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  1. Encapsulation of Ethylene Gas into Granular Cold-Water-Soluble Starch: Structure and Release Kinetics
    Shi L, Fu X, Tan CP, Huang Q, Zhang B
    J Agric Food Chem, 2017 Mar 15;65(10):2189-2197.
    PMID: 28215072 DOI: 10.1021/acs.jafc.6b05749
    Ethylene gas was introduced into granular cold-water-soluble (GCWS) starches using a solid encapsulation method. The morphological and structural properties of the novel inclusion complexes (ICs) were characterized using scanning electron microscopy, X-ray diffractometry, and Raman spectroscopy. The V-type single helix of GCWS starches was formed through controlled gelatinization and ethanol precipitation and was approved to host ethylene gas. The controlled release characteristics of ICs were also investigated at various temperature and relative humidity conditions. Avrami's equation was fitted to understand the release kinetics and showed that the release of ethylene from the ICs was accelerated by increasing temperature or RH and was decelerated by increased degree of amylose polymerization. The IC of Hylon-7 had the highest ethylene concentration (31.8%, w/w) among the five starches, and the IC of normal potato starch showed the best controlled release characteristics. As a renewable and inexpensive material, GCWS starch is a desirable solid encapsulation matrix with potential in agricultural and food applications.
    Matched MeSH terms: Polymerization
  2. Fulltext Effects of resin cements on hardness and thickness around titanium post: an intraradicular assessment
    Lim, Siau Peng, Fazal Reza, Zaihan Ariffin
    Archives of Orofacial Sciences, 2011;6(2):1-10.
    MyJurnal
    The purpose of this study was to evaluate hardness (indicator for polymerization) and thickness of two types of resin cement at coronal, middle and apical level of tooth root canal. Ten extracted maxillary incisors were instrumented and post space was prepared for cementation of titanium post. Samples were divided into two groups and each group was cemented either of the two types of resin cements; Panavia F [dual-cured (PF)] and Rely X Luting 2 [self-cured (RL)]. The teeth were longitudinally sectioned; hardness and thickness was measured using Vickers hardness tester and a microscope (Leica DMLM). SEM observations along the cement line at the 3 different root levels were performed. Statistical analysis was performed to test significance of differences in hardness and thickness of the two types of cement (t-test; p= 0.05) and at different levels of the same type (one-way ANOVA followed by multiple comparison; p= 0.05). Significant difference of hardness was found at the apical level between the two groups and between the coronal and apical level of PF (p0.05). Moreover, voids were more obvious within the dual-cured group of cement. Dual-cured resin cement was found to be less polymerized than self-cured type at apical level. Increased thicknesses of resin cements in comparison to post space size were observed in both groups. Use of metallic post with resin cements needs further evaluation.
    Matched MeSH terms: Polymerization
  3. Fulltext Polymerization Shrinkage and Degree of Conversion of New Zirconia-Reinforced Rice Husk Nanohybrid Composite
    Lin GSS, Abdul Ghani NRN, Ismail NH, Singbal KP, Yusuff NMM
    Eur J Dent, 2020 Jul;14(3):448-455.
    PMID: 32599624 DOI: 10.1055/s-0040-1713951
    OBJECTIVES:  This study aimed to compare the polymerization shrinkage and degree of conversion of new zirconia-reinforced rice husk nanohybrid composite with commercialized microhybrid and nanofilled composites.

    MATERIALS AND METHODS:  Overall, 180 samples were used for polymerization shrinkage (buoyancy and optical methods) and degree of conversion tests in which they were divided into Group 1, nanofilled composite (Filtek-Z350- XT; 3M ESPE, St Paul, MN 55144-1000, USA), Group 2, microhybrid composite (Zmack-Comp), and Group 3, nanohybrid composite (Zr-Hybrid). Polymerization shrinkage test was performed using buoyancy and optical methods. For buoyancy method, samples were weighed in air and water to calculate the shrinkage value, whereas, for optical method, images of nonpolymerized samples were captured under a digital microscope and recaptured again after light-cured to calculate the percentage of shrinkage. Degree of conversion was tested using Fourier-transform infrared spectroscopy spectrometer.

