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Yang M, Huang Y, Liu M, Yang MX, Wang Q, Zeng X, Xiao X, Tao Z. Specific Recognition of Hg
2+
and other Cations by a Hoechst33258@inverted Cucurbit[7]uril Fluorescence Probe Using Different pH Media. ChemistrySelect 2019. [DOI: 10.1002/slct.201901717] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Meixiang Yang
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou ProvinceGuizhou University Guiyang 550025 China
| | - Ying Huang
- The Engineering and Research Center for Southwest Bio-Pharmaceutical Resources of National Education Ministry of ChinaGuizhou University Guiyang 550025 China
| | - Ming Liu
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou ProvinceGuizhou University Guiyang 550025 China
| | - Mei X. Yang
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou ProvinceGuizhou University Guiyang 550025 China
| | - Qin Wang
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou ProvinceGuizhou University Guiyang 550025 China
| | - Xi Zeng
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou ProvinceGuizhou University Guiyang 550025 China
| | - Xin Xiao
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou ProvinceGuizhou University Guiyang 550025 China
| | - Zhu Tao
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou ProvinceGuizhou University Guiyang 550025 China
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2
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Nakamura A, Tsukiji S. Ratiometric fluorescence imaging of nuclear pH in living cells using Hoechst-tagged fluorescein. Bioorg Med Chem Lett 2017; 27:3127-3130. [DOI: 10.1016/j.bmcl.2017.05.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/10/2017] [Accepted: 05/11/2017] [Indexed: 01/03/2023]
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3
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Rakshit S, Goswami N, Pal SK. Slow solvent relaxation dynamics of nanometer sized reverse micellar systems through tryptophan metabolite, kynurenine. Photochem Photobiol 2011; 88:38-45. [PMID: 21958420 DOI: 10.1111/j.1751-1097.2011.01007.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Exploration of environmental dynamics using intrinsic biological probe tryptophan is very important; however, it suffers from various difficulties. An alternative probe, kynurenine (KN), has been found to be an efficient probe for the ultrafast dynamics in the biological environment (Goswami et al., [2010] J. Phys. Chem. B., 114, 15236-15243). In the present study, we have investigated the efficacy of KN for the exploration of relatively slower dynamics of biologically relevant environments. A detailed investigation involving UV-Vis, steady-state/time-resolved fluorescence spectroscopy and Förster resonance energy transfer (FRET) studies on KN compared to a well-known solvation probe, H33258, a DNA-minor groove binder in a model nonionic reverse micelle reveals that ultrafast internal conversion associated with the hydrogen-bonding dynamics masks KN to become a dynamical reporter of the immediate environments of the probe.
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Affiliation(s)
- Surajit Rakshit
- Department of Chemical, Biological & Macromolecular Sciences, S N Bose National Centre for Basic Sciences, Salt Lake, Kolkata, India
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4
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Kalies S, Kuetemeyer K, Heisterkamp A. Mechanisms of high-order photobleaching and its relationship to intracellular ablation. BIOMEDICAL OPTICS EXPRESS 2011; 2:805-816. [PMID: 21483605 PMCID: PMC3072123 DOI: 10.1364/boe.2.000816] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 02/18/2011] [Accepted: 02/20/2011] [Indexed: 05/30/2023]
Abstract
In two-photon laser-scanning microscopy using femtosecond laser pulses, the dependence of the photobleaching rate on excitation power may have a quadratic, cubic or even biquadratic order. To date, there are still many open questions concerning this so-called high-order photobleaching. We studied the photobleaching kinetics of an intrinsic (enhanced Green Fluorescent Protein (eGFP)) and an extrinsic (Hoechst 33342) fluorophore in a cellular environment in two-photon microscopy. Furthermore, we examined the correlation between bleaching and the formation of reactive oxygen species. We observed bleaching-orders of three and four for eGFP and two and three for Hoechst increasing step-wise at a certain wavelength. An increase of reactive oxygen species correlating with the bleaching over time was recognized. Comparing our results to the mechanisms involved in intracellular ablation with respect to the amount of interacting photons and involved energetic states, we found that a low-density plasma is formed in both cases with a smooth transition in between. Photobleaching, however, is mediated by sequential-absorption and multiphoton-ionization, while ablation is dominated by the latter and cascade-ionization processes.
