Axispharm offers you high-purity 9-aminononanoic acid, an alkane chain with terminal carboxylic acid and amine groups, that can be used as a PROTAC linker. Amino groups (NH2) react with carboxylic acids, activated NHS esters, carbonyl groups (ketones, aldehydes), etc. Terminal carboxylic acids can react with the primary amine groups of activated NHS esters to form stable amide bonds.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.