Synthesis, absorption and fluorescence spectral characteristics of trinucleus dimethine cyanine dyes as fluorescent probes for DNA detection

ARTICLE

Synthesis, absorption and fluorescence spectral characteristics of trinucleus dimethine cyanine dyes as fluorescent probes for DNA detection

Jun-Jie Su^I; Lan-Ying WangI, ^*; Xiang-Han Zhang^I; Yi-Le Fu^I; Yi Huang^II; Yong-Sheng Wei^II

^IKey Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), College of Chemistry and Materials Science, Northwest University, Xi'an 710069, People's Republic of China

^IIDepartment of Chemistry, Xianyang Normal University, Xianyang, Shaanxi 712000, China

ABSTRACT

The preparation of six trinucleus dimethine cyanine dyes with pyridine nucleus obtained by the condensation of trimethylpyridinium iodides with heterocyclic aromatic aldehyde was described. The absorption and fluorescence properties of the dyes were studied in different polarity solvents. Blue shift of the maxima absorption of the dyes was observed with the increase of solvents polarity. The fluorescence properties of the dyes in solution and in presence of DNA were studied. Significant enhancement of the fluorescent quantum yield was observed in four dyes in the presence of DNA. Specially, one of six dyes emitted weak fluorescence in Tris-HCl buffer, but displayed bright fluorescence in the presence of DNA.

Keywords: trinucleus dimethine cyanine dyes, DNA, absorption properties, fluorescence properties, fluorescent dyes

RESUMO

Neste trabalho descreve-se a preparação de seis corantes cianina dimetina trinucleares com núcleos de piridina, obtidos a partir da condensação de iodeto de trimetilpiridínio com aldeídos aromáticos heterocíclicos. As propriedades de absorção e fluorescência dos corantes foram estudadas em solventes com polaridades diferentes. O deslocamento hipsocrômico dos máximos de absorção dos corantes foi observado com o aumento da polaridade do solvente. Foram estudadas as propriedades fluorescentes dos corantes em solução e na presença de DNA. Foi observado um aumento significativo do rendimento quântico de fluorescência na presença de DNA para quatro corantes.. Em particular, um dos corantes emite fluorescência fraca no tampão Tris-HCl, apresentando contudo fluorescência intensa na presença de DNA.

Introduction

Methine cyanine dyes have been widely researched and explored as sensitizers in photography¹ and as optical recording materials in laser disk.² Recently, methine cyanine dyes have attracted attention owing to their excellent fluorescence properties^3-5 as well as their potential applications in probes for DNA in living cells.^6-10 From the applications of cyanine dyes it is known that the optical properties of cyanine dyes are often influenced by their conjugated systems and the solution environment. Trinucleus dimethine cyanine dyes are large conjugated systems, which contain three heteroaromatic rings joined by two vinyl chains. However the synthesis of trinucleus dimethine cyanine dyes and their applications as fluorescent probe were rarely reported.^11,12 Our previous efforts have been devoted to developing series of cyanine dyes and styryl dyes.^13-17

In this paper, six trinucleus dimethine cyanine dyes with pyridine nucleus, four dyes of which were novel, were synthesized in water or ethanol via the condensation of appropriate heteroaromatic aldehydes with quaternary salts of heterocyclic compounds containing active methyl groups. The influence of different solvents on spectral properties of the trinucleus dimethine cyanine dyes was studied by UV-Vis and fluorescence spectroscopy. A further objective of this study was to investigate the fluorescence spectral properties of prepared trinucleus dimethine cyanine dyes both in solution and in the DNA presence, exploring their future applications as fluorescence probe.

