Displaying publications 241 - 260 of 320 in total

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  1. Targeting chemical and thermal stability of ovalbumin by simulated honey sugar cocktail
    Wong YH, Kadir HA, Tayyab S
    Int J Biol Macromol, 2015 Feb;73:207-14.
    PMID: 25434804 DOI: 10.1016/j.ijbiomac.2014.11.015
    Effect of simulated honey sugar cocktail (SHSC) on chemical and thermal stability of ovalbumin (OVA) was investigated using multiple-spectroscopic techniques. Urea-induced denaturation of OVA produced a transition, characterized by the start-, the mid- and the end-points at 3.2 M, 5.9/5.6 M and 8.5/8.0 M urea, respectively, when studied by MRE222nm and tryptophan fluorescence measurements. Presence of 10% or 20% (w/v) SHSC in the incubation mixture shifted the transition curve towards higher urea concentration in a concentration dependent manner. A comparison of far- and near-UV CD, UV-difference, ANS fluorescence and 3-D fluorescence spectral results of native OVA and 5.9 M urea-denatured OVA (U-OVA), obtained in the absence and the presence of 20% (w/v) SHSC suggested SHSC-induced stabilization of U-OVA. Furthermore, a significant shift towards higher denaturant concentration was also noticed in the GdnHCl and thermal transition curves of OVA in the presence of 20% (w/v) SHSC. Taken together, all these results suggested stabilization of OVA against chemical and thermal denaturations by SHSC.
    Matched MeSH terms: Thermodynamics
  2. Fulltext Physicochemical characterization and thermodynamic studies of nanoemulsion-based transdermal delivery system for fullerene
    Ngan CL, Basri M, Tripathy M, Abedi Karjiban R, Abdul-Malek E
    ScientificWorldJournal, 2014;2014:219035.
    PMID: 25165736 DOI: 10.1155/2014/219035
    Fullerene nanoemulsions were formulated in palm kernel oil esters stabilized by low amount of mixed nonionic surfactants. Pseudoternary phase diagrams were established in the colloidal system of PKOEs/Tween 80 : Span 80/water incorporated with fullerene as antioxidant. Preformulation was subjected to combination of high and low energy emulsification methods and the physicochemical characteristics of fullerene nanoemulsions were analyzed using electroacoustic spectrometer. Oil-in-water (O/W) nanoemulsions with particle sizes in the range of 70-160 nm were formed. The rheological characteristics of colloidal systems exhibited shear thinning behavior which fitted well into the power law model. The effect of xanthan gum (0.2-1.0%, w/w) and beeswax (1-3%, w/w) in the estimation of thermodynamics was further studied. From the energetic parameters calculated for the viscous flow, a moderate energy barrier for transport process was observed. Thermodynamic study showed that the enthalpy was positive in all xanthan gum and beeswax concentrations indicating that the formation of nanoemulsions could be endothermic in nature. Fullerene nanoemulsions with 0.6% or higher xanthan gum content were found to be stable against creaming and flocculation when exposed to extreme environmental conditions.
    Matched MeSH terms: Thermodynamics
  3. Fulltext Synthesis Mechanism and Thermal Optimization of an Economical Mesoporous Material Using Silica: Implications for the Effective Removal or Delivery of Ibuprofen
    Kittappa S, Cui M, Ramalingam M, Ibrahim S, Khim J, Yoon Y, et al.
    PLoS One, 2015;10(7):e0130253.
    PMID: 26161510 DOI: 10.1371/journal.pone.0130253
    Mesoporous silica materials (MSMs) were synthesized economically using silica (SiO2) as a precursor via a modified alkaline fusion method. The MSM prepared at 500°C (MSM-500) had the highest surface area, pore size, and volume, and the results of isotherms and the kinetics of ibuprofen (IBP) removal indicated that MSM-500 had the highest sorption capacity and fastest removal speed vs. SBA-15 and zeolite. Compared with commercial granular activated carbon (GAC), MSM-500 had a ~100 times higher sorption rate at neutral pH. IBP uptake by MSM-500 was thermodynamically favorable at room temperature, which was interpreted as indicating relatively weak bonding because the entropy (∆adsS, -0.07 J mol(-1) K(-1)) was much smaller. Five times recycling tests revealed that MSM-500 had 83-87% recovery efficiencies and slower uptake speeds due to slight deformation of the outer pore structure. In the IBP delivery test, MSM-500 drug loading was 41%, higher than the reported value of SBA-15 (31%). The in vitro release of IBP was faster, almost 100%, reaching equilibrium within a few hours, indicating its effective loading and unloading characteristics. A cost analysis study revealed that the MSM was ~10-70 times cheaper than any other mesoporous silica material for the removal or delivery of IBP.
