寡肽Asterin B和C溶液构象的NMR研究1: ^1H NMR归属及构象特征

Asterin B和C是从紫菀中分得的两个寡肽, 本文利用2D-NMR技术归属了它们的^1H NMR谱线, 并讨论了它们的构象特征。为进一步采用NMR和分子动力学(MD)方法研究它们的溶液构象奠定了基础。     

NMR和肽在溶液中的构象

了解肽在溶液中的构象一直是多肽化学家们极感兴趣的一个研究领域,这是因为,肽在溶液中的构象同生物功能之间很可能存在着某种联系,而要了解这种联系,首先必须知道某个肽在溶液中的真实构象。但是,在NMR光谱产生以前,肽在溶液中的构象的研究一直停留在定性的水平上。直到六十年代,高分辨NMR     

群多普利溶液构象的NMR研究

采用1D和2D NMR技术对血管紧张素转化酶抑制剂群多普利在CDCl₃溶液中存在的两种构象进行了结构解析, 并结合分子动力学和密度泛函理论方法对其进行了结构的几何优化和能量计算. 结果表明, 群多普利因分子中酰胺键的旋转而形成反式构象A和顺式构象B, 两种构象的能量差为6.35 kJ/mol, 且顺式构象为该药物的优势构象.     

采用动态NMR对8-C-glucosyl-prunetin构象研究

采用动态NMR方法,对从海南黄檀中分得的8-C-glucosyl-prunetin及其它7位 上羟基烷基化了的8－C苷异黄酮的构象进行了研究。结果表明,在8－C苷异黄酮中 ,当7位上羟基烷基化了时,由于1"-C(sp~3)-8C(sp~2)单键旋转受阻,产生两种构 象异构体。同时,借助分子力场（MM）计算方法,确定了8-C-glucosyl-prunetin 两种构象异构栓中的优势构象,即为1"-H与7－OCH_3位于同侧。由低能量构象转化 为高能量构象所需活化能为75.66 kJ/mol。这一结果与动态NMR实验计算的71. 48kJ/mol活化自由能数值相符。     

寡肽Asterin B和C溶液构象的NMR研究 Ⅱ. NMR及分子动力学模拟

利用NMR和分子动力学方法研究了寡肽Asterin B和C的溶液构象。结果表明,Asterin B在溶液中形成了某种非氢键的转角结构, 并由残基间的疏水相互作用使整个分子具有两亲性, 这种结构特征可能和其生物活性有关。并进一步讨论了这种结构的形成在蛋白质卷曲的起始过程中的意义。而Asterin C在溶液中柔性较大, 存在多种构象的平均。     

寡肽Asterin B和C溶液构象的NMR研究 Ⅱ. NMR及分子动力学模拟

利用NMR和分子动力学方法研究了寡肽Asterin B和C的溶液构象.结果表明,Asterin B在溶液中形成了某种非氢键的转角结构,并由残基间的疏水相互作用使整个分子具有两亲性,这种结构特征可能和其生物活性有关.并进一步讨论了这种结构的形成在蛋白质卷曲的起始过程中的意义.而Asterin C在溶液中柔性较大,存在多种构象的平均.     

NMR测定生物分子的结构和构象

研究分子在溶液中的行为一事主要属于核磁共振波谱学的范畴。NMR可用来测定生物分子的一级结构,可是这一技术最大的用途是研究分子以至于大分子的构象。如分子结构已知,NMR研究工作的第一步也是最关键的一步就是归属全部谱峰。对于中等大小或更大分子的~1H谱说来,即使在高场谱仪上,某些部分仍然     

α-单取代环十二酮构象的研究

利用分子力学计算，单晶X射线分析和~1H NMR技术研究了α-单取代环十二酮 的构象。结果表明，它们的优势构象的环骨架仍是[3333]构象，而羰基则在2-C位 置上。在晶体中，它们的优势构象为α－角顺取代[3333]-2-酮构象，而在溶液中 则取α－角顺取代和α－边外取代[3333]-2-酮两种构象，且两种构象处于动力学 平衡之中，以α－边外取代[3333]-2-酮构象占优势。     

α，α'-顺式二取代环十二酮的构象

利用分子力学计算，1~H NMR，(13)~C NMR和单晶X射线衍射分析技术研究了α -α'-顺式二表明，它们的优势构象骨架仍是[333]-2-酮，在晶体和溶液中，它们 的优势构象均为。α-角顺，α'-边外构象．在溶液中，相同取代基的α，α'-顺 式二取代环十二酮存在两种互为镜象的[3333]-2-酮对映体构象，学平衡之中；不 同取代基的α，α'-顺式二取代环十二酮存在体积较大的基团为边外取代的[3333] -2-酮和角顺取代的[3333]-2-酮两种构象，两种构象也处于动力学平衡之中，以较 大基团为边外取代的[3333]-2酮构象占优势.     

α，α'-顺式二取代环十二酮的构象

利用分子力学计算，1~H NMR，(13)~C NMR和单晶X射线衍射分析技术研究了α -α'-顺式二表明，它们的优势构象骨架仍是[333]-2-酮，在晶体和溶液中，它们 的优势构象均为。α-角顺，α'-边外构象．在溶液中，相同取代基的α，α'-顺 式二取代环十二酮存在两种互为镜象的[3333]-2-酮对映体构象，学平衡之中；不 同取代基的α，α'-顺式二取代环十二酮存在体积较大的基团为边外取代的[3333] -2-酮和角顺取代的[3333]-2-酮两种构象，两种构象也处于动力学平衡之中，以较 大基团为边外取代的[3333]-2酮构象占优势.     

