Derivatization carboxylic group

C-terminal end) The end of the peptide chain with a free or derivatized carboxyl group. 

C terminus (C-terminal end) The end of the peptide chain with a free or derivatized carboxyl group. As the peptide is written, the C terminus is usually on the right. The amino group of the C-terminal amino acid links it to the rest of the peptide, (p. 1172)... 

Ph3COSiMc3, Me3SiOTf, CH2CI2, 0°, 0.5 h, 73-97% yield. These conditions will also introduce the trityl group on a carboxyl group. The primary hydroxyl of persilylated ribose was selectively derivatized. 

AMCA may be coupled to amine-containing molecules through the use of the carbodiimide reaction using EDC (Chapter 3, Section 1.1). EDC will activate the carboxylate on AMCA to a highly reactive o-acylisourea intermediate. Attack by a nucleophilic primary amine group results in the formation of an amide bond (Figure 9.22). Derivatization of AMCA off its carboxylate group causes no major effects on its fluorescent properties. Thus, proteins and other macromolecules may be labeled with this intensely blue probe and easily detected by fluorescence microscopy and other techniques. 

BSA possesses a total of 59 lysine e-amine groups (with only 30-35 of these typically available for derivatization), 1 free cysteine sulfhydryl (with an additional 17 disulfides buried within its three-dimensional structure), 19 tyrosine phenolate residues, and 17 histidine imidazole groups. The presence of numerous carboxylate groups gives BSA its net negative charge (pi 5.1). 

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... 

Fig. 10.3 Examples of water-soluble derivatized fullerenes with 1, 3, and 18 carboxyl groups attached (Reprinted from Bosi et al., 2003. With permission from Elsevier)...

The protected (5)-4,8-diamino-3-oxooctanoic acid 99 was reduced with NaBH4, the resulting mixture of diastereomers was separated and the (3R,45)-product was derivatized with benzylated DHB (100). Then derivatized o-Ser-Gly was added and the serine OH-group was esterified with the protected OHAsp (101). The Gly carboxyl group was finally set free. 

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