Radiation synthesis of a water-soluble temperature sensitive polymer, activated copolymer and applications in immobilization of proteins

In this work the radiation polymerization of N-isopropylacrylamide (NIPAAM) in aqueous solutions has been carried out and a water-soluble, temperature sensitive polymer and copolymer were obtained by using γ-rays from Co-60 source at room temperature. We have gained the optimum dose and dose—rate of radiation synthesis of linear polyNIPAAM through determining conversion yield and viscosity. In order to immobilize protein (BSA) and enzyme (HRP) into this water-soluble polymer, we prepared an activated copolymer, poly ( N-isopropylacrylamide-co-N-acryloxysuccinimide). The BSA and HRP has been immobilized onto the activated copolymer. The BSA (HRP) / copolymer conjugates still kept the original thermally sensitive properties of the linear polyNIPAAM. The conjugation yield of BSA to the activated copolymer decreased with increasing of dose. The thermal stability of the immobilized HRP was stable at 0 °C for a long time and has, at least, 4 days stability at room temperature. Immobilized HRP activity was lowered when the temperature was raised above its LCST. This phenomenon was reversible and the immobilized HRP regained activity below its LCST. The optimum pH of the immobilized HRP shifted from ca.5 upward to ca.7.     

Radiation-induced copolymerization of styrene/n-butyl acrylate in the presence of ultra-fine powdered styrene–butadiene rubber

Styrene (St)/n-butyl acrylate (BA) copolymers were prepared by two-stage polymerization: St/BA was pre-polymerized to a viscous state by bulk polymerization with initiation by benzoyl peroxide (BPO) followed by ⁶⁰Co γ-ray radiation curing. The resultant copolymers had higher molecular weight and narrower molecular weight distribution than conventional methods. After incorporation of ultra-fine powdered styrene–butadiene rubber (UFSBR) with a particle size of 100 nm in the monomer, the glass transition temperature (T_g) of St–BA copolymer increased at low rubber content. Both the St–BA copolymer and the St–BA copolymer/UFSBR composites had good transparency at BA content below 40%.     

Al(6)(2-) - fusion of two aromatic Al(3)(-) units. A combined photoelectron spectroscopy and ab initio study of M(+)[Al(6)(2-)] (M = Li,Na, K,Cu, and Au)

Photoelectron spectroscopy is combined with ab initio calculations to elucidate the structure and chemical bonding of a series of MAl(6)(-) (M = Li, Na, K, Cu, and Au) bimetallic clusters. Well-resolved photoelectron spectra were obtained for MAl(6)(-) (M = Li, Na, Cu, and Au) at several photon energies. The ab initio calculations showed that all of the MAl(6)(-) clusters can be viewed as an M(+) cation interacting with an Al(6)(2-) dianion. Al(6)(2-) was found to possess an O(h) ground-state structure, and all of the MAl(6)(-) clusters possess a C(3v) ground-state structure derived from the O(h) Al(6)(2-). Careful comparison between the photoelectron spectral features and the ab initio one-electron detachment energies allows us to establish firmly the C(3v)ground-state structures for the MAl(6)(-) clusters. A detailed molecular orbital (MO) analysis is conducted for Al(6)(2-) and compared with Al(3)(-). It was shown that Al(6)(2-) can be considered as the fusion of two Al(3)(-) units. We further found that the preferred occupation of those MOs derived from the sums of the empty 2e' MOs of Al(3)(-), rather than those derived from the differences between the occupied 2a(1)' and 2a(2)' ' MOs of Al(3)(-), provides the key bonding interactions for the fusion of the two Al(3)(-) into Al(6)(2-). Because there are only four bonding MOs (one pi and three sigma MOs), an analysis of resonance structures was performed for the O(h)Al(6)(2-). It is shown that every face of the Al(6)(2-) octahedron still possesses both pi- and sigma-aromaticity, analogous to Al(3)(-), and that in fact Al(6)(2-) can be viewed to possess three-dimensional pi- and sigma-aromaticity with a large resonance stabilization.     

