The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Modelling of the serine-proteinase fold by X-ray and neutron scattering and sedimentation analyses: occurrence of the fold in factor D of the complement system.

Solution scattering is a powerful means of determining the overall arrangement of domains in the multidomain proteins of complement. the serine-proteinase domain is central to all proteolytic events during complement activation. As models of this domain, bovine beta-trypsin, trypsinogen, alpha-chymotrypsin and chymotrypsinogen A were studied by neutron and X-ray synchrotron solution scattering. At pH 7, all the X-ray and neutron M(r) values corresponded to monomeric proteins. The X-ray radii of gyration, RG, of beta-trypsin, trypsinogen, alpha-chymotrypsin and chymotrypsinogen A (measured in positive solute-solvent contrasts) were 1.59 nm, 1.78 nm, 1.71 nm and 1.76 nm (+/- 0.05-0.11 nm) in that order. Neutron contrast variation showed that the RG at infinite contrast, RC, for these four proteins were 1.57 nm, 1.70 nm, 1.67 nm and 1.78 nm (+/- 0.03 nm) in that same order. The radial inhomogeneity of neutron-scattering density, alpha, was positive at (5-13) x 10(-5), and corresponds to the preponderance of hydrophilic residues near the protein surface. On trypsinogen activation, a small reduction in the RG value of 0.13 +/- 0.07 nm was just detectable, while the RG of chymotrypsinogen A was unchanged after activation. The RC and alpha values of the four proteins can be calculated by using crystallographic co-ordinates. The reduced RG of beta-trypsin relative to trypsinogen was explained in terms of the removal of the extended N-terminal hexapeptide of trypsinogen. The full X-ray and neutron-scattering curves in positive and negative contrasts agreed well with scattering curves calculated from crystallographic coordinates to a nominal structural resolution of 4.5 nm, provided that the internal structure was considered in neutron modelling, and that the hydration was considered in X-ray modelling. Sedimentation-coefficient data also provide information on the disposition of domains in multidomain proteins. It was found that the hydrated X-ray sphere model could be directly utilized to calculate sedimentation coefficients. X-ray scattering on factor D showed from its RG of 1.78 nm that this is monomeric and very similar in structure to beta-trypsin. The X-ray-scattering curve of factor D was readily modelled using the beta-trypsin crystal structure after allowance for sequence changes. The success of these modellings provides a basis for the constrained modelling of solution scattering data for the multidomain proteins of complement.[1]


WikiGenes - Universities