STRUCTURE AND CONFORMATIONS OF 2 CYCLOISOMERIC HEXAPEPTIDES - CYCLO(L-LEU-L-PHE-GLY-D-PHE-L-LEU-GLY-) TRIHYDRATE AND CYCLO(L-PHE-L-LEU-GLY-D-LEU-L-PHE-GLY-) TRIHYDRATE
STRUCTURE AND CONFORMATIONS OF 2 CYCLOISOMERIC HEXAPEPTIDES - CYCLO(L-LEU-L-PHE-GLY-D-PHE-L-LEU-GLY-) TRIHYDRATE AND CYCLO(L-PHE-L-LEU-GLY-D-LEU-L-PHE-GLY-) TRIHYDRATE
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DOI：
10.1107/s0108768189010633
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发表时间：
1990-04-01
影响因子：
1.9
通讯作者：
VANDERHELM, D
中科院分区：
文献类型：
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作者：
BARNES, CL;HOSSAIN, MB;VANDERHELM, D
Cyclo(L-Leucyl-L-phenylalanyl-glycyl-D-phenylalanyl-L-leucyl-glycyl-)三水合物(IV)，C34H46N6O6-3H2O，MR=688.8，单斜晶系，P21，α。=11.720(2)，b=36.354(4)，c=8.888(1)。=103.88(1)°，V=3676.3°3，Z=4，Dx=1.244 g cm~(-3)，λ。(Cu Kα)=1.54178.ANG、.MU=7.6 cm~(-1)，F(000)=1480，T=138K，最终R=0.052。三水cyclo(L-Phenylalanyl-L-leucyl-glycyl-D-leucyl-L-phenylalanyl-glycyl-)(V)，C34H46N6O6-3H2O，MR=688.8，三斜酸，P_1，α。=11.668(3)，b=19.111(5)，c=8.527(1)。=101.54(2)，β。=93.42(2)，.=94.27(2)度，V=1852.4°3，Z=2，Dx=1.235克厘米~(-3)，λ(Cu Kα)=1.54178。=7.5 cm~(-1)F(000)=740，T=138K，最终R=0.063，对应7574次独特反射。多肽IV和V都有两个独立的构象(分子A和B)。每种情况下的肽环都包含一个β(I)转角和一个β(ii‘’)转角。两种结构中的A分子都有两个跨环的N.sbd.H.cntdo...cntdo...cntdot.O氢键，而B分子只形成一个很强的跨环氢键。两个独立分子(A和B)之间的构象差异远远大于两个结构对应的分子(A和A，B和B)之间的差异。这两个多肽的晶体结构非常相似，由疏水侧链和极性多肽区域的平行带组成。在每个结构中，分子相互堆叠，六肽环垂直于堆叠的轴线。水分子形成分隔良好的溶剂通道，夹在多肽分子层之间，并通过广泛的氢键连接多肽。
cyclo(L-Leucyl-L-phenylalanyl-glycyl-D-phenylalanyl-L-leucyl-glycyl-) trihydrate (IV), C34H46N6O6.-3H2O, Mr = 688.8, monoclinic, P21, .alpha. = 11.720 (2), b = 36.354(4), c = 8.888 (1) .ANG., .beta. = 103.88 (1).degree., V = 3676.3 .ANG.3, Z = 4, Dx = 1.244 g cm-3, .lambda. (Cu K.alpha.) = 1.54178 .ANG., .mu. = 7.6 cm-1, F(000) = 1480, T = 138 K, final R = 0.052 for 7661 unique reflections. cyclo(L-Phenylalanyl-L-leucyl-glycyl-D-leucyl-L-phenylalanyl-glycyl-) trihydrate (V), C34H46N6O6.- 3H2O, Mr = 688.8, triclinic, P1, .alpha. = 11.668 (3), b = 19.111 (5), c = 8.527 (1) .ANG., .alpha. = 101.54 (2), .beta. = 93.42 (2), .lambda. = 94.27 (2).degree., V = 1852.4 .ANG.3, Z = 2, Dx = 1.235 g cm-3, .lambda.(Cu K.alpha.) = 1.54178 .ANG., .mu. = 7.5 cm-1 F(000) = 740, T = 138 K, final R = 0.063 for 7574 unique reflections. Peptides IV and V both have two independent conformers (molecules A andB). The peptide ring in each case contains one .beta.(I) turn and one .beta.(II'') turn. A molecules in both structures have two transannular N.sbd.H.cntdot..cntdot..cntdot.O hydrogen bonds, while B molecules form only one strong transannular hydrogen bond. The conformational differences between the two independent molecules (A and B) are much larger than the differences between the corresponding molecules of the two structures (A and A, and B and B). The crystal structures of the two peptides are very similar and consist of parallel bands of hydrophobic side chains and polar peptide regions. In each structure, molecules are stacked one over another with the hexapeptide ring lying perpendicular to the axis of the stack. The water molecules form well delimited solvent channels sandwiched between the layers of peptide molecules, and bridge the peptides through extensive hydrogen bonding.