Preparation of a cyclodextrin dimer linked with a bis(picolinyl)cystine moiety and its intra- and intermolecular inclusion behavior

A novel cyclodextrin (CD) dimer linked with a bis(picolinyl)cystine (Cys) moiety was prepared by the coupling of Boc-protected Cys with amino-modified CDs, followed by deprotection of the Boc groups and bispicolinylation. The dimer showed less affinity to an organic guest molecule compared to that of a native CD monomer. It was attributed to an intramolecular inclusion of the pyridine moiety into CD cavity. The dimer caused significant increase of its organic guest affinity by an addition of a copper ion. The included pyridine group may come out of a CD cavity to bind the copper ion and the two CDs included cooperatively and intermolecularly a guest molecule with high affinity.     

Cu（Ⅱ）—胱氨酸络合物吸附波的研究及蛋白质中胱氨酸的测定

研究了Cu(Ⅱ)-胱氨酸络合物极谱波的性质;提出了一种用示波极谱法测定蛋白质中胱氨酸的新方法,可在8.0×10~(-4)mol/L Cu~(2+)+8.0×10~(-3)mol/L三乙醇胺的溶液中测定0.05～20mg/L的胱氨酸。     

Comparison of pulsed amperometric detection and integrated voltammetric detection for inorganic sulfur compounds in liquid chromatography

A Variety of potential–time waveforms are useful in pulsed electrochemical detection (PED) when applied for the amperometric detection of numerous polar organic compounds following their separation by liquid chromatography (LC). Here, we compare the waveforms for pulsed amperometric detection (PAD) and integrated voltammetric detection (IVD) applied for detection of organosulfur compounds at Au electrodes in acidic media. In PAD waveforms, electrodes response is measured at a constant detection potentials. In IVD waveforms, electrodes current is integrated throughout a fast cyclic scan of the detection potential. As a consequence of this difference in detection strategy, the background signal for IVD is significantly smaller for PAD in the detection of organosulfur compounds whose response mechanisms require the concomitant formation of surface oxides on Au electrodes. Furthermore, in comparison to Pad, IVD has a larger sensitivity and a diminished system peak from 0₂ dissolved in the sample. Use of a preadsorption step increases detection sensitivity in both PAD and IVD. The limit of detection (S/N=3)for cysteine in LC-IVD is ca. 6 nM for a 50-μl injection (i.e., 300 fmol) using a detection waveform that includes a 1000-ms preadsorption period.     

原子吸收光谱间接测定胱氨酸的研究

胱氨酸(Cystine,Cys)在碱性条件下与新生成的ZnS悬浮液反应,生成可溶性碱式胱氨酸锌配合物,再用塞曼原子吸收光谱测定溶液中的总锌浓度即可间接的得到胱氨酸的含量.优化了测定的条件,在pH 9.40的2%硼砂底液中于室温下,使胱氨酸试液与新生成的ZnS悬浮液反应20min,离心分离后测定上层清液锌的FAAS响应.在所选定的条件下胱氨酸测定的线性浓度范围为0-450μg·mL-1,特征浓度为4.40μg·mL-1,检出限为4.20μg·mL-1.该法用于样品中的胱氨酸测定,其相对标准偏差RSD为4.45%(n=7),方法的回收率在70.8%-105.8%之间.并对测定机理进行了探讨.     

Triply bridged (1,3,5) cyclophanes from cystine and lanthionine linkers—a comparison

The condensation of benzene 1,3,5-tricarbonylchloride with cystine-di-Me [H₂N-CH(COOMe)-CH₂-S-S-CH₂-CH(COOMe)-NH₂] yielded triply bridged (1,3,5) cyclophane 1, which was shown by detailed spectral studies and molecular orbital calculations to have a D₃ symmetry with conformationally identical linkers and a spherical topology. In sharp contrast, the (1,3,5) cyclophane 2 from the rarely studied lanthionine di-Me [H₂N-CH(COOMe)-CH₂-S-CH₂-CH(COOMe)-NH₂], showed only a equatorial twofold symmetry. This work highlights the special properties of the -S-S- bridge in cystine, which makes it an exceptional synthon in nature and organic synthesis.     

用同步荧光光谱法研究细胞色素C与胱氨酸的相互作用

用同步荧光技术研究了细胞色素Ｃ与促进剂胱氨酸的相互作用，分别监测了二者相互作用时细胞色素Ｃ中色氨酸残基和酪氨酸残基的荧光光谱的变化和二种氨基酸残基的荧光强度随的变化，实验结果表明，胱氨酸分子与细胞色素Ｃ的赖氨酸残基缓慢结合，二者相互作用的最终结果使细胞色素Ｃ分子的构象发生了微小的变化。     

A stereoselective synthesis of a spiro-bridged bis(α-amino acid) derivative based on Ru(II)-catalysed RCM reactions

Methodology for a stereoselective synthesis of a member of a novel family of spiro-bridged bis(α-amino acid) derivatives is described. The key step in the construction is a spirane annulation reaction effected by a Ru(II)-catalysed ring-closing metathesis (RCM) reaction of an appropriately substituted tetraene. The latter became available after stereocontrolled allylations of 3,3-bis[2-((2S,5R)-5-isopropyl-3,6-dimethoxy-2,5-dihydropyrazin-2-yl)ethyl]-1,4-pentadiene, which was prepared in several reaction steps from (2R)-2,5-dihydro-2-isopropyl-3,6-dimethoxypyrazine as a chiral starting material.     

示波极谱同时测定胱氨酸和赖氨酸方法的研究

本文提出在pH为10的Na_2B_4O_7·10H_2O-CH_3CHO-NaOH体系中,于示波极谱仪上,峰电位分别为-0.70V和-1.45V处,可同时测定胱氨酸和赖氨酸,其浓度分别在0.5～100μg/ml和0.5～80μg/ml范围内与峰电流成线性关系,大部分共存氨基酸对测定无大的影响,最大相对标准偏差分别为1.8%和10.0%,接近于氨基酸专用分析仪的测定水平。