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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.

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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.


Normalized fluorescence emission spectra of compounds 1 and 2 incorporated in liposomes of DPPC, Egg-PC and DODAB.
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Figure 8: Normalized fluorescence emission spectra of compounds 1 and 2 incorporated in liposomes of DPPC, Egg-PC and DODAB.

Mentions: Fluorescence experiments of both compounds encapsulated in liposomes of DPPC, DODAB and Egg-PC were carried out (Figure 8), in both gel (below Tm) and liquid-crystalline (above Tm) phases. The melting transition temperature of Egg-PC is very low [31] and this lipid is in the fluid liquid-crystalline phase at room temperature. Fluorescence spectra of compound 1 incorporated in liposomes (Figure 8, Table 3) are roughly similar to the one obtained in pure water, regarding the band shape and maximum emission wavelength. Compound 2 in liposomes presents emission spectra similar to those in polar solvents, significantly blue-shifted relative to water. In Egg-PC, a band enlargement is observed in the blue region, which can indicate two different locations of compound 2 in these liposomes, one deep in the hydrophobic region and another more close to the lipid polar heads.


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)

Normalized fluorescence emission spectra of compounds 1 and 2 incorporated in liposomes of DPPC, Egg-PC and DODAB.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: Normalized fluorescence emission spectra of compounds 1 and 2 incorporated in liposomes of DPPC, Egg-PC and DODAB.
Mentions: Fluorescence experiments of both compounds encapsulated in liposomes of DPPC, DODAB and Egg-PC were carried out (Figure 8), in both gel (below Tm) and liquid-crystalline (above Tm) phases. The melting transition temperature of Egg-PC is very low [31] and this lipid is in the fluid liquid-crystalline phase at room temperature. Fluorescence spectra of compound 1 incorporated in liposomes (Figure 8, Table 3) are roughly similar to the one obtained in pure water, regarding the band shape and maximum emission wavelength. Compound 2 in liposomes presents emission spectra similar to those in polar solvents, significantly blue-shifted relative to water. In Egg-PC, a band enlargement is observed in the blue region, which can indicate two different locations of compound 2 in these liposomes, one deep in the hydrophobic region and another more close to the lipid polar heads.

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.