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).
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.
Triazine-2-(14)C metsulfuron-methyl is a selective, systemic sulfonylurea herbicide. Degradation studies in soils are essential for the evaluation of the persistence of pesticides and their breakdown products. The purpose of the present study was to investigate the degradation of triazine-2-(14)C metsulfuron-methyl in soil under laboratory conditions. A High Performance Liquid Chromatograph (HPLC) equipped with an UV detector and an on-line radio-chemical detector, plus a Supelco Discovery column (250 x 4.6 mm, 5 μm), and PRP-1 column (305 x 7.0 mm, 10 μm) was used for the HPLC analysis. The radioactivity was determined by a Liquid Scintillation Counter (LSC) in scintillation fluid. The soil used was both sterilized and non-sterilized in order to observe the involvement of soil microbes. The estimated DT50 and DT90 values of metsulfuron-methyl in a non-sterile system were observed to be 13 and 44 days, whereas in sterilized soil, the DT50 and DT90 were 31 and 70 days, respectively. The principal degradation product after 60 days was CO2. The higher cumulative amount of (14)CO2 in (14)C-triazine in the non-sterilized soil compared to that in the sterile system suggests that biological degradation by soil micro-organisms significantly contributes to the dissipation of the compound. The major routes of degradation were O-demethylation, sulfonylurea bridge cleavage and the triazine "ring-opened."
In this study, durian (Durio zibethinus Murray) skin was examined for its ability to remove methylene blue (MB) dye from simulated textile wastewater. Adsorption equilibrium and kinetics of MB removal from aqueous solutions at different parametric conditions such as different initial concentrations (2-10 mg/L), biosorbent dosages (0.3-0.7 g) and pH solution (4-9) onto durian skin were studied using batch adsorption. The amount of MB adsorbed increased from 3.45 to 17.31 mg/g with the increase in initial concentration of MB dye; whereas biosorbent dosage increased from 1.08 to 2.47 mg/g. Maximum dye adsorption capacity of the durian skin was found to increase from 3.78 to 6.40 mg/g, with increasing solution pH. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich isotherm models. The sorption equilibrium was best described by the Freundlich isotherm model with maximum adsorption capacity of 7.23 mg/g and this was due to the heterogeneous nature of the durian skin surface. Kinetic studies indicated that the sorption of MB dye tended to follow the pseudo second-order kinetic model with promising correlation of 0.9836 < R(2) < 0.9918.
Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb(2+), Cu(2+), Fe(2+), and Zn(2+) onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment.
Electrokinetic process has emerged as an important tool for remediating heavy metal-contaminated soil. The process can concentrate heavy metals into smaller soil volume even in the absence of hydraulic flow. This makes it an attractive soil pre-treatment method before other remediation techniques are applied such that the chemical consumption in the latter stage can be reduced. The present study evaluates the feasibility of electrokinetic process in concentrating lead (Pb) and chromium (Cr) in a co-contaminated soil using different types of wetting agents, namely 0.01 M NaNO3, 0.1 M citric acid and 0.1 M EDTA. The data obtained showed that NaNO3 and citric acid resulted in poor Pb electromigration in this study. As for Cr migration, these agents were also found to give lower electromigration rate especially at low pH region as a result of Cr(VI) adsorption and possible reduction into Cr(III). In contrast, EDTA emerged as the best wetting agent in this study as it formed water-soluble anionic complexes with both Pb and Cr. This provided effective one-way electromigration towards the anode for both ions, and they were accumulated into smaller soil volume with an enrichment ratio of 1.55-1.82. A further study on the application of approaching cathode in EDTA test showed that soil alkalisation was achieved, but this did not provide significant enhancement on electromigration for Pb and Cr. Nevertheless, the power consumption for electrokinetic process was decreased by 22.5%.
