Pisanu Toochinda

CO2 capture using fly ash from coal fired power plant and applications of CO2-captured fly ash as a mineral admixture for concrete.

The utilization of fly ash as a solid sorbent material for CO2 capture via surface adsorption and carbonation reaction was evaluated as an economically feasible CO2 reduction technique. The results show that fly ash from a coal fired power plant can capture CO2 up to 304.7 μmol/g fly ash, consisting of 2.9 and 301.8 μmol/g fly ash via adsorption and carbonation, respectively. The CO2 adsorption conditions (temperature, pressure, and moisture) can affect CO2 capture performance of fly ash. The carbonation of CO2 with free CaO in fly ashes was evaluated and the results indicated that the reaction consumed most of free CaO in fly ash. The fly ashes after CO2 capture were further used for application as a mineral admixture for concrete. Properties such as water requirement, compressive strength, autoclave expansion, and carbonation depth of mortar and paste specimens using fly ash before and after CO2 capture were tested and compared with material standards. The results show that the expansion of mortar specimens using fly ash after CO2 capture was greatly reduced due to the reduction of free CaO content in the fly ash compared to the expansion of specimens using fresh fly ash. There were no significant differences in the water requirement and compressive strength of specimens using fly ash, before and after CO2 capture process. The results from this study can lead to an alternative CO2 capture technique with doubtless utilization of fly ash after CO2 capture as a mineral admixture for concrete.

Molecular dynamics simulations of UC781-cyclodextrins inclusion complexes in aqueous solution.

The inclusion complexes of highly potent anti-HIV agent, UC781, with β-cyclodextrin (βCD), 2,6-dimethyl-β-cyclodextrin (MβCD), and 2-hydroxypropyl-β-cyclodextrin (HPβCD) in aqueous solution were investigated by molecular dynamics simulations. Simulations show that the phenyl ring of UC781 is trapped inside CD cavities, while the NH group of UC781 interacts with secondary hydroxyl groups at the wider rim of CDs. The different types of CDs directly affect the binding energy and the stability of the inclusion complexes. MβCD provides the most stable inclusion complex of UC781 among all CDs in this study due to the effect of methoxy groups (-OCH(3)) at C2 and C6 positions on the glucopyranose of CDs. Structure analysis of CDs and the orientation of UC781 inside CD cavities as well as the effects of aqueous solution to the inclusion complexes of UC781/CDs are discussed. Results of this study have provided an agreeable output; therefore, a reliable prediction method for other drug/CD inclusion complex formations is introduced.

Development of low-cost amine-enriched solid sorbent for CO2 capture

CO2 capture amine-enriched solid sorbent using agricultural wastes, such as bagasse, or industrial wastes, such as mullite, as support materials could provide efficient alternative CO2 reduction due to their low cost and ability to shape into many forms. These amine-enriched solid sorbents were prepared by treatment with monoethanolamine (MEA), diethanolamine, piperazine (PZ), 2-(2-aminoethyl-amino) ethanol (AEEA) and mixtures of these amines. The performance of amine-enriched solid sorbents with various amine compositions was studied in a tubular column at 1 atm and an adsorption temperature of 303 K. The CO2 capture capacities of the amine-enriched solid sorbents were determined by gas chromatography at a desorption temperature of 393 K. Amine-enriched solid sorbents in this study exhibited high performance CO2 capture. The MEA-PZ-enriched solid sorbent does have the highest CO2 capture performance of the amine-enriched bagasse support-based sorbents, and the results indicate that PZ is the most effective promoter in this study. The CO2 capture performances of solid sorbents in this study were compared with commercial solid sorbents. This study could lead to the development of low-cost solid sorbents for CO2 capture that can be used in many industrial applications.

A novel prediction approach for antimalarial activities of Trimethoprim, Pyrimethamine, and Cycloguanil analogues using extremely randomized trees

Malaria is still one of the most serious diseases in tropical regions. This is due in part to the high resistance against available drugs for the inhibition of parasites, Plasmodium, the cause of the disease. New potent compounds with high clinical utility are urgently needed. In this work, we created a novel model using a regression tree to study structure-activity relationships and predict the inhibition constant, Ki of three different antimalarial analogues (Trimethoprim, Pyrimethamine, and Cycloguanil) based on their molecular descriptors. To the best of our knowledge, this work is the first attempt to study the structure-activity relationships of all three analogues combined. The most relevant descriptors and appropriate parameters of the regression tree are harvested using extremely randomized trees. These descriptors are water accessible surface area, Log of the aqueous solubility, total hydrophobic van der Waals surface area, and molecular refractivity. Out of all possible combinations of these selected parameters and descriptors, the tree with the strongest coefficient of determination is selected to be our prediction model. Predicted Ki values from the proposed model show a strong coefficient of determination, R2=0.996, to experimental Ki values. From the structure of the regression tree, compounds with high accessible surface area of all hydrophobic atoms (ASA_H) and low aqueous solubility of inhibitors (Log S) generally possess low Ki values. Our prediction model can also be utilized as a screening test for new antimalarial drug compounds which may reduce the time and expenses for new drug development. New compounds with high predicted Ki should be excluded from further drug development. It is also our inference that a threshold of ASA_H greater than 575.80 and Log S less than or equal to -4.36 is a sufficient condition for a new compound to possess a low Ki.