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Affiliation(s)
- S. Kalies
- Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany
| | - K. Kuetemeyer
- Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany
| | - A. Heisterkamp
- Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany
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5
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Kalies S, Kuetemeyer K, Heisterkamp A. Mechanisms of high-order photobleaching and its relationship to intracellular ablation. BIOMEDICAL OPTICS EXPRESS 2011; 2:805-816. [PMID: 21483605 DOI: 10.1364/boe.2.000805] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 02/18/2011] [Accepted: 02/20/2011] [Indexed: 05/27/2023]
Abstract
In two-photon laser-scanning microscopy using femtosecond laser pulses, the dependence of the photobleaching rate on excitation power may have a quadratic, cubic or even biquadratic order. To date, there are still many open questions concerning this so-called high-order photobleaching. We studied the photobleaching kinetics of an intrinsic (enhanced Green Fluorescent Protein (eGFP)) and an extrinsic (Hoechst 33342) fluorophore in a cellular environment in two-photon microscopy. Furthermore, we examined the correlation between bleaching and the formation of reactive oxygen species. We observed bleaching-orders of three and four for eGFP and two and three for Hoechst increasing step-wise at a certain wavelength. An increase of reactive oxygen species correlating with the bleaching over time was recognized. Comparing our results to the mechanisms involved in intracellular ablation with respect to the amount of interacting photons and involved energetic states, we found that a low-density plasma is formed in both cases with a smooth transition in between. Photobleaching, however, is mediated by sequential-absorption and multiphoton-ionization, while ablation is dominated by the latter and cascade-ionization processes.
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Barooah N, Mohanty J, Pal H, Bhasikuttan AC. Supramolecular assembly of hoechst-33258 with cucurbit[7]uril macrocycle. Phys Chem Chem Phys 2011; 13:13117-26. [DOI: 10.1039/c1cp20493a] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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7
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Barooah N, Mohanty J, Pal H, Sarkar SK, Mukherjee T, Bhasikuttan AC. pH and temperature dependent relaxation dynamics of Hoechst-33258: a time resolved fluorescence study. Photochem Photobiol Sci 2011; 10:35-41. [DOI: 10.1039/c0pp00215a] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Furse KE, Corcelli SA. The Dynamics of Water at DNA Interfaces: Computational Studies of Hoechst 33258 Bound to DNA. J Am Chem Soc 2008; 130:13103-9. [DOI: 10.1021/ja803728g] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kristina E. Furse
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
| | - Steven A. Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
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9
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Sando S, Narita A, Hayami M, Aoyama Y. Tuning the Hoechst Dye into Color-changing Fluorescent pH Indicator in an Acidic Range. CHEM LETT 2008. [DOI: 10.1246/cl.2008.246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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10
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Furse KE, Lindquist BA, Corcelli SA. Solvation Dynamics of Hoechst 33258 in Water: An Equilibrium and Nonequilibrium Molecular Dynamics Study. J Phys Chem B 2008; 112:3231-9. [DOI: 10.1021/jp711100f] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Guan Y, Shi R, Li X, Zhao M, Li Y. Multiple Binding Modes for Dicationic Hoechst 33258 to DNA. J Phys Chem B 2007; 111:7336-44. [PMID: 17530793 DOI: 10.1021/jp066344e] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The binding of dicationic Hoechst 33258 (ligand) to DNA was characterized by means of the fluorescence spectra, fluorescence intensity titration, time-resolved fluorescence decay, light scattering, circular dichroism, and fluorescence thermal denaturation measurements, and two binding modes were distinguished by the experimental results. Type 1 binding has the stoichiometry of one ligand to more than 12 base pairs, and it is defined as quasi-minor groove binding which has the typical prolonged fluorescence lifetime of about 4.4 ns. In type 1 binding, planar conformation of the ligand is favorable. Type 2 binding with phosphate to ligand ratio (P/L) < 2.5 has the stoichiometry of one ligand to two phosphates. It is defined as a highly dense and orderly stacked binding with DNA backbone as the template. Electrostatic interactions between doubly protonated ligands and negatively charged DNA backbone play a predominant role in the type 2 binding mode. The characteristics of this type of binding result in a twisted conformation of the ligand that has a fluorescence lifetime of less than 1 ns. The results also indicate that the binding is in a cooperative manner primarily by stacking of the aromatic rings of the neighboring ligands. Type 1 binding is only observed for double-stranded DNA (dsDNA) with affinity constant of 1.83 x 10(7) M-1. In the type 2 binding mode, the binding affinity constants are 4.9 x 10(6) and 4.3 x 10(6) M-1 for dsDNA and single-stranded DNA (ssDNA), respectively. The type 2 binding is base pair independent while the type 1 binding is base pair related. The experiments described in this paper revealed that the dication bindings are different from the monocation bindings reported by previous study. The dication binding leads to stronger aggregation at low ligand concentration and results in orderly arrangements of the ligands along DNA chains. Furthermore the dication binding is demonstrated to be beneficial for enhancing the DNA's stability.
