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제108회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Observation of geminate recombination of nitric oxide to metmyoglobin in D2O solution

2011년 8월 5일 10시 26분 15초
Ⅲ-PHYS.P-45 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
금 <발표Ⅲ>
저자 및
박재흥, 이태곤, 박재헌1, 임만호
부산대학교 화학과, Korea
1포항공과대학교 포항가속기연구소/빔라인부, Korea
Many NO’s biological functions come from its interactions with heme proteins, such as cytochrome c oxidase, hemoglobin, NO synthase enzymes. Recently, it has been revealed that oxymyglobin (MbO2) plays a role as an NO scavenger, regulating process, ferric myoglobin (Mb(III)) is yielded. Because ferric Mb can bind to NO, it reacts with another NO molecule to yield ferrous MbNO. Other neutral ligand such as CO and O2 binds only to ferrous Mb and anions can bind to ferric heme but NO can bind both ferrous and ferric heme. We had measured the rebinding dynamics of NO to ferrous Mb and found that most of NO geminately rebinds nonexponentially in 1 ns. Vibrational bands of NO in MbNO revealed two bands and kinetics of the rebinding of both bands are identical, indicating that the dynamics of geminate rebinding to ferrous Mb is conformationally independent. Here we investigated NO rebinding dynamics to ferric Mb and compare it with that of ferrous Mb. Stretching mode of NO has two overlapping bands, main band at 1921 cm-1 and minor one at 1904 cm-1, suggesting that ferric MbNO has at least two conformational substates. We observed that 80% of NO dissociated from heme after photo excitation and the rest of them relax to the ground state by vibrational relaxation. The rebinding of NO to ferric Mb in D2O at 293 K is nonexponential. The decay of the main band is slower than that of ferrous MbNO band but almost ~80% complete in 1 ns, indicating that NO rebinding to the main conformation of ferric Mb is less efficient than ferrous Mb. The minor band shows clearly slower decay than the major one. The minor conformation is suggested to arise from the interaction of the protonated His 64 with NO. Clearly the structure of amino acid residues near the active site of the protein is very critical in controlling protein function (ligand binding).