Co-reporter:Qiong Lei, Sai Ba, Hao Zhang, Yanyan Wei, Jasmine Yiqin Lee, Tianhu Li
Food Chemistry 2016 Volume 199() pp:364-371
Publication Date(Web):15 May 2016
DOI:10.1016/j.foodchem.2015.12.005
•Alternate winterization and interesterification enriched omega-3 PUFA efficiently.•The omega-3 PUFA content in cod liver oil was successfully doubled to 43.20 mol%.•Oil was winterized in acetone for 24 h at −80 °C before precooled vacuum filtration.•Optimum interesterification was with Lipozyme TL IM at 40 °C for 2.5 h in N2.•1H NMR analysis was efficient and authentic for omega-3 PUFA content determination.Enrichment of omega-3 fatty acids in cod liver oil via alternate operation of solvent winterization and enzymatic interesterification was attempted. Variables including separation method, solvent, oil concentration, time and temperature were optimized for the winterization. Meanwhile, Novozyme 435, Lipozyme RM IM and Lipozyme TL IM were screened for interesterification efficiency under different system air condition, time and temperature. In optimized method, alternate winterization (0.1 g/mL oil/acetone, 24 h, −80 °C, precooled Büchner filtration) and interesterification (Lipozyme TL IM, N2 flow, 2.5 h, 40 °C) successfully doubled the omega-3 fatty acid content to 43.20 mol%. 1H NMR was used to determine omega-3 fatty acid content, and GC–MS to characterize oil product, which mainly contained DHA (15.81 mol%) and EPA (20.23 mol%). The proposed method offers considerable efficiency and reduce production cost drastically. Oil produced thereof is with high quality and of particular importance for the development of omega-3 based active pharmaceutical ingredients.
Co-reporter:Sai Ba, Hao Zhang, Jasmine Yiqin Lee, Haixia Wu, Ruijuan Ye, Dejian Huang, Tianhu Li
Bioorganic & Medicinal Chemistry 2016 Volume 24(Issue 9) pp:1988-1992
Publication Date(Web):1 May 2016
DOI:10.1016/j.bmc.2016.03.025
Flap structure-specific endonuclease 1 (FEN1) is one of the enzymes that involve in Eukaryotic DNA replication and repair. Recent studies have proved that FEN1 is highly over-expressed in various types of cancer cells and is a drug target. However, a limited number of FEN1 inhibitors has been identified and approved. Herein, we investigate the catalytic activity of FEN1, and propose a substrate-based inhibitor. As a consequence, one of the phosphorothioate-modified substrates is proved to exhibit the most efficient inhibitory effect in our in vitro examinations. A novelly-designed substrate-based FEN1 inhibitor was accordingly constructed and determined a remarkable IC50 value.
Co-reporter:Sai Ba;Hao Zhang;Yiqin Jasmine Lee;Chee Wee Ng
European Journal of Lipid Science and Technology 2016 Volume 118( Issue 4) pp:651-657
Publication Date(Web):
DOI:10.1002/ejlt.201500120
Castor beans contain large quantities of oil and can grow in harsh environments. Unlike soybean oil, castor oil cannot be directly used for biodiesel production due to its extremely high viscosity. Here, we report an alternative source of biodiesel which possesses an ideal viscosity like soybean oil, and this new biodiesel could be obtained through simple synthetic routes from castor oil. Moreover, the properties of our newly designed ketone-containing triglycerides and its transesterified counterpart as biodiesel were systematically examined in our study, and their structures were characterized by using 1H NMR and 13C NMR.
Practical application: The product obtained has the potential to be utilized as an alternative biofuel.
Illustration of oxidation of castor oil and transesterification of oxidized castor oil to reduce viscosity.
