Time-Resolved Chemically Induced Dynamic Nuclear Polarization of Biologically Important Molecules

In this work, we review the hyperpolarization technique named chemically induced dynamic nuclear polarization (CIDNP), focusing on the time-resolved variant of this method and its biological applications. We introduce the main principles of polarization formation in liquids at high magnetic fields, provided by the so-called spin sorting mechanism. Applications of CIDNP to studying fast reactions of short-lived free radicals of biologically important molecules are discussed, as well as the potential of the method to probe the structure and magnetic parameters of such radicals. We also explain the principles of protein CIDNP and discuss applications of time-resolved CIDNP to studies of protein structure and dynamics.     

基于数值计算模拟的仿真核磁共振波谱仪开发

核磁共振（NMR）波谱是研究有机分子结构的重要工具之一，其设备昂贵、仪器数量有限、科研机时安排紧凑、教学实验机时有限；若学生的NMR理论和实验基础较为薄弱，则易发生误操作损坏设备或降低设备性能；另外，NMR实验涉及流程较多、教学耗时较长.因此，针对学生的NMR实验教学难以广泛开展.为将虚拟技术更好地用于辅助NMR实验教学，本文基于数值模拟仿真技术，开发了具备真实NMR波谱仪基本功能的仿真NMR波谱仪——VMRS1.0软件.VMRS1.0软件可实现真实NMR实验须进行的调谐匹配、匀场、锁场、射频脉冲调节、原始数据采集等操作步骤，以及快速傅里叶变换、相位校正、自动寻峰、积分、测距、化学位移校正等基本数据处理功能；除简单的1D ¹H和¹³C NMR波谱采集和数据处理外，还可模拟去偶、DEPT、HSQC等相对复杂的实验；另外，该软件可自行虚拟编辑¹H或¹³C NMR实验样品.VMRS1.0软件摆脱硬件条件的限制，实现了与真实NMR实验类似的教学效果，可以让学生通过反复操作调试，更充分地掌握NMR基本原理和实验技能，再配合在真实NMR谱仪上的少量实际操作，可达到更加令人满意的实验教学效果.     

原子核结合能的协方差分析

以Weizs?cker公式为基础,使用协方差分析的研究方法,重新计算了原子核结合能中的体积项、表面项等5个系数,使原子核的结合能平均误差降至最低。在此基础上,利用Fattoyev给出的协方差方法,给出了各项系数的误差范围、各项系数与原子核结合能之间的关联系数、各项系数之间的关联系数。研究表明,原子核的结合能与对称能、表面能、库仑能有很大关系,而且对称能系数的误差很大,这里隐含着3个重要的物理规律:原子核可能存在四极形变;库仑能的大小可能因为四极形变而改变;可能存在中子皮、质子皮等影响对称能的大小。可以通过该项研究,对比系数间的关联性,合并减少系数的个数;得到结合能与体积项、表面项、对称能之间的密切程度等信息,为得出更为精确的原子核质量提供理论依据。     

Structural Insights into Peptides Bound to the Surface of Silica Nanopores

The structure and surface functionalization of biologically relevant silica-based hybrid materials was investigated by 2D solid-state NMR techniques combined with dynamic nuclear polarization (DNP). This approach was applied to a model system of mesoporous silica, which was modified through in-pore grafting of small peptides by solid-phase peptide synthesis (SPPS). To prove the covalent binding of the peptides on the surface, DNP-enhanced solid-state NMR was used for the detection of ¹⁵N NMR signals in natural abundance. DNP-enhanced heterocorrelation experiments with frequency switched Lee–Goldburg homonuclear proton decoupling (¹H–¹³C and ¹H–¹⁵N CP MAS FSLG HETCOR) were performed to verify the primary structure and configuration of the synthesized peptides. ¹H FSLG spectra and ¹H-²⁹Si FSLG HETCOR correlation spectra were recorded to investigate the orientation of the amino acid residues with respect to the silica surface. The combination of these NMR techniques provides detailed insights into the structure of amino acid functionalized hybrid compounds and allows for the understanding for each synthesis step during the in-pore SPPS.     

