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以聚丙烯(PP)为基体树脂,乙丙橡胶(EPDM)为增韧剂,滑石粉为填料,加入钛酸酯类偶联剂CT-114、抗氧剂1010、抗氧剂168和受阻胺类光稳定剂770,制得汽车内饰专用改性PP。研究了PP种类及用量、增韧剂种类及用量、滑石粉粒径、CT-114及抗老化剂对PP性能的影响。结果表明:当w(PP)(牌号M2600R)为52.0%,w(PP)(PP粉料,牌号040)为12.0%,w(EPDM)(牌号3722P)为9.0%,w(CT-114)为0.8%,粒径为2μm的滑石粉质量分数23.5%,抗氧剂1010、抗氧剂168、光稳定剂770总质量分数为0.5%,白油质量分数为0.2%,色母粒质量分数为2.0%时,制备的改性PP能满足汽车内饰件各项性能指标要求,且放大生产后,下游客户成功进行试用。 相似文献
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利用多种功能添加剂复合改性聚丙烯(PP),制成高韧性高模量PP。从几种PP组合中优选出综合性能最好的两种PP共混体系,研究了不同增韧剂及其用量、镁盐晶须作为增刚剂及其用量对PP着色专用料性能的影响,并选用环保型彩色混相无机颜料作为主着色剂。结果表明:以两种PP(K7726、K8303)为基体树脂,POE(8150型)与β晶型成核剂为增韧剂,经偶联剂处理的镁盐晶须为增刚剂,并用两步法动态硫化改性PP,当PP、POE与镁盐晶须三者的质量比为67:18:15时,改性PP的缺口冲击强度达到42.1 kJ/m~2,弯曲弹性模量为1 420 MPa,拉伸强度为18.6 MPa,达到了适用于类似汽车保险杠等制品的较高性能指标。 相似文献
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三元乙丙橡胶共混改性聚丙烯 总被引:9,自引:0,他引:9
分别用茂金属催化聚合所得的三元乙丙橡胶(mEPDM)和传统Ziegler-Natta催化剂聚合所得的三元乙丙橡胶(EPDM)对PP进行共混改性。考察了增韧剂质量分数对共混物冲击强度、拉伸强度和热变形温度等力学性能的影响,以及共混物结构形态和结晶行为。结果表明,与PP/EPDM共混物相比,PP/mEPDM共混物的脆韧转变增韧剂临界质量分数小,扯断伸长率高。PP/mEPDM共混物的脆韧转变区间远小于PP/EPDM共混物。随增韧剂质量分数的增加,PP/mEPDM和PP/EPDM共混物的拉伸强度、弹性模量和维卡软化点均单调下降,但后者的下降幅度更大。电镜分析和结晶行为研究表明,PP与mEPDM的相容性优于PP与EPDM的。 相似文献
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该文根据欧盟2000年公布的第五版和2002年公布的第六版《欧洲化学物质申报清单》,选择一些重要的染料品种,介绍了他们的化学名称,以及可供参考的结构式。 相似文献
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Trabbic-Carlson K Meyer DE Liu L Piervincenzi R Nath N LaBean T Chilkoti A 《Protein engineering, design & selection : PEDS》2004,17(1):57-66
The limited throughput, scalability and high cost of protein purification by chromatography provide motivation for the development of non-chromatographic protein purification technologies that are cheaper and easier to implement in a high-throughput format for proteomics applications and to scale up for industrial bioprocessing. We have shown that genetic fusion of a recombinant protein to an elastin-like polypeptide (ELP) imparts the environmentally sensitive solubility property of the ELP to the fusion protein, and thereby allows selective separation of the fusion protein from Escherichia coli lysate by aggregation above a critical temperature (T(t)). Further development of ELP fusion proteins as widely applicable purification tools necessitates a quantitative understanding of how fused proteins perturb the ELP T(t) such that purification conditions (T(t)) may be predicted a priori for new recombinant proteins. We report here the effect that fusing six different proteins has on the T(t) of an ELP. A negative correlation between T(t) and the fraction hydrophobic surface area on the fused proteins was observed, which was determined from computer modeling of the available three-dimensional structure. The thermally triggered aggregation behavior of ELP-coated, functionalized gold colloids as well as ligand binding to the tendamistat-ELP fusion protein support the hypothesis that hydrophobic surfaces in molecular proximity to ELPs depress the ELP T(t) by a mechanism analogous to hydrophobic residue substitution in the ELP repeat, Val-Pro-Gly-Xaa-Gly. 相似文献
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An efficient method for creation and functional analysis of libraries of hybrid type I polyketide synthases 总被引:1,自引:0,他引:1
Bacterial type I polyketide synthases (PKSs) generate a structurally diverse group of natural products with a wide range of biological activities. Hybrid type I PKSs in which domains of one multifunctional polypeptide are replaced with components from heterologous systems have generated significant interest over the past decade. Almost invariably only one or several specific hybrids are made at a time and tested for functionality. This approach is slow, dependent upon a fortuitous choice of specific fusions points, and often leads to inactive or minimally active hybrid systems. We describe herein a method for generating and screening a library of hybrid pikAI complementation plasmids (encoding the loading domain and the first two extension domains of pikromycin PKS) able to restore pikromycin in a BB138 Streptomyces venezuelae