Displaying publications 1 - 20 of 59 in total

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  1. Chai KL, Aung MM, Noor IM, Lim HN, Abdullah LC
    Sci Rep, 2022 Jan 07;12(1):124.
    PMID: 34997013 DOI: 10.1038/s41598-021-03965-7
    Jatropha oil-based polyurethane acylate gel polymer electrolyte was mixed with different concentrations of tetrabutylammonium iodide salt (TBAI). The temperature dependences of ionic conductivity, dielectric modulus and relaxation time were studied in the range of 298 to 393 K. The highest ionic conductivity of (1.88 ± 0.020) × 10-4 Scm-1 at 298 K was achieved when the gel contained 30 wt% of TBAI and 2.06 wt% of I2. Furthermore, the study found that conductivity-temperature dependence followed the Vogel-Tammann Fulcher equation. From that, it could be clearly observed that 30 wt% TBAI indicated the lowest activation energy of 6.947 kJ mol-1. By using the fitting method on the Nyquist plot, the number density, mobility and diffusion coefficient of the charge carrier were determined. The charge properties were analysed using the dielectric permittivity, modulus and dissipation factor. Apart from this, the stoke drag and capacitance were determined.
  2. Chan KF, Lim HN, Shams N, Jayabal S, Pandikumar A, Huang NM
    Mater Sci Eng C Mater Biol Appl, 2016 Jan 1;58:666-74.
    PMID: 26478358 DOI: 10.1016/j.msec.2015.09.010
    Immunosensors based on gold nanoparticles and reduced graphene oxide (AuNPs/rGO)-modified screen-printed electrodes (SPEs) were successfully synthesized using an electrochemical deposition method. The modified SPEs were characterized using a field emission scanning electron microscope (FESEM) and Raman spectroscopy to analyze the morphology and composition of AuNPs and rGO. Both the FESEM and Raman spectroscopy revealed that the AuNPs were successfully anchored on the thin film of rGO deposited on the surface of the SPEs. Characterization with a ferri-ferrocyanide couple [Fe(CN)6(3-/4-)] showed that the electron transfer kinetic between the analyte and electrode was enhanced after the modification with the AuNPs/rGO composite on the electrode surface, in addition to increasing the effective surface area of the electrode. The modified SPE was immobilized with a sandwich type immunosensor to mimic the ELISA (enzyme-linked immunosorbent assay) immunoassay. The modified SPE that was fortified with the sandwich type immunosensor exhibited double electrochemical responses in the detection of carcinoembryonic antigen (CEA), with linear ranges of 0.5-50 ng/mL and 250-2000 ng/mL and limits of detection of 0.28 ng/mL and 181.5 ng/mL, respectively.
  3. Chan SC, Chandramani T, Chen TY, Chong KN, Harbaksh S, Lee TW, et al.
    Med J Malaysia, 2005 Oct;60(4):475-82.
    PMID: 16570710
    An audit of hypertension management was done in October 2004 in nine general practice (GP) clinics. Two structure, ten process and two outcome indicators were assessed. Results showed that targets were achieved in only four indicators, i.e., weight recording (89%), BP monitoring (85.8%), follow-up interval not exceeding 6 months (87.9%) and mean diastolic BP (73.9%). The other indicators (hypertension registry, reminder mechanisms for defaulters, recording of smoking, height, fundoscopy, monitoring of lipid profile, blood sugar, ECG, renal function and achievement of target mean systolic pressure) showed adequacy percentages varying from 22.1 to 68.7. Out of the 1260 patients assessed, 743 (59%) achieved a mean BP < or = 140/90 (or < or = 130/80 mmHg with diabetes mellitus / renal insufficiency) in the last 3 recorded readings. There was a vast difference between individual clinics. Reasons for not achieving targets were discussed and remedial measures for implementation were recommended.
  4. Che' Man AB, Lim HH
    Singapore Med J, 1983 Jun;24(3):135-9.
    PMID: 6635675
    A study was carried out to determine ventilatory capacity (Forced Expiratory Volume or FEV1 and Forced Vital Capacity or FVC) in apparently normal Malay office workers in Malaysia. The subjects, 78 males and 113 females, were interviewed using a standardized questionnaire to exclude those with symptoms or past history of cardiopulmonary disease. Measurements of age, height, weight, FEV, and FVC were made on each subject; the FEV, and FVC were measured using Vitalograph spirometers. The mean FEV, and FVC for males were 3.35 litres and 3.76 Iitres, respectively. For females, the mean FEV, and FVC were 3.46 and 2.72 Iitres, respectively. Height was positively correlated with FEV, and FVC (p
  5. Chen LT, Martinelli E, Cheng AL, Pentheroudakis G, Qin S, Bhattacharyya GS, et al.
    Ann Oncol, 2020 03;31(3):334-351.
