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R Lontie

Publications and source records attributed to R Lontie.

At least 37 records · Page 2Linked to original sources
PubMed1977

Studies by small-angle X-ray scattering of the quaternary structure of the beta-haemocyanin of Helix pomatia.

Helix pomatia beta-haemocyanin was studied in solution by small-angle X-ray scattering. The following molecular parameters were determined: molecular weight = 9.02 X 10(6), volume = 14000 nm3, radius of gyration = 18.4 nm, radius of the spherical subunits = 2.5 +/- 0.2 nm. With these data, and with information of dissociation products described in a former paper, a model of the molecule was built whose theoretical scattering curve showed good agreement with the experimental one. The model consists of 160 spherical subunits of a radius of 2.5 nm; 12 rings each built up of 10 spheres form the outer wall of a hollow cylinder; 20 subunits are situated at the inner side of each end.

Animals↗
PubMed1977

Studies by small-angle x-ray scattering of the quaternary structure of dissociation products of the beta-haemocyanin of Helix pomatia.

Helix pomatia beta-haemocyanin was split into dissociation products by varying the pH and the ionic strength. The purity of the solution was checked in an ultracentrifuge. Two defined dissociation products were studied in solution by small-angle X-ray scattering. In Tris-HC1 buffer, pH 8.0 and ionic strength 1 M, the following parameters of the dissociation product (tenths) could be determined: molecular weight = 7 x 10(5), volume = 1350 nm3, radius of gyration = 9.0 nm, maximal distance = 28.3 nm, radius of the spherical subunits about 2.6 nm, number of the subunits approximately 19. Tris-HC1 buffer, pH 8.7 and ionic strength 0.01 M, yielded dissociation products (twentieths) with the following parameters: molecular weight = 3.5 x 10(5), volume = 635 nm3, radius of gyration = 7.5 nm, maximal distance = 21.9 nm, radius of the spherical subunits about 2.5 nm. With this information, the assumption that the larger fragment was double the smaller one and the latest biochemical and morphological results, theoretical scattering curves of models were calculated and compared with the experimental curves. Two models are suggested which argee well with the dissociation products in radius of gyration and scattering.

Animals↗
PubMed1976

Differential hydrogen ion titrations of the histidine residues in Helix pomatia haemocyanin.

The properties of the histidine residues in Helix pomatia haemocyanin have been studied by differential hydrogen ion titrations. In oxy-and deoxyhaemocyanin 31 X 10(-5) histidine residues per g protein are titrated in contrast to 35 X 10(-5) residues in apohaemocyanin. The difference corresponds to a stoichiometry of one histidine residue per copper atom bound. Even in apohaemocyanin about 6 X 10(-5) histidine residues per g protein are not titrated in their normal pH region. In the presence of sufficient calcium to displace the dissociation completely out of the titration region, the titration curve of apohaemocyanin could be linarized according to the model of Linderstrom--Lang. In oxy-and deoxyhaemocyanin, however, a distinct deviation from linearity was found under the same conditions. In the absence of calcium the effect of the dissociation adds up to this deviation. The electrostatic interaction factors were determined for the protein at 0.1 M KC1 and for the dissociation products: halves and tenths at 1.0 M KC1. The electrostatic interaction factor for the wholes and the halves are much smaller than the values calculated from the Linderstrom--Lang equation, using the radius of the equivalent sphere either obtained from electron microscopy or from the partial specific volume. This probably due to solvent penetration. For the tenths at 1.0 M KC1, this effect is small.

Animals↗
PubMed1975

Limited trypsinolysis of beta-haemocyanin of Helix pomatia. Characterization of the fragments and heterogeneity of the copper groups by circular dichroism.

A limited trypsinolysis of the tenths of beta-haemocyanin of Helix pomatia was performed at pH 8.2. The absorbance at 346 nm remained constant, indicating a preservation of the oxygen-binding sites. The five tryptic fragments were separated by chromatography on Sephadex G-100 and on DEAE-cellulose. They contained 2 Cu per 50000 daltons and showed different mobilities in agar electrophoresis. The molecular weights indicated that one fragment was constituted of three functional domains of about 50000 daltons, that two fragments were constituted of two domains, and two others of one domain. Twentieths of beta-haemocyanin seemed thus to be made up of 9 domains. The circular dichroic spectra of the fragments indicated the presence of two classes of copper groups according to their positive maximum at 455 or at 500 nm. The circular dichroic spectra also showed that no fragment could have originated from a larger one, confirming the presence of nine domains in the twentieths.

Animals↗