Sulfation of the amino acid tyrosine regulates the interactions of many extracellular proteins. The proposed research will develop a novel chemical method for the preparation of peptides bearing sulfate groups on specific tyrosine residues. The method will be applied to understand the interactions between chemokines and sulfated regions of their receptors. These molecules play central roles in the control of inflammatory responses. The research will test the hypothesis that sulfation regulates the selectivity of a receptor to different chemokines and will reveal the structural basis of these interactions. The new methodology developed in this research will facilitate future studies of the biological role of tyrosine sulfation.