Experimental

General

All reagents were obtained from commercial sources and used without further purification. All chemicals were of analytical grade. Melting points were taken on a XT-4 micromelting apparatus and uncorrected. IR spectra in cm^-1 were recorded on Shimadzu IRPrestige-21 spectrometer and Bruker Equiox-55 spectrometer. ¹H NMR spectra were recorded at 400 MHz on a Varian Inova-400 spectrometer and chemical shifts were reported relative to internal Me₄Si. ¹³C NMR spectra were recorded at 100 MHz on a Varian Inova-400 spectrometer and chemical shifts were reported relative to internal Me₄Si. Elemental analysis was performed with Vario EL-III instrument. The electron impact (EI) mass spectra were recorded at 70 eV with a GCMS-QP2010 system equipped with the solid sample direct insertion probe. The absorption spectra were recorded on a Shimadzu UV-1700 UV-Vis spectrometer. Fluorescence measurements were carried out on a Hitachi F-4500 spectrofluorimeter.

Measurements of the spectral properties of the dyes in different solvents

The dye stock solutions (5.0×10^-4 mol L^-1 in dimethylsulfoxide (DMSO)) were diluted with different solvents and resulted in working solutions of dyes (2.0×10^-5 mol L^-1). The absorption spectra were examined at room temperature in different solvents and recorded using 1 cm quartz cells on a Shimadzu UV-1700 UV-Vis spectrometer. Fluorescence measurements were carried out at room temperature on a Hitachi F-4500 spectrofluorimeter in 1 cm quartz cells. Fluorescence emission was excited at the maximum of the absorption. The absorption and fluorescence spectral data were listed in Table 1.

Measurements of spectral properties of the dyes in the presence of DNA

Dye stock solutions (2.0×10^-4 mol L^-1) were prepared by dissolving the dyes in DMSO and further diluted with Tris-HCl buffer (pH 7.4) to result in working solutions of dyes (1.0×10^-5 mol L^-1). Stock solution of DNA was prepared by dissolving salmon sperm DNA in 0.05 mol L^-1 Tris-HCl buffer. The concentration of DNA in stock solution was 3.1×10^-3 mol L^-1 base pairs (bp). The fluorescence of dyes in the presence of DNA was tested by adding 0.5 mL DNA solution (3.1×10^-3 mol L^-1 bp) into 1.0 mL 1.0×10^-5 mol L^-1 working solutions of dyes. All working solutions were prepared immediately before the experiment.

The absorption spectra were examined at room temperature in different solvents and recorded using 1 cm quartz cells on a Shimadzu UV-1700 UV-Vis spectrometer. Fluorescence measurements were carried out at room temperature on a Hitachi F-4500 spectrofluorimeter in 1 cm quartz cells. Fluorescence emission was excited at the maximum of the fluorescence excitation spectrum. The absorption and fluorescence spectral date were listed in Table 2 and Table 3.

Preparation of trimethyl pyridine quaternary salt 2a-2b

A mixture of 3.54 g (0.033 mol) 1a or 1b with 4.71 g (0.033 mol) CH₃I was refluxed for 20 h. After cooling, the product was filtered off and purified by recrystallization from ethanol. Pyridine quaternary salt 2a: 5.1 g, yield 62%, mp 130-131 °C. 2b: 5.4 g. Yield 66%, mp 235-236 °C.

Preparation of dyes 3a-3b

A mixture of 2a or 2b (0.10 g, 0.4 mmol), indole-3-carboxaldehyde (0.15 g, 1.0 mmol) and 5 drops of piperidine was refluxed for 24 h in 8 mL ethanol. After cooling, ether was added and the product was filtered off, washed with ether and recrystallized from ethanol:water = 9:1. Yield: 3a: 0.15 g (84%), 3b: 0.16 g (79%).

Preparation of dyes 3c-3d

The dyes 3c-3d were synthesized according to a revised literature procedure.¹² A mixture of 2a or 2b (0.10 g, 0.4 mmol), 1-methylpyrrole-2-carboxaldehyde (0.20 g, 1.0 mmol) and 5 drops of piperidine was refluxed for 20 h in 5 mL ethanol. After cooling, ether was added and the product was filtered off, washed with ether and recrystallized from ethanol:water = 9:1. Yield: 3c: 0.17 g (86%), 3d: 0.15 g (76%).