基于神经网络拟合的腹部化学交换饱和转移成像

磁共振成像（Magnetic Resonance Imaging，MRI）化学交换饱和转移（Chemical Exchange Saturation Transfer，CEST）技术在临床诊断中展现了巨大的潜力，但在腹部成像中受到主磁场偏移量大的挑战，而且利用传统的非对称性分析法得到的酰胺质子转移（Amide Proton Transfer，APT）成像对比度受到核奥氏增强（Nuclear Overhauser Enhancement，NOE）效应的干扰.本文提出了一种基于神经网络拟合的CEST后处理方法，对每个像素采集得到的Z谱特征进行识别，不需要额外序列扫描即可得到背景参考Z谱与主磁场偏移量，用以校正和获得理想的Z谱，并进一步分离得到源自APT效应与NOE效应的信号.鸡蛋清和健康志愿者腹部成像结果显示，本文提出的基于神经网络的CEST后处理方法效果较好.     

1H NMR based metabolic profiling in Crohn's disease by random forest methodology

The present study was designed to search for metabolic biomarkers and their correlation with serum zinc in Crohn's disease patients. Crohn's disease (CD) is a form of inflammatory bowel disease that may affect any part of the gastrointestinal tract and can be difficult to diagnose using the clinical tests. Thus, introduction of a novel diagnostic method would be a major step towards CD treatment. Proton nuclear magnetic resonance spectroscopy (¹H NMR) was employed for metabolic profiling to find out which metabolites in the serum have meaningful significance in the diagnosis of CD. CD and healthy subjects were correctly classified using random forest methodology. The classification model for the external test set showed a 94% correct classification of CD and healthy subjects. The present study suggests Valine and Isoleucine as differentiating metabolites for CD diagnosis. These metabolites can be used for screening of risky samples at the early stages of CD diagnoses. Moreover, a robust random forest regression model with good prediction outcomes was developed for correlating serum zinc level and metabolite concentrations. The regression model showed the correlation (R²) and root mean square error values of 0.83 and 6.44, respectively. This model suggests valuable clues for understanding the mechanism of zinc deficiency in CD patients. Copyright © 2014 John Wiley & Sons, Ltd.     

Projectile spectator proton production in 84Kr-emulsion interactions at 1.7 A GeV

The multiplicity distribution of projectile protons and multiplicity correlations between black particles, grey particles, shower particles, compound particles, heavily ionized track particles, projectile helium fragments and projectile spectator protons in <'84>Kr-emulsion collisions at 1.7 A GeV are investigated. It is found that the projectile spectator proton multiplicity distribution becomes broader with increasing target mass. The average multiplicity of shower particles and compound particles strongly depends on the number of projectile spectator protons, but the average multiplicity of black particles, grey particles and heavily ionized track particles weakly depends on the number of projectile spectator protons. The average multiplicity of projectile helium fragments increases linearly with increasing numbers of projectile spectator protons. Finally, the multiplicity distribution of projectile spectator protons obeys a KNO type of scaling law.     

Evaluation and determination of the cyclofructans–amino acid complex binding pattern by electrospray ionization mass spectrometry

The noncovalent complex interactions between cyclofructans, a new class of cyclic oligosaccharide hosts, and various amino acids have been characterized by means of electrospray ionization mass spectrometry and nuclear magnetic resonance. The 1 : 1 stoichiometry of cyclofructans and amino acid complexes was confirmed by their mass‐to‐charge ratio in positive mode. Cyclofructans (CFs)–amino acid complexes and cyclodextrin–amino acid complexes exhibited distinctive different fragment behaviors in collision‐induced dissociation experiments. Coupled with the results of ¹H NMR and nuclear overhauser effect spectroscopy, cyclofructan–amino acid complexes were deduced to be rim complexes via formation hydrogen bonding and ion–dipole forces. The interaction pattern could be controlled by changing the pH condition. In neutral solution, amino acids are located on the positive side of CFs, although moved to the negative side pocket constructed by 3‐OH oxygen of furanose ring and the crown ether oxygen in acid condition. In addition, theory calculation for geometry optimization of Trp and CFs was performed, which was in good agreement with the experimental results. Copyright © 2014 John Wiley & Sons, Ltd.