Macrocycle-Directed Construction of Tetrahedral Anion–π Receptors for Nesting Anions with Complementary Geometry

Manipulation of the emerging anion–π interactions in a highly cooperative manner through sophisticated host design represents a very challenging task. In this work, unprecedented tetrahedral anion–π receptors have been successfully constructed for complementary accommodation of tetrahedral and relevant anions. The synthesis was achieved by a macrocycle-directed approach by using large macrocycle precursors bearing four reactive sites, which enabled a kinetic-favored pathway and afforded the otherwise inaccessible tetrahedral cages in considerable yields. Crystal structure suggested that the tetrahedral cages have an enclosed three-dimensional cavity surrounded by four electron-deficient triazine faces in a tetrahedral array. The complementary accommodation of a series of tetrahedral and relevant anions including BF₄⁻, ClO₄⁻, H₂PO₄⁻, HSO₄⁻, SO₄²⁻ and PF₆⁻ was revealed by ESI-MS and DFT calculations. Crystal structures of ClO₄⁻ and PF₆⁻ complexes showed that the anion was nicely encapsulated within the tetrahedral cavity with up to quadruple cooperative anion–π interactions by an excellent shape and size match. The strong anion–π binding was further confirmed by negative ion photoelectron spectroscopy measurements.     

隐身技术光谱反射率的发展探讨

介绍了隐身技术的发展,论述了光谱反射率在可见光隐身技术、激光隐身技术、红外隐身技术、雷达隐身技术、多波段复合型隐身技术等不同领域的进展,简要总结了光谱反射率技术在隐身技术中的发展方向.     

p(HEMA-MMA)表面固定I-型胶原和碱性成纤维生长因子(bFGF)改善细胞相容性的研究

材料表面固定生物分子一直都被认为是其提高其细胞相容性有效的途径。本文采用羧基二咪唑(CDI)作为缩合剂,使p(HEMA-MMA)表面羟基与胶原中氨基发生缩合反应,从而将I-型胶原接枝在材料表面。然后利用"接枝-吸附"的方法,将I-型胶原和bFGF混合层吸附固定于材料表面,形成稳定的胶原与bFGF涂层。红外光谱(FTIR)和原子力显微镜(AFM)证实了该种固定方法的成功。静态接触角显示材料表面亲水性较改性前略微降低。涂层稳定性实验结果表明在类似人体环境(pH=7.4)下涂层具有良好的稳定性。细胞粘附性实验以及MTT实验一致显示改性后材料的细胞相容性得到明显提高。因此,Col/bFGF-p(HEMA-MMA)有望成为能够被宿主机体所接受的生物材料。     

具有形状记忆性能的P(MMA-co-HEA)/PDMS-OH氢键复合物的研究

选择低分子量端羟基聚二甲基硅氧烷(PDMS-OH)与聚(甲基丙烯酸甲酯-co-丙烯酸β-羟乙酯)P(MMA-co-HEA)共聚物原位复合形成氢键复合物,该复合物表现出良好的形状记忆效应.通过FTIR,SEM对材料的结构和形貌进行表征,DMA表征材料的动态力学行为,并通过弯曲实验对材料的形状记忆性能进行了表征及比较.FTIR分析证明PDMS-OH与P(MMA-co-HEA)共聚物形成氢键缔合作用;SEM分析显示,随着PDMS-OH含量的升高,氢键复合物由"海-岛"相分离结构向反转相分离结构转变;DMA分析结果表明,氢键的引入有利于复合物获得更高的模量比;形状记忆性能测试结果显示该氢键复合物具有良好的形状记忆性能,形状记忆固定率超过98%、形变恢复率超过99%,并且与聚(甲基丙烯酸甲酯-co-丙烯酸乙酯)/PDMS-OH(P(MMA-co-EA)/PDMS-OH)复合物相比,氢键复合物显示出更快的形变回复速率.     

基于GPU计算的并行PLS算法研究与实现

偏最小二乘算法(PLS)是与红外、近红外光谱分析结合使用最为广泛的化学计量学算法,然而当前PLS算法通常采用单线程方式实现,当校正模型数量多或样本数量大、波长点数和主成分数较多,模型需对光谱预处理和波长选择方法反复优化时,计算十分缓慢。为大幅提高建模速度,该文提出了一种基于图形处理器(GPU)的并行计算策略,利用具有大规模并行计算特性的GPU作为计算设备,结合CUBLAS库函数实现了基于GPU并行的PLS建模算法(CUPLS)。利用近红外光谱数据集进行性能对比实验,结果表明CUPLS建模算法较传统单线程实现的PLS算法,加速比可达近42倍,极大地提升了化学计量学算法的建模效率。该方法亦可用于其它化学计量学算法的加速。     

Microencapsulation of protein‐loaded polysaccharide particles within poly(D,L‐lactic‐co‐glycolic acid) microspheres using S/O/W: characterization and release studies