    Matched MeSH terms: Thermodynamics
  4. Supramolecular interaction of 6-shogaol, a therapeutic agent of Zingiber officinale with human serum albumin as elucidated by spectroscopic, calorimetric and molecular docking methods
    Feroz SR, Mohamad SB, Lee GS, Malek SN, Tayyab S
    Phytomedicine, 2015 Jun 01;22(6):621-30.
    PMID: 26055127 DOI: 10.1016/j.phymed.2015.03.016
    BACKGROUND: 6-Shogaol, one of the main bioactive constituents of Zingiber officinale has been shown to possess various therapeutic properties. Interaction of a therapeutic compound with plasma proteins greatly affects its pharmacokinetic and pharmacodynamic properties.

    PURPOSE: The present investigation was undertaken to characterize the interaction between 6-shogaol and the main in vivo transporter, human serum albumin (HSA).

    METHODS: Various binding characteristics of 6-shogaol-HSA interaction were studied using fluorescence spectroscopy. Thermal stability of 6-shogaol-HSA system was determined by circular dichroism (CD) and differential scanning calorimetric (DSC) techniques. Identification of the 6-shogaol binding site on HSA was made by competitive drug displacement and molecular docking experiments.

    RESULTS: Fluorescence quench titration results revealed the association constant, Ka of 6-shogaol-HSA interaction as 6.29 ± 0.33 × 10(4) M(-1) at 25 ºC. Values of the enthalpy change (-11.76 kJ mol(-1)) and the entropy change (52.52 J mol(-1) K(-1)), obtained for the binding reaction suggested involvement of hydrophobic and van der Waals forces along with hydrogen bonds in the complex formation. Higher thermal stability of HSA was noticed in the presence of 6-shogaol, as revealed by DSC and thermal denaturation profiles. Competitive ligand displacement experiments along with molecular docking results suggested the binding preference of 6-shogaol for Sudlow's site I of HSA.

    CONCLUSION: All these results suggest that 6-shogaol binds to Sudlow's site I of HSA through moderate binding affinity and involves hydrophobic and van der Waals forces along with hydrogen bonds.

    Matched MeSH terms: Thermodynamics
  5. Fulltext Synthesis, molecular structure and spectroscopic investigations of novel fluorinated spiro heterocycles
    Islam MS, Al-Majid AM, Barakat A, Soliman SM, Ghabbour HA, Quah CK, et al.
    Molecules, 2015 May 07;20(5):8223-41.
    PMID: 25961163 DOI: 10.3390/molecules20058223
    This paper describes an efficient and regioselective method for the synthesis of novel fluorinated spiro-heterocycles in excellent yield by cascade [5+1] double Michael addition reactions. The compounds 7,11-bis(4-fluorophenyl)-2,4-dimethyl- 2,4-diazaspiro[5.5] undecane-1,3,5,9-tetraone (3a) and 2,4-dimethyl-7,11-bis (4-(trifluoromethyl)phenyl)-2,4-diazaspiro[5.5]undecane-1,3,5,9-tetraone (3b) were characterized by single-crystal X-ray diffraction, FT-IR and NMR techniques. The optimized geometrical parameters, infrared vibrational frequencies and NMR chemical shifts of the studied compounds have also been calculated using the density functional theory (DFT) method, using Becke-3-Lee-Yang-Parr functional and the 6-311G(d,p) basis set. There is good agreement between the experimentally determined structural parameters, vibrational frequencies and NMR chemical shifts of the studied compounds and those predicted theoretically. The calculated natural atomic charges using NBO method showed higher polarity of 3a compared to 3b.The calculated electronic spectra are also discussed based on the TD-DFT calculations.
    Matched MeSH terms: Thermodynamics
  6. Optimization of methylene blue using Ca(2+) and Zn(2+) bio-polymer hydrogel beads: A comparative study
    Kumar M, Tamilarasan R, Arthanareeswaran G, Ismail AF
    Ecotoxicol Environ Saf, 2015 Nov;121:164-73.
