We report on the first measurement of the spin-dependent structure function g1d of the deuteron in the deep inelastic scattering of polarised muons off polarised deuterons, in the kinematical range 0.006

No abstract

In order to get an idea of the possible neutron small-angle scattering experiments with solutions of macromolecules at the high-flux reactor of the Institut Max von Laue-Paul Langevin at Grenoble, aqueous solutions of molecules with molecular weights from about one hundred to several millions have been studied. Changing the contrast by using different HzO/D20 mixtures the basic scattering functions could be determined. Zero-angle scattering from neutron and X-ray small-angle scattering experiments are compared. In the case of ferritin the molecular-weight distribution could be determined from the dependence of zero-angle scattering on the solvent. A considerable variation of the square of the radius of gyration R at low contrast ~ was observed. R 2 turned out to be a linear function of 1/~. The slope of the straight line is a measure of the homogeneity of the internal structure. Proton-deuteron exchange reactions have been studied. A time resolution of less than two seconds had been reached with myoglobin and other globular proteins.

The problem of uniqueness of the low-resolution shape determination from small-angle scattering by isotropic monodisperse systems is considered. The particle shape is represented by the envelope function parameterized using spherical harmonics as described in a previous paper [Svergun & Stuhrmann (1991). Acta Cryst. A47, 736-744]. Computer simulations are made on the model bodies with sharp boundaries exactly represented by spherical harmonics. If the number of independent parameters describing the shape is 1 to 1.5 times the number of Shannon channels covered by the data set, the shape restoration is found to be unique and stable with respect to the random and systematic errors. The resolution limits of the straightforward shape determination are connected to the computational accuracy of the model intensities; with current algorithms, shapes described by 15 to 20 independent parameters can be uniquely determined. The results form a basis for an ab initio low-resolution shape determination in terms of spherical harmonics.

Small‐angle scattering studies on biological structures provide low‐resolution models. More detailed models need a more elaborate analysis in order to show their uniqueness. The representation of small‐angle scattering of both in Cartesian coordinates and polar coordinates is discussed. The degree of non‐uniqueness of structural analysis is best presented in terms of a multipole expansion. Contrast variation leads to the evaluation of the basic scattering functions Jc(κ), Jcs(κ) and Js(κ), which add useful constraints to a model. The experimental aspects of this method in both X‐ray and neutron scattering are discussed. Furthermore, isomorphous (or isotopic) replacement of parts of macromolecular structures have been very useful in structure determination of ribosomes. Kinetic investigations of solutions in the subsecond region have been performed so far only for the investigation of H–D exchange with some proteins. Small‐angle scattering from fibrous and lamellar systems received a considerable impact from a combined use of X‐ray and neutron scattering, as is shown for collagen. Structural changes during active muscle contraction have been investigated both with classical X‐ray equipment and with synchrotron radiation.