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.
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.
The molecular structure of a new Schiff base, 2-[4-hydroxy benzylidene]-amino naphthalene (HBAN) has been examined by HF and B3LYP/6-311++G(d,p) calculations. The X-ray structure was determined in order to establish the conformation of the molecule. The compound, C17H13NO, crystallizes in the orthorhombic, P212121 space group with the cell dimension, a=6.2867(2), b=10.2108(3), c=19.2950(6) Å, α=β=γ=90° and z=4. The asymmetric unit contains a molecule of a Schiff base. A strong intermolecular O-H⋯N and a weak C-H⋯O hydrogen bonds stabilized the crystal structure. The vibrational spectra of HBAN have been calculated using density functional theoretical computation and compared with the experimental. The study is extended to the HOMO-LUMO analysis to calculate the energy gap (Δ), Ionization potential (I), Electron Affinity (A), Global Hardness (η), Chemical Potential (μ) and Global Electrophilicity (w). The calculated HOMO and LUMO energy reveals that the charge transfer occurs within the molecule.
The adsorption from aqueous solution of imidazolium, pyrrolidinium and pyridinium based bromide ionic liquids (ILs) having different alkyl chain lengths was investigated on two types of microporous activated carbons: a fabric and a granulated one, well characterized in terms of surface chemistry by "Boehm" titrations and pH of point of zero charge measurements and of porosity by N2 adsorption at 77 K and CO2 adsorption at 273 K. The influence of cation type, alkyl chain length and adsorbate size on the adsorption properties was analyzed by studying kinetics and isotherms of eight different ILs using conductivity measurements. Equilibrium studies were carried out at different temperatures in the range [25-55 °C]. The incorporation of ILs on the AC porosity was studied by N2 adsorption-desorption measurements at 77 K. The experimental adsorption isotherms data showed a good correlation with the Langmuir model. Thermodynamic studies indicated that the adsorption of ILs onto activated carbons was an exothermic process, and that the removal efficiency increased with increase in alkyl chain length, due to the increase in hydrophobicity of long chain ILs cations determined with the evolution of the calculated octanol-water constant (Kow). The negative values of free energies indicated that adsorption of ILs with long chain lengths having hydrophobic cations was more spontaneous at the investigated temperatures.
The purpose of exploring protein interactions between human adenovirus and heat shock protein 70 is to exploit a potentially synergistic interaction to enhance anti-tumoral efficacy and decrease toxicity in cancer treatment. However, the protein interaction of Hsp70 with E1A32 kDa of human adenovirus serotype 5 remains to be elucidated. In this study, two residues of ATPase domain of human heat shock 70 kDa protein 1 (PDB: 1 HJO) were mutated. 3D mutant models (K71L and T204V) using PyMol software were then constructed. The structures were evaluated by PROCHECK, ProQ, ERRAT, Verify 3D and ProSA modules. All evidence suggests that all protein models are acceptable and of good quality. The E1A32 kDa motif was retrieved from UniProt (P03255), as well as subjected to docking interaction with NBD, K71L and T204V, using the Autodock 4.2 program. The best lowest binding energy value of -9.09 kcal/mol was selected for novel T204V. Moreover, the protein-ligand complex structures were validated by RMSD, RMSF, hydrogen bonds and salt bridge analysis. This revealed that the T204V-E1A32 kDa motif complex was the most stable among all three complex structures. This study provides information about the interaction between Hsp70 and the E1A32 kDa motif, which emphasizes future perspectives to design rational drugs and vaccines in cancer therapy.
This work describes methacrylic acid functionalized β-cyclodextrin (MAA-βCD) as a novel functional monomer in the preparation of molecular imprinted polymer (MIP MAA-βCD) for the selective removal of 2,4-dichlorophenol (2,4-DCP). The polymer was characterized using Fourier Transform Infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) and Field Emission Scanning Electron Microscopy (FESEM) techniques. The influence of parameters such as solution pH, contact time, temperature and initial concentrations towards removal of 2,4-DCP using MIP MAA-βCD have been evaluated. The imprinted material shows fast kinetics and the optimum pH for removal of 2,4-DCP is pH 7. Compared with the corresponding non-imprinted polymer (NIP MAA-βCD), the MIP MAA-βCD exhibited higher adsorption capacity and outstanding selectivity towards 2,4-DCP. Freundlich isotherm best fitted the adsorption equilibrium data of MIP MAA-βCD and the kinetics followed a pseudo-second-order model. The calculated thermodynamic parameters showed that adsorption of 2,4-DCP was spontaneous and exothermic under the examined conditions.
