Chemoselective precipitation of lactose from a lactose/sucrose mixture: proof of concept for a new separation methodology

Abstract

A new methodology for the facile isolation of biomolecules containing carbonyl groups has been developed. This methodology is based on tethering of 8-aminopyrene-1,3,6-trisulphonic acid (APTS) to a target molecule via amino or imino bonds, followed by treatment with cyclen–thiourea receptor (cyclen 1). This receptor forms an insoluble complex with APTS conjugates, and therefore precipitates these conjugates from the solution. A sucrose/lactose mixture has been used for proof of concept and lactose was successfully isolated using this procedure. Whereas labelling of lactose via reductive amination resulted in the permanent attachment of the dye to the disaccharide, the labelling via an imine bond was reversible. Additional protocol developed for the lactose labelled with APTS dye via imine bond allowed us to recover all components in their unaltered form. Such an additional protocol not only allows isolation of target molecules without their modification, but also allows one to use recovered cyclen 1 and the dye for subsequent isolation cycles.

Keywords:

• chemoselective precipitation
• reductive amination
• supramolecular chemistry
• 8-aminopyrene-1,3,6-trisulphonic acid

Acknowledgements

We thank Dr Scott Gronert for critical reading and advice. This work was supported by NSF (grant ECS-0508381) and VCU. We are grateful to an anonymous reviewer for valuable advice.