2XKH:
reference: Ligand migration in the apolar tunnel of cerebratulus lacteus mini-hemoglobin., Pesce A, Nardini M, Dewilde S, Capece L, Marti MA, Congia S, Salter MD, Blouin GC, Estrin DA, Ascenzi P, Moens L, Bolognesi M, Olson JS, J Biol Chem. 2010 Dec 7. PMID: 21147768

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