Receptors specific for cell-surface carbohydrates are expected to be useful in many bio-medical applications. Natural sugar-binding proteins – lectins - are highly selective for their preferred polysaccharides. Lectins have limitations however - they are costly to produce and do not always bind glycans expressed on mammalian cells. Glycans and saccharides are also weak immunogens and hence high affinity monoclonal antibodies to cell-surface glycans are rare. As boronic acids covalently bind to diols present in saccharides, they are the most widely studied artificial carbohydrates receptors.
The aim of this work is to develop “boronolectins” - synthetic lectins that are able to selectively bind polysaccharides displayed on the cell surface. To achieve our goal we combine the diol binding ability of boronic acids with the carbohydrate-binding properties of certain peptide sequences. Such a combination can lead to libraries of peptide boronic acids that show variable carbohydrate binding strength and selectivity [1-4].
In this study, we have focussed on practical methods for the preparation and assay of benzoboroxole-bearing, soluble boronolectins derived exclusively from proteinogenic amino acids. To identify sequences with favourable binding properties with mammalian sugars, we have used a high throughput alizarin-displacement assay based on the one developed by Wang [5]. The binding properties of hit sequences were then further analysed with more sensitive techniques such as isothermal titration calorimetry.