    PMID: 32067677 DOI: 10.1016/j.annonc.2019.12.001
    The most recent version of the European Society for Medical Oncology (ESMO) Clinical Practice Guidelines for the diagnosis, treatment and follow-up of hepatocellular carcinoma (HCC) was published in 2018, and covered the diagnosis, management, treatment and follow-up of early, intermediate and advanced disease. At the ESMO Asia Meeting in November 2018 it was decided by both the ESMO and the Taiwan Oncology Society (TOS) to convene a special guidelines meeting immediately after the Taiwan Joint Cancer Conference (TJCC) in May 2019 in Taipei. The aim was to adapt the ESMO 2018 guidelines to take into account both the ethnic and the geographic differences in practice associated with the treatment of HCC in Asian patients. These guidelines represent the consensus opinions reached by experts in the treatment of patients with intermediate and advanced/relapsed HCC representing the oncology societies of Taiwan (TOS), China (CSCO), India (ISMPO) Japan (JSMO), Korea (KSMO), Malaysia (MOS) and Singapore (SSO). The voting was based on scientific evidence, and was independent of the current treatment practices, the drug availability and reimbursement situations in the individual participating Asian countries.
  6. Chiam SL, Lim HN, Hafiz SM, Pandikumar A, Huang NM
    Sci Rep, 2018 Jul 12;8(1):10830.
    PMID: 29997395 DOI: 10.1038/s41598-018-28897-7
    A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
  7. Chiam SL, Lim HN, Hafiz SM, Pandikumar A, Huang NM
    Sci Rep, 2018 02 15;8(1):3093.
    PMID: 29449631 DOI: 10.1038/s41598-018-21572-x
    The energy density of conventional supercapacitors is in the range of 6-10 Wh kg-1, which has restricted them from many applications that require devices with long durations. Herein, we report a method for enhancing the energy density of a device through the parallel stacking of five copper foils coated on each side with graphene nanoplatelets. Microporous papers immersed in 2 M aqueous sodium sulphate were used as separators. With a low contact resistance of 0.05 Ω, the supercapacitor yielded an optimum specific energy density and a specific power density of 24.64 Wh kg-1 and 402 W kg-1 at 0.8 V, respectively. The working potential was increased to 2.4 V when three of the supercapacitors were connected in series, forming a tandem device. Its potential for real applications was manifested by the ability to light up a light-emitting diode for 40 s after charging for 60 s.
  8. Crous PW, Wingfield MJ, Chooi YH, Gilchrist CLM, Lacey E, Pitt JI, et al.
    Persoonia, 2020 Jun;44:301-459.
    PMID: 33116344 DOI: 10.3767/persoonia.2020.44.11
    Novel species of fungi described in this study include those from various countries as follows: Antarctica, Cladosporium arenosum from marine sediment sand. Argentina, Kosmimatamyces alatophylus (incl. Kosmimatamyces gen. nov.) from soil. Australia, Aspergillus banksianus, Aspergillus kumbius, Aspergillus luteorubrus, Aspergillus malvicolor and Aspergillus nanangensis from soil, Erysiphe medicaginis from leaves of Medicago polymorpha, Hymenotorrendiella communis on leaf litter of Eucalyptus bicostata, Lactifluus albopicri and Lactifluus austropiperatus on soil, Macalpinomyces collinsiae on Eriachne benthamii, Marasmius vagus on soil, Microdochium dawsoniorum from leaves of Sporobolus natalensis, Neopestalotiopsis nebuloides from leaves of Sporobolus elongatus, Pestalotiopsis etonensis from leaves of Sporobolus jacquemontii, Phytophthora personensis from soil associated with dying Grevillea mccutcheonii.Brazil, Aspergillus oxumiae from soil, Calvatia baixaverdensis on soil, Geastrum calycicoriaceum on leaf litter, Greeneria kielmeyerae on leaf spots of Kielmeyera coriacea. Chile, Phytophthora aysenensis on collar rot and stem of Aristotelia chilensis.Croatia, Mollisia gibbospora on fallen branch of Fagus sylvatica.Czech Republic, Neosetophoma hnaniceana from Buxus sempervirens.Ecuador, Exophiala frigidotolerans from soil. Estonia, Elaphomyces bucholtzii in soil. France, Venturia paralias from leaves of Euphorbia paralias.India, Cortinarius balteatoindicus and Cortinarius