Preparation of dyes 3e-3f

Quaternary salts 2a or 2b (0.2 g, 0.8 mmol) and furaldehyde (0.62 g, 6.4 mmol) were dissolved in 18 mL H₂O. NaOH (20%, 4.6 mL) was added with stirring over 30 min. After 1 h, the product was filtered off, washed with cold water and recrystallized from water. Yield: 3e: 0.22 g (69%), 3f: 0.27 g (83%).

1-Methyl-2,4-bis[2-(indole-3-yl)vinyl]pyridinium iodide (3a)

Orange-red crystals with metallic luster, mp 172 ºC (decomposition), ¹H NMR (DMSO-d₆, 400 MHz): δ 4.21 (s, 3H, N⁺CH₃), 7.20-7.32 (m, 6H, Ar-H, CH=CH), 7.52-7.54 (m, 2H, Ar-H), 7.89 (d, 1H, J 6.8 Hz, pyridine-H), 7.91-7.92 (m, 1H, Ar-H), 8.10-8.19 (m, 2H, CH=CH), 8.19-8.25 (m, 3H, indole-H, CH=CH), 8.48 (s, 1H, pyridine-H), 8.54 (d, 1H, J 6.8 Hz, pyridine-H), 11.84 (s, 1H, indole N-H), 11.96 (s, 1H, indole N-H). ¹³C NMR (DMSO-d₆, 100 MHz): δ 43.6, 110.2, 112.1, 113.0, 113.1, 116.7, 117.0, 117.6, 119.7, 120.0, 120.4, 120.6, 122.3, 122.4, 124.5, 131.1, 131.3, 134.3, 136.1, 136.8, 137.0, 143.5, 152.1. IR ν_max/cm^-1 (KBr) 3400 (m, ν_=NH), 3068 (ν_=C-H), 1597, 1552 (ν_C=C), 1517, 1492 1423 (s, ν_C=C, ν_C=N), 1367, 1315,1238, 1128, 1107 (δ_CH), 957, 744 (m, δ_=CH). MS: EI (70 ev) m/z (%): 361 (58 M - CH₃I), 360 (100 M - CH₃I - H), 142, 127. UV-Vis Λ_max/nm (methanol) 465. Found: C, 59.0; H, 4.43; N, 7.56. Calc. for C₂₆H₂₂N₃I·3/2H₂O (530.3 g mol^-1): C, 58.9; H, 4.72; N, 7.92%.

1-Methyl-2,6-bis[2-(indole-3-yl)vinyl]pyridinium iodide (3b)

Orange-red crystals with metallic luster, mp 206-207 ºC, ¹H NMR (DMSO-d₆, 400 MHz): δ 4.12 (s, 3H, N⁺CH₃), 7.21-7.29 (m, 6H, Ar-H), 7.51-7.54 (m, 2H, CH=CH), 7.85-7.92 (m, 2H, CH=CH), 8.10-8.24 (m, 5H, Ar-H, pyridine-H), 8.48-8.56 (m, 2H, pyridine-H), 11.86 (s, 1H, indole N-H), 11.97 (s, 1H, indole N-H). ¹³C NMR (DMSO-d₆, 100 MHz): δ 44.0, 110.7, 112.5, 113.3, 113.4, 117.2, 117.4, 118.0, 120.1, 120.4, 120.9, 121.1, 122.7, 122.8, 124.7, 124.9, 131.3, 131.5, 131.7, 134.7, 136.4, 137.1, 137.2, 137.4, 143.9, 152.5. IR ν_max/cm^-1 (KBr) 3389 (m, ν_=NH), 3071 (ν_=C-H), 1598, 1551 (ν_C=C), 1493 1423 (s, ν_C=C, ν_C=N), 1313, 1273, 1237, 1189, 1128 (δ_CH), 956 (s, ν_=CH), 809, 745 (m, δ_=CH). MS: EI (70 ev) m/z (%): 361 (62 M - CH₃I), 360 (100 M - CH₃I - H), 142, 127. UV-Vis λ_max/nm (methanol) 464. Found: C, 61.50; H, 4.23; N, 8.13. Calc. for C₂₆H₂₂N₃I (503.3 g mol^-1): C, 61.85; H, 4.40; N, 8.32%.

