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Investigating interactions of the Bacillus subtilis spore coat proteins CotY and CotZ using single molecule force spectroscopy
No full textSpores formed by Bacillus subtilis are surrounded by a protective and multilayered shell, termed the coat, which grants the spores resistance to various environmental stresses and facilitates spore germination. The spore coat consists of more than seventy different proteins, arranged into at least four distinct structural layers: the undercoat, inner coat, outer coat and crust. However, how these proteins, especially the morphogenetic proteins, interact to establish the organized, functional coat layers remains poorly understood. CotY and CotZ as the components of the crust, play a morphogenetic role in the crust assembly around the spore. In this study, the single molecule force spectroscopy was used to investigate the interaction and dynamics between CotY and CotZ at the single-molecule level. The results show that homotypic interactions of CotY and CotZ and the heterotypic interaction between CotY and CotZ exist. Furthermore, the dissociation kinetics of the complexes were studied by monitoring the relationship between the unbinding forces and the loading rates at different pulling velocities. In this way, a series of kinetic parameters regarding the three different complexes were obtained. It revealed the strong interactions between CotY and CotZ, CotY and CotY, and a relatively weak interaction of CotZ and CotZ. (C) 2015 Elsevier Inc. All rights reserved
Synthesis and characterization of cyclic bisphenol A (phenylene phosphonate) oligomer and its flame retardancy application
No full textA novel solid flame retardant cyclic bisphenol A (phenylene phosphonate) (CPBA) oligomer was synthesized in high yields by the reaction of phenylphosphonic dichloride with bisphenol A under pseudohigh-dilution conditions via polycondensation. Detailed structural characterizations of this oligomer were conducted using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, H-1 NMR, P-31 NMR and FTIR. Furthermore, the flame-retardant efficiency of this oligomer in polybutylene terephthalate (PBT) was investigated using limiting oxygen index (LOI) and UL-94 tests. After the addition of 25 wt.% CPBA, the LOI increased from 20.2% to 28.6% and the UL-94 V-0 rating was achieved. Thermogravimetric analysis, FTIR, and Pyrolysis/GC/MS were employed to elucidate the pyrolysis behavior of CPPA and PBT/CPBA. Results showed that the CPBA oligomer could change the degradation path of PBT and improved the char formation of the PBT/CPBA systems. The residual morphologies of residues of the PBT/CPBA25% system were investigated by scanning electron microscopy (SEM). SEM investigations revealed that the residual chars containing polyphosphoric or phosphoric acid, which plays an important role in the process of carbonization. The influence of CPBA content on the mechanical properties of PBT/CPBA blends was also discussed. (C) 2015 Elsevier Ltd. All rights reserved
