Side chain crosslinking reaction

Side-chain crosslinked helices obtained from an olefin metathesis reaction were first described by Blackwell and Grubbs [110], and more recently by Schafmeister and Verdine [70]. These researchers carefully examined linker length and stereochemistry to arrive at the optimal design. The hydrocarbon-stapled helices were subsequently shown to target antiapoptotic proteins HDM2 and Bcl-2 BH3 domain proteins in cell culture and animal models [37, 111]. The hydrocarbon linker was employed because it was expected to be chemically more stable than linkers built from amide or disulfide bonds but, significantly, these hydrocarbon-stapled helices have also shown an increased tendency to penetrate cell membranes, possibly due to the lipophilic nature of the linker. Debnath and... 

Chemical modification refers to the modification process in which chemical reactions occur between the backbone, branched chain, and side chain of a macro-molecular chain. The modification principle depends mainly on the structural changes of the main chain, branched chain, or side chain. Chemical modifications include copolymerization between different monomers, grafting reaction of macromolecular chains, crosslinking reaction within macromolecular chains, functional group reactions on the macromolecular chains, and so forth. For example. 

Fluorosilicones consist of PDMS backbones with some degree of fluoro-aliphatic side chains. The fluorinated group can be trifluoropropyl, nonafluorohexylmethyl, or fluorinated ether side group [78,28,79]. These polymers differ not only in substituent group, but also in the amount of fluoro-substitution relative to PDMS, the overall molecular weight and crosslink density, and the amount of branching. In most commercially available cases, these polymers are addition cure systems and the reactions are those discussed previously for silicone networks. 

From the data of DTA and TGA analyses illustrated in Fig. 4, its evident that the visible exo-peaks in the range of 140-150°C appear in DTA curves (Fig. 4a), which can be taken as evidence of a crosslinking reaction of acylated macromolecules at the expense of side chain... 

The inhibition of C a2+-ATPase at the active site by ATP-Im or ADP-Im with the participation of Ca2+ is illustrated by the following model. In the reaction of ATP-imidazolide with the carboxylate of Asp 351, a mixed anhydride is formed with the aspartate residue, followed by presumably nucleophilic attack of a lysine side chain, thereby displacing the nucleotide and leading to an intramolecular crosslink.[1]... 

Figure 28.21 The reactions of R u (11) pby 3 + are catalyzed by light at 452 nm that begins by forming an excited state intermediate. In the presence of persulfate, a sulfate radical is formed concomitant with the oxidative product Ru(III)bpy33+. This form of the chelate is able to catalyze the formation of a radical on a tyrosine phenolic ring that can react along with the sulfate radical either with a nucleophile, such as a cysteine thiol, or with another tyrosine side chain to form a covalent linkage. The result of this reaction cascade is to cause protein crosslinks to form when a sample containing these components is irradiated with light.

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