Other Capsules

Various other examples have been provided in the literature involving the formation of molecular capsules. However, guest binding by these capsules may not have been studied, or evidence of a template requirement for formation may not have been present. These include urea-based calixarene dimers [50], deep-cavity resorcinarenes [51], 

The reversible nature of self-assembling capsules has already been exploited as molecular switching devices and catalysts. Other applications may involve the development of artificial enzymes, and the design of specific drug delivery systems. 

We thank Christoph Naumann and Ashley Causton for careful reading of this manuscript. We also thank the funding agencies (NIH, PRF, and NSERC) for supporting our work, and we thank the authors of the references discussed for providing a stimulating area to review. 

Over the last four decades, synthetic non-enzymatic oligonucleotide ligations have been explored as potential models for the evolution of replicating systems on the early Earth [2-11]. These studies have explored ligation reactions that occur on a template without protein/enzymatic catalysis. Such systems have both provided mechanisms for the early evolution of biopolymer catalysts and placed limits on template directed ligation. More recently, the lure of antisense molecules capable of disrupting specific gene expression has resulted in the exploration of backbone-modified nucleic acids [12-33]. 

At the same time, several laboratories have used in-vitro selection strategies to identify RNAs and DNAs that catalyze specific reactions [34-40]. The information from these and related studies now opens the possibility of expanding the molecular skeletons capable of storing sequence information into ones that can be read into complementary materials [41]. 

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The concept of a well-stirred segregated reactor which also has an exponential residence time distribution function was introduced by Dankwerts (16, 17) and was elaborated upon by Zweitering (18). In a totally segregated, stirred tank reactor, the feed stream is envisioned to enter the reactor in the form of macro-molecular capsules which do not exchange their contents with other capsules in the feed stream or in the reactor volume. The capsules act as batch reactors with reaction times equal to their residence time in the reactor. The reactor product is thus found by calculating the weighted sum of a series of batch reactor products with reaction times from zero to infinity. The weighting factor is determined by the residence time distribution function of the constant flow stirred tank reactor. 

In the present paper we extend our analysis of the experimental results obtained from this small deformation regime and we show that the result found by Reissner for the deformation of shallow spherical caps represents an excellent analytical approximation for the interpretation of the measurements. This result is varified by finite element modelling (FEM) and by experimental variation of the force probe geometry and radius as well as wall thickness of the studied capsules. This result is also applicable for other capsule deformation measurements, since it is independent of the specific Young s modulus. Furthermore, we report on speed dependent measurements that indicate the glassy nature of PAH/PSS multilayers. 

Some other capsules have been described in which both complimentary functions, carboxylic acids and nitrogen-containing aromatic rings, are respectively attached to the rims of two bowl-shaped molecules. Reinhoudt has prepared selfassembling, multi-hydrogen bonding molecular capsules in which a calix[4]arene substituted with four carboxylic functions at the upper rim interacts with a complimentary calix[4]arene with four pyridines attached to the lower rim. These capsules have been identified by H-NiMR, IR and VPO measurements but encapsulation properties have not been reported [106]. 

Capsules do noi have lo be inserted in a proper orientation, as in all other capsule based systems. 

Gutcho, M.H. Microcapsules and Other Capsules, Advanced Since 1975 Noyes Data Corp. Park Ridge, NJ, 1979. 

Indeed, very recently, several examples for the use of diffusion NMR for studying other capsules were reported by different groups [38]. 

Fisons introduced the first DPI with the capsule-based Spinhaler . This was followed by a number of other capsule devices and then by unit dose blisters and multidose systems. DPIs are very diverse in their design and operation, since each product manufacturer has developed their own proprietary devices for their own drugs. 

As examples the separation of aspirin, caffeine, and phenacetin (APC tablets) is accomplished by a mobile phase of methanol-acetic acid-ether-benzene (1 18 60 120) and nitroglycerine, a vasodilator, present in heart medication capsules can be separated from the other capsule materials by benzene. 

Severe nausea, vomiting, drowsiness, prolonged QT, and episodes of nonsustained ventricular tachycardia were reported in a 34-year-old woman who had taken three or four 500 mg capsules of passionflower daily for several days. A sample of the product taken by the patient was analyzed and compared to other capsules produced by the same manufacturer and to other commercial samples of passionflower, and also tested for the presence of two... 

Microcapsules with desired release rates according to the application involved can be prepared by incorporating a selected fluid (solvent), while keeping the other capsule parameters constant. These fluids include dearomatized and isoparaffinic hydrocarbons, aromatic hydrocarbons, acetate derivatives, and blends of these [51], In the preparation of polyurethane-polyurea microcapsules containing hep-tenophos (liquid pesticide, b.p. 64 °C), it has been reported that the porosity of microcapsules can be controlled by the addition of 2-ethoxy ethyl acetate or ethyl acetate in the organic phase containing isocyanate prepolymer and pesticide [52]. 

An intriguing class of hydrogen-bonded self-assembled molecular capsule is that of the Rebek dimeric capsules based on deep cavitands prepared from resorcin[4] arene derivatives [3,12,22], The importance of this class of dimeric capsules arises from their elongated shape which resulted in anisotropic imsymmetrical cavities which gave birth to several phenomena such as social and constellational isomerism, [23a-b] which could not be observed in the bulk or in other capsules... 

Gutcho MH (1979) Microcapsules and other capsules, advanced since 1975. Noyes Data Corp, New Jersey... 

The largest of the reversibly formed capsules are, ironically, the easiest to make. This accounts for their active pursuit in laboratories worldwide [6-15]. In relation to the other capsules, they are of the size of volleybaUs [16] and show the symmetry... 

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