蛋白质溶液结构及动力学的核磁共振研究

高场液相核磁共振技术作为解析高分辨率蛋白质结构的两大主要手段之一,在近二十几年的时间里得到了迅猛的发展. 一方面,随着谱仪硬件技术、核磁脉冲技术和蛋白质标记技术的不断发展,液相核磁共振技术所能够研究的蛋白质不断突破分子量的限制,可以达到几万,甚至几十万. 另一方面,液相核磁共振技术成功地应用于蛋白质分子动力学的研究中,是目前唯一能够对蛋白质多个位点同时进行动力学研究的实验方法,并且仍在不断地创新、发展和完善中. 本文从蛋白质溶液结构的解析和动力学的研究两个主要方面对液相核磁共振研究的基本方法进行简要的介绍,并结合实例介绍一些最新的研究进展.     

岩心孔隙介质中流体的核磁共振弛豫

弛豫时间是核磁共振研究中的一个重要参数,岩心孔隙介质流体的弛豫过程是自由流体弛豫机制、表面弛豫机制和流体的扩散弛豫机制共同作用的结果,它包含了丰富的孔隙和流体本身的信息. 弛豫时间和自扩散系数的测量及对弛豫时间的分析是核磁共振技术应用于岩心分析和石油勘测的重要内容.     

一体化核磁共振谱仪数据交换的实现机制

核磁共振（NMR）随着其应用领域的拓展和深入,核磁共振谱仪技术得到了不断的发展和完善^[1,2]_. 针对以往谱仪存在的一些问题,本文提出了一种一体化核磁共振谱仪数据交换的实现机制,同时提出了基于ARM（Advanced RISC Machines,先进精简指令计算机）微处理器的嵌入式操作系统软件设计方案,并给出了谱仪各功能模块的实际性能测试结果,对实验结果进行了总结和讨论.      

人参茎叶中一个新天然产物的结构研究

采用多种色谱方法从人参茎叶中分离得到一个新天然产物-达玛烷型三萜皂苷元dammar 20(22), 24-diene-3β,6α,12β-triol,并利用质谱、核磁共振谱和化学方法对此化合物进行了结构解析. 通过2D NMR（HMQC、HMBC）进行了¹H和¹³C NMR信号全归属,并纠正了文献中的个别化学位移的信号指认错误.     

拉呋替丁的波谱学数据和结构确证

对拉呋替丁的氢谱（¹H NMR）、碳谱（¹³C NMR,DEPT）、异核多键相关谱（HMBC）予以解析并进行了报道,对其所有的¹H NMR和¹³C NMR谱信号进行了归属;讨论了红外特征吸收,热差和热重分析;质谱的裂解途径和离子特征也与拉呋替丁的分子结构相符.      

扩散序谱(DOSY)实验中扩散系数维数字分辨率的影响

核磁共振二维扩散序谱（DOSY）实验测定溶液中分子自扩散系数时,扩散系数维的数据点及其数字分辨率直接影响了测定值的精度.在较系统地确定了DOSY实验本身偏差范围的基础上,本文研究了扩散系数维不同的数字分辨率对测定值的影响,包括其引入偏差的来源以及形成偏差的大小.由于不同的溶液条件下分子扩散系数的改变可直接用于表征分子结构或状态的变化,本文提出的相对数字分辨率与扩散系数相对变化值的直接比较,可直观地表明数字分辨率对扩散系数测定值的影响.     

GS-221高速摄影测量仪测角信息的采集与处理

在GS-221高速摄影测量仪中,测角信息采集与处理速度的快慢是重要性能指标之一。本文讨论了如何在尽可能短的时间内对测角信息进行采集和处理的软件实现方法。     

一种双香豆蒽衍生物的NMR研究

应用核磁共振技术（¹H NMR, ¹3C NMR, DEPT, ¹H-¹H COSY, HSQC, HMBC）,确定了7-(4-溴苯甲基)-7H-吡喃[3,2-c:5,6-c′]二香豆蒽-6,8二酮的结构,排除了其他可能结构, 准确归属了它的¹H, ¹³C信号.      

