巯基化改性壳聚糖在电化学生物传感器制备中的应用

以壳聚糖、N-乙酰-L-半胱氨酸(NAC)为原料,以1-羟基苯并三唑(HOBt)和1-乙基-3-(3-二甲基胺丙基)碳化二亚胺盐酸盐(EDAC)为缩合剂,合成功能化壳聚糖衍生物巯基壳聚糖(CHS-NAC).用红外光谱(FTIR)、核磁共振(1H-NMR)及X射线衍射(XRD)对其结构进行表征,用Ellman’s试剂通过标准曲线法测得巯基含量.利用CHS-NAC的黏附性,通过层层吸附的方法将CHS-NAC、纳米金及细胞色素c分别修饰到玻碳电极(GC)上,通过扫描电子显微镜(SEM)对修饰电极表面的形貌进行了观察,采用循环伏安和电化学阻抗研究了不同修饰膜电极的电化学行为,及扫描速率对细胞色素c修饰电极的影响,并开展了对过氧化氢的电催化分析.实验结果表明,CHS-NAC能高效地将纳米金及细胞色素c固定在电极表面,并能有效发挥纳米金辅助转移电子及细胞色素c对过氧化氢催化的能力.     

含末端炔基的Salen型金属配合物的合成、表征及性质

设计合成了新型含有末端炔基的Salen型配体H2Ln及其系列金属配合物MLn(n=1,2;M=Ni,Cu,Mn),并用氢核磁共振(1H NHR)谱、电喷雾质谱(ESI-MS)、元素分析(EA)、傅里叶变换红外(FT-IR)光谱和紫外-可见(UV-Vis)光谱等对各目标化合物进行了表征.采用循环伏安法研究了配体及其金属配合物的电化学氧化还原性质.研究发现,配体除H2L1外均在测试范围内出现特征的亚胺氧化还原峰.镍和铜的配合物均经历了两个单电子的氧化还原过程;锰的配合物均出现由Mn(III)/Mn(II)产生的一对氧化还原峰,该过程为准可逆的单电子过程.H2Ln及MLn的溶液摩尔电导率数据显示,各目标化合物为弱电解质,具有一定的导电性.     

Synthesis,X-ray crystal structure,and electrochemistry of polynuclear azido-bridged manganese(III) and copper(II) Schiff base complexes

New azido-bridged [Mn^III(salabza)(μ-1,3-N₃)]_n (1), and [Cu^II₄(salabza)₂(μ-1,1-N₃)₂(N₃)₂(HOCH₃)₂],(2) complexes with an unsymmetrical Schiff base ligand, {H₂salabza = N,N’-bis(salicylidene)-2-aminobenzylamine}, have been synthesized, characterized by spectroscopic and electrochemical methods, and their crystal structures have been determined by X-ray diffraction. In complex 1, each manganese(III) atom is coordinated with N₂O₂ donor atoms from salabza and two adjacent Mn(III) centers are linked by an end-to-end (EE) azide bridge to form a helical polymeric chain with octahedral geometry around the Mn(III) centers. Complex 2 is a centrosymmetric tetranuclear compound containing two types of Cu(II) centers with square pyramidal geometry. Each terminal copper atom is surrounded by N₂O₂ atoms of a salabza ligand, and the oxygen atom of the methanol molecule. Each central copper(II) ion is coordinated with two phenoxo oxygen atoms from one salabza, one terminal azido, and two end-on (EO) bridging azido ligands. The central copper(II) ions are linked to each other by the two end-on (EO) azido groups.     

Synthesis and Spectral and Electrochemical Characterization of Novel Substituted 1,4-Naphthoquinone Derivatives

The novel substituted 2,3-dichloro-1,4-naphthoquinone derivatives were synthesized from the reactions of (1) and related nucleophilles in sodium carbonate (Na₂CO₃) solution of ethanol, chloroform with Et₃N, or potassium carbonate (K₂CO₃) solution of acetonitrile. The structures of novel compounds were characterized by using microanalysis, Fourier transform–infrared, ¹H NMR, ¹³C NMR, mass spectrometry, and cyclic voltammetry (CV).