    STATISTICAL ANALYSIS:  Data were analyzed using one-way analysis of variance complemented by post hoc Dunnett's T3 test for polymerization shrinkage and Tukey's honestly significant difference test for degree of conversion. Level of significance was set at p < 0.05.

    RESULTS:  Group 3 demonstrated similar polymerization shrinkage with Group 1, but lower shrinkage (p < 0.05) than Group 2 based on buoyancy method. However, optical method (p < 0.05) showed that Group 3 had the lowest shrinkage, followed by Group 1 and lastly Group 2. Besides, Group 3 showed a significantly higher degree of conversion (p < 0.05) than Group 1 and comparable conversion value with Group 2.

    CONCLUSIONS:  Zirconia-reinforced rice husk nanohybrid composite showed excellent shrinkage and conversion values, hence can be considered as an alternative to commercially available composite resins.

    Matched MeSH terms: Polymerization
  4. Fulltext A Cell Internalizing Antibody Targeting Capsid Protein (p24) Inhibits the Replication of HIV-1 in T Cells Lines and PBMCs: A Proof of Concept Study
    Ali SA, Teow SY, Omar TC, Khoo AS, Choon TS, Yusoff NM
    PLoS One, 2016;11(1):e0145986.
    PMID: 26741963 DOI: 10.1371/journal.pone.0145986
    There remains a need for newer therapeutic approaches to combat HIV/AIDS. Viral capsid protein p24 plays important roles in HIV pathogenesis. Peptides and small molecule inhibitors targeting p24 have shown to inhibit virus replication in treated cell. High specificity and biological stability of monoclonal antibodies (mAbs) make them an attractive contender for in vivo treatments. However, mAbs do not enter into cells, thus are restricted to target surface molecules. This also makes targeting intracellular HIV-1 p24 a challenge. A mAb specific to p24 that can internalize into the HIV-infected cells is hypothesized to inhibit the virus replication. We selected a mAb that has previously shown to inhibit p24 polymerization in an in vitro assay and chemically conjugated it with cell penetrating peptides (CPP) to generate cell internalizing anti-p24 mAbs. Out of 8 CPPs tested, κFGF-MTS -conjugated mAbs internalized T cells most efficiently. At nontoxic concentration, the κFGF-MTS-anti-p24-mAbs reduced the HIV-1 replication up to 73 and 49% in T-lymphocyte and PBMCs respectively. Marked inhibition of HIV-1 replication in relevant cells by κFGF-MTS-anti-p24-mAbs represents a viable strategy to target HIV proteins present inside the cells.
    Matched MeSH terms: Polymerization
  5. Fulltext Physico-mechanical, thermal and morphological properties of furfuryl alcohol/2-ethylhexyl methacrylate/halloysite nanoclay wood polymer nanocomposites (WPNCs)
    Rahman MR, Hamdan S, Lai JCH, Jawaid M, Yusof FABM
    Heliyon, 2017 Jul;3(7):e00342.
