92 research outputs found
Geh Cheow Lin Terima Anugerah Warna Ungu Universiti
No full textPULAU PINANG, 15 Mei 2018 – Atlet sukan Perahu Layar, Geh Cheow Lin dinobatkan sebagai penerima
Anugerah Ungu Universiti di Majlis Anugerah Sukan ke-40 Universiti Sains Malaysia (USM) kelmarin.
Cheow Lin menerima anugerah tertinggi tersebut kerana telah menunjukkan pencapaian yang
cemerlang di peringkat kebangsaan dan antarabangsa termasuk di Sukan SEA Kuala Lumpur 2017
Asymmetric ligand transformation reactions promoted by cyclometallated complexes
No full textComplex bis(u-chloro)-bis{(R)-1-(dimethylamino)ethyl] naphtyl-C2,N} palladium (II) was found to successfully undergo insertion reactions at the palladium-carbon with the diphenylarsinoprop-1-yne ligand at room temperature which leads to the formation of a new 7-membered metallacyce in the inserted product. This reaction was also carried out on the platinum (II) metal template containing the naphythylamine moiety. The monoarsine precursor complexes has shown to undergo a C-H bond activation followed by a C-C bond coupling at room temperature. This reaction can only be initiated with the presence of a platinum (II) metal. The chiral organopalladium template was used to promote asymmetric hydroarsination reaction between diphenylarsine and various functionalised alkenyl phosphines with hydroxy, methoxy, dimethylamino, ester and ketone as functional groups. The asymmetric Diels-Alder reaction promoted by chiral platinum (II) metal template between DMPP and phenyldi[(Z)]prop-1-enyl]phosphine oxide showed poor stereoselectivity with two isomers (1:1) being formed. The cycloaddition reaction between DMPP and phenyldi[(Z)]prop-1-enyl]phosphine sulphide similarly showed poor selectivity.DOCTOR OF PHILOSOPHY (SPMS
Chemical Constituents and Biological Activities From Garcinia Maingayi and Garcinia Parvifolia
No full textIn this present study, the stem bark of Garcinia maingayi and Garcinia parvifolia were
investigated and resulted in the isolation of nine compounds. There are no previous
reports on chemical components and biological activities from Garcinia maingayi. The
structures of these compounds were elucidated by using spectroscopic experiments
namely NMR, MS, IR and UV.
Being the first report on Garcinia maingayi, detailed chemical studies have afforded
two triterpenoids, stigmasterol and sitosterol, two xanthones, 1,3,7-trihydroxy-2-(3-
methylbut-2-enyl)-xanthone and 1,3,6,8-tetrahydroxyxanthone, one benzophenone,
isoxanthochymol, and one benzoic acid derivative methyl 3,4-dihydroxybenzoate. The
findings are significant as it contributes to the knowledge of the chemotaxonomy on
Garcinia species and all these compounds are new to the species.
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Meanwhile investigations on Garcinia parvifolia have afforded one triterpenoid, α-
amyrin and two xanthones, cowanin and rubraxanthone. Acetylation reaction was
carried out on rubraxanthone to yield triacetate rubraxanthone.
This is also the first report on cytotoxic and larvicidal activities of Garcinia maingayi,
Garcinia parvifolia and rubraxanthone. Cytotoxic tests were performed using HL-60
and CEM-SS cell lines. The crude hexane and chloroform extracts of Garcinia
maingayi were active against HL-60 cell line with IC50 values of less than 30 μg/ml. The
crude hexane and acetone extracts of Garcinia parvifolia were found to be active
against CEM-SS cell line with IC50 values of less than 30 μg/ml meanwhile, the crude
chloroform extract gave a significant activity with an IC50 value of 6.5 μg/ml.