This report demonstrates a process to form polysaccharide glassy particles without water–oil or water–air interfaces as well as ionic polymers and its application in formulating sustained‐release dosage forms for structurally delicate proteins. When a co‐solution containing dextran and polyethylene glycol (PEG) was subjected to freeze‐drying, the dextran separated out of the solution to form dispersed phases surrounded by a PEG‐rich continuous phase and was solidified during subsequent lyophilization to fine glassy particles, 1–2 µm in diameter. Water‐soluble proteins can easily be loaded in these glassy particles due to preferential partition and become resistant to organic solvents simply by adding them into the dextran‐PEG co‐solution. After washing away the PEG continuous phase with organic solvents, the protein‐containing glassy particles can be suspended in a hydrophobic polymer solution and formulated into various pharmaceutical dosage forms and medical devices for sustained‐release protein delivery. In the present study, myoglobin, bovine serum albumin (BSA), and β‐galactosidase (β‐gal) were formulated in PLGA mcirospheres and as model proteins using this glassy particulate approach, and subjected to a series of assays for release kinetics, structural integrity, and bioactivity. The experimental results indicated that this system offered well preserved protein integrity and bioactivity as well as significantly improved protein release kinetics. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of hollow composite spheres with raspberry‐like structure based on hydrogen‐bonding interaction

The hollow composite spheres with a raspberry‐like structure were prepared by a self‐assemble heterocoagulation based on the inter‐particle hydrogen‐bonding interaction between the amide groups of hollow poly (N,N′‐methylenebisacrylamide‐co‐N‐isopropyl acrylamide) (P(MBA‐co‐NIPAAm)) microspheres and the carboxylic acid groups of poly(ethyleneglycol dimethacrylate‐co‐methacrylic acid) (P(EGDMA‐co‐MAA)) nanoparticles, in which P(EGDMA‐co‐MAA) nanoparticle acted as the corona and the hollow P(MBA‐co‐NIPAAm) microsphere behaved as the core. The control coverage of the corona particles on the surface of hollow core microspheres of P(MBA‐co‐NIPAAm)/P(EGDMA‐co‐MAA) hollow composite sphere was studied in detail through adjustment of the mass ratio between the core and corona particles. The effect of the pH on the stability of the raspberry‐like hollow spheres was investigated. The polymer particles and the resultant heterocoagulated raspberry‐like hollow spheres were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Copyright © 2008 John Wiley & Sons, Ltd.     

Fluorescence resonance energy-transfer affects the determination of the affinity between ligand and proteins obtained by fluorescence quenching method

The interaction between esculin and serum albumins was investigated to illustrate that the fluorescence resonance energy-transfer (FRET) affects the determination of the binding constants obtained by fluorescence quenching method. The binding constants (K_a) obtained by the double-logarithm curve for esculin–BSA and esculin–HSA were 1.02 × 10⁷ and 2.07 × 10⁴ L/mol, respectively. These results from synchronous fluorescence showed that the Tyr and Trp residues of HSA were affected more deeply than those in BSA. The excitation profile of esculin showed that in the presence of BSA and HSA, the S₀ → S₁ transition of esculin () appears, which is similar to the of BSA and HSA. The critical distance (R₀) between BSA and esculin is higher than that of HSA, which showed that the affinity of esculin and HSA should be higher than that of BSA. After centrifugation, the concentrations of esculin bound to albumins were determined by means of the fluorescence of esculin. It was found that much more esculin was bound to HSA than to BSA. However, the bound models for BSA and HSA are almost the same. The concentration of esculin bound to serum albumin at first decreased with the addition of esculin and then increased. From above results, it can be concluded that the affinity of esculin and HSA should be higher than that of esculin and BSA. This example showed that in the presence of FRET, the binding constants between ligands and proteins based on fluorescence quenching might be deviated.     

轻质油料电导率仪自动检定方法

研究了一种对轻质油料电导率仪进行自动检定的方法。采用模拟高阻技术和视频采集控制软件相结合,减少了人体对检定结果的影响,提高了检定效率和检定结果的可靠性。该方法对研究轻质油料电导率仪的测量参数和相关仪器的特殊测量范围的线性有很大的帮助。     

Analysis and prediction of RNA-binding residues using sequence, evolutionary conservation, and predicted secondary structure and solvent accessibility

Identification and prediction of RNA-binding residues (RBRs) provides valuable insights into the mechanisms of protein-RNA interactions. We analyzed the contributions of a wide range of factors including amino acid sequence, evolutionary conservation, secondary structure and solvent accessibility, to the prediction/characterization of RBRs. Five feature sets were designed and feature selection was performed to find and investigate relevant features. We demonstrate that (1) interactions with positively charged amino acids Arg and Lys are preferred by the egatively charged nucleotides; (2) Gly provides flexibility for the RNA binding sites; (3) Glu with negatively charged side chain and several hydrophobic residues such as Leu, Val, Ala and Phe are disfavored in the RNA-binding sites; (4) coil residues, especially in long segments, are more flexible (than other secondary structures) and more likely to interact with RNA; (5) helical residues are more rigid and consequently they are less likely to bind RNA; and (6) residues partially exposed to the solvent are more likely to form RNA-binding sites. We introduce a novel sequence-based predictor of RBRs, RBRpred, which utilizes the selected features. RBRpred is comprehensively tested on three datasets with varied atom distance cutoffs by performing both five-fold cross validation and jackknife tests and achieves Matthew's correlation coefficient (MCC) of 0.51, 0.48 and 0.42, respectively. The quality is comparable to or better than that for state-of-the-art predictors that apply the distancebased cutoff definition. We show that the most important factor for RBRs prediction is evolutionary conservation, followed by the amino acid sequence, predicted secondary structure and predicted solvent accessibility. We also investigate the impact of using native vs. predicted secondary structure and solvent accessibility. The predictions are sufficient for the RBR prediction and the knowledge of the actual solvent accessibility helps in predictions for lower distance cutoffs.