RUBIDIUM, a program for computer-aided assignment of two-dimensional NMR spectra of polypeptides.

Taking advantage of the rule-based expert system technology, a program named RUBIDIUM (Rule-Based Identification In 2D NMR Spectrum) was developed to accomplish the automatic 1H NMR resonance assignments of polypeptides. Besides noise elimination and peak selection capabilities, RUBIDIUM detects the cross-peak patterns of amino acid residues in the COSY spectrum, assigning these patterns to amino acid types, performing sequential assignments using combined COSY/NOESY spectra, and finally, achieving the total assignment of the 1H NMR spectrum.     

Complete (1)H and (13)C NMR assignments of two new trans-clerodane diterpenoids from Otostegia limbata

Two new tricyclic trans-clerodane diterpenoids trivially named as ballotenic acid A (1) and ballodiolic acid A (2) have been isolated from ethyl acetate fraction of Otostegia limbata. The structure assignments are based on (1)H and (13)C NMR spectra, 2D NMR (HMQC, HMBC, COSY, NOESY and NOE) techniques and comparison with the literature data.     

聚芳醚酮大环化合物的核磁共振谱解析

利用一维ＮＭＲ方法研究了新型聚芳醚酮大环化合物的影响，用二维同核＾１Ｈ－＾１Ｈ ＣＯＳＹ和＾１３Ｃ－＾１Ｈ ＣＯＳＹ实验方法以及类似物质标准谱图的比较，对一维ＮＭＲ谱峰进行了归属。     

Complete 1H- and 13C NMR assignments of saponins from roots of Gypsophila trichotoma Wend

The assignments of 1H and 13C NMR spectra of two new aminoacyl triterpene saponins from roots of Gypsophila trichotoma Wend. are reported. In addition to 1D NMR methods, 2D NMR techniques (COSY, TOCSY, ROESY, HSQC, HMBC, and HSQC-TOCSY) were used for the assignments. The structures were completed by analysis of HR-ESI-MS and ESI-MS(n).     

A Two-Dimensional 1H NMR Approach for Peptide Backbone Assignments: Gramicidin S

Two-dimensional NMR spectra of gramicidin S have been measured. With the combination of COSY (through bond interaction) and NOESY (through space interaction) spectra, it is possible to identify amino acid residues sequentially. It is found that the phase-sensitive 2D technique is superior to the absolute value mode. A double quantum filtering technique could be combined with phase-sensitive COSY experiments to obtain the optimum results.     

Structural and spectral assignment of a new diterpenoid isolated from Ballota undulata and a complete (1)H and (13)C NMR data assignment for three other structurally related compounds

The structure of 3beta-hydroxyballotinone, a new labdane diterpenoid isolated from Ballota undulata, has been established by NMR spectroscopic studies. In addition, complete and unambiguous assignments of the (1)H and (13)C NMR spectra of three other already known labdanes (ballotinone, ballonigrin and ballonigrinone) isolated from the same source have been achieved. The assignments are based on 2D shift-correlated (1)H--(1)H COSY, (1)H--(13)C gHSQC [(1)J(C,H)] and (1)H--(13)C gHMBC [(n)J(C,H) (n = 2 and 3)], and NOE experiments.     

Total assignment of 1H and 13C NMR spectra of three triterpene saponins from roots of Silene vulgaris (Moench) Garcke

The assignments of ¹H and ¹³C NMR spectra for three new triterpene saponins from Silene vulgaris (gypsogenin 3‐O‐glucuronide, quillaic acid 3‐O‐glucuronide, and gypsogenin 3‐O‐glycoside) are reported. In addition to 1D NMR methods, 2D NMR techniques (COSY, HSQC, HMBC, and HSQC‐TOCSY) were used for the assignments. Copyright © 2002 John Wiley & Sons, Ltd.     

Unambiguous NMR spectral assignments of salvinorin A

The complete assignments of the (1)H and (13)C NMR spectra of the hallucinogenic neoclerodane diterpenoid salvinorin A were determined in three different NMR solvents using HSQC, HMBC and COSY. Solvent systems are described that allow the resolution of all (1)H signals. Virtual coupling was observed for the protons at C-2, C-3 and C-4 in the 600 MHz (1)H spectrum in CDCl(3). The complete assignments of the (1)H and (13)C NMR spectra of salvinorin B are also reported.     

酞侧基聚芳醚酮的核磁共振研究(Ⅰ)──链结构及NMR谱的归属

用1D NMR方法研究酞侧基聚芳醚酮(PEK-C)链结构,用二维同核化学位移相关与二维异核化学位移相关实验方法对1D NMR谱峰进行归属,探讨了二维异核远程相关实验在缩聚高分子研究中的应用,为PEK-C修饰机理以及共混相容机理的研究提供重要信息。溶液NMR谱图数据表明,PEK-C具有较规整的链结构。     

酞侧基聚芳醚砜的核磁共振研究──PES－C的氢谱归属及碳谱峰的确认

用１３Ｃ－ＮＭＲ谱和二维异核化学位移相关谱（ＨＥＴＣＯＲ）归属了酞侧基聚芳醚砜（ＰＥＳ－Ｃ）的１Ｈ－ＮＭＲ谱峰，并经二维同核化学位移相关谱（ＣＯＳＹ）验证．对原１３Ｃ－ＮＭＲ谱峰归属作了部分修正．二维同核及异核相关谱为ＰＥＳ－Ｃ的碳、氢核磁谱峰归属提供了重要信息．由ＰＥＳ－Ｃ的核磁谱图可见其链结构的规整性