The fluorescence quenching of naphthalene (2)and 1, 3-di(α-naphthyl)propane (1) by RNA and bases in methanol-water (v:v=1:1) binary solvents in the presence or absence of cyclodex- trin (CD) has been investigated. Th...The fluorescence quenching of naphthalene (2)and 1, 3-di(α-naphthyl)propane (1) by RNA and bases in methanol-water (v:v=1:1) binary solvents in the presence or absence of cyclodex- trin (CD) has been investigated. The results show that both the monomer and excimer fluorescence of 1 can be quenched by these quenchers. The quenching and rates depend on the quencher and tem- perature. It is shown that there is a critical temperature (Tc) for each quencher. Below Tc, the excimer fluorescence spectra show vibrational structures and the Stern-Volmer plots are straight lines (for ura- cil and cytosine); while above the Tc, the vibrational structures disappear and the Stern-Volmer plots deviate from linearity and curve upward. The former is a static process; while the latter is a mixture of both static and dynamic processes. The addition of α-CD has no effect on the fine structure, whereas β-CD prevents the appearance of this structure efficiently. The quenching rates both for the monomer and excimer of 1 by bases except cytosine in the presence of β-CD at ambient temperature are not changed; the quenching of fluorescence of 1 by RNA in the presence of β-CD, however, is hindered. Time-resolved fluorescence study shows that the excimer fine structures appear from the zero time. The intensity of fine structures depend on the fraction of water (φ) in binary solvents, and it is independent of the pH value of the solvents. It is suggested that bases and RNA induced aggregates (perhaps microcrystal) are formed, in which the motion of molecules 1 is limited.展开更多
The UV absorption and fluorescence spectra of 1,3-di (α-naphthyl) propane (1), di (α- naphthylmethyl) ether (2), and α-methylnaphthalene (3) in aqueous methanol, ethanol, and DMSO were recorded as a function of Φ ...The UV absorption and fluorescence spectra of 1,3-di (α-naphthyl) propane (1), di (α- naphthylmethyl) ether (2), and α-methylnaphthalene (3) in aqueous methanol, ethanol, and DMSO were recorded as a function of Φ value (fraction of water in binary solvents). The existence of two sta- tes, a metastable state (defined as m) and a stable stationary state (defined as s), of molecules 1 as well as 2 in the above cosolvents at high Φ was shown by the contrary fluorescence excimer to monomer intensity (Ie/Im)vs. Φ relationships of the samples prepared with different processes. On the basis of the Φ value, substrate concentration, and the temperature dependence of the UV spectra. fluores- cence excitation and emission spectra, the chromophores of 1, 2 show the formation of aggregates in ground state at high Φ owing to the hydrophobic interaction. The m states consist of a supersaturated solution with aggregates, whereas the s states are suspended microcrystals or micro-oil-droplets with aggregates. The conformations of the molecules in the aggregates were discussed. Single crystal X-ray structure of 2 is reported.展开更多
基金This project was supported by the NationaI Natural Science Foundation of Chinathe National Education Commission Foundation of China.
文摘The fluorescence quenching of naphthalene (2)and 1, 3-di(α-naphthyl)propane (1) by RNA and bases in methanol-water (v:v=1:1) binary solvents in the presence or absence of cyclodex- trin (CD) has been investigated. The results show that both the monomer and excimer fluorescence of 1 can be quenched by these quenchers. The quenching and rates depend on the quencher and tem- perature. It is shown that there is a critical temperature (Tc) for each quencher. Below Tc, the excimer fluorescence spectra show vibrational structures and the Stern-Volmer plots are straight lines (for ura- cil and cytosine); while above the Tc, the vibrational structures disappear and the Stern-Volmer plots deviate from linearity and curve upward. The former is a static process; while the latter is a mixture of both static and dynamic processes. The addition of α-CD has no effect on the fine structure, whereas β-CD prevents the appearance of this structure efficiently. The quenching rates both for the monomer and excimer of 1 by bases except cytosine in the presence of β-CD at ambient temperature are not changed; the quenching of fluorescence of 1 by RNA in the presence of β-CD, however, is hindered. Time-resolved fluorescence study shows that the excimer fine structures appear from the zero time. The intensity of fine structures depend on the fraction of water (φ) in binary solvents, and it is independent of the pH value of the solvents. It is suggested that bases and RNA induced aggregates (perhaps microcrystal) are formed, in which the motion of molecules 1 is limited.
基金This work was supported by the National Natural Science Foundation of Chinathe National Education Commission Foundation of China.
文摘The UV absorption and fluorescence spectra of 1,3-di (α-naphthyl) propane (1), di (α- naphthylmethyl) ether (2), and α-methylnaphthalene (3) in aqueous methanol, ethanol, and DMSO were recorded as a function of Φ value (fraction of water in binary solvents). The existence of two sta- tes, a metastable state (defined as m) and a stable stationary state (defined as s), of molecules 1 as well as 2 in the above cosolvents at high Φ was shown by the contrary fluorescence excimer to monomer intensity (Ie/Im)vs. Φ relationships of the samples prepared with different processes. On the basis of the Φ value, substrate concentration, and the temperature dependence of the UV spectra. fluores- cence excitation and emission spectra, the chromophores of 1, 2 show the formation of aggregates in ground state at high Φ owing to the hydrophobic interaction. The m states consist of a supersaturated solution with aggregates, whereas the s states are suspended microcrystals or micro-oil-droplets with aggregates. The conformations of the molecules in the aggregates were discussed. Single crystal X-ray structure of 2 is reported.
