Size methods neutron scattering

To determine the shape of ribosomal proteins in solution, ultracentrifugation, digital densimetry, viscosity, gel filtration, quasi-elastic light scattering, and small-angle X-ray or neutron scattering have all been used. With each technique it is possible to obtain a physical characteristic of the protein. Combining these techniques should allow the size and shape of the protein to be characterized quite well. However, the values determined in various laboratories for the same ribosomal proteins differ considerably. To help understand some of the reasons we will initially discuss each method briefly as it relates to proteins and then review the size and shape of the ribosomal proteins that have been so characterized. 

The above experimental results largely relate to spectroscopic techniques, which do not give direct information about the spatial scale of the molecular motions. The size of the spatial heterogeneities is estimated by indirect methods such as sensitivity of the dynamics to the probe size or from the differences between translational and rotational diffusion coefficients (rotation-translation paradox). It might be expected that the additional spatial information provided by neutron scattering could help to discriminate between the two scenarios proposed. 

The sizes were determined by small angle neutron scattering method (SANS), (Markovic et al., 1984). In order to interpret the SANS results, a concentric sphere model was used. A spherical homogeneous core particle of radius R and the total spherical units were taken as R2, giving the thickness of the adsorbed layer as (R2 - R,)... 

Measurement of characteristics of the emulsion droplets in concentrated media is indeed a difficult task. Some indirect methods have been used. The interfacial area and therefore the droplet size were determined by measuring the critical micelle concentration of miniemulsions [43]. Erdem et al. determined droplet sizes of concentrated miniemulsions via soap titration, which could be confirmed by CHDF measurements [44]. Droplet sizes without diluting the system can much better be estimated by small angle neutron scattering (SANS) measurements [23]. 

Indirect techniques, such as conductivity measurements and the determination of the surface tension were carried out to get more information about the surfactant distribution during the polymerization and were applied to characterize the droplet or particle sizes before and after the polymerization without diluting the system [23]. As a powerful method small angle neutron scattering experiments were applied to characterize the droplet or particle sizes before and after the polymerization without diluting the system [23]. 

The pore diameters of MFI-type zeolites are comparable to the size of many commercially important molecules, such as aromatics or linear or branched hydrocarbons [1]. Thus, the study of the difiusion of reactive molecules in the channel system of zeolite catalysts is of considerable interest for the understanding of the catalyst performance. A variety of methods has been developed and applied to the measurement of diffii-sion coefficients, amongst others gravimetric techniques [2], neutron scattering [3], NMR [4] and Frequency Response [5]. The FTIR technique offers the possibility to study sorption and sorption kinetics under conditions close to those of catalytic experiments. By the use of an IR microscope, single crystals have become accessible to the FTIR technique. 

Small-angle X-ray and neutron scattering Chemical Methods Pore morphology, roughness of pore surface, and pore size distribution 27, 28... 

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