Directed peptide assembly at the lipid-water interface cooperatively enhances membrane binding and activity

We modified membrane-active peptides with synthetic recognition modules to foster peptide assembly at the lipid-water interface. The designed recognition strategy has been previously reported: tris-cyanuric acid and tris-melamine have been found to bind selectively to each another when membrane-anchored. We designed this interaction to occur between two membrane-active peptides, forming a heteromeric complex at the lipid-water interface that exhibits superior membrane binding and permeation compared to the monomeric peptides, presumably because of the higher avidity of the assembled structure. These conjugates do not assemble appreciably in solution but assemble at the lipid-water interface, with surface binding of the peptide acting cooperatively with molecular recognition to yield improved binding and permeation. Furthermore, we find that specific recognition between tris-cyanuric acid phospholipid (TCA-PE) at low surface concentration and tris-melamine magainin (TMM) or hexa-melamine magainin (HMM) results in highly lytic binding, whereas no binding is detectable in the absence of lipid recognition. These findings suggest a noncovalent strategy to enhance peptide membrane activity, which may lead to the discovery of more potent surface-active agents such as antimicrobials.     

OFFGEL isoelectric focusing and polyacrylamide gel electrophoresis separation of platinum-binding proteins

In this work a 2D electrophoretic separation procedure able to maintain the integrity of platinum-protein bonds has been developed. The method is based on the use of sequential OFFGEL isoelectric focussing (IEF) and PAGE. A systematic study of the reagents used for PAGE, for OFFGEL-IEF separation, and post-separation treatment of gels (such as enzymatic digestion and sample preparation for MS analysis) was tackled regarding their suitability for the identification of platinum binding proteins using standard proteins incubated with cisplatin. The distribution of platinum in high and low molecular weight fractions (separated by cut-off filters) was determined by ICP-MS, which allows evaluating platinum-protein bond stability under the conditions studied. SDS-PAGE in the absence of β-mercaptoethanol or dithiotreitol preserved the platinum-protein bonds. In addition, neither the influence of the electric field during the electrophoretic separation, nor the processes of fixing, staining and destaining of proteins in the gel did result in the loss of platinum from platinum binding proteins. SDS-PAGE under non-reducing conditions provides separation of platinum-binding proteins in very narrow bands with quantitative recoveries. Different amounts of platinum-bound proteins covering the range 0.3-2.0 μg were separated and mineralised for platinum determination, showing good platinum linearity. Limits of detection for a mixture of five standard proteins incubated with cisplatin were between the range of 2.4 and 13.9 pg of platinum, which were satisfactory for their application to biological samples. Regarding OFFGEL-IEF, a denaturing solution without thiourea and without dithiotreitol is recommended. The suitability of the OFFGEL-IEF for the separation of platinum binding proteins of a kidney cytosol was demonstrated.     

Palladium-catalyzed approach to stereodefined ten-membered cycles from 1,5-bisallenes

A three-component Pd(0)-catalyzed reaction of 1,5-bisallenes with organic halides in the presence of primary amines was observed to afford stereodefined not readily available ten-membered cyclic compounds highly chemo- and regioselectively. A mechanism involving two π-allylic palladium intermediates was proposed to account for the observed regio- and stereoselectivity.     

高能球磨和低温烧结制备高电位梯度ZnO厚膜压敏电阻

通过高能球磨和低温烧结,制备出高电位梯度的ZnO厚膜压敏电阻,并研究了烧结温度对厚膜试样电学性能的影响.结果表明,高能球磨可显著细化粉体颗粒,球磨后颗粒的平均尺寸减小到0.420μm;颗粒的高度细化促使厚膜可在650-850℃的低温范围烧结成瓷,其中在700℃的烧结条件下,厚膜试样的综合性能最佳,电位梯度达到3175.6 V·mm-1,漏电流为30.7μA,非线性系数为13,微观势垒高度为0.79eV,耗尽层宽度为14.4nm,施主浓度为2.24×1018cm-3,表面态密度为3.22×1012cm-2.     

