Surface protuberances

FIGURE 1.12 Van der Waals packing is enhanced in molecules that are structurally complementary. Gln represents a surface protuberance on the protein lysozyme. This protuberance fits nicely within a pocket (formed by Tyr , Tyr , Phe and Trp ) in the antigen-binding domain of an antibody raised against lysozyme. (See also Figure 1.16.)... 

In pressure-swirl atomization, the complex atomization process may be conveniently subdivided into two main stages, as suggested by Lefebvre.12661 In the first stage, surface instabilities are generated as a result of the combined effects of hydrodynamic and aerodynamic forces. In the second stage, surface protuberances are... 

It may not be adequate to describe the interaction between Agl particles — especially at relatively close range —in terms of the radii of the dispersed units. In fact, the radii of surface protuberances rather than the dimensions of the particle as a whole may affect the short-range interaction. 

Figure 6.48 Extrusions and intrusions in the copper7 after 6 x 70s cycles in air. Sample covered with silver and mounted at an angle to magnify surface protuberances x20...

Figure 8.19. Extrusions and intrusions in copper after 6 x 10 cycles in air. Specimen plated with silver after test and mounted at an angle to magnify surface protuberances by about 20x. Overall magnification about SOOx. [Figure 3 from W. Wood and H. Bendler, The fatigue process in copper as studied by electron metallography, Trans. Metall. Soc. AIME 224, 182...

Different specimen types yield a range of results upon ion or plasma etching. Multiphase polymers generally etch differentially, enhancing the contrast. Melt crystallized polymers can be etched to reveal the spherulites. Surface protuberances and particulate fillers can and do form cones or ridges when etched. Oriented semicrystalline polymers, on the other hand, appear to be the most controversial with respect to the resulting surface textures. Clearly, in such cases the specimen should be prepared by other methods for comparison, and control experiments are essential. There are problems in the industrial laboratory that can be solved, in part, by microscopy of surfaces prepared by etching techniques however, these are far fewer than those addressed by other specimen preparation methods. 

Figure Bl.22.11. Near-field scanning optical microscopy fluorescence image of oxazine molecules dispersed on a PMMA film surface. Each protuberance in this three-dimensional plot corresponds to the detection of a single molecule, the different intensities of those features being due to different orientations of the molecules. Sub-diffraction resolution, in this case on the order of a fraction of a micron, can be achieved by the near-field scaiming arrangement. Spectroscopic characterization of each molecule is also possible. (Reprinted with pennission from [82]. Copyright 1996 American Chemical Society.)...

Figure 7.14a illustrates the insertion of a propylene monomer into an edge vacancy in a crystal adjacent to an alkylated titanium atom. In Fig. 7.14b a cross-sectional view of the same site shows how the preferential orientation of the coordinated monomer is dictated by constraints imposed by the protuberances on the crystal surface. 

The shape of the interaction area between lysozyme and the CDR loops of the antibody is easily distinguished from the hapten-binding crevice. The interaction extends over a large area with maximum dimensions of about 20 X 30 A (Figure 15.15). The interaction surface is irregular but relatively flat, with small protuberances and depressions that are complementary in the antigen and the antibody. Residues from all six CDR loops contribute to the... 

The results obtained demonstrate competition between the entropy favouring binding at bumps and the potential most likely to favour binding at dips of the surface. For a range of pairwise-additive, power-law interactions, it was found that the effect of the potential dominates, but in the (non-additive) limit of a surface of much higher dielectric constant than in solution the entropy effects win. Thus, the preferential binding of the polymer to the protuberances of a metallic surface was predicted [22]. Besides, this theory indirectly assumes the occupation of bumps by the weakly attracted neutral macromolecules capable of covalent interaction with surface functions. 

In principle, sites a, IT, and c need not be association sites as depicted by Ogston but could be steric sites that form obstructions such that the adsorbed molecule is chirally directed. Only one active site is actually required providing the remaining two sites (protuberances or cavities) are different from each other and from the active site that catalyzes the reaction. They could be identical providing they are not symmetrically oriented with respect to the active site (not an isosceles triangle). These are the basic concepts for a chiral environment on a surface and they lead to the three basic methods for creating chiral surfaces in heterogeneous catalysis. 

Preferred adsorption of the unsaturated bond of the substrate occurs at that face which presents the least steric interactions between the adsorbed substrate and the surface. Since some amazingly sterically hindered molecules can be hydrogenated, at least some active sites must look like corners or edges or some other protuberances. 

Chigiefl211 found that turbulence in a liquid jet has important disturbing influences throughout the liquid flow. At the liquid surface, turbulent velocity fluctuations directly cause protuberances and roughness that result in direct stripping by surrounding air flow. Large eddy structures in the air flow penetrate into the liquid and... 

Some protuberances may be created on a droplet surface due to local deformations. Under favorable conditions, these bulges detach from the droplet and disintegrate into smaller droplets. 

Fig. 9.10 SWCNTs attached to the surface of cells and located within cells a. SWCNTs attached to the surface of cells b. SWCNTs labeled with Cy3 located within cells c. Some protuberances appeared on the cell surface after cells are stimulated by SWCNTs. Right picture is control. Bar is 10 pm (With permission from American Scientific publisher) (See Color Plates)...

Fig. 8.15. Illustration of the desolvation of ions, (a) Charge separation inside a protuberance, (b) continuous reconstruction of the surface allows for successive rupture of inter-molecular bonds and stepwise desolvation of the ions. Reproduced from Ref. [83] by permission. Elsevier Science, 1984.

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