1. 1. The radular myoglobin of the Brazilian sea hare, Aplysia brasiliana, has been isolated and its ligand binding properties have been characterized. The myoglobin is similar to the myoglobin of Aplysia limacina (a Mediterranean species), and has a lower oxygen affinity than does myoglobin of the sperm whale, Physeter macrocephalus. 2. 2. Aplysia brasiliana myoglobin is a monomer and binds oxygen and other heme ligands non-cooperatively. There is no evidence of pH sensitivity in these processes. 3. 3. The kinetics of ligand binding and dissociation are simple processes. The lower oxygen affinity of Aplysia brasiliana myoglobin relative to sperm whale myoglobin is associated with a much higher rate of oxygen dissociation, with first order rate constants of 125 sec-1 and 10 sec-1 respectively. © 1978.612223226Anderson, Brunori, Weber, Fluorescence studies of Aplysia and sperm whale apomyoglobins (1970) Biochemistry, 24, pp. 4723-4729Antonini, Brunori, (1971) Hemoglobin and Myoglobin in their Reactions with Ligands, , North Holland, AmsterdamBlundell, Brunori, Curti, Bolognesi, Coda, Fumagalli, Ungaretti, Crystallization and preliminary X-ray diffraction studies on met-myoglobin from Aplysia limacina (1975) J. molec. Biol., 97, pp. 665-666Bonaventura, Sullivan, Bonaventura, Effects of pH and anions on functional properties of hemoglobin from Lemur fulvus fulvus (1974) J. blol. Chem., 249, pp. 3768-3775Brunori, Antonini, Fasella, Wyman, Fanelli, Reversible thermal denaturation of Aplysia myoglobin (1968) J. molec. Biol., 34, pp. 497-504Brunori, Ughetta, Rotilio, Antonini, Wyman, Redox equilibrium of sperm-whale myoglobin, Aplysia myoglobin, and Chironomus thummi hemoglobin (1971) Biochemistry, 10, pp. 1604-1609Brunori, Giacometti, Antonini, Wyman, Denaturation of Aplysia myoglobin. Equilibrium study (1972) J. molec. Biol., 63, pp. 139-152Giacometti, Da Ros, Antonini, Brunori, Equilibrium and kinetics of the reaction of Aplysia myoglobin with azide (1975) Biochemistry, 14, pp. 1584-1588Guiseppe, Calabrese, Giacometti, Brunori, An electron paramagnetic resonance study of Aplysia myoglobin (1971) Biochimica et Biophysica Acta (BBA) - Protein Structure, 236, pp. 234-237Perutz, Three-dimensional Fourier synthesis of horse oxyhaemoglobin at 2.8 Å resolution: (1) X-ray analysis (1968) Nature, Lond., 219, pp. 29-32Riggs, Wolbach, Sulphydryl groups and the structure of hemoglobin (1956) The Journal of General Physiology, 39, pp. 585-605Rossi-Fanelli, Antonini, A new type of myoglobin isolated and crystallized from the muscles of Aplysiae (1957) Biochemia (URSS), 22, pp. 344-355Rossi-Fanelli, Antonini, Povoledo, Further study on myoglobin II. Chemical and biochemical properties of a new type of myoglobin in molluscs, in Neuberger, A (1960) Symposium on Protein Structure, pp. 143-147. , Methuen, LondonSekino, Ogo, Montouchet, Focesi, Jr., Denaturation of Aplysia brasiliana myoglobin (1976) Tenth International Congress of Biochemistry, p. 169. , Abstract volumeTakano, Structure of myoglobin refined at 2.0 Å resolution. I. Crystallographic refinement of metmyoglobin for sperm whale (1977) J. molec. Biol., 110, pp. 537-568Takano, Structure of myoglobin refined at 2.0 Å resolution. II. Structure of deoxymyoglobin from sperm whale (1977) J. molec. Biol., 110, pp. 569-584Tentori, Vivaldi, Carta, Marinucci, Massa, Antonini, Brunori, Amino acid sequence of Aplysia limacina myoglobin (1973) Int. J. Peptide Protein Res., 5, pp. 187-200Wittenberg, Brunori, Wittenberg, Wyman, Kinetics of the reactions of Aplysia myoglobin with oxygen and carbon monoxide (1965) Archs Biochem. Biophys., 111, pp. 576-579