Co-reporter:Dawei Li, Bei Lv, Hao Zhang, Jasmine Yiqin Lee, Tianhu Li
Bioorganic & Medicinal Chemistry Letters 2015 Volume 25(Issue 8) pp:1709-1714
Publication Date(Web):15 April 2015
DOI:10.1016/j.bmcl.2015.02.070
Unlike chemical damages on DNA, physical alterations of B-form of DNA occur commonly in organisms that serve as signals for specified cellular events. Although the modes of action for repairing of chemically damaged DNA have been well studied nowadays, the repairing mechanisms for physically altered DNA structures have not yet been understood. Our current in vitro studies show that both breakdown of stable non-B DNA structures and resumption of canonical B-conformation of DNA can take place during the courses of isothermal helicase-dependent amplification (HDA). The pathway that makes the non-B DNA structures repairable is presumably the relieving of the accumulated torsional stress that was caused by the positive supercoiling. Our new findings suggest that living organisms might have evolved this distinct and economical pathway for repairing their physically altered DNA structures.It is demonstrated in our studies that positive supercoiling generated in HDA reaction can act as the driving force to disintegrate the cruciform and G-quadruplex structures.
Co-reporter:Qiong Lei
European Journal of Lipid Science and Technology 2015 Volume 117( Issue 5) pp:630-636
Publication Date(Web):
DOI:10.1002/ejlt.201400458
Abstract
Long-chain monounsaturated fatty acid ethyl esters (LMFAEE) and fatty alcohol acetates (LMFAA) are important functional compounds in industry, and new sources are needed. In this study, jojoba oil was interesterified with ethyl acetate (EA) for the combined production of LMFAEE and LMFAA. Lipozyme RM IM and Novozym 435 were employed as the biocatalyst and their efficiencies were compared. Aliquot removal and subsequent 1H NMR analysis were used to monitor reaction progress and determine the interesterification yield (IY, %). Optimization of this reaction was conducted for both lipases with respect to four experimental parameters: temperature, EA content, immobilized lipase load, and reaction time. The highest IY in the presence of Novozym 435 was 97%, which was achieved after 9 hours of reaction at 37°C with 75 wt% EA and 5.00 wt% lipase load at 300 rpm, whereas the IY was 76% in the case of Lipozyme RM IM. The interesterified product was purified by preparative TLC and characterized by 1H NMR, FT-IR and GC-MS, indicating the main components are ethyl cis-11-eicosenoate (44%), cis-11-eicosenyl acetate (25%) and cis-13-docosenyl acetate (22%). Novozym 435 exhibited excellent operational stability over 17 interesterification cycles with ca. 12% IY decrease.
Practical applications: Conversion of the rare LMF-acid/alcohol source from jojoba oil to LMFAEE and LMFAA was realized in a one step interesterification reaction. The obtained jojobyl LMFAEE and LMFAA, in mixture or purified form, can serve as functional ingredients in various upmarket products, such as functional lipids, fragrances, cosmetics, pharmaceuticals and lubricants. Cis-11-eicosenyl acetate and cis-13-docosenyl acetate are also important insect pheromones in biological study. Additionally, the lipase reuse can help reduce cost significantly, making jojoba oil more economically attractive for industrial application.
Jojoba oil was converted to long-chain monounsaturated fatty acid ethyl ester (LMFAEE) and fatty alcohol acetate (LMFAA) via enzymatic interesterification with ethyl acetate. The resulting jojobyl LMFAEE and LMFAA have great potential for various upmarket applications in both industry and academia (e.g., fragrance, cosmetic, pharmaceutical and insect pheromone).
Co-reporter:Dawei Li, Bei Lv, Hao Zhang, Jasmine Yiqin Lee and Tianhu Li
Chemical Communications 2014 vol. 50(Issue 73) pp:10641-10644
Publication Date(Web):30 Jul 2014
DOI:10.1039/C4CC04789C
It is demonstrated that positive supercoiling affiliated with nucleosome formation can act as the driving force to repair the G-quadruplex, cruciform as well as a stable non-B DNA structure caused by peptide nucleic acid.
Co-reporter:Bei Lv, Dawei Li, Hao Zhang, Jasmine Yiqin Lee and Tianhu Li
Chemical Communications 2013 vol. 49(Issue 75) pp:8317-8319
Publication Date(Web):09 Jul 2013
DOI:10.1039/C3CC44675A
It is demonstrated that the prokaryote-exclusively-owned DNA gyrase is capable of facilitating the generation of a G-quadruplex from a long perfectly matched duplex DNA at physiological concentrations of cations.
