A New Practical Route to ZSM‐5 Nanoparticles and Optimization of Synthetic Parameters through D‐optimal Design of Experiments

A D‐optimal experimental design with three levels of SiO₂/Al₂O₃, template/SiO₂, H₂O/SiO₂, Na₂O/SiO₂ and TPABr/TPAOH ratio parameters has been used to optimize the experimental parameters by an analysis of variances (ANOVA). The effects of these ratios in the initial synthetic mixture on the size of the ZSM‐5 zeolite nanoparticles have been studied. XRD and FE‐SEM analyses were used to characterize synthetic samples. Fischer test results showed that H₂O/SiO₂ and TPABr/TPAOH ratios are the most and least effective parameters, respectively, in the range studied. The most important two‐way interaction variables were the interaction of template/SiO₂ and TPABr/TPAOH molar ratios. The average particle size was in the 34–79 nm range. Furthermore, a mathematical model for the synthesis of ZSM‐5 zeolite nanoparticles was derived using experimental results. The optimized gel composition is as follows: SiO₂/Al₂O₃₌91.20, template/SiO₂₌0.16, H₂O/SiO₂₌40.42, Na₂O/SiO₂₌0.0147 and TPABr/TPAOH=0.     

Dendrimer‐reinforced sol–gel based hollow fiber solid‐phase microextraction for citalopram determination using response surface methodology

The inclusion of a polyamidoamine dendrimer in a silica sol–gel yielded a solid nanosorbent that was used for the preconcentration, extraction, and determination of citalopram in hospital waste water, hemodialysis solution, and some drinking water. The method was developed by applying a novel nanosorbent for the solid‐phase microextraction of citalopram, containing a silica sol–gel reinforced by polyamidoamine second‐generation dendrimer, which was protected by a polypropylene hollow fiber. Plackett–Burman design and central composite design were utilized to evaluate the significance of several factors on the extraction efficiency. The adsorption mechanism and thermodynamic and kinetic aspects were studied. The adsorption process was exothermic and well fitted to the Bangham equation kinetic model. Under optimal conditions, the presented method was liner in the range of 0.05–100 μg/mL. The limits of detection of quantification of citalopram were 0.0095 and 0.031 μg m/L, respectively.     

Dead-end elimination for multistate protein design

Multistate protein design is the task of predicting the amino acid sequence that is best suited to selectively and stably fold to one state out of a set of competing structures. Computationally, it entails solving a challenging optimization problem. Therefore, notwithstanding the increased interest in multistate design, the only implementations reported are based on either genetic algorithms or Monte Carlo methods. The dead-end elimination (DEE) theorem cannot be readily transfered to multistate design problems despite its successful application to single-state protein design. In this article we propose a variant of the standard DEE, called type-dependent DEE. Our method reduces the size of the conformational space of the multistate design problem, while provably preserving the minimal energy conformational assignment for any choice of amino acid sequence. Type-dependent DEE can therefore be used as a preprocessing step in any computational multistate design scheme. We demonstrate the applicability of type-dependent DEE on a set of multistate design problems and discuss its strength and limitations.     

Structure‐based redesign of proteins for minimal T‐cell epitope content

The protein universe displays a wealth of therapeutically relevant activities, but T‐cell driven immune responses to non‐“self” biological agents present a major impediment to harnessing the full diversity of these molecular functions. Mutagenic T‐cell epitope deletion seeks to mitigate the immune response, but can typically address only a small number of epitopes. Here, we pursue a “bottom‐up” approach that redesigns an entire protein to remain native‐like but contain few if any immunogenic epitopes. We do so by extending the Rosetta flexible‐backbone protein design software with an epitope scoring mechanism and appropriate constraints. The method is benchmarked with a diverse panel of proteins and applied to three targets of therapeutic interest. We show that the deimmunized designs indeed have minimal predicted epitope content and are native‐like in terms of various quality measures, and moreover that they display levels of native sequence recovery comparable to those of non‐deimmunized designs. © 2013 Wiley Periodicals, Inc.     

