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Cambrón G, Sevilla JM, Pineda T, et al. Fluorescence of the Schiff bases of pyridoxal and pyridoxal 5'-phosphate withL-isoleucine in aqueous solutions. J Fluoresc. 1996;6(1):1-6doi: 10.1007/BF00726720.
Cambrón, G., Sevilla, J. M., Pineda, T., & Blázquez, M. (1996). Fluorescence of the Schiff bases of pyridoxal and pyridoxal 5'-phosphate withL-isoleucine in aqueous solutions. Journal of fluorescence, 6(1), 1-6. https://doi.org/10.1007/BF00726720
Cambrón, G, et al. "Fluorescence of the Schiff bases of pyridoxal and pyridoxal 5'-phosphate withL-isoleucine in aqueous solutions." Journal of fluorescence vol. 6,1 (1996): 1-6. doi: https://doi.org/10.1007/BF00726720
Cambrón G, Sevilla JM, Pineda T, Blázquez M. Fluorescence of the Schiff bases of pyridoxal and pyridoxal 5'-phosphate withL-isoleucine in aqueous solutions. J Fluoresc. 1996 Mar;6(1):1-6. doi: 10.1007/BF00726720. PMID: 24226991.
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J Fluoresc. 1996 Mar;6(1):1-6. doi: 10.1007/BF00726720.

Fluorescence of the Schiff bases of pyridoxal and pyridoxal 5'-phosphate withL-isoleucine in aqueous solutions.

Journal of fluorescence

G Cambrón, J M Sevilla, T Pineda, M Blázquez

Affiliations

  1. Departamento de Quimica Fisica y Termodinámica Aplicada, Facultad de Ciencias, Universidad de Córdoba, 14004, Córdoba, Spain.

PMID: 24226991 DOI: 10.1007/BF00726720

Abstract

The present study reports on the absorption and emission properties of the Schiff bases formed by pyridoxal and pyridoxal 5'-phosphate withL-isoleucine in aqueous solutions. Species protonated at the imine and ring nitrogen are the most fluorescent in both Schiff bases with a quantum yield of 0.02, i.e., 20-fold the value found for species in alkaline solutions. In agreement with other studies, species protonated at the imine nitrogen shows an emission around 500 nm upon excitation at 415 nm. In contrast to previous observations on other PLP Schiff bases, emissions at 560 nm (PL-Ile) and 540 nm (PLP-Ile) are observed upon excitation at 365 and 415 nm, respectively. The emission at 470 nm found in PLP-Ile Schiff base upon excitation at 355 nm is ascribed to a multipolar monoprotonated species. An estimation for the pK a of the imine in the excited state ( ≈ 8.5) for both Schiff bases is also reached. Our results suggest that fast protonation reactions on the excited state are responsible for the observed fluorescence. These effects, in which the hydrogen bond and the phosphate group seem to play a role, could be extended to understanding coenzyme environments in proteins.

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