title: Light-scattering and scanning transmission electron microscopic investigation of the hemocyanin of the bivalve, Yoldia limatula (Say).
abstract: 1. The hemocyanin of the bivalve, Yoldia limatula (Say) was found by light-scattering to have a mol. wt of 8.0 +/- 0.6 x 10(6). Mass measurements by scanning transmission electron microscopy (STEM) gave a particle mass of 8.25 +/- 0.42 x 10(6) for the native particle and 4.09 +/- 0.20 x 10(6) for the half-molecule. 2. The hemocyanin subunits fully dissociated in 8.0 M urea and 6.0 M GdmCl at pH 8.0, and at pH 11.0, 0.01 M EDTA have mol. wts of 4.38 x 10(5), 4.22 x 10(5) and 4.71 x 10(5), close to one-twentieth of the parent molecular weight of Y. limatula hemocyanin and most gastropod hemocyanins. 3. Analyses of the urea dissociation transitions studied at pH 8.0, 1 x 10(-2) M Mg2+, 1 x 10(-2) M Ca2+ and pH 8.0, 3 x 10(-3) M Ca2+ suggest few hydrophobic amino acid groups, of the order of 10 to 15 at the contact areas of each half-molecule or decamer. 4. The further dissociation of the decamers to dimers and the dimers to monomers indicates the presence of a larger number of amino acid groups of ca 35-40/dimer and 100-120/monomer. 5. This suggests hydrophobic stabilization of the dimer to dimer and monomer to monomer contacts within the decamers, as observed with other molluscan hemocyanins.
authors.affiliation: Department of Chemistry, Fordham University, Bronx, NY 10458.
authors.forename: T T
authors.initials: TT
authors.lastname: Herskovits
authors.forename: M G
authors.initials: MG
authors.lastname: Hamilton
authors.forename: C J
authors.initials: CJ
authors.lastname: Cousins
authors.forename: J S
authors.initials: JS
authors.lastname: Wall
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002942:Circular Dichroism; D004492:Edetic Acid; D019791:Guanidine; D006146:Guanidines; D006433:Hemocyanins / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D008027:Light; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D008974:Mollusca / Q000032:analysis*; D012542:Scattering, Radiation; D014461:Ultracentrifugation; D014508:Urea
chemical_list: D006146:Guanidines; D046911:Macromolecular Substances; D014508:Urea; D006433:Hemocyanins; D004492:Edetic Acid; D008274:Magnesium; D019791:Guanidine; D002118:Calcium