    PMID: 25913699 DOI: 10.1016/j.ecoenv.2015.04.007
    Recently noted that the methylene blue cause severe central nervous system toxicity. It is essential to optimize the methylene blue from aqueous environment. In this study, a comparison of an optimization of methylene blue was investigated by using modified Ca(2+) and Zn(2+) bio-polymer hydrogel beads. A batch mode study was conducted using various parameters like time, dye concentration, bio-polymer dose, pH and process temperature. The isotherms, kinetics, diffusion and thermodynamic studies were performed for feasibility of the optimization process. Freundlich and Langmuir isotherm equations were used for the prediction of isotherm parameters and correlated with dimensionless separation factor (RL). Pseudo-first order and pseudo-second order Lagegren's kinetic equations were used for the correlation of kinetic parameters. Intraparticle diffusion model was employed for diffusion of the optimization process. The Fourier Transform Infrared Spectroscopy (FTIR) shows different absorbent peaks of Ca(2+) and Zn(2+) beads and the morphology of the bio-polymer material analyzed with Scanning Electron Microscope (SEM). The TG & DTA studies show that good thermal stability with less humidity without production of any non-degraded products.
    Matched MeSH terms: Thermodynamics
  7. 3-Iodobenzaldehyde: XRD, FT-IR, Raman and DFT studies
    Kumar CS, Parlak C, Tursun M, Fun HK, Rhyman L, Ramasami P, et al.
    Spectrochim Acta A Mol Biomol Spectrosc, 2015 Jun 15;145:90-7.
    PMID: 25767992 DOI: 10.1016/j.saa.2015.02.079
    The structure of 3-iodobenzaldehyde (3IB) was characterized by FT-IR, Raman and single-crystal X-ray diffraction techniques. The conformational isomers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of 3IB were examined using density functional theory (DFT) method, with the Becke-3-Lee-Yang-Parr (B3LYP) functional and the 6-311+G(3df,p) basis set for all atoms except for iodine. The LANL2DZ effective core basis set was used for iodine. Potential energy distribution (PED) analysis of normal modes was performed to identify characteristic frequencies. 3IB crystallizes in monoclinic space group P21/c with the O-trans form. There is a good agreement between the theoretically predicted structural parameters, and vibrational frequencies and those obtained experimentally. In order to understand halogen effect, 3-halogenobenzaldehyde [XC6H4CHO; X=F, Cl and Br] was also studied theoretically. The free energy difference between the isomers is small but the rotational barrier is about 8kcal/mol. An atypical behavior of fluorine affecting conformational preference is observed.
    Matched MeSH terms: Thermodynamics
  8. Fulltext Iron impregnated activated carbon as an efficient adsorbent for the removal of methylene blue: regeneration and kinetics studies
    Shah I, Adnan R, Wan Ngah WS, Mohamed N
    PLoS One, 2015;10(4):e0122603.
    PMID: 25849291 DOI: 10.1371/journal.pone.0122603
    In this study, iron impregnated activated carbon (FeAC) was synthesized following an oxidation and iron impregnation of activated carbon (AC). Both the AC and FeAC were characterized by pHZPC and FTIR spectroscopy. The removal of Methylene Blue (MB) by AC and FeAC was examined under various experimental conditions. The FeAC showed up to 95% (higher than AC) MB removal in the pH range of 7-10. Although the reaction kinetics was pseudo-second order, the overall rate was controlled by a number of processes such as film diffusion, pore diffusion and intraparticle diffusion. The activation energy values for the MB uptake by AC and FeAC (21.79 and 14.82 kJ/mol, respectively) revealed a physisorption process. In the regeneration study, FeAC has shown consistently ≥ 90% MB removal even up to 10 repeated cycles. The reusable characteristic of the spent FeAC improved the practical use of activated carbon and can be a breakthrough for continuous flow system applications where it can work effectively without any significant reduction in its performance.
    Matched MeSH terms: Thermodynamics
  9. Fulltext QOS-aware error recovery in wireless body sensor networks using adaptive network coding
    Razzaque MA, Javadi SS, Coulibaly Y, Hira MT
    Sensors (Basel), 2014 Dec 29;15(1):440-64.
