 The azide side chains of L-Aha allow highly specific and efficient site-specific conjugation to a lot different of functional molecules via Staudinger ligation with phosphine reagents, and Copper (I)-catalysed azide-alkyne cycloaddition (CuAAC) or Strain promoted azide-alkyne cycloaddition (SPAAC) in click reactions.CuAAC and SPAAC are both common click reactions which are often interchangeable in click chemistry.It is well known that intracellular Cu(I) is cytotoxic, which means CuAAC is not as common as SPAAC click reactions for research leading to in-vivo applications.