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首页> 外文期刊>Journal of pharmaceutical sciences. >Estimated pKa Values for Specific Amino Acid Residues in Daptomycin
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Estimated pKa Values for Specific Amino Acid Residues in Daptomycin

机译：达托霉素中特定氨基酸残基的估计pKa值

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摘要

Daptomycin is a cyclic lipopeptide antibiotic. The ionization constants of daptomycin have not been individually elucidated. The objective of this research is to determine the sequence-specific ionization constants of daptomycin in the monomeric state. The pH titra-tions of daptomycin were performed by nuclear magnetic resonance (NMR) spectroscopy. The sequence-specific pKa values for the four acidic residues and one aromatic amine (Kyn-13) in daptomycin were determined by two-dimensional total correlation spectroscopy ~1H NMR. From the NMR pH titration, the estimated pKa values for Asp-3, Asp-9, and methylglutamic acid (mGlu-12) were determined to be 4.2, 3.8, and 4.6 in the absence of salt, and 4.1, 3.8, and 4.4 in the presence of 150 mM NaCl, respectively. The pKa value for Asp-7 is estimated to be approximately 1.0 in the absence of salt and 1.3 in the presence of salt. The estimated Hill coefficients for Asp-7 were 0.72 and 1.31 in the absence and presence of salt, respectively. The increase in Hill coefficients from 0.72 to 1.31 with increasing salt concentration is consistent with the estimated lower pKa in the absence of salt, and suggests that a salt bridge is formed in solution possibly between Asp-7 acidic group and the neighboring Orn-6 basic group.
机译：达托霉素是一种环状脂肽抗生素。达托霉素的电离常数尚未单独阐明。这项研究的目的是确定达托霉素在单体状态下的序列特异性电离常数。达托霉素的pH滴定通过核磁共振（NMR）光谱进行。达托霉素中四个酸性残基和一个芳香胺（Kyn-13）的序列特异性pKa值通过二维全相关光谱法〜1H NMR测定。通过NMR pH滴定，在无盐情况下，Asp-3，Asp-9和甲基谷氨酸（mGlu-12）的估计pKa值分别为4.2、3.8和4.6，以及4.1、3.8和4.4。分别在150 mM NaCl存在下。在没有盐的情况下，Asp-7的pKa值估计约为1.0，在有盐的情况下，pKa值约为1.3。在无盐和有盐的情况下，Asp-7的估计希尔系数分别为0.72和1.31。随着盐浓度的增加，希尔系数从0.72增加到1.31与估计的不存在盐的较低pKa相一致，这表明在溶液中可能在Asp-7酸性基团与相邻的Orn-6碱性盐之间形成了盐桥。组。

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