    PMID: 25551485 DOI: 10.3390/s150100440
    Wireless body sensor networks (WBSNs) for healthcare and medical applications are real-time and life-critical infrastructures, which require a strict guarantee of quality of service (QoS), in terms of latency, error rate and reliability. Considering the criticality of healthcare and medical applications, WBSNs need to fulfill users/applications and the corresponding network's QoS requirements. For instance, for a real-time application to support on-time data delivery, a WBSN needs to guarantee a constrained delay at the network level. A network coding-based error recovery mechanism is an emerging mechanism that can be used in these systems to support QoS at very low energy, memory and hardware cost. However, in dynamic network environments and user requirements, the original non-adaptive version of network coding fails to support some of the network and user QoS requirements. This work explores the QoS requirements of WBSNs in both perspectives of QoS. Based on these requirements, this paper proposes an adaptive network coding-based, QoS-aware error recovery mechanism for WBSNs. It utilizes network-level and user-/application-level information to make it adaptive in both contexts. Thus, it provides improved QoS support adaptively in terms of reliability, energy efficiency and delay. Simulation results show the potential of the proposed mechanism in terms of adaptability, reliability, real-time data delivery and network lifetime compared to its counterparts.
    Matched MeSH terms: Thermodynamics
  10. Thermokinetic comparison of trypan blue decolorization by free laccase and fungal biomass
    Razak NN, Annuar MS
    Appl Biochem Biotechnol, 2014 Mar;172(6):2932-44.
    PMID: 24464534 DOI: 10.1007/s12010-014-0731-7
    Free laccase and fungal biomass from white-rot fungi were compared in the thermokinetics study of the laccase-catalyzed decolorization of an azo dye, i.e., Trypan Blue. The decolorization in both systems followed a first-order kinetics. The apparent first-order rate constant, k1', value increases with temperature. Apparent activation energy of decolorization was similar for both systems at ∼ 22 kJ mol(-1), while energy for laccase inactivation was 18 kJ mol(-1). Although both systems were endothermic, fungal biomass showed higher enthalpy, entropy, and Gibbs free energy changes for the decolorization compared to free laccase. On the other hand, free laccase showed reaction spontaneity over a wider range of temperature (ΔT = 40 K) as opposed to fungal biomass (ΔT = 15 K). Comparison of entropy change (ΔS) values indicated metabolism of the dye by the biomass.
    Matched MeSH terms: Thermodynamics
  11. Synthesis, molecular structure, FT-IR and XRD investigations of 2-(4-chlorophenyl)-2-oxoethyl 2-chlorobenzoate: a comparative DFT study
    Chidan Kumar CS, Fun HK, Tursun M, Ooi CW, Chandraju S, Quah CK, et al.
    Spectrochim Acta A Mol Biomol Spectrosc, 2014 Apr 24;124:595-602.
    PMID: 24509537 DOI: 10.1016/j.saa.2014.01.063
    2-(4-Chlorophenyl)-2-oxoethyl 2-chlorobenzoate has been synthesized, its structural and vibrational properties have been reported using FT-IR and single-crystal X-ray diffraction (XRD) studies. The conformational analysis, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the synthesized compound (C15H10Cl2O3) have been examined by means of Becke-3-Lee-Yang-Parr (B3LYP) density functional theory (DFT) method together with 6-31++G(d,p) basis set. Furthermore, reliable conformational investigation and vibrational assignments have been made by the potential energy surface (PES) and potential energy distribution (PED) analyses, respectively. Calculations are performed with two possible conformations. The title compound crystallizes in orthorhombic space group Pbca with the unit cell dimensions a=12.312(5) Å, b=8.103(3) Å, c=27.565(11) Å, V=2750.0(19) Å(3). B3LYP method provides satisfactory evidence for the prediction of vibrational wavenumbers and structural parameters.
    Matched MeSH terms: Thermodynamics
  12. A DFT analyses for molecular structure, electronic state and spectroscopic property of a dithiolene tungsten carbonyl complex
    Arifin K, Daud WR, Kassim MB
    Spectrochim Acta A Mol Biomol Spectrosc, 2014 Apr 24;124:375-82.
    PMID: 24508875 DOI: 10.1016/j.saa.2013.12.107
    Bis(dithiolene) tungsten carbonyl complex, W(S2C2Ph2)2(CO)2 was successfully synthesized and the structure, frontier molecular orbital and optical properties of the complex were investigated theoretically using density functional theory calculations. The investigation started with a molecular structure construction, followed by an optimization of the structural geometry using generalized-gradient approximation (GGA) in a double numeric plus polarization (DNP) basis set at three different functional calculation approaches. Vibrational frequency analysis was used to confirm the optimized geometry of two possible conformations of [W(S2C2Ph2)2(CO)2], which showed distorted octahedral geometry. Electronic structure and optical characterization were done on the ground states. Metal to ligand and ligand to metal charge transfer were dominant in this system.
