[reaction: see text] A new, simple and efficient immobilization method to attach mono-, di-, oligo-, and polysaccharides to hydrazide-coated glass slides was developed. Protein and cell-binding experiments show that the carbohydrate microarrays prepared by this method are applicable for the rapid analysis of protein-carbohydrate interactions and fast detection of pathogens.

Carbohydrate-protein interactions play important biological roles in living organisms. For the most part, biophysical and biochemical methods have been used for studying these biomolecular interactions. Less attention has been given to the development of high-throughput methods to elucidate recognition events between carbohydrates and proteins. In the current effort to develop a novel high-throughput tool for monitoring carbohydrate-protein interactions, we prepared carbohydrate microarrays by immobilizing maleimide-linked carbohydrates on thiol-derivatized glass slides and carried out lectin binding experiments by using these microarrays. The results showed that carbohydrates with different structural features selectively bound to the corresponding lectins with relative binding affinities that correlated with those obtained from solution-based assays. In addition, binding affinities of lectins to carbohydrates were also quantitatively analyzed by determining IC(50) values of soluble carbohydrates with the carbohydrate microarrays. To fabricate carbohydrate chips that contained more diverse carbohydrate probes, solution-phase parallel and enzymatic glycosylations were performed. Three model disaccharides were in parallel synthesized in solution-phase and used as carbohydrate probes for the fabrication of carbohydrate chips. Three enzymatic glycosylations on glass slides were consecutively performed to generate carbohydrate microarrays that contained the complex oligosaccharide, sialyl Le(x). Overall, these works demonstrated that carbohydrate chips could be efficiently prepared by covalent immobilization of maleimide-linked carbohydrates on the thiol-coated glass slides and applied for the high-throughput analyses of carbohydrate-protein interactions.

Candida albicans is one of the most prevalent fungal pathogens, causing both mucosal candidiasis and invasive candidemia. Antimicrobial peptides (AMPs), part of the human innate immune system, have been shown to exhibit antifungal activity but have not been effective as pharmaceuticals because of low activity and selectivity in physiologically relevant environments. Nevertheless, studies on α-peptide AMPs have revealed key features that can be designed into more stable structures, such as the 14-helix of β-peptide-based oligomers. Here, we report on the ways in which two of those features, hydrophobicity and helicity, govern the activity and selectivity of 14-helical β-peptides against C. albicans and human red blood cells. Our results reveal both antifungal activity and hemolysis to correlate to hydrophobicity, with intermediate levels of hydrophobicity leading to high antifungal activity and high selectivity toward C. albicans. Helical structure-forming propensity further influenced this window of selective antifungal activity, with more stable helical structures eliciting specificity for C. albicans over a broader range of hydrophobicity. Our findings also reveal cooperativity between hydrophobicity and helicity in regulating antifungal activity and specificity. The results of this study provide critical insight into the ways in which hydrophobicity and helicity govern the activity and specificity of AMPs and identify criteria that may be useful for the design of potent and selective antifungal agents.

Carbohydrate microarrays have received great attention as high-throughput analytic tools in studies of carbohydrate-mediated biological processes. Most of the methods employed to fabricate glycan microarrays rely on the immobilization of modified glycans on the properly derivatized surfaces. This immobilization strategy requires the availability of modified glycans whose syntheses in many cases are time-consuming and difficult. We have developed a simple and direct immobilization technique that involves a one-step, site-specific attachment of diverse unmodified glycans to the hydrazide-derivatized glass surface. To demonstrate the generality of this direct immobilization method, we examined its use for the construction of carbohydrate microarrays containing a variety of glycans. The results of protein and cell-binding experiments indicate that the glycan microarrays, prepared by using this methodology, are applicable to the rapid evaluation of glycan-mediated biomolecular interactions and the determination of quantitative binding affinities between carbohydrates and proteins.

The biological significance of glycans in the post-genomic era requires the development of new technologies to enable functional studies of carbohydrates in a high-throughput manner. Recently, carbohydrate microarrays have been exploited as an advanced technology for this purpose. Efficient immobilization methods for carbohydrate probes on the proper surface are essential for the successful fabrication of carbohydrate microarrays. Up to date, several techniques have been developed to attach simple or complex carbohydrates to a solid surface. The developed glycan microarrays have been applied for functional glycomics, drug discovery, and diagnosis. In this concept article, we discuss the progress of immobilization methods of carbohydrates on solid surfaces, their potential uses for biological research and biomedical applications, and possible solutions for some remaining challenges to improve this new technology.