Optimization via experimental design of an SPE-HPLC-UV-fluorescence method for the determination of valsartan and its metabolite in human plasma samples

A chemometric approach was applied for the optimization of the extraction and separation of the antihypertensive drug valsartan and its metabolite valeryl-4-hydroxy-valsartan from human plasma samples. Due to the high number of experimental and response variables to be studied, fractional factorial design (FFD) and central composite design (CCD) were used to optimize the HPLC-UV-fluorescence method. First, the significant variables were chosen with the help of FFD; then, a CCD was run to obtain the optimal values for the significant variables. The measured responses were the corrected areas of the two analytes and the resolution between the chromatographic peaks. Separation of valsartan, its metabolite valeryl-4-hydroxy-valsartan and candesartan M1, used as internal standard, was made using an Atlantis dC18 100 mm x 3.9 mm id, 100 angstroms, 3 microm chromatographic column. The mobile phase was run in gradient elution mode and consisted of ACN with 0.025% TFA and a 5 mM phosphate buffer with 0.025% TFA at pH 2.5. The initial percentage of ACN was 32% with a stepness of 4.5%/min to reach the 50%. A flow rate of 1.30 mL/min was applied throughout the chromatographic run, and the column temperature was kept to 40+/-0.2 degrees C. In the SPE procedure, experimental design was also used in order at achieve a maximum recovery percentage and extracts free from plasma interferences. The extraction procedure for spiked human plasma samples was carried out using C8 cartridges, phosphate buffer (pH 2, 60 mM) as conditioning agent, a washing step with methanol-phosphate buffer (40:60 v/v), a drying step of 8 min, and diethyl ether as eluent. The SPE-HPLC-UV-fluorescence method developed allowed the separation and quantitation of valsartan and its metabolite from human plasma samples with an adequate resolution and a total analysis time of 1 h.     

Functional Polypyridine Co Complex as an Efficient Catalyst for Photo‐Induced Water Oxidation

A novel mononuclear cobalt complex 1 was synthesized by treatment of CoCl₂·6H₂O with a COOMe functionalized TPA ligand (TPA=tris(2‐pyridylmethyl)amine). In a basic borate buffer, 1 acts as an efficient catalyst for water oxidation, which is confirmed by an extinct catalytic oxidant wave in electrochemistry. Visible light‐driven water oxidation has been achieved by 1 with a TON of 127.7 and a TOF of 3.8 s^?1 respectively in a homogeneous system. In comparison to the reference RC with naked TPA, the higher efficiency of 1 evidences COOMe on ligand can improve the catalytic efficiency, leading to an effective pathway towards construction of a robust and stable artificial photosynthesis system.     

Synthesis and Herbicidal Activity of Novel N‐(2‐Fluoro‐5(3‐methyl‐2,6‐dioxo‐4‐(trifluoromethyl)‐2,3‐dihydro‐pyrimidin‐1(6H)‐yl)phenyl)‐2‐phenoxyacetamide Derivatives

Thirteen novel N‐(2‐fluoro‐5‐(3‐methyl‐2,6‐dioxo‐4‐(trifluoromethyl)‐2,3‐dihydropyrimidin‐1(6H)‐yl)phenyl)‐2‐phenoxy)acetamides were designed and synthesized utilizing 4‐fluoro‐aniline and ethyl 3‐amino‐4,4,4‐trifluoro‐but‐2‐enoate as starting materials. The chemical structures of all compounds were confirmed by ¹H NMR, IR, mass spectrum and elemental analyses. Subsequently, the herbicidal activities of the as‐prepared compounds were evaluated in the greenhouse. Bioassay results indicated that most of compounds had better herbicidal activities against dicotyledonous weeds. Among all the tested compounds, compounds 4a – 4i showed good herbicidal activities at both pre‐emergence and post‐emergence treatment against two or three kinds of dicotyledonous weeds, such as Abutilon theophrasti Medic, Amaranthus ascendens L, and Chenopodium album L at the dosage of 75 g ai/ha.     

