This afternoon I started working on an illustration to go with a research highlight for the Functional Glycomics Gateway newsletter, published by Nature Publishing Group in collaboration with the Consortium for Functional Glycomics. One of the articles they're highlighting this month is about an anti-angiogenic peptide called Anginex that binds to the galactose-binding lectin Galectin-1. Through an unknown mechanism, which the data suggests does not involve multivalency, this binding event leads to a several-fold increase in the binding affinity of Galectin-1 to its carbohydrate ligands. There is a crystal structure of Galectin-1, an NMR solution structure of Anginex, and a rough idea of where the peptide docks onto Galectin-1, but the details of the interaction, and how it affects carbohydrate binding, are still unknown.
So, how do I draw it? Well, simply, for starters, because it's only a small spot illustration. Above are some thumbnails I did while thinking through it. Since I don't know exactly where Anginex goes or in what orientation, I thought I'd try using typography to illustrate the effect it has on Galectin-1 binding. First I tried having it sort of wrap around the protein, ostensibly squeezing the lectin so that it would clamp down tighter on the carbohydrate. But that seemed too suggestive of a mechanism that is almost certainly not grounded in any sort of reality. Playing around with the letters I realized that the A in Anginex could be shaped into the head of an equilibrium arrow to show how the peptide perturbs the on/off equilibrium, a much more likely scenario. I'm all for using metaphors, but I do try to keep the misleading ones to a minimum.