    PMID: 28725868 DOI: 10.1016/j.heliyon.2017.e00342
    In this study, the physical, morphological, mechanical and thermal properties of furfuryl alcohol/2-ethylhexyl methacrylate/halloysite nanoclay wood polymer nanocomposites (FA-co-EHMA-HNC WPNCs) were investigated. FA-co-EHMA-HNC WPNCs were prepared via an impregnation method and the properties of the nanocomposites were characterized through the weight percent gain, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), three-point flexural test, dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) analysis and moisture absorption test. The weight percent gain in the 50:50 FA-co-EHMA-HNC WPNC was the highest compared with the raw wood (RW) and other WPNCs. The FT-IR results confirmed that polymerization took place in the nanocomposites, especially 50:50 FA-co-EHMA-HNC WPNC, which had a reduced amount of hydroxyl groups. The SEM results revealed that the 50:50 FA-co-EHMA-HNC WPNC had the smoothest and most uniform surface among all of the nanocomposites. The 50:50 FA-co-EHMA-HNC WPNC showed the highest flexural strength and modulus of elasticity. The results revealed that the storage modulus and loss modulus of the FA-co-EHMA-HNC WPNCs were higher and the tan δ of FA-co-EHMA-HNC WNPCs was lower compared with the RW. The FA-co-EHMA-HNC WPNCs exhibited the higher thermal stability in the TGA and DSC analysis. The 50:50 FA-co-EHMA-HNC WPNC exhibited remarkably lower moisture absorption compared with the RW. Overall, this study proved that the ratio 50:50 FA-co-EHMA ratio was the most suitable for introduction in the in the RW.
    Matched MeSH terms: Polymerization
  6. A urea precursor to synthesize carbon nitride with mesoporosity for enhanced activity in the photocatalytic removal of phenol
    Lee SC, Lintang HO, Yuliati L
    Chem Asian J, 2012 Sep;7(9):2139-44.
    PMID: 22733646 DOI: 10.1002/asia.201200383
    A urea precursor was used for the first time to prepare mesoporous carbon nitride (MCN) by a thermal polymerization process with silica nanospheres as a hard template. Although the prepared MCN samples have similar structures and optical properties, it was revealed that the specific surface area, pore-size distribution, and morphology of the MCN samples depend on the initial mass ratio of urea to silica. Compared to the bulk carbon nitride (BCN) that only gave 20% phenol removal (6 h of irradiation), the activities can be enhanced up to 74% on MCN samples for photocatalytic removal of phenol under visible-light irradiation. The highest conversion was obtained on MCN with an initial mass ratio of urea to silica of 5, which has high surface area of 191 m(2) g(-1) and a nanoporous structure with uniform pore-size distribution of 7 nm. In addition to the high activity, the MCN sample also showed high photocatalytic stability.
    Matched MeSH terms: Polymerization
  7. Fulltext Effect of beverages and food source on wear resistance of composite resins
    Seow, L.L., Chong, S.Y., Lau, M.N., Tiong, S.G., Yew, C.C.
    Malaysian Dental Journal, 2008;29(1):34-39.
    MyJurnal
    Certain beverages e.g. coffee, tea, soft drinks, fruit juices, alcoholic beverages, may affect the physical properties of composite resins. Objectives: The objectives of this study were to: (1) evaluate the effect of different beverages and chilli sauce on the wear resistance of composite resins, (2) evaluate effect of the duration of immersion in the beverages and chilli sauce on the wear resistance of composite resins.

    Materials and methods: Disc specimens were fabricated using two different types of composite resins: (i) Filtek Z350 (3M ESPE, USA, nano-filled composite, 40 specimens) and (ii) Solare P (GC Dental Products Corp, Japan, microhybrid composite, 40 specimens). After polymerization, all the specimens were polished using Enhance Polishing System (Dentsply International Inc.,USA). The specimens were air-dried before weighing using Sartorius BP 221S weighing balance (Sartorius AG, Goettingen, Germany). Ten specimens from each type of composite were immersed in distilled water (control group), Coca cola®, orange juice (Peel Fresh®) and chilli sauce (Maggi®) respectively. The duration of immersion was 6 hours and 1 week. A reciprocal compression-sliding system was used to evaluate the wear resistance of the specimens. The specimens were moved back and forth with a loaded counter-body (235g) against sand paper (P1000, 3M ESPE, USA) in running water. The weight of the specimens were measured after 6 hours of immersion and 20,000 wear cycles and also at 1 week of immersion with further 20,000 wear cycles. The wear resistances were tabulated as percentage of weight loss from the specimens. Results were statistically analyzed using one way ANOVA and post-hoc Tukey’s test (p= 0.05).
