Liu Maili

Production of Hyperpolarized129Xe Gas Without Nitrogen by Optical Pumping at133CsD2Line in Flow System

We report production of hyperpolarized 129Xe gas via spin-exchange with optically pumped Cs atoms at the D2 line, achieved at low magnetic field in a flow system and in the absence of nitrogen gas. The nuclear spin polarization of hyperpolarized 129Xe gas is enhanced by a factor of 10000 compared to that without optical pumping under the same condition, which corresponds to polarization of about 2.66%. Due to the high spin polarization, the radiation damping of hyperpolarized 129Xe gas has also been observed in the flow system.

Single-Shot Magnetic Resonance Imaging of a Moving Object Based on the High-Speed Spiral-Scan Echo Planner Technique at 4.7 T

The single-shot spiral magnetic resonance imaging (MRI) technique was implemented and optimized on a Bruker Biospec47/30 scanner. The technique includes the pulse sequence for generation and detection of the k-space MRI signal (free induction decay (FID)), and PC-based programs for the data grid and image reconstruction. The temporal resolution is 70 ms (14 images per second), which consists of a data acquisition time as short as 13.7 ms, a spin-echo time of 13.6 ms and a magnetization recovery time of 43 ms. This makes it possible to take real-time images of moving objects. The technique is demonstrated using a pendulum (tube) filled with water.

蛋白质INSM1中的锌指结构域ZF(4-5)的表达、纯化与表征

胰岛素瘤相关蛋白1（INSM1）是一类转录调节蛋白，通过其C-端的锌指结构域（氨基酸250-510）来识别序列特异性的DNA分子．INSM1的C-端包含有5个串联的锌指结构域，然而这些结构域的结构及其如何识别DNA的分子机制目前仍不清楚．通过重组构建的质粒pET-32m-INSM1(424-497)表达的蛋白质（氨基酸424-497）包含了最后两个锌指结构域4和5，简称为ZF(4-5)．该文详细研究了蛋白质ZF(4-5)的诱导表达条件，得到了较高产率的纯化蛋白．核磁共振（NMR）谱和圆二色谱（CD）揭示了Zn2+对稳定锌指蛋白结构的必要性，以及C2H2-Zn2+结合的组氨酸呈现为.-异构方式．

Characterizations of protein oligomeric states in solution

Protein oligomeric state characterization is a prerequisite for its structural and functional studies. Many methods are currently used in wet labs for this characterization including native polyacrylamide gel electrophoresis (Native-PAGE), size exclusion chromatography (SEC), light scattering (LS), and analytical ultracentrifugation. These methods are sometimes carried out qualitatively or semi-quantitatively to give only imprecise information. In addition to these techniques, solution nuclear magnetic resonance (NMR) and native mass spectrometry (Native-MS) are also capable of analyzing protein oligomeric states. In order to compare results of SEC to results from these last two techniques, we studied the oligomeric states of two proteins, the monomeric protein TGIF1-HD and the dimeric protein SP_0782. Our research results indicated that SEC and NMR can be used to estimate the molecular weight of the dominant oligomer, and also to roughly estimate the relative contents of additional oligomeric forms. Native-MS was able to complementary quantitative assessment of the amounts of each oligomeric state based on their mass to charge ( m / z ) ratio for many proteins.

Progress in biomolecular cryo-electron microscopy

Biomolecular structure is the basis of discovering life procedure on atom level, exploring disease mechanism, and developing targeting drugs. The main techniques to resolve biomolecular structure are X-ray crystallography, NMR spectroscopy, and cryo-electron microscopy (Cryo-EM). Recently, there was dramatical progress in Cryo-EM, the resolution of which reached atom level (ca. 3 A). The Nobel Prize in Chemistry 2017 was awarded to three scientists for developing cryo-electron microscopy for the high-resolution structure determination of biomolecules in solution. This paper introduced the scientific background and application perspective of cryo-electron microscopy.

PDI抑制 α -synuclein纤维化聚集作用机制研究

天然无结构蛋白α-synuclein在帕金森症（PD）患者脑部的路易小体中异常聚集，被认为是引起PD的重要原因之一，但是目前关于α-synuclein的聚集机制仍没有定论.蛋白质二硫键异构酶（PDI）是细胞内质网中重要的分子伴侣蛋白，能够阻止内质网中无结构蛋白的聚集.在PD患者的脑细胞内发现PDI过量表达，且酶活性位点半胱氨酸被亚硝基化使其活性受到抑制.体外实验证明，PDI能够抑制α-synuclein的聚集，但其具体的分子机制还不清楚，研究PDI抑制α-synuclein聚集的具体机制可能对于PD治疗有重要意义.该文利用核磁共振（NMR）方法研究了α-synuclein与PDI的相互作用，发现α-synuclein与PDI的结合位点位于α-synuclein的N端；将PDI所有的6个半胱氨酸突变成丝氨酸，得到突变体PDI C-S，发现α-synuclein与PDI C-S的结合位点则位于其C末端；荧光实验结果表明突变体PDI C-S对α-synuclein纤维化聚集的抑制作用减弱，说明PDI抑制α-synuclein的纤维化聚集主要是通过与α-synuclein的N端残基结合来实现的.

离子对人血清白蛋白影响的 1 H NMR研究

人血清白蛋白（HSA）上有很多的结合位点，对药物及内源性物质的运输有很重要的作用.由于HSA分子量大且结构复杂，核磁共振（NMR）谱图信号重叠严重，因此使用常规的NMR技术很难获得天然丰度HSA上结合位点的信息.我们通过新的谱编辑技术，将横向弛豫加权（T2W）与RD-WaterLOGSY技术相结合（即T2W-RD-WaterLOGSY），观察到了天然丰度HSA表面的一些明显的特征信号，且这些信号的分辨率较高；通过pH滴定和2D 1H-1H TOCSY实验，我们对观察到的信号做了初步指认，发现部分信号来自于HSA表面的组氨酸；然后，我们通过这些特征信号研究了金属离子与HSA之间的相互作用.结果表明该技术可用于简化天然丰度HSA的谱线，在不对HSA进行突变的情况下，能反映了Zn2+与HSA的强结合作用以及结合位点等信息.