高效液相色谱法测定低聚果糖

提出用高效液相色谱法（ Ｈ Ｐ Ｌ Ｃ）, Ｂｏｎｄａｐａｋ Ｎ Ｈ２ 柱为分析柱,乙腈—水（３∶１, Ｖ／ Ｖ）为流动相,示差折 光仪为检测器,一次进样能同时测定低聚果糖样品中的果糖、蔗糖、蔗果三糖（ Ｇ Ｆ２ ）、蔗果四糖（ Ｇ Ｆ３ ）、蔗果五糖（ Ｇ Ｆ４ ）、蔗果六糖（ Ｇ Ｆ５ ）等。本法测定了样品“博爱生命素”和“火麻仁内清液”,所得结果良好,变异系数为 ０９ ％ ～１５ ％ ,线性相关系数 ｒ 为 ０９９９０～０９９９９。     

Identification of Low‐Molecular‐Weight Compounds Inhibiting Growth of Corynebacteria: Potential Lead Compounds for Antibiotics

The bacterial genus Corynebacteria contains several pathogenic species that cause diseases such as diphtheria in humans and “cheesy gland” in goats and sheep. Thus, identifying new therapeutic targets to treat Corynebacteria infections is both medically and economically important. CG2496, a functionally uncharacterized protein from Corynebacterium glutamicum, was evaluated using an NMR ligand‐affinity screen. A total of 11 compounds from a library of 460 biologically active compounds were shown to selectively bind CG2496 in a highly conserved region of the protein. The best binder was identified to be methiothepin (K_D=54±19 µM ), an FDA‐approved serotonin receptor antagonist. Methiothepin was also shown to inhibit the growth of C. glutamicum, but not bacteria that lack CG2496 homologs. Our results suggest that CG2496 is a novel therapeutic target and methiothepin is a potential lead compound or structural scaffold for developing new antibiotics specifically targeting Corynebacteria.     

Drug Screening Boosted by Hyperpolarized Long‐Lived States in NMR

Transverse and longitudinal relaxation times (T_1ρ and T₁) have been widely exploited in NMR to probe the binding of ligands and putative drugs to target proteins. We have shown recently that long‐lived states (LLS) can be more sensitive to ligand binding. LLS can be excited if the ligand comprises at least two coupled spins. Herein we broaden the scope of ligand screening by LLS to arbitrary ligands by covalent attachment of a functional group, which comprises a pair of coupled protons that are isolated from neighboring magnetic nuclei. The resulting functionalized ligands have longitudinal relaxation times T₁(¹H) that are sufficiently long to allow the powerful combination of LLS with dissolution dynamic nuclear polarization (D‐DNP). Hyperpolarized weak “spy ligands” can be displaced by high‐affinity competitors. Hyperpolarized LLS allow one to decrease both protein and ligand concentrations to micromolar levels and to significantly increase sample throughput.     

Development and Validation of 2D Difference Intensity Analysis for Chemical Library Screening by Protein‐Detected NMR Spectroscopy

An academic chemical screening approach was developed by using 2D protein‐detected NMR, and a 352‐chemical fragment library was screened against three different protein targets. The approach was optimized against two protein targets with known ligands: CXCL12 and BRD4. Principal component analysis reliably identified compounds that induced nonspecific NMR crosspeak broadening but did not unambiguously identify ligands with specific affinity (hits). For improved hit detection, a novel scoring metric—difference intensity analysis (DIA)—was devised that sums all positive and negative intensities from 2D difference spectra. Applying DIA quickly discriminated potential ligands from compounds inducing nonspecific NMR crosspeak broadening and other nonspecific effects. Subsequent NMR titrations validated chemotypes important for binding to CXCL12 and BRD4. A novel target, mitochondrial fission protein Fis1, was screened, and six hits were identified by using DIA. Screening these diverse protein targets identified quinones and catechols that induced nonspecific NMR crosspeak broadening, hampering NMR analyses, but are currently not computationally identified as pan‐assay interference compounds. The results established a streamlined screening workflow that can easily be scaled and adapted as part of a larger screening pipeline to identify fragment hits and assess relative binding affinities in the range of 0.3–1.6 mm . DIA could prove useful in library screening and other applications in which NMR chemical shift perturbations are measured.     