Co-reporter:Qiong Lei;Wilson Liangwei Lee
European Journal of Lipid Science and Technology 2013 Volume 115( Issue 2) pp:232-238
Publication Date(Web):
DOI:10.1002/ejlt.201200174
Abstract
The increasing number of health issues caused by obesity and lack of healthy and efficient fat substitutes require development on new fat substitute. This study proposes a new potential reduced-calorie structured triacylglycerol (TAG) of “1,3-medium-chain, 2-short-chain triglycerides (MSM)” configuration, and the fat substitution method is based on the suppression of 2-monoacylglycerol absorption into intestinal cells, which would decrease the recombination of TAG and reduce lipid absorption in the digestive tract. A molecular probe, 1,3-dicapryloyl-2-acetylglycerol, is offered for nutritionists to conduct further study on its metabolism in human body. The synthesis method for this structured TAG starts from the lipase-catalyzed esterification between glycerol and caprylic acid, yielding 1,3-dicapryloylglycerol, and is followed by direct esterification with acetic anhydride to form 1,3-dicapryloyl-2-acetylglycerol. Its structure is characterized by FTIR,1H NMR,13C NMR, and LC-ESI-MS.
Practical application: This kind of pure structured triglyceride can function as a molecular probe for nutritionists to test its metabolism in human body and conduct further evaluation on their fat substitute potential. The synthesis method can also be easily adopted by food industry since it involves only two simple reaction steps.
Co-reporter:Hao Zhang, Juanjuan Guo, Dawei Li, Magdeline Tao Tao Ng, Jasmine Yiqin Lee, Bei Lv, Chee Wee Ng, Selvi Lee, Fangwei Shao, Tianhu Li
Bioorganic & Medicinal Chemistry Letters 2013 Volume 23(Issue 16) pp:4622-4626
Publication Date(Web):15 August 2013
DOI:10.1016/j.bmcl.2013.06.021
It was demonstrated in our studies that norfloxacin, a representative member of quinolone antibiotics, can indeed stabilize the gyrase–DNA complex formed during enzymatic cycle. In addition, the formation of the drug-induced complex has been firstly visualized through our atomic force microscopic examination.
Co-reporter:Hong Kee Tan, Dawei Li, Robert Kenneth Gray, Zhaoqi Yang, Magdeline Tao Tao Ng, Hao Zhang, Joel Ming Rui Tan, Shu Hui Hiew, Jasmine Yiqin Lee and Tianhu Li
Organic & Biomolecular Chemistry 2012 vol. 10(Issue 11) pp:2227-2230
Publication Date(Web):12 Jan 2012
DOI:10.1039/C2OB06811G
It has been demonstrated in our studies that the intrinsic curvature of DNA can be easily interrupted by low concentrations of chloroquine and ethidium bromide. In addition, the changes of DNA curvature caused by varying the concentration of these two DNA intercalators can be readily verified through using an atomic force microscope.
Co-reporter:Zhaoqi Yang, Dawei Li, Juanjuan Guo, Fangwei Shao, Tianhu Li
Bioorganic & Medicinal Chemistry Letters 2012 Volume 22(Issue 3) pp:1322-1325
Publication Date(Web):1 February 2012
DOI:10.1016/j.bmcl.2011.12.089
Human Topoisomerase I (hTopo I) have been known as a potential target for cancer therapy. A series of duplex DNA with different intrinsic curvatures have been designed as inhibitors to hTopo I. The activities of hTopo I on relaxing supercoiled plasmid pUC 19 are apparently diminished in the presence of the curved DNA. More potent inhibitions and smaller IC50 are achieved by duplex DNA with higher curvatures. EMSA indicates that hTopo I can recognize the curved DNA through binding interactions. Our studies demonstrate that the activity of hTopo I can be modulated by the intrinsic curvature of linear DNA and provide a new avenue to design curved DNA as hTopo I inhibitors with high therapeutic efficiency and low toxicity.Our studies demonstrate that the activity of hTopo I can be modulated by the intrinsic curvature of linear DNA and provide a new avenue to design curved DNA as hTopo I inhibitors with high therapeutic efficiency and low toxicity.