The antimicrobial assay was carried out against four pathogenic bacteria, Methicillin
resistant Staphylococcus aures, Pseudomonas aeruginosa, Staphylococcus typhimurium
and Bacillus subtilis. Most of the crude extracts tested against these microbes gave only
moderate or weak activity. The antifungal activity testing of the plant extracts were
carried out against the fungi Candida albican, Aspergillus ochraceaus, Sacchoromyces
cerevisiae and Candida lypolytica. No activity was observed for all the crude extracts
The larvicidal test was carried out towards the larvae of Aedes aegypti. All the crude
extracts of Garcinia maingayi were weakly active against the larvae with LC50 values of
more than 150 μg/ml. The crude extracts of Garcinia parvifolia showed moderate
activities against the larvae by giving LC50 values of less than 100 μg/ml. The pure
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rubraxanthone showed a strong activity against the larvae with a LC50 value of 15.49
μg/ml
ATLET PERAHU LAYAR USM CEMERLANG DALAM SUKAN SEA
No full textPULAU PINANG, 19 Jun 2015 – Atlet sukan perahu layar dari Universiti Sains Malaysia (USM), Geh
Cheow Lin, 20, berjaya membuktikan kecemerlangannya membanggakan negara dengan meraih dua
pingat Perak dalam acara perahu layar pada Sukan SEA ke-28 di Pusat Pelayaran Kebangsaan
Singapura, baru-baru ini
USM ATHLETE EXCELS IN SEA GAMES SAILING EVENT
No full textPENANG, June 2015 – A Universiti Sains Malaysia (USM) athlete, Geh Cheow Lin, 20, has made the
country proud by winning two silver medals in the sailing event at the recently concluded 28 SEA
Games held at the Singapore National Sailing Centre
Secondary metabolites from two garcinia species and their biological activities.
No full textDetail chemical studies on Garcinia maingayi have yielded one xanthone, 1,3,7-trihydroxy-2-(3-methylbut-2-enyl)xanthone, one benzophenone, isoxanthochymol, one benzoic acid derivative 3,4-dihydroxy-methylbenzoate and two triterpenoids, stigmasterol and sitosterol. Meanwhile, investigations on Garcinia parvifolia have afforded one triterpenoid, α-amyrin and two xanthones, cowanin and rubraxanthone. Their structures were derived based on spectroscopic evidence, mainly 1D and 2D NMR spectroscopy. Acetylation reaction was carried out on rubraxanthone to yield triacetate rubraxanthone. It was found that the pure rubraxanthone was strongly active against the larvae of Aedes aegypti with LC50 value of 15.49 μg/mL and HL-60 cell line with an IC50 value of 7.5 μg/mL
Chemical constituents from Garcinia maingayi and Garcinia parvifolia (Guttiferae) and their biological activities
No full textDetail chemical studies on Garcinia maingayi have yielded one xanthone, 1,3,7-trihydroxy- 2-(3-methylbut-2-enyl)-xanthone, one benzophenone, isoxanthochymol, one benzoic acid derivative 3,4-dihydroxy-methylbenzoate and two triterpenoids, stigmasterol and sitosterol. Meanwhile, investigations on Garcinia parvifolia have afforded one triterpenoid, ?-amyrin and two xanthones, cowanin and rubraxanthone. Their structures were derived based on spectroscopic evidence, mainly ID and 2D NMR spectroscopy. Acetylation reaction was carried out on rubraxanthone to yield triacetate rubraxanthone. It was found that the pure rubraxanthone was strongly active against the larvae of Aedes aegypti with LC50 value of 15.49 μg/ ml and HL-60 cells line with an IC50 value of 7.5 μg/ ml
MOBILE SYSTEM WITH MOBILE STATION CONTROLLED HANDOFF FOR PACKETISED CDMA NETWORK DESIGN AND PERFORMANCE ANALYSIS
No full textMaster'sMASTER OF ENGINEERIN
Optical imaging detects metabolic signatures associated with oocyte and embryo quality
No full textNon-invasive assessment of both oocyte and embryo quality is a major focus of research to improve pregnancy and live birth rates following in vitro fertilisation (IVF). The developmental potential of the oocyte and embryo are intimately linked to metabolism. Thus, diagnostic approaches that measure oocyte and embryo metabolism may improve IVF outcomes. Metabolic heterogeneity is known to exist between cells of the cumulus oocyte complex (COC) and the embryo. However, current approaches may fail to accurately predict oocyte and embryo quality as they measure metabolism of the entire COC or embryo, and do not provide spatial information. Label-free optical imaging of NAD(P)H and FAD, provides an overall indicator of metabolism via the optical redox ratio (ORR; FAD / [NAD(P)H + FAD]). Optical imaging of these metabolic co-factors occurs in the complete absence of exogenous tags. In this thesis, I investigated whether label-free optical imaging of cellular autofluorescence could detect metabolic changes associated with oocyte and embryo quality. I confirmed the robustness of label-free optical imaging to measure dynamic metabolic