Self-assembled monolayers with latent aldehydes for protein immobilization.

Aldehyde functions are widely used for immobilization of biomolecules on glass surfaces but have found little attention for biofunctionalization of self-assembled monolayers (SAMs) on gold, due to interference between thiol and aldehyde functions. This problem was recently solved by synthesis of an alkanethiol that carried a vicinal diol group [Jang et al. (2003) Nano Lett. 3, 691−694]. The latter served as a latent aldehyde function that was unmasked by short exposure of the vicinal diol-terminated SAM to aqueous periodate. However, the synthesis of the new vicinal diol-terminated alkane thiol was time-consuming and had an overall yield of ∼3.5%. In the present study, a general modular strategy was introduced by which SAM components with vicinal diol functions were rapidly synthesized with high yield:  this was accomplished by amide bond formation between a SAM-forming carboxylic acid (exemplified by lipoic acid and 16-mercaptohexadecanoic acid) with 3-aminopropane-1,2-diol, using suitable protecting gro...