R. Gargallo et al., Study of the protonation equilibria of a transfer ribonucleic acid by means of a multivariate curve resolution method, QUIM ANAL, 18(1), 1999, pp. 73-81
The protonation equilibria in a natural macromolecule (a mixture of yeast t
ransfer ribonucleic acids, tRNAs) were studied by means of spectroscopicall
y monitored acid-base titrations (UV spectrophotometry, circular dichroism
and molecular fluorescence). Experimental data were analyzed by a soft-mode
ling multivariate curve resolution procedure that allows the detection of t
he secondary effects arising from the macromolecular nature of tRNA, and th
e calculation of pK(a) values.
Three spectroscopically different species were detected, associated with th
e acid-base equilibria of the different nitrogenated bases present in the p
olynucleotide. For the transition observed at acidic pH values a certain de
pendence of the pK(a) with the degree of protonatian was found, which war a
ttributed to the secondary effects. On the other hand, no dependence was ob
served in the second transition, at basic pH values. From the simultaneous
data analysis of UV and fluorescence spectra, the transition at acidic pH v
alues was resolved into two different contributions, related to the differe
nt nature of the bases involved.