碳基三维自支撑超级电容器电极材料研究进展
Get PDF自支撑电极材料在超级电容器中有着广泛的应用.碳材料具有结构多样、来源丰富、价格低廉以及性能稳定等优点,是构建三维自支撑电极材料的首选基底材料.本文结合作者课题组的研究工作,从"由上而下"和"由下而上"两个方面,概述了设计、制备三维自支撑电极材料的常用方法及材料的电容性能,希望对开发利用天然可再生资源,制备高性能的自支撑电极材料及其在超级电容器材料中的应用有所帮助
PDLA-PBS-PDLA三嵌段共聚物的合成及性能
Get PDF合成了末端均为羟基的聚丁二酸丁二醇酯(PBS)预聚物,再以PBS的端羟基引发D-丙交酯(D-LA)开环聚合,得到聚右旋乳酸(PDLA)与PBS的三嵌段共聚物(PDLA-PBS-PDLA).通过凝胶渗透色谱和核磁共振氢谱进行了结构表征.随着m(D-LA)∶m(PBS)由0.51∶1逐渐增加至2.60∶1,PDLA-PDS-PDLA中PDLA链段的长度逐渐增加.随着PDLA嵌段长度的增加,PDLA嵌段对PBS嵌段的限制作用增强,并导致PBS嵌段结晶温度下降,结晶焓降低.当m(D-LA)∶m(PBS)=2.60∶1时,PBS嵌段不再能形成结晶.而m(D-LA)∶m(PBS)在0.51∶1~3.04∶1范围内,PDLA嵌段均可形成结晶,PDLA嵌段的熔点随其在嵌段共聚物中含量的增加而逐渐升高,但PDLA嵌段的熔融焓呈现先增加后降低的趋势.在部分嵌段共聚物中,PBS和PDLA嵌段可各自形成结晶,且PBS和PDLA的结晶结构不随组分的变化而发生改变,表明该嵌段共聚物中PDLA嵌段和PBS嵌段呈微相分离结构
三层共挤聚乙烯/聚丙烯/聚乙烯上吹薄膜的研究
No full text采用马来酸酐(MAH)接枝改性乙烯-辛烯共聚物(POE-g-MAH)对聚丙烯(PP)进行增韧改性,用增韧后的PP和聚乙烯(PE)采用三层共挤上吹技术制备了聚乙烯(PE)/聚丙烯(PP)/聚乙烯(PE)薄膜;探讨了不同含量的POE-g-MAH对三层共挤薄膜力学性能、流变性能、热稳定性能的影响,并通过扫描电子显微镜观察其撕裂断面形态。结果表明,POE-g-MAH的加入,提高了薄膜的撕裂强度和热稳定性;PP熔体强度差的问题也得到了改善;薄膜力学性能与形态学密切相关,MPOE的加入使得吹膜材料的相容性得到更好的提高
液相色谱-质谱联用技术结合多探针底物法研究人参皂苷Rb1的体外代谢
No full text以奥美拉唑、苯妥英、卡马西平和非那西丁为检测肝药酶细胞色素P450酶(CYP450)亚型的专属探针药物,通过原型药物减少量测定法考察药物体外代谢的变化,评价人参皂苷Rb1对CYP450不同亚型酶的作用.结果表明,P2C9,P2C19和P3A4实验组与对照组差异不显著,P1A2实验组与对照组差异显著,表明人参皂苷Rb1能诱导P1A2亚型酶的活性,促进底物与酶反应,加快底物的代谢,而对P2C9,P2C19和P3A4三个亚型酶有弱的诱导或无诱导作用.根据快速分离液相色谱-质谱联用(RRLC-MS/MS)检测结果推断,人参皂苷Rb1在CYP450酶中的代谢产物可转化为人参皂苷Rb1氧化产物(Rb1+O)及人参皂苷Rd和F2
刚性聚酰亚胺的分子堆积和热膨胀性能研究
No full text聚酰亚胺是一类高强、耐热、低介电常数特种工程材料,已在微电子领域广泛应用。因其热膨胀系数高于无机导电层,其作为集成线路板基膜材料时易与导电层剥离分层。在聚酰亚胺分子结构中引入刚性链段是降低热膨胀系数的有效方法。本文从2,5-二氨基苯基吡啶和2,5-二氨基苯基嘧啶合成了2种刚性聚酰亚胺,对其热性能和机械性能进行了表征。结果表明,此类刚性聚酰亚胺比普通聚酰亚胺具有更紧密的分子堆积,从而呈现出高密度、低热膨胀以及很好的耐热性和机械性能。另外,通过理论计算比较了聚酰亚胺堆砌系数与热膨胀系数的相关性,这些理论计算的堆砌系数可以较好的预测刚性聚酰亚胺的热膨胀性能
基于微悬臂梁生物传感器检测三磷酸腺苷
Get PDF基于适配子构建了无标记检测三磷酸腺苷(ATP)的微悬臂梁生物传感器。将ATP适配子修饰在微悬臂梁阵列中的传感悬臂镀金面上,用来识别ATP,而参比悬臂修饰巯基己醇(MCH)防止非特异性吸附。ATP与其适配子发生特异性相互作用,使悬臂的上下两个表面产生应力差,导致传感悬臂产生偏转,扣除参比悬臂偏转后其偏转值与ATP的浓度在0.5~5 mmol/L范围内有良好的线性关系,相关系数为0.998,最低检出限为0.06 mmol/L。该微悬臂梁生物传感器响应快速、操作简单,并且对ATP具有良好的特异性
PVC搪塑专用料及制品中无机粒子均匀分散的工艺方法
No full text本发明涉及PVC搪塑专用料及制品中无机粒子均匀分散的工艺方法,并以不影响PVC颗粒对增塑剂的吸收作为前提条件。通过在通常的干混工艺——热混、冷却、冷混、后处理等阶段之前增设室温混合阶段,并对室温混合时的转速、时间和温度进行优选,找出使无机纳米粒子分布最为均匀的工艺条件为高速短时室温混合
一种聚(碳酸酯-醚)多元醇的制备方法
No full text本发明提供了一种聚(碳酸酯-醚)多元醇的制备方法,包括：将羧酸和环氧化物进行反应,得到中间产物；所述羧酸的酸度常数为0.2～4；在Zn3[Co(CN)6]2的稀土掺杂双金属氰化物的作用下,将所述中间产物和二氧化碳进行聚合反应,得到聚(碳酸酯-醚)多元醇。本发明提供的聚(碳酸酯-醚)多元醇的制备方法,采用酸度常数适宜的羧酸作为起始剂,先采用羧酸对环氧化物进行活化,将活化后原位产生的不同分子量的聚醚作为链转移剂,在Zn3[Co(CN)6]2的稀土掺杂双金属氰化物的作用下,参与二氧化碳和环氧化物的聚合反应,这种聚(碳酸酯-醚)多元醇的制备方法反应时间较短,而且产物中的副产物碳酸丙烯酯含量较低