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A novel magnetic molecular-imprinted polymer (MMIP) was used to selectively extract folic acid directly from real samples. Folic acid was used as template molecule, Fe3O4/SiO2-3-triethoxysilyl-propyl-acrylamide as functional monomer, azobisisobutyronitrile as initiation, ethylene glycol dimethacrylate as crosslinker agent, and acrylamide as the secondary monomer in a mixed ethanol-water solvent. The effect of different parameters on the extraction efficiency was studied, and the optimum conditions were established as follows: the concentrations of crosslinking and template were fixed at 0.05 and 0.06 g, absorption percentage was 96.5, pH was adjusted to 8, and extraction time was 8 h with a temperature of 25 °C. By examining the effect of pH, we tried to investigate the effect of the amide groups that present in MMIP and its intermolecular hydrogen interaction with folic acid. After optimising the effective parameters in polymer synthesis and adsorption rate, a magnetic imprinting dispersive solid-phase extraction method combined with fluorescence spectrophotometry at λem = 367 nm (MMIP-DSPE-FL) was constructed for sensitive determination of folic acid in tomato samples. The limit of quantification (LOQ) and limit of detection (LOD) values were 30.00 ± 0.01 μg L−1 and 10.00 ± 0.03 μg L−1, respectively, after the MMIP-DSPE preconcentration. Three tomato samples were analysed to give recoveries in the range of 80.2–81.6%, with relative standard deviation values below 0.6% (n = 3). The prepared MMIP-DSPE showed high selectivity toward folic acid, which could be used six times without changing adsorption capacity. The adsorption isotherm of the folic acid-imprinted polymer pursued the Langmuir model (RL = 0.029), and the kinetics model followed pseudo-first-order (R 2 = 0.9974). [ABSTRACT FROM AUTHOR]

A novel, simple, fast and sensitive method for the simultaneous analysis of heavy metals such as Cd(II), Cr(III), Co(II), Pb(II) and Cu(II) in hair samples based on complexometric method with EDTA and using solid-phase extraction with graphene oxide coupled with capillary electrophoresis has been developed. Under the optimised conditions, the proposed methodology had limits of detection from 5.7 to 16.8 µg kg−1 with intra- and inter-day repeatabilities <5% (in respect to relative standard deviation) in all cases. The proposed method was successfully employed for determination of heavy metals in the analysis of 20 hair samples. All samples were positive for at least one of the heavy metals studied with concentrations of 1.2 ± 1.0 mg kg−1 Cd(II), 7.2 ± 4.0 mg kg−1 Cr(III), 0.9 ± 0.8 mg kg−1 Co(II), 0.6 ± 0.2 mg kg−1 Pb(II) and 2.5 ± 0.3 mg kg−1 Cu(II). The method is an easy, robust and efficient strategy for determination of heavy metals in complex matrices. [ABSTRACT FROM AUTHOR]

CrSi2 thin films with different thicknesses obtained on the Si(111) surface by magnetron sputtering method have been investigated using complex of electron spectroscopy and microscopy methods. The thin films' composition, surface morphology, and cross-section, as well as the resistivity's, Seebeck coefficient's, and power factor's temperature dependences have been studied for the first time. It has been established that, starting from a thickness of ~ 400 Å (deposition time ~ 60 sec), the SiO2/Si(111) surface is completely covered with an amorphous CrSi2 film. After heating the CrSi2/SiO2/Si(111) system at T ≈ 750 K, a homogeneous polycrystalline CrSi2/SiO2/Si(111) film is formed. It is shown that the resistivity ρ, the Seebeck coefficient S, and the power factor P of a CrSi2/SiO2/Si(111) film of different thicknesses (80 and 180 nm) change nonlinearly with increasing temperature. Their values for CrSi2 films of different thicknesses differ slightly from each other. [ABSTRACT FROM AUTHOR]

