MOTIVATION: Sequencing glycan structures is a difficult problem that requires the use of multiple experimental approaches. One powerful approach to glycan sequencing is the combination of liquid chromatography with sequential exoglycosidase digestions; however, interpreting this can be difficult and time-consuming. To aid this process, we introduce GlycoProfileAssigner, software for automated structural assignment of glycan profile data from liquid chromatography experiments. RESULTS: GlycoProfileAssigner has been tested on human IgG data, and can retrieve the correct structure in 14 out of 16 peaks tested. AVAILABILITY AND IMPLEMENTATION: The programme and its source code is available at https://bitbucket.org/fergaljd/glycoprofileassigner CONTACT: : [email protected] SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

BACKGROUND: Bioactive cyclic peptides derived from natural sources are well studied, particularly those derived from non-ribosomal synthetases in fungi or bacteria. Ribosomally synthesised bioactive disulphide-bonded loops represent a large, naturally enriched library of potential bioactive compounds, worthy of systematic investigation. RESULTS: We examined the distribution of short cyclic loops on the surface of a large number of proteins, especially membrane or extracellular proteins. Available three-dimensional structures highlighted a number of disulphide-bonded loops responsible for the majority of the likely binding interactions in a variety of protein complexes, due to their location at protein-protein interfaces. We find that disulphide-bonded loops at protein-protein interfaces may, but do not necessarily, show biological activity independent of their parent protein. Examining the conservation of short disulphide bonded loops in proteins, we find a small but significant increase in conservation inside these loops compared to surrounding residues. We identify a subset of these loops that exhibit a high relative conservation, particularly among peptide hormones. CONCLUSIONS: We conclude that short disulphide-bonded loops are found in a wide variety of biological interactions. They may retain biological activity outside their parent proteins. Such structurally independent peptides may be useful as biologically active templates for the development of novel modulators of protein-protein interactions.