ulkhagarhiensis on leaf litter. Indonesia, Hymenotorrendiella indonesiana on Eucalyptus urophylla leaf litter. Italy, Penicillium taurinense from indoor chestnut mill. Malaysia, Hemileucoglossum kelabitense on soil, Satchmopsis pini on dead needles of Pinus tecunumanii.Poland, Lecanicillium praecognitum on insects' frass. Portugal, Neodevriesia aestuarina from saline water. Republic of Korea, Gongronella namwonensis from freshwater. Russia, Candida pellucida from Exomias pellucidus, Heterocephalacria septentrionalis as endophyte from Cladonia rangiferina, Vishniacozyma phoenicis from dates fruit, Volvariella paludosa from swamp. Slovenia, Mallocybe crassivelata on soil. South Africa, Beltraniella podocarpi, Hamatocanthoscypha podocarpi, Coleophoma podocarpi and Nothoseiridium podocarpi (incl. Nothoseiridium gen. nov.) from leaves of Podocarpus latifolius, Gyrothrix encephalarti from leaves of Encephalartos sp., Paraphyton cutaneum from skin of human patient, Phacidiella alsophilae from leaves of Alsophila capensis, and Satchmopsis metrosideri on leaf litter of Metrosideros excelsa.Spain, Cladophialophora cabanerensis from soil, Cortinarius paezii on soil, Cylindrium magnoliae from leaves of Magnolia grandiflora, Trichophoma cylindrospora (incl. Trichophoma gen. nov.) from plant debris, Tuber alcaracense in calcareus soil, Tuber buendiae in calcareus soil. Thailand, Annulohypoxylon spougei on corticated wood, Poaceascoma filiforme from leaves of unknown Poaceae.UK, Dendrostoma luteum on branch lesions of Castanea sativa, Ypsilina buttingtonensis from heartwood of Quercus sp. Ukraine, Myrmecridium phragmiticola from leaves of Phragmites australis.USA, Absidia pararepens from air, Juncomyces californiensis (incl. Juncomyces gen. nov.) from leaves of Juncus effusus, Montagnula cylindrospora from a human skin sample, Muriphila oklahomaensis (incl. Muriphila gen. nov.) on outside wall of alcohol distillery, Neofabraea eucalyptorum from leaves of Eucalyptus macrandra, Diabolocovidia claustri (incl. Diabolocovidia gen. nov.) from leaves of Serenoa repens, Paecilomyces penicilliformis from air, Pseudopezicula betulae from leaves of leaf spots of Populus tremuloides. Vietnam, Diaporthe durionigena on branches of Durio zibethinus and Roridomyces pseudoirritans on rotten wood. Morphological and culture characteristics are supported by DNA barcodes.
  9. Feng Z, Lim HN, Ibrahim I, Gowthaman NSK
    J Mater Chem B, 2023 Oct 06;11(38):9099-9127.
    PMID: 37650588 DOI: 10.1039/d3tb01221b
    Small biomolecules play a critical role in the fundamental processes that sustain life and are essential for the proper functioning of the human body. The detection of small biomolecules has garnered significant interest in various fields, including disease diagnosis and medicine. Electrochemical techniques are commonly employed in the detection of critical biomolecules through the principle of redox reactions. It is also a very convenient, cheap, simple, fast, and accurate measurement method in analytical chemistry. Zeolitic imidazolate frameworks (ZIFs) are a unique type of metal-organic framework (MOF) composed of porous crystals with extended three-dimensional structures. These frameworks are made up of metal ions and imidazolate linkers, which form a highly porous and stable structure. In addition to their many advantages in other applications, ZIFs have emerged as promising candidates for electrochemical sensors. Their large surface area, pore diameter, and stability make them ideal for use in sensing applications, particularly in the detection of small molecules and ions. This review summarizes the critical role of small biomolecules in the human body, the standard features of electrochemical analysis, and the utilization of various types of ZIF materials (including carbon composites, metal-based composites, ZIF polymer materials, and ZIF-derived materials) for the detection of important small biomolecules in human body fluids. Lastly, we provide an overview of the current status, challenges, and future outlook for research on ZIF materials.
  10. Foo CY, Lim HN, Pandikumar A, Huang NM, Ng YH
    J Hazard Mater, 2016 Mar 5;304:400-8.
