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141.
Peng Yang Xuan Wang Bo Li Yixuan Yang Jinfeng Yue Yanrui Suo Huarong Tong Gang He Xiaojie Lu Gong Chen 《Chemical science》2021,12(16):5804
A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed. The method exhibits a broad substrate scope for thiols, aryl iodides and amino acid units. Peptide macrocycles of a wide range of size and composition can be readily assembled in high yield from various easily accessible building blocks. This method has been successfully employed to prepare an 8-million-membered tetrameric cyclic peptide DNA-encoded library (DEL). Preliminary screening of the DEL library against protein p300 identified compounds with single digit micromolar inhibition activity.A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed. 相似文献
142.
Lianghui Gao Mengjie Gong Fanbo Kong Ting Yuan Xiaohong Li Lili Zu Yunchao Li Louzhen Fan 《大学化学》2020,35(5):81-87
During the fight against the new coronavirus epidemic, the "Physical Chemistry" team of Beijing Normal University used various network platforms and tools, such as MOOC of China University, Rain Classroom and WeChat Group in the teaching process. The exploration and practice of online learning of "Physical Chemistry" is carried out based on MOOC teaching, with student learning as the center and teacher guidance as the support. Taking the most difficult chapter of "fundamentals for statistical thermodynamic" as an example, we designed a complex teaching program that includes previews, watching MOOC videos in class, real-time online exercises, teachers' answers, and after-class reflection and questioning. The students were encouraged to learn independently through the reserved information, designed activities and assignments. Practice shows that the online course has cultivated the students' self-management ability, trained their critical thinking skills, and achieved good teaching results. 相似文献
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144.
基于在生理、催化等方面研究中的重要作用,H_2Pc分子的电子结构一直受到广泛的注意和研究。但是,理论上算出的电荷分布与实验上测出的NIS XPS信息,目前还不相符。为此,本文用CNDO/2计算方法,对应H_2Pc的文献几何构型,进一步考察了H_2Pc与H_2Pc'的电子结构。计算方法和结果H_2Pc和H_2Pc'的骨架构型见图1。对于固态与气态的H_2Pc,目前多数人认为其具有D_(2h)点群对称性(尽管作为D_(4h)点群对称性的根据也是存在的)。为考察分子构型改变(特别是切割)对分子的电子结构、特别是电荷分布的影响,我们 相似文献
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147.
Wei-Cho Huang Cheng S. Gong George T. Tsao 《Applied biochemistry and biotechnology》2003,106(1-3):471-480
Pressure pulsation (PP) was investigated for its effects on oxygen transfer rate (OTR) measured by sulfite oxidation. By manipulating
airflow rate, 0.41–1.2 vvm, and a control valve in a 4-L bioreactor, the frequency of PP was varied at different gas pressures3–15
psig. A mathematical model of OTR was built and compared to experimental data. OTR was also examined at constant gas pressure,
4.5–15.0 psig. The results indicate a good agreement between measurement and model prediction. OTR above 9 psig during PP
showed significant enhancement at 25°C. This proves that PP not only affects the elevation of DO level, but also increases
the interfacial area and mass transfer coefficient. 相似文献
148.
Based on the theory of stochastic resonance, a new method carried on the quantitive analysis to weak chromatographic signal of glyburide in plasma, which was embedded in the noise background and the signal-to-noise ratio (SNR) of HPLC-UV is enhanced remarkably. This method enhances the quantification limit to 1 ng ml−1, which is the same as HPLC-MS, and makes it possible to detect the weak signal accurately by HPLC-UV, which was not suitable before. The results showed good recovery and linear range from 1 to 50 ng ml−1 of glyburide in plasma and the method can be used for quantitative analysis of glyburide. 相似文献
149.
Chen Chee-Shan Chan E. Wang S. L. Gong C. S. Chen L. F. 《Applied biochemistry and biotechnology》1994,(1):531-544
A self-aggregating strain ofSaccharomyces uvarum (U4) was used as a biocatalyst to carry out continuous ethanol fermentation in a tower fermentor equipped with a cell separator.
Cell aggregates (2–3 mm) formed a stable packed bed in the fermentor, and the cell separator retained yeast cells effectively.
Corn steep liquor was used as a nitrogen source for the fermentation of corn syrup and black strap molasses. An ethanol productivity
of 54 g/L/h was reached using corn syrup at a dilution rate of 0.7/h, and sugar concentration in the feed was 15% (w/v). For
molasses fermentation, an ethanol productivity of 22 g/L/h was obtained at a dilution rate of 0.7/h, and sugar concentration
in the feed was 12.5% (w/v). Ethanol yields obtained from tower fermentation are higher than those obtained from flask fermentation
(96% for corn syrup fermentation and 92% for molasses fermentation). No significant loss in fermentation activity was observed
after 3 mo of operation. 相似文献
150.
Five different pure density functional theory (DFT) and hybrid Hartree-Fock/DFT methods have been used to search for the molecular structures, thermochemistry, and electron affinities of the bromine hydrogen fluorides HBrF(n)/HBrF(n)(-) (n = 2, 4). The basis sets used in this work are of double-zeta plus polarization quality in conjunction with s- and p-type diffuse functions, labeled as DZP++. Structures with Br-F and Br-H normal bonds, that is, HBrF(2)/HBrF(2)(-) with C(2v) or C(s) symmetry and HBrF(4)/HBrF(4)(-) with C(4v) or C(s) symmetry, are genuine minima. However, unlike the original BrF(3) and BrF(5) molecules, the global minima for HBrF(n)/HBrF(n)(-) (n = 2, 4) species are predicted to be complexes, some of which contain hydrogen bonds. The demise of the hypervalent structures is due to the availability of favorable dissociation products involving HF, which has a much larger dissociation energy than F(2). Similar reasoning suggests that PF(4)H, SF(3)H, SF(5)H, ClF(2)H, ClF(4)H, AsF(4)H, SeF(3)H, and SeF(5)H will all be hydrogen bond structures incorporating diatomic HF. The most reasonable theoretical values of the adiabatic electron affinities (EA(ad)) are 3.69 (HBrF(2)) and 4.38 eV (HBrF(4)) with the BHLYP method. These electron affinities are comparable to those of the analogous molecules: Br(2)F(n), ClBrF(n), and BrF(n)(+1) systems. The first F-atom dissociation energies for the neutral global minima are 60 (HBrF(2)) and 49 kcal/mol (HBrF(4)) with the B3LYP method. The first H-atom dissociation energies for the same systems are 109 (HBrF(2)) and 116 kcal/mol (HBrF(4)). The large Br-H bond energies are not sufficient to render the hypervalent structures energetically tenable. The dissociation energies for the complexes to their fragments are relatively small. 相似文献