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제105회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Azido Gauche Effect on the Backbone Conformation of beta-Azidoalanine Peptides

등록일
2010년 2월 23일 23시 05분 43초
접수번호
1325
발표코드
34P200포 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
발표시간
목 <발표Ⅱ>
발표형식
포스터
발표분야
물리화학
저자 및
공동저자
오광임, 조민행
고려대학교 화학과, Korea
To study the azido gauche effect on the backbone conformation of beta-azidoalanine blocked dipeptide (AAD) and tripeptide (AAT), we used spectroscopic methods in combination of quantum chemistry calculations and molecular dynamics (MD) simulations. From the NMR studies, we found that AAD in water prefers the gauche− (g−) side-chain conformer and adopts either polyproline II (PPII) or C7 backbone conformation. From the amide I IR absorption and circular dichroism (CD) spectra, the backbone conformation of AAD in water is found to deviate from PPII, but rather close to C7. Likewise, 1H NMR data for temperature dependence and NOESY experiments bring the same information of conformations up. Thus, the backbone conformation of AAD differs from that of AD, which is mainly PPII in water. The underlying origin of the backbone conformational difference between AAD and AD in water was elucidated by using the quantum chemistry calculation results. From the electronic structure calculations with density functional theory (DFT), it was found that the C7/g− conformer is the lowest energy structure of an isolated AAD. Here, the beta-azido group forms intramolecular electrostatic interactions with two neighboring peptide bonds, which are facilitated by the azido gauche effect. Thus, the -azido group appears to be responsible for directing peptide backbone conformation toward the C7 structure. The quantum mechanical/molecular mechanical (QM/MM) MD simulations show that AAD in water adopts neither PPII nor alpha-helix and prefers the g− conformer. Thus, the intramolecular electrostatic interactions between the beta-azido group and two nearby peptide bonds are also found even in the solution structure of AAD in water. Consequently, the beta-azido group appears to be an effective C7-conformation-directing element, which may also be useful for tuning the structures of other amino acids and polypeptides.

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