杜仲的核磁共振指纹图谱研究

核磁共振氢谱（Proton Nuclear Magnetic Resonance,¹H NMR）是中药指纹图谱中一种鉴定和控制植物中药质量的新方法．本文采用CPMG（Carr-Purcell-Meiboom-Gill）脉冲序列采集了杜仲提取物的¹H NMR谱,通过完整还原振幅频率表（Complete Reduction to Amplitude-Frequency Table,CRAFT）分析技术对杜仲指纹图谱进行特征指纹分析,将待目标合物的信号从混合物图谱中剥离出来,实现了不分离样品而分析目标化合物信息的目的,从而对杜仲的特征化合物——松脂醇二葡萄糖苷（Pinoresinol Glucoside,PDG）进行了定性和定量分析．结果显示贵阳药用植物园所得杜仲的PDG含量为0.275 6%,相对标准偏差（Relative Standard Deviation,RSD）为1.69%,与高效液相色谱（High Performance Liquid Chromatography,HPLC）定量分析结果（含量为0.269 6%,RSD为0.65%）基本一致．另外,通过NMR检测与多变量数据建模相结合分析了杜仲提取物的全指纹图谱,结果显示同一采收期不同产地的杜仲药材有显著差异,这表明该方法可用于鉴定不同产地的药材,具有一定的实用意义．     

混沌激光相关法测距系统的信号采集与处理

 混沌激光相关法测距技术可用于汽车防撞、光纤及电缆断点检测等,其中混沌信号的快速采集、存储以及处理是重要的单元技术。基于数据采集卡设计并实现了混沌激光测距系统的数据采集与处理,利用Visual Basic平台,开发了采集、存储的控制软件,并提出和编制了平均离散消除算法以实时地实现混沌信号的高信噪比相关运算。利用该采集处理系统,实验获得了低于±0.25 m的光纤断点定位精度。     

Single-scan 2D DOSY NMR spectroscopy

Spatial encoding is a particular kind of spin manipulation that enables the acquisition of multidimensional NMR spectra within a single scan. This encoding has been shown to possess a general applicability and to enable the completion of arbitrary nD NMR acquisitions within a single transient. The present study explores its potential towards the acquisition of 2D DOSY spectra, where the indirect dimension is meant to encode molecular displacements rather than a coherent spin evolution. We find that in its simplest form this extension shows similarities with methods that have been recently discussed for the single-scan acquisition of this kind of traces; still, a number of advantageous features are also evidenced by the “ultrafast” modality hereby introduced. The principles underlying the operation of this new single-scan 2D DOSY approach are discussed, its use is illustrated with a variety of sequences and of samples, the limitations of this new experiment are noted, and potential extensions of the methodology are mentioned.     

Improving pulse sequences for 3D DOSY: convection compensation

Signal overlap in the NMR dimension significantly complicates the construction and analysis of 2D diffusion-ordered (DOSY) spectra. Such problems can often be reduced or even eliminated by extending the NMR domain of a DOSY experiment into two dimensions, giving a 3D-DOSY spectrum. To date such experiments have generally sacrificed some signal-to-noise ratio and have required extensive and time-consuming phase cycling. A new family of pulse sequences with internal diffusion encoding (IDOSY) has been introduced which avoids both of these problems. It is often straightforward to incorporate convection compensation in such sequences at no cost in signal-to-noise ratio. Here, some of the problems caused by convection in DOSY are described and illustrated, and the efficacy of convection compensation in the 2DJ-IDOSY and COSY-IDOSY experiments is demonstrated.     

The DOSY Toolbox: A new tool for processing PFG NMR diffusion data

The DOSY Toolbox is a free programme for processing PFG NMR diffusion data (sometimes loosely referred to as DOSY data), distributed under the GNU General Public License. NMR data from three major manufacturers can be imported and all processing is done in a user-friendly graphical user interface. The Toolbox is completely free-standing in the sense that all necessary basic processing of NMR data (e.g., Fourier transformation and phasing) is catered for within the programme, as well as a number of methods specific to DOSY data (e.g., DOSY and SCORE). The programme is written in MATLAB^® and as such can be run on any platform, but can also run independent of MATLAB^® in a free-standing compiled version for Windows, Mac, and Linux.     

Diagnostic analysis of experimental artefacts in DOSY NMR data by covariance matrix of the residuals

Multivariate curve resolution (MCR) has been applied to separate pure spectra and pure decay profiles of DOSY NMR data. Given good initial guesses of the pure decay profiles, and combined with the nonlinear least square regression (NLR), MCR can result in good separation of the pure components. Nevertheless, due to the presence of artefacts in experimental data, validation of a MCR model is still necessary. In this paper, the covariance matrix of the residuals (CMR), obtained by postmultiplying the residual matrix with its transpose, is proposed to evaluate the quality of the results of an experimental data set. Plots of the rows of this matrix give a general impression of the covariance in the frequency domain of the residual matrix. Different patterns in the plot indicate possible causes of experimental imperfections. This new criterion can be used as diagnosis in order to improve experimental settings as well as suggest appropriate preprocessing of DOSY NMR data.     