Co-reporter:Dawei Li, Zhaoqi Yang, Bei Lv, Tianhu Li
Bioorganic & Medicinal Chemistry Letters 2012 Volume 22(Issue 2) pp:833-836
Publication Date(Web):15 January 2012
DOI:10.1016/j.bmcl.2011.12.047
It is demonstrated in our studies that intrinsic curvatures of organismal DNAs could lead to the generation of duplex backbone self-crossings in their relaxed forms. In addition, the backbone self-crossings of the organismal DNAs could be readily confirmed through atomic force microscopic examination.It is demonstrated in our studies that intrinsic curvatures of organismal DNAs could lead to the generation of duplex backbone self-crossings in their relaxed forms. In addition, the backbone self-crossings of the organismal DNAs could be readily confirmed through atomic force microscopic examination.
Co-reporter:Dawei Li, Zhaoqi Yang, Yi Long, Guanjia Zhao, Bei Lv, Shuhui Hiew, Magdeline Tao Tao Ng, Juanjuan Guo, HongKee Tan, Hao Zhang, Weixing Yuan, Haibin Su and Tianhu Li
Chemical Communications 2011 vol. 47(Issue 38) pp:10695-10697
Publication Date(Web):05 Sep 2011
DOI:10.1039/C1CC13158C
It is demonstrated that the right and left handedness of DNA supercoils can be engineered precisely and readily at the molecular level in vitro through utilization of the invading property of peptide nucleic acid.
Co-reporter:Zhaoqi Yang, Dawei Li and Tianhu Li
Chemical Communications 2011 vol. 47(Issue 43) pp:11930-11932
Publication Date(Web):05 Oct 2011
DOI:10.1039/C1CC14957A
Strand proximity and self-crossing that occur intrinsically in the relaxed forms of toroidal DNA are utilized unprecedentedly in our investigations for creating catenated DNA rings. In addition, our current studies show that the geometrical shapes of our newly obtained catenated DNA circles as well as their topological arrangements are vividly visible under atomic force microscopic examination.
Co-reporter:Dawei Li, Zhaoqi Yang, Guanjia Zhao, Yi Long, Bei Lv, Cheng Li, Shuhui Hiew, Magdeline Tao Tao Ng, Juanjuan Guo, HongKee Tan, Hao Zhang and Tianhu Li
Chemical Communications 2011 vol. 47(Issue 26) pp:7479-7481
Publication Date(Web):20 Apr 2011
DOI:10.1039/C1CC11543J
It is demonstrated that the shapes and magnitudes of DNA writhe can be precisely manipulated solely through maneuvering the nucleotide sequence of DNA and without the assistance of topoisomerases.
Co-reporter:Zhaoqi Yang, Dawei Li, Shuhui Hiew, Magdeline Taotao Ng, Weixing Yuan, Haibin Su, Fangwei Shao and Tianhu Li
Chemical Communications 2011 vol. 47(Issue 40) pp:11309-11311
Publication Date(Web):16 Sep 2011
DOI:10.1039/C1CC13904E
A series of forcible curved circular DNAs (cDNAs) were prepared to investigate the recognition features of human Topoisomerase I (hTopo I). The IC50 can be modulated by the curvature degrees of cDNA. In addition, preferential bindings of hTopo I to cDNA with high curvature have been observed by AFM and EMSA.
Co-reporter:Tianyan Zhou, Xinming Li, Magdeline Tao Tao Ng, Yifan Wang, Ngee Mien Quek, Ji Luo, Weixing Yuan, Choon-Hong Tan, Huaqiang Zeng and Tianhu Li
Bioconjugate Chemistry 2009 Volume 20(Issue 4) pp:644
Publication Date(Web):March 30, 2009
DOI:10.1021/bc8004599
Synthesis of a fluorescein-tagged circular structure of i-motif was accomplished during our investigations. The backbone circularity of this molecular probe and the presence of the fluorescent moiety within its structure were also confirmed through exonuclease hydrolysis and fluorescence spectroscopy.