changes in the COC by comparing the ORR with oxygen consumption rate –– the benchmark methodology for the field. Additionally, my work demonstrated the ability of hyperspectral microscopy, a label-free optical imaging modality, to detect metabolic signatures in oocytes with poor developmental potential. I utilised hyperspectral microscopy due to its low power density (energy) requirements for imaging and expected absence of photodamage. This makes this form of microscopy compatible with future clinical implementation. Following demonstration that label-free optical imaging detected metabolic changes associated with oocyte quality, I next investigated whether hyperspectral microscopy could quantify metabolic variance associated with poor embryo quality, specifically, aneuploidy. Current methods for assessing embryo aneuploidy are invasive and do not provide an accurate diagnosis for the presence or absence of aneuploid cells within foetal cell lineage: inner cell mass (ICM). My findings demonstrated that hyperspectral imaging detected significant metabolic differences between euploid and aneuploid cells. Importantly, mathematical algorithms applied to images acquired by hyperspectral microscopy, were able to discriminate between euploid and aneuploid ICM. I also assessed the safety of hyperspectral microscopy by comparing imaged and non-imaged embryos and showed that imaging did not impact embryo development, pregnancy rate or the weight of pups at weaning. Overall, my results demonstrate the potential for label-free optical imaging to be a safe and non-invasive diagnostic for embryo aneuploidy. As I had shown that label-free optical imaging of cellular autofluorescence could discriminate between euploid and aneuploid embryos, I next determined whether preservation of embryos impacted cellular autofluorescence, which could alter determination of ploidy status. Specifically, I investigated the impact of vitrification and fixation on autofluorescence as these techniques are commonly used in the clinic and for research purposes, respectively. My results showed that autofluorescence was impacted by vitrification and fixation. Therefore, caution is warranted when using preserved embryos to measure metabolic state and predict developmental potential. Collectively, these findings demonstrate that label-free optical imaging is a promising non-invasive approach to measure metabolism and predict the developmental potential of oocytes and embryos.Thesis (Ph.D.) -- University of Adelaide, School of Biomedicine, 202
Burkholderia paludis sp. nov., an antibiotic-siderophore producing novel Burkholderia cepacia complex species, isolated from malaysian tropical peat swamp soil
No full textA novel Gram negative rod-shaped bacterium, designated strain MSh1T, was isolated from Southeast Pahang tropical peat swamp forest soil in Malaysia and characterized using a polyphasic taxonomy approach. The predominant cellular fatty acids (> 10.0%) were C16:0 (31.7%), C17:0 cyclo (26.6%), and C19:0 cyclo ω8c (16.1%). The polar lipids detected were phosphatidylglycerol, phosphatidylethanolamine, and diphosphatidylglycerol. The predominant ubiquinone was Q-8. This revealed that strain MSh1T belongs to the genus Burkholderia. The type strain MSh1T can be differentiated from other Burkholderia cepacia complex (Bcc) species by phylogenetic analysis of 16S rRNA gene sequence, multilocus sequence analysis (MLSA), average nucleotide identity (ANI) and biochemical tests. DNA-DNA relatedness values between strain MSh1T and closely related type strains were below the 70% threshold value. Based on this polyphasic study of MSh1T, it can be concluded that this strain represents a novel species within the Bcc, for which the name Burkholderia paludis sp. nov. is proposed. The type strain is MSh1T (= DSM 100703T = MCCC 1K01245T). The dichloromethane extract of MSh1T exhibited antimicrobial activity against four Gram positive bacteria (Enterococcus faecalis ATCC 29212, E. faecalis ATCC 700802, Staphylococcus aureus ATCC 29213, S. aureus ATCC 700699) and a Gram negative bacteria (Escherichia coli ATCC 25922). Further purification work has led to the isolation of Compound 1, pyochelin. Pyochelin demonstrated antimicrobial activity against four S. aureus strains and three E. faecalis strains with MIC-values of 3.13 μg/ml and 6.26 μg/ml, respectively. SEM analysis showed that the cellular morphology of E. faecalis ATCC 700802 was not affected by pyochelin; suggesting that it might target the intracellular components. Pyochelin, a siderophore with antimicrobial activity might be useful in treating bacterial infections caused by S. aureus and E. faecalis, however further work has to be done. © 2016 Ong, Aw, Lee, Yule, Cheow and Lee
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