    Results: The results showed that Solare P has significantly lower wear resistance compared to Filtek Z350. There was no significant difference in wear resistance for Filtek Z350 when immersed in chili sauce, Coca-cola® and orange juice in comparison with control group for 6 hours and 1 week. Similar findings were observed for Solare P.

    Conclusion: Within the limitations of this study, it was concluded that Solare P has poorer wear resistance than Filtek Z350. The soaking medium investigated and duration of immersion have no influence on the wear resistance of Solare P and Filtek Z350.
    Matched MeSH terms: Polymerization
  8. Fulltext The Influence of Ziegler-Natta and Metallocene Catalysts on Polyolefin Structure, Properties, and Processing Ability
    Shamiri A, Chakrabarti MH, Jahan S, Hussain MA, Kaminsky W, Aravind PV, et al.
    Materials (Basel), 2014 Jul 09;7(7):5069-5108.
    PMID: 28788120 DOI: 10.3390/ma7075069
    50 years ago, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds and aluminum-alkyls as co-catalysts. Polyolefins have grown to become one of the biggest of all produced polymers. New metallocene/methylaluminoxane (MAO) catalysts open the possibility to synthesize polymers with highly defined microstructure, tacticity, and steroregularity, as well as long-chain branched, or blocky copolymers with excellent properties. This improvement in polymerization is possible due to the single active sites available on the metallocene catalysts in contrast to their traditional counterparts. Moreover, these catalysts, half titanocenes/MAO, zirconocenes, and other single site catalysts can control various important parameters, such as co-monomer distribution, molecular weight, molecular weight distribution, molecular architecture, stereo-specificity, degree of linearity, and branching of the polymer. However, in most cases research in this area has reduced academia as olefin polymerization has seen significant advancements in the industries. Therefore, this paper aims to further motivate interest in polyolefin research in academia by highlighting promising and open areas for the future.
    Matched MeSH terms: Polymerization
  9. Fulltext Depth of polymerization of a new nanocomposite according to different exposure times and shades
    Lui, J.L., Chan, C.L., Yap, K.T.
    Ann Dent, 2006;13(1):6-11.
    MyJurnal
    The aim of the study was to determine the depth of cure of a new nanocomposite when exposed to different curing times and also when different shades were polymerized. The nanocomposite, Filtek Supreme (3M ESPE), was packed into 96 plastic cylindrical moulds measuring 4 mm in internal diameter and 8 mm in length and then polymerized using a conventional quartz-tungsten-halogen light curing unit. The first part of the study involved curing 16 samples each of A2 shade of the nanocomposite at exposure times of 20s, 40s, 60s and 120s. For the second part, a similar number of samples of the dentinal opacity shades of A2, B3 and A4 of the nanocomposite were polymerized at a constant exposure time of 40s. The depth of polymerization of the nanocomposite in each sample was measured using a digimatic indicator. Curing depths were found to increase significantly (P < 0.05) with longer exposure time (20s < 40s < 60s < 120s) and decrease significantly with darker shades (A2 > B3 > A4).
    Matched MeSH terms: Polymerization
  10. Fulltext Dataset in characterization of the polymer produced using different method of synthesis polychloromethylstyrene (PCMS) with clay and without clay
    Ismail N, Nazri NK, Abdullah AA, Wan Nik WMN, Wright LJ
    Data Brief, 2021 Feb;34:106738.
    PMID: 33521179 DOI: 10.1016/j.dib.2021.106738
    Polychloropolymethylstyrene (PCMS) polymers were synthesized with clay Cloisite and without clay Cloisite and chloromethylstyrene (CMS) combine with styrene (1:1) v/v or known as copolymer and clay Cloisite by the polymerization process. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra of each polymer synthesized are reported. The spectra of IR shows the different value of the wavenumber and intensity for each set of different sample. The spectra can be as a reference for others to use in synthesizing this polymer and clay Cloisite for different type of application.