用鲁米诺-KIO4-Fe(1, 10-phen)32+体系的化学发光法测定痕量铁

本文利用鲁米诺-KIO₄-Fe(1,10-phen)₃²⁺配合物体系产生化学发光反应,建立了测定痕量铁的新的化学发光分析方法.该法以1,10-phen为配位体,铁的检出限为1.6×10^-7g/L,工作曲线响应浓度范围在1×10^-5-1×10^-3g/L.在测定2×10^-4g/L铁的相对标准偏差为3.5%.用于检测工业沉淀BaSO₄中痕量铁获得满意结果.     

Thermodynamic properties of aqueous mixtures of LiCl and Li2SO4 at different temperatures

Emf measurements were made on the cell without liquid junction: Li?ISE LiCl(m₁), Li₂SO₄(m₂) Ag/AgCl. The performances of the electrode pairs constructed in our laboratory were tested and exhibited near-Nernstian behavior. The mean activity coefficients of LiCl for the system Li⁺?Cl^??SO ₄ ^2? ?H₂O have been investigated by the emf values at temperatures of 0, 15, 35°C and constant total ionic strengths of 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 and 5.0 mol·kg^?1. The activity coefficients decrease with increasing temperature and the ionic strength fraction of Li₂SO₄ in the mixtures. The thermodynamic properties are interpreted by use of Harned's empirical equations and Pitzer's ion interaction approach including the contribution of higher order electrostatic terms. The experimental results obey Harned's rule and are described by using Pitzer equations satisfactorily. The activity coefficients of Li₂SO₄, the osmotic coefficients and the excess free energies of mixing for the system in the experimental temperature range were reported.     

ZnCl2熔盐的分子动力学模拟

近年来，若干作者根据几种粒子间函数，对ZnCl2熔盐结构做过分子动力学模拟［1－3］其出的Zn－Cl和Cl－Cl离子间的偏径向分布函数与中子衍射实测值符合较好，但Zn－Zn离子间距以及Zn－Zn间配位数计算值多偏高．鉴于Busing势函数在多价卤化物馆盐的分子动力学计算中应用效果较好[4],我们试用Busing势函数为基础对ZnCl2熔盐结构和能量做分子动力学计算．1研究方法计算所用粒子势为Busing势函数此处，Zi为离子的电行数（ZZn。＋＝2，Zcl－＝1），几；是离子有效半径，人为＊离子的“硬度”参数·据文献问，f二0．005071，尸zn。十二0．…     

壳聚糖衍生物的制备及其吸附性能

壳聚糖衍生物的制备及其吸附性能曲荣君，马千里，郑秀丽，孙言志（烟台师范学院化学系烟台２６４０２５）关键词壳聚精衍生物，制备，吸附壳聚糖（ＣＴＳ）是重金瞩离子的吸附剂￣［１，２］，由于壳聚精分子中的－ＮＨ＿２在ｐＨ较低的水溶液易形成而使ＣＴＳ溶于水，造...     

三氯化一缬氨酸六水合稀土固体配合物的合成及红外光谱

在水溶液中合成了Ｌｎ（Ｖａｌ）·Ｃｌ＿３·６Ｈ＿２Ｏ（Ｌｎ＝Ｌａ，Ｎｄ，Ｓｍ，Ｇｄ，Ｅｒ）．利用元素分析和容量滴定法确定了其组成。测定了配合物的红外光谱，对其主要红外吸收带进行了归属。红外光谱结果表明，缬氨酸以内盐的形式存在于配合物中，并通过羟基与稀土离子配位，６个水分子亦参与了配泣，推测Ｌａ和Ｎｄ配合物具有一维无限长锭结构，而Ｓｍ、Ｇｄ和Ｅｒ配合物为双核配合物．     

气相色谱—微波等离子体发射光谱法研究农药1605与人唾液的相互作用

用ＧＣ－ＡＥＤ联用技术研究了农药１６０５，得到１６０５所含六种元素的元素色谱图，并用该方法研究了人唾液与１６０５的相互作用。