共查询到20条相似文献,搜索用时 140 毫秒
1.
2.
3.
采用量子化学计算研究了磷酰化氨基酸的反应性质,包括N-磷酰氨基酸成肽反应、成酯反应、磷上酯交换反应和磷上的N→O迁移反应的机理以及计算模型和计算方法的选择,并从理论上解释了自然界选择α-氨基酸而不是β,γ-氨基酸的实验事实. 相似文献
4.
寡肽类化合物一般具有较强的生物活性,多数可作为药物或药物前体,因此成为人们的研究热点之一.目前寡肽的合成方法主要有液相法、固相法及酶促合成法,这些合成方法往往需要对氨基酸的活性基团进行选择性保护,步骤繁琐.近期研究发现,在水-醇体系中α-氨基酸被磷酰化为N-磷酰-α-氨基酸后,可发生自组装聚合肽反应;在无水条件下,N,O-二(三甲基硅基)-α-氨基酸可与磷酰化试剂如O,O-亚苯基磷酰氯反应生成N-磷酰-α-氨基酸,后者也可通过自组装反应得到二~八肽,但这些N-磷酰-α-氨基酸的制备均需使用有机磷试剂.我们发现,在无机磷试剂如PCl5等辅助下,α-氨基酸同样可以发生自组装反应,得到一系列寡聚肽,这既可为寡聚肽的合成提供一种新的方法,同时,因无机磷试剂在原始地球条件下更可能存在,因而对于揭示多肽及蛋白质的起源具有重要意义.氨基酸的自组装反应具有链锁反应的特点,因此必须控制反应条件实现对反应的控制。 相似文献
5.
6.
氨基酸和核苷的五配位磷化合物 总被引:2,自引:0,他引:2
五配位磷化合物在生物化学中起着重要作用。磷所参与的绝大多数生命化学过程,包括酶活性调节过程中蛋白质的磷酰化与去磷酰化,信息传导过程中蛋白质的磷酰化与去磷酰化,ATP的能量转移,RNA的自体切割等,其化学本质都是磷酰基转移反应。生物化学家们的研究表明,这些磷酰基转移反应都是通过五配位中间体来完成的。因此,对生物化学中五配位磷化合物的研究具有重要意义。 相似文献
7.
咪唑催化磷酰化丝,苏氨酸及其酯的活化反应 总被引:1,自引:2,他引:1
咪唑对磷酰化氨基酸的活化反应具有较强的催化作用,磷酰化丝、苏氨酸在咪唑催化下不仅能发生溶剂解反应,如磷酯交换,羧基活化成酯、成肽及磷酰基的N-O迁移等,而且还会发生分子内环化反应,对于化学性质非常稳定的磷酰化丝、苏氨酸酯在咪唑催化下也会发生上述反应,反应机理推测为丝、苏氨酸的侧链基团羟基在咪唑的存在下亲核进攻磷原子形成五配位中间体。 相似文献
8.
9.
蛋白质磷酸化是细胞内调节酶功能的一种重要的翻译后修饰 .蛋白质内酪氨酸磷酰化是目前所知道的在细胞应答外界刺激时最主要的信号传导方式 [1] .文献 [2 ]报道的酪氨酸 O-磷酰化的方法是基于亚磷酰胺化学 ,包含亚磷酸化和氧化两步 .我们在 O-磷酰化多肽的合成研究中发现 ,应用 Atherton-Todd反应可以有效地进行酪氨酸 O-磷酰化 .Atherton- Todd反应是指二烷基亚磷酸酯在四氯化碳和有机碱 (如三乙胺 )存在下转变成二烷基磷酰氯 ,从而进行胺、亚胺及肟的磷酰化 .该法曾被有效地用于在弱碱性水溶液中合成 N - (二烷基磷酰 )氨基酸和小肽 [… 相似文献
10.
ESI质谱法对黄酮-7-磷酰化氨基酸酯与溶菌酶相互作用的研究 总被引:4,自引:3,他引:1
采用电喷雾(ESI)质谱技术,研究了4种黄酮-7-磷酰化氨基酸酯与溶菌酶的弱相互作用,实验结果表明4种化合物均能与溶菌酶形成非共价复合物,在相同条件下,未检测到黄酮与溶菌酶形成的非共价复合物,说明在黄酮分子中引入N-磷酰化氨基酸,能改变黄酮的分子极性,从而使其与生物大分子之间的相互作用情况发生变化;通过改变锥孔电压,分别对4种黄酮-7-磷酰化氨基酸酯-溶菌酶复合物的耐压能力进行检测.结果显示,黄酮-7-磷酰化氨基酸酯b与溶菌酶形成的复合物最稳定,它们之间存在最强的弱相互作用. 相似文献
11.
Solvent accessibility prediction from amino acid sequences has been pursued by several researchers. Such a prediction typically starts by transforming the amino acid category (or type) information into numerical representations. All twenty amino acids can be completely and uniquely represented by 20-dimensional vectors. Here, we investigate if the amino acid space defined in this way really requires twenty dimensions. We tried to develop corresponding representations in fewer dimensions. A method for searching optimal codification schema in an arbitrary space using neural networks was developed. The method is used to obtain optimal encoding of amino acids at various levels of dimensionality, and applied to optimize the amino acid codifications for the prediction of the solvent accessibility values of the proteins using feed-forward neural networks. The traditional 20-dimensional codification seems to be redundant in solving the solvent accessibility prediction problem, since a 1-dimensional codification is able to achieve almost the same degree of accuracy as the 20-dimensional codification. Optimal coding in much fewer dimensions could be used to make the predictions of accessible surface area with almost the same degree of accuracy as that obtained by a fully unique 20-dimensional coding. The 1-dimensional amino acid codification for solvent accessibility prediction obtained by a purely mathematical way based on neural networks is highly correlated with a physical property of the amino acids, namely their average solvent accessibility. The method developed to find the optimal codification is general, although the codification thus produced is dependent on the type of estimated property. 相似文献
12.