中药黄芪有效成份的研究 Ⅰ.多糖体的分离、性质及其生理活性

从内蒙黄芪(Astragalus mongholicus Bunge)根的水提液中分得三种多糖:黄芪多糖Ⅰ,Ⅱ及Ⅲ。经玻璃纤维纸电泳及Sephadex G-150凝胶过滤表明为均一体。黄芪多糖Ⅰ是杂多糖,由D-葡萄糖、D-半乳糖和L-阿拉伯糖组成。其克分子比为1.75:1.63:1此外还含痕迹量的五碳糖,经已知分子量的标准葡聚糖在Sephadex G-75凝胶层析所标定的曲线上求得其平均分子量约为36300,比旋度为正,[α]_D~(30.5)+101.5(H _2O)。黄芪多糖Ⅱ及Ⅲ均为D-葡聚糖,其平均分子量分别约为12300和34600,比旋度亦为正,分别为[α]_D~(30.5)+170.8(H_2O)和[α]_D~(26)+177.6(H_2O)。黄芪多糖Ⅱ及Ⅲ经过碘酸氧化及Smith降解结果,除了产生大量的赤藓醇外,还产生丙三醇,这个结果表明两者的组成除含少量α-(1→6)-D-葡萄糖缩合键外。主要是α-(1→4)-D-葡萄糖的缩合键。 APS是水提取液中所分得的均一多糖部位,主要由黄芪多糖Ⅰ及Ⅱ组成,在小鼠上具有广泛的各种负疫作用,能增加小鼠脾脏的重量及细胞数,增加小鼠脾脏对绵羊红细胞的免疫应答反应和促进腹腔巨噬细胞的吞噬功能。若将黄芪多糖Ⅰ及Ⅱ分别试验,初步结果表明多糖Ⅰ能增加脾脏重量及细胞数。但抑制脾细胞对绵羊红细胞的免疫应答反应;多糖Ⅱ作用与多糖Ⅰ相似,但较弱;而多糖Ⅲ则没有作用。     

Simultaneous Kinetic Characterization of Multiple Protein Forms by Top Down Mass Spectrometry

Top down mass spectrometry, using a Fourier transform instrument, has unique capabilities for biomolecule kinetic studies, in that the concentration of large molecules in a reaction mixture can be monitored simultaneously from its mass spectrum produced by electrospray ionization. This is demonstrated with enzyme modifications occurring in the biosynthesis of the thiazole moiety of thiamin phosphate. The formation rate of ThiS-thiocarboxylate from ThiS was determined from the relative abundance of the corresponding m/z 10162 and 10146 isotopic peak clusters for all the observable charge states in the mass spectra measured at different reaction times. Even without measuring standard ionization efficiencies, the rate and precision of 0.018 +/- 0.004 min(-1) agree well with the 0.027 +/- 0.003 min(-1) obtained with a radiochemical assay, which requires a separate derivatization step. To illustrate the simultaneous characterization of the reaction kinetics of a native enzyme and its mutant, the imine formation rate of ThiG and its substrate DXP was compared between the native protein (M(r) = 26803.9) and its E98A (M(r) = 26745.9) or D182A (M(r) = 26759.9) mutant in the same reaction mixture. The kinetic data show clearly that neither the E98 nor the D182 residues participate in the imine formation. The high resolution and MS/MS capabilities of FTMS should make possible the extension of this kinetics approach to far more complicated systems, such as simultaneous monitoring of 24 native, intermediate, and reduced forms in the reductive unfolding of a mixture of ribonuclease A and the five isoforms of ribonuclease B. Stable intermediates with different SS bonding (same molecular weight) can be differentiated by MS/MS, while molecular ions differing by only 2 Da are distinguished clearly by synthesizing isotopically depleted proteins.     

Band-gap engineering of semiconductor nanowires through composition modulation

Alloyed ternary CdS(1-x)Se(x) nanowires were synthesized by template-assisted electrodeposition, in which the ratio of S to Se in the nanowires was controlled by adjusting the relative amounts of the starting materials. Higher-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) showed that the alloyed ternary CdS(1-x)Se(x) nanowires are highly crystalline, and no phase-separated Cd was observed in these nanowires. Optical measurements indicated that the band-gap engineering can be realized in these CdS(1-x)Se(x) nanowires through modulating the composition of S and Se. With broadly tunable optical and electrical properties, these alloyed nanowires could be used in color-tuned nanolasers, biological labels, and nanoelectronics.     