pikAI-deletion mutant. In the first step the plasmid sequence encoding the loading domain AT(0)-ACP(0) was replaced by a counter selectable marker, sacB. DNA family shuffling was then used to generate a diverse library of chimeric AT(0)-ACP(0) fragments, which were used to replace sacB by lambda-Red-mediated in vivo recombination in an Escherichia coli host. This method resulted in the rapid and efficient generation of a large number of hybrid pikAI complementation plasmids, which were used to transform S.venezuelae BB138. A bioassay of over 4000 of these transformants successfully revealed three different PikAI hybrids which were able to lead to pikromycin production. The study suggests that most of the hybrids are not detectably functional, and underscores the need to generate and screen large and diverse libraries in which different fusion points are tried. The methodologies applied in this study address this need and can be used for directed evolution of any component of the PikPKS, and potentially other type I PKS systems. 相似文献
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Emulsion formulations used for in vitro compartmentalization (IVC) methods were found to be incompatible with protein expression in the rabbit reticulocyte (RRL) system, causing rapid discoloration and translation shutdown. Here we identify possible causes and describe a novel water-in-oil emulsion which abolished discoloration and allowed high-level in-emulsion expression of active luciferase and human telomerase using the RRL. This novel emulsion greatly expands the range of potential protein targets for IVC. 相似文献
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Algerian oil well deposit derived asphaltene fraction was characterized by different MAS/NMR sequences to investigate asphaltene aromaticity and the best cross-polarization contact time. The aromaticity was estimated by single pulse sequence (SP), Hahn-echo (HE), cross-polarization (CP) and variable cross-polarization (VACP) sequences. The values found ranging from 0.58 to 0.48 are of the same order of magnitude as ones published in the literature. The discrepancies between the values are thought to be relevant to both the specificity of each sequence and the asphaltene structure. Spectra band de-convolution enables us the determination of the average number of carbon atoms per side chain according to each sequence. The obtained values spanning from 3 to 7 are also sequence nature dependent. 相似文献
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Identification of potent human anti-IL-1RI antagonist antibodies 总被引:4,自引:0,他引:4
Fredericks ZL Forte C Capuano IV Zhou H Vanden Bos T Carter P 《Protein engineering, design & selection : PEDS》2004,17(1):95-106
Interleukin-1 (IL-1) blockade by IL-1 receptor antagonist benefits some arthritis patients by reducing joint damage. This fact inspired us to develop antagonist human therapeutic antibodies against IL-1R(I) using phage libraries that display single-chain variable fragment (scFv) antibody fragments. Panning libraries against human IL-1R(I) generated 39 unique scFv-phage whose binding to IL-1R(I) was competed by IL-1 ligands. Fifteen of these scFv-phage, identified using IL-1R(I)-binding assays and dissociation rate ranking, were reformatted as scFv-Fc and IgG(4) molecules. The ease of producing antibodies in the scFv-Fc format permitted rapid identification of four lead clones (C10, C13, C14, C15) that inhibit NF-kappaB nuclear translocation induced by IL-1. Reformatting these clones as IgG(4) molecules increased their inhibition potency by =24-fold. C10 IgG(4) is the most potent antagonist of IL-1alpha (26 nM IC(50)) and IL-1beta (18 nM IC(50)) in the NF-kappaB bioassay, although less potent than IL-1ra ( approximately 0.4 nM IC(50)). C10 is the highest affinity clone for human IL-1R(I) (K(D) approximately 60 nM). Flow cytometry indicates that several lead clones bind cell-surface cynomolgus or murine IL-1R(I), characteristics advantageous for preclinical toxicology and efficacy studies. This study demonstrates the utility of scFv-Fc fusion proteins for rapid screening of clones derived from phage libraries to identify antibody leads with therapeutic potential. 相似文献