In peptide drug discovery, the C-terminal structure of peptide compounds is crucial for enhancing the affinity with target proteins and for optimizing the compound's dynamics and physical properties. In conventional solid-phase synthesis, two steps are necessary to modify the C-terminal structure: cleavage from the resin and subsequent amidation involving activation of the resulting carboxylic acid. This process can potentially lead to racemization of the C-terminal amino acid side chain. To address this issue, we developed a novel method that, in the presence of a Ta catalyst, directly allows amines to react with amino acid-loaded resins, thereby accomplishing both resin cleavage and amidation in a single step. [ABSTRACT FROM AUTHOR]

Volatile products from thermal decomposition of lignocellulosic biomass have been well characterized, but the solid- and liquid-phase reactions during the early stages of decomposition are largely unknown. Here the initial solid-phase biomass thermal deconstruction reactions were analyzed in situ and with high particle heating rates, delineating how these processes occur. A variety of instrumentation was used to quantify the extent and relative rates of deconstruction, demonstrating that biopolymers resist the thermally energetic conditions to differing degrees, even when ensconced in biomass cell walls. Hemicellulose and the more frangible lignin components decompose and volatilize more readily than cellulose, which temporarily enriches biomass with cellulose. These chemical changes manifest in larger cell wall structural and mechanical property transformations. In all, this investigation concludes that these solid-phase reactions strongly influence the production rates of volatile species and will require additional study before these processes can be modeled precisely to improve yields of desired product. [ABSTRACT FROM AUTHOR]

The accumulation of plastics and microplastics in the environment is a major global concern because of their negative impact on ecosystems and human health. The use of zinc oxide (ZnO)-based systems for photocatalytic degradation of these pollutants has shown promise. This review presents an overview of the solid- and aqueous-phase approaches employed for the degradation of plastics and microplastics using ZnO-based photocatalytic systems. The preparation of microplastic samples is discussed, highlighting various techniques used to generate representative samples for testing. The experimental setup or reactor design is explored, encompassing different configurations employed in both the solid- and aqueous-phases. Next, the impact of reaction conditions on degradation efficiency is investigated, including catalyst concentration, pH, temperature, and irradiation source. Sampling techniques for post-reaction analysis are explored, discussing methods for collecting and analyzing degraded products and byproducts in solid- and aqueous-phases. The comparative discussion was meant to assess the effectiveness and suitability of solid- and aqueous-phase methods, revealing their potential for practical use. This review paper presents an extensive analysis of the methods used in ZnO-based photocatalytic systems for plastic and microplastics degradation which the output will aid researchers and practitioners in developing effective strategies to mitigate plastic pollution. [Display omitted] • Review of recent studies on the photocatalytic degradation of plastic/microplastic utilizing ZnO-based photocatalyst. • Solid phase approach of photocatalytic degradation of plastic/microplastics. • Aqueous phase approach of photocatalytic degradation of plastic/microplastics. • Advantages and limitations of both solid and aqueous phase approach. [ABSTRACT FROM AUTHOR]

Volatile products from thermal decomposition of lignocellulosic biomass have been well characterized, but the solid- and liquid-phase reactions during the early stages of decomposition are largely unknown. Here the initial solid-phase biomass thermal deconstruction reactions were analyzed in situ and with high particle heating rates, delineating how these processes occur. A variety of instrumentation was used to quantify the extent and relative rates of deconstruction, demonstrating that biopolymers resist the thermally energetic conditions to differing degrees, even when ensconced in biomass cell walls. Hemicellulose and the more frangible lignin components decompose and volatilize more readily than cellulose, which temporarily enriches biomass with cellulose. These chemical changes manifest in larger cell wall structural and mechanical property transformations. In all, this investigation concludes that these solid-phase reactions strongly influence the production rates of volatile species and will require additional study before these processes can be modeled precisely to improve yields of desired product.