    Matched MeSH terms: Polymerization
  11. Fulltext Application of Zwitterions in Forward Osmosis: A Short Review
    Chiao YH, Sengupta A, Ang MBMY, Chen ST, Haan TY, Almodovar J, et al.
    Polymers (Basel), 2021 Feb 15;13(4).
    PMID: 33672026 DOI: 10.3390/polym13040583
    Forward osmosis (FO) is an important desalination method to produce potable water. It was also used to treat different wastewater streams, including industrial as well as municipal wastewater. Though FO is environmentally benign, energy intensive, and highly efficient; it still suffers from four types of fouling namely: organic fouling, inorganic scaling, biofouling and colloidal fouling or a combination of these types of fouling. Membrane fouling may require simple shear force and physical cleaning for sufficient recovery of membrane performance. Severe fouling may need chemical cleaning, especially when a slimy biofilm or severe microbial colony is formed. Modification of FO membrane through introducing zwitterionic moieties on the membrane surface has been proven to enhance antifouling property. In addition, it could also significantly improve the separation efficiency and longevity of the membrane. Zwitterion moieties can also incorporate in draw solution as electrolytes in FO process. It could be in a form of a monomer or a polymer. Hence, this review comprehensively discussed several methods of inclusion of zwitterionic moieties in FO membrane. These methods include atom transfer radical polymerization (ATRP); second interfacial polymerization (SIP); coating and in situ formation. Furthermore, an attempt was made to understand the mechanism of improvement in FO performance by zwitterionic moieties. Finally, the future prospective of the application of zwitterions in FO has been discussed.
    Matched MeSH terms: Polymerization
  12. Fulltext Post-polymerization of dental resin composite evaluated with nanoindentation and micro-Raman spectroscopy
    Mohamad, D., Young, R.J., Mann, A.B., Watts, D.C.
    Archives of Orofacial Sciences, 2007;2(1):26-31.
    MyJurnal
    The aim of the study was to evaluate post-polymerization of resin composite by measuring NanoHardness (H), Young’s Modulus (E) and Degree of Conversion (DC) using nanoindentation and Micro-Raman spectroscopy. For this purpose a computer-controlled NanoIndenter™ and a Renishaw 1000 Raman Spectrometer fitted with an Olympus microscope attachment, operated at 638 nm, were used. A light-activated resin composite was used in this study, (Z250, 3MESPE). Sub-groups (n=3) of specimens were irradiated for 20, 30, 40 s. All samples for nanoindentation were polished metallographically and typically 50 nanoindentations were performed per specimen. After curing and polishing, half of the samples were tested immediately (Group 1); the others after being stored dry at 37 °C for 7 days (Group 2) to allow scope for postpolymerization. H values ranged from 1.08 to 1.40 GPa for Group 1, and from 1.64 to1.71 GPa for Group 2. E values in Group 1 ranged from 19.60 to 19.94 GPa and for Group 2, from 21.42 to 22.05 GPa. DC values ranged from 55 to 66.39%, and 60.90 to 66.47% for Group 1 and Group 2 respectively. All values obtained shown significant different between Groups 1 and 2 (p
    Matched MeSH terms: Polymerization
  13. Preparation of methacrylamide-functionalized crosslinked chitosan by free radical polymerization for the removal of lead ions
    Sutirman ZA, Sanagi MM, Abd Karim KJ, Wan Ibrahim WA
    Carbohydr Polym, 2016 Oct 20;151:1091-1099.