The adsorption behavior of chitosan (CS) beads modified with 3-aminopropyl triethoxysilane (APTES) for the removal of reactive blue 4 (RB4) in batch studies has been investigated. The effects of modification conditions, such as the APTES concentration, temperature and reaction time on RB4 removal, were studied. The adsorbent prepared at a concentration of 2 wt% APTES for 8h at 50 °C was the most effective one for RB4 adsorption. The adsorption capacity of modified CS beads (433.77 mg/g) was 1.37 times higher than that of unmodified CS beads (317.23 mg/g). The isotherm data are adequately described by a Freundlich model, and the kinetic study revealed that the pseudo-second-order rate model was in better agreement with the experimental data. The negative values of the thermodynamic parameters, including ΔG° (-2.28 and -4.70 kJ/mol at 30 ± 2 °C), ΔH° (-172.18 and -43.82 kJ/mol) and ΔS° (-560.71 and -129.08 J/mol K) for CS beads and APTES modified beads, respectively, suggest that RB4 adsorption is a spontaneous and exothermic process.
A cis-regulatory genetic element which targets gene expression to stem cells, termed stem cell enhancer, serves as a molecular handle for stem cell-specific genetic engineering. Here we show the generation and characterization of a tamoxifen-inducible CreERT2 transgenic (Tg) mouse employing previously identified hematopoietic stem cell (HSC) enhancer for Runx1, eR1 (+24 m). Kinetic analysis of labeled cells after tamoxifen injection and transplantation assays revealed that eR1-driven CreERT2 activity marks dormant adult HSCs which slowly but steadily contribute to unperturbed hematopoiesis. Fetal and child HSCs that are uniformly or intermediately active were also efficiently targeted. Notably, a gene ablation at distinct developmental stages, enabled by this system, resulted in different phenotypes. Similarly, an oncogenic Kras induction at distinct ages caused different spectrums of malignant diseases. These results demonstrate that the eR1-CreERT2 Tg mouse serves as a powerful resource for the analyses of both normal and malignant HSCs at all developmental stages.
In the aimed research study, a new series of N-(aryl)-3-[(4-phenyl-1-piperazinyl)methyl]benzamides was synthesized, which was envisaged as tyrosinase inhibitor. The structures of these newly designed molecules were verified by IR, 1H-NMR, 13C-NMR, EI-MS and CHN analysis data. These molecules were screened against tyrosinase and their inhibitory activity explored that these 3-substituted-benzamides exhibit good to excellent potential, comparative to the standard. The Kinetics mechanism was investigated through Lineweaver-Burk plots which depicted that molecules inhibited this enzyme in a competitive mode. Moreover, molecular docking was also performed to determine the binding interaction of all synthesized molecules (ligands) with the active site of tyrosinase enzyme and the results showed that most of the ligands exhibited efficient binding energy values. Therefore, it is anticipated that these molecules might serve as auspicious therapeutic scaffolds for treatment of the tyrosinase associated skin disorders.
Herein, this work targets to employ the blended fruit wastes including rambutan (Nephelium lappaceum) peel and durian (Durio zibethinus) seed as a promising precursor to produce activated carbon (RPDSAC). The generation of RPDSAC was accomplished through a rapid and practical procedure (microwave-ZnCl2 activation). To evaluate the adsorptive capabilities of RPDSAC, its efficacy in eliminating methylene blue (MB), a simulated cationic dye, was measured. The Box-Behnken design (BBD) was utilized to optimize the crucial adsorption parameters, namely A: RPDSAC dose (0.02-01 g/100 mL), B: pH (4-10), and C: time (2-6 min). The BBD design determined that the highest level of MB removal (79.4%) was achieved with the condition dosage of RPDSAC at 0.1 g/100 mL, contact time (6 min), and pH (10). The adsorption isotherm data is consistent with the Freundlich concept, and the pseudo-second-order versions adequately describe the kinetic data. The monolayer adsorption capacity (qmax) of RPDSAC reached 120.4 mg/g at 25 °C. Various adsorption mechanisms are involved in the adsorption of MB dye onto the surface of RPDSAC, including π-π stacking, H-bonding, pore filling, and electrostatic forces. This study exhibits the potential of the RPDSAC as an adsorbent for removal of toxic cationic dye (MB) from contaminated wastewater.