    PMID: 26595899 DOI: 10.1016/j.jhazmat.2015.11.004
    A newly developed CdS/rGO/CC electrode was prepared based on a flexible carbon cloth (CC) substrate with cadmium sulfide (CdS) nanoparticles and reduced graphene oxide (rGO). The CdS was synthesized using an aerosol-assisted chemical vapor deposition (AACVD) method, and the graphene oxide was thermally reduced on the modified electrode surface. The existence of rGO in the CdS-modified electrode increased the photocurrent intensity of the CdS/rGO/CC-modified electrode by three orders of magnitude, compared to that of the CdS/ITO electrode and two orders of magnitude higher than the CdS/CC electrode. A new visible-light-prompt photoelectrochemical sensor was developed based on the competitive binding reaction of Cu(2+) and CdS on the electrode surface. The results showed that the effect of the Cu(2+) on the photocurrent response was concentration-dependent over the linear ranges of 0.1-1.0 μM and 1.0-40.0 μM with a detection limit of 0.05 μM. The results of a selectivity test showed that this modified electrode has a high response toward Cu(2+) compared to other heavy metal ions. The proposed CdS/rGO/CC electrode provided a significantly high potential current compared to other reported values, and could be a practical tool for the fast, sensitive, and selective determination of Cu(2+).
  11. Gowthaman NSK, Ngee Lim H, Balakumar V, Shankar S
    Ultrason Sonochem, 2020 Mar;61:104828.
    PMID: 31670250 DOI: 10.1016/j.ultsonch.2019.104828
    A novel organic-inorganic nile-blue - CeO2 (CeO2/NB) nanohybrid has been synthesized by environmentally benign ultrasonic irradiation method for the selective determination of the environmental pollutant, carcinogenic hydrazine (HZ) in environmental water samples. Hydrophobic dyes have generally been as redox mediators in electrochemical sensors fabrication due to strong electron transfer capacity and they would allow the oxidation and reduction of the analytes at lower potentials. The CeO2 nanoparticles were initially synthesized by the ultrasonic irradiation of Ce(NO3)2, NH4OH and ethylene glycol mixture for 6 h using probe sonicator (20 kHz, 100 W) followed by calcination. The organic-dye NB was then added and ultrasonicated further 30 min for the formation of CeO2/NB nanohybrid material. Various spectroscopic and microscopic tools such as UV-vis and FT-IR spectroscopy, XRD, SEM and high-solution TEM and surface analysis tool Brunauer-Emmett-Teller (BET) confirm the formation of the nanohybrid. HR-TEM images showed the well-covered CeO2 on NB molecules and the average size of the nanohybrid is ~35 nm. For the fabrication of environmental pollutant electrochemical sensor, the prepared CeO2/NB nanohybrid was drop-casted on the electrode surface and utilized for the determination of HZ. The nanohybrid modified electrode exhibits higher electrocatalytic activity by showing enhanced oxidation current and less positive potential shift towards HZ oxidation than the bare and individual CeO2 and NB modified electrodes. The fabricated sensor with excellent reproducibility, repeatability, long-term storage stability and cyclic stability exhibited the sensational sensitivity (484.86 µA mM-1 cm-2) and specificity in the presence of 50-fold possible interfering agents with the lowest limit of detection of 57 nM (S/N = 3) against HZ. Utilization of the present sensor in environmental samples with excellent recovery proves it practicability in the determination of HZ in real-time application.
  12. Huang NM, Lim HN, Chia CH, Yarmo MA, Muhamad MR
    Int J Nanomedicine, 2011;6:3443-8.
    PMID: 22267928 DOI: 10.2147/IJN.S26812
    Graphene has attracted much attention from researchers due to its interesting mechanical, electrochemical, and electronic properties. It has many potential applications such as polymer filler, sensor, energy conversion, and energy storage devices. Graphene-based nanocomposites are under an intense spotlight amongst researchers. A large amount of graphene is required for preparation of such samples. Lately, graphene-based materials have been the target for fundamental life science investigations. Despite graphene being a much sought-after raw material, the drawbacks in the preparation of graphene are that it is a challenge amongst researchers to produce this material in a scalable quantity and that there is a concern about its safety. Thus, a simple and efficient method for the preparation of graphene oxide (GO) is greatly desired to address these problems. In this work, one-pot chemical oxidation of graphite was carried out at room temperature for the preparation of large-area GO with ~100% conversion. This high-conversion preparation of large-area GO was achieved using a simplified Hummer's method from large graphite flakes (an average flake size of 500 μm). It was found that a high degree of oxidation of graphite could be realized by stirring graphite in a mixture of acids and potassium permanganate, resulting in GO with large lateral dimension and area, which could reach up to 120 μm and ~8000 μm(2), respectively. The simplified Hummer's method provides a facile approach for the preparation of large-area GO.