    PMID: 27474659 DOI: 10.1016/j.carbpol.2016.06.076
    A new poly(methacrylamide) grafted crosslinked chitosan was prepared for removal of lead, Pb(II) ion from aqueous solution. Crosslinked chitosan, in beads form, was grafted with methacrylamide (MAm) using ammonium persulfate (APS) as free radical initiator. Evidence of grafting was determined by comparing FTIR, TGA, SEM and (13)C NMR analyses of chitosan and graft copolymer. The optimal conditions for grafting reaction were as follow: crosslinked chitosan beads (1g), MAm (17.62×10(-1)M), APS (2.63×10(-1)M), reaction time (3h) and temperature (60°C). The modified chitosan bead was then used in laboratory batch experiments to evaluate the removal of Pb(II) ion from water samples. The Langmuir and Freundlich adsorption models were also applied to describe the equilibrium isotherms. The results revealed that the adsorption of Pb(II) ions onto the beads fitted very well with the Langmuir model with the maximum capacity (qmax) of 250mgg(-1).
    Matched MeSH terms: Polymerization
  14. New efficient chitosan derivative for Cu(II) ions removal: Characterization and adsorption performance
    Sutirman ZA, Rahim EA, Sanagi MM, Abd Karim KJ, Wan Ibrahim WA
    Int J Biol Macromol, 2020 Jun 15;153:513-522.
    PMID: 32142849 DOI: 10.1016/j.ijbiomac.2020.03.015
    A new crosslinked chitosan grafted with methyl methacrylate (M-CTS) adsorbent was synthesized via free radical polymerization for effective removal of Cu(II) ions from aqueous solution. Crosslinked chitosan (1 g) was grafted with 29.96 × 10-1 M methyl methacrylate in the presence of 2.63 × 10-1 M ammonium persulfate as initiator at 60 °C for 2 h to give grafting and yield percentages of 201% and 67%, respectively. Batch adsorption experiment was performed as a function of solution pH, initial metal ion concentration and contact time. The isotherm data were adequately described by Langmuir model, while kinetic study revealed that the pseudo-second order rate model best fitted for the experimental data. The maximum adsorption capacity for M-CTS at pH 4 was 192.31 mg g-1. Furthermore, the reusability of over six adsorption-desorption cycles suggested that M-CTS is a durable adsorbent and good candidate for metal ions treatment.
    Matched MeSH terms: Polymerization
  15. Prosthetic Rehabilitation of Cranial Deformity in Hyperostotic Convexity Meningioma
    Nandini Y, Venkatesh SB
    Contemp Clin Dent, 2019 11 28;9(4):674-677.
    PMID: 31772486 DOI: 10.4103/ccd.ccd_537_18
    Cranial defects lead to unesthetic appearance and are a constant source of apprehension to the patient. Meningioma with calvarial extension requires the excision of the involved bone for complete excision. Such total excision would leave behind a bony defect which would need reconstruction. Presurgical fabrication of acrylic flap helps in reconstruction of such cranial defect following complete excision in single stage, thereby decreasing the cost and morbidity of surgery. Further, it facilitates the reproduction of the contours, and the tissue bed is not exposed to the heat of polymerization or to the free monomer. The authors report a case of hyperostotic convexity meningioma in a middle-aged female where heat-cured acrylic resin alloplastic implant was prefabricated and used successfully.
    Matched MeSH terms: Polymerization
  16. The use of differential scanning fluorimetry in the rational design of plastic antibodies for protein targets
    Ashley J, Shukor Y, Tothill IE
    Analyst, 2016 Nov 14;141(23):6463-6470.