    Matched MeSH terms: Thermodynamics
  13. Antioxidant properties of phenolic Schiff bases: structure-activity relationship and mechanism of action
    Anouar el H, Raweh S, Bayach I, Taha M, Baharudin MS, Di Meo F, et al.
    J Comput Aided Mol Des, 2013 Nov;27(11):951-64.
    PMID: 24243063 DOI: 10.1007/s10822-013-9692-0
    Phenolic Schiff bases are known for their diverse biological activities and ability to scavenge free radicals. To elucidate (1) the structure-antioxidant activity relationship of a series of thirty synthetic derivatives of 2-methoxybezohydrazide phenolic Schiff bases and (2) to determine the major mechanism involved in free radical scavenging, we used density functional theory calculations (B3P86/6-31+(d,p)) within polarizable continuum model. The results showed the importance of the bond dissociation enthalpies (BDEs) related to the first and second (BDEd) hydrogen atom transfer (intrinsic parameters) for rationalizing the antioxidant activity. In addition to the number of OH groups, the presence of a bromine substituent plays an interesting role in modulating the antioxidant activity. Theoretical thermodynamic and kinetic studies demonstrated that the free radical scavenging by these Schiff bases mainly proceeds through proton-coupled electron transfer rather than sequential proton loss electron transfer, the latter mechanism being only feasible at relatively high pH.
    Matched MeSH terms: Thermodynamics
  14. Biosorption of As (III) by non-living biomass of an arsenic-hypertolerant Bacillus cereus strain SZ2 isolated from a gold mining environment: equilibrium and kinetic study
    Mohd Bahari Z, Ali Hamood Altowayti W, Ibrahim Z, Jaafar J, Shahir S
    Appl Biochem Biotechnol, 2013 Dec;171(8):2247-61.
    PMID: 24037600 DOI: 10.1007/s12010-013-0490-x
    The ability of non-living biomass of an arsenic-hypertolerant Bacillus cereus strain SZ2 isolated from a gold mining environment to adsorb As (III) from aqueous solution in batch experiments was investigated as a function of contact time, initial As (III) concentration, pH, temperature and biomass dosage. Langmuir model fitted the equilibrium data better in comparison to Freundlich isotherm. The maximum biosorption capacity of the sorbent, as obtained from the Langmuir isotherm, was 153.41 mg/g. The sorption kinetic of As (III) biosorption followed well the pseudo-second-order rate equation. The Fourier transform infrared spectroscopy analysis indicated the involvement of hydroxyl, amide and amine groups in As (III) biosorption process. Field emission scanning electron microscopy-energy dispersive X-ray analysis of the non-living B. cereus SZ2 biomass demonstrated distinct cell morphological changes with significant amounts of As adsorbed onto the cells compared to non-treated cells. Desorption of 94 % As (III) was achieved at acidic pH 1 showing the capability of non-living biomass B. cereus SZ2 as potential biosorbent in removal of As (III) from arsenic-contaminated mining effluent.
    Matched MeSH terms: Thermodynamics
  15. Development of magnetic graphene oxide adsorbent for the removal and preconcentration of As(III) and As(V) species from environmental water samples
    Rashidi Nodeh H, Wan Ibrahim WA, Ali I, Sanagi MM
    Environ Sci Pollut Res Int, 2016 May;23(10):9759-73.
    PMID: 26850098 DOI: 10.1007/s11356-016-6137-z
    New-generation adsorbent, Fe3O4@SiO2/GO, was developed by modification of graphene oxide (GO) with silica-coated (SiO2) magnetic nanoparticles (Fe3O4). The synthesized adsorbent was characterized using Fourier transform infrared spectroscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, and field emission scanning electron microscopy. The developed adsorbent was used for the removal and simultaneous preconcentration of As(III) and As(V) from environmental waters prior to ICP-MS analysis. Fe3O4@SiO2/GO provided high adsorption capacities, i.e., 7.51 and 11.46 mg g(-1) for As(III) and As(V), respectively, at pH 4.0. Adsorption isotherm, kinetic, and thermodynamic were investigated for As(III) and As(V) adsorption. Preconcentration of As(III) and As(V) were studied using magnetic solid-phase extraction (MSPE) method at pH 9.0 as the adsorbent showed selective adsorption for As(III) only in pH range 7-10. MSPE using Fe3O4@SiO2/GO was developed with good linearities (0.05-2.0 ng mL(-1)) and high coefficient of determination (R (2) = 0.9992 and 0.9985) for As(III) and As(V), respectively. The limits of detection (LODs) (3× SD/m, n = 3) obtained were 7.9 pg mL(-1) for As(III) and 28.0 pg mL(-1) for As(V). The LOD obtained is 357-1265× lower than the WHO maximum permissible limit of 10.0 ng mL(-1). The developed MSPE method showed good relative recoveries (72.55-109.71 %) and good RSDs (0.1-4.3 %, n = 3) for spring water, lake, river, and tap water samples. The new-generation adsorbent can be used for the removal and simultaneous preconcentration of As(III) and As(V) from water samples successfully. The adsorbent removal for As(III) is better than As(V).