1-Methyl-2,4-bis[2-(1-methylpyrrol-2-yl)vinyl]pyridinium iodide (3c)

Red needle crystals, mp 180-181ºC, ¹H NMR (CDCl₃, 400 MHz): δ 3.70-4.01 (m, 9H, pyrrole N-CH₃, N⁺CH₃), 6.20 (s 1H, pyrrole-H), 6.24 (s 1H, pyrrole-H), 6.52 (d, 1H, J 15.2 Hz, CH=CH), 6.73 (s, 1H, pyrrole-H), 6.83 (s, 3H, pyrrole-H), 7.08 (d, 1H, J 16.0 Hz, CH=CH) 7.54 (d, 1H, J 16.0 Hz, CH=CH), 7.68 (d, 1H, J 6.8 Hz, pyridine-H), 8.03 (d, 1H, J 15.2 Hz, CH=CH), 8.28 (d, 1H, J 6.8 Hz, pyridine-H), 8.60 (s, 1H, pyridine-H). ¹³C NMR (DMSO-d₆, 100 MHz): δ 34.0, 34.1, 44.2, 109.6, 109.7, 111.1, 111.3, 112.7, 117.6, 117.9, 119.2, 128.0, 128.1, 128.5, 130.2, 130.2, 130.4, 144.0, 151.6, 151.9.IR ν_max/cm^-1 (KBr) 3440 (m, ν_=NH), 3031 (ν_=C-H), 1597, 1547 (ν_C=C), 1520, 1409 (s, ν_C=C, ν_C=N), 1339, 1264, 1194, 1126, 1086 (δ_CH), 971, 888, 814, 710 (m, δ_=CH). MS: EI(70 ev) m/z (%): 289 (45 M - CH₃I), 288 (100 M - CH₃I - H), 142, 127. UV-Vis Λ_max/nm (methanol) 473. Found: C, 53.91; H, 3.57; N, 5.99. Calc. for C₂₀H₂₂N₃I (431.09 g mol^-1): C, 53.77; H, 3.61; N, 6.27%.

1-Methyl-2,6-bis[2-(1-methylpyrrol-2-yl)vinyl]pyridinium iodide (3d)

Red needle, mp 230 ºC (decomposition), ¹H NMR (CDCl₃, 400 MHz): δ 3.86 (s, 6H, pyrrole N-CH₃), 4.28 (s, 3H, N⁺CH₃), 6.21-6.23 (m, 2H, pyrrole-H), 6.79 (s, 2H, pyridine-H), 6.93-6.99 (m, 4H, CH=CH, pyrrole-H), 7.50 (d, 2H, J 16.0 Hz, CH=CH), 8.08-8.10 (m, 3H, pyridine-H, pyrrole-H). ¹³C NMR (DMSO-d₆, 100 MHz): δ 33.9, 40.9, 109.5, 112.4, 112.7, 121.2, 128.2, 130.3, 141.1, 153.2. IR ν_max/cm^-1 (KBr) 3446 (m, ν_=NH), 3073 (ν_=C-H), 1604, 1559 (ν_C=C), 1469, 1404 (s, ν_C=C, ν_C=N), 1335, 1307, 1228, 1189, 1144, 1090 (δ_CH), 948, 841, 802, 730 (m, δ_=CH). MS: EI (70 ev) m/z (%): 289 (100 M - CH₃I), 288 (58 M - CH₃I - H), 142, 127. UV-Vis Λ_max/nm (methanol) 465. Found: C, 53.88; H, 3.65; N, 6.47. Calc. for C₂₀H₂₂N₃I (431.09 g mol^-1): C, 53.77; H, 3.61; N, 6.27%.

