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Affinity Labeling
Published in Roger L. Lundblad, Chemical Reagents for Protein Modification, 2020
Photoaffinity labels have become extremely popular. These reagents are essentially unreactive until exposed to light, whereupon the active species is generated (i.e., a nitrene is formed from an azide) which then reacts instantaneously with a variety of groups. Particular attention must be paid to photolysis rate and solvent conditions. As noted by DeTraglia and co-workers,90 characterization of the rate(s) of photolysis vs. wavelength of irradiation provides useful information to control photoaffinity labeling (see Figures 28 and 29). Another potential problem in the use of aryl azides is the ease of reduction to the corresponding amine with a mild reducing agent such as dithiothreitol.91 Selected examples of affinity labels are given in Table 2.
Affinity Modification — Organic Chemistry
Published in Dmitri G. Knorre, Valentin V. Vlassov, Affinity Modification of Biopolymers, 1989
Dmitri G. Knorre, Valentin V. Vlassov
Arylazides with electron-withdrawing substituents absorb at 300 to 450 nm (E − 5 • 103M−1 cm−1). Use of other types of carbene and nitrene precursors122 is limited due to disadvantages related to insufficient stability, inappropriate photochemical properties (require short wavelength UV light for activation), or the tendency to rearrange to inactive compounds or species which are consumed in the light-independent reactions.
Affinity Labeling
Published in Roger L. Lundblad, Claudia M. Noyes, Chemical Reagents for Protein Modification, 1984
Roger L. Lundblad, Claudia M. Noyes
Photoaffinity labels have become extremely popular. These reagents are essentially un-reactive until exposed to light, whereupon the active species is generated (i.e., a nitrene is formed from an azide) which then reacts instantaneously with a variety of groups. Particular attention must be paid to photolysis rate and solvent conditions. As noted by DeTraglia and co-workers,60 characterization of the rate(s) of photolysis vs. wavelength of irradiation provides useful information to control photoaffinity labeling (see Figures 23 and 24). Another potential problem in the use of aryl azides is the ease of reduction to the corresponding amine with a mild reducing agent such as dithiothreitol.61 Selected examples of affinity labels are given in Table 2.
Biomedical applications and toxicities of carbon nanotubes
Published in Drug and Chemical Toxicology, 2022
Shiv Kumar Prajapati, Akanksha Malaiya, Payal Kesharwani, Deeksha Soni, Aakanchha Jain
In the covalent method, several chemical tactics have been developed for the formation of a variety of chemical bonds over the surface of CNTs either at the sidewalls or at the end. Covalent bonding is formed between functional entities and carbon skeleton present in CNT. This aims to enhance the CNTs dispersion, which increases wetting or adhesion characteristics and diminishes agglomeration (Koval’chuk et al.2008). The covalent approach can be categories in two ways: direct covalent sidewall functionalization and indirect chemical modification (Amiri et al.2011). Functionalization with chemicals involves amidation (Balas et al.2016); oxidation (Spinato et al.2016), halogenation (bromination, chlorination, and fluorination) (Rastogi et al.2014); hydrogenation (Silambarasan et al.2017); thiolation (Komane et al.2018); addition of radicals (Rodríguez-Jiménez et al.2016); carbenes (Yu et al.2008); nitrene (Holzinger et al.2003); etc. The covalent functionalization of CNTs produces sp3 hybridization on the carbon sites and blocks the transitions of π-electrons without altering its texture (Shinde et al.2015). However, the covalently conjugated drug with carrier has benefits of high drug loading as the drugs selected usually containing free amine or carboxylic group. Nonetheless, it also has some concerns like slow drug release and conjugation may result in drug being completely ineffective. In a study conducted by Sahoo et al. (2011), three different types of chemical functional groups were introduced namely, amino-phenyl (C6H4NH2), benzoic acid (C6H4COOH), and nitro-phenyl (C6H4NO2) on the sidewalls of MWCNTs (Rasheed et al.2006). The purpose of the study was to check compatibility with liquid crystalline polymer (LCP). An investigation was done on effect of electron withdrawing and donating groups. It was found that amino-phenyl (C6H4NH2) showed the highest intermolecular interaction between multiple wall CNTs (MWCNTs) and LCP. These interactions improved the mechanical and rheological properties of CNTs (Sahoo et al.2011).