This study introduces an innovative magnetic-based multifunctional anti-cancer drug carrier aiming to enhance the efficacy of curcumin in cancer therapy. The research investigates the potential of Graphene Quantum Dots (GQDs) as a curcumin drug delivery system for inhibiting in vivo cancer growth. GQDs with a particle diameter below 10 nm were synthesized via hydrothermal and Hummers methods, exhibiting homogeneity and crystalline structure according to AFM and XRD analyses. FTIR analysis confirmed functionalization success, revealing the formation of bonds between GQDs and curcumin. The optical properties of GQDs were assessed using a UV-Vis spectrophotometer and spectrofluorometer, resulting in vigorous fluorescence with a quantum yield of 1.32%. Subsequently, loading curcumin onto GQDs (CQDs/cur) resulted in an efficient system for delivering the anti-cancer drug, demonstrating significant in vivo efficacy. It was indicated by reduced tumor diameter and increased body weight in mice. Furthermore, the release kinetics of curcumin from GQDs were analyzed using the Peppas-Sahlin equation under varying pH conditions (4, 7, and 9), revealing the highest release rate in acidic conditions. In conclusion, this study highlights the potential of GQDs as highly efficient carriers for targeted curcumin delivery, showcasing promising prospects in cancer treatment.
Chitosan salicylaldehyde/calcium oxide nanoparticle (CS-SL/CaO) was synthesized by hydrothermal process and isolated via different drying processes, namely, air-drying (AD) and freeze-drying (FD). The physicochemical properties of freeze-dried CS-SL/CaO nanoparticle (CS-SL/CaO-FD) and air-dried CS-SL/CaO nanoparticle (CS-SL/CaO-AD) were compared. In particular, the adsorption properties reveal that the specific surface area of CS-SL/CaO-FD increased by ca. 6 times (BET SA = 7.28 m2/g) greater than CS-SL/CaO-FD (BET SA = 1.26 m2/g). Also, the adsorptive removal of acid red 88 dye (AR88) from aqueous media was optimized by employing the Box-Behnken design (BBD). The optimal adsorption conditions obtained from desirability functions test for the removal of AR88 dye employed a dosage of 0.09 g/100 mL of adsorbent dosage at a solution pH of 5.6 and 25 °C. The best AR88 dye removal was found for the adsorbents CS-SL/CaO-AD (38.2 %) and CS-SL/CaO-FD (86.1 %), which concur with differences in the adsorbent surface areas. Moreover, the adsorption kinetics and isotherm profiles for CS-SL/CaO-FD were described by the pseudo second order (PSO) and Temkin models, where the maximum adsorption capacity of AR88 by CS-SL/CaO-FD 175.4 was mg/g. These findings reveal the potential application of the CS-SL/CaO-FD towards removal of toxic cationic dye (AR88) from an aqueous environment.
In this pioneering study, electrostatic spraying (ES) technology with high voltages is proposed to reduce the size of hydrogel microbeads further, aiming to enhance the adsorption rate of cationic methylene blue (MB) dye. The increased voltages, ranging from 0.0 to 13.0 kV, further decreased the size of electrostatically sprayed hydrogel microbeads crosslinked by hydrogen bonds between sodium alginate (SA) and carboxymethyl chitosan (CMCS) in hydrochloric acid. The size of SA/CMCS hydrogel microbeads was successfully reduced from 2000 ± 121 μm (SC-2000) to 400 ± 15 μm (SC-400). Notably, SC-400 exhibits the highest maximum adsorption capacity (qm) and rate constant (k2) at 840.3 mg/g and 0.0598 g/mg/min, respectively, at pH 9.0 and a temperature of 25 °C in the absence of ionic compounds, which is three times higher than that of SC-2000, due to their high specific surface area and pore volume. Through a series of adsorption studies and characterization analyses, SA/CMCS hydrogel microbeads displayed heterogeneous adsorption behaviors towards MB dye through electrostatic interactions between the deprotonated carboxylic groups and cationic MB molecules, where MB adsorption efficiency could be significantly influenced by pH and ionic strength. These findings suggest that ES technology is effective in synthesizing smaller SA/CMCS hydrogel microbeads with enhanced MB removal rates and stable adsorption capacities and their applications could be further explored for removing other organic dyes and toxic metals in subsequent research studies.