丙烯齐聚制壬烯生产工艺条件研究

研究了以丙烯为原料、磷酸／硅胶为催化剂,进行齐聚反应生产壬烯的工艺条件。最佳反应条件是：活化水质量流量约占总进料质量流量的1％,进料温度为200℃,催化剂初期反应温度为200—210℃,反应压力为4.0—4．5MPa,催化剂末期反应温度为220—230℃,反应压力为4.5—5.5MPa。     

Identification of the Binding Site of Apical Membrane Antigen 1 (AMA1) Inhibitors Using a Paramagnetic Probe

Apical membrane antigen 1 (AMA1) is essential for the invasion of host cells by malaria parasites. Several small-molecule ligands have been shown to bind to a conserved hydrophobic cleft in Plasmodium falciparum AMA1. However, a lack of detailed structural information on the binding pose of these molecules has hindered their further optimisation as inhibitors. We have developed a spin-labelled peptide based on RON2, the native binding partner of AMA1, to probe the binding sites of compounds on PfAMA1. The crystal structure of this peptide bound to PfAMA1 shows that it binds at one end of the hydrophobic groove, leaving much of the binding site unoccupied and allowing fragment hits to bind without interference. In paramagnetic relaxation enhancement (PRE)-based NMR screening, the ¹H relaxation rates of compounds binding close to the probe were enhanced. Compounds experienced different degrees of PRE as a result of their different orientations relative to the spin label while bound to AMA1. Thus, PRE-derived distance constraints can be used to identify binding sites and guide further hit optimisation.     

Novel Aeruginosin‐865 from Nostoc sp. as a Potent Anti‐inflammatory Agent

Aeruginosin‐865 (Aer‐865), isolated from terrestrial cyanobacterium Nostoc sp. Luke?ová 30/93, is the first aeruginosin‐type peptide containing both a fatty acid and a carbohydrate moiety, and is the first aeruginosin to be found in the genus Nostoc. Mass spectrometry, chemical and spectroscopic analysis as well as one‐ and two‐dimensional NMR and chiral HPLC analysis of Marfey derivatives were applied to determine the peptidic sequence: D ‐Hpla, D ‐Leu, 5‐OH‐Choi, Agma, with hexanoic and mannopyranosyl uronic acid moieties linked to Choi. We used an AlphaLISA assay to measure the levels of proinflammatory mediators IL‐8 and ICAM‐1 in hTNF‐α‐stimulated HLMVECs. Aer‐865 showed significant reduction of both: with EC₅₀ values of (3.5±1.5) μg mL^?1 ((4.0±1.7) μM ) and (50.0±13.4) μg mL^?1 ((57.8±15.5) μM ), respectively. Confocal laser scanning microscopy revealed that the anti‐inflammatory effect of Aer‐865 was directly associated with inhibition of NF‐κB translocation to the nucleus. Moreover, Aer‐865 did not show any cytotoxic effect.     

Oligomerization of ethylene on platinum by a two-step reaction sequence

On Pt, substantial fractions of chemisorbed C₂h₄ can be converted to C₃₊ alkanes by subsequent hydrogenation. The absence of H₂ during chemisorption is considered as the main factor favoring C-C bonding between adsorbed species, whereas its further addition permits higher alkanes to be released.     

Formation Kinetics and Structural Features of Beta‐Amyloid Aggregates by Sedimented Solute NMR

The accumulation of soluble toxic beta‐amyloid (Aβ) aggregates is an attractive hypothesis for the role of this peptide in the pathology of Alzheimer's disease. We have introduced sedimentation through ultracentrifugation, either by magic angle spinning (in situ) or preparative ultracentrifuge (ex situ), to immobilize biomolecules and make them amenable for solid‐state NMR studies (SedNMR). In situ SedNMR is used here to address the kinetics of formation of soluble Aβ assemblies by monitoring the disappearance of the monomer and the appearance of the oligomers simultaneously. Ex situ SedNMR allows us to select different oligomeric species and to reveal atomic‐level structural features of soluble Aβ assemblies.     

乙烯齐聚法制取线性α-烯烃技术进展

线性α-烯烃是重要的基本有机化工原料和精细化学品生产的中间体,在合成聚烯烃方面需求增长迅速。乙烯齐聚法主要包括烷基铝催化法、SHOP法和金属络合物催化法等三种工艺。本文对线性α-烯烃的应用以及近年来的技术进展做了详尽总结。鉴于我国目前尚无乙烯齐聚法生产α-烯烃的工业装置,笔者认为应该重视和加强这方面的研发工作。     

AlCl_3-丙三醇络合催化剂催化1-辛烯齐聚工艺

以1-辛烯为原料,A1C13/丙三醇络合物为催化剂,催化1-辛烯齐聚反应,合成α-烯烃。考察了络合催化剂的添加量、反应温度、反应时间、丙三醇与AlCl3的摩尔比对聚α-烯烃（PAO）收率的影响。结果表明,在AlCl3摩尔分数为4%,丙三醇与AlCl3的摩尔比为0.5,反应温度为40℃,反应时间为4 h的条件下,PAO收率达到85.6%,且具有较好的选择性。     

