Derivatization, amino acids

Watanabe Y, Imai K (1981) High-performance liquid chromatography and sensitive detection of amino acids derivatized with 7-fluoro-4-nitrobenzo-2-oxa-l,3-diazole. Anal Biochem 116 471—472... 

Hu S, Li PCH (2000) Micellar electrokinetic capillary chromatographic separation and fluorescent detection of amino acids derivatized with 4-fluoro-7-nitro-2,l,3-benzoxadiazole. J Chromatogr A 876 183-191... 

Figure 5.20 TEM images of twisted ribbons observed in diacetylenic amino-acid-derivatized lipids in methanol-water solution (a) Glu-PDA (34) (b, c) Gln-PDA (35). Bar = 0.6 xm. Reprinted with permission from Ref. 95. Copyright 2000 by the American Chemical Society.

Amino acids derivatized with 9-fluorenylmethyl chloroformate (90) were separated by CE and determined by LIF with a pulsed laser LOD 0.5 nM (SNR 2)322. A sensitive technique for amino acids is capillary zone electrophoresis (CZE) combined with LIF of their fluorescein isothiocyanate (133) derivatives. Not all amino acids give good resolution. LOD for proline and arginine were 0.3 and 0.5 nM, respectively323. 

Song, Y, Shenwu, M., Zhao, S., Hou, D., and Liu, Y. M., Enantiomeric separation of amino acids derivatized with 7-fluoro-4-nitrobenzoxadiazole by capillary liquid chromatography/tandem mass spectrometry,/owmaZ o/Chroma/ograp/jy 4 1091(1-2), 102-109,2005. 

Cheng Q, Stevens RC. Charge-induced chromatic transition of amino acid-derivatized polydiacetylene liposomes. Langmuir 1998 14 1974-1976. 

F. Lai and T. Sheehan, BioTecbniques 14, 642-649 (1993). A comparison of reagents for amino acid derivatization. 

P Grossman andj Colburn, Editors, Capillary Electrophoresis Theory and Practice (1992), Academic Press (San Diego). An up-to-date and complete review of CE E Heimer,/. Chem. Educ. 49, 547 (1972) Paper chromatography of amino acids F Lai and T Sheehan, BioTechniques 14, 642-649 (1993) A comparison of reagents for amino acid derivatization... 

Amino acid derivatization reagents Performic acid... 

SA Cohen, KM DeAntonis. Applications of amino acid derivatization with 6-aminoquinolyl-Al-hydroxysuccinimidyl carbamate. Analysis of feed grains, intravenous solutions and glycoproteins. J Chromatogr A 661 25-34, 1994. 

Amino acids derivatized with isothiocyanates (PITC, NITC, DNITC, DABITC), with AQC. or with sulphonyl chlorides (DNS-Cl. DABS-CI)... 

The synthesis of potent peptide analogues is also a commonly used strategy for mucosal delivery, with aims of increased stability of enzymatic degradation and increased lipophilicity. Several standard approaches include replacing typical amino acids with their corresponding o-amino acids, derivatizing the N-terminus or C-terminus, and cyclization. Several successful examples are metkephamid, desmopressin, and a few LHRH agonists. ... 

One of the most popular methods of single-stage amino acid derivatization at present is their conversion to N,0 S) err-butyldimethylsilyl derivatives [the reagent rert-butyldimethylsilyl trifluoroacetamide (MTBSTFA) or its A-Me analog]. Another way, which was proposed at the beginning of the 1970s is based on amino acid interaction with dimethylformamide di-alkylacetals (CH3)2NCH(OR )2 (R = Me, Et, Pr, iso-Pr, Bu, Am) with formation of A-dimethylaminometh-ylene derivatives of amino acids esters ... 

D-enantiomers of amino acids have been frequently reported in various tissues of diverse organisms. A simple and rapid method of separating optical isomers of amino acids on a reverse-phase thin layer chromatography plate is described. Amino acids, derivatized with l-fluoro-2,4-dinitrophenyl-5-L-alanine amide, were spotted onto a reverse-phase thin layer chromatography plate. Acetonitrile in triethylamine-phosphate buffer was used as the developer. 

This detection method has been tested with a series of amino acids derivatized prior to injection with fluorescein isothiocyanate, to yield products that are excited at 488 nm and produce emission at 528 nm (Eq. 12.10) ... 