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Improved activity and thermostability of Candida antarctica lipase B by DNA family shuffling 总被引:2,自引:0,他引:2
Suen WC Zhang N Xiao L Madison V Zaks A 《Protein engineering, design & selection : PEDS》2004,17(2):133-140
DNA family shuffling was used to create chimeric lipase B proteins with improved activity toward the hydrolysis of diethyl 3-(3',4'-dichlorophenyl)glutarate (DDG). Three homologous lipases from Candida antarctica ATCC 32657, Hyphozyma sp. CBS 648.91 and Crytococcus tsukubaensis ATCC 24555 were cloned and shuffled to generate a diverse gene library. A high-throughput screening assay was developed and used successfully to identify chimeric lipase B proteins having a 20-fold higher activity toward DDG than lipase B from C.antarctica ATCC 32657 and a 13-fold higher activity than the most active parent derived from C.tsukubaensis ATCC 24555. In addition, the stability characteristics of several highly active chimeric proteins were also improved as a result of family shuffling. For example, the half-life at 45 degrees C and melting point (T(m)) of one chimera exceeded those of lipase B from C.antarctica ATCC 32657 by 11-fold and 6.4 degrees C, respectively, which closely approached the stability characteristics of the most thermostable parent derived from Hyphozyma sp. CBS 648.91. 相似文献
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Shim JH Kim YW Kim TJ Chae HY Park JH Cha H Kim JW Kim YR Schaefer T Spendler T Moon TW Park KH 《Protein engineering, design & selection : PEDS》2004,17(3):205-211
In an effort to improve the properties of cyclodextrin glucanotransferase (CGTase) as an antistaling enzyme, error-prone PCR was used to introduce random mutations into a CGTase cloned from alkalophilic Bacillus sp. I-5 (CGTase I-5). A mutant CGTase[3-18] with the three mutations M234T, F259I and V591A was selected by agar plate assay. Sequence alignment of various CGTases indicated that M234 and F259 are located in the vicinity of the catalytic sites of the enzyme and V591 in the starch binding domain E. The cyclization activity of CGTase[3-18] was dramatically decreased by 10-fold, while the hydrolyzing activity was increased by up to 15-fold. These mutations near subsite +1 (M234T) and at subsite +2 (F259I) are likely to alter the enzyme activity in a concerted manner, promoting hydrolysis of substrate while retarding cyclization. The addition of CGTase[3-18] reduced the retrogradation rate of bread by as much as did the commercial antistaling enzyme Novamyl during 7-day storage at 4 degrees C. No cyclodextrin (CD) was detected in bread treated with CGTase[3-18], whereas 21 mg of CD per 10 g of bread was produced in bread treated with wild-type CGTase. 相似文献
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Mutations that cause X-linked agammaglobulinemia (XLA) appear throughout the Bruton tyrosine kinase (Btk) sequence, including the pleckstrin homology (PH) domain. To analyze the basis of this disease with respect to protein structure, we studied the relationships between PH domain sequences and structures by comparing sequence-based profiles of physicochemical properties and solvent accessibility profiles. The diversity of the distribution of amino acids was measured by calculating entropies for sequences containing mutations at different positions in multiple sequence alignments. Mutual information was calculated to quantify positional covariation. Eight conserved extrema were apparent in all profiles. The majority of the XLA disease-causing mutations in the Btk PH domain were found at positions having significant mutual information, indicating that there are covariant constraints for both structure and function. Together with additional structural analyses, all the XLA mutations that were analyzed could be explained at the molecular level. The method developed here is applicable to the design of mutations for protein engineering. 相似文献