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491.
《Analytical letters》2012,45(7):1137-1145
Abstract A molecularly imprinted polymer was prepared using tert-butyloxycarbonyl-L-phenylalanine as the print molecule and methacrylic acid as the functional monomer. The bulk polymer obtained was ground, sieved, packed into a column and investigated in the HPLC-mode by frontal chromatography to determine the number of binding sites and dissociation constants for the enantiomers interacting with the polymer. The dissociation constant for the L-enantiomer of the print molecule was lower than for the D-enantiomer (6.3 mM and 8.1 mM, respectively). This means that the affinity for the L-enantiomer was higher than for the D-enantiomer. The number of binding sites in the polymer giving rise to these dissociation constants were determined to be 28 μmol per g dry polymer. 相似文献
492.
采用共沉淀法制备了高Co含量的Co/SiO2费托合成催化剂,并向其中添加一定含量的间苯二酚-甲醛树脂凝胶.结果表明,催化剂在393K干燥时,树脂会发生分解,因而仅有少量的含碳凝胶残留在催化剂中.然而,少量碳凝胶的存在显著增加了催化剂的还原度和金属钴的分散度,致使催化剂表面产生更多的活性金属Co,同时,催化剂的孔径也有所增大,因此Co/SiO2催化剂具有更高的反应活性及高碳烃选择性.其中80%Co/SiO2-C催化剂活性及高碳烃的选择性与我们前期报道的一种高活性的80%Co-8%ZrO/SiO催化剂相近. 相似文献
493.
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495.
合成与表征了三个系列的Al促进固体强酸样品,并研究了对甲苯的苯甲酰化反应性能.实验表明,SO_4~(2-)/ZrO_2,SO_4~(2-)/TiO_2和SO_4~(2-)/Fe_2O_3中引入适量的Al_2O_3,有助于稳定样品表面的含硫物种,增加样品表面的有效酸位,提高样品的强酸性和对甲苯的苯甲酰化的反应活性.NH_3吸附微量热结果表明,Al促进样品的强酸性和催化活性的显著提高是由于样品表面的酸位强度分布发生了变化,有利于正丁烷异构化反应和苯甲酰化反应的中强酸位和强酸位的酸量显著增加. 相似文献
496.
Leila Ayadi Damien Forget Alain Martelli Jean-François Constant Martine Demeunynck Christian Coulombeau 《Theoretical chemistry accounts》2000,104(3-4):284-289
We use molecular modeling calculations to study the structure and the flexibility of abasic (AP sites) and for the design
of anticancer drugs targeted against AP sites. For either adenine or cytosine on the opposing strand within the same sequence
context, the results are in line with experimental data which show that the two unpaired bases lead to intrahelical forms,
but with differences in induced curvature. Results on flexibility, indicate that the two duplexes have the same bending rigidity
for cytosine. In previous work a series of polyfunctional molecules, such as ATAc, were designed to selectively recognize
and cleave abasic sites in DNA. The nitrobenzamide group which was added to the ATAc molecule to obtain a new molecule, termed
ATAc4, can induce a second lesion under irradiation in close proximity to the abasic site. The different conformations of
ATAc4 interacting with a DNA oligomer containing a stable analog of the abasic site were compared to the photoinduced cleavage
pattern observed experimentally.
Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 12 May 2000 相似文献
497.
An important reason of cancer proliferation is the change in DNA methylation patterns, characterized by the localized hypermethylation of the promoters of tumor-suppressor genes together with an overall decrease in the level of 5-methylcytosine (5mC). Therefore, identifying the 5mC sites in the promoters is a critical step towards further understanding the diverse functions of DNA methylation in genetic diseases such as cancers and aging. However, most wet-lab experimental techniques are often time consuming and laborious for detecting 5mC sites. In this study, we proposed a deep learning-based approach, called BiLSTM-5mC, for accurately identifying 5mC sites in genome-wide DNA promoters. First, we randomly divided the negative samples into 11 subsets of equal size, one of which can form the balance subset by combining with the positive samples in the same amount. Then, two types of feature vectors encoded by the one-hot method, and the nucleotide property and frequency (NPF) methods were fed into a bidirectional long short-term memory (BiLSTM) network and a full connection layer to train the 22 submodels. Finally, the outputs of these models were integrated to predict 5mC sites by using the majority vote strategy. Our experimental results demonstrated that BiLSTM-5mC outperformed existing methods based on the same independent dataset. 相似文献
498.
499.
This study brings a detailed bioinformatics analysis of fungal and chloride-dependent α-amylases from the family GH13. Overall, 268 α-amylase sequences were retrieved from subfamilies GH13_1 (39 sequences), GH13_5 (35 sequences), GH13_15 (28 sequences), GH13_24 (23 sequences), GH13_32 (140 sequences) and GH13_42 (3 sequences). Eight conserved sequence regions (CSRs) characteristic for the family GH13 were identified in all sequences and respective sequence logos were analysed in an effort to identify unique sequence features of each subfamily. The main emphasis was given on the subfamily GH13_32 since it contains both fungal α-amylases and their bacterial chloride-activated counterparts. In addition to in silico analysis focused on eventual ability to bind the chloride anion, the property typical mainly for animal α-amylases from subfamilies GH13_15 and GH13_24, attention has been paid also to the potential presence of the so-called secondary surface-binding sites (SBSs) identified in complexed crystal structures of some particular α-amylases from the studied subfamilies. As template enzymes with already experimentally determined SBSs, the α-amylases from Aspergillus niger (GH13_1), Bacillus halmapalus, Bacillus paralicheniformis and Halothermothrix orenii (all from GH13_5) and Homo sapiens (saliva; GH13_24) were used. Evolutionary relationships between GH13 fungal and chloride-dependent α-amylases were demonstrated by two evolutionary trees—one based on the alignment of the segment of sequences spanning almost the entire catalytic TIM-barrel domain and the other one based on the alignment of eight extracted CSRs. Although both trees demonstrated similar results in terms of a closer evolutionary relatedness of subfamilies GH13_1 with GH13_42 including in a wider sense also the subfamily GH13_5 as well as for subfamilies GH13_32, GH13_15 and GH13_24, some subtle differences in clustering of particular α-amylases may nevertheless be observed. 相似文献
500.
温和条件下将CO2电催化还原(CO2RR)为高能量密度燃料和高附加值碳产品是降低大气中CO2浓度、储存间歇性可再生能源、实现碳中和的重要途径之一。设计和开发对电催化CO2RR兼具高活性、高选择性、高稳定性、且对析氢反应(HER)具有显著抑制作用的高性能廉价催化剂是CO2RR研究的关键。单原子催化剂(SACs)由于其独特的电子结构和几何结构对许多重要化学反应(如CO氧化反应、加氢反应、析氧反应、氧还原反应、析氢反应等)显示出优异的催化活性而广受关注。近年来,N掺杂多孔碳载体过渡金属单原子催化材料(M-N-C)显示出对电化学二氧化碳还原的广阔前景、并有望成为在水相电解质中还原CO2的贵金属(Au,Ag)催化剂的替代品。本文从单原子催化材料M-N-C的制备、影响电催化性能的因素及MNx活性基团三个方向介绍了单原子催化剂M-N-C电催化CO2RR的研究现状和进展。最后,就目前该方向研究中尚待解决的问题进行了总结、并对下一步的研究进行了展望。 相似文献