Hasse symbols of trace forms of number fields

Thesis (master`s)--서울대학교 대학원 :수리과학부,2004.Maste

주기적인 감속파 조건을 지닌 RBWO의 전산 모사

Maste

재조합된 클래스 Ⅱ 주조직적합체의 펩타이드 결합 및 항체에서 CDR-H3의 구조 다양성에 관한 연구

학위논문(박사) - 한국과학기술원 : 생물과학과, 2000.8, [ xi, 98 p. ]한국과학기술원 : 생물과학과

단백질공학기술을 이용한 서브틸리신의 열안정성에 대한 연구

학위논문(석사) - 한국과학기술원 : 생물과학과, 1996.2, [ v, 53 p. ]Subtilsin J is an extracellular serine protease from Bacillus stearothermophilus. Subtilisin is one of the most intensively studied and widely used enzymes. In application to industry, stability of subtilisin is important. Many factors influence on stab ility of protein. Among them, this study focused on stability of helix and interhelical interaction. The segments of $Ser^{105}-Asn^{117}$ and $Ser^{132}-Gly^{146}$ of subtilisin J form α-helices. These two α-helices closely interact each other just as coiled-coil structure in surface of the molecule. First of all, to determine the role of N-terminus of α-helix in protein stability $Ser^{105}$ and $Ser^{132}$, N-termini of two neighboring α-heilces, were changed into Ala, Asp and Lys by site-directed mutagen sis. To determine the role of interaction between two N-termini of α-helices, four double mutant(S105A/S132A, S105D/S132D, S105D/S132K, S105K/S132D) were constructed. The half-life at 60℃ of S105A mutant protein was improved without changing the catalytic efficiency of the enzyme. Alanine replacement may result in more stable packing against hydrophobic core and decreased helical flexibility. S105D and S132D mutant protein showed improvement of thermostability through strengthened dipole moment. However thermostability of S105D/S132D double mutant protein was radically decreased. While S105K and S132K mutant proteins showed destabilization, the thermostability of S105K/S132D double mutant was nearly equal to that of wild-type protein. These results suggest that transition to alanine or aspartic acid in N-terminus of α-helix may improve protein stability through decrease of helical flexibility or increase of dipole moment and interaction of 105-residue and 132-residue has important influence on protein stability.한국과학기술원 : 생물과학과