Co-reporter:Sock Teng Chua, Ngee Mien Quek, Ming Li, Magdeline Tao Tao Ng, Weixing Yuan, May Ling Chua, Juanjuan Guo, Li Eng Koh, Ruijuan Ye, Tianhu Li
Bioorganic & Medicinal Chemistry Letters 2009 Volume 19(Issue 3) pp:618-623
Publication Date(Web):1 February 2009
DOI:10.1016/j.bmcl.2008.12.061
A series of oligonucleotides with various lengths that contain nick and topoisomerase I-binding sites were designed. The interactions between these oligonucleotides and human topoisomerase I were investigated and the most efficient one among them has displayed IC50 value of 6.3 nM. Our studies have also demonstrated that the position of the nick as well as the length of the oligonucleotides were crucial factors for the inhibition of this nuclear enzyme.Here, we report oligonucleotides with various lengths that contain nick and topoisomerase I-binding sites as human topoisomerase I inhibitors.
Co-reporter:Hao Zhang, Tianhu Li
Bioorganic & Medicinal Chemistry Letters (15 January 2017) Volume 27(Issue 2) pp:
Publication Date(Web):15 January 2017
DOI:10.1016/j.bmcl.2016.11.088
It was shown in the past that in the presence of histone H1, plasmidic polynucleosomes formed densely packed aggregates. Our current studies demonstrate that these aggregates are susceptible to the actions of E. coli topoisomerase I, human topoisomerase I and DNA nicking enzyme, which is the indication that negative supercoiling is present in the condensed DNA-protein complexes. Since negative supercoiling leads to formation of highly curved and compact plectonemic and toroidal DNA structures, it would be reasonable to assume that DNA negative supercoils are responsible for aggregation of histone H1-plasmidic polynucleosome complexes.
Co-reporter:Hao Zhang, Tianhu Li
Bioorganic & Medicinal Chemistry Letters (1 March 2017) Volume 27(Issue 5) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.bmcl.2017.01.072
It is shown in our FRET studies that both chromatosomes and histone H1-depleted chromatosomes exist in their arm-closed forms in the absence of spermidine. In the presence of spermidine, however, these two types of structural assemblies are converted into their arm-open forms. In addition, ATP as polyanion is capable of suppressing the polycationic effect of spermidine, thus facilitating re-formation of arm-closed forms of these two types of structural assemblies. Our studies therefore illustrate that conversion between arm-closed and arm-open forms of chromatosomes and histone H1-depleted chromatosomes can be manipulated by varying concentrations of polycationic spermidine and polyanionic ATP.
Co-reporter:Vicky Ziman Zeng, Haibin Su and Tianhu Li
Organic & Biomolecular Chemistry 2016 - vol. 14(Issue 42) pp:NaN9965-9965
Publication Date(Web):2016/09/08
DOI:10.1039/C6OB01841F
By using polar DMF to relax the H-bonded rigid backbone and to lower the energetic penalty associated with the sterically-crowded environment, the yields for BOP-mediated one-pot synthesis of pentameric macrocycles can be improved from 10–25% as obtained in CH2Cl2 to 13–47% when 15% DMF in CH2Cl2 was used as the reaction medium.
Co-reporter:Zhaoqi Yang, Dawei Li, Shuhui Hiew, Magdeline Taotao Ng, Weixing Yuan, Haibin Su, Fangwei Shao and Tianhu Li
Chemical Communications 2011 - vol. 47(Issue 40) pp:NaN11311-11311
Publication Date(Web):2011/09/16
DOI:10.1039/C1CC13904E
A series of forcible curved circular DNAs (cDNAs) were prepared to investigate the recognition features of human Topoisomerase I (hTopo I). The IC50 can be modulated by the curvature degrees of cDNA. In addition, preferential bindings of hTopo I to cDNA with high curvature have been observed by AFM and EMSA.
