Capsular structure

Typically, the characterization of supramolecular systems requires the application of a whole set of analytical techniques. Without going into details, the capsular structure of the tennis ball 1-1 has been confirmed by X-ray crystallography, vapor phase osmometry (VPO), and NMR experiments.1111 The encapsulation of guests can be routinely analyzed by NMR experiments. Recently, a mass spec-trometric method was developed that not only... 

In addition to the 20 amino acids most frequently found in proteins a large group of amino acids occur in plants, bacteria, and animals that are not found in proteins. Some are found in peptide linkages in compounds that are important as cell wall or capsular structures in bacteria or as antibiotic substances produced by bacteria and fungi. Others are found as free amino acids in seeds and other plant structures. Some amino acids are never found in proteins. These nonprotein amino acids, numbering in the hundreds, include precursors of normal amino acids, such as homoserine and diaminopimelate intermediates in catabolic pathways, such as pipecolic acid d enantiomers of normal amino acids and amino acid analogs, such as azetidine-2-carboxylic acid and canavanine, that might be formed by unique pathways or by modification of normal amino acid biosynthetic pathways. 

Systems with Capsular Structure Several single-unit pulsatile dosage forms with a capsular design have been developed. Most of them consist of an insoluble capsular body which contains the drug and a plug which is removed after a predetermined lag time because of swelling, erosion, or dissolution. 

The morphology of the capsule of a strain of E. coli has been examined by freeze-etching techniques. The effects of increasing concentrations of antibodies on the capsular structure, the location of the sites of synthesis of the capsular polysaccharide, and the export of the capsular polysaccharide were reported for a temperature-sensitive mutant. In addition to a Iiis-linked gene, a frp-Iinked gene is required for the synthesis of the complete K27(A) capsular polysaccharide of E. coli 08 K27. ... 

In natural system, there are many capsular structures like viral capsids " or ferritin protein, where building subunits assemble into the precisely determined structures. In these systems, the subunits not only construct the capsular structures but also have functions, that is, the origin and the action mechanism of the functions of the virus or protein themselves, using the functional groups of the peptides. For example, a viral capsid storing a DNA inside has cationic peptides on the internal surface of the capsule to capture and stabihze the DNA, which is anionic in nature, through electrostatic interactions. 

Figure 10 The molecular structure of p-tertbutylcalix[4]arene (2) and its dimeric capsular structure. The void within the capsule is mapped as a yellow surface.

Figure 16 (a) p-OctanoylcaUx[4]arene (3), its crystal packing, and capsular structure, (b) Adsorption isotherms for the capsular form... 

The excited-state Si lifetime of pyrene included in OA was found to be 350 ns, suggesting that pyrene resides as a single molecule within the OA capsule [117]. The /1//3 ratio after addition of 2 mol equiv OA was found to be 1.01, similar to that of benzene, indicating a closed and compact capsular structure in which water molecules from the solvent are excluded. 

From a materials engineering perspective, what is needed in order to completely characterize these capsular structures, is a tool with which to probe their mechanical properties - an ability to manipulate individual giant lipid vesicles capsules and cells, that can not only apply well defined stresses for each of the three basic modes of deformation, (dilational, shear, and bending), but that can also measure the strain resulting from the applied stress, and therefore characterize the material behavior in terms of elastic moduli and viscous coefficients. The micropipet technique, initiated by Rand and Burton [92] and later perfected by Evans and Hochmuth [16], provides such an ability. It has been used extensively since the late 1970s to measure and characterize the material properties of red cells, white cells, and giant vesicles as reviewed in several recent publications [30,69,82]. 

The co-solvents can be encapsnlated within the cavity of the capsular structure. The volume of the inner cavity was calculated to be 237 A. Rebek reported that a self-assembled dimeric capsule prefers to be filled by a guest with a volume occupying approximately 55% of the binding space. Accordingly, toluene is a good guest for the dimeric capsule, while the molecular volume of chloroform is too small to... 

As shown in Figure 9.9, all the PMCs have well-defined capsular structure, dense shell, and large lumen. The PMCs are quite uniform with a lumen diameter of around 400 nm. The shell thicknesses of PMC-C, PMC-S, and PMC-N are around 127,... 

Compared with emulsion polymerization and suspension polymerization, the manufacturing process of suspension polymerization of inverse emulsion is more complicated. The advantage of using this technology is to make a capsular structure which has a polymer shell and liquid inner phase. The polymer shell can provide protection by preventing the inner phase from leaking out. When nanoparticles are added to the polymer shell, they can inhibit mass transfer and reinforce the polymer matrix to make the nanocomposites stronger or thermally stable. More importantly, the presence of nanoparticles can partially replace or completely eliminate the use of emulsifiers in the nanocomposite bead synthesis process. One application, as mentioned before, is to make PS nanocomposite... 

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