Amino groups reversible modifying

The noncovalent adsorption of proteins by p.CP is experimentally simple, but suffers from the disadvantage that the attachment can be reversible by rinsing the pattern with certain buffers and detergents or replacement by other proteins in solution. Moreover, the orientation of the deposited protein is not controlled. Delamarche et al. proposed the use of stamps modified with poly(ethylene oxide) silanes.100 The modification was conducted by oxidation of the PDMS stamp and reaction with APTES to yield an amino-functionalized surface. The next step was the reaction with homobifunctional cross-linker BS3 to bind surface amino groups with poly(ethylene glycol) (PEG) chains (Fig. 14.10). 

Figure 18. Reversible reductive alkylation of amino groups. Amino groups are alkylated first by treatment with (a) glycolaldehyde or (b) acetol in the presence of sodium borohydride. Reversal of the modification is effected by treating the modified amino group with 10-20mM NalOh for 30 min (85).

Reversible Modifying Reagents for Amino Groups in Proteins... 

Scheme III. Scheme for separating proteins and nucleic acids from a nucleoprotein complex using reversible modifying reagents of amino groups in the proteins...

Silica with bonded fullerene probably can be used for the separation of organic compounds by reversed phase liquid chromatography if the fullerene modifying layer will be stable to hydrolysis. The reaction of fullerenes with amino groups can be used for the modification of capillary columns for the separation of compounds by capillary gas chromatography. 

An alternative to the mirror image-approach is the direct selection of an aptamer from libraries of chemically modified RNAs. Many modifications in the ribose moiety of nucleic acids have been shown to dramatically increase their nuclease resistance. Modifications have to be chosen so as to be compatible with nucleic acid replicating enzymes such as reverse transcriptase, or DNA- and RNA-polymerases. The modifications most commonly used are those in which the 2 -OH group of pyrimidines is substituted by a 2 -fluoro-, or a 2 -amino group (1) [64,65],... 

Colman and Frieden (108) demonstrated in 1966 that acetylation of one amino group per subunit with acetic anhydride produces 80% inactivation. More extensive acetylation alters the degree of polymerization and certain kinetic parameters (276). Almost simultaneously, Anderson et al. (277) reported the reversible inhibition of GDH by pyridoxal 5 -phosphate and certain other aromatic aldehydes. The inhibition was attributed to formation of a Schilf base since reduction with NaBH4 results in irreversible inactivation. It was estimated that approximately one residue of -pyridoxyllysine had been formed per subunit. In 1969, Holbrook and Jeckel (278) inactivated the enzyme by reaction with a substituted maleimide and, subsequently, obtained the partial sequence of a tryptic peptide containing a modified lysine residue (Fig. 7). 

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