Br2+2HI=2HBr＋I2应机理的密度泛函理论

用密度泛函理论(DFT)B3LYP方法，取3-21G**基组研究了气相反应Br2＋2HI=2HBr＋I2的机理，求得一系列四中心和三中心的过渡态.双分子基元反应Br2＋HI→HBr＋IBr和IBr＋HI→I2＋HBr的活化能(81.02和121.08 kJ•mol－1)小于Br2、HI和IBr的解离能(249.21、320.16和232.42 kJ•mol－1)，故从理论上证明了标题反应将优先以分子与分子作用形式分两步完成.同时发现I原子与Br2分子反应生成较稳定的IBr2是一个无能垒过程，IBr2分解为IBr和Br原子的能垒为70.88 kJ•mol－1.     

Cu3C4-: a new sandwich molecule with two revolving C2(2-) units

A combined photoelectron spectroscopy (PES) and ab initio study was carried out on a novel copper carbide cluster in the gas phase: Cu(3)C(4)(-). It was generated in a laser vaporization cluster source and appeared to exhibit enhanced stability among the Cu(3)C(n)(-) series. Its PES spectra were obtained at several photon energies, showing numerous well-resolved bands. Extensive ab initio calculations were performed on Cu(3)C(4)(-), and two isomers were identified: a C(2) structure ((1)A) with a Cu(3)(3+) triangular group sandwiched by two C(2)(2-) units and a linear CuCCCuCCCu structure (D(infinity)(h), (1)Sigma(g)(+)). A comparison of ab initio PES spectra with experimental data showed that the sandwich Cu(3)C(4)(-) cluster was solely responsible for the observed spectra and the linear isomer was not present, suggesting that the C(2) structure is the global minimum in accordance with CCSD(T)/6-311+G predictions. Interestingly, a relatively low barrier (0.4-0.6 kcal/mol) was found for the internal rotation of the C(2)(2-) units in the sandwich Cu(3)C(4)(-). To test different levels of theory in describing the Cu(m)C(n)(-) systems and lay foundations for the validity of the theoretical methods, extensive calculations at a variety of levels were also carried out on a simpler copper carbide species CuC(2)(-), where two isomers were found to be close in energy: a linear one (C(infinity)(v), (1)Sigma(+)) and a triangular one (C(2)(v), (1)A(1)). The calculated electronic transitions for CuC(2)(-) were also compared with the PES data, in which both isomers were present.     

MgB4O7－MgSO4－MgCl2－H2O及次级体系298.15K时稀释热、热容和表观摩尔焓的研究

本文研究了含硼四元水盐体系ＭｇＢ４Ｏ７－ＭｇＳＯ４－ＭｇＣｌ２－Ｈ２Ｏ及次级体系ＭｇＢ４Ｏ７－ＭｇＳＯ４－Ｈ２Ｏ在２９８．１５Ｋ时不同离子强度下的稀释热和热容，产将Ｄｅｂｙｅ－Ｈｕｃｋｅｌ极限公式应用到多元电解质稀溶液中，获得从高子强度到低离子强度Ｉ为１９－０．０００１范围内的相对表观摩尔焓。     

硫酸溶液中Pt(111)电极面上存在SO2-4的XPS证据

Pt（111）电极在硫酸溶液中的循环伏安图已被多个研究小组所得到[1-3]．对图上出现的高于正常氢吸脱附电位出现的两个电流峰（Clavilier等[1]首次发现并称之为异常峰）的解释至今没有得到一致意见．分歧焦点是异常峰的出现是由于强键合吸附氢还是吸附其它阴离子所致·本文用XPS和LEED研究异常峰电位处浮出的Pt（111）电极表面，发现尖锐异常峰的出现是由于表面上吸附了离子．1实验文献＊中详细说明了实验所用装置．主要部份是把装有XPS、LEED、MS、Ar“枪的超高真空腔门HV）与测量循环伏安图的腔（EC）联在一起·UHV中基压强为4x…