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Affiliation(s)
- Yuan Guan
- The Key Laboratory of Bioorganic Chemistry & Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing, People's Republic of China
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12
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Görner H. Direct and Sensitized Photoprocesses of Bis-benzimidazole Dyes and the Effects of Surfactants and DNA¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2001)0730339daspob2.0.co2] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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13
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Cosa G, Focsaneanu KS, McLean JRN, McNamee JP, Scaiano JC. Photophysical Properties of Fluorescent DNA-dyes Bound to Single- and Double-stranded DNA in Aqueous Buffered Solution¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2001)0730585ppofdd2.0.co2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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14
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Banerjee D, Pal SK. Ultrafast charge transfer and solvation of DNA minor groove binder: Hoechst 33258 in restricted environments. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.10.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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15
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Choi YS, Cho TS, Kim JM, Han SW, Kim SK. Amine terminated G-6 PAMAM dendrimer and its interaction with DNA probed by Hoechst 33258. Biophys Chem 2006; 121:142-9. [PMID: 16458415 DOI: 10.1016/j.bpc.2006.01.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 01/12/2006] [Accepted: 01/13/2006] [Indexed: 11/20/2022]
Abstract
Fluorescence characteristics of Hoechst 33258 bound to G-6 dendrimer, to the DNA-G-6 dendrimer complex, and to DNA were compared with that in an aqueous solution. The spectral properties including fluorescence emission spectrum, accessibility of anionic quencher, as well as the fluorescence decay time of the Hoechst 33258 are different for all three conditions, indicating that the environments in these conditions are different. Close analysis of the fluorescence properties led us to suggest that Hoechst 33258 located at or near the contact area of the dendrimer and DNA in the DNA-G-6 complex. In the complex, in the absence of Hoechst 33258, the shape of the circular dichroism in the DNA absorption region remained, indicating that DNA is in B form in the complex. On the other hand, the magnitude of linear dichroism (LD) decreased upon DNA-G-6 dendrimer complex formation. The decrease in LD magnitude reflects the shortening of the DNA contour length, which is expected from the fact that a large part of linear DNA is required to wrap the surface of G-6 dendrimer.
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Affiliation(s)
- Young Shin Choi
- Department of Chemistry, Yeungnam University, Gyeongsan City, Gyeong-buk, 712-749, Republic of Korea
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Goracci L, Germani R, Savelli G, Bassani DM. Hoechst 33258 as a pH-Sensitive Probe to Study the Interaction of Amine Oxide Surfactants with DNA. Chembiochem 2004; 6:197-203. [PMID: 15549726 DOI: 10.1002/cbic.200400196] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The use of Hoechst 33258 (HO) as a fluorescent probe to characterize the interactions between DNA and pH-sensitive amphiphiles is discussed. In the case of amine oxide amphiphiles dodecyldimethylamine oxide (DDAO) and p-dodecyloxybenzyldimethylamine oxide (pDoAO), the decrease in fluorescence emission, which signals DNA-amphiphile association, is accompanied by a large hypsochromic shift in the emission maximum of the bound probe; this eventually reaches a value characteristic of HO in a neutral or slightly basic environment. These findings are compared to results obtained by using the more common ethidium bromide (EB) probe, which shows no such shift. Circular dichroism and fluorescence depolarization experiments indicate that fluorescence emission only occurs from the DNA-bound probe, and the observed shift in emission maximum when using HO as a fluorescent probe is due to a variation in the local pH in the vicinity of the probe.