Hispidin oligomers are styrylpyrone pigments isolated from the medicinal fungi Inonotus xeranticus and Phellinus linteus. They exhibit diverse biological activities and strong free radical scavenging activity. To rationalize the antioxidant activity of a series of four hispidin oligomers and determine the favored mechanism involved in free radical scavenging, DFT calculations were carried out at the B3P86/6-31+G (d, p) level of theory in gas and solvent. The results showed that bond dissociation enthalpies of OH groups of hispidin oligomers (ArOH) and spin density delocalization of related radicals (ArO•) are the appropriate parameters to clarify the differences between the observed antioxidant activities for the four oligomers. The effect of the number of hydroxyl groups and presence of a catechol moiety conjugated to a double bond on the antioxidant activity were determined. Thermodynamic and kinetic studies showed that the PC-ET mechanism is the main mechanism involved in free radical scavenging. The spin density distribution over phenoxyl radicals allows a better understanding of the hispidin oligomers formation.
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.
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.
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.
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.
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.
Density functional theory calculations on two glycosides, namely, n-octyl-β-D-glucopyranoside (C(8)O-β-Glc) and n-octyl-β-D-galactopyranoside (C(8)O-β-Gal) were performed for geometry optimization at the B3LYP/6-31G level. Both molecules are stereoisomers (epimers) differing only in the orientation of the hydroxyl group at the C4 position. Thus it is interesting to investigate electronically the effect of the direction (axial/equatorial) of the hydroxyl group at the C4 position. The structure parameters of X-H∙∙∙Y intramolecular hydrogen bonds were analyzed, while the nature of these bonds and the intramolecular interactions were considered using the atoms in molecules (AIM) approach. Natural bond orbital analysis (NBO) was used to determine bond orders, charge and lone pair electrons on each atom and effective non-bonding interactions. We have also reported electronic energy and dipole moment in gas and solution phases. Further, the electronic properties such as the highest occupied molecular orbital, lowest unoccupied molecular orbital, ionization energy, electron affinity, electronic chemical potential, chemical hardness, softness and electrophilicity index, are also presented here for both C(8)O-β-Glc and C(8)O-β-Gal. These results show that, while C(8)O-β-Glc possess- only one hydrogen bond, C(8)O-β-Gal has two intramolecular hydrogen bonds, which further confirms the anomalous stability of the latter in self-assembly phenomena.
Finding a proper transition structure for the peptide bond formation process can lead one to a better understanding of the role of ribosome in catalyzing this reaction. Using computer simulations, we performed the potential energy surface scan on the ester bond dissociation of P-site aminoacyl-tRNA and the peptide bond formation of P-site and A-site amino acids. The full fragments of initiator tRNA(i)(met) and elongator tRNA(phe) are attached to both cognate and non-cognate amino acids as the P-site substrate. The A-site amino acid for all four calculations is methionine. We used ONIOM calculations to reduce the computational cost. Our study illustrates the reduced rate of peptide bond formation for misacylated tRNA(i)(met) in the absence of ribosomal bases. The misacylated elongator tRNA(phe), however, did not show any difference in its PES compared with that for the phe-tRNA(phe). This demonstrates the structural specification of initiator tRNA(i)(met) for the amino acids side chain.
The potential of base treated Shorea dasyphylla (BTSD) sawdust for Acid Blue 25 (AB 25) adsorption was investigated in a batch adsorption process. Various physiochemical parameters such as pH, stirring rate, dosage, concentration, contact time and temperature were studied. The adsorbent was characterized with Fourier transform infrared spectrophotometer, scanning electron microscope and Brunauer, Emmett and Teller analysis. The optimum conditions for AB 25 adsorption were pH 2, stirring rate 500 r/min, adsorbent dosage 0.10 g and contact time 60 min. The pseudo second-order model showed the best conformity to the kinetic data. The equilibrium adsorption of AB 25 was described by Freundlich and Langmuir, with the latter found to agree well with the isotherm model. The maximum monolayer adsorption capacity of BTSD was 24.39 mg/g at 300 K, estimated from the Langmuir model. Thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were determined. It was found that AB 25 adsorption was spontaneous and exothermic.
