Covalent derivatization

Fig. 7-2. Type I Covalent derivatization with a unichiral reagent.

Type I Covalent Derivatization with a Unichiral Derivatizing Agent... 

Photoaffinity analogs of UDP-Xyl and UDP-GlcA have been chemo-enzymatically synthesized for a covalent derivatization and 32P-labeling of membrane-bound glycosyltransferases and nucleotide sugar metabolizing enzymes (Table 4) [322, 325, 359, 360],... 

Static modification (e.g., adsorbed oligomers, polymer coatings, or covalent derivatization)... 

Resolving Reagent for Carboxylic Acids and Other Types of Compounds. A large number of carboxylic acids have been resolved via their diastereomeric salts with (S)- or (7 )-a-methylbenzylamine (1). The ready availability of both enantiomers of (1) guarantees access to both enantiomers of the desired acid. Compounds (2)-(6) are representative examples of acids obtained in high enantiomeric purity. " Alternatively, racemic carboxylic acids have been resolved by covalent derivatization with (1) and separation of the resulting diastereomeric amides by physical means such as chromatography (eq 1) or fractional crystallization (eq 2). ... 

Chromatographic enantioseparations can be achieved when the diastereoisomeric interaction is established via a precolumn covalent derivatization, or a non-covalent association formed within the chromatographic system through the use of chiral mobile phase additives (primarily an LC technique) or chiral stationary phases. 

The principles of fluorescence quenching have been successfully applied to assays for protease activity. Proteases are digestive enzymes that degrade polypeptides into smaller oligopeptides or constituent amino acids. A general assay12 for protease activity employs a substrate prepared by covalently derivatizing a protein, transferrin, with a number of fluorescein isothiocyanate (FITC) labels. The FITC labeled proteins (Fig. 3.3) exhibit absorbance maxima at 495 nm and emission maxima at 525 nm. 

As mentioned above, fhe second PASP strategy for purifying a crude reaction mixture after a synfhesis is to separate fhe desired product by selective covalent derivatization with a functionalized resin followed by filtration and rinsing. After fhe formation of the product in solution, it reacts selectively wifh a solid support while impurities and unreacted substrate remain in solution and are washed away. This resin-capture concept has been demonstrated in fhe context of fhe Ugi four-component condensation [51]. After the condensation, fhe reactivity of fhe enam-ide allowed fhe specific reaction with Wang resin under anhydrous acidic conditions. The resin was washed wifh methanol and dichloromefhane and fhe subsequent cleavage was performed with trifluoroacetic add in dichloromefhane. The final carboxyhc adds were characterized without further purification and were found to be > 95 % pure. 

Noteworthy is the presence in this pathway of Trpl91, which is the center of radical formation in CCP compound I as discussed in Section IV. Using flash photolysis it has been possible to directly observe intracomplex electron transfer from ferrocyt c to compounds I and II of CCP in the preformed complexes. In one set of experiments (108), cyt c was covalently derivatized at surface lysine residues with a Ru-polypyridine photoredox reagent (Ru). Photoinduced intracomplex electron transfer was observed following rapid reduction of cyt c by Ru ... 

Protein expression encompasses an enormous dynamic range. Since rare proteins cannot be amplified by any type of PCR method, sensitive detection is critical to proteome projects. Fluorescence methods deliver streamlined detection protocols, superior detection sensitivity, broad linear dynamic range and excellent compatibility with modem microchemical identification methods such as mass spectrometry. Two general approaches to fluorescence detection of proteins are the covalent derivatization of proteins with fluorophores or noncovalent interaction of fluorophores through direct electrostatic interaction with proteins. One approach for quantifying fluorescence is to use a photomultiplier tube detector combined with a laser... 

Popular stabilizers in the solubUization buffer are 10 to 20% (w/v) glycerine, 1 mM DTT, and 0.1 to 1 mM EDTA. The protease inhibitors PMSF, bacitracine, trypsin inhibitor, leu-peptin, benzamide, and benzamidine are also a blessing, in that binding activities in solution are more sensitive against protease than in the membrane (see Table 5.1). PMSF irreversibly inhibits serin proteases via covalent derivatization of the active center. A one-time application is thus sufficient, especially because PMSF falls apart in watery solution (half-life of a few hours). 

Harnessing bioinspired phenomena such as molecular recognition and self-assembly, a new approach termed Non-Covalent Derivatization was developed. The properties of hydroquinone were successfully altered by incorporating the hydroquinone molecules in a matrix with compatible alkylterephthalamide molecules. This was achieved via one-step solventless... 

Pollution Prevention via Molecular Recognition and Self Assembly Non-Covalent Derivatization. Warner, J. C., in Green Chemistry Frontiers in Benign Chemical Synthesis and Processes Anastas, P. and Williamson, T. Eds., Oxford University Press, London, pp 336 - 346. 1998. 

In order to construct an ordered monolayer on a carbon surface, a premodified smooth and functionalized film is needed. Electrochemical reduction of diazonium salts or oxidation of amine-containing compounds and arylacetate produces free radicals, resulting in covalent derivatization of the carbon surface in nonaqueous solutions (Figure 3). The premodification by free radical grafting methods is quite mild, simple, and rapid experimentally. The monolayers prepared as a precursor film for subsequent assembly are stable to harsh environments and can endure elevated temperatures, and especially are organized in order, compact, and charge-rich. 

Covalent derivatization of proteins in this instance dictated the modes of separation and enhanced detection sensitivity. Non-covalent dye-protein interactions can alternatively be exploited to facilitate protein determination by ju-chip electrophoresis with LIF detection, thus offering greater... 

All of the examples in Scheme 6.41 use chiral reagents that are incorporated into the products. Therefore, all of these applications may be regarded as examples of double-covalent derivatization as well as PKR. The relative merits of such... 

Marchand-Brynaert J, Detrait E, Noiset O, Boxus T, Schneider Y-J, Remade C. Biological evaluation of RGD peptidomimetics, designed for the covalent derivatization of cell culture substrata, as potential promoters of cellular adhesion. Biomaterials 1999 20 1773-82. 

Herino R (2000) Nanocomposite materials from porous silicon. Mater Sci Eng B 69-70 70-76 Hong C, Kim H, Park S, Lee C (2010) Optical properties of porous silicon coated with ultrathin gold fihn by RF-magnetron sputtering. J Eur Ceram Soc 30 459-463 Jia P, Yan Chun T, Ning X, Wei L, ShouJun X, JianNing L (2010) Covalently derivatized NTA microarrays on porous silicon for multi-mode detection of his-tagged proteins. Sci China Chem 53 1-10... 

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