Thermal stability and cross-linking of Hb New York [beta 113(G15)Val----Glu]

Hb New York [beta 113(G15)Val----Glu] has been cross-linked with bis (3,5-dibromosalicyl) fumarate, a reagent known to cross-link Lys 82 beta 1 and Lys 82 beta 2. Thermal denaturations of met Hb New York and its derivative have been compared to those of the corresponding Hb A samples. The structural transitions, observed as absorbance changes at 418 nm, were at 40.2 degrees C for Hb New York, 42.2 degrees C for Hb A, 53.7 degrees C for cross-linked Hb New York, and 56.2 degrees C for cross-linked Hb A. Transitions observed at 280 nm were approximately 2 degrees C higher. Thus, a single inter-subunit cross-link can stabilize an abnormal hemoglobin. A model of Hb New York in which Glu beta 113 forms a salt bridge to His beta 117 can explain the small changes in both the stability and the electrophoretic mobility of this protein.