Open AccessX‐Ray Small‐Angle‐Scattering Investigation of a Giant Respiratory Protein: Hemoglobin Tubifex tubifex
Author(s) -
Stöckel Peter,
Mayer Adalbert,
Keller Rainer
Publication year - 1973
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1973.tb02975.x
Subject(s) - scattering , tubifex tubifex , radius of gyration , gyration , molecular physics , radius , spheres , chemistry , tubifex , crystallography , physics , geometry , optics , nuclear magnetic resonance , mathematics , biology , ecology , computer security , astronomy , computer science , environmental chemistry , polymer
The quaternary structure of hemoglobin of the worm species Tubifex tubifex was investigated by X‐ray small‐angle scattering. The desmeared scattering functions were observed to be similar for oxygenated and deoxygenated species having true radii of gyration of 11.0 and 11.2nm respectively. Comparison of experimental and theoretical scattering curves gives information on the overall shape of the macromolecule in solution. What is found in this way allows the postulation of structural models of uniform electron density which are equivalent in scattering to the macromolecule studied. The experimental scattering curves were compared with scattering curves calculated for various models. The overall shape of hemoglobin Tubifex can be approximated by a hollow cylinder of outer diameter D = 26.0 nm, inner diameter d = 0.3 D and height h = 0.6 D . The scattering functions calculated for hexagonal arrangements of 12 identical spheres of radius 4.5 nm in two superposed 6‐numbered rings, correspond to the experimental scattering curves we have obtained, as well as to electron microscopic observations on hemoglobins from some Annelida . However, the calculated scattering curves of a model of 108 identical spheres arranged in 12 nonamers proposed by Yamagishi and his colleagues in 1966 provided the best simultaneous fit for the radius of gyration and for the sizes and positions of the first and second subsidiary minima and maxima. A model of outer diameter 27.3 nm, inner diameter 9.1 nm, sphere diameter 3.4 nm for the oxygenated species and 3.45 nm for the deoxygenated species and total heights of 16.2 and 16.65 nm respectively is equivalent in scattering to the quaternary structures of the hemoglobin Tubifex molecules.