Analysis of transient membrane protein interactions by single-molecule diffusional mobility shift assay

Various repertoires of membrane protein interactions determine cellular responses to diverse environments around cells dynamically in space and time. Current assays, however, have limitations in unraveling these interactions in the physiological states in a living cell due to the lack of capability to probe the transient nature of these interactions on the crowded membrane. Here, we present a simple and robust assay that enables the investigation of transient protein interactions in living cells by using the single-molecule diffusional mobility shift assay (smDIMSA). Utilizing smDIMSA, we uncovered the interaction profile of EGFR with various membrane proteins and demonstrated the promiscuity of these interactions depending on the cancer cell line. The transient interaction profile obtained by smDIMSA will provide critical information to comprehend the crosstalk among various receptors on the plasma membrane.Subject terms: Fluorescence imaging, Super-resolution microscopy, Single-molecule biophysics     

Characterization of amiodarone metabolites and impurities using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

Using the high performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/APCI-MS/MS) technique, together with established trends from the literature, the structures of metabolites and impurities of amiodarone, an anti-arrhythmic drug, have been assigned. By comparing analyses of products of incubation with rat liver microsomes with controls in which glucose 6-phosphate dehydrogenase was omitted, metabolites could be distinguished from impurities. Structures for the two proposed metabolites and four impurities are proposed.     

聚N—异丙基丙烯酰胺溶液的温度依赖关系

用自由基聚合法合成了聚Ｎ－异丙基丙烯酰胺（ＰＮＩＰＡＡＭ）样品，用乌氏粘度计考查了该聚合物的四氢呋喃（ＴＨＦ）溶液和水溶液的粘度与温度的依赖关系。发现ＰＮＩＰＡＡＭ－ＴＨＦ体系的特性粘数随温度升高而增大，ＰＮＩＰＡＡＭ－Ｈ２Ｏ体系的特性粘数－温度曲线表现出较为复杂的变化规律。并用实验确定的特性粘数对合成样品的分子量进行了表征Ｍｎ＝８．４４×１０＾５ｇ·ｍｏｌ＾－１。     

Determination of lutetium by fluorimetry, using BPMPHD and CTMAB

Lutetium(III) forms an association compound with a new synthetic reagent, 1,6-bi(1-phenyl-3-methyl-5-pyrazolone-4)hexandione (BPMPHD), and cetyltrimethylammonium bromide (CTMAB). The compound enhances the natural fluorescence of BPMPHD remarkably, upon which a new fluorescence method was developed for determining lutetium in rare earth (RE) samples. The determination range was 1.80 × 10^–7–8.8 × 10^–6 g/ml. The determination limit was 29 ng/ml. The composition of the ion associate was [Lu(BPMPHD)₂]–CTMAB⁺.     

d-xylose transport by Candida succiphila and Kluyveromyces marxianus

The kinetics and regulation of d-xylose uptake were investigated in the efficient pentose fermentor Candida succiphila, and in Kluyveromyces marxianus, which assimilate but do not ferment pentose sugars. Active high-affinity (K _m ∼ 3.8 mM; V _max ∼ 15 nmol/[mg·min]) and putative facilitated diffusion low-affinity (K _m ∼ 140 mM; V _max ∼ 130 nmol/[mg·min]) transport activities were found in C. succiphila grown, respectively, on xylose or glucose. K. marxianus showed facilitated diffusion low-affinity (K _m ∼ 103 mM; V _max ∼ 190 nmol/[mg·min]) transport activity when grown on xylose under microaerobic conditions, and both a low-affinity and an active high-affinity (K _m ∼ 0.2 mM; V _max ∼ 10 nmol/[mg·min]) transport activity when grown on xylose under fully aerobic conditions.     

烟酸对酸性硫酸盐体系铜电沉积的影响

对溶液A: 0.8 mol•L－1硫酸铜,0.6 mol•L－1硫酸,5.0×10－5 mol•L－1氯离子,1.0×10－4 mol•L－1聚乙二醇的溶液,溶液B:在溶液A中加入2.0×10－2 mol•L－1烟酸,pH为0.5,运用循环伏安和计时安培法研究玻碳电极上铜的电沉积行为.结果表明,铜的电沉积过程经历了晶核形成过程,其电结晶按瞬时成核和三维生长方式进行.烟酸的加入对铜的电沉积具有阻化作用,但不改变铜的电结晶机理.沉积层的X射线衍射表明Cu为面心立方结构,在烟酸存在下沉积层出现(220)高择优取向,这可能是烟酸在Cu(220)晶面上发生强烈吸附作用的结果.     

用双氧水绿色氧化环己酮合成己二酸的研究

以30%的双氧水为氧化剂, 钨酸钠与含N或O的双齿有机配体(草酸)形成的络合物为催化剂, 在无有机溶剂、无相转移剂的条件下, 研究了环己酮氧化制己二酸的反应. 研究结果表明, 用廉价的草酸为配体, 最佳反应条件为钨酸钠∶草酸∶环己酮∶30%的双氧水的物质的量比为2.0∶3.3∶100∶350, 在92 ℃下反应12 h, 可制得80.6%的己二酸; 用GC-MS跟踪了氧化过程中三种主要物质环己酮、己内酯及己二酸含量随反应时间的变化关系, 提出了其主要氧化机理为环己酮首先经Beayer-Villiger氧化反应生成己内酯, 己内酯进一步氧化成己二酸.     

CsxH3-xPW12O40的孔结构

Ｎ２静态吸附容量法的测定结果表明，磷钨酸铯盐（ＣｓｘＨ３－ｘＰＷ１２Ｏ４０）的孔窝和孔分布与ｘ值的大小相关。ｘ〈１．５的ＣｓｘＨ３－ｘＰＷ１２Ｏ４０孔容相近，孔分布近似；当ｘ〉１．５时，ＣｓｘＨ３－ｘＰＷ１２Ｏ４０的孔主要是孔径小于１０ｎｍ的中孔和微孔，平均孔径及孔容随ｘ的增加而增大。ＳＥＭ和ＴＥＭ的观测结果表明，ＣｓｘＨ３－ｘＰＷ１２Ｏ４０的孔是微细粒子堆积留下的空隙孔，可能不存在晶内孔。     

NdOx作为助催化剂对PtRu/C电催化氧化甲醇活性的影响

采用沉积-还原法制备了PtRu-NdOx/C催化剂, 借助TEM、EDS和XRD等测试手段对其进行了微结构和组成的表征. 结果表明, 催化剂中Pt与Ru以合金形式存在, 而Nd的氧化物则以无定形形态存在. 催化剂粒子的平均粒径在2 nm左右, 晶胞参数为0.3896 nm, Nd氧化物的加入对PtRu合金的晶体结构影响不明显. 采用循环伏安法和计时电流法, 比较了PtRu-NdOx/C催化剂和PtRu /C催化剂对甲醇氧化的电催化活性, 结果表明, 加入Nd的氧化物作为助催化剂能明显提高PtRu /C催化剂对甲醇氧化的电催化性能.     

β-环糊精与N,N''''-二(4-吡啶基甲基)-1,6-己二胺自组装包结行为的研究

以4-吡啶甲醛和1,6-己二胺为原料,合成了含吡啶基的还原双席夫碱客体N,N'-二(4-吡啶基甲基)-1,6-己二胺(C6N4),通过核磁共振技术研究了β-环糊精与C6N4的自组装包结作用,测定了包结比和稳定常数.结果表明,β-环糊精与客体C6N4在水溶液中形成1∶1的包结配合物,其稳定常数的平均值为1.7×102dm3·mol-1.