Derivatization amino group

IR spectroscopy has been used to estimate the yield [10], The UV spectrophotometric quantitative measurement of Fmoc release from derivatized amino groups is still a very common method for measuring loadings [14],... 

N-terminal end) The end of the peptide chain with a free or derivatized amino group. As the peptide is written, the N terminus is usually on the left. The carboxyl group of the N-terminal amino acid links it to the rest of the peptide, (p. 1174)... 

IR methods can be used to support a proposed intermediate in a reaction or to follow the incorporation of a distinctive functional group (e.g., CHO) onto a resin. IR is especially useful for surfaces such as pins or crowns where NMR techniques are not useful. High-quality IR spectra can be obtained from single beads. The UV spectrophotometric quantitative measurement of Fmoc release from derivatized amino groups is still a very common method for measuring loadings. Qualitative color tests are frequently used to follow reactions to assure completion. The Kaiser ninhy-drin test is the best known of these. An improved method for detection of secondary amines has been reported. ... 

Righetti and co-workers [11] were one of the first to demonstrate the utility of classical isoelectric focusing for the chiral separation of small molecules in a slab gel configuration. In their system, dansylated amino acids were resolved enan-tiomerically through complexation with (i-cyclodextrin. Preferential complexation between the cyclodextrin and the derivatized amino acid induced as much as a 0.1 pH unit difference in the pK s of the dansyl group. 

Another way to derivatize the OH group is by silylation using the Tri-sil Z reagent that will silylate the hydroxyl group, but not silylate the secondary amino group. 

Preparation of the TMS derivative Add 0.5 ml of TRI-SIL Z reagent (trimethylsilylimidazole in pyridine) to 1-5 mg of the sample. (This derivatizing preparation does not react with amino groups and tolerates the presence of water.) Heat in a sealed vial at 60° until the sample is dissolved. An alternate method is to let the reaction mixture stand at room temperature for at least 30 minutes (or overnight). This procedure is not appropriate for amino sugars. 

Reports on the use of fluorescent derivatives abound (5). Some reagents have become widely used. The dansyl group is probably the most thoroughly studied. Dansyl chloride has been widely used as a fluorescent derivatizing reagent for HPLC (6,7). It reacts readily with primary and secondary amino groups (7) and with phenols (8), but forms derivatives of alcohols very slowly (9). The lower detection limit for dansyl derivatives of aliphatic amines is in the range of 300 femtomoles per injection. 

Many times an analyte must be derivatized to improve detection. When this derivatization takes place is incredibly important, especially in regards to chiral separations. Papers cited in this chapter employ both precolumn and postcolumn derivatization. Since postcolumn derivatization takes place after the enantiomeric separation it does not change the way the analyte separates on the chiral stationary phase. This prevents the need for development of a new chiral separation method for the derivatized analyte. A chiral analyte that has been derivatized before the enantiomeric separation may not interact with the chiral stationary phase in the same manner as the underivatized analyte. This change in interactions can cause a decrease or increase in the enantioselectivity. A decrease in enantioselectivity can result when precolumn derivatization modifies the same functional groups that contribute to enantioselectivity. For example, chiral crown ethers can no longer separate amino acids that have a derivatized amine group because the protonated primary amine is... 

The unsubstituted phthalic acid hydrazide and several nonaromatic cyclic hydrazides such as maleic acid hydrazide or succinic acid hydrazide are either nonchemiluminescent or show extremely weak CL. However, the 6-amino isomer of luminol, which is called isoluminol, is chemiluminescent to about the same extent as is luminol. Isoluminol has been used in many chemiluminescent studies, and because the amino group is less sterically hindered than that of luminol, it is probably derivatized for chemiluminescent labeling far more often than is luminol (Fig. 3). 

It should be noted that the majority of the derivatization techniques modify the peptide s N-terminus. The reason is that the N-terminal amine group is easier to modify than the C-terminal carboxyl group. Also, due to differences in pKa value in the e-amino group of lysine, there are possible reaction that modify the N-terminus only, while the lysine side chains remain intact. Modifications of carboxyl groups... 

Pre-column derivatization with either 134 or 135 followed by CZE and LIF detection was proposed for amino acids. The amino group of the analyte displaces the succinyloxy moiety of the reagent yielding a carboxamide325. See also Section IV.D.3.C for other acylating reagents derived from A-hydroxysuccinimide (95 and 96). 

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