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Affiliation(s)
- Laura Goracci
- CEMIN, Centro di Eccellenza per Materiali Innovativi Nanostrutturati, Dipartimento di Chimica, Università di Perugia via Elce di Sotto 8, 06123 Perugia, Italy
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Affiliation(s)
- Samir Kumar Pal
- Laboratory for Molecular Sciences, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, USA
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Pal SK, Zhao L, Zewail AH. Water at DNA surfaces: ultrafast dynamics in minor groove recognition. Proc Natl Acad Sci U S A 2003; 100:8113-8. [PMID: 12815094 PMCID: PMC166191 DOI: 10.1073/pnas.1433066100] [Citation(s) in RCA: 202] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Water molecules at the surface of DNA are critical to its equilibrium structure, DNA-protein function, and DNA-ligand recognition. Here we report direct probing of the dynamics of hydration, with femtosecond resolution, at the surface of a DNA dodecamer duplex whose native structure remains unperturbed on recognition in minor groove binding with the bisbenzimide drug (Hoechst 33258). By following the temporal evolution of fluorescence, we observed two well separated hydration times, 1.4 and 19 ps, whereas in bulk water the same drug is hydrated with time constants of 0.2 and 1.2 ps. For comparison, we also studied calf thymus DNA for which the hydration exhibits similar time scales to that of dodecamer DNA. However, the time-resolved polarization anisotropy is very different for the two types of DNA and clearly elucidates the rigidity in drug binding and difference in DNA rotational motions. These results demonstrate that hydration at the surface of the groove is a dynamical process with two general types of trajectories; the slowest of them (approximately 20 ps) are those describing dynamically ordered water. Because of their ultrafast time scale, the "ordered" water molecules are the most weakly bound and are accordingly involved in the entropic (hydration/dehydration) process of recognition.
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Alemán C, Adhikary A, Zanuy D, Casanovas J. On the protonation equilibrium for the benzimidazole derivative Hoechst 33258: an electronic molecular orbital study. J Biomol Struct Dyn 2002; 20:301-10. [PMID: 12354081 DOI: 10.1080/07391102.2002.10506845] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Hoechst 33258 and its deprotonated forms have been examined in the gas-phase and in solution using quantum mechanical methods. Ab initio calculations at the HF level have been used to investigate the more relevant geometrical trends of such species, while proton affinities and gas-phase basicities were derived from B3LYP and MP2 electronic energies. Solvation energies were calculated using a dielectric continuum model: MST. The Delta(p)K(a) values were estimated by combining the gas-phase basicities and the free energies of solvation. Comparison of these Delta(p)K(a) values with experimentally reported data have been used to highlight the advantages and limitations of this strategy.
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Affiliation(s)
- Carlos Alemán
- Departament d'Enginyeria Química, E.T.S. d'Enginyers Industrials de Barcelona, Universitat Politècnica de Catalunya, Diagonal 647, Barcelona E-08028, Spain.
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Cosa G, Focsaneanu KS, McLean JR, McNamee JP, Scaiano JC. Photophysical properties of fluorescent DNA-dyes bound to single- and double-stranded DNA in aqueous buffered solution. Photochem Photobiol 2001; 73:585-99. [PMID: 11421063 DOI: 10.1562/0031-8655(2001)073<0585:ppofdd>2.0.co;2] [Citation(s) in RCA: 243] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The absorption and fluorescence spectra, fluorescence quantum yields, lifetimes and time-resolved fluorescence spectra are reported for nine different fluorescent DNA-dyes. The work was initiated in search of a quantitative method to detect the ratio of single-to-double stranded DNA (ssDNA/dsDNA) in solution based on the photophysics of dye-DNA complexes; the result is a comprehensive study providing a vast amount of information for users of DNA strains. The dyes examined were the bisbenzimide or indole-derived stains (Hoechst 33342, Hoechst 33258 and 4',6-diamidino-2-phenylindole), phenanthridinium stains (ethidium bromide and propidium iodide) and cyanine dyes (PicoGreen, YOYO-1 iodide, SYBR Green I and SYBR Gold). All were evaluated under the same experimental conditions in terms of ionic strength, pH and dye-DNA ratio. Among the photophysical properties evaluated only fluorescence lifetimes for the cyanine stilbene dyes allowed a convenient differentiation between ssDNA and dsDNA. The bisbenzimide dyes showed multiexponential decays when bound to either form of DNA, making lifetime-based analysis cumbersome with inherent errors. These dyes also presented biexponential decay when free in aqueous buffered solutions at different pH. A mechanism for their deactivation is proposed based on two different conformers decaying with different kinetics. The phenanthridinium dyes showed monