Lectins are proteins with multivalent carbohydrate-binding sites, which confer the ability to agglutinate. The seeds of legumes are particularly rich in lectins, for example, concanavalin A (Con A) comprises up to 15% of the protein in the cotyledons of jack bean (Canavalia ensiformis) seeds. The amino acid sequences of Con A and several other legume lectins have been partially or fully determined, and comparison of these sequences from different species reveals a circular homology (Fig. 1A); rearrangements within the genome have been suggested to explain this. We report here that the circular homology displayed by Con A is due to a post-translational transposition and ligation within the initial polypeptide. This type of modification has not been reported previously for eukaryotes, although it has been suggested to occur in bacteriophage lambda.

No abstract

No abstract

This contribution concerns the issue of crystal nucleation in the polymorphic and hydrate forming system inosine-water. A combination of computational and experimental tools have been used to explore the relationship between solution phase inosine species and the structural synthons as found in its crystal structures. It is evident that the initial nucleation of a metastable polymorph at temperatures above 10 degrees C is directed by dimeric self-association as revealed through proton NMR. At lower temperatures a dihydrate structure becomes the most stable solid phase and in this region of the phase diagram this is the only form that appears even though the solution species remain unchanged. This can only be rationalised in terms of a combination of water binding to the solution dimers and the thermodynamic stability of the hydrate crystal structure.

No abstract