The results presented in this work demonstrate the high complexity of chemical reactions involving species with multiple acid-base equilibria. For the case study investigated here, it was necessary to consider two radical species for tryptophan (Trp(-H)˙ and Trp˙+) and three fractions for uric acid (H3Ur, H2Ur- and HUr2-) in order to properly reproduce the experimental results. At pH = 7.4, two...

The conformation of ten purified tRNAs from Escherichia Coli has been investigated by means of the photo-induced cross-linking of 4Srd8 and Cyd13, which is sensitive to the juxtaposition of the two bases. Three tRNAs photo-react abnormally slowly; tRNAPhe, tRNAMet/m a and tRNAVal/2; a comparison with normally reacting species suggests that base 47 (Urd or modified Urd) is involved in a tertiary...

A high sensitive electrochemical nanostructure sensor based on graphene oxide/Fe3O4@SiO2 nanocomposite modified graphite screen printed electrode (GO/Fe3O4@SiO2/SPE) has been developed for trace analysis of acetaminophen. The electrochemical study of the modified electrode, as well as its efficiency for simultaneous voltammetric oxidation of acetaminophen and tryptophan is described. Compared w...

The site-specific basicities of imatinib (Gleevec, a new signal transduction inhibitor drug of chronic myeloid leukemia) and two of its fragment compounds were quantitated in terms of protonation macroconstants, microconstants, and group constants by NMR-pH and pH-potentiometric titrations. Sequential protonation of imatinib follows the N(34), N(11), N(31), N(13) order, in which N(11) and N(31)...

We investigated how changes in tryptophan pyrrolase activity and tryptophan loads affect the breakdown of tryptophan by tryptophan pyrrolase. Breakdown of tryptophan was estimated by injecting rats with [ring-ZJ%]tryptophan and measuring respiratory 14C02. We concluded, contrary to previous reports, that induction of tryptophan pyrrolase definitely will increase the rate of tryptophan breakdown...

Protonated nucleobases have significant roles in facilitating catalytic functions of RNA, and in stabilizing different structural motifs. Reported pKa values of nucleobase protonation suggest that the population of neutral nucleobases is 10(3)-10(4) times higher than that of protonated nucleobases under physiological conditions (pH ∼ 7.4). Therefore, a molecular level understanding of various p...

Spectral changes of bovine serum albumin (BSA) in the presence of dipicolinic acid (DPA) were studied with UV/Vis absorption and fluorescence spectroscopy. The change in UV/vis spectra of BSA in the presence of DPA indicated the protein weakly interacting with DPA. The DPA quenching to the fluorescence of BSA leads to the calculation of the BAS-DPA association constant K of 8.9 x 104 Lmol-1 at ...

Bovine, human and rat serum albumins were defatted and palmitic acid, oleic acid and lauric acid added in various molar ratios. The binding of L-tryptophan to these albumins was measured at 20 degrees C in a 0.138 M salt solution at pH 7.4, by using an ultrafiltration technique, and analysed in terms of n, the number of available tryptophan-binding sites per albumin molecule, with apparent asso...