Meaning
An acetyl group is −COCH₃. Hydrolyzing an acetyl attached through an amide or ester bond exposes an amino (−NH₂) or hydroxyl (−OH) group. The reverse reaction is acetylation.
From chitin to chitosan
Chitin, a polysaccharide of N-acetylglucosamine, is abundant in crab and shrimp shells and insect exoskeletons. Shells are deproteinized (dilute NaOH) and demineralized (dilute HCl), then heated in 40-50% NaOH, which hydrolyzes the acetamide groups to give chitosan.
- Degree of deacetylation (DD): the fraction of units converted to amines. Above roughly 50%, the polymer dissolves in dilute acid and is called chitosan.
- Higher DD means more protonatable amines, stronger metal complexation, greater heavy-metal adsorption and antimicrobial activity.
- DD is measured by titration, FTIR or ¹H NMR.
Deacetylation in cells
Acetylated lysines on histone tails loosen chromatin and promote transcription; histone deacetylases (HDACs) remove them, compacting chromatin and silencing genes. HDAC inhibitors such as vorinostat are approved for some lymphomas. Sirtuins (e.g., SIRT1) are NAD⁺-dependent deacetylases.
References
- Rinaudo, M. (2006). Chitin and chitosan: Properties and applications. Progress in Polymer Science, 31(7), 603-632.
- Kumar, M. N. V. R. (2000). A review of chitin and chitosan applications. Reactive and Functional Polymers, 46(1), 1-27.
- Seto, E., & Yoshida, M. (2014). Erasers of histone acetylation: The histone deacetylase enzymes. Cold Spring Harbor Perspectives in Biology, 6(4), a018713.
- Guibal, E. (2004). Interactions of metal ions with chitosan-based sorbents: A review. Separation and Purification Technology, 38(1), 43-74.