Co-reporter:Bei Lv, Dawei Li, Hao Zhang, Jasmine Yiqin Lee and Tianhu Li
Chemical Communications 2013 - vol. 49(Issue 75) pp:NaN8319-8319
Publication Date(Web):2013/07/09
DOI:10.1039/C3CC44675A
It is demonstrated that the prokaryote-exclusively-owned DNA gyrase is capable of facilitating the generation of a G-quadruplex from a long perfectly matched duplex DNA at physiological concentrations of cations.
Co-reporter:Dawei Li, Zhaoqi Yang, Yi Long, Guanjia Zhao, Bei Lv, Shuhui Hiew, Magdeline Tao Tao Ng, Juanjuan Guo, HongKee Tan, Hao Zhang, Weixing Yuan, Haibin Su and Tianhu Li
Chemical Communications 2011 - vol. 47(Issue 38) pp:NaN10697-10697
Publication Date(Web):2011/09/05
DOI:10.1039/C1CC13158C
It is demonstrated that the right and left handedness of DNA supercoils can be engineered precisely and readily at the molecular level in vitro through utilization of the invading property of peptide nucleic acid.
Co-reporter:Dawei Li, Bei Lv, Hao Zhang, Jasmine Yiqin Lee and Tianhu Li
Chemical Communications 2014 - vol. 50(Issue 73) pp:NaN10644-10644
Publication Date(Web):2014/07/30
DOI:10.1039/C4CC04789C
It is demonstrated that positive supercoiling affiliated with nucleosome formation can act as the driving force to repair the G-quadruplex, cruciform as well as a stable non-B DNA structure caused by peptide nucleic acid.
Co-reporter:Dawei Li, Zhaoqi Yang, Guanjia Zhao, Yi Long, Bei Lv, Cheng Li, Shuhui Hiew, Magdeline Tao Tao Ng, Juanjuan Guo, HongKee Tan, Hao Zhang and Tianhu Li
Chemical Communications 2011 - vol. 47(Issue 26) pp:NaN7481-7481
Publication Date(Web):2011/04/20
DOI:10.1039/C1CC11543J
It is demonstrated that the shapes and magnitudes of DNA writhe can be precisely manipulated solely through maneuvering the nucleotide sequence of DNA and without the assistance of topoisomerases.
Co-reporter:Zhaoqi Yang, Dawei Li and Tianhu Li
Chemical Communications 2011 - vol. 47(Issue 43) pp:NaN11932-11932
Publication Date(Web):2011/10/05
DOI:10.1039/C1CC14957A
Strand proximity and self-crossing that occur intrinsically in the relaxed forms of toroidal DNA are utilized unprecedentedly in our investigations for creating catenated DNA rings. In addition, our current studies show that the geometrical shapes of our newly obtained catenated DNA circles as well as their topological arrangements are vividly visible under atomic force microscopic examination.
Co-reporter:Hong Kee Tan, Dawei Li, Robert Kenneth Gray, Zhaoqi Yang, Magdeline Tao Tao Ng, Hao Zhang, Joel Ming Rui Tan, Shu Hui Hiew, Jasmine Yiqin Lee and Tianhu Li
Organic & Biomolecular Chemistry 2012 - vol. 10(Issue 11) pp:NaN2230-2230
Publication Date(Web):2012/01/12
DOI:10.1039/C2OB06811G
It has been demonstrated in our studies that the intrinsic curvature of DNA can be easily interrupted by low concentrations of chloroquine and ethidium bromide. In addition, the changes of DNA curvature caused by varying the concentration of these two DNA intercalators can be readily verified through using an atomic force microscope.
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![(2-ISOPROPYL-3-INDOLIZINYL)(4-{3-[(2-METHYL-2-PROPANYL)AMINO]PROP<WBR />OXY}PHENYL)METHANONE](http://img.cochemist.com/ccimg/3600/3546-21-2_b.png)
