Thioether linkage

The importance of steric effects in determining the oxidation state of the product can be illustrated by a thioether linkage, eg (57). If a methyl group is forced to be adjacent to the sulfur bond, the planarity required for efficient electron donation by unshared electrons is prevented and oxidation is not observed (48). Similar chemistry is observed in the addition of organic nitrogen and oxygen nucleophiles as well as inorganic anions. 

In general most of the commercial polymers are not comparable to metals and ceramics in terms of load-bearing property, mechanical strength, and thermal stability. To overcome these difficulties the aromatic ether or sulfide (thioether) linkages in the polymer backbone... 

Figure 5.4 SMCC reacts with amine-containing molecules to form stable amide bonds. Its maleimide end then may be conjugated to a sulfhydryl-containing compound to create a thioether linkage.

Figure 5.9 SIAX can be used to modify amine-containing molecules to produce sulfhydryl-reactive derivatives. Subsequent reaction with a thiol compound produces a thioether linkage.

Figure 5.11 NPIA is one of the shortest heterobifunctional reagents. It reacts with amine-containing molecules through its p-nitrophenyl ester end to produce amide bonds. The iodoacetyl group then can be used to couple with thiol compounds to give stable thioether linkages.

Figure 5.12 MPBH reacts with sulfhydryl-containing molecules through its maleimide end to produce thioether linkages. Its hydrazide group then can be used to conjugate with carbonyl-containing molecules (such as periodate-oxidized carbohydrates that contain aldehydes) to give hydrazone bonds.

Figure 5.31 ASIB can react with sulfhydryl-containing molecules through its iodoacetate group to form thioether linkages. Subsequent exposure to UV light causes a ring-expansion process to occur, creating a highly reactive dehydroazepine intermediate that can couple to amine-containing molecules.

Figure 5.33 Benzophenone-4-iodoacetamide reacts with sulfhydryl-containing compounds to give thioether linkages. Subsequent photoactivation of the benzophenone residue gives a highly reactive triplet-state ketone intermediate. The energized electron can insert in active C—H or N—H bonds to give covalent crosslinks.

Dendrimer-Alkaline Phosphatase Conjugate via thioether linkage... 

The epoxy-activated dendrimer may be conjugated to thiol-containing proteins by reaction in 50 mM sodium phosphate, pH 7.2. The reaction can be done at 4°C or at room temperature for 8-16 hours to form thioether linkages. 

The iodoacetyl group of both isomers reacts with sulfhydryls under slightly alkaline conditions to yield stable thioether linkages (Figure 9.7). They do not react with unreduced disulfides in cystine residues or with oxidized glutathione (Gorman et al., 1987). The thioether bonds will be hydrolyzed under conditions necessary for complete protein hydrolysis prior to amino acid analysis. 

Figure 9.7 5-IAF can be used to modify sulfhydryl-containing molecules, creating stable thioether linkages.

Figure 9.25 DCIA can modify sulfhydryl groups through its iodoacetamide group to form thioether linkages.

BODIPY FL IA is insoluble in aqueous solution, but may be dissolved in DMF or DMSO as a concentrated stock solution prior to addition of a small aliquot to a reaction mixture. Coupling to sulfhydryl-containing molecules occurs rapidly with the formation of a thioether linkage. The reaction may be done in 50mM sodium borate, 5mM EDTA, pH 8.3. The main consideration is to protect the iodoacetyl derivative from light which may generate iodine and... 

Figure 9.35 The iodoacetamide group of this BODIPY fluorophore can react with sulfhydryl-containing molecules to form thioether linkages.

One Lucifer Yellow derivative is available for labeling sulfhydryl-containing molecules. Lucifer Yellow iodoacetamide is a 4-ethyliodoacetamide derivative of the basic disulfonate aminonaph-thalimide fluorophore structure (Invitrogen). The iodoacetyl groups react with —SH groups in proteins and other molecules to form stable thioether linkages (Figure 9.42). 

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