Conjugation of molecules or proteins to oligonucleotides can improve their functional and therapeutic capacity. However, such modifications are often limited to the 5′ and 3′ end of oligonucleotides. Herein, we report the development of an inexpensive and simple method that allows for the insertion of chemical handles into the backbone of oligonucleotides. This method is compatible with standardized automated solid‐phase oligonucleotide synthesis, and relies on formation of phosphoramidates. A unique phosphoramidite is incorporated into a growing oligonucleotide, and oxidized to the desired phosphoramidate using iodine and an amine of choice. Azides, alkynes, amines, and alkanes have been linked to oligonucleotides via internally positioned phosphoramidates with oxidative coupling yields above 80 %. We show the design of phosphoramidates from secondary amines that specifically hydrolyze to the phosphate only at decreased pH. Finally, we show the synthesis of an antibody‐DNA conjugate, where the oligonucleotide can be selectively released in a pH 5.5 buffer. [ABSTRACT FROM AUTHOR]

We prepared a highly sensitive electrochemical sensor for the free-enzymatic indirect detection of malathion. The electrochemical sensor was based silicon carbide and copper oxide nanocomposite material. The structural and morphological properties of the SiC@CuO-NPs nanocomposite was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). SiC-NPs has the function of malathion preconcentration and SiC@CuO-NPs nanocomposite was noted to possess high affinity towards malathion, thus the redox reaction of CuO could be hindered. This feature was utilized to design as a simple strategy for electrochemical detection of malathion. Electrochemical detection of malathion was investigated via cyclic voltammetry (CV), differential pulse voltammetry (DPV), respectively. Under the optimized experimental conditions, the inhibition rate displays a good linear relationship with the concentration of malathion, the linear range is 0.03 nM∼3.0 nM, and the detection limit is 0.01 nM (S/N=3). In addition, the sensor exhibits good selectivity, stability and reproducibility, and has been successfully used in the detection of malathion in actual water samples with recoveries between 99.33% and 106.6%, which is satisfactory experimental results. [ABSTRACT FROM AUTHOR]

Macrocycles represent attractive candidates in organic synthesis and drug discovery. Since 2014, nineteen macrocyclic drugs, including three radiopharmaceuticals, have been approved by FDA for the treatment of bacterial and viral infections, cancer, obesity, immunosuppression, etc. As such, new synthetic methodologies and high throughput chemistry (e.g., microwave-assisted and/or solid-phase synthesis) to access various macrocycle entities have attracted great interest in this chemical space. This article serves as an update on our previous review related to macrocyclic drugs and new synthetic strategies toward macrocycles (Molecules, 2013, 18, 6230). In this work, I first reviewed recent FDA-approved macrocyclic drugs since 2014, followed by new advances in macrocycle synthesis using high throughput chemistry, including microwave-assisted and/or solid-supported macrocyclization strategies. Examples and highlights of macrocyclization include macrolactonization and macrolactamization, transition-metal catalyzed olefin ring-closure metathesis, intramolecular C–C and C–heteroatom cross-coupling, copper- or ruthenium-catalyzed azide–alkyne cycloaddition, intramolecular SNAr or SN2 nucleophilic substitution, condensation reaction, and multi-component reaction-mediated macrocyclization, and covering the literature since 2010.

Amberlite XAD-4 resin (AXAD-4) was chemically modified to an aminated Amberlite XAD-4 (AAXAD-4) resin and characterized by infrared spectroscopy. AAXAD-4 resin was used as an efficient solid phase for the preconcentration and speciation of Cr(III) and Cr(VI) ions by column technique. The concentration of chromium species was determined by microsample injection system-flame atomic absorption spectrometer (MIS-FAAS). Selective retention of Cr(III) ions was achieved at pH 8.0 and eluted using 1.0 mL of 3.0 mol L–1 HCl and 1.0 mL of 2.0 mol L–1 NaOH, successively, at the flow rate of 5.0 mL min–1. The maximal sorption capacity of AAXAD-4 resin for Cr(III) ions was found to be 67.0 mg g–1. The limit of detection (LOD) and limit of quantitation (LOQ) for Cr(III) ions were found to be 0.041 and 0.131 µg L–1, respectively, with preconcentration factor (PF) of 375 and relative standard deviation (RSD) of 3.75% (n=11). The method was validated using certified reference materials (CRMs) and successfully applied to the real samples, spiked with Cr(III) and Cr(VI) ions.

