a) Optro™ (rHb 1.1, deoxy). This Hb is expressed as a crossed-linked deoxy form with glycine αα linked genes on expression plasmid (Hb Presbyterian (βN108K)). b) HemAssist (DCLHb™). This Hb is chemically cross-linked at the αα subunits with bis(3.5-dibromosalicyl)fumarate. Figures were constructed using the Adobe Illustrator (Adobe Systems Incorporated, Mountain View, CA) and PyMOL Molecular Graphics System (Schrodinger, LLC, New York, NY).