China
Africa
Explore chapters and articles related to this topic
Facile Chemical Fabrication of Designer Biofunctionalized Nanomaterials
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials I, 2020
Nanoparticles with carboxyl groups can be readily bonded covalently to biomolecules bearing primary amine groups though carbodiimde chemistry. Carbodiimide coupling agents commonly used are a zero-length crosslinking agent, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N, N’-dicyclohexylcarbodiimide (DCC), used along with the solvent dimethylformamide (DMF) (Grabarek and Gergely, 1990). These carbodiimdes are popular crosslinking agents because of their high water solubility and the ease of removal of excess reagents and by-products. As the reactive ester rapidly formed hydrolyzes in aqueous solution, the coupling reaction is carried out in the presence of N-hydroxysuccinimide (NHS) or N-hydroxysulfosuccinimide (sulfo-NHS). NHS or sulfo-NHS reacts with carboxylic groups to form an active intermediate ester and further assist in amide-bond formation in the presence of EDC (Figure 2.3). General schematic representation of biofunctionalization of NPs demonstrated by the use of a protein. (a) Assembly of NP-protein by electrostatic interaction, (b) Formation of nanoparticle-protein bioconjugate by affinity interaction using streptavidin–biotin binding, or (c) Antigen-antibody interaction, (d) Adsorption of nanoparticle-protein mediated via sulfhydryl group of cysteine amino acid, (e) Carboxylate–amine coupling of carboxylated nanoparticle and amine group presented by lysine amino acid in protein. NHS/EDC coupling agents are used during covalent coupling, (f) Click chemistry reaction with azide-tagged nanoparticle and protein with alkyne tail.
Enzyme immobilization as a sustainable approach toward ecological remediation of organic-contaminated soils: Advances, issues, and future perspectives
Published in Critical Reviews in Environmental Science and Technology, 2023
Litao Wang, Xuran Du, Ying Li, Yuhong Bai, Teng Tang, Jing Wu, Hong Liang, Dawen Gao
Compared with physical immobilization, covalent binding usually exhibits excellent thermal stability, reusability, and less leaching (Sheldon & van Pelt, 2013). Covalent binding refers to the method of the binding enzyme to the carrier in covalent bonds (Cesar et al., 2007). The chosen carriers are generally chemically modified sugar-based gels, amino acid copolymers with the azide method (Akhtar et al., 2012), cyanogen bromide method (Homaei, 2015), and dicyclohexylcarbodiimide method (Raghvendra Ashok et al., 2015). Enzyme proteins can provide active cross-linking groups, which mainly include the amino group of lysine/arginine, the carboxyl group of the aspartic acid/glutamic acid, and the sulfhydryl group of cysteine, the hydroxyl group of tyrosine/serine, the imidazole group of histidine, the indole group of tryptophan. Laccase was immobilized on polyacrylonitrile nanofiber membrane by amidation reaction of ethanol/HCl, and more than 85% of 2,4,6-trichlorophenol in water could be removed (Ran et al., 2013). After 18 d of storage, immobilized laccase retains 92% of its initial enzyme activity, while free laccase retains 20%. Additionally, by covalently immobilizing laccase on polyvinyl alcohol/chitosan/multi-walled carbon nanotubes composite nanofibrous membrane with aldimine condensation, enzyme loading (907 mg/g) and enzyme activity (76.7%) were significantly higher than in free laccase (862 mg/g and 63.5%) (Ran et al., 2014). Despite its strong binding properties on laccase and carrier, this method is complex to prepare, and it has a high rate of enzyme inactivation under harsh conditions.
New Schiff’s base cinnamates/benzoates liquid crystals with lateral methyl substitutes: characterisation, mesomorphic behaviour and DFT calculation
Published in Liquid Crystals, 2022
Rohit R. Koshti, Akshay Vyas, Kaushik A. Patel, Hardik S. Patel, Madhur B. Patel, H. N. Patel
2-methylaniline, Nitric acid, Sulphuric acid, concentrated hydrochloric acid, 4-Hydroxybenzaldehyde, the appropriate n-alkyl halides, anhydrous potassium carbonate, dry acetone, ethyl acetate, Dry Pyridine, Pipyridine, Malonic acid, 4-hydroxybenzoic acid, Potassium hydroxide, Ethyl alcohol, glacial acetic acid, N,N′-Dicyclohexylcarbodiimide (DCC), 4-Dimethylaminopyridine (DMAP) and tetrahydrofuran (THF) were used as received. Distillation and drying of the solvent were done before using them. Infrared (IR) spectra were collected on Shimadzu IR-408 spectrophotometer using potassium bromide (KBr) pellets. Proton nuclear magnetic resonance (1H-NMR) spectra were obtained on a Bruker Avance Neospectrometer (400 MHz) using tetramethyl silane (TMS) as an internal reference. The chemical shifts are quoted as δ (ppm) downfield from the internal reference; Deuterated chloroform (CDCl3) was used as a solvent for all the compounds. The phase assignments and transition temperatures were determined by thermal polarising optical microscopy by means of polarising microscope (Leitz Laborlux 12 POL) equipped with a heating stage. Differential scanning calorimeter (DSC) Shimadzu DSC-60 plus system with a heating rate of 10°C min−1 was used to determine the enthalpies of transitions and reported in kJ.mol−1. The instrument was calibrated with pure indium as a standard.
Molecular packing handedness dominated by the chirality of the lactic acid residue near the liquid crystalline core
Published in Liquid Crystals, 2021
Xiaoqing Wu, Baining Ni, Limin Wu, Yongmin Guo, Yi Li, Baozong Li, Yonggang Yang
The synthetic route for (R,R)-3 and the molecular structures of (R,S)-3, (S,R)-3 and (S,S)-3 is shown in Scheme 1. 4-Perfluorooctylbenzoic acid was synthesised by copper catalysed coupling of perfluorooctyl iodide with 4-iodobenzoic acid [38]. The intermediates with two lactate residues were also synthesised according to the literature [32]. After removing the benzyl group, compound (R,R)-D was obtained. The final liquid crystals were synthesised through a N,N-dicyclohexylcarbodiimide/4-dimethylaminopyridine (DCC/DMAP) approach in tetrahydrofuran (THF) and purified by recrystallisation in a mixture of acetone/methanol. The series of 4s was also synthesised according to similar procedure using 4-perfluorohexylbenzoic acid as the starting material. Moreover, the molecular structures of the series 2 were also shown in Scheme 1 [32].