13.
14.
15.
J Silberring P Brostedt A Ingvast F Nyberg 《Rapid communications in mass spectrometry : RCM》1991,5(12):579-581
There is evidence that even highly purified preparations of human growth hormone are not homogenous, but contain charge as well as size variants. The charge heterogeneity was suggested to be due to deamidation of the native hormone. To verify this we have applied peptide mapping followed by fast-atom bombardment mass spectrometry (FAB-MS), in order to identify fragments containing the altered amino acids. Growth hormone was purified from human pituitaries and the differently charged forms were separated by column electrophoresis in agarose suspension. The isolated components were treated with trypsin and analysed directly by FAB-MS without prior separation by reversed-phase high-performance liquid chromatography (RP-HPLC). Using this technique, approximately 80% of the hormone structure was recovered and two deamidation sites were found in the fragment T15 (FDTNSHNDDALLK). The results clearly elucidated the potential use of FAB-MS for the fast screening of other variants of the growth hormone which are known to exist. 相似文献
16.
Xiaowu Chen Dan Gao Feng Liu Xiang Gao Shujuan Wang Yufen Zhao Hongxia Liu Yuyang Jiang 《Analytica chimica acta》2014
A novel method based on the strategy of N-phosphorylation labeling is described for quantification of twenty natural amino acids in human serum by reversed-phase liquid chromatography–electrospray tandem mass spectrometry (RP-LC/ESI-MS). The derivatization reaction was easily performed in one-pot reaction under mild conditions within 30 min. The reaction mixture was then evaporated to dryness, redissolved, desalted by C18 SPE. The twenty N-phosphoryl amino acids were separated on an RP-C18 column within 20 min by isocratic elution (0.1% formic acid–acetonitrile, v/v 7:3). At the same time, multiple reaction monitoring (MRM) MS enabled quantitation of twenty natural amino with the LOD of 0.0005–0.15 μM and LOQ of 0.0020–0.5 μM in human serum. The linear range was from 0.025 to 25 μM (except Cys and Trp) with R > 0.99. The recovery range was determined to be 85.5–117.4% with the relative standard deviation (RSD) in the range of 1.3–13.9%. All twenty amino acids were successfully detected in human serum samples with the concentration from 5.7 to 577.9 μM, which indicates potential of the developed method for determination of amino acids in complex biological samples, hence for screening of amino acid metabolite related diseases. 相似文献
17.
We demonstrate a 2D NMR method which distinguishes between phosphorylated and non-phosphorylated amino acids. The method is
capable of monitoring the amino acid and site-specific enzymatic phosphorylation and dephosphorylation of peptides. The method
was developed using O-phosphorylated amino acids and its potential is shown with a peptide fragment of the myelin basic protein
(MBP). 相似文献
18.
Thebiosynthesisofnucleicacid,oneofthemostimportantbio-macromolecules,isahighlyelegantprocess,whichinvolvestheparticipationofmanyenzymesandenergycarriers,suchasATP',whilechemicalsynthesisofoligonucleotidesgenerallyinvolvescomplicatedprotectinganddeprotectingprocesses'.Inthepreviouswork,nucleotidesandoligonucleotidesweredirectlyformedacthereaction,,-ofN-(O,O-diisopropyl)phosphorylthreonineanduridineinanhydrouspyridine'.SoN-(O,O-diisopropyl)phospho-aminoacid(DIPP-aa)wasproposedasamodelcompou… 相似文献
19.
为了分析烤烟中游离氨基酸含量与烤烟香型、产地的关系,以国内14个烟草种植省份的138个调制后的烤烟中部叶片为材料,采用柱前衍生-超高效液相色谱-单重四极杆质谱法对烤烟中的20种游离氨基酸进行分析。方法表征结果显示该方法满足分析要求,适合烤烟中游离氨基酸的检测。对调制后烤烟中部叶片的游离氨基酸分析结果显示,烤烟的游离氨基酸含量在产地间差异很大(28.50%~94.20%),其中天冬酰胺、谷氨酰胺含量的相对标准偏差(RSD)超过80%;在3种典型香型(浓香型、清香型和中间香型)烤烟中,浓香型烤烟游离氨基酸含量的RSD大于其他两种香型。对同一香型的不同种植省份和同一省份不同香型的烤烟游离氨基酸分析结果显示,其含量呈现一定的规律。 相似文献
20.
Atom-centered partial charges which exactly reproduce the lowest several multipoles of a molecule's charge distribution can be obtained in a straightforward and convenient manner from the output of existing electronic structure calculations. The multipole constraint method is demonstrated by a computation of partial charges for the twenty common amino acids. The electron density employed here, derived from a semiempirical MNDO calculation, incorporates Slater-type orbitals which imbue it with the exponential fall-off vital to electronic tunneling calculations. In addition, a procedure based on these charges is described which divides the original electron density into two components, a large component with a simple electrostatic potential, and a much smaller residual whose several lowest multipoles vanish. 相似文献