Selective determination of melamine in milk samples using 3-mercapto-1-propanesulfonate-modified gold nanoparticles as colorimetric probe

A novel and sensitive colorimetric method for determination of melamine in milk samples was developed by a 3-mercapto-1-propanesulfonate-modified gold nanoparticles (MPS-GNPs) probe. Melamine molecule has multiple -NH₂ groups. These functional groups can interact with MPS to form strong hydrogen bonding and induce the aggregation of the MPS-GNPs, resulting in a dramatic color change from red to blue. Therefore, the concentration of melamine in milk samples can be quantitatively detected by the naked eyes or a UV-vis spectrometer. Moreover, investigations have revealed that the sensitivity of the detection could be clearly improved by adding NaCl to the modified GNPs solution, which leads to a more rapid color change in the NaCl-optimized GNPs system. It is worth noting that the absorption ratio (A₆₅₀/A₅₂₀) of the modified GNPs in the NaCl-optimized system exhibited a linear correlation with melamine concentration and the limit of detection is 8 nM, well below the safety limit (1 ppm for infant formula in China).     

Surface-enhanced Raman scattering detection of the breast cancer susceptibility gene BRCA1 using a silver-coated microarray platform

Surface-enhanced Raman scattering (SERS) spectroscopy was used to monitor DNA hybridization of a fragment of the BRCA1 breast cancer susceptibility gene on modified silver surfaces. Rhodamine B was covalently attached to a 5′-amino-labeled oligonucleotide sequence (23 mer) through a succinimidyl ester intermediate in methanol. The silver surfaces were prepared by depositing a discontinuous layer (9.0 nm) of silver onto glass slides, which had been etched with HF to form a microwell platform, and subsequently modified with a monolayer of mercaptoundecanoic acid. The complementary probe was covalently attached to the silver surfaces using a succinimidyl ester intermediate in acetonitrile. The silver island substrate allows a very large enhancement of the Raman signal of the DNA-Rhodamine B, and clear distinction between hybridized samples and controls on a microwell array sampling platform.     

Ag/Si-NPA基底上共吸附R6G和CV的表面增强拉曼散射

以硅纳米孔柱阵列(Si-NPA)为基底, 采用浸渍沉积技术制备了具有较高表面增强拉曼散射(SERS)活性的Ag/Si-NPA衬底, 并采用扫描电子显微镜和透射电子显微镜对其表面形貌和结构进行了表征. 在此基础上, 选择罗丹明6G(R6G)和结晶紫(CV)2种生物染料分子并采用不同的混合吸附程序对其共吸附状态下的SERS光谱进行了探测. 结果表明, 当2种分子的溶液浓度均为10^-7 mol/L时, 无论采用何种浸渍吸附程序, 其SERS谱中CV的特征拉曼峰都被R6G完全掩盖. 对溶液采用错级配置(R6G和CV的浓度分别为10^-9和10^-7 mol/L)后, 所测SERS谱上获得了分别对应于R6G和CV的分离良好、相对强度匹配、分辨率高的2个SERS特征峰组, 从而有利于简化现实混合探测过程中对SERS特征峰的指认和判断.     

Surface-enhanced resonance Raman spectroscopic study of yeast iso-1-cytochrome c and its mutant

The structural stability and redox properties of yeast iso-1-cytochrome c and its mutant, F82H, were studied by surface-enhanced resonance Raman scattering (SERRS) spectroscopy. Phenylalanine, which exists at the position-82 in yeast iso-1-cytochrome c, is replaced by histidine in the mutant. The SERRS spectra of the proteins on the bare silver electrodes indicate that the mutant possesses a more stable global structure with regard to the adsorption-induced conformational alteration. The redox potential of the mutant negatively shifts by about 400 mV, relative to that of yeast iso-1-cytochrome c. This is ascribed to axial ligand switching and higher solvent accessibility of the heme iron in the mutant during the redox reactions.     