Herein, a mesoporous magnetic chitosan-salicylaldehyde/calcium oxide nanoparticle (CS-SL/CaO/Fe3O4) biocomposite adsorbent that was prepared via freeze-drying. The CS-SL/CaO/Fe3O4 was utilized for the adsorption of ramazol brilliant blue (RBB) dye from aqueous solution. The physicochemical properties of the CS-SL/CaO/Fe3O4 were evaluated using diverse characterization techniques, including BET, XRD, FTIR, FESEM-EDX, CHNS, and pHpzc. The three main factors for adsorption included the following A: CS-SL/CaO/Fe3O4 dosage (0.02-0.1 g/100 mL), B: pH (4-10), and C: Time (60-540 min). These factors were improved using statistical methods, specifically the Box-Behnken design (BBD). The optimal conditions for achieving maximum RBB removal (62.5 %) are listed: CS-SL/CaO/Fe3O4 dosage of 0.1 g/100 mL, a solution pH of 7, and a contact time of 540 min. The adsorption kinetics and equilibrium isotherms were well described by the pseudo first order (PFO) kinetic and Langmuir isotherm models, respectively. Thus, the CS-SL/CaO/Fe3O4 material has a maximum adsorption capacity (qmax) of 63.3 mg/g for RBB at 25 °C. The adsorption mechanism of RBB onto the CS-SL/CaO/Fe3O4 surface was attributed to electrostatic forces, n-π stacking, H-bonding, and Pi-Pi interactions. Thus, CS-SL/CaO/Fe3O4 represents a recoverable magnetic adsorbent with potential for capture of organic dyes from wastewater.
The hazardous dyes on mixing with water resources are affecting many life forms. Granite stone is popular worldwide for decorating floors, making other forms of decorative materials and items. Granite stone powder waste can be obtained free of cost from marble factories as factories spend on the disposal of this waste. In the present study, novel granite stone powder waste composite has been prepared and utilized for the effective removal of Terasil dye. Two types of granite including gray granite and white granite were used in pure, calcinized, and chemically modified forms. Freundlich adsorption isotherm model best explained the adsorption mechanism of dye removal using granite composites as compared to other adsorption isothermal models. Characterization techniques like scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were used for the determination of morphological features and functional groups of granite composites. The obtained results were statistically analyzed using analysis of variance (ANOVA) along with the post hoc Tukey test. An extraordinarily high Terasil dye uptake capacity (more than 400 mg/g) was exhibited by granite composites prepared using sodium metasilicate. The synthesized novel nano-constructed composites provided a viable strategy as compared to the pure granite stone for dye removal from wastewater water.
