Novel temporary protective coatings were prepared by the addition of release additives to waterborne polyurethane dispersions. New types of self-crosslinkable sulfourethane-silanol (SUS) dispersions were utilized as the peelable coatings. These dispersions are stable, low-volatility organic chemical (VOC) waterborne dispersions that spontaneously crosslink upon drying without extra additives or processing steps. Tensile strengths up to 6000 psi with elongations between 300-600% were obtained for the crosslinked films. The adhesion of the films to a variety of substrates can be controlled by the addition of hydrophilic additives, including glycerol, oligomers of glycerol, and poly(ethylene glycol) derivatives. Alternatively, hydrophobic additives that are water dispersible, such as paraffin waxes and sulfated castor oil, can also be used to control adhesion. In addition, this technique can be utilized for the release of films derived from a wide variety of waterborne urethane dispersions, including carboxylated polyurethane ureas. The removable coatings are useful for the temporary protection of plastic surfaces during thermoforming processes. (C) 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1443-1449,2004.

The addition of exogenous ent-cholesterol suppressed the antifungal activity of the amphotericin B when added to cultures of Candida albicans, but to a lesser extent than natural cholesterol. There were no detectable differences between added 2a or 2b on the antifungal activities of jaspamide or bengazole A, two unrelated antifungal natural products.

A novel type of crosslinkable waterborne polyurethane ionomer was prepared by the acetone process. Two new types of sulfonated diols compatible with this process were synthesized from dimethyl 5-sodium sulfo isophthalate using a one- or two-stage method. Isocyanate-terminated polyurethane oligomers were prepared from the sulfonated diols with various combinations of diols and diisocyanates and subsequently reacted with amino silane derivatives. Stable, low-volatile organic chemical, waterborne dispersions of the sulfo-urethane silanol polymers spontaneously crosslink upon drying without extra additives or processing steps. Despite the lack of organic coalescing solvents, the dispersions have minimum film-forming temperatures below 10 degreesC, regardless of glass-transition temperature. Tensile strengths up to 6000 psi with elongations between 300 and 600% were obtained for the crosslinked films. The hard-segment content of the films can be controlled to produce films with a Sward-Rocker hardness value up to 42. Through silane end-group modification, the crosslinking density of the films can also be modified to produce polyurethanes with a wide range of physical properties. (C) 2002 Wiley Periodicals, Inc.

The interaction between a monoclonal antibody and four distinct monolayers with varying degrees of structural, chemical, and stereochemical similarity were studied and quantified. The antibody, raised and selected against cholesterol monohydrate crystals, interacts with cholesterol monolayers stereospecifically, but not enantiospecifically. Monolayers of ent-cholesterol molecules, which are chemically identical to cholesterol and whose structure is the exact mirror image of the cholesterol monolayer, interact with the antibody to the same extent as the cholesterol monolayers. The affinity of the antibody for both enantiomeric monolayers is extremely high. However, the antibody does not interact with monolayers of epicholesterol, which is an epimer of cholesterol: The hydroxy group in epicholesterol is in the 3 alpha position rather than in the 3 beta position, imposing a different angle between the hydroxy group and the rigid steroid backbone, and a different packing of the molecules. Monolayers of triacontanol, a long-chain primary aliphatic alcohol, interact with the antibody to a lesser extent than the cholesterol and ent-cholesterol monolayers, presumably due to the structural flexibility of the triacontanol molecule. The lack of chiral discrimination by the antibody is thus correlated to the level at which the chirality is exposed at the surface of the monolayers.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEnantiomeric cholesterol as a probe of ion-channel structureDaniel E. Mickus, David G. Levitt, and Scott D. RychnovskyCite this: J. Am. Chem. Soc. 1992, 114, 1, 359–360Publication Date (Print):January 1, 1992Publication History Published online1 May 2002Published inissue 1 January 1992https://pubs.acs.org/doi/10.1021/ja00027a055https://doi.org/10.1021/ja00027a055research-articleACS PublicationsRequest reuse permissionsArticle Views207Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

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Cholesterol is ubiquitious in mammals and plays an important role in human health. The unique relationship between enantiomers makes ent-cholesterol, the unnatural enantiomer of cholesterol, a valuable new probe of cholesterol function in biochemical systems. We report the first enantioselective total synthesis of ent-cholesterol

AbstractLithiation of the tetrahydropyrans (I) and (V) or the dioxane (VIII) is performed with lithium di‐tert‐butylbiphenylide at a low temperature.

Both axial and equatorial 2-lithiotetrahydropyrans are readily prepared from 2-(phenylthio)-tetrahydropyrans. Axial 2-lithiotetrahydropyrans are formed selectively on reducing 2-(phenylthio)-tetrahydropyrans with lithium di-tert-butylbiphenylide, and equatorial 2-lithiotetrahydropyrans are formed selectively by thermal equilibration of the axial isomers.