1-Methyl-2,4-bis[2-(furan-2-yl)vinyl]pyridinium iodide (3e)

Yellow powder, mp 254-255 ºC, ¹H NMR (CDCl₃, 400 MHz): δ 4.35 (s, 3H, N⁺CH₃), 6.54-6.55 (m, 2H, furan-H), 6.91-6.98 (m, 4H, furan-H, CH=CH), 7.56-7.58 (m, 2H, furan-H), 7.68-7.82 (m, 3H, CH=CH, pyridine-H), 8.14 (s, 1H, pyridine-H), 9.10 (d, 1H, J 6.8 Hz, pyridine-H). ¹³C NMR (DMSO-d₆, 100 MHz): δ 44.4, 112.8, 115.0, 115.7, 119.8, 120.2, 126.4, 128.3, 144.9, 145.7, 146.0, 150.6, 150.8, 150.9. IR ν_max/cm^-1 (KBr) 3474 (m, ν_=NH), 3083 (ν_=C-H), 1608, 1558 (ν_C=C), 1470, 1442 (s, ν_C=C, ν_C=N), 1386, 1330, 1301 (δ_CH) 1253(ν_asC-O-C), 1069(ν_sC-O-C), 969, 880,751 (m, δ_=CH). MS: EI (70 ev) m/z (%): 264 (11 M - CH₃I), 263 (53 M - CH₃I - H), 142, 127. MS: EI (70 ev) m/z (%): 264 (11 M - CH₃I), 263 (53 M - CH₃I - H), 142, 127. UV-Vis λ_max/nm (methanol) 397. Found: C, 53.64; H, 3.60; N, 3.60. Calc. for C₁₈H₁₆NIO₂ (405.02 g mol^-1): C, 53.35; H, 3.98; N, 3.46%.

1-Methyl-2,6-bis[2-(furan-2-yl)vinyl]pyridinium iodide (3f)

Khaki-colored powder, mp 214-215 ºC, ¹H NMR (CDCl₃, 400 MHz): δ 4.37 (s, 3H, N⁺CH₃), 6.54-6.55 (m, 2H, CH=CH), 6.93-6.94 (m, 2H, furan-H), 7.21-7.27 (m, 2H, CH=CH), 7.50-7.56 (m, 4H, furan-H), 8.08 (d, 2H, J 8.8 Hz, pyridine-H), 8.28 (t, 1H, J 8.8 Hz, pydidine-H). ¹³C NMR (DMSO-d₆, 100 MHz): δ 41.1, 112.7, 115.4, 115.5, 122.8, 128.4, 142.3, 145.7, 150.6, 152.2. IR ν_max/cm^-1 (KBr) 3479 (m, ν_=NH), 3061 (ν_=C-H), 1602, 1561(ν_C=C), 1463, 1384 (s, ν_C=C, ν_C=N), 1305 (δ_CH) 1247(ν_asC-O-C) 1068(ν_sC-O-C), 951, 982, 878, 757 (m, δ_=CH). MS: EI (70 ev) m/z (%): 264 (8 M - CH₃I), 263 (39 M - CH₃I - H), 142, 127. UV-Vis δ_max/nm (methanol) 397. Found: C, 53.31; H, 3.60; N, 3.76. Calc. for C₁₈H₁₆NIO₂ (405.02 g mol^-1): C, 53.35; H, 3.46; N, 3.98%.

