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Spectroscopic study of porphyrin-caffeine interactions.

Makarska-Bialokoz M - J Fluoresc (2012)

Bottom Line: The association constants were calculated using curve-fitting procedure (K(AC) of the order of magnitude of 10(3) mol(-1)).Whereas the emission spectra point at the presence of the fluorescence quenching effect testifying for the partial inactivation of the porphyrin molecule.The fluorescence quenching constants were calculated from Stern-Volmer plots.

View Article: PubMed Central - PubMed

Affiliation: Department of Inorganic Chemistry, Maria Curie-Sklodowska University, Lublin, Poland. makarska@hektor.umcs.lublin.pl

ABSTRACT
The association between water-soluble porphyrins: 4,4',4″,4'''-(21 H,23 H-porphine-5,10,15,20-tetrayl)tetrakis-(benzoic acid) (H(2)TCPP), 5,10,15,20-tetrakis(4-sulfonatophenyl)-21 H,23 H-porphine (H(2)TPPS(4)), 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21 H,23 H-porphine tetra-p-tosylate (H(2)TTMePP), 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21 H,23 H-porphine tetra-p-tosylate (H(2)TMePyP), the Cu(II) complexes of H(2)TTMePP and H(2)TMePyP, as well as chlorophyll a with caffeine (1,3,7-trimethylxanthine) has been studied analysing their absorption and emission spectra in aqueous (or acetone in case of chlorophyll a) solution. During the titration by caffeine the porphyrins absorption spectra undergo the evolution - the bathochromic effect can be observed as well as the hypochromicity of the Soret maximum. The association constants were calculated using curve-fitting procedure (K(AC) of the order of magnitude of 10(3) mol(-1)). Whereas the emission spectra point at the presence of the fluorescence quenching effect testifying for the partial inactivation of the porphyrin molecule. The fluorescence quenching constants were calculated from Stern-Volmer plots. The results obtained show that caffeine can interact with water-soluble porphyrins and through formation of stacking complexes is able to quench their ability to emission.

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Evolution of chlorophyll a absorption spectrum during titration by caffeine. The dependence of absorbance versus chlorophyll a concentration for the process presented. The concentrations of chlorophyll a and caffeine in solution changed in the range 7.34 – 4.31 (× 10-7 mol dm-3) and 0–4.13 × 10-4 mol dm-3, respectively
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Fig4: Evolution of chlorophyll a absorption spectrum during titration by caffeine. The dependence of absorbance versus chlorophyll a concentration for the process presented. The concentrations of chlorophyll a and caffeine in solution changed in the range 7.34 – 4.31 (× 10-7 mol dm-3) and 0–4.13 × 10-4 mol dm-3, respectively

Mentions: Acetone solution of chlorophyll a was titrated both by acetone and water in order to separate the influence of these solvents on absorption and emission spectra of this compound. The slight deviations from Beer-Lambert law appearing in absorption spectrum of chlorophyll a (Fig. 4) can testify either for the minimal interactions with caffeine or for the time dependence occurring during this reaction or, what seems the most likely, for the different comparing to other porphyrins mechanism of interactions.Fig. 4


Spectroscopic study of porphyrin-caffeine interactions.

Makarska-Bialokoz M - J Fluoresc (2012)

Evolution of chlorophyll a absorption spectrum during titration by caffeine. The dependence of absorbance versus chlorophyll a concentration for the process presented. The concentrations of chlorophyll a and caffeine in solution changed in the range 7.34 – 4.31 (× 10-7 mol dm-3) and 0–4.13 × 10-4 mol dm-3, respectively
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3473192&req=5

Fig4: Evolution of chlorophyll a absorption spectrum during titration by caffeine. The dependence of absorbance versus chlorophyll a concentration for the process presented. The concentrations of chlorophyll a and caffeine in solution changed in the range 7.34 – 4.31 (× 10-7 mol dm-3) and 0–4.13 × 10-4 mol dm-3, respectively
Mentions: Acetone solution of chlorophyll a was titrated both by acetone and water in order to separate the influence of these solvents on absorption and emission spectra of this compound. The slight deviations from Beer-Lambert law appearing in absorption spectrum of chlorophyll a (Fig. 4) can testify either for the minimal interactions with caffeine or for the time dependence occurring during this reaction or, what seems the most likely, for the different comparing to other porphyrins mechanism of interactions.Fig. 4

Bottom Line: The association constants were calculated using curve-fitting procedure (K(AC) of the order of magnitude of 10(3) mol(-1)).Whereas the emission spectra point at the presence of the fluorescence quenching effect testifying for the partial inactivation of the porphyrin molecule.The fluorescence quenching constants were calculated from Stern-Volmer plots.

View Article: PubMed Central - PubMed

Affiliation: Department of Inorganic Chemistry, Maria Curie-Sklodowska University, Lublin, Poland. makarska@hektor.umcs.lublin.pl

ABSTRACT
The association between water-soluble porphyrins: 4,4',4″,4'''-(21 H,23 H-porphine-5,10,15,20-tetrayl)tetrakis-(benzoic acid) (H(2)TCPP), 5,10,15,20-tetrakis(4-sulfonatophenyl)-21 H,23 H-porphine (H(2)TPPS(4)), 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21 H,23 H-porphine tetra-p-tosylate (H(2)TTMePP), 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21 H,23 H-porphine tetra-p-tosylate (H(2)TMePyP), the Cu(II) complexes of H(2)TTMePP and H(2)TMePyP, as well as chlorophyll a with caffeine (1,3,7-trimethylxanthine) has been studied analysing their absorption and emission spectra in aqueous (or acetone in case of chlorophyll a) solution. During the titration by caffeine the porphyrins absorption spectra undergo the evolution - the bathochromic effect can be observed as well as the hypochromicity of the Soret maximum. The association constants were calculated using curve-fitting procedure (K(AC) of the order of magnitude of 10(3) mol(-1)). Whereas the emission spectra point at the presence of the fluorescence quenching effect testifying for the partial inactivation of the porphyrin molecule. The fluorescence quenching constants were calculated from Stern-Volmer plots. The results obtained show that caffeine can interact with water-soluble porphyrins and through formation of stacking complexes is able to quench their ability to emission.

Show MeSH
Related in: MedlinePlus