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Solution structure of a designed cyclic peptide ligand for nickel and copper ions

Nuclear magnetic resonance (NMR) spectroscopy was used to study a cyclic peptide derived from the amino-terminal copper-and-nickel-binding (ATCUN) motif. The three-dimensional structure of the unliganded peptide in aqueous solution was solved by simulated annealing using distance constraints derived from Nuclear Overhauser Effects. A structural model for the Ni(II)-bound complex was also produced based on NMR evidence and prior spectroscopic data, which are consistent with crystal structures of linear ATCUN complexes. Structural interpolation, or ‘morphing’, was used to understand the transition of this highly structured cyclic peptide from its unliganded structure to its metal-ion-bound structure.     

Effective synthesis of cyclic peptide yunnanin C and analogues via Ser/Thr ligation (STL)-mediated peptide cyclization

Cyclic peptide yunnanin C isolated from the root of Stellaria yunnanensis was efficiently synthesized in which the linear peptide was prepared by Boc-SPPS and the cyclization was realized by serine/threonine ligation (STL)-mediated cyclization. In addition, nine yunnanin C analogues, including mutations of Tyr7Gly, Tyr7Val, Tyr7Pro, Tyr7Phe, Ser1Thr, Pro2Val, Gly5Pro, Phe6Ala and Ile4Ala, were prepared in the same fashion. Here, we demonstrated that STL-mediated peptide cyclization could be an effective approach to construct cyclic peptides. Except that proline at the C-terminus could retard the cyclization process, cyclization of yunnanin C analogues with various C-terminal amino acids proceeded with fast cyclization rate (<4 h) and only trace amount of dimers (<5%) at a working concentration of 5 mM.     

Synthesis of chromeno[3,4-c][1,2]oxazine-N-oxides via formal [4+2] cycloaddition of 3-nitro-2-trihalomethyl-2H-chromenes with cyclohexanone and pinacolone enamines

3-Nitro-2-trichloro(trifluoro)methyl-2H-chromenes undergo a formal [4+2] cycloaddition reaction to cyclohexanone and pinacolone enamines, producing chromeno[3,4-c][1,2]benzoxazin-6-oxides with high diastereoselectivity and in good yields. In addition, some novel 2,3,4-trisubstituted chromanes were obtained. The stereochemistry of the products was established based on a 2D NOESY experiment and an X-ray diffraction study.     

Investigating the scope of pseudoproline assisted peptide cyclization

The cyclization of linear peptides from six to nine amino acids in length and containing between two and four pseudoproline turn inducers derived from serine or threonine was investigated to determine the effect of peptide length, amino acid composition and spacing between the pseudoproline residues on macrocyclization yield.     

Preparation of cyclic boramides from salicylaldehydes,ammonium acetate and sodium borohydride

Borohydride reduction of salicylaldehyde imines yields surprisingly a cyclic boramide. This is a fairly stable compound, and X-ray analysis shows it has a tetrahedral boron atom. Mechanistic studies show a reaction pathway through an oxazaborinane intermediate. The reaction also works with halogen substituted salicylaldehydes and for the preparation of non-symmetrical boramides.     

New cyclic RGD peptides: synthesis,characterization, and theoretical activity towards αvβ3 integrin

Two new cyclic RGD peptides were prepared using a click chemistry approach. The linear RGDfV peptide was synthesized by solid-phase peptide synthesis using a 9-fluorenylmetoxicarbonyl (Fmoc) strategy and a 2-chlorotrityl chloride resin. After coupling 5-hexynoic acid the peptide was cleaved from the resin and linked to propargylamine. The bis-alkynyl RGDfV peptide was then reacted with two different bis-azides by treatment with copper iodide and triethylamine. These two cyclic RGD peptides were characterized by NMR and HRMS. In order to evaluate the interaction of these new compounds with integrin α_vβ₃ docking experiments were carried out and the results compared with those obtained with cyclo(RGDf[N–Me]V) (Cilengitide). The two new cyclic RGD peptides showed a higher affinity to the α_vβ₃ integrin when compared with Cilengitide thus representing two new potential integrin α_vβ₃ antagonists.