  13. Ibrahim I, Lim HN, Huang NM, Pandikumar A
    PLoS One, 2016;11(5):e0154557.
    PMID: 27176635 DOI: 10.1371/journal.pone.0154557
    A photoelectrochemical (PEC) sensor with excellent sensitivity and detection toward copper (II) ions (Cu2+) was developed using a cadmium sulphide-reduced graphene oxide (CdS-rGO) nanocomposite on an indium tin oxide (ITO) surface, with triethanolamine (TEA) used as the sacrificial electron donor. The CdS nanoparticles were initially synthesized via the aerosol-assisted chemical vapor deposition (AACVD) method using cadmium acetate and thiourea as the precursors to Cd2+ and S2-, respectively. Graphene oxide (GO) was then dip-coated onto the CdS electrode and sintered under an argon gas flow (50 mL/min) for the reduction process. The nanostructured CdS was adhered securely to the ITO by a continuous network of rGO that also acted as an avenue to intensify the transfer of electrons from the conduction band of CdS. The photoelectrochemical results indicated that the ITO/CdS-rGO photoelectrode could facilitate broad UV-visible light absorption, which would lead to a higher and steady-state photocurrent response in the presence of TEA in 0.1 M KCl. The photocurrent decreased with an increase in the concentration of Cu2+ ions. The photoelectrode response for Cu2+ ion detection had a linear range of 0.5-120 μM, with a limit of detection (LoD) of 16 nM. The proposed PEC sensor displayed ultra-sensitivity and good selectivity toward Cu2+ ion detection.
  14. Kwan MK, Chooi WK, Lim HH
    Med J Malaysia, 2004 Dec;59 Suppl F:14-8.
    PMID: 15941155
    Between April 1998 and December 1999, thirty patients with Idiopathic Scoliosis were operated with Multisegmented Hook-Rod System. These patients were operated at the mean age of 16 years and were followed up for a mean of 22.3 months (range 13-34 months). Seven patients had anterior release to increase the curve flexibility followed by second stage posterior instrumentation on the same day. The average operating time for a posterior instrumentation alone and anterior release combined with posterior instrumentation were 270 minutes and 522 minutes respectively. The average blood loss was 2.2 litres for posterior instrumentation alone and 3.3 litres for single day anterior release and posterior surgery. The mean preoperative Cobb's angle was 70 degrees. The mean immediate postoperative and final follow up Cobb's angles were 38 and 42 degrees, which represented an average coronal plane correction of 46.7% and 40.0% respectively. The mean preoperative apical vertebral rotation was 25 degrees, which improved to 15 degrees after the operation. At final follow up, the mean apical vertebra rotation was 20 degrees, which represented a mean apical vertebral rotation correction of 20%. Complications of the procedure included one transient neurological deficit, one infection, one graft site infection and one case of screw cut out. We were able to obtain satisfactory correction of idiopathic scoliosis with the Multisegmented Hook-Rod System.
  15. Lee SX, Lim HN, Ibrahim I, Jamil A, Pandikumar A, Huang NM
    Biosens Bioelectron, 2017 Mar 15;89(Pt 1):673-680.
    PMID: 26718548 DOI: 10.1016/j.bios.2015.12.030
    In this study, a disposable and simple electrochemical immunosensor was fabricated for the detection of carcinoembryonic antigen. In this method, silver nanoparticles (AgNPs) were mixed with reduced graphene oxide (rGO) to modify the surface of screen-printed carbon electrode (SPE). Initially, AgNPs-rGO modified-SPEs were fabricated by using simple electrochemical deposition method. Then the carcinoembryonic antigen (CEA) was immobilized between the primary antibody and horseradish peroxidase (HRP)-conjugated secondary antibody onto AgNPs-rGO modified-SPEs to fabricate a sandwich-type electrochemical immunosensor. The proposed method could detect the CEA with a linear range of 0.05-0.50µgmL-1 and a detection limit down to 0.035µgmL-1 as compared to its non-sandwich counterpart, which yielded a linear range of 0.05-0.40µgmL-1, with a detection limit of 0.042µgmL-1. The immunosensor showed good performance in the detection of carcinoembryonic antigen, exhibiting a simple, rapid and low-cost. The immunosensor showed a higher sensitivity than an enzymeless sensor.
