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Tryptophan as a Probe for Acid-base Equilibria in Peptides by Cássia Alessandra Marquezin; Izaura Yoshico Hirata; Luiz Juliano; Amando Siuiti Ito is a Biochemistry, Genetics and Molecular Biology article available to read on EtoBox.

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We present results of time resolved fluorescence measurements performed in Tryptophan (Trp) derivatives and Trp-containing peptides in the pH range 3.0-11.0. For each compound a set of decay profiles measured in a given range of pH values was examined as a whole, using the global analysis technique. The data were fitted to two or three lifetime components and the analysis allowed the monitoring of the changes in the concentration of the different species contributing to the total fluorescence in that pH interval. The decay components were sensitive to the ionization state of groups neighboring the indol ring, and pK values for the equilibrium between protonated and deprotonated species were obtained from the preexponential factor of the lifetime components. In Trp, protonation of the amino terminal of the rotamer having electron transfer rate comparable to fluorescence decay rates was responsible for the interconvertion of a long lifetime component, to the 2.9 ns component usually observed in neutral pH. Trpbond;X peptides also have a single rotamer dominating the decay that is quenched by NH(3) (+). X-Trp peptides seem to be conformationally less restricted, and it is possible tha

Who reads Tryptophan as a Probe for Acid-base Equilibria in Peptides?

Author

Cássia Alessandra Marquezin; Izaura Yoshico Hirata; Luiz Juliano; Amando Siuiti Ito

Publisher

Wiley (John Wiley & Sons); John Wiley & Sons Inc.; Wiley (ISSN 0006-3525)

Published

2003

Language

EN

Field

Biochemistry, Genetics and Molecular Biology (Life Sciences)