A False Alarm Reduction Method for a Gas Sensor Based Electronic Nose

Electronic noses (E-Noses) are becoming popular for food and fruit quality assessment due to their robustness and repeated usability without fatigue, unlike human experts. An E-Nose equipped with classification algorithms and having open ended classification boundaries such as the k-nearest neighbor (k-NN), support vector machine (SVM), and multilayer perceptron neural network (MLPNN), are found to suffer from false classification errors of irrelevant odor data. To reduce false classification and misclassification errors, and to improve correct rejection performance; algorithms with a hyperspheric boundary, such as a radial basis function neural network (RBFNN) and generalized regression neural network (GRNN) with a Gaussian activation function in the hidden layer should be used. The simulation results presented in this paper show that GRNN has more correct classification efficiency and false alarm reduction capability compared to RBFNN. As the design of a GRNN and RBFNN is complex and expensive due to large numbers of neuron requirements, a simple hyperspheric classification method based on minimum, maximum, and mean (MMM) values of each class of the training dataset was presented. The MMM algorithm was simple and found to be fast and efficient in correctly classifying data of training classes, and correctly rejecting data of extraneous odors, and thereby reduced false alarms.

A prediction approach for anti-HIV activity of HEPT compounds using random forest technique

The human immunodeficiency virus type 1 (HIV-1) is one of the deadliest viruses that affect public health worldwide. Joint United Nations Programme on HIV/AIDS (UNAIDS) and World Health Organization estimate that there are more than 15 million people infected with this HIV-1 around the world. The cure of HIV-1 and a better understanding of effective drugs are urgently needed. In this work, we study the structure–activity relationship and predict the potency of HIV-1 drug compounds. We employ the random forest technique to select relevant molecular descriptors of 132 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) compounds toward the inhibition of HIV-1 reverse transcriptase (RT). The best model yields 5 relevant descriptors with a coefficient of determination (R2) of 0.83. Our prediction model suggests that a potent HEPT compound must be a lipophilic molecule with a high value of fractional hydrophobic van der Waals surface areas.Graphical abstract

Host-Guest Interactions of Plumbagin with β-Cyclodextrin, Dimethyl-β-Cyclodextrin and Hydroxypropyl-β-Cyclodextrin: Semi-Empirical Quantum Mechanical PM6 and PM7 Methods

Molecular interactions of plumbagin inclusion complexes with β-cyclodextrin (BCD), dimethyl-β-cyclodextrin (MBCD), and hydroxypropyl-β-cyclodextrin (HPBCD) were investigated by semi-empirical, Parameterization Method 6 and 7 (PM6, and PM7) in the aqueous phase using polarizable continuum calculations. The results revealed two different binding modes of the plumbagin molecule inside the BCD cavity with a negative value of the complexation energy. In conformation-I, the hydroxyl phenolic group of plumbagin was placed in the BCD cavity near the narrow-side of the host molecule. In the other model, conformation-II, the methyl quinone group of plumbagin was placed in the cavity of BCD near the narrow-side of the host molecule. The higher the negative value of the complexation energy, the more favorable is the pathway of inclusion-complex formation.

Reduced Temperature Ammonia Decomposition Using Ni/Zr-Doped Al 2 O 3 Catalyst

The development of Ni/Zr-doped Al2O3 was achieved to reduce the reaction temperatures in ammonia decomposition by doping Zr into Al2O3 framework. The Ni/Zr-doped Al2O3 exhibits higher H2 yield and NH3 conversion than Ni/γ-Al2O3 in a continuous operation. Partial doping of Zr in Al2O3 framework can increase Ni dispersion, Ni surface area and basic sites of the Ni catalyst. These effects can promote in both dehydrogenation of NH3 and recombination of nitrogen adsorbates in an NH3 decomposition mechanism. The comparison between roles of Zr as a dopant and a promoter for Ni catalyst was also discussed.Graphical Abstract

Theoretical Investigation of the Enantioselective Complexations between pfDHFR and Cycloguanil Derivatives

Point mutations in Plasmodium falciparum dihydrofolate reductase (pfDHFR), especially the double mutant variant (A16V + S108T), led to ineffective inhibiting by cycloguanil (Cyc). Cycloguanil derivatives showed good inhibiting properties against wild-type and mutant pfDHFR with an inhibition constant as low as the nanomolar level. However, there have been no reports on the stereochemistry of the compounds, and this is important because the pure enantiomeric form of a chiral drug can exert desirable, as well as non-desirable responses on the body or both. In this work, three-dimensional structures of Cyc derivatives in R and S configuration were constructed and optimized using Hartree-Fock/6-31G (d,p). Their structures were docked into the binding pocket of wild-type and double mutant (A16V + S108T) pfDHFR, complexed with nicotinamide adenine dinucleotide phosphate (NADPH). Results indicate that both wild-type and mutant pfDHFR are enantioselective towards enantiomeric Cyc derivatives (R and S configuration).

Structural and Dynamics Perspectives on the Binding of Substrate and Inhibitors in Mycobacterium tuberculosis DHFR

Dihydrofolate reductase (DHFR), an essential enzyme in the folate pathway, is a potential target for new anti-tuberculosis drugs. Fifteen crystal structures of Mycobacterium tuberculosis DHFR complexed with NADPH and various inhibitors are available in the RCSB Protein Data Bank, but none of them is a substrate binding structure. Therefore, we performed molecular dynamics simulations on ternary complexes of M. tuberculosis DHFR:NADPH with a substrate (dihydrofolate) and each of three competitive inhibitors in 2,4-diaminopyrimidine series (P1, P157, and P169), in order to gain insight into the inhibition-mechanism of DHFR in the folate pathway. The binding energy and thermodynamics values of each system were calculated by the Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) method. The dynamics of the enzyme and the motion of each amino acid residue at the active site were examined. The key factors that promote the binding of P157 and P169 on M. tuberculosis DHFR (mtbDHFR) reveal opportunities for using these compounds as novel anti-tuberculosis drugs.