Graves, B.J., Crowther, R.L., Chandran, C., Rumberger, J.M., Li, S., Huang, K.S., Presky, D.H., Familletti, P.C., Wolitzky, B.A., Burns, D.K., Insight into E-selectin/ligand interaction from the crystal structure and mutagenesis of the lec/EGF domains Nature 1994