Acid-labile hydrazone linkage

An acid-labile linker of c/ -aconityl or hydrazone between DOX and HPMA was synthesized to release the drug in the endosomes and lysosomes after endocy-totic uptake of the conjugate. Hydrolysis of the linkage occurs at weak acidic pH therefore, the release of DOX at plasma pH is insignificant. The in vivo activity of the acid-sensitive conjugate was significantly enhanced in comparison with free DOX and PKl. ... 

An elegant and efficient label-free method of enrichment of HNE-modified peptides by SPH chemistry utilizes reversible hydrazide chemistry to selectively capture and then release HNE-modified peptides from within complex mixtures [5], as shown in Scheme 2.2. In this strategy, HNE-modified peptides are captured on hydrazide-coated glass beads via the formation of covalent hydrazone linkage between the hydrazide group immobilized on the solid support and the aldehyde group in the modified peptides facilitating their selective enrichment. The hydrazone bond is acid labile and, hence, the modified peptides can be easily recovered from the SPH beads under acidic conditions. 

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