  16. Lim H, Chee H
    Malays J Nutr, 1998 Dec;4(1):31-54.
    PMID: 22692340 MyJurnal
    The study was conducted to determine the nutritional status and reproductive health of 34 Orang Asli women, aged 16-45 years, from two Orang Asli villages in Kuantan, Pahang Darul Makmur.The results of the study indicate that on the whole, the women's nutritional status is generally not satisfactory.Their mean iron intakes for example, are very low, about one-quarter to one-third of the required level.All their other mean nutrient intake levels are below the required level. Only their mean intake of vitamin C exceeds the required level due to their frequent intake of raw vegetables. Their main source of carbohydrate is rice, while their main source of protein is fish, and their main source of minerals and vitamins are Chinese mustard and cabbage.From BMI measurements, it is found that less than half of the women (42.9%) have normal weight, 35.7% suffer from chronic energy deficiency (CED), 7.1% (one) are overweight, and 14.3% (two) are obese.The accessibility and availability of food are a problem for the women, limiting their choice of varieties of food sources.For their reproductive health needs, the pregnant women rely on the government hospital and clinics for their antenatal check-ups and birth deliveries.Of all the women, nine suffer from menstrual pain and five from vaginal discharge.Food taboos and cultural practices are practised by the pregnant women during their confinement.It is concluded that the nutritional status of the women needs to be improved since most of them have insufficient nutrient intake.
  17. Lim H, Zainal Abidin M, Pulungan CP, de Bruyn M, Mohd Nor SA
    PLoS One, 2016 Sep 22;11(9):e0163596.
    PMID: 27657915 DOI: 10.1371/journal.pone.0163596
    DNA barcoding of the cytochrome oxidase subunit I (COI) gene was utilized to assess the species diversity of the freshwater halfbeak genus Hemirhamphodon. A total of 201 individuals from 46 locations in Peninsular Malaysia, north Borneo (Sarawak) and Sumatra were successfully amplified for 616 base pairs of the COI gene revealing 231 variable and 213 parsimony informative sites. COI gene trees showed that most recognized species form monophyletic clades with high bootstrap support. Pairwise within species comparisons exhibited a wide range of intraspecific diversity from 0.0% to 14.8%, suggesting presence of cryptic diversity. This finding was further supported by barcode gap analysis, ABGD and the constructed COI gene trees. In particular, H. pogonognathus from Kelantan (northeast Peninsular Malaysia) diverged from the other H. pogonognathus groups with distances ranging from 7.8 to 11.8%, exceeding the nearest neighbor taxon. High intraspecific diversity was also observed in H. byssus and H. kuekanthali, but of a lower magnitude. This study also provides insights into endemism and phylogeographic structuring, and limited support for the Paleo-drainage divergence hypothesis as a driver of speciation in the genus Hemirhamphodon.
  18. Lim H, Chuah JA, Chek MF, Tan HT, Hakoshima T, Sudesh K
    Int J Biol Macromol, 2021 Sep 01;186:414-423.
    PMID: 34246679 DOI: 10.1016/j.ijbiomac.2021.07.041
    Polyhydroxyalkanoates (PHAs) are biopolyesters synthesized by microorganisms as intracellular energy reservoirs under stressful environmental conditions. PHA synthase (PhaC) is the key enzyme responsible for PHA biosynthesis, but the importance of its N- and C-terminal ends still remains elusive. Six plasmid constructs expressing truncation variants of Aquitalea sp. USM4 PhaC (PhaC1As) were generated and heterologously expressed in Cupriavidus necator PHB-4. Removal of the first six residues at the N-terminus enabled the modulation of PHA composition without altering the PHA content in cells. Meanwhile, deletion of 13 amino acids from the C-terminus greatly affected the catalytic activity of PhaC1As, retaining only 1.1-7.4% of the total activity. Truncation(s) at the N- and/or C-terminus of PhaC1As gradually diminished the incorporation of comonomer units, and revealed that the N-terminal region is essential for PhaC1As dimerization whereas the C-terminal region is required for stabilization. Notably, transmission electron microscopy analysis showed that PhaC modification affected the morphology of intracellular PHA granules, which until now is only known to be regulated by phasins. This study provided substantial evidence and highlighted the significance of both the N- and C-termini of PhaC1As in regulating intracellular granule morphology, activity, substrate specificity, dimerization and stability of the synthase.
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