    Matched MeSH terms: Thermodynamics
  16. Preparation and characterization of irradiated carboxymethyl sago starch-acid hydrogel and its application as metal scavenger in aqueous solution
    Basri SN, Zainuddin N, Hashim K, Yusof NA
    Carbohydr Polym, 2016 Mar 15;138:34-40.
    PMID: 26794735 DOI: 10.1016/j.carbpol.2015.11.028
    Carboxymethyl sago starch-acid hydrogel was prepared via irradiation technique to remove divalent metal ions (Pb, Cu and Cd) from their aqueous solution. The hydrogel was characterized by using Fourier Transform Infrared (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The removal of these metal ions was analyzed by using inductively coupled plasma-optic emission spectra (ICP-OES) to study the amount of metal uptake by the hydrogel. Parameters of study include effect of pH, amount of sample, contact time, initial concentration of metal solution and reaction temperature. FTIR spectroscopy shows the CMSS hydrogel absorption peaks at 1741cm(-1), 1605cm(-1) and 1430cm(-1) which indicates the substitution of carboxymethyl group of modified sago starch. The degradation temperature of CMSS hydrogel is higher compared to CMSS due to the crosslinking by electron beam radiation and formed a porous hydrogel. From the data obtained, about 93.5%, 88.4% and 85.5% of Pb, Cu and Cd ions has been respectively removed from their solution under optimum condition.
    Matched MeSH terms: Thermodynamics
  17. Effect of hydrolysed cellulose nanowhiskers on properties of montmorillonite/polylactic acid nanocomposites
    Arjmandi R, Hassan A, Haafiz MK, Zakaria Z, Islam MS
    Int J Biol Macromol, 2016 Jan;82:998-1010.
    PMID: 26592699 DOI: 10.1016/j.ijbiomac.2015.11.028
    Polylactic acid (PLA) nanocomposites reinforced with hybrid montmorillonite/cellulose nanowhiskers [MMT/CNW(SO4)] were prepared by solution casting. The CNW(SO4) nanofiller was first isolated from microcrystalline cellulose using acid hydrolysis treatment. PLA/MMT/CNW(SO4) hybrid nanocomposites were prepared by the addition of various amounts of CNW(SO4) [1-9 parts per hundred parts of polymer (phr)] into PLA/MMT nanocomposite at 5 phr MMT content, based on highest tensile strength values as reported previously. The biodegradability, thermal, tensile, morphological, water absorption and transparency properties of PLA/MMT/CNW(SO4) hybrid nanocomposites were investigated. The Biodegradability, thermal stability and crystallinity of hybrid nanocomposites increased compared to PLA/MMT nanocomposite and neat PLA. The highest tensile strength of hybrid nanocomposites was obtained by incorporating 1 phr CNW(SO4) [∼ 36 MPa]. Interestingly, the ductility of hybrid nanocomposites increased significantly by 87% at this formulation. The Young's modulus increased linearly with increasing CNW(SO4) content. This is due to the relatively good dispersion of nanofillers in the hybrid nanocomposites, as revealed by transmission electron microscopy. Fourier transform infrared spectroscopy indicated the formation of some polar interactions. In addition, water resistance of the hybrid nanocomposites improved and the visual transparency of neat PLA film did not affect by addition of CNW(SO4).
    Matched MeSH terms: Thermodynamics
  18. Fulltext Enhanced Recyclable Magnetized Palm Shell Waste-Based Powdered Activated Carbon for the Removal of Ibuprofen: Insights for Kinetics and Mechanisms
    Wong KT, Yoon Y, Jang M
    PLoS One, 2015;10(10):e0141013.
