Inner cavity

Vacuum Radiation Furnaces. Vacuum furnaces are used where the work can be satisfactorily processed only in a vacuum or in a protective atmosphere. Most vacuum furnaces use molybdenum heating elements. Because all heat transfer is by radiation, metal radiation shields ate used to reduce heat transfer to the furnace casing. The casing is water-cooled and a sufficient number of radiation shields between the inner cavity and the casing reduce the heat flow to the casing to a reasonable level. These shields are substitutes for the insulating refractories used in other furnaces. 

Hollow carbon nanotubes (CNTs) can be used to generate nearly onedimensional nanostrutures by filling the inner cavity with selected materials. Capillarity forces can be used to introduce liquids into the nanometric systems. Here, we describe experimental studies of capillarity filling in CNTs using metal salts and oxides. The filling process involves, first a CNT-opening steps by oxidation secondly the tubes are immersed into different molten substance. The capillarity-introduced materials are subsequently transformed into metals or oxides by a thermal treatment. In particular, we have observed a size dependence of capillarity forces in CNTs. The described experiments show the present capacities and potentialities of filled CNTs for fabrication of novel nanostructured materials. 

The alkaline version of the Mn02 / zinc cell follows a different concept because it turns the construction of the Leclanche cell completely around now the cathode (Mn02 + carbon) forms a hollow cylinder contacting the inner wall of the cell container (steel) along its outer surface. The inner cavity has to accommodate anode, electrolyte, separator, and current collector. Usually, the separator forms a basket, which is automatically inserted and pre-... 

Inward Rectifier K+ Channels. Figure 5 Proposed three-dimensional arrangement of the transmembrane region of Kir channels. Two of four subunits are indicated. The pore consists of a selectivity filter close to the outside part of the membrane, a central inner vestibule, and a cytoplasmic entrance. Spermine may block in the inner cavity or in the selectivity filter. Large intracellular vestibule where polyamines may also block the channel is not shown. 

The three-dimensional structure of the sodium channel (from electric eel) was determined at 19-A resolution using cryo-electron microscopy and single-particle image analysis. The sodium channel has a bell-shaped outer surface of 135 A in height, 100 A in side length at the square bottom, and 65 A in diameter of the spherical top. An interesting finding is that there are several inner cavities connected to outer orifices. 

Figure 46-8. Fusion of a vesicle with the plasma membrane preserves the orientation of any integral proteins embedded in the vesicle bilayer. Initially, the amino terminal of the protein faces the lumen, or inner cavity, of such a vesicle. After fusion, the amino terminal is on the exterior surface of the plasma membrane. That the orientation of the protein has not been reversed can be perceived by noting that the other end of the molecule, the carboxyl terminal, is always immersed in the cytoplasm. The lumen of a vesicle and the outside of the cell are topologically equivalent. (Re drawn and modified, with permission, from Lodish HF, Rothman JE The assembly of cell membranes. Sci Am [Jan] 1979 240 43.)...

One of the exciting results to come out of heterogeneous catalysis research since the early 1980s is the discovery and development of catalysts that employ hydrogen peroxide to selectively oxidize organic compounds at low temperatures in the liquid phase. These catalysts are based on titanium, and the important discovery was a way to isolate titanium in framework locations of the inner cavities of zeolites (molecular sieves). Thus, mild oxidations may be run in water or water-soluble solvents. Practicing organic chemists now have a way to catalytically oxidize benzene to phenols alkanes to alcohols and ketones primary alcohols to aldehydes, acids, esters, and acetals secondary alcohols to ketones primary amines to oximes secondary amines to hydroxyl-amines and tertiary amines to amine oxides. 

Zeolite ITQ-21 is a recently discovered zeolite [1], containing Si, Ge and optionally A1 as framework cations. Its three-dimensional structure is formed by three linear 12 ring (12-R) channels that intersect to produce large inner cavities with a nearly spherical shape about 1.18 nm in diameter (Figure 1), similar to those present in the Faujasite structure. However, in the case of ITQ-21 these cavities are accessible through six circular 12-R windows of 0.74 nm wide. 

Fig. 34. Model of a functionalised (internally or externally) SWNT, which may be closed, open and/or corked reversibly or permanently after filling. Potentially the inner cavity may be filled with a (radio)-imaging agent (for PET/SPECT and/or MRI) or a (radio)therapeutic agent. Such functionalized SWNTs may conceivably act as probe prototype for multimodal imaging/therapy and targeted drug delivery (155).

Fig. 13. Schematic illustration of metal-organic molecular squares, assembled from linear organic linkers and 90° metal units (left), linear metal units and organic comers (middle), or linear metal units and 90° metal units (113). The latter two classes have several inner-cavity binding sites and thus fit the definition of metalated container molecules.