白杨素-6-磺酸钠及其Zn(Ⅱ)、Ca(Ⅱ)配位化合物与NDA作用的研究

采用紫外、荧光、粘度法研究了白杨素-6-磺酸钠、白杨素-6磺酸双核锌及白杨素-6-磺酸四核钙与小牛胸腺DNA的结合常数分别是KNa=1.52×104L.mol-1、KZn=3.56×104L.mol-1和KCa=1.54×104L.mol-1。实验结果表明,白杨素-6-磺酸双核锌和白杨素-6-磺酸四核钙;白杨素-6-磺酸钠与DNA间的作用方主要为静电结合。     

Synthesis, Characterization, Spectroscopic Properties of 2-（4-Dimethylaminophenyl）-5-fluoro-6-（morpholin-4-yl）-1H-benzimidazole and its Interaction with Calf Thymus DNA

Benzimidazole compounds have attracted a renewed interest recently owing to theirpotential applications in high-performance composite materials, electronic chemicals,photosensitive materials, and their special potentials in biological and/or medicinalapplication1,2. Typically, aromatic compounds with near planar structures and contain-ing hydrogen-donor groups or groups, which are capable of being protonated, havespecial interactions with DNA via intercalation, hydrogen-bonding, and so on3.Me…     

A Au mössbauer study of reaction products of trimeric 1-benzyl-2-gold(I)-imidazole leading to Au carbene or Au imidazoline complexes and trinuclear Au imidazolyl derivatives. X-Ray crystal structure of [{(μ-1-benzylimidazolato-N,C)Au}3I2]

Reactions of the trinuclear [Au₃Rim₃] compound (Rim = [μ-1-benzylimidazolato-N³,C²] with several reagents capable of oxidative addition have been investigated by ¹⁹⁷Au Mössbauer spectroscopy. The reaction products are either Au^I carbene mononuclear and binuclear complexes or trinuclear Au^III and mixed-valence compounds. The X-ray crystal structure of the mixed-valence complex [Au^IIIAu^I₂Rim₃I₂] has been determined. Two two-coordinate Au^I centres show average Au---C and Au---N distances of 2.02(3) and 2.04(2) Å and average C---Au---N angles of 175.0(1.2)°, whereas the four-coordinate Au^III centre gives Au---C and Au---N 1.96(4) and 1.91(3) Å with the C---Au---N angle 170.5(1.6)°, and Au---I average distances 2.598(3) Å, with an I---Au=I angle 175.8(1)°. The Au---Au intramolecular distances [Au(1) Au(2) 3.432(3), Au(1) Au(3) 3.508(3), Au(2) Au(3) 3.464(3) Å] indicate a weak metal-metal interaction.     

Asymmetric aldol reactions using catalytic d(+)-proline: a new, economic and practical approach to a commonly employed C1-C6 keto-acid synthon of the epothilones

A new approach to ketoacid 4, a common C1-C6 fragment used in the total synthesis of epothilones was initiated by direct aldol reaction of acetone with a pivaldehyde-like substance 5, catalyzed with d-proline, leading to a 2,6-diketoalcohol with better than 99% ee. Further intramolecular closure of the diketone 8 followed by oxidation of the silyl protected hydroxycyclohexenone 14 led to the desired product 4. None of the steps have been optimized, yet the overall yield for the four-step process is 31%. The use of commercially available d-proline to construct the chiral center of 4 under very mild reaction conditions provided an economical and practical method for its construction.     

Regioselective monobromination of (E)-1-(2′-hydroxy-4′,6′-dimethoxyphenyl)-3-aryl-2-propen-1-ones using bromodimethylsulfonium bromide and synthesis of 8-bromoflavones and 7-bromoaurones

A wide variety of monobrominated compounds 2a-l have been prepared in good yields from (E)-1-(2′-hydroxy-4′,6′-dimethoxyphenyl)-3-aryl-2-propen-1-ones (1a-l) through regioselective ring bromination using 1.5 equiv of bromodimethylsulfonium bromide (BDMS) at room temperature. Similarly, some of the 2′-hydroxychalcones can be converted directly into tribromides 3 or dibromides 4 by employing 4.0 equiv of BDMS under different reaction conditions which in turn can be transformed into 8-bromoflavones and 7-bromoaurones on treatment with 0.2 M ethanolic KOH solution. Mild reaction conditions, good yields and no chromatographic separation are some of the salient features of the present protocol.