CONFORMATIONS OF CIS-4-FLUORO-L-PROLINE AND TRANS-4-FLUORO-L-PROLINE IN AQUEOUS-SOLUTION
CONFORMATIONS OF CIS-4-FLUORO-L-PROLINE AND TRANS-4-FLUORO-L-PROLINE IN AQUEOUS-SOLUTION
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DOI：
10.1021/ja00798a046
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发表时间：
1973-01-01
影响因子：
15
通讯作者：
MCLEOD, RS
中科院分区：
文献类型：
--
作者：
GERIG, JT;MCLEOD, RS
分析了顺式和rz-ons-4-氟- l -脯氨酸两种亚胺酸的高分辨率质子和氟磁共振波谱。邻域耦合常数与kar -plus型方程相结合，确定了每个体系中prolinering的构象性质。这两个分子都是包膜构象；存在一个单一的，强优势构象同分异构体与氟原子在一个轴向的数据表明，为每个化合物。通常出现在蛋白质结构中的环状亚胺酸只有l -脯氨酸（la）和4-羟基-l -脯氨酸（Ib），因此这些分子的构象，R= H b， R= OH c， R= F的性质特别令人感兴趣。虽然4-羟基- l -脯氨酸的顺式和反式异构体已经通过pmr光谱在溶液中进行了检测，但先前对五元脯氨酸环的研究主要是晶体学测定。这些研究表明，未取代和4-单取代的脯氨酸环的总体趋势是皱褶，碳C7 0.4-0.6 Á在被Q、N、Ca和€ß原子占据的平面外。这个褶皱的原子可能在平面以下，因此指向羰基，如在脯氨酸二水合物铜5和(反式-羟基- l -脯氨酸1·9中发现的那样，也可能在平面以上，指向car-羧基。后一种环状构象的例子有l -脯氨酸和c/s-4-羟基- l -脯氨酸。一些含有脯氨酸的肽也被发现在C710-12位皱褶，尽管在一些取代的脯氨酸和一些pep-中
High-resolution proton and fluorine magnetic resonance spectra of the two-imino acids, cis-and rz-ons-4-fluoro-L-proline, have been analyzed. The vicinal coupling constants are used in conjunction with a Kar-plus-type equation to ascertain the conformational properties of the prolinering in each system. Both molecules are found to be in envelope conformations; theexistence of a single, stronglydominant conformational isomer with the fluorine atom in an axial orientation is indicated for each compound by the data. he only cyclic-imino acids which commonly appear in protein structures are L-proline (la) and 4-hydroxy-L-proline (Ib), and as a result the conforma-la, R= H b, R= OH c, R= F tional properties of these molecules are of particular interest. Previous studies of the five-memberedproline ring have largely been crystallographic determinations, 1-8 although the cis and trans isomers of 4-hydroxy-L-proline have been examined in solution by pmr spectroscopy. 9 These investigations show the general tendency of the unsubstituted and 4-monosubstituted proline ring to be puckered, with carbon C7 0.4-0.6 Á out of the plane occupied by the Q, N, Ca, and€ ß atoms. This puckered atom may be below the plane, and thereby oriented trans to the carbonyl group, as found in copper prolinedihydrate5 and (rans-hydroxy-L-proline1· 9 or may lie above the plane, cis to the car-boxyl group. Examples of this latter ring conforma-tion are afforded by L-proline1 2 3and c/s-4-hydroxy-L-proline. A number of proline-containing peptides have also been found to be puckered at C710-12 al-though in several substituted prolines andin some pep-