    PMID: 27813538
    The development of molecularly imprinted polymer nanoparticles (MIP-NPs), which specifically bind biomolecules, is of great interest in the area of biosensors, sample purification, therapeutic agents and biotechnology. Polymerisation techniques such as precipitation polymerisation, solid phase synthesis and core shell surface imprinting have allowed for significant improvements to be made in developing MIP-NPs which specifically recognise proteins. However, the development of MIP-NPs for protein templates (targets) still require lengthy optimisation and characterisation using different ratios of monomers in order to control their size, binding affinity and specificity. In this work we successfully demonstrated that differential scanning fluorimetry (DSF) can be used to rapidly determine the optimum imprinting conditions and monomer composition required for MIP-NP design and polymerisation. This is based on the stability of the protein template and shift in apparent melting points (Tm) upon interaction with different functional acrylic monomers. The method allows for the characterisation of molecularly imprinted nanoparticles (MIP-NPs) due to the observed differences in melting point profiles between, protein-MIP-NPs complexes, pre-polymerisation mixtures and non-imprinted nanoparticles (NIP-NPs) without the need for prior purification. The technique is simple, rapid and can be carried out on most quantitative polymerase chain reaction (qPCR) thermal cyclers which have the required filters for SYPRO
    Matched MeSH terms: Polymerization
  17. PHA synthase (PhaC): interpreting the functions of bioplastic-producing enzyme from a structural perspective
    Chek MF, Hiroe A, Hakoshima T, Sudesh K, Taguchi S
    Appl Microbiol Biotechnol, 2019 Feb;103(3):1131-1141.
    PMID: 30511262 DOI: 10.1007/s00253-018-9538-8
    Polyhydroxyalkanoates (PHAs) are biopolymers synthesized by a wide range of bacteria, which serve as a promising candidate in replacing some conventional petrochemical-based plastics. PHA synthase (PhaC) is the key enzyme in the polymerization of PHA, and the crystal structures were successfully determined using the catalytic domain of PhaC from Cupriavidus necator (PhaCCn-CAT) and Chromobacterium sp. USM2 (PhaCCs-CAT). Here, we review the beneficial mutations discovered in PhaCs from a structural perspective. The structural comparison of the residues involved in beneficial mutation reveals that the residues are near to the catalytic triad, but not inside the catalytic pocket. For instance, Ala510 of PhaCCn is near catalytic His508 and may be involved in the open-close regulation, which presumably play an important role in substrate specificity and activity. In the class II PhaC1 from Pseudomonas sp. 61-3 (PhaC1Ps), Ser325 stabilizes the catalytic cysteine through hydrogen bonding. Another residue, Gln508 of PhaC1Ps is located in a conserved hydrophobic pocket which is next to the catalytic Asp and His. A class I, II-conserved Phe420 of PhaCCn is one of the residues involved in dimerization and its mutation to serine greatly reduced the lag phase. The current structural analysis shows that the Phe362 and Phe518 of PhaC from Aeromonas caviae (PhaCAc) are assisting the dimer formation and maintaining the integrity of the core beta-sheet, respectively. The structure-function relationship of PhaCs discussed in this review will serve as valuable reference for future protein engineering works to enhance the performance of PhaCs and to produce novel biopolymers.
    Matched MeSH terms: Polymerization
  18. Modelling of polyhydroxyalkanoate synthase from Aquitalea sp. USM4 suggests a novel mechanism for polymer elongation
    Teh AH, Chiam NC, Furusawa G, Sudesh K
    Int J Biol Macromol, 2018 Nov;119:438-445.
    PMID: 30048726 DOI: 10.1016/j.ijbiomac.2018.07.147
    Polyhydroxyalkanoate (PHA) synthase, PhaC, is a key enzyme in the biosynthesis of PHA, a type of bioplastics with huge potential to replace petroleum-based plastics. While two structures have been determined, the exact mechanism remains unclear partly due to the absence of a tunnel for product passage. A model of the class I PhaC from Aquitalea sp. USM4, characterised with Km of 394 μM and kcat of 476 s-1 on 3-(R)-hydroxybutyryl-CoA, revealed a three-branched channel at the dimeric interface. Two of them are opened to the solvent and are expected to serve as the putative routes for substrate entrance and product exit, while the third is elongated in the class II PhaC1 model from Pseudomonas aeruginosa, indicating a role in accommodating the hydroxyalkanoate (HA) moiety of a HA-CoA substrate. Docking of the two tetrahedral intermediates, formed during the transfer of the growing PHA chain from the catalytic Cys to a new molecule of substrate and back to Cys, suggests a common elongation mechanism requiring the HA moiety of the ligand to rotate ~180°. Substrate specificity is determined in part by a bulky Phe/Tyr/Trp residue in the third branch in class I, which is conserved as Ala in class II to create room for longer substrates.
