Effect of cross-linker length on the stability of hemoglobin.

A series of cross-linking reagents with 4 to 7 carbons have been synthesized and used to modify human hemoglobin. The product yields and biochemical properties of these cross-linked hemoglobins are compared to those made with both longer and shorter cross-linkers. Several trends become apparent. The yields decrease as the cross-linker becomes longer, which correlates well with molecular dynamics studies of reagent binding pathways presented here. The autooxidation rates increase while thermal stability decreases with longer reagents. Cross-linking under deoxy conditions also increases autooxidation rates, but the effect is less than that of increased cross-linker length. The results suggest that shorter reagents may provide better-stabilized tetramers for the construction of more complex hemoglobin-based oxygen carriers.