Hyperpolarization of Nitrogen‐15 Schiff Bases by Reversible Exchange Catalysis with
<i>para</i>
‐Hydrogen
作者:Angus W. J. Logan、Thomas Theis、Johannes F. P. Colell、Warren S. Warren、Steven J. Malcolmson
DOI:10.1002/chem.201602393
日期:2016.7.25
NMR with thermal polarization requires relatively concentrated samples, particularly for nuclei with low abundance and lowgyromagneticratios, such as 15N. We expand the substrate scope of SABRE, a recently introduced hyperpolarization method, to allow access to 15N‐enriched Schiff bases. These substrates show fractional 15N polarization levels of up to 2 % while having only minimal 1H enhancements
A Complete Set of NMR Chemical Shifts and Spin−Spin Coupling Constants for <scp>l</scp>-Alanyl-<scp>l</scp>-alanine Zwitterion and Analysis of Its Conformational Behavior
two-dimensional vibrational wave function was constructed and used for determination of the main chain torsion angle dispersions and conformational averaging of the NMR shifts and couplingconstants. The quantum description of the conformational dynamics based on the density functional theory and a polarizable continuum solvent model agrees reasonably with classical molecular dynamics simulations using explicit
借助稳定同位素 ((15)N 和 (13)C) 标记,获得了水溶液中 L-丙氨酰-L-丙氨酸的两性离子形式的完整化学位移和间接自旋-自旋耦合常数。在与 ab initio (DFT) 计算值比较的基础上讨论了 NMR 参数对分子几何形状的不同敏感性。构建绝热二维振动波函数并用于确定主链扭转角色散和核磁共振位移和耦合常数的构象平均。基于密度泛函理论和可极化连续溶剂模型的构象动力学量子描述与使用显式溶剂的经典分子动力学模拟合理一致。结果一致证明水溶液中存在一种具有平衡主链扭转角值(psi = 147 度,varphi = -153 度)的单一形式,与之前在 X 射线研究中发现的接近。在正常温度下,扭转角可以围绕其平衡值变化约 10 度,但这只会导致 NMR 参数的微小修正。涉及α-碳和氢原子的主链重原子化学位移和自旋-自旋耦合常数似乎对肽结构预测最有用。在正常温度下,扭转角可在其平衡值附近变化约
Isobaric Stable Isotope N‐Phosphorylation Labeling (iSIPL) for Ultrasensitive Proteome Quantification
A novel isobaric phosphorus reagent enables the accurate quantitative proteome analysis and peptide sequencing with high sensitivity. The reporter ion clusters with characteristic P−N bonds were efficiently generated with very high intensities for protein quantification.
Biocatalytic reductive amination as a route to isotopically labelled amino acids suitable for analysis of large proteins by NMR
作者:Jack S. Rowbotham、Jake H. Nicholson、Miguel A. Ramirez、Kouji Urata、Peter M. T. Todd、Gogulan Karunanithy、Lars Lauterbach、Holly A. Reeve、Andrew J. Baldwin、Kylie A. Vincent
DOI:10.1039/d3sc01718d
日期:——
and easy to use H2-driven biocatalytic platform for the enantioselective incorporation of 2H-atoms into amino acids. By combining the biocatalytic deuteration catalyst with amino acid dehydrogenase enzymes capable of reductive amination, we synthesised a library of multiply isotopically labelled amino acids from low-cost isotopic precursors, such as 2H2O and 15NH4+. The chosen approach avoids the use
我们展示了一种原子效率高且易于使用的 H 2驱动生物催化平台,用于将2 个H 原子对映选择性掺入氨基酸中。通过将生物催化氘化催化剂与能够还原胺化的氨基酸脱氢酶相结合,我们从低成本同位素前体(例如2 H 2 O 和15 NH 4 + )合成了多重同位素标记的氨基酸库。所选择的方法避免使用预先标记的2 H-还原剂,因此大大简化了产品清理。值得注意的是,该策略使得2 H、15 N 和不对称中心能够在良性条件下以完全选择性的一步引入到分子位点,并且具有接近 100% 的原子经济性。该方法有利于半克规模的氨基酸同位素体的制备。这些氨基酸在分析生命科学中具有广泛的适用性,特别是蛋白质的核磁共振光谱分析。为了证明该方法对蛋白质 NMR 化学家工作流程的好处,我们制备了L -[α- 2 H, 15 N, β- 13 C]-丙氨酸并将其集成到大型 (>400 kDa) 热休克中蛋白质寡聚物,随后可通过甲基-TROSY
Stereoselective synthesis of stable isotope-labeled L-α-amino acids: Electrophilic amination of Oppolzer's acyl sultams in the synthesis of L-[15N]alanine, L-[15N]valine, L-[15N]leucine, L-[15N]phenylalanine and L-[1-13C, 15N]valine
Using 1-chloro-1-[N-15]nitrosocyclohexane, we have prepared five L-[alpha-N-15]amino acids. The stereoselective electophillic hydroxyamination of (S)-acylbornane-10,2-sultams, followed by Zn-o/H+ reduction, and alkaline cleavage of the chiral auxiliary, gave the amino acids in 97.2-99.5% e.e. By starting with labeled (S)-acylbornane-10,2-sultams this stereoselective route could be to prepare many C-13 and/or N-15 isotopomers of alpha-amino acids.