The de novo biosynthesis of phosphatidylcholine and phosphatidylethanolamine in Entamoeba histolytica is largely dependent on the CDP-choline and CDP-ethanolamine pathways. Although the first enzymes of these pathways, EhCK1 and EhCK2, have been previously characterized, their enzymatic activity was found to be low and undetectable, respectively. This study aimed to identify the unusual characteristics of these enzymes in this deadly parasite. The discovery that EhCKs prefer Mn2+ over the typical Mg2+ as a metal ion cofactor is intriguing for CK/EK family of enzymes. In the presence of Mn2+, the activity of EhCK1 increased by approximately 108-fold compared to that in Mg2+. Specifically, in Mg2+, EhCK1 exhibited a Vmax and K0.5 of 3.5 ± 0.1 U/mg and 13.9 ± 0.2 mM, respectively. However, in Mn2+, it displayed a Vmax of 149.1 ± 2.5 U/mg and a K0.5 of 9.5 ± 0.1 mM. Moreover, when Mg2+ was present at a constant concentration of 12 mM, the K0.5 value for Mn2+ was ~ 2.4-fold lower than that in Mn2+ alone, without affecting its Vmax. Although the enzyme efficiency of EhCK1 was significantly improved by about 25-fold in Mn2+, it is worth noting that its Km for choline and ATP were higher than in equimolar of Mg2+ in a previous study. In contrast, EhCK2 showed specific activity towards ethanolamine in Mn2+, exhibiting Michaelis-Menten kinetic with ethanolamine (Km = 312 ± 27 µM) and cooperativity with ATP (K0.5 = 2.1 ± 0.2 mM). Additionally, we investigated the effect of metal ions on the substrate recognition of human choline and ethanolamine kinase isoforms. Human choline kinase α2 was found to absolutely require Mg2+, while choline kinase β differentially recognized choline and ethanolamine in Mg2+ and Mn2+, respectively. Finally, mutagenesis studies revealed that EhCK1 Tyr129 was critical for Mn2+ binding, while Lys233 was essential for substrate catalysis but not metal ion binding. Overall, these findings provide insight into the unique characteristics of the EhCKs and highlight the potential for new approaches to treating amoebiasis. Amoebiasis is a challenging disease for clinicians to diagnose and treat, as many patients are asymptomatic. However, by studying the enzymes involved in the CDP-choline and CDP-ethanolamine pathways, which are crucial for de novo biosynthesis of phosphatidylcholine and phosphatidylethanolamine in Entamoeba histolytica, there is great potential to discover new therapeutic approaches to combat this disease.
There has been significant progress in the last few decades in addressing the biomedical applications of polymer hydrogels. Particularly, stimuli responsive hydrogels have been inspected as elegant drug delivery systems capable to deliver at the appropriate site of action within the specific time. The present work describes the synthesis of pH responsive semi-interpenetrating network (semi-IPN) hydrogels of N-succinyl-chitosan (NSC) via Schiff base mechanism using glutaraldehyde as a crosslinking agent and Poly (acrylamide-co-acrylic acid)(Poly (AAm-co-AA)) was embedded within the N-succinyl chitosan network. The physico-chemical interactions were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscope (FESEM). The synthesized hydrogels constitute porous structure. The swelling ability was analyzed in physiological mediums of pH 7.4 and pH 1.2 at 37°C. Swelling properties of formulations with various amounts of NSC/ Poly (AAm-co-AA) and crosslinking agent at pH 7.4 and pH 1.2 were investigated. Hydrogels showed higher swelling ratios at pH 7.4 while lower at pH 1.2. Swelling kinetics and diffusion parameters were also determined. Drug loading, encapsulation efficiency, and in vitro release of 5-fluorouracil (5-FU) from the synthesized hydrogels were observed. In vitro release profile revealed the significant influence of pH, amount of NSC, Poly (AAm-co-AA), and crosslinking agent on the release of 5-FU. Accordingly, rapid and large release of drug was observed at pH 7.4 than at pH 1.2. The maximum encapsulation efficiency and release of 5-FU from SP2 were found to be 72.45% and 85.99%, respectively. Kinetics of drug release suggested controlled release mechanism of 5-FU is according to trend of non-Fickian. From the above results, it can be concluded that the synthesized hydrogels have capability to adapt their potential exploitation as targeted oral drug delivery carriers.
