | Single-year Grants |
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| Research Institution | Himeji Institute of Technology |
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Principal Investigator |
HONMA Kenji Himeji Institute of Technology, Department of Material Science, Associate Professor, 理学部, 助教授 (30150288)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Condenced Phase / Charge transfer reaction / Clusters / Protein folding / Electrospray |
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| Research Abstract |
We have carried out the following two projects and obtained some interesting results.
(1)Dynamics of the electronically excited state of 9,9'-bianthryl(BA) was studied in gas-phase clusters with acetonitrile (ACN), BA-(ACN)_n(n=1-5). The mass-selected two-color resonance-enhanced multiphoton ionization (REMPI) spectra were measured to determine the absorption band for the cluster of BA with the specific number of the acetonitrile molecules. The dispersed fluorescence (DF) spectra and lifetimes were measured for these absorption bands to study the dynamics of the excited state of BA in the clusters, BA-(ACN)_n. For all clusters studied, the DF spectra were broad and largely red shifted compared with that of unclustered BA. The fluorescence lifetimes of BA in the clusters were considerably longer than that of unclustered BA. These results suggested that the photoexcited state of BA in the clusters change to the polar excited state which is analogous to the twisted intramolecular charge tr
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ansfer (TICT) state of BA in the acetonitrile solution. Stokes shift and lifetime of the BA-(ACN)_1 suggested that the charge-transfer reaction becomes possible by adding one acetonitrile. However, these two properties of the larger clusters did not show monotonic change toward those of BA in acetonitrile solution. These results implied that the structure and dynamics of the clusters play some important roles in the charge-transfer reaction.
(2)The laser-induced fluorescence technique is applied to electrosprayed cytochrome c (cyt-c). While no fluorescence was observed for the electrospray of the solution of neutral pH, the fluorescence ascribed to the tryptophane residue was observed for the spray of the acidified solution by acetic acid. The relative intensity of the fluorescence from the acidified cyt-c is observed to increase with the distance from the end of the spray needle. This result indicates that the tryptophane residue becomes more fluorescent by the loss of solvent molecules in the electrospray. It is suggested that the highly charged cyt-c ions which preserve the nonfluorescent compact forms in solution make a conformational change by the loss of solvent in the electrospray and become fluorescent. Less
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