Thermal Stability and Cross-Linking of HB New York [β113(G15)VAL→GLU]

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Abstract
Hb New York [.beta.113(G15)Val.fwdarw.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.degree. C for Hb New York, 42.2.degree. C for Hb A, 53.7.degree. C for cross-linked Hb New York, and 56.2.degree. C for cross-linked Hb A. Transitions observed at 280 nm were approximately 2.degree. 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.