A novel method was established to determine trichlorocaban, α--bromocinnamaldehyde, 2--(4--thiazole)--1H--benzimidazole and 4--chloro--3--methylphenol in textiles by solid phase extraction (SPE) with high performance liquid chromatography (HPLC) for evaluating the risk level of toxic and harmful antibacterial agents m textiles. The antibacterial agents were extracted from textiles with methanol-tetrahydrofuran, purified by strong cation exchange (SCX) SPE colume, and analyzed by HPLC-DAD on a Agilent Eclipse XDB-C18 column (150 mim x 4.6 mm, 5 µm), employing acetonitrile-water with a volume ratio of 40/60 as the mobile phase in a gradient elution mode. The antibacterial agents were qualitatively determined hy retention time, and confirmed by ultraviolet spectrum. Under the optimal conditions, the target analytes were in range of 1.0-100.0 mg/L with the correlation coefficients higher than 0.999, and the method limits of quantification of target analytes were from 2.2 mg/kg to 3.6 mg/kg when the signal to noise ratio is 10. The spiked recoveries were in the range between 86.5% and 100.3%, and relative standard deviation ranged from 1.9% to 4.3%. The method is simple, precise and has high recoveries for the determination of antibacterial agents in textiles. [ABSTRACT FROM AUTHOR]

Among the cyclic forms of carbohydrates, pyranoside derivatives have widely contributed to the well‐defined nanoassemblies. However, nanoassemblies originating from furanoside derivatives/oligomers, excluding nucleosides are underrepresented. Herein, we discuss the design and solid‐phase synthesis of homoligomers of a new class of clickable psicofuranose glycocarbamates that display nanovesicular/spherical nanostructures, an occurrence rarely observed in furanoside oligomers. The key intermediate, D‐(‐)‐fructose derived 2‐azido psicofuranose carbonate, was converted into dimeric and tetrameric azido‐glycocarbamates on solid‐phase which on subsequent "Click" reaction provided triazolyl glycocarbamates. These amphiphilic glycocarbamates self‐assembled into thermally and proteolytically stable spherical vesicles of 200‐800 nm size with visible hollow nature in CH3OH and tightly packed sphericals in CH3OH‐H2O. These nanostructures are characterized by various microscopy techniques. Effect of Cu+2 and Zn+2 ions, various cationic stimuli on the morphology of these nanostructures was studied. Hydrophobic drug curcumin was encapsulated in the hollow vesicles and release of the drug was investigated. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thioamides, amidines, and heterocycles are three classes of modifications that can act as peptide-bond isosteres to alter the peptide backbone. Thioimidate protecting groups can address many of the problematic synthetic issues surrounding installation of these groups. Historically, amidines have received little attention in peptides due to limitations in methods to access them. The first robust and general procedure for the introduction of amidines into peptide backbones exploits the utility of thioimidate protecting groups as a means to side-step reactivity that ultimately renders existing methods unsuitable for the installation of amidines along the main-chain of peptides. Further, amidines formed on-resin can be reacted to form (4H)-imidazolone heteorcycles which have recently been shown to act as cis-amide isosteres. General methods for heterocyclic installation capable of geometrically restricting peptide conformation are also under-developed. This work is significant because it describes a generally applicable and divergent approach to access unexplored peptide designs and architectures., (Copyright © 2024. Published by Elsevier Inc.)

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this report, we employed the solid-phase synthetic approach to prepare variously substituted dihydropteridinones, tetrahydropyrrolopteridinones, and pyrimidodiazepinones, using a versatile building block-4,6-dichloro-5-nitropyrimidine. All these compounds are pharmacologically significant scaffolds of the great importance of medicinal chemists. The fast and efficient synthetic methodology is highly desirable for defining their structure-activity relationship (SAR) and optimizing pharmacokinetic properties. Our research efforts utilize simple synthetic methods to generate a library of analogues for future SAR studies. The efficiency of our approach was exemplified in various pteridinones as well as pyrimidodiazepinones.

