@misc{oai:ir.soken.ac.jp:00001249,
 author = {高, 影 and ガオイン and GAO, Ying},
 month = {2016-02-17, 2016-02-17},
 note = {The　iron protoporphyrin IX（<i>b</i> type heme）exists as a reaction center in most of the<br />heme proteins as a prosthetic group which bound with the protein matrix. It carries out<br />various functions including the diatomic gaseous ligand storage and transport，electron<br />transfer，oxidization，peroxidization，catalysis and signaling process and so on．For <br />investigating the active center, heme-iron-ligand complex，IR and visible RR spectroscopy<br />have revealed the heme environment structure and the ligand discrimination mechanism<br />for many heme proteins．Furthermore，electron paramagnetic resonance spectroscopy<br />and quantum mechanism study have been used to revealing the reaction mechanism of<br />heme enzyme．However, in any cases the accompanying conformational changes in<br />protein moiety always occur for regulating protein function as revealed by x-ray<br />crystallography. It appears quite important to establish a correlation between the active<br />center, heme，and the protein matrix for understanding the essential mechanism for<br />heme proteins. Also，this issue has attracted a lot of concerns from many fields. The<br />nature utilizes <i>b</i> type heme as the most common structure among the four kinds of hemes<br />that contain same framework but altered substitutions. Therefore, it is easy to propose<br />that the side chain of heme could play important role in regulation of protein structure<br />and function, and this propose is consistent with the discoveries from more and more<br />experimental data that side chains are involved in many reactions related with protein<br />functions. In this study, the interactions between heme and protein matrix as well as solvent leading<br />to intramolecular transduction of structural information and intermolecular energy transfer were<br />systematically investigated by using Mb. Those interactions include the covalent bond and the<br />hydrogen bonds between heme and globin and spatial collision between heme side chains and water<br />moleculs．<br />　　　In order to investigate　the　transmission of a binding slgnal of a gaseous ligand from the<br />ligand binding site?heme，to protein moiety in gas sensory heme proteins，we applied UVRR<br />spectroscopy to myoglobin as a model. UVRR spectroscopy is known as an excellent tool for<br />monitoring protein conformational changes. First of all，we determined the changes of conformation<br />in globin that occur upon binding of CO，NO，or O<small>2</small>to heme. Specifically，NO induces spectral<br /> changes in Trp residues of A-helix that are significantly different from those induced by O<small>2</small>or CO<br />binding. On the other hand，binding of O<small>2</small> to heme produces spectral changes in the Tyr residues of<br /> H-helix that are difftrent from those induced by CO or NO binding. The UVRR results demonstrate<br />that the heme discriminates among different ligands by driving corresponding conformational changes<br /> in the globin matrix. In order to explore the signaling pathway through His93 covalent bond，and 6-or<br />7-propionate hydrogen bonding network，we extended measurements to mutant-and heme-modified<br />Mbs in a similar way to native Mb, and investigated how they are responsible for transmitting<br />structural changes from ligand binding site--heme to globin for difftrent ligands. The experimental<br />results demonstrate that the cleavage of Fe-His93 covalent bond eliminates communication to the<br />C-terminal of the H-helix and that 7-propionate hydrogen-bonding network is essential for<br />transmitting the CO or NO binding signal to the N-and C-termini. Finally，6-propionate is important<br />only for NO binding. Thus，the hydrogen-bonding network in the protein appears to be critical for<br />intramolecular slgnal transduction in gas sensory heme proteins.<br />　　Furthermore, pathway of vibrational energy dissipation from the heme to<br />surrounding protein matrix and solvent following CO photolysis in the fast time<br />component (&le;10 ps）was investigated by using picosecond time-resolved anti-Stokes<br />Raman spectroscopy. The modified-and mutant Mbs，in which the 6- or 7-propionate is<br />selectively replaced by a methyl group or related hydrogen bonds is eliminated by<br />mutagenesis was used as model systems. The time constants of population decay of<br />vibrationally excited states for two modified Mbs became significantly larger compared<br />with those of native Mb．However the corresponding values of mutants are not different<br />from those of the native Mb．This work indicates that the two heme-propionate side<br />chains are highly involved in the energy transfer from the heme to solvent through the<br />collision with surrounding water molecules and contribute equally. But the hydrogen<br />bonding interactions with protein matrix seem to contribute scarcely to this fast energy<br />transfer process．This is the first experimental data estimating the contribution of<br />individual heme<sup>-</sup>propionate side chains to the vibrational energy transfer from the heme<br />to the surroundings．, application/pdf, 総研大甲第1013号},
 title = {Resonance Raman Investigation of Protein Dynamics Studies on  Myoglobin:  Information Transmission and Energy Funneling Mechanisms},
 year = {}
}