The present invention provides a method for stabilizing a protein in a desired conformation by introducing at least one disulfide bond into the polypeptide. Computational design is used to identify positions where cysteine residues can be introduced to form a disulfide bond in only one protein conformation, and therefore lock the protein in a given conformation. Accordingly, antibody and small molecule therapeutics are selected that are specific for the desired protein conformation. The invention also provides modified integrin I-domain polypeptides that are stabilized in a desired conformation. The invention further provides screening assays and therapeutic methods utilizing the modified integrin I-domains of the invention.