The synthesis of these heterocycles was approached using two similar strategies. Fmoc-amino acid-derivatized Wang resins were N-deprotected (87) and coupled with either o-nitrobenzoic acid or N-Fmoc-anthranilic acid (88 and 89). Reduction of the nitro group with 2 m Sn( l, /DMF or Fmoc cleavage with piperidine/DMF, respectively, produced 90, which was cyclized with NaOtBu/THF at 60 °C. Extraction of the crude materials yielded 11 different l,4-benzodiazepine-2,5-diones 91 in yields of 45-80% with an average purity of 90% (Scheme 24) [39]. 

Fig. 5. The principle of processing-independent immunoassays. The scheme illustrates the processing from translation of pre-pro-protein in the endoplasmatic reticulum, via intermediates in the Golgi apparatus and early secretory vesicles, to final maturation (see also Fig. 3). Divisions within the protein bars indicate proteolytic cleavage sites. The protuberances on the tops and ends of the bars illustrate different forms of amino acid derivatization. The filled-in areas of the protein bars are the selected processing-independent sequences, toward which the processing-independent immunoassay is developed.

The enantioselective alkylation of A-protected a-amino esters has been studied with many chiral catalysts, including spirocyclic ammonium salt 10A, while (lOB) containing two binaphthyl components is an effective mediator for alkylation of protected glycine under phase-transfer conditions.p-f-Boc-amino acid derivatized with (-l-)-pseu-doephedrine enables enantioselective alkylation of the ensuing amides. - Note the enolate derived from 11 remains chiral, alkylation products are produced in high ee. ... 

The precolumn technique that is most frequently employed today was developed during the early 1980s [32,33]. For this method, The classical Edman reagent phenylisothiocyanate (PITC) is used for amino acid derivatization after hydrolysis. Separation of the PTC amino acids i then accomplished by HPLG, with detection at 254 nm. Although standard Cig columns available Irom a variety of vendors are suitable for separation of the PTC-derivatized amino acids, there are specific columns that have bqen optimized for this purpose (e.g.. Waters). Approximately 0.5 /ug of peptMe should be hydrolyzed for analyses using precolumn derivatization. ... 

Figure 5. Separation of amino acids derivatized with o-phthaldialdehyde (OTA) by reverse-phase chromatography. Extracts of nodules were derivatized according to the procedures described by Hill et al, (51, except the final volume was reduced from 5 mL to 0.5 mL or less and the concentrations of OTA and ethanethiol in the derivaUzing solution were increased to 60 mgjmL and 0.1 mglmLy respectively. A sample volume of 20 fiL was injected on column and the derivatized amino acids were eluted with an increasing gradient of acetonitrile from 12% to 100%.

Chen, F., Zhang, S., Qi, L., and Chen, Y. Chiral capillary electrophoretic separation of amino acids derivatized with 9-fluorenylmethylchloroformate using mixed chiral selectors of 6-cyclodextrin and sodium tamodeoxycholate. Electmphoresis, 27, 2896, 2006. 

Jin, L. J., Rodriguez, 1., and Li, S. R Y, Enantiomeric separation of amino acids derivatized with fluores-ceine isothiocyanate isomer I by micellar electrokinetic chromatography using b- and g-cyclodextrins as chiral selectors. Electrophoresis, 20, 1538, 1999. 

In the GC analysis of amino acids, derivatization processes are necessary and can be a disadvantage All reactive groups of the ammo acids have to be denvatized for a satisfactory GC analysis. Esterification of the carboxylic group is acid-catalyzed, which causes the degradation of glutamine (the most abundant ammo acid in the CNS) and asparagine to their dicarboxylic acid counterparts (glutamate and aspartate). An alternative derivatization ap-... 

A number of groups have shown how enantiomeric resolution of amino acids derivatized with non-chiral reagents is possible in SFC with chiral stationary phases. N-Acetylamino acid t-butyl ester racemates were rapidly resolved [17] on (N-formyl-L-valylamino)propyl silica with CO2 modified with methanol, acetonitrile and diethyl ether. A similar stationary phase allowed (18 rapid (< 5 min) separation of racemic N-4-nitrobenzoyl-amino acid isopropyl esto-s with methanol-modified CO2 the enantioselectivity in SFC was comparable with that in HPLC with isopropanol/n-hexane as mobile phase. Capillary column SFC on polysiloxane stationary phases containing chiral side chains has been employed... 

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