Figure 5. Top Tetraurea calixarene monomers 37 and 38 bearing chiral amino acid ester residues (isoleucine and valine methyl esters, respectively) attached to the urea functions. Norcamphor 39 was the chiral guest used to detect the chirality transfer from the outside to the inner cavity.

The future prospects for the capsule project emerge from these considerations. Further increasing the size of the capsule and building chemical functionalities into the inner cavity would allow a closer emulation the functions of enzymes, especially those that require cofactors in order to catalyze chemical transformations. Another important aspect is to design capsules that can combine stereospecificity and catalysis - that is accelerate stereoselective transformations. Capsules that reversibly dimerize in water would probably contribute a lot more to our understanding of non-covalent forces and solvent effects in this most biorelevant medium. So far, water solubility and assembly have not been achieved with hydrogen-bonded capsules. 

The mobility of 1-butene molecules decreases from the gas (AH = 5 Hz) to the adsorbed state (AH = 35 Hz) at room temperature The latter depends on surface coverage as previously shown for benzene (33). At the low surface coverage (0 = 0.5) where not all the available Sjj sites are occupied - there are only 3 molecules for 4 different positions (4 ) - the mobility is smaller than in the higher surface coverage sample (0 = 0.9) and this effect is even more important at lower temperaure (250 K). In the latter, characterized by 4.6 molecules for 4 Sji sites - the molecules are exchanged between the strong adsorption sites and the inner cavity, hence the smaller linewidth. 

Lees-Miller et al. [49] were the first to use mutagenesis approaches to demonstrate the importance of an inner cavity residue in high-affinity binding. The mutation F656V substantially increased the IC50 for dofetilide and quinidine, without altering the potency of extracellularly applied TEA [49]. The binding site was more... 

The evolving structural insights into the hERG drug-binding site show that this channel has a relatively larger inner cavity, with many aromatic and polar residues intricately positioned to interact with drugs. Utilization of in silico techniques, refined... 

Figure 4.4 Placement of the hERG blocker pharmacophore in the inner cavity of the channel. The Cavalli pharmacophore [83] is placed within the pore illustrating its main features N (positively charged central nitrogen), CO (aromatic group), Cl and C2 (hydrophobic groups). The N feature is thought to form...

Figure 18.1 Schematic depiction of the putative filter form the inner cavity and the ligand-binding interactions between a spiropiperidine site. For clarity, S6 and pore helix domainsofonly...

The inner cavity of carbon nanotubes stimulated some research on utilization of the so-called confinement effect [33]. It was observed that catalyst particles selectively deposited inside or outside of the CNT host (Fig. 15.7) in some cases provide different catalytic properties. Explanations range from an electronic origin due to the partial sp3 character of basal plane carbon atoms, which results in a higher n-electron density on the outer than on the inner CNT surface (Fig. 15.4(b)) [34], to an increased pressure of the reactants in nanosized pores [35]. Exemplarily for inside CNT deposited catalyst particles, Bao et al. observed a superior performance of Rh/Mn/Li/Fe nanoparticles in the ethanol production from syngas [36], whereas the opposite trend was found for an Ru catalyst in ammonia decomposition [37]. Considering the substantial volume shrinkage and expansion, respectively, in these two reactions, such results may indeed indicate an increased pressure as the key factor for catalytic performance. However, the activity of a Ru catalyst deposited on the outside wall of CNTs is also more active in the synthesis of ammonia, which in this case is explained by electronic properties [34]. 

Fig. 10.16. Properties of the inner cavity. Half cut presentations of molecule A (left side view, center and right top views) with cut regions shown in dark gray. (Left) Surface representation of the internal tunnel illustrating its molecular-sieve character. Access is restricted to single secondary structure elements as shown by the modeled polyalanine helix, which is colored yellow. (Center) Top view on the...

In order to deal with a system whose structural characteristics were unaltered by the loading with Gd(III) chelates, we choose Apoferritin because it allows the Imaging Probes to be entrapped inside its inner cavity (60). The exterior of such Gd(III)-loaded Apoferritin is exactly the same as in the parent Ferritin and then, once administered intravenously, it is quickly cleared-up by the proper receptors on hepatocytes (172). The process of loading Apoferritin with [GdHPD03A(H20)] consists first of the dissociation of the protein into subunits at pH 2, followed by its reforming at pH 7, thereby trapping the solution components (e.g., [GdHPD03A(H20)])... 

Since the (Fen05(0H)6> unit is stable, it has been speculated(8b,17b) that it might also be present in the ferritin core. Since the majority of phosphate in ferritin is adventitious, surface bound and the metallic core can be reconstituted in the absence of phosphate groups with no change in the X-ray powder diffraction pattem(l), replacement of bridging phosphate by bridging carboxylate groups should not influence the three dimensional structure of the core. Calculations show that -409 Fell nnits could fill the apoferritin inner cavity. Further details can be found in reference 17. 

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