Results and Discussion

Synthesis

The trinucleus dimethine cyanine dye was synthesized via the reaction of heteroaromatic aldehydes with the quaternary ammonium salt of 1,2,4-trimethyl pyridine quaternary salt or 1,2,6- trimethyl pyridine quaternary salt (Scheme 1). In all cases investigated, we found that the formation reactions of trinucleus dimethine cyanine dyes with pyridine nucleus proceeded efficiently under catalysis of piperidine or NaOH, and the better and purer yields were obtained in ethanol for 3a-3d and in water for 3e-3f. For example, the yield of 3d could reach 86% in ethanol, and 65% in water.¹² The yield of 3f could reach 83% in water, but in ethanol 3f could hardly be obtained. Because in organic solvents furaldehyde reacted with quaternary salt so quickly that the reaction could not be controlled, and there would be serious side reactions. In the synthesis of dyes 3a-3f , the required reaction time of heterocyclic aromatic aldehydes with trimethylpyridinium iodides was furaldehyde (30 min) < 1-methylpyrrole-2-carboxaldehyde (20 h) < indole-3-carboxaldehyde (24 h), thereby the reaction activity of heterocyclic aromatic aldehydes was furaldehyde > 1-methylpyrrole-2-carboxaldehyde > indole-3-carboxaldehyde. From the structure it was also suggested that the electron-withdrawing ability of the group attached to aldehyde group was =C"O > =C"N > =C"C=, leading to the positive charge density of carbon in aldehyde group was furaldehyde > 1-methylpyrrole-2-carboxaldehyde > indole-3-carboxaldehyde. The larger the positive charge density of carbon in aldehyde group is, the higher the reaction activity of heterocyclic aromatic aldehyde with trimethylpyridinium iodides is.

Spectral properties of the dyes in different solvents

Figure 1 gives the absorption maxima (λ_max) of six trinucleus dimethine cyanine dyes in different solvents (their dielectric constant: CHCl₃ 4.9, EtOH 24.6, MeOH 32.6, dimethylformamide 38.3, H₂O 78.4). From Figure 1 it could be found that the λ_max of 3a, 3b, 3c and 3d was longer than the λ_max of 3e and 3f. The reason suggested here was that dyes 3a-3f were all D-π-A molecules, in dyes 3a-3d the electron donor was N of indole or pyrrole ring, and the electron donor was O of furan ring in dyes 3e-3f, and the electron acceptor of six dyes was all N⁺ of pyridinium. The stronger was electron-donating capability of electron donor, the longer was the λ_max of dyes under the same electron-withdrawing capability of electron acceptor. The electron-donating capability of N situated indole or pyrrole ring was stronger than that of O situated furan ring, so the λ_max of 3a-3d was longer than the λ_max of 3e-3f. It could be also found that with the increasing of solvent polarity the λ_max of the dyes decreased. The effect of the solvent polarity on the absorption maximum could be illustrated by interactions between the dye molecules and the solvents, as the interactions made the ground state of dye more stable by forming hydrogen bonds.^18,19

The absorption, excitation maxima (λ_ex), fluorescence maxima emission (λ_em) of the dyes are summarized in Table 1. The dyes exhibited fluorescence properties at room temperature. Their fluorescence maxima were located at 502-565 nm. Compared with the absorption maxima of the dyes, the emission spectra were shifted to the red by 69-140 nm (Stokes shift). The stokes shift of six dyes were all large, this might be attributed to an excited-state intramolecular charge transfer between the donor and acceptor in the dyes. Large stokes shift could help to reduce self-quenching and measurement error by excitation light and scattered light.²⁰ The fluorescence quantum yield of six dyes was in the region 0.0001-0.0781 in different solvents. From Table 1 it could be found that the order of fluorescence quantum yield was 3a, 3b > 3c, 3d. The possible reason was that the conjugated system of 3a, 3b was larger than that of 3c, 3d. We also found the order of fluorescence quantum yield was 3a > 3b and 3c > 3d. The cause lay in the fact that two D-π-A system in 3b and 3d was in opposite orientation, which made their conjugated system became small. It could be found that the fluorescence performance of 3e and 3f was complex, because oxygen of furan ring was of both electron-donating and electron-acceptor effect. And there was also influence of solvents on the fluorescence quantum yield of these dyes. Further investigation of the influence of solvents on the fluorescence quantum yield of the dyes is in progressing.

