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New potential antitumoral fluorescent tetracyclic thieno[3,2-b]pyridine derivatives: interaction with DNA and nanosized liposomes.

Castanheira EM, Carvalho MS, Rodrigues AR, Calhelha RC, Queiroz MJ - Nanoscale Res Lett (2011)

Bottom Line: Fluorescence properties of two new potential antitumoral tetracyclic thieno[3,2-b]pyridine derivatives were studied in solution and in liposomes of DPPC (dipalmitoyl phosphatidylcholine), egg lecithin (phosphatidylcholine from egg yolk; Egg-PC) and DODAB (dioctadecyldimethylammonium bromide).Compound 1, pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, exhibits reasonably high fluorescence quantum yields in all solvents studied (0.20 ≤ ΦF ≤ 0.30), while for compound 2, 3-[(p-methoxyphenyl)ethynyl]pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, the values are much lower (0.01 ≤ ΦF ≤ 0.05).Studies of incorporation of both compounds in liposomes of DPPC, Egg-PC and DODAB revealed that compound 2 is mainly located in the hydrophobic region of the lipid bilayer, while compound 1 prefers a hydrated and fluid environment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre of Physics (CFUM), University of Minho, Campus de Gualtar, Braga, 4710-057, Portugal. ecoutinho@fisica.uminho.pt.

ABSTRACT
Fluorescence properties of two new potential antitumoral tetracyclic thieno[3,2-b]pyridine derivatives were studied in solution and in liposomes of DPPC (dipalmitoyl phosphatidylcholine), egg lecithin (phosphatidylcholine from egg yolk; Egg-PC) and DODAB (dioctadecyldimethylammonium bromide). Compound 1, pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, exhibits reasonably high fluorescence quantum yields in all solvents studied (0.20 ≤ ΦF ≤ 0.30), while for compound 2, 3-[(p-methoxyphenyl)ethynyl]pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, the values are much lower (0.01 ≤ ΦF ≤ 0.05). The interaction of these compounds with salmon sperm DNA was studied using spectroscopic methods, allowing the determination of intrinsic binding constants, Ki = (8.7 ± 0.9) × 103 M-1 for compound 1 and Ki = (5.9 ± 0.6) × 103 M-1 for 2, and binding site sizes of n = 11 ± 3 and n = 7 ± 2 base pairs, respectively. Compound 2 is the most intercalative compound in salmon sperm DNA (35%), while for compound 1 only 11% of the molecules are intercalated. Studies of incorporation of both compounds in liposomes of DPPC, Egg-PC and DODAB revealed that compound 2 is mainly located in the hydrophobic region of the lipid bilayer, while compound 1 prefers a hydrated and fluid environment.

No MeSH data available.


Stern-Volmer plots for quenching with iodide ion of compounds 1 and 2 for [DNA]/[compound] = 200 (A) and corresponding modified Stern-Volmer plots (B).
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Figure 7: Stern-Volmer plots for quenching with iodide ion of compounds 1 and 2 for [DNA]/[compound] = 200 (A) and corresponding modified Stern-Volmer plots (B).

Mentions: Anionic quenchers can be useful in distinguishing between DNA binding modes [9,10]. Compounds that are bound at the DNA surface (groove binding or electrostatic binding) are more accessible and emission from these molecules can be quenched more efficiently. Fluorescence quenching measurements using iodide ion showed that the usual Stern-Volmer plots (plots of the fluorescence intensity ratio in the absence, I0, and presence, I, of quencher vs. quencher concentration) are not linear and exhibit a downward curvature (Figure 7A). This indicates that some compound molecules are not accessible to the anionic quencher, being intercalated between DNA base pairs. The modified Stern-Volmer plot [30] (Equation 3) allows the determination of the fraction of compound molecules accessible to quencher,(3)


New potential antitumoral fluorescent tetracyclic thieno[3,2-b]pyridine derivatives: interaction with DNA and nanosized liposomes.

Castanheira EM, Carvalho MS, Rodrigues AR, Calhelha RC, Queiroz MJ - Nanoscale Res Lett (2011)

Stern-Volmer plots for quenching with iodide ion of compounds 1 and 2 for [DNA]/[compound] = 200 (A) and corresponding modified Stern-Volmer plots (B).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211472&req=5

Figure 7: Stern-Volmer plots for quenching with iodide ion of compounds 1 and 2 for [DNA]/[compound] = 200 (A) and corresponding modified Stern-Volmer plots (B).
Mentions: Anionic quenchers can be useful in distinguishing between DNA binding modes [9,10]. Compounds that are bound at the DNA surface (groove binding or electrostatic binding) are more accessible and emission from these molecules can be quenched more efficiently. Fluorescence quenching measurements using iodide ion showed that the usual Stern-Volmer plots (plots of the fluorescence intensity ratio in the absence, I0, and presence, I, of quencher vs. quencher concentration) are not linear and exhibit a downward curvature (Figure 7A). This indicates that some compound molecules are not accessible to the anionic quencher, being intercalated between DNA base pairs. The modified Stern-Volmer plot [30] (Equation 3) allows the determination of the fraction of compound molecules accessible to quencher,(3)

Bottom Line: Fluorescence properties of two new potential antitumoral tetracyclic thieno[3,2-b]pyridine derivatives were studied in solution and in liposomes of DPPC (dipalmitoyl phosphatidylcholine), egg lecithin (phosphatidylcholine from egg yolk; Egg-PC) and DODAB (dioctadecyldimethylammonium bromide).Compound 1, pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, exhibits reasonably high fluorescence quantum yields in all solvents studied (0.20 ≤ ΦF ≤ 0.30), while for compound 2, 3-[(p-methoxyphenyl)ethynyl]pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, the values are much lower (0.01 ≤ ΦF ≤ 0.05).Studies of incorporation of both compounds in liposomes of DPPC, Egg-PC and DODAB revealed that compound 2 is mainly located in the hydrophobic region of the lipid bilayer, while compound 1 prefers a hydrated and fluid environment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre of Physics (CFUM), University of Minho, Campus de Gualtar, Braga, 4710-057, Portugal. ecoutinho@fisica.uminho.pt.

ABSTRACT
Fluorescence properties of two new potential antitumoral tetracyclic thieno[3,2-b]pyridine derivatives were studied in solution and in liposomes of DPPC (dipalmitoyl phosphatidylcholine), egg lecithin (phosphatidylcholine from egg yolk; Egg-PC) and DODAB (dioctadecyldimethylammonium bromide). Compound 1, pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, exhibits reasonably high fluorescence quantum yields in all solvents studied (0.20 ≤ ΦF ≤ 0.30), while for compound 2, 3-[(p-methoxyphenyl)ethynyl]pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, the values are much lower (0.01 ≤ ΦF ≤ 0.05). The interaction of these compounds with salmon sperm DNA was studied using spectroscopic methods, allowing the determination of intrinsic binding constants, Ki = (8.7 ± 0.9) × 103 M-1 for compound 1 and Ki = (5.9 ± 0.6) × 103 M-1 for 2, and binding site sizes of n = 11 ± 3 and n = 7 ± 2 base pairs, respectively. Compound 2 is the most intercalative compound in salmon sperm DNA (35%), while for compound 1 only 11% of the molecules are intercalated. Studies of incorporation of both compounds in liposomes of DPPC, Egg-PC and DODAB revealed that compound 2 is mainly located in the hydrophobic region of the lipid bilayer, while compound 1 prefers a hydrated and fluid environment.

No MeSH data available.