Biosynthesis of Indole Diterpene Lolitrems: Radical‐Induced Cyclization of an Epoxyalcohol Affording a Characteristic Lolitremane Skeleton

Lolitrems are tremorgenic indole diterpenes that exhibit a unique 5/6 bicyclic system of the indole moiety. Although genetic analysis has indicated that the prenyltransferase LtmE and the cytochrome P450 LtmJ are involved in the construction of this unique structure, the detailed mechanism remains to be elucidated. Herein, we report the reconstitution of the biosynthetic pathway for lolitrems employing a recently established genome‐editing technique for the expression host Aspergillus oryzae. Heterologous expression and bioconversion of the various intermediates revealed that LtmJ catalyzes multistep oxidation to furnish the lolitrem core. We also isolated the key reaction intermediate with an epoxyalcohol moiety. This observation allowed us to establish the mechanism of radical‐induced cyclization, which was firmly supported by density functional theory calculations and a model experiment with a synthetic analogue.     

Synthesis and characterization of highly random copolymer of ϵ-caprolactone and D,L-lactide using rare earth catalyst

Highly random copolymers of ϵ-caprolactone (CL) and D ,L -lactide (LA) were synthesized by a new catalyst system, rare earth chloride–propylene oxide (PO) system. In the presence of propylene oxide, all rare earth chlorides tested are highly effective for the copolymerization. The influences of reaction conditions on the copolymerization catalyzed by the NdCl₃-5PO system have been investigated in detail. The reactivity ratios of ϵ-caprolactone and D ,L -lactide were determined and show that the copolymerization with this new rare earth catalyst is closer to ideal copolymerization than reported for other catalysts. The microstructure of copolymer analyzed by ¹³C-NMR shows that the monomer units in the copolymer is near to completely random distribution with a short average monomer sequence length. The DSC measurement confirms the high randomness of the chain structure. The mechanism studied by NMR indicates that the rare earth alkoxide generated by the reaction of rare earth chloride with propylene oxide initiates the copolymerization, and then proceeds via a “coordination-insertion” mechanism with acyl-oxygen bond cleavage of CL and LA. © 1996 John Wiley & Sons, Inc.     

Energy conditions of the f(T,B) gravity dark energy model with the validity of thermodynamics

In this article, the analysis of Tsallis holographic dark energy(which turns into holographic dark energy for a particular choice of positive non-additivity parameter δ) in modified f(T, B) gravity with the validity of thermodynamics and energy conditions for a homogeneous and isotropic FLRW Universe has been studied. The enlightenment of the field equation towards f(T,B)=αT~m+βB~n, made possible by the fact that the model is purely accelerating,corresponds to q=-0.54(Mamon and Das 2017 Eur. Phys.J.C 77 49). The generalized second law of thermodynamics is valid not only for the same temperature inside the horizon, but also for the apparent horizon for a change in temperature. The essential inspiration driving this article is to exhibit the applicability that the holographic dark energy achieved from standard Tsallis holographic dark energy and the components acquired from f(T, B) gravity are identical for the specific bounty of constants. The analysis of energy conditions confirms that the weak energy condition and the null energy condition are fulfilled throughout the expansion, while violation of the strong energy condition validates the accelerated expansion of the Universe.With the expansion, the model becomes a quintessence dominated model. The dominant energy condition is not observed initially when the model is filled with genuine baryonic matter,whereas it appears when the model is in the quintessence dominated era.     

土壤中烃类污染物的超临界流体萃取

采用超临界流体萃取技术提取环境样品中的烃类污染物，以色谱－质谱联用仪测定了萃取物的化学成分，考察了影响萃取效率的主要因素。比传统的索氏萃取能更有效地从复杂环境样品中萃取分析物。     

气液色谱法测定双-(4,6-二异丙基水杨酸)合铜(Ⅱ)与脂肪胺和醇加合反应的热力学性质

用气液色谱法,在不同的温度下,测定了以α-甲基萘作为固定液时,路易斯碱脂肪胺和醇的溶解平衡常数K_R~0,以及它们与作为路易斯酸的过渡金属配合物双-(4,6-二异丙基水杨酸)合铜(Ⅱ)相互作用的表观分配常数K_R和加合反应的平衡常数K_1。再根据热力学公式: 进一步求出了加合反应的焓变ΔH和熵变ΔS。     

Studies on Cytochrome c Modified by [PtdienNO_3]Cl

For the first time, [PtdienNO_3]Cl was used as a stable reagent to modify ferricytochrome c and the reaction products were separated and purified with the CM-52 cation exchange chromatography. Five components were obtained, corresponding to the native cytochrome c single-labeled, dual-labeled, and triple-labeled derivatives as shown by the analysis of the molar ratio of the two metal atoms (Pt and Fe). The reduction potentials of these proteins were measured by differential pulse voltammetry. His-33 and Trp-59 were identified by~1HNMR as the binding sites of the platinum complex in the modified cytochrome c derivatives. Trp-59 was a conserved amino acid connected with the heme through hydrogen bond, which had not been modified by other transition metal complexes. The platinummodified cytochrome c derivatives might be valuable in exploring the role of the aromatic amino acids, especially Trp-59, in electron transfer.     

N－（2－环戊酮基丙酰基）－及N－（2－环己酮基丙酰基）－四氢噻唑－2－硫酮的合成及其醇解与胺解

以碘化－Ｎ－甲基－２－氯吡啶盐为缩合剂，在三乙胺存在下由３－（２－环戊酮基）丙酸及３－（２－环己酮基）丙酸分别同四氢噻唑－２－硫酮反应，得到新化合物Ｎ－（２－环戊酮基内酰基）四氢噻唑－２－硫酮（２ａ）及Ｎ－（２－环己酮基丙酰基）四氢噻唑－２－硫酮（２ｂ），产率分别为５２．９％和５１．０％，２ａ，ｂ分别同甲醇、乙醇反应得到相应的３－（２－环戊酮基）丙酸酯３ａ，ｂ及３－（２－环己酮基）丙酸酯３ｃ，ｄ，３ａ～ｄ的产率为７５～８７％；２ａ、ｂ分别同胺反应得到３－（２－环戊酮基）内酰胺４ａ、ｂ及３－（２－环己酮基）内酰胺４ｃ、ｄ，４ａ～ｄ产率为７８～９３％。