Spectral properties of the dyes in the presence of DNA

The spectral properties of the dyes in the presence of DNA are summarized in Table 2 and Table 3. The λ_max of DNA-dye solution was situated at 401-458 nm and showed a slight red shift relative to the corresponding maxima of free dyes in buffer. The molar extinction coefficients for dyes 3a-3d were increased in the presence of DNA, and were in the range from 3.2×10⁴ to 8.5×10⁴ L mol^-1 cm^-1. However, for dyes 3e and 3f the values of molar extinction coefficients were unchanged relative to free dyes, which were 3.8×10⁴ and 4.2×10⁴ L mol^-1 cm^-1, respectively.

The fluorescence emission maxima of DNA-dyes were located at 503-555 nm, and showed a slight blue shift relative to free dyes in solution. Stokes shift values for the DNA-dyes were in the range of 97-109 nm. Moreover, the fluorescence intensity of dyes 3a-3c was greatly increased in the presence of DNA. Compared with free dyes, the quantum yields of DNA-dyes were up to 9.5 times for dye 3a, up to 31.6 times for dye 3b (Figure 2) and up to 18.9 times for dye 3c. Specially, the quantum yields of DNA-dye 3a was the highest in six dyes. It was noteworthy that free dye 3d could not be detected significantly fluorescence in buffer, but DNA-dye 3d showed great fluorescence quantum yields. The fluorescence enhancement of trinucleus dimethine cyanine dyes bound to DNA was attributable to the fact that on photoexcitation a lack of free rotation around the internuclear bridge made isomerisation around the C-C bonds of the methine chain difficult; and subsequently nonradiative deactivation of the excited state was not possible, causing the dye to fluoresce.^22,23 Upon binding with DNA, 3a-3d maintained their high Stokes shift and showed a red shift, owing to a more efficient ICT in the excited state between the terminal heterocyclic aromatic and the pyridimium group. ^24,25

CONCLUSIONS

Six trinucleus dimethine cyanine dyes with pyridine nucleus were synthesized and isolated in 69-86% yield with piperidine or NaOH as catalyst.

The absorption maxima of the dyes were located at 397-487 nm in different solvents, and with the increase of solvents polarity the maximum absorption wavelength of these dyes had a blue-shift. The fluorescence maxima of the dyes in different solvents were basically located at 502-565 nm, and the fluorescence quantum yield of six dyes was in the region 0.0001-0.0781 in different solvents.

The absorption maxima of the dyes in the presence of DNA were situated at 401-458 nm and showed a slight red shift relative to free dyes. The fluorescence maxima of DNA-dyes were located at 503-555 nm, and showed a slight blue shift relative to free dyes. The fluorescent quantum yields of the DNA-dyes 3a-3c were up to 9.5-31.6 times higher than that of free dyes. Specially, free dye 3d emitted weak fluorescence in buffer, but DNA-dye 3d showed great fluorescence quantum yields. Therefore dyes 3a-3d could be proposed as fluorescent dyes for DNA detection.

Supplementary Information

Supplementary data are available free of charge at http://jbcs.sbq.org.br, as PDF file.

Acknowledgements

We appreciate the financial support for this research by a grant from the Natural Science Foundation of Shaanxi Province (No. SJ08B04), the Special Science Research Foundation of Education Committee (No. 08JK458), NWU Excellent Doctoral Dissertation Foundation (No. 08YYB04) and NWU Graduate Cross-discipline Funds (No. 09YJC20).

References

1. Karatsu, T.; Yanai, M.; Yagai, S.; Mizukami, J.; Urano, T.; Kitamura, A.; J. Photochem. Photobiol., A 2005, 170, 123.

2. Usami, T.; Asanuma, N.; Yamakawa, K.; JP Pat 265,076 2000.

3. Kovalska, V.; Volkova, K.; Losytskyy, M.; Tolmachev, O.; Balanda, A.; Yarmoluk, S.; Spectrochim. Acta, Part A 2006, 65, 271.