Extraction of phenolic compounds from water samples by dispersive micro‐solid‐phase extraction

In this article, the use of magnetically separable sorbent polyaniline/silica‐coated nickel nanoparticles is evaluated under a dispersive micro‐solid‐phase extraction approach for the extraction of phenolic compounds from water samples. The sorbent was prepared by in situ chemical polymerization of aniline on the surface of silica‐modified nickel nanoparticles and was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X‐ray powder diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectrometry, and vibrating sample magnetometry. Effective variables such as amount of sorbent (milligrams), pH and ionic strength of sample solution, volume of eluent solvent (microliters), vortex, and ultrasonic times (minutes) were investigated by fractional factorial design. The significant variables optimized by a Box–Behnken design were combined by a desirability function. Under the optimized conditions, the calibration graphs of analytes were linear in a concentration range of 0.02–100 μg/mL, and with correlation coefficients more than 0.999. The limits of detection and quantification were in the ranges of 10–23 and 33–77 μg/L, respectively. This procedure was successfully employed in the determination of target analytes in spiked water samples; the relative mean recoveries ranged from 96 to 105%.     

Parameters optimization of supercritical fluid‐CO2 extracts of frankincense using response surface methodology and its pharmacodynamics effects

The volatile oil parts of frankincense (Boswellia carterii Birdw.) were extracted with supercritical carbon dioxide under constant pressure (15, 20, or 25 MPa) and fixed temperature (40, 50, or 60°C), given time (60, 90, or 120 min) aiming at the acquisition of enriched fractions containing octyl acetate, compounds of pharmaceutical interest. A mathematical model was created by Box‐Behnken design, a popular template for response surface methodology, for the extraction process. The response value was characterized by synthetical score, which comprised yields accounting for 20% and content of octyl acetate for 80%. The content of octyl acetate was determined by GC. The supercritical fluid extraction showed higher selectivity than conventional steam distillation. Supercritical fluid‐CO₂ for extracting frankincense under optimum condition was of great validity, which was also successfully verified by the pharmacological experiments.     

Quantitative impurity analysis of monoclonal antibody size heterogeneity by CE-LIF: example of development and validation through a quality-by-design framework

This paper describes the framework of quality by design applied to the development, optimization and validation of a sensitive capillary electrophoresis-sodium dodecyl sulfate (CE-SDS) assay for monitoring impurities that potentially impact drug efficacy or patient safety produced in the manufacture of therapeutic MAb products. Drug substance or drug product samples are derivatized with fluorogenic 3-(2-furoyl)quinoline-2-carboxaldehyde and nucleophilic cyanide before separation by CE-SDS coupled to LIF detection. Three design-of-experiments enabled critical labeling parameters to meet method requirements for detecting minor impurities while building precision and robustness into the assay during development. The screening design predicted optimal conditions to control labeling artifacts while two full factorial designs demonstrated method robustness through control of temperature and cyanide parameters within the normal operating range. Subsequent validation according to the guidelines of the International Committee of Harmonization showed the CE-SDS/LIF assay was specific, accurate, and precise (RSD ≤ 0.8%) for relative peak distribution and linear (R > 0.997) between the range of 0.5-1.5 mg/mL with LOD and LOQ of 10 ng/mL and 35 ng/mL, respectively. Validation confirmed the system suitability criteria used as a level of control to ensure reliable method performance.     

Analytical investigation of secondary metabolites extracted from Camellia sinensis L. leaves using a HPLC‐DAD‐ESI/MS data fusion strategy and chemometric methods

Considerable attention has been paid to the study of green tea leaves because of their high consume and beneficial effects on human health. In this work, an appropriate strategy is proposed to investigate and resolve the major metabolites extracted from Camellia sinensis tea leaves. Statistical design mixtures of ethanol, ethyl acetate, dichloromethane, and chloroform were used to study the effects of different solvents and their mixtures on the extraction of the secondary metabolites of C. sinensis tea leaves from two different harvest seasons. Extracted samples were analyzed by high performance liquid chromatography‐diode array detection‐electrospray ionization mass spectrometer allowing the resolution of a large amount of tea metabolites with high relative abundances, especially when their extraction was performed in pure ethanol and with solvent mixtures with ethanol. Resolution of the more relevant metabolites was achieved by the simultaneous analysis of the fused diode array detection and mass spectrometer detectors data from the same samples using the multivariate curve resolution‐alternating least squares chemometric method. Peak areas finally resolved were further analyzed by orthogonal signal correction and partial least squares‐discrimination analysis to discriminate among C. sinensis tea samples. Using the Variable Importance in Projection variable selection method, epigallocatechin and caffeine were finally selected as the two more important chemical constituents of tea leaves that were discriminating more between the tea samples from two different harvest seasons. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of 2,2‐Bis‐C‐functionalized Chain Glucosid‐3‐ketals

Novel 2,2‐bis‐C‐functionalized chain glucosid‐3‐uloses have been synthesized in the form of ketal. The synthesis is rather convenient through one pot multistep reactions and no expensive reagents are involved. The products are formed via autoxidation‐Michael addition mechanism and their structures were characterized by X‐ray crystallographic analysis. Their crystal stuctures are stablilized by intermolecular hydrogen bonds and double‐strand supramolecular stacking is observed.     