Amberlite XAD-4 resin (AXAD-4) was chemically modified to an aminated Amberlite XAD-4 (AAXAD-4) resin and characterized by infrared spectroscopy. AAXAD-4 resin was used as an efficient solid phase for the preconcentration and speciation of Cr(III) and Cr(VI) ions by column technique. The concentration of chromium species was determined by microsample injection system-flame atomic absorption spectrometer (MIS-FAAS). Selective retention of Cr(III) ions was achieved at pH 8.0 and eluted using 1.0 mL of 3.0 mol L-1 HCl and 1.0 mL of 2.0 mol L-1 NaOH, successively, at the flow rate of 5.0 mL min-1. The maximal sorption capacity of AAXAD-4 resin for Cr(III) ions was found to be 67.0 mg g-1. Th limit of detection (LOD) and limit of quantitation (LOQ) for Cr(III) ions were found to be 0.041 and 0.131 µg L-1, respectively, with preconcentration factor (PF) of 375 and relative standard deviation (RSD) of 3.75% (n = 11). The method was validated using certified reference materials (CRMs) and successfully applied to the real samples, spiked with Cr(III) and Cr(VI) ions. [ABSTRACT FROM AUTHOR]

A 2-amido benzo[d]imidazole library has been constructed by solid-phase synthesis. The key step of this solid-phase synthesis involves the preparation of polymer-bound 2-amino benzo[d]imidazole resin through desulfurative cyclization of thiourea resin using 2-chloro-1,3-dimethylimidazolinium chloride and N,N-diisopropylethylamine in dichloromethane (DCM), and the resin is then functionalized by acylation at the 2-amine position to afford 2-amidobenzo[d]imidazole resin. In the case of 2-amidobenzo[d]imidazole resin having a p-I or m-NO2, the resin was further functionalized by Suzuki/Sonogashira-coupling (p-I) and reduction to the primary amine (m-NO2) followed by acylation. Finally, the functionalized 2-amido-benzo[d]imidazole resin was cleaved from the polymer support by treatment with a cocktail of trifluoroacetic acid and DCM. As a result, we obtained 2-amidobenzo[d]imidazole analogues in high yield and good purities. [ABSTRACT FROM AUTHOR]

An efficient solid-phase synthetic route for the construction of 1,3,4-oxadiazole and 1,3,4-thiadiazole libraries based on branching diversity-oriented synthesis (DOS) has been developed in this study. The core skeleton resins, 1,3,4-oxadiazole and 1,3,4-thiadiazole, were obtained through desulfurative and dehydrative cyclizations of thiosemicarbazide resin, respectively. Various functional groups have been introduced to the core skeleton resins, such as aryl, amine, amide, urea, thiourea, and an amino acid. Most of the libraries were purified by simple trituration without extraction or column chromatography after cleavage of the products from the solid-supported resin. As a result, we obtained high yields of pure 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives (total numbers = 128). Finally, we confirmed the drug-like properties of our library by calculation of physicochemical properties, displays of the skeletal diversities of the library in 3D-space, and occupation of a broad range of areas by their functional groups. [ABSTRACT FROM AUTHOR]

Design and solid phase synthesis of the 1,3,4-oxadiazole based peptidomimetic library is presented. Library synthesis starts from the coupling of the thiosemicarbazide resin with Fmoc-protected amino acid following desulfurative cyclization to 1,3,4-oxadiazoles. Following substitution of the secondary amine with the 3-nitrobenzoyl functional group and its further reduction were performed. Thus, the functionalization with amino acids could be performed on both sides of the core skeleton. After diversification and cleavage from the resin using TFA: DCM cleavage cocktail, an enantiopure library of compounds was obtained. Further evaluation of physicochemical properties was performed. [ABSTRACT FROM AUTHOR]

