Studies by small-angle X-ray scattering of the quaternary structure of the 24-S component of the haemocyanin of Astacus leptodactylus in solution.

The haemocyanin of Astacus leptodactylus was studied in several buffers at three pH values. The best stability and lowest mean deviation on repeating the measurements were found at pH 7.2 in a Tris-HCl buffer. The following molecular parameters were determined: radius of gyration 6.90 nm, radius of gyration of the cross-section 3.87 nm, maximum dimension 21.5 nm, relative molecular mass 854000, volume 1440 nm3, hydration 0.27 g H2O/g protein. The theoretical scattering curves of a large number of models were calculated to find one fitting these data and the experimental scattering curve. The model with the best agreement was compared with an electron micrograph.