An insight into structure and stability of DNA in ionic liquids from molecular dynamics simulation and experimental studies

Molecular dynamics simulation and biophysical analysis were employed to reveal the characteristics and the influence of ionic liquids (ILs) on the structural properties of DNA. Both computational and experimental evidence indicate that DNA retains its native B-conformation in ILs. Simulation data show that the hydration shells around the DNA phosphate group were the main criteria for DNA stabilization in this ionic media. Stronger hydration shells reduce the binding ability of ILs' cations to the DNA phosphate group, thus destabilizing the DNA. The simulation results also indicated that the DNA structure maintains its duplex conformation when solvated by ILs at different temperatures up to 373.15 K. The result further suggests that the thermal stability of DNA at high temperatures is related to the solvent thermodynamics, especially entropy and enthalpy of water. All the molecular simulation results were consistent with the experimental findings. The understanding of the properties of IL–DNA could be used as a basis for future development of specific ILs for nucleic acid technology

Optimizations and artificial neural network validation studies for naphthalene and phenanthrene adsorption onto NH2-UiO-66(Zr) metal-organic framework

Adsorptive removal of naphthalene (NAP) and phenanthrene (PHE) was reported using NH2-UiO-66(Zr) metal-organic frameworks. The process was optimized by response surface methodology (RSM) using central composite design (CCD). The fitting of the model was described by the analysis of variance (ANOVA) with significant Fischer test (F-value) of 85.46 and 30.56 for NAP and PHE, respectively. Validation of the adsorption process was performed by artificial neural network (ANN), achieving good prediction performance at node 6 for both NAP and PHE with good agreement between the actual and predicted ANN adsorption efficiencies. The good reusability of the MOF was discovered for 7 consecutive cycles and achieving adsorption efficiency of 89.1 and 87.2% for the NAP and PHE, respectively. The performance of the MOF in a binary adsorption system was also analyzed and the adsorption efficiency achieved was 97.7 and 96.9% for the NAP and PHE, respectively

Design and molecular modelling of phenolic-based protic ionic liquids

Five new phenolic-based protic ionic liquids (PILs) were successfully synthesised via neutralisation reaction. The synthesised PILs were characterised using spectral analyses such as 1H NMR, FTIR and thermogravimetric analysis. The effects of alkyl chain length and temperature towards the physical properties of the PILs were comprehensively investigated as well. The alkyl chain length of the cation and temperature significantly influenced both the density and viscosity of the PILs. As the alkyl chain length elongated from 2-hydroxy-N-methylethanaminium salicylate (2HMES) to 2-hydroxy-N-propylethanaminium salicylate (2HBES) the density decreased from 1158.40 to 1110.60 kg.m−3 (at 293.15 K) and viscosity increased from 541.69 to 1383.00 mPa.s (at 293.15 K). Moreover, the density and viscosity of the PILs declined steadily as the temperature elevated from 293.15 to 363.15 K. Furthermore, the structural conformation of the PILs from the spectral analyses was further validated by the density function theory (DFT) calculation. Based on the optimised structure from the computational study, the most favourable interaction occurred between the –NH and –COO groups of the ion-pairs resulted from the transfer of hydrogen atom from acid to base

Modeling to enhance attached microalgal biomass growth onto fluidized beds packed in nutrients-rich wastewater whilst simultaneously biofixing CO2 into lipid for biodiesel production

[[abstract]]One way to reconcile an issue associating with the harvesting of microalgal biomass is via the application of attached growth cultivation mode, whereby the mature microalgal biomass can be facilely harvested from the support material. Accordingly, the objectives of present works were to model the attached growth of Chlorella vulgaris onto polyurethane foam support material in a fluidized bed bioreactor while simultaneously bioremediating real nutrients-rich wastewater and biofixing CO2 for biodiesel production. The mathematical models accounting the impact of various interactions between light intensities and CO2 concentrations in culture medium on growing attached microalgal biomass were initially improved. The successful practicality of models was confirmed from the analysis of statistical accuracy while predicting the growth of attached microalgal biomass in real nutrients-rich wastewater. When the microalgal growth reached the stationary growth phase, all the nutrients (nitrogen and phosphorous sources of compounds) were completed impoverished, accentuating the bioremediation potentiality in satisfying the effluent discharged requirements. Subsequently, the modeling of microalgal CO2 biofixation also unveiled that the highest CO2 biofixation rate was transpiring in parallel with the growth rate of attached microalgal biomass during the exponential growth phase. Upon the harvesting, the neutral lipid from mature attached microalgal biomass was found to contain 97.7% (by wt. of lipid) of fatty acid methyl esters (FAMEs) mixture, heralding the biodiesel purity. Assessment of biodiesel quality showed a balance composition among the saturated, monounsaturated and polyunsaturated FAMEs mixture with high in C16 and C18 FAME species for the materialization of efficient combustion.[[notice]]補正完

Arsenic adsorption mechanism on palm oil fuel ash (POFA) powder suspension

The contribution of palm oil fuel ash (POFA), an agricultural waste as a low cost adsorbent for the removal of arsenite (As(III)) and arsenate (As(V)) was explored. Investigation on the adsorbency characteristics of POFA suspension revealed that the surface area, particle size, composition, and crystallinity of the SiO2 rich mullite structure were the crucial factors in ensuring a high adsorption capacity of the ions. Maximum adsorption capacities of As(III) and As(V) at 91.2 and 99.4 mg g(-1), respectively, were obtained when POFA of 30 mu m particle size was employed at pH 3 with the highest calcination temperature at 1150 degrees C. An optimum dosage of 1.0 g of dried POFA powder successfully removed 48.7% and 50.2% of As(III) and As(V), respectively. Molecular modeling using the density functional theory consequently identified the energy for the proposed reaction routes between the SiO- and As+ species. The high stability of the POFA suspension in water in conjunction with good adsorption capacity of As(III) and As(V) seen in this study, thus envisages its feasibility as a potential alternative absorbent for the remediation of water polluted with heavy metals