deoxynucleoside triphosphate (dNTPs) are the reduced nucleotides used as the building blocks and energy source for deoxyribonucleic acid (DNA) replication and maintenance in all living systems. They are present in highly regulated amounts and ratios in the cell, and their balance has been implicated in the most important cell processes, from determining the fidelity of DNA replication to affecting cell fate. Furthermore, many cancer drugs target biosynthetic enzymes in dNTP metabolism, and mutations in genes directly or indirectly affecting these pathways that are the cause of devastating diseases. The accurate and systematic measurement of these pools is key to understanding the mechanisms behind these diseases and their treatment. We present a new method for measuring dNTP pools from biological samples, utilizing the current state-of-theart polymerase method, modified to a solid-phase setting and optimized for larger scale measurements. [ABSTRACT FROM AUTHOR]

2-Alkoxy/thioalkoxy benzo-[d]-imidazole and 2-thione benzo-[d]-imidazole libraries were constructed in solution phase and on solid phase, respectively. The key step in this work is the phase-based chemoselective reaction of the 2-mercaptobenzo-[d]-imidazole intermediate with benzyl chloride (solution phase) and Merrifield resin (solid phase). In the solution-phase case, benzyl chloride reacted with the thiol group of 2-mercaptobenzo-[d]-imidazole, whereas in the solid-phase case, Merrifield resin was introduced at an internal amine group of benzo-[d]-imidazole. To afford the desired 2-alkoxy/thioalkoxy benzo-[d]-imidazole analogues, we used various alkyl halides, alcohols, and thiols in solution phase, and to obtain 2-thione benzo-[d]-imidazole derivatives on solid phase, we used diverse alkyl halides and boronic acids. Finally, to measure the drug potential to be orally active and the molecular diversity in three-dimensional (3D) space, we calculated physicochemical properties and displayed energy-minimized 3D structures. As a result, the libraries from solution phase and solid phase show distinct features in physicochemical properties and skeletal diversities in 3D space. [ABSTRACT FROM AUTHOR]

In this study, we report on a novel approach to produce ∼12 nm thick few-layer monoclinic 1T’-MoTe 2 films. The deposition method comprised sputtering of Mo, molecular beam epitaxy of Te, and rapid thermal processing to effect tellurization of the Mo into 1T’-MoTe 2 . The heating rate and annealing time are the critical factors. 30 °C s −1 heating rate and 2 min annealing at 470 °C were adopted in this work. X-ray photoelectron spectroscopy confirmed the formation of stoichiometric 1T’-MoTe 2 films, while X-ray diffraction confirmed the monoclinic polymorph. Raman spectroscopy confirmed spatial uniformity over the sample size of 1 cm × 1.5 cm. Our fast synthesis approach to realize high-quality 1T’-MoTe 2 paves the way towards the large-scale application of 1T’-MoTe 2 in high-performance nanoelectronics and optoelectronics. [ABSTRACT FROM AUTHOR]

An efficient synthesis of d 5 -VX adducted nonapeptide and d 15 -GD adducted nonapeptide via solid-phase approach has been developed. The deuterated peptides could be used as the isotope-labeled internal standard for LC-MS/MS detecting the BuChE-OPNA biomarkers. This method also offers an access to the synthesis and detection of other phosphorylated nonapeptides. [ABSTRACT FROM AUTHOR]

This contribution showcases the interplay of several non-metathetic reactions (isomerization, silylation and "hydrogen-free" reduction) with metathesis in systems comprising a functionalized olefin and a soluble or resin-immobilized silane. These competing, one-pot reactions occur under activation by second-generation Ru-alkylidene catalysts. Different olefinic substrates were used to study the influence of the substitution pattern on the reaction outcome. Emphasis is placed upon the rarely reported yet important transformations implying a solid phase-supported silane reagent. Catalytic species involved in and reaction pathways accounting for these concurrent processes are evidenced. An unexpected result of this research was the clearly proved partial binding of the olefin to the resin, thereby removing it from the reacting ensemble. [ABSTRACT FROM AUTHOR]

Approaches to sample preparation for estimation of free fatty acids composition by gas chromatography are presented. These fatty acids are included in the total lipid extract of human plasma.

