Wu Ji'en
Email Address
chmwujie@nus.edu.sg
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Publication Effect of vacuum impregnated fish gelatin and grape seed extract on metabolite profiles of tilapia (Oreochromis niloticus) fillets during storage(Elsevier BV, 2019-09-30) Zhao, X; Wu, J; Chen, L; Yang, H; Dr Yang Hongshun; CHEMISTRY© 2019 Elsevier Ltd Traditional methods evaluating fish quality do not involve comprehensive qualification and quantification of quality-related components. The objective of this study was to investigate the effect of vacuum impregnated fish gelatin (FG)and grape seed extract (GSE)on metabolites of tilapia fillets during storage using nuclear magnetic resonance (NMR). Totally 42 metabolites were identified, 36 of which were quantified. The multivariate analysis results demonstrated distinct separations between fresh and stored fillets, indicating significant metabolite changes during storage. Some metabolites like choline and trimethylamine oxide were closely related to freshness while organic acids were associated with spoilage. Combined FG and GSE reduced the formation of undesirable metabolites like trimethylamine and histidine significantly (P < 0.05). Traditional freshness indexes indicated preserved quality after combined coating and further verified NMR results. This study reveals the potential of NMR to analyse metabolites that determine fish quality and to monitor their changes during storage.Publication Structure-Dependent cis/trans Isomerization of Tetraphenylethene Derivatives: Consequences for Aggregation-Induced Emission(WILEY-V C H VERLAG GMBH, 2016-05-17) Zhang, Chong-Jing; Feng, Guangxue; Xu, Shidang; Zhu, Zhenshu; Lu, Xianmao; Wu, Jien; Liu, Bin; Prof Liu Bin; CHEMISTRY; CHEMICAL & BIOMOLECULAR ENGINEERING© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. The isomerization and optical properties of the cis and trans isomers of tetraphenylethene (TPE) derivatives with aggregation-induced emission (AIEgens) have been sparsely explored. We have now observed the tautomerization-induced isomerization of a hydroxy-substituted derivative, TPETH-OH, under acidic but not under basic conditions. Replacing the proton of the hydroxy group in TPETH-OH with an alkyl group leads to the formation of TPETH-MAL, for which the pure cis and trans isomers were obtained and characterized by HPLC analysis and NMR spectroscopy. Importantly, cis-TPETH-MAL emits yellow fluorescence in DMSO at -20 °C whereas trans-TPETH-MAL shows red fluorescence under the same conditions. Moreover, the geometry of cis- and trans-TPETH-MAL remains unchanged when they undergo thiol-ene reactions to form cis- and trans-TPETH-cRGD, respectively. Collectively, our findings improve our fundamental understanding of the cis/trans isomerization and photophysical properties of TPE derivatives, which will guide further AIEgen design for various applications. The cis and trans isomers of a tetraphenylethene derivative with aggregation-induced emission, TPETH-MAL, were characterized by HPLC analysis and NMR spectroscopy. cis-TPETH-MAL emits yellow fluorescence in DMSO at -20 °C whereas trans-TPETH-MAL shows red fluorescence under the same conditions.Publication Highly emissive, solution-processable and dynamic Eu(III)-containing coordination polymers(Royal Society of Chemistry, 2015) Duerrbeck, Andre; Gorelik, Sergey; Hobley, Jonathan; Wu, Ji'En; Hor Tzi Sum, Andy; Long, Nicholas; CHEMISTRYPublication Enantioselective desymmetrization of cyclohexadienones via an intramolecular Rauhut-Currier reaction of allenoates(Nature Publishing Group, 2016) Yao, W; Dou, X; Wen, S; Wu, J; Vittal, J.J; Lu, Y; CHEMISTRYThe Rauhut-Currier (RC) reaction represents an efficient method for the construction of carbon-carbon bond in organic synthesis. However, the RC reactions involving allenoate substrates are very rare, and in particular, asymmetric intramolecular RC reaction of allenoates is yet to be discovered. Here, we show that the intramolecular RC reaction proceeds smoothly in the presence of 1 mol% ?-ICD, and bicyclic lactones are obtained in high yields and with excellent enantiomeric excesses. With the employment of 3-substituted allenoates as racemic precursors, a novel dynamic kinetic resolution of allenes via RC reaction is observed, which allows for facile synthesis of highly enantiomerically enriched allenes. © The Author(s) 2016.Publication Light-Up Probe for Targeted and Activatable Photodynamic Therapy with Real-Time In Situ Reporting of Sensitizer Activation and Therapeutic Responses(Wiley-VCH Verlag, 2015-11-11) YUAN YOUYONG; Zhang Chongjing; Kwok, Ryan TK; XU SHIDANG; ZHANG RUOYU; WU JI'EN; Tang, Ben Zhong; LIU BIN; Prof Liu Bin; CHEMISTRY; CHEMICAL & BIOMOLECULAR ENGINEERINGIntegrated systems that offer traceable cancer therapy are highly desirable for personalized medicine. Herein, a probe is reported that is composed of a red-emissive photosensitizer (PS) with aggregation-induced emission characteristics and a built-in apoptosis sensor with activatable green emission for targeted cancer cell ablation and real-time monitoring of PS activation and therapeutic response. The probe is nonemissive in aqueous media and can be selectively uptaken by αvβ3 integrin overexpressed cancer cells. Cleavage of the probe by intracellular glutathione leads to release of the apoptosis sensor and red fluorescence turn-on to report the PS activation. Upon light irradiation, the PS can generate reactive oxygen species to induce cell apoptosis and activate caspase-3/-7, which will cleave the apoptosis sensor to yield intense green fluorescence. Both the red and green emission can be obtained through a single wavelength excitation, which makes the probe very convenient for therapeutic protocol development. A novel light-up probe is developed for targeted and activatable photodynamic therapy with real-time in situ reporting of sensitizer activation and therapeutic responses.Publication Identification of cyclic dipeptides from Escherichia coli as new antimicrobial agents against Ralstonia solanacearum(MDPI AG, 2018) Song, S.; Fu, S.; Sun, X.; Li, P.; Wu, J.; Dong, T.; He, F.; Deng, Y.; CHEMISTRYRalstonia solanacearum is a causative agent of bacterial wilt in many important crops throughout the world. How to control bacterial wilt caused by R. solanacearum is a major problem in agriculture. In this study, we aim to isolate the biocontrol agents that have high efficacy in the control of bacterial wilt. Three new bacterial strains with high antimicrobial activity against R. solanacearum GMI1000 were isolated and identified. Our results demonstrated that these bacteria could remarkably inhibit the disease index of host plant infected by R. solanacearum. It was indicated that strain GZ-34 (CCTCC No. M 2016353) showed an excellent protective effect to tomato under greenhouse conditions. Strain GZ-34 was characterized as Escherichia coli based on morphology, biochemistry, and 16S rRNA analysis. We identified that the main antimicrobial compounds produced by E. coli GZ-34 were cyclo(L-Pro-D-Ile) and cyclo(L-Pro-L-Phe) using electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) analysis. The two active compounds also interfered with the expression levels of some pathogenicity-contributors of R. solanacearum. Furthermore, cyclo(L-Pro-L-Phe) effectively inhibited spore formation of Magnaporthe grisea, which is a vital pathogenesis process of the fungal pathogen, suggesting cyclic dipeptides from E. coli are promising potential antimicrobial agents with broad-spectrum activity to kill pathogens or interfere with their pathogenesis. © 2018 by the authors.