4. Deligeorgiev, T.; Gadjev, N.; Vasilev, A.; Maximova, V.; Timcheva, I.; Katerinopoulos, H.; Dyes Pigm. 2007, 75, 466.

5. Kovalska, V.; Kryvorotenko, D.; Balanda, A.; Losytskyy, M.; Tokar, V.; Yarmoluk, S.; Dyes Pigm. 2005, 67, 47.

6. Karlsson, H.; Bergqvist, M.;, Lincoln, P.; Westman, G.; Bioorg. Med. Chem. 2004, 12, 2369.

7. Timtcheva, I.; Maximova, V.; Deligeorgiev, T.; Zaneva, D.; Ivanov, I.; J. Photochem. Photobiol., A 2000, 130, 7.

8. Hilal, H.; Taylor, J.; Dyes Pigm. 2007, 75, 483.

9. Rosania, G. R.; Lee, J. W.; Ding, L. Yoon, H. S.; Chang, Y. T.; J. Am. Chem. Soc. 2003, 125, 1130.

10. Li, Q.; Kim, Y.; Namm, J.; Kulkarni, A.; Rosania, G.. R.; Ahn, Y. H.; Chang, Y. T.; Chem. Biol. 2006, 13, 615.

11. Vincenza, B.; Daniele, F.; Condorelli, C.; Giuseppe, M.; Bioorg. Med. Chem. 2002, 10, 2899.

12. Maria, F.; Cosimo, G. F.; Giuseppe, I.; Giuseppe, M.; Eur. J. Org. Chem. 2002, 145.

13. Wang, L. Y.; Zhang, X. G.; Shi, Y. P.; Zhang, Z. X.; Dyes Pigm. 2004, 62, 21.

14. Wang, L. Y.; Zhang, X. G.; Li, F. M.; Zhang, Z. X.; Synth. Commun. 2004, 34, 1.

15. Zhang, Z. X.; Zhang, Y. J.; Hao, J. X.; Li, C. E.; Sci. China, Ser. B: Chem. 1995, 25, 689.

16. Zhang, X .H.; Wang, L. Y.; Zhai, G.. H.; Wen, Z. Y.; Zhang, Z. X.; Bull. Korean Chem. Soc. 2007, 28, 12.

17. Huang, W.; Wang, L. Y.; Fu, Y. L.; Liu, J. Q.; Tao, Y. N.; Fan, F. L.; Zhai, G.. H.; Wen, Z. Y.; Bull. Korean Chem. Soc. 2009, 30, 3.

18. Pham, W.; Lai, W. F.; Weissleder, R.; Tung, C. H.; Bioconjugate Chem. 2003, 14, 1048.

19. Mishra, A.; Behera, R. K.; Behera, P. K.; Mishra, B. K.; Behera, G. B.; Chem. Rev. 2000, 100, 1973; Ibrahim, A. Z.; Al-Ansari, I.; Bull. Soc. Chim. Fr. 1997, 134, 593.

20. Zhang, Z.; Achilefu, S.; Org. Lett. 2004, 6, 2067.

21. Casey, K. G.; Quitevis, E. L.; J. Phys. Chem. 1988, 92, 6590.

22. Carlsson, C.; Larsson, A.; Jonsson, M.; Albinsson, B.; J. Phys. Chem. 1994, 98, 10313.

23. Anikovsky, M.Y.; Tatikolov, A. S.; Shvedove, L. A.; Kuzmin V. A.; Russ. Chem. Bull. 2001, 50, 1190.

24. Neto, B. A. D.; Lápis, A. A. M.; Mancilha, F. S.; Vasconcelos, I. B.; Thum, C.; Basso, L. A.; Santos, D. S.; Dupont, J.; Org. Lett. 2007, 20, 4001.

25. Neto, B. A. D.; Lápis, A. A. M.; Molecules 2009, 14, 1725.

Submitted: April 17, 2010

Published online: August 10, 2010

Supplementary Information

Figure S7 - Click to the enlarge

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Publication Dates

• Publication in this collection
  26 Jan 2011
• Date of issue
  Jan 2011

History

• Received
  17 Apr 2010
• Accepted
  10 Aug 2010