Since Gomberg’s discovery of radicals as chemical entities, the interest around them has increased through the years. Nowadays, radical chemistry is used in the synthesis of 75% of all polymers, inevitably establishing a close relationship with Solid-Phase Organic Synthesis. More recently, the interest of organic chemists has shifted towards the application of usual “in-solution” radical chemistry to the solid-phase, ranging from the use of supported reagents for radical reactions, to the development of methodologies for the synthesis of small molecules or potential libraries. The aim of this review is to put in perspective radical chemistry, moving it away from its origin as a synthetic means for solid supports, to becoming a useful tool for the synthesis of small molecules.

Trp(Nps)-Lys-NH2 derivatives, bearing alkyl or guanidine groups either at the N–terminus or on the Lys side-chain or at both positions were conveniently prepared on solid-phase and evaluated as TRPV1 channel antagonists.

A novel solid-phase synthesis methodology of N-substituted-2-aminothiazolo[4,5-b]pyrazine derivatives was developed. The key step in this synthesis strategy is the tandem reaction of isothiocyanate terminated resin 2 with o-bromo-2-aminopyrazine, affording cyclized 2-aminothiazolo[4,5-b]pyrazine resin 4. To increase the diversity of our library, Suzuki coupling reaction was performed at the position C6. Further functionalization of 2-aminothiazolo[4,5-b]pyrazine core skeleton with various electrophiles such as alkyl halides, acyl chlorides, and sulfonyl chlorides and cleavage from the resin with TFA in DCM generated N-alkyl-, N-acyl-, and N-sulfonyl-2-aminothiazolo[4,5-b]pyrazine derivatives. The physicochemical properties and the polar surface areas of synthesized compounds were evaluated. [ABSTRACT FROM AUTHOR]

A 1,3,4-thiadiazole library was constructed by solid-phase organic synthesis. The key step of this solid-phase synthesis involves the preparation of polymer-bound 2-amido-5-amino-1,3,4-thiadiazole resin by the cyclization of thiosemicarbazide resin using p-TsCl as the desulfurative agent, followed by the functionalization of the resin by alkylation, acylation, alkylation/acylation, and Suzuki coupling reactions. Both the alkylation and acylation reactions chemoselectively occurred at the 2-amide position of 2-amido-5-amino-1,3,4-thiadiazole resin and the 5-amine position of 2-amido-5-amino-1,3,4-thiadiazole resin, respectively. Finally, these functionalized 1,3,4-thiadiazole resins were treated with trifluoroacetic acid in dichloromethane, affording diverse 1,3,4-thiadiazole analogs in high yields and purities. The 1,3,4-thiadiazole analogs show a different distribution of physicochemical and biological properties compared with our previously constructed 1,3,4-oxadiazole and 1,3,4-thiadiazole libraries in a range of orally available drug properties. [ABSTRACT FROM AUTHOR]

The acetyl capping reaction used throughout solid phase oligonucleotide synthesis is meant to minimize n−1 deletionmer impurities by terminating sequences that fail to couple to a phosphoramidite. However, the reaction is also responsible for the formation of a number of impurities. One capping-related impurity has an additional mass of 98 amu from the parent oligonucleotide. The n+98 amu impurity was found to result from modification of an adenine nucleobase. The structure of the impurity was determined by preparation of an oligonucleotide enriched in n+98 amu , enzymatic digestion to individual nucleosides, isolation of the pure nucleoside+98 amu species, crystallization, and X-ray crystallographic analysis. The n+98 amu impurity is an oligonucleotide in which one adenine residue has been converted to 5-amino-4-pyrimidinylimidazole. The mechanism of formation of the impurity was investigated, and a mechanism is proposed. [ABSTRACT FROM AUTHOR]