AlCl3-丙三醇络合催化剂催化1-辛烯齐聚工艺

以1-辛烯为原料,A1C13/丙三醇络合物为催化剂,催化1-辛烯齐聚反应,合成α-烯烃。考察了络合催化剂的添加量、反应温度、反应时间、丙三醇与AlCl3的摩尔比对聚α-烯烃(PAO)收率的影响。结果表明,在AlCl3摩尔分数为4%,丙三醇与AlCl3的摩尔比为0.5,反应温度为40℃,反应时间为4 h的条件下,PAO收率达到85.6%,且具有较好的选择性。     

添加剂对氯铝酸离子液体催化异丁烯齐聚反应的影响

含有AlCl4-和/或Al2Cl7-阴离子的氯铝酸离子液体对异丁烯齐聚反应有很强的催化活性,但反应的选择性较差。改变离子液体本身的阴、阳离子种类不能提高反应的选择性。在氯铝酸离子液体中引入Cu+进行改性,改性后离子液体的阴离子具有双金属的配位中心,能够有效抑制齐聚过程中裂化等副反应的发生,改善目标产物的选择性。当氯化亚铜与氯铝酸离子液体的物质的量比为0.1时,液相产物中二聚物和三聚物的含量达到60%以上。     

Confocal Spectroscopy to Study Dimerization,Oligomerization and Aggregation of Proteins: A Practical Guide

Protein self-association is a key feature that can modulate the physiological role of proteins or lead to deleterious effects when uncontrolled. Protein oligomerization is a simple way to modify the activity of a protein, as the modulation of binding interfaces allows for self-activation or inhibition, or variation in the selectivity of binding partners. As such, dimerization and higher order oligomerization is a common feature in signaling proteins, for example, and more than 70% of enzymes have the potential to self-associate. On the other hand, protein aggregation can overcome the regulatory mechanisms of the cell and can have disastrous physiological effects. This is the case in a number of neurodegenerative diseases, where proteins, due to mutation or dysregulation later in life, start polymerizing and often fibrillate, leading to the creation of protein inclusion bodies in cells. Dimerization, well-defined oligomerization and random aggregation are often difficult to differentiate and characterize experimentally. Single molecule “counting” methods are particularly well suited to the study of self-oligomerization as they allow observation and quantification of behaviors in heterogeneous conditions. However, the extreme dilution of samples often causes weak complexes to dissociate, and rare events can be overlooked. Here, we discuss a straightforward alternative where the principles of single molecule detection are used at higher protein concentrations to quantify oligomers and aggregates in a background of monomers. We propose a practical guide for the use of confocal spectroscopy to quantify protein oligomerization status and also discuss about its use in monitoring changes in protein aggregation in drug screening assays.     

Oligomerization of ethylene by several normal butyllithium-amine complexes: 8. Kinetic study

A detailed study of the effect of new amines: dimethyl-diethylethylene diamine (DMDEEDA) and pentamethyldiethylenetriamine (PMDT), on the addition of ethylene to n-butyllithium has been made in order to determine the mechanism of the growth step. The results obtained indicate the absence of aggregated species and the following equation has been established for both amines:

$\text{V}{}_{\mathrm{p}}\text{=k}{}_{\mathrm{p}}\text{[}\text{n-BuLi:Amine}\text{][}\text{Et}\text{]}$

     

异丁烯齐聚固定床反应器的模拟

利用高压微反实验装置,在排除了外扩散影响的基础上,利用集总的方法建立了异丁烯齐取反应集总动力学模型,并对该模型进行了求解,获得了该反应集总宏观动力学方程;对φ30mm的固定床反应器建立了一维拟均相模型,结合集总动力学方程对该反应器进行了模拟,实验结果与模拟结果吻合,证明动力学模型与反应器模型是可行的。     

乙烯齐聚催化剂研究进展

乙烯齐聚是合成直链低碳α-烯烃最先进的方法,直链低碳α-烯烃可用于生产低密度聚乙烯和高密度聚乙烯等多种精细化学品。本文综述了乙烯齐聚催化体系的研究进展,重点介绍了镍、锆、钛催化剂的组成以及反应时间、反应温度、溶剂、助催化剂等因素对乙烯齐聚活性和选择性的影响,并讨论了典型镍的催化机理。