Spectral separation of gaseous fluorocarbon mixtures and measurement of diffusion constants by F gas phase DOSY NMR

Diffusion-ordered (DOSY) NMR techniques have for the first time been applied to the spectral separation of mixtures of fluorinated gases by diffusion rates. A mixture of linear perfluoroalkanes from methane to hexane was readily separated at 25 °C in an ordinary experimental setup with standard DOSY pulse sequences. Partial separation of variously fluorinated ethanes was also achieved. The constants of self-diffusion of a set of pure perfluoroalkanes were obtained at pressures from 0.25 to 1.34 atm and temperatures from 20 to 122 °C. Under all conditions there was agreement within 20% of experimental self-diffusion constant D and values calculated by the semiempirical Fuller method.     

Improved DOSY NMR data processing by data enhancement and combination of multivariate curve resolution with non-linear least square fitting

The quality of DOSY NMR data can be improved by careful pre-processing techniques. Baseline drift, peak shift, and phase shift commonly exist in real-world DOSY NMR data. These phenomena seriously hinder the data analysis and should be removed as much as possible. In this paper, a series of preprocessing operations are proposed so that the subsequent multivariate curve resolution can yield optimal results. First, the baseline is corrected according to a method by Golotvin and Williams. Next, frequency and phase shift are removed by a new combination of reference deconvolution (FIDDLE), and a method presented by Witjes et al. that can correct several spectra simultaneously. The corrected data are analysed by the combination of multivariate curve resolution with non-linear least square regression (MCR-NLR). The MCR-NLR method turns out to be more robust and leads to better resolution of the pure components than classic MCR.     

基于CAN总线的遥测数据处理模块软件设计

随着飞行器电子综合化技术的发展,数据总线在飞行器中得到大量应用。为满足某飞行器总线系统测量的需求,本文设计了一种基于CAN总线的遥测数据处理模块。硬件部分主要由CAN总线驱动器模块、DSP数字信号处理模块、FPGA逻辑处理模块组成。软件设计包括TMS320F28335的初始化,CAN总线数据处理和外部中断处理三部分。该模块用于某飞行器双路CAN总线数据的采集及处理,并经过了多次飞行试验验证。该模块简化了系统设计,实现了高速、可靠的CAN总线遥测数据处理。     

辣椒碱与β-环糊精包合物的核磁共振研究

利用核磁共振方法研究了辣椒碱β-环糊精包合物的化学计量比、空间结构信息及其在水溶液中的自扩散系数. 通过测定不同浓度比的辣椒碱和β-环糊精混合溶液的 ¹H NMR数据,绘制Job's曲线,辣椒碱和β-环糊精的Job's曲线均在r=0.5处出现拐点. 同时测定了该包合物的2D ROESY和DOSY谱图,ROESY谱图中NOE交叉信号出现在辣椒碱的H-1~H-8和β-环糊精的H-3′、H-5′、H-6′之间,DOSY测得β-环糊精和辣椒碱形成包合物前后的表观自扩散系数. 结果表明,辣椒碱β-环糊精包合物的主客体分子的化学计量比为1∶1,辣椒碱分子的异丙基端从β-环糊精的宽口端进入疏水腔,其中H-1~H-8部分在空腔内部,包合物的自扩散系数为2.95×10^-10m²/s.     

多道ICP-AES多元素瞬时信号检测、处理集成软件的开发

介绍了多道ＩＣＰ－ＡＥＳ多元素瞬时信号检测处理集成软件的研制过程,应用该软件实现了多道ＩＣＰ－ＡＥＳ和多种瞬时进样技术在线联用的信号采集、处理。     

高效液相色谱-原子荧光光谱联用中的连续数字信号采集和处理

本文报道了利用Visual C 编写原子荧光光谱仪的数字信号采集和处理软件,成功地解决了原子荧光光谱仪作为联用技术在线检测器的数据采集问题,实现了通过计算机串口对瞬变光谱信号的连续采集和实时的曲线绘制。本工作采用Savitzky-Golay平滑、傅里叶变换滤波和小波滤噪三种数据处理技术对采集数据进行平滑和滤波,并对其处理效果进行了比较。并以镉为例,验证了高效液相色谱与国产原子荧光光谱联用应用于形态分析的可能性。