    PMID: 26496196 DOI: 10.1371/journal.pone.0141013
    A novel preparation method of magnetized palm shell waste-based powdered activated carbon (MPPAC, avg. size 112 μm) was developed. The prepared MPPAC was assessed by several physicochemical analyses, and batch tests were performed for ibuprofen (IBP) removal. Field emission scanning electron microscopy (FESEM) and N2 gas isotherms revealed that magnetite and maghemite were homogeneous and deposited mostly on the surface of PPAC without a significant clogging effect on the micropores. Isotherm results showed that 3.8% Fe (w/w) impregnated PPAC [MPPAC-Fe(3.8%)] had about 2.2-fold higher maximum sorption capacity (157.3 mg g-1) and a 2.5-fold higher sorption density (0.23 mg m-2) than pristine PPAC. Both Fourier-transform infrared spectroscopy (FTIR) and isotherm data indicated that the high sorption capacity and density of IBP by MPPAC was primarily attributable to donor-acceptor complexes with the C = O group and dispersive π-π interactions with the carbon surface. Based on kinetic and repeated adsorption tests, pore diffusion was the rate-limiting step, and MPPAC-Fe(3.8%) had about 1.9~2.8- and 9.1~15.8-fold higher rate constants than MPPAC-Fe(8.6%) and palm shell-waste granular activated carbon (PGAC, avg. size 621 μm), respectively. MPPAC showed almost eight fold greater re-adsorption capacity than PPAC due to a thermal catalytic effect of magnetite/maghemite.
    Matched MeSH terms: Thermodynamics
  19. Fulltext Involvement of Lipocalin-like CghA in Decalin-Forming Stereoselective Intramolecular [4+2] Cycloaddition
    Sato M, Yagishita F, Mino T, Uchiyama N, Patel A, Chooi YH, et al.
    Chembiochem, 2015 Nov 2;16(16):2294-8.
    PMID: 26360642 DOI: 10.1002/cbic.201500386
    Understanding enzymatic Diels-Alder (DA) reactions that can form complex natural product scaffolds is of considerable interest. Sch 210972 1, a potential anti-HIV fungal natural product, contains a decalin core that is proposed to form through a DA reaction. We identified the gene cluster responsible for the biosynthesis of 1 and heterologously reconstituted the biosynthetic pathway in Aspergillus nidulans to characterize the enzymes involved. Most notably, deletion of cghA resulted in a loss of stereoselective decalin core formation, yielding both an endo (1) and a diastereomeric exo adduct of the proposed DA reaction. Complementation with cghA restored the sole formation of 1. Density functional theory computation of the proposed DA reaction provided a plausible explanation of the observed pattern of product formation. Based on our study, we propose that lipocalin-like CghA is responsible for the stereoselective intramolecular [4+2] cycloaddition that forms the decalin core of 1.
    Matched MeSH terms: Thermodynamics
  20. Removal of humic and tannic acids by adsorption-coagulation combined systems with activated biochar
    Jung C, Phal N, Oh J, Chu KH, Jang M, Yoon Y
    J Hazard Mater, 2015 Dec 30;300:808-814.
    PMID: 26340547 DOI: 10.1016/j.jhazmat.2015.08.025
    Despite recent interest in transforming biomass into bio-oil and syngas, there is inadequate information on the compatibility of byproducts (e.g., biochar) with agriculture and water purification infrastructures. A pyrolysis at 300°C yields efficient production of biochar, and its physicochemical properties can be improved by chemical activation, resulting in a suitable adsorbent for the removal of natural organic matter (NOM), including hydrophobic and hydrophilic substances, such as humic acids (HA) and tannic acids (TA), respectively. In this study, the adsorption affinities of different HA and TA combinations in NOM solutions were evaluated, and higher adsorption affinity of TA onto activated biochar (AB) produced in the laboratory was observed due to its superior chemisorption tendencies and size-exclusion effects compared with that of HA, whereas hydrophobic interactions between adsorbent and adsorbate were deficient. Assessment of the AB role in an adsorption-coagulation hybrid system as nuclei for coagulation in the presence of aluminum sulfate (alum) showed a synergistic effect in a HA-dominated NOM solution. An AB-alum hybrid system with a high proportion of HA in the NOM solution may be applicable as an end-of-pipe solution.
    Matched MeSH terms: Thermodynamics
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