Design,Synthesis, and Insecticidal Activity of 1,5‐Diphenyl‐1‐pentanone Analogues

Three series of novel 1,5‐diphenyl‐1‐pentanone derivatives were designed and synthesized. Their structures were characterized by IR, ¹H NMR techniques, and elemental analysis. The insecticidal activities of the new compounds were preliminarily evaluated. The bioassay results indicated that the compounds X11 – X30 displayed better aphicidal activity against Aphis gossypii than compounds X1 – X10 and the lead compound (E)‐1,5‐diphenyl‐1‐penten‐1‐one ( A ). The inhibitory rates of compounds X6 and X29 were 100% against Plutella xylostella (L.) at 600 mg·L^?1. Compounds X12 , X13, X19 , X24, X25 , X26 and X27 showed higher insecticidal activity against Tetranychus cinnabarinus (Boisduval) at 600 mg·L^?1 than the lead compound ( A ).     

Developing an alcoholic‐assisted dispersive liquid–liquid microextraction for extraction of pentachlorophenol in water

Optimization of alcoholic‐assisted dispersive liquid–liquid microextraction of pentachlorophenol (PCP) and determination of it with high‐performance liquid chromatography (UV‐Vis detection) was investigated. A Plackett‐Burman design and a central composite design were applied to evaluate the alcoholic‐assisted dispersive liquid–liquid microextraction procedure. The effect of seven parameters on extraction efficiency was investigated. The factor studied were type and volume of extraction and dispersive solvents, amount of salt, and agitation time. According to Plackett‐Burman design results, the effective parameters were type and volume of extraction solvent and agitation time. Next, a central composite design was applied to obtain optimal condition. The optimized conditions were obtained at 170‐μL 1‐octanol and 5‐min agitation time. The enrichment factor of PCP was 242 with limits of detection of 0.04 μg L^?1. The linearity was 0.1–100 μg L^?1 and the extraction recovery was 92.7%. RSD for intra and inter day of extraction of PCP were 4.2% and 7.8%, respectively for five measurements. The developed method was successfully applied for the determination of PCP in environmental water samples.     

Molecular recognition at the active site of catechol-O-methyltransferase (COMT): adenine replacements in bisubstrate inhibitors

L-Dopa, the standard therapeutic for Parkinson's disease, is inactivated by the enzyme catechol-O-methyltransferase (COMT). COMT catalyzes the transfer of an activated methyl group from S-adenosylmethionine (SAM) to its catechol substrates, such as L-dopa, in the presence of magnesium ions. The molecular recognition properties of the SAM-binding site of COMT have been investigated only sparsely. Here, we explore this site by structural alterations of the adenine moiety of bisubstrate inhibitors. The molecular recognition of adenine is of special interest due to the great abundance and importance of this nucleobase in biological systems. Novel bisubstrate inhibitors with adenine replacements were developed by structure-based design and synthesized using a nucleosidation protocol introduced by Vorbrüggen and co-workers. Key interactions of the adenine moiety with COMT were measured with a radiochemical assay. Several bisubstrate inhibitors, most notably the adenine replacements thiopyridine, purine, N-methyladenine, and 6-methylpurine, displayed nanomolar IC(50) values (median inhibitory concentration) for COMT down to 6 nM. A series of six cocrystal structures of the bisubstrate inhibitors in ternary complexes with COMT and Mg(2+) confirm our predicted binding mode of the adenine replacements. The cocrystal structure of an inhibitor bearing no nucleobase can be regarded as an intermediate along the reaction coordinate of bisubstrate inhibitor binding to COMT. Our studies show that solvation varies with the type of adenine replacement, whereas among the adenine derivatives, the nitrogen atom at position 1 is essential for high affinity, while the exocyclic amino group is most efficiently substituted by a methyl group.