    Matched MeSH terms: Polymerization
  19. Fulltext Synthesis and adsorption studies for newly prepared Ni2+-imprinted polymer co-functionalized with picolinic acid
    Mehamod, F.S., Kadir, M.A., Jusoh, N., Yusof, N.F., Suah, F.B.
    ASM Science Journal, 2018;11(101):114-123.
    MyJurnal
    The development of new adsorbent has rapidly increased in order to overcome the problem
    of waste water treatment from heavy metal pollution. The ability of nickel (II)-ion imprinted
    polymer (Ni-IIP) as an alternative adsorbent for the removal of nickel ion from aqueous has
    been investigated. The Ni-IIP was prepared via bulk polymerization by using functional
    monomers; methylacrylic acid (MAA) with picolinic acid as a co-monomer. Nickel ion was
    used as template, AIBN as initiator and EGDMA as cross-linking agent. Non-imprinted control
    polymer (NIP) was prepared in the same manner as Ni-IIP but in the absence of nickel
    ion. The resultant of Ni-IIP and NIP were characterized by using Fourier Transform Infrared
    (FTIR) spectroscopy and Scanning Electron Microscope (SEM). Result showed that, the adsorption
    of nickel ion onto Ni-IIP increased as the adsorbent dosage increased and contact
    time is prolonged. The adsorption isotherm model for Ni-IIP and NIP were fitted well with
    Freundlich and Langmuir, respectively. Kinetic study for both Ni-IIP and NIP were followed
    the pseudo-second order, indicates that the rate-limiting step is the surface adsorption that
    involves chemisorption. Selectivity studies showed that the distribution coefficient of Ni2+
    was higher compared to Zn2+, Mg2+ and Pb2+. The present work has successfully synthesized
    Ni-IIP particles with good potential in recognition of Ni2+ ions in an aqueous medium.
    Matched MeSH terms: Polymerization
  20. Microbial biosynthesis and in vivo depolymerization of intracellular medium-chain-length poly-3-hydroxyalkanoates as potential route to platform chemicals
    Anis SNS, Mohd Annuar MS, Simarani K
    Biotechnol Appl Biochem, 2018 Nov;65(6):784-796.
    PMID: 29806235 DOI: 10.1002/bab.1666
    Biosynthesis and in vivo depolymerization of intracellular medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA) in Pseudomonas putida Bet001 grown on lauric acid were studied. Highest mcl-PHA fraction (>50 % of total biomass) and cell concentration (8 g L-1 ) were obtained at carbon-to-nitrogen (C/N) ratio 20, starting cell concentration 1 g L-1 , and 48 H fermentation. The mcl-PHA comprised of 3-hydroxyhexanoate (C6 ), 3-hydroxyoctanote (C8 ), 3-hydroxydecanoate (C10 ), and 3-hydroxydodecanoate (C12 ) monomers. In vivo action was studied in a mineral liquid medium without carbon source, and in different buffer solutions with varied pH, molarity, ionic strength, and temperature. The monomer liberation rate reflected the mol percentage distribution of the initial polymer subunit composition. Rate and percentage of in vivo depolymerization were highest in 0.2 M Tris-HCl buffer (pH 9, strength = 0.2 M, 30 °C) at 0.21 g L-1  H-1 and 98.6 ± 1.3 wt%, respectively. There is a congruity vis-à-vis to specific buffer type, molarity, pH, ionic strength, and temperature values for superior in vivo depolymerization activities. Direct products from in vivo depolymerization matched the individual monomeric composition of native mcl-PHA. It points to exo-type reaction for the in vivo process, and potential biological route to chiral molecules.
    Matched MeSH terms: Polymerization*
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