The gastrointestinal transit of markers in pigs has been well studied, but the methods and approaches are different from gastrointestinal studies performed in humans clinically. Aim To develop a non-invasive method of estimating oral-rectal transit times in young pigs. Methods We performed transit studies in 3 groups of 4 week-old, Large White female pigs. Group 1 . Ten animals (5.7±0.34 kg (mean±SEM)) were fed blue-dyed grower feed and placed under video surveillance. Group 2a . Twenty-two animals (7.7±0.59 kg) from the same pig supplier were administered 18 4 mm-diameter radio-opaque plastic markers under light anaesthesia (5% isofluorane), and we took abdominal x-rays at 6, 30, 54 and 78 h. Group 2b . Eight pigs (9.2±0.48 kg) from a different supplier also underwent plastic marker transit studies. Results Using blue dye (fluid transit), the median (25th, 75th percentiles) time to first incidence of blue-dyed stool was 13.2 (10.2, 18.1) h and to last blue stool was 24.1 (22.4, 40.3) h. Using plastic markers, markers were evacuated between 30 and 80+ hours with differences in stomach emptying between two groups of animals from different farms. Median oral-rectal transit times were 25.2 (17.8, 40.5) h and 48.9 (26.9, 68.3) h in the second and third groups (M-W test, P =0.04). Conclusion There are differences in the transit of fluid- and solid-phase marker in pigs. Fluid-phase markers appear earlier than solid markers. Monitoring the evacuation of fluid-phase dye using video surveillance is difficult. Using plastic markers and x-rays to estimate the segmental and oral-rectal transit times in young pigs may be a useful method that can be correlated to oral-rectal transit studies performed in humans. The ability of pigs to hold solids in the stomach for extended times complicates transit studies. There are some differences in transit in pigs from different breeders. [ABSTRACT FROM AUTHOR]

A leachbed is a relatively simple anaerobic digester suitable for high-solids residues and on-farm applications. However, performance characteristics and optimal configuration of leachbeds are not well-understood. In this study, two 200 L pilot-scale leachbeds fed with spent straw bedding from pigs/swine (methane potential, B 0 = 195–218 L CH 4 kg −1 VS fed ) were used to assess the effects of leachate recirculation mode (trickling vs. flood-and-drain) on the digestion performance. Results showed comparable substrate solubilisation extents (30–45% of total chemical oxygen demand fed) and methane conversion (50% of the B 0 ) for the trickling and flood-and-drain modes, indicating that digestion performance was insensitive to the mode of leachate flow. However, the flood-and-drain leachbed mobilised more particulates into the leachate than the trickling leachbed, an undesirable outcome, because these particulates were mostly non-biodegradable. Inoculation with solid residues from a previous leachbed (inoculum-to-substrate ratio of 0.22 on a VS basis) hastened the leachbed start-up, but methane recovery remained at 50% of the B 0 regardless of the leachate recirculation mode. Post-digestion testing indicated that the leachbeds may have been limited by microbial activity/inhibition. The high residual methane potential of leachate from the trickling (residual B o = 732 ± 7 L CH 4 kg −1 VS fed ) and flood-and-drain leachbeds (582 ± 8 L CH 4 kg −1 VS fed ) indicated an opportunity for further processing of leachate via a separate methanogenic step. Overall, a trickling leachbed appeared to be more favourable than the flood-and-drain leachbed for treating spent bedding at farm-scale due to easier operation. [ABSTRACT FROM AUTHOR]

Click chemistry is an approach that uses efficient and reliable reactions, such as Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC), to bind two molecular building blocks. CuAAC has broad applications in medicinal chemistry and other fields of chemistry. This review describes the general features and applications of CuAAC in solid-phase synthesis (CuAAC-SP), highlighting the suitability of this kind of reaction for peptides, nucleotides, small molecules, supramolecular structures, and polymers, among others. This versatile reaction is expected to become pivotal for meeting future challenges in solid-phase chemistry. [ABSTRACT FROM AUTHOR]