Enhancement of the fluorescence and stability of o-phthalaldehyde-derived isoindoles of amino acids using hydroxypropyl-beta-cyclodextrin.
Addition of hydroxypropyl-beta-cyclodextrin to o-phthalaldehyde (OPA)-amino acid-thiol reaction mixtures is shown to cause significant enhancement of the fluorescence of the isoindole product for a wide range of amino acids, with the largest effects observed in the cases of glycine and lysine. The largest enhancement observed was a factor of 2.67 in the case of the derivative of glycine. This fluorescence enhancement is the result of the formation of a 1:1 host:guest inclusion complex between the isoindole and the cyclodextrin. Relatively small association constants of 44 and 130 M(-1) were obtained for the inclusion of the derivatives of glycine and lysine, respectively. Inclusion of the isoindole derivative into hydroxypropyl-beta-cyclodextrin was also found to result in a significant stabilization of the isoindole derivatives, contrary to what has been previously reported for inclusion into beta-cyclodextrin. For example, the lifetime of the lysine derivative was found to increase from 42 to 222 min, a factor of 5.3. These results have potential applications in fluorescence-based HPLC and high-performance capillary electrophoresis amino acid analysis methods using OPA derivation. Addition of hydroxypropyl-beta-cyclodextrin to the reaction mixture results in an increase in both the fluorescence and the stability of the isoindole product, providing potentially significant improvements to the method.
Wagner
Brian D
BD
Department of Chemistry, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3. bwagner@upei.ca
McManus
Gregory J
GJ
D000073738:2-Hydroxypropyl-beta-cyclodextrin; D000596:Amino Acids / Q000737:chemistry* / Q000187:drug effects; D003505:Cyclodextrins / Q000737:chemistry* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007211:Indoles / Q000032:analysis*; D007700:Kinetics; D015394:Molecular Structure; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013997:Time Factors; D047392:beta-Cyclodextrins; D009764:o-Phthalaldehyde / Q000032:analysis*
D000596:Amino Acids; D003505:Cyclodextrins; D007211:Indoles; D047392:beta-Cyclodextrins; D000073738:2-Hydroxypropyl-beta-cyclodextrin; D009764:o-Phthalaldehyde; C031215:betadex