Interaction of flavokawain B (FB), a multitherapeutic flavonoid from Alpinia mutica with the major transport protein, human serum albumin (HSA), was investigated using different spectroscopic probes, i.e., intrinsic, synchronous, and three-dimensional (3-D) fluorescence, circular dichroism (CD), and molecular modeling studies. Values of binding parameters for FB-HSA interaction in terms of binding constant and stoichiometry of binding were determined from the fluorescence quench titration and were found to be 6.88 × 10(4) M(-1) and 1.0 mol of FB bound per mole of protein, respectively, at 25 °C. Thermodynamic analysis of the binding data obtained at different temperatures showed that the binding process was primarily mediated by hydrophobic interactions and hydrogen bonding, as the values of the enthalpy change (ΔH) and the entropy change (ΔS) were found to be -6.87 kJ mol(-1) and 69.50 J mol(-1) K(-1), respectively. FB binding to HSA led to both secondary and tertiary structural alterations in the protein as revealed by intrinsic, synchronous, and 3-D fluorescence results. Increased thermal stability of HSA in the presence of FB was also evident from the far-UV CD spectral results. The distance between the bound ligand and Trp-214 of HSA was determined as 3.03 nm based on the Förster resonance energy transfer mechanism. Displacement experiments using bilirubin and warfarin coupled with molecular modeling studies assigned the binding site of FB on HSA at domain IIA, i.e., Sudlow's site I.
This paper describes the sorption of Pb(ll) from aqueous solution. Oil palm empty fruit bunch (OPEFB) fiber was first grafted with poly(methylacrylate) and then treated with hydroxylammonium chloride in alkaline medium to produce hydroxamic acid (PHA) grafted OPEFB. Sorption of Pb(ll) by PHA-OPEFB was maximum at pH 5. The sorption followed the Langmuir model with maximum capacityof 125.0 mg g-1 at 25 degrees C. The sorption process was exothermic, as shown by the negative value of enthalpy change, Delta H0. The free energy change (DeltaG0) for the sorption was negative, showing that the sorption process was spontaneous. A kinetic study showed that the Pb(ll) sorption followed a second order kinetic model.
For the coherent understanding of heat acclimatization in tropical natives, we compared ethnic differences between tropical and temperate natives during resting, passive and active heating conditions. Experimental protocols included: (1) a resting condition (an air temperature of 28°C with 50% RH), (2) a passive heating condition (28°C with 50% RH; leg immersion in a hot tub at a water temperature of 42°C), and (3) an active heating condition (32°C with 70% RH; a bicycle exercise). Morphologically and physically matched tropical natives (ten Malaysian males, MY) and temperate natives (ten Japanese males, JP) participated in all three trials. The results saw that: tropical natives had a higher resting rectal temperature and lower hand and foot temperatures at rest, smaller rise of rectal temperature and greater temperature rise in bodily extremities, and a lower sensation of thirst during passive and active heating than the matched temperate natives. It is suggested that tropical natives' homeostasis during heating is effectively controlled with the improved stability in internal body temperature and the increased capability of vascular circulation in extremities, with a lower thirst sensation. The enhanced stability of internal body temperature and the extended thermoregulatory capability of vascular circulation in the extremities of tropical natives can be interpreted as an interactive change to accomplish a thermal dynamic equilibrium in hot environments. These heat adaptive traits were explained by Wilder's law of initial value and Werner's process and controller adaptation model.
Lipase-catalyzed synthesis of 6-O-glucosyldecanoate from d-glucose and decanoic acid was performed in dimethyl sulfoxide (DMSO), a mixture of DMSO and tert-butanol and tert-butanol alone with a decreasing order of polarity. The highest conversion yield (> 65%) of decanoic acid was obtained in the blended solvent of intermediate polarity mainly because it could dissolve relatively large amounts of both the reactants. The reaction obeyed Michaelis-Menten type of kinetics. The affinity of the enzyme towards the limiting substrate (decanoic acid) was not affected by the polarity of the solvent, but increased significantly with temperature. The esterification reaction was endothermic with activation energy in the range of 60-67 kJ mol⁻¹. Based on the Gibbs energy values, in the solvent blend of DMSO and tert-butanol the position of the equilibrium was shifted more towards the products compared to the position in pure solvents. Monoester of glucose was the main product of the reaction.
In this study, calcined Lapindo volcanic mud (LVM) was used as an adsorbent to remove an anionic dye, methyl orange (MO), from an aqueous solution by the batch adsorption technique. Various conditions were evaluated, including initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature. The adsorption kinetics and equilibrium isotherms of the LVM were studied using pseudo-first-order and -second-order kinetic equations, as well as the Freundlich and Langmuir models. The experimental data obtained with LVM fits best to the Langmuir isotherm model and exhibited a maximum adsorption capacity (q(max)) of 333.3 mg g(-1); the data followed the second-order equation. The intraparticle diffusion studies revealed that the adsorption rates were not controlled only by the diffusion step. The thermodynamic parameters, such as the changes in enthalpy, entropy, and Gibbs free energy, showed that the adsorption is endothermic, random and spontaneous at high temperature. The results indicate that LVM adsorbs MO efficiently and could be utilized as a low-cost alternative adsorbent for the removal of anionic dyes in wastewater treatment.