Conformal encapsulation

Cheiv. Descrip. Benzophenone CAS 119-61-9 EINECS/ELINCS 204-337-6 Uses Free radical initiator for UV curing used in adhesives, chem. intermediates, coatings (metal, paper, wood), electronics (conformal, encapsulants, photoresists, solder masks), inks (flexo and gravure, litho, offset, screen) intermediate for mfg. of antihistamines, hypnotics, insecticides... 

Chem. Descrip. Ben ldimethyl ketal with 100 ppm MEHQ CAS 2465042-8 EINECS/ELINCS 246-386-6 Uses Photoinitiator tor UV-cured adhesives (pressure sensitive, structural), coatings (metal, optical, paper, plastic, PVC floor, textile, wood), photopolymers, electronics (photoresists, conformal, encapsulants, solder maste), iniffi (flexo, gravure, litho, offset, screen)... 

Many of the calixarenes retain the solvent from which they are crystallized. Crystal structures by Andreetti et al (126) of (128)-toluene complex show the calix to be in the cone conformation and the toluene located in the centre of the calix, i.e. an endo -calix complex (Figure 2.55). A recent publication by the same group (129) shows two molecules of (128) in the cone conformation encapsulating one molecule of anisole. 

In the course of these investigations, in 1947 Dr. Szwarc discovered a new hydrocarbon monomer, p-xylylene (quinomethane), that is formed in the vapor phase at high temperature (>800°C) and spontaneously polymerizes upon hitting any surface kept at room temperature. The resultant polymer forms a transparent film conformally encapsulating the object on which it is deposited. The film neither melts nor decomposes until heated above 400°C. Dr. Szwarc determined the structure of this monomer and its polymer. The first publication on this work appeared in 1947 in the Disc. Faraday Soc. 2, 46. Subsequently, a whole class of related quinonoid monomers based on substituted p-xylenes, 1,4-dimethylnaphthalenes, 2,5-dimethylpyrazene, etc., was developed (J. Polymer Sci., 6, 319 (1950)). 

Eggers, D.K. and Valentine, J.S. (2001) Crowding and hydration effects on protein conformation a study with sol-gel encapsulated proteins. Journal of Molecular Biology, 314, 911-922. 

Several enzymes have been immobilized in sol-gel matrices effectively and employed in diverse applications. Urease, catalase, and adenylic acid deaminase were first encapsulated in sol-gel matrices [72], The encapsulated urease and catalase retained partial activity but adenylic acid deaminase completely lost its activity. After three decades considerable attention has been paid again towards the bioencapsulation using sol-gel glasses. Braun et al. [73] successfully encapsulated alkaline phosphatase in silica gel, which retained its activity up to 2 months (30% of initial) with improved thermal stability. Further Shtelzer et al. [58] sequestered trypsin within a binary sol-gel-derived composite using TEOS and PEG. Ellerby et al. [74] entrapped other proteins such as cytochrome c and Mb in TEOS sol-gel. Later several proteins such as Mb [8], hemoglobin (Hb) [56], cyt c [55, 75], bacteriorhodopsin (bR) [76], lactate oxidase [77], alkaline phosphatase (AP) [78], GOD [51], HRP [79], urease [80], superoxide dismutase [8], tyrosinase [81], acetylcholinesterase [82], etc. have been immobilized into different sol-gel matrices. Hitherto some reports have described the various aspects of sol-gel entrapped biomolecules such as conformation [50, 60], dynamics [12, 83], accessibility [46], reaction kinetics [50, 54], activity [7, 84], and stability [1, 80],... 

J.D. Badjic and N.M. Kostic, Effects of encapsulation in sol-gel silica glass on esterase activity, conformational stability, and unfolding of bovine carbonic anhydrase II. Chem. Mater. 11, 3671-3679 (1999). 

Using information obtained from X-ray crystallography, we have described the structure of a chiral, spherical molecular assembly held together by 60 hydrogen bonds. [10] The host, which conforms to the structure of a snub cube, self-assembles in apolar media and encapsulates guest species within a cavity that possesses an internal volume of approximately 1.4 nm3. 

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