This study investigated the reaction kinetics and mechanism of the degradation of 5,5-diphenylhydantoin (DPH) during conventional chlorination and UV/chlorination. DPH is one of the antiepileptic drugs, which has frequently been detected in the aquatic environment. For chlorination, the second-order rate constant for the reaction between DPH and free active chlorine (FAC) was determined at pH 5 to 8. At pH 6 to 8, the efficiency of chlorination in the removal of DPH was found to be dominated by the reaction involving hypochlorous acid (HOCl). The result also showed that anionic species of DPH was more reactive toward FAC as compared with neutral DPH. For UV/chlorination, the effect of FAC dosage and pH on the degradation of DPH was evaluated. UV/chlorination is a more effective method for removing DPH as compared with conventional chlorination and UV irradiation. The DPH degradation rate was found to increase with increasing FAC concentration. On the other hand, the degradation of DPH was found to be more favorable under the acidic condition. Based on the identified transformation by-products, DPH was found to be degraded through the reaction at imidazolidine-2,4-dione moiety of DPH for both chlorination and UV/chlorination. Toxicity study on the chlorination and UV/chlorination-treated DPH solutions suggested that UV/chlorination is a more efficient method for reducing the toxicity of DPH.
Enzymatic reduction of carbon dioxide (CO2 ) to methanol (CH3 OH) can be accomplished using a designed set-up of three oxidoreductases utilizing reduced pyridine nucleotide (NADH) as cofactor for the reducing equivalents electron supply. For this enzyme system to function efficiently a balanced regeneration of the reducing equivalents during reaction is required. Herein, we report the optimization of the enzymatic conversion of formaldehyde (CHOH) to CH3 OH by alcohol dehydrogenase, the final step of the enzymatic redox reaction of CO2 to CH3 OH, with kinetically synchronous enzymatic cofactor regeneration using either glucose dehydrogenase (System I) or xylose dehydrogenase (System II). A mathematical model of the enzyme kinetics was employed to identify the best reaction set-up for attaining optimal cofactor recycling rate and enzyme utilization efficiency. Targeted process optimization experiments were conducted to verify the kinetically modeled results. Repetitive reaction cycles were shown to enhance the yield of CH3 OH, increase the total turnover number (TTN) and the biocatalytic productivity rate (BPR) value for both system I and II whilst minimizing the exposure of the enzymes to high concentrations of CHOH. System II was found to be superior to System I with a yield of 8 mM CH3 OH, a TTN of 160 and BPR of 24 μmol CH3 OH/U · h during 6 hr of reaction. The study demonstrates that an optimal reaction set-up could be designed from rational kinetics modeling to maximize the yield of CH3 OH, whilst simultaneously optimizing cofactor recycling and enzyme utilization efficiency.
Interaction of an anticancer drug, vandetanib (VDB) with a ligand transporter, lysozyme (LYZ) was explored using multispectroscopic techniques, such as fluorescence, absorption and circular dichroism along with computational analysis. Fluorescence data and absorption results confirmed VDB-LYZ complexation. VDB-induced quenching was characterized as static quenching based on inverse correlation of KSV with temperature as well as kq values. The complex was characterized by the weak binding constant (Ka=4.96-3.14×103M-1). Thermodynamic data (ΔS=+12.82Jmol-1K-1; ΔH=-16.73kJmol-1) of VDB-LYZ interaction revealed participation of hydrophobic and van der Waals forces along with hydrogen bonds in VDB-LYZ complexation. Microenvironmental perturbations around tryptophan and tyrosine residues as well as secondary and tertiary structural alterations in LYZ upon addition of VDB were evident from the 3-D fluorescence, far- and near-UV CD spectral analyses, respectively. Interestingly, addition of VDB to LYZ significantly increased protein's thermostability. Molecular docking results suggested the location of VDB binding site near the LYZ active site while molecular dynamics simulation results suggested stability of VDB-LYZ complex. Presence of Mg2+, Ba2+ and Zn2+ was found to interfere with VDB-LYZ interaction.