Internally folded density

B( ) is variously called the reciprocal form factor, the p-space form factor, and the internally folded density. B(s) is the basis of a method for reconstructing momentum densities from experimental data [145,146], and it is useful for the r-space analysis of Compton profiles [147-151]. The B(s) function probably first arose in an examination of the connection between form factors and the electron momentum density [129]. The B f) function has been rediscovered by Howard et al. [152]. 

Since the momentum density is related to the reciprocal form factor or internally folded density by a Fourier transform, Eq. (5.29), there are sum rules that connect moments of momentum with the spherical average of B f) defined by... 

For folded proteins, relaxation data are commonly interpreted within the framework of the model-free formalism, in which the dynamics are described by an overall rotational correlation time rm, an internal correlation time xe, and an order parameter. S 2 describing the amplitude of the internal motions (Lipari and Szabo, 1982a,b). Model-free analysis is popular because it describes molecular motions in terms of a set of intuitive physical parameters. However, the underlying assumptions of model-free analysis—that the molecule tumbles with a single isotropic correlation time and that internal motions are very much faster than overall tumbling—are of questionable validity for unfolded or partly folded proteins. Nevertheless, qualitative insights into the dynamics of unfolded states can be obtained by model-free analysis (Alexandrescu and Shortle, 1994 Buck etal., 1996 Farrow etal., 1995a). An extension of the model-free analysis to incorporate a spectral density function that assumes a distribution of correlation times on the nanosecond time scale has recently been reported (Buevich et al., 2001 Buevich and Baum, 1999) and better fits the experimental 15N relaxation data for an unfolded protein than does the conventional model-free approach. 

Detailed pictures of the iron-binding sites in transferrins have been provided by the crystal structures of lactoferrin (Anderson et ai, 1987, 1989 Baker etai, 1987) and serum transferrin (Bailey etal., 1988). Each structure is organized into two lobes of similar structure (the amino- and carboxy-terminal lobes) that exhibit internal sequence homology. Each lobe, in turn, is organized into two domains separated by a cleft (Fig. 3 and 10). The domains have similar folding patterns of the a//3 type. One iron site is present in each lobe, which occupies equivalent positions in the interdomain cleft. The same sets of residues serve as iron ligands to the two sites two tyrosines, one histidine, and one aspartate. Additional extra density completes the octahedral coordination of the iron and presumably corresponds to an anion and/or bound water. The iron sites are buried about 10 A below the protein surface and are inaccessible to solvent. 

All of the undamaged particles in Fig. 14 are of nearly uniform projected electron density, decreasing near the boundaries. There is no TEM evidence of internal structure. With increasing electron beam irradiation, however, all of the particles develop the well-known large differences in contrast (e.g., TE-3170 in Fig. 15) that have been attributed by some authors to folded ribbons or fibrils [1,13,14,17] and that we [4] and others [15,16] have attributed to beam damage. It is noted the particles shrink considerably during the beam damage. 

One crucial aspect is the large difference in the thermal expansion coefficients of stainless steel and SiOx (more than 10-fold, Table 5.4.1). As a result, temperature changes create significant stress at the interface between the steel and the SiOx. During operation, mechanical stress is introduced in addition to the thermal stress. To prevent the formation of cracks, the internal stress of the SiOx layer has to be chosen so that the SiOx remains under compressive stress under all operating conditions. Typically, the internal stress needs to be compressive and on the order of 100 MPa. Stability against cracks is favored by a high density of the deposited layer [9],... 

Carboxy- and amino-functionaUzed polystyrene nanoparticles have been synthesized by the miniemulsion process using styrene and the functional monomers acrylic acid (AA) or 2-aminoethyl methacrylate hydrochloride (AEMH) as functional comonomers [30,31]. By changing the amount of the comonomer, different surface densities of the charged groups could be realized. Since a fluorescent dye was incorporated inside the nanoparticles, the uptake behavior of different cell Unes could be determined as a function of the surface functionalization [30,31]. It was found that, in general, the uptake of the nanoparticles into the cells increases with increasing functionality on the particle s surface. For HeLa cells, for example, the internalized particle amount was up to sixfold better for carboxy-functionaUzed polystyrene (PS) nanoparticles than for non-functionalized PS particles. For amino functionalized PS nanoparticles, an up to 50-fold enhanced uptake could be detected. In order to investigate the actual uptake pathway into HeLa cells, positively... 

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