Sustainable and resilient e-commerce under COVID-19 pandemic: a hybrid grey decision-making approach.

E-commerce saw a paradigm shift during COVID. Consumers turned to online shopping when pandemic lockdowns caused brick-and-mortar stores to shut for extended periods. Although the pandemic drove more buyers online, it had negative impacts that affected e-commerce performance. This study assesses both positive and negative impacts and their relative significance. The findings are then used to prioritize different strategies for e-commerce development in four vibrant Middle Eastern economies: United Arab Emirates, Saudi Arabia, Qatar, and Kuwait. The study employs a hybrid approach incorporating grey analytical hierarchy process (GAHP) and grey relational analysis (GRA). The GAHP evaluates the relative significance of impacts, whereas the GRA ranks the strategies. The study is based on the responses from 36 local e-commerce specialists. The findings revealed that the supply chain disruption was a rather significant factor, and that "expanding supplier base" was a top-ranked strategy. The study suggests that increasing market share of e-commerce will necessitate the improvement of the supply chains, including the expansion of the supply base, as well as the establishment of sustainable supply chains. In addition to that, the moment has come to implement meaningful changes, such as digital transformation of supply chains, in order to fulfil customer expectations.

Efficient synthesis of Ala-Tyr by L-amino acid ligase coupled with ATP regeneration system.

The multi-enzyme coupling reaction system has become a promising biomanufacturing platform for biochemical production. Tyr is an essential amino acid, but the limited solubility restricts its use. Tyrosyl dipeptide has been paid more attention due to its higher solubility. In this study, an efficient enzymatic cascade of Ala-Tyr synthesis was developed by a L-amino acid ligase together with polyphosphate kinase (PPK). Two L-amino acid ligases from Bacillus subtilis and Bacillus pumilus were selected and applied for Ala-Tyr synthesis. The L-amino acid ligase from B. subtilis (Bs) was selected and coupled with the PPK from Sulfurovum lithotrophicum (PPKSL) for regenerating ATP to produce Ala-Tyr in one pot. In the optimization system, 40.1 mM Ala-Tyr was produced within 3 h due to efficient ATP regeneration with hexametaphosphate (PolyP(6)) as the phosphate donor. The molar yield was 0.89 mol/mol based on the substrates added, while the productivity of Ala-Tyr achieved 13.4 mM/h, which were the highest yield and productivity ever reported about Ala-Tyr synthesis with L-amino acid ligase.

Site-Directed Mutation of Salicylate Decarboxylase Gene and Mechanism of Ginkgo Acid Decarboxylation.

Ginkgo seed is an important Chinese medicine and food resource in China, but the toxicity of ginkgo acid in it limits its application. Previous studies have found that salicylic acid decarboxylase (Sdc) has a decarboxylation degradation effect on ginkgo acid. In order to improve the decarboxylation ability of Sdc to Ginkgo acid, 11 residues of the Sdc around the substrate (salicylic acid) were determined as mutation targets according to the analysis of crystal structure of Sdc (PDB ID:6JQX), from Trichosporon moniliiforme WU-0401, and a total of 30 single point mutant enzymes and one compound mutant enzyme were obtained. With Ginkgo acid C15:1 as the substrate, it was found from activity assay that Sdc-Y64T and Sdc-P191A had higher decarboxylation activity, which increased by 105.18% and 116.74% compared with that of wild type Sdc, respectively. The optimal pH for Sdc Y64T and Sdc-P191A to decarboxylate Ginkgo acid C15:1 was 5.5, which is the same as the wild type Sdc. The optimal temperature of Sdc-P191A was 50 °C, which was consistent with that of the wild type Sdc, but the optimal temperature of the mutant Sdc-Y64T was 40 °C, which was 10 °C lower than that of wild type Sdc.

Supplementary data for the quantum chemical calculation of free radical substitution reaction mechanism of camptothecin.

This data article contains the truncated view of the transition states for methyl radical attacking camptothecin at the site of 9, 10, 11, 12 and 14 in acidic conditions obtained from quantum computation of Gaussian 09 with B3LYP/6-31+G(d,p) level, also the truncated view of transition states for H abstraction by singlet O2 from sites of 9, 10, 11 and 12 of the intermediates of methyl combination with camptothecin and that by triplet O2 from site 9 of the intermediate of methyl combination with camptothecin in acidic condition are included. The corresponding parameters of reaction rate constant calculation for the formation of methyl radical from acetaldehyde, the first and second step of radical substitution of camptothecin under acidic conditions are listed. The data of the basic parameters for the computation of the total energy of the spin-projection of singlet oxygen, and the S2 values for the reactants, transition states and intermediates in the free radical substitution reaction of camptothecin are also included.

Characterization of UDP-Glycosyltransferase Involved in Biosynthesis of Ginsenosides Rg1 and Rb1 and Identification of Critical Conserved Amino Acid Residues for Its Function.

Ginsenosides attract great attention for their bioactivities. However, their contents are low, and many UDP-glycosyltransferases (UGTs) that play crucial roles in the ginsenoside biosynthesis pathways have not been identified, which hinders the biosynthesis of ginsenosides. In this study, we reported that one UDP-glycosyltransferase, UGTPg71A29, from Panax ginseng could glycosylate C20-OH of Rh1 and transfer a glucose moiety to Rd, producing ginsenosides Rg1 and Rb1, respectively. Ectopic expression of UGTPg71A29 in Saccharomyces cerevisiae stably generated Rg1 and Rb1 under its corresponding substrate. Overexpression of UGTPg71A29 in transgenic cells of P. ginseng could significantly enhance the accumulation of Rg1 and Rb1, with their contents of 3.2- and 3.5-fold higher than those in the control, respectively. Homology modeling, molecular dynamics, and mutational analysis revealed the key catalytic site, Gln283, which provided insights into the catalytic mechanism of UGTPg71A29. These results not only provide an efficient enzymatic tool for the synthesis of glycosides but also help achieve large-scale industrial production of glycosides.

Quantum chemical calculation of free radical substitution reaction mechanism of camptothecin.

Free radical substitution reaction, which has low energy barrier and takes place in mild reaction conditions, is an important method for camptothecin's modification. The experimental data show that the free radical substitution reaction of camptothecin has high site selectivity, and prefers to take place at site 7. Up to now, few researches focus on the mechanism of it. In this study, the differences of the reaction rate constant (k) for the reactions at different sites, such as site of 7, 9, 10, 11, 12, were investigated with B3LYP of density functional theory at the 6-31 + G (d, p) base set level and CPCM aqueous solvent model. It was found that the substitution reaction can be carried out in two steps in acidic condition. First, the methyl radical attacks the corresponding site to form an intermediate having methyl radical combined with the camptothecin skeleton, and then a hydrogen atom was abstracted by the singlet oxygen to form methyl camptothecin, wherein the first step was the rate control step of the reaction. The results show that site 7 has the higherreaction rate constant (k) than other examined sites, indicating that the reaction tends to take place on site 7 position, which is in agreement with the experimental results.

The catalytic activity for ginkgolic acid biodegradation, homology modeling and molecular dynamic simulation of salicylic acid decarboxylase.

The toxic ginkgolic acids are the main safety concern for the application of Ginkgo biloba. In this study, the degradation ability of salicylic acid decarboxylase (SDC) for ginkgolic acids was examined using ginkgolic acid C15:1 as a substrate. The results indicated that the content of ginkgolic acid C15:1 in Ginkgo biloba seeds was significantly decreased after 5 h treatment with SDC at 40 °Cand pH 5.5. In order to explore the structure of SDC and the interaction between SDC and substrates, homology modeling, molecular docking and molecular dynamics were performed. The results showed that SDC might also have a catalytic active center containing a Zn2+. Compared with the template structure of 2,6-dihydroxybenzoate decarboxylase, the residues surrounding the binding pocket, His10, Phe23 and Phe290, were replaced by Ala10, Tyr27 and Tyr301 in the homology constructed structure of SDC, respectively. These differences may significantly affect the substrates adaptability of SDC for salicylic acid derivatives.

Synthesis and aromatase inhibitory evaluation of 4-N-nitrophenyl substituted amino-4H-1,2,4-triazole derivatives.

In this paper, 13 4-N-nitrophenyl substituted amino-4H-1,2,4-triazole derivatives were synthesized and their aromatase inhibitory activities were measured. The results show that the substitution of the groups on benzyl group can further improve their bioactivity and the compound with Cl on the para position of benzyl has the highest bioactivity (IC50=9.02nM). A QSAR model was constructed from the 13 compounds with genetic function approximation using DS 2.1 package. This model can explain 90.09% of the variance (R(2)Adj), while it can predict 84.95% of the variance (R(2)cv) with the confidence interval of 95%.

DFT investigation on the decarboxylation mechanism of ortho hydroxy benzoic acids with acid catalysis.

A density functional theory (DFT) study was performed to explore the mechanisms of the acid-catalyzed decarboxylation reaction of salicylic acids using the B3LYP method with 6-31++G(d,p) basis set in both gas phase and aqueous environment. The α-protonated cation of carboxylate acid was formed during the decarboxylation process in acidic conditions, and the presence of hydrogen ions promotes decarboxylation greatly by significantly decreasing the overall reaction energy barriers to 20.98 kcal mol(-1) in gas phase and 20.93 kcal mol(-1) in water, respectively. The hydrogen in the α-carbon came directly from the acid rather than from the carboxyl group in neutral state. Compared with the reaction in gas phase, water in aqueous state causes the reaction to occur more easily. Substituents of methyl group, chlorine and fluorine at the ortho-position to the carboxyl of salicylic acid could further lower the decarboxylation energy barriers and facilitate the reaction.