Suppressing the fragmentation of fragile molecules in helium nanodroplets by coembedding with water: possible role of the electric dipole moment

When fragile molecules such as glycine, polyglycine, alkanes, and alkanethiols are embedded in liquid helium nanodroplets, electron-impact ionization of the beam leads to fragmentation which is as extensive as that of isolated gas-phase molecules. However, it turns out that if a few molecules of water are coembedded with the peptide and alkane chains, their fragmentation is drastically reduced or completely eliminated. On the other hand, the fragmentation of alkanethiols remains unaffected. On the basis of these observations, it is proposed that the fragmentation "buffering" effect may correlate with the magnitude of the impurity's electric dipole moment, which steers the migration of the ionizing He(+) hole in the droplet.     

蛋品中苏丹红残留的液相色谱串联质谱测定法研究

采用液相色谱-串联质谱法（LC-MS/MS）测定了蛋品中苏丹红I、II、III、Ⅳ号染料的残留。制样后,装柱,应用基质固相分散技术,用氯仿、乙腈混合溶液（体积比为90：10）淋洗,浓缩定容后经ZORBAX SB-C18柱分离,采用电喷雾正离子,多反应监控（MRM）模式检测。外标曲线定量,苏丹红I、II、III、Ⅳ的线性范围分别为0.5～100ng/g,5.0～100ng/g,1.0～100ng/g和2.0～100ng/g,线性方程的相关系数都大于0.99,添加样品回收率在87.3～113％之间,相对标准偏差均小于9.1％。针对四种苏丹红染料,该方法的检测低限分别可达0.1μg/kg,2.0μg/kg,0.2μg/kg,0.4μg/kg,可以满足国内外蛋品中苏丹红监控要求。     

A New Sandwich Polyoxometalate Constructed from a Zn<Stack><Subscript>6</Subscript><Superscript>12+</Superscript></Stack> Hexagon Cluster Sandwiched by Two B-α-[BiW<Subscript>9</Subscript>O<Subscript>33</Subscript>]<Superscript>9−</Superscript>

A new sandwich polyoxometalate Na₄Zn₂[Zn₂(H₂O)₁₀(ZnCl)₆(B-α- BiW₉O₃₃)₂] · 40.5H₂O (1) has been obtained in aqueous solution and characterized by IR, UV, element analysis, TG and single-crystal X-ray analysis. Polyoxoanion 1 is composed of a Zn ₆ ¹²⁺ hexagon sandwiched by two [BiW₉O₃₃]^9? units, which is firstly observed in tungstobismutate. The crystal data for compound 1: Triclinic, space group P–1, a = 15.426(3) Å, b = 15.467(3) Å, c = 15.526(3) Å, α = 74.24(3)°, β = 64.37(3)°, γ = 60.73(3)°, V = 2905.3(1) ų, Z = 1.     

Immobilization of ionic liquid with polyelectrolyte as carrier

An all-purpose approach to immobilize ionic liquids onto solid supports is proposed by chemical grafting on a polyelectrolyte carrier.     

Recent progress in small molecule fluorescent probes for nitroreductase

This review aims to provide a summary of the progress in fluorescent probes for nitroreductase (NTR) in recent years and displays the main fluorescent mechanisms that have been applied to design probes.     

Solvent‐free polymerization of citric acid and hexamethylenediamine for novel carboxylated polyamides

Copolymers of tributyl citrate (TBC) and hexamethylenediamine (HMDA) were synthesized with a solvent‐free condensation method with molar ratios of TBC to HMDA varying from 2:1 to 1:2. The reaction led to poly(succinimide‐co‐citramide) copolymers which were characterized by infrared and Raman spectroscopies, X‐ray diffraction, and thermal analyses. Hydrolysis of the copolymers resulted in water soluble polycitramides with number averaged molecular weights ranging from 1.16 × 10⁴ to 5.00 × 10³ as determined by gel permeation chromatography. ¹H, ¹³C, and ¹³C‐¹H‐heteronuclear single quantum coherence NMR spectroscopy has confirmed that the hydrolyzed polycitramides with COOH side chains and amide backbones are structurally similar to biodegradable poly(aspartic acid) (PASP). Interestingly, the polycitramides showed Ca²⁺ and Pb²⁺ ion chelating capabilities higher than PASP, citric acid–sorbitol copolymers, or conventional resins. Thus, the polycitramides offer promise as a totally new class of metal sequesters and renewable substitutes for PASP and poly(acrylic acid). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012