ALPHA-HELIX AND MIXED 310/ALPHA-HELIX IN COCRYSTALLIZED CONFORMERS OF BOC-AIB-VAL-AIB-AIB-VAL-VAL-VAL-AIB-VAL-AIB-OME
ALPHA-HELIX AND MIXED 310/ALPHA-HELIX IN COCRYSTALLIZED CONFORMERS OF BOC-AIB-VAL-AIB-AIB-VAL-VAL-VAL-AIB-VAL-AIB-OME
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DOI：
10.1073/pnas.86.3.765
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发表时间：
1989-02-01
影响因子：
11.1
通讯作者：
BALARAM, P
中科院分区：
文献类型：
--
作者：
KARLE, IL;FLIPPENANDERSON, JL;BALARAM, P
两分子量的Boc-Aib-Val-Aib-Aib-Val-Val-Val-Aib-Val-Aib-OMe（其中Boc是叔丁氧基羰基，Aib是α-丁氧羰基）氨基异丁酰基）在具有不同螺旋构象的三斜晶胞中共结晶。一个分子完全是α-螺旋形，具有七个5 →1分子内氢键。它形成了三个头到尾的NH。cntdot.. cntdot.O. dbd. C氢键与其他相同构象的分子。第二分子具有混合的310/α-螺旋构象，具有三个4 →1个氢键和4个5 →氢键。1氢键;此外，在两端有螺旋反转。第二个分子只与相同类型的分子形成两个头-尾氢键，N（3）H基团不参与任何氢键。这两种不同类型的螺旋在晶体中交替出现，每一片都是由相邻的螺旋棒通过首尾氢键形成的。在每一片中，只含有一种构象的螺旋，螺旋以平行模式聚集。在不同螺旋的片层之间，聚集是反平行的。具有式C51 H92 N10 O 13的肽在空间群P1中结晶，其中Z = 2，晶胞参数为α。= 10.047 .+-. 0.002埃，B = 16.684。0.003埃，c = 19.198。0.004埃，α。= 80.30 °.+-. 0.01 °，β。= 85.74 °.+-. 0.01 °，和γ= 83.03 °.+-. 0.01度; 6053个数据的总体一致性因子R = 6.7%（F0 > 3 σ）。和0.96-.分辨率
Two molcules of Boc-Aib-Val-Aib-Aib-Val-Val-Val-Aib-Val-Aib-OMe (where Boc is t-butoxycarbonyl and Aib is .alpha.-aminoisobutyryl) cocrystallize in a triclinic cell with different helical conformations. One molecule is completely .alpha.-helical with seven 5 .fwdarw. 1 intramolecular hydrogen bonds. It forms three head-to-tail NH.cntdot..cntdot..cntdot.O .dbd. C hydrogen bonds to other molecules of the same conformation. The second molecule has a mixed 310/.alpha.-helix conformation with three 4 .fwdarw. 1 hydrogen bonds and four 5 .fwdarw. 1 hydrogen bonds; furthermore, there is a helix reversal at both termini. The second moleucle forms only two head-to-tail hydrogen bonds with molecules of the same type, and the N(3)H group does not participate in any hydrogen bonding. The two different types of helices occur in alternate sheets, in the crystal, where each sheet is composed of adjacent rods of helices formed by head-to-tail hydrogen bonding. Within each sheet, containing helices of only one type of conformation, the helices aggregate in a parallel mode. Between the sheets of different helices, the aggregation is antiparallel. The peptide, with formula C51H92N10O13, crystallizes in space group P1 with Z = 2 and cell parameters .alpha. = 10.047 .+-. 0.002 .ANG., b = 16.684 .+-. 0.003 .ANG., c = 19.198 .+-. 0.004 .ANG., .alpha. = 80.30.degree. .+-. 0.01.degree., .beta. = 85.74.degree. .+-. 0.01.degree., and .gamma. = 83.03.degree. .+-. 0.01.degree.; overall agreement factor R = 6.7% for 6053 data ( F0 > 3.sigma.) and 0.96-.ANG. resolution.