In Vitro: KSC-34 is selective for PDIA1 over other members of the PDI family, and other cellular cysteine-containing proteins. KSC-34 contains a (4-phenylbutyl)methylamine diversity element for optimized binding to the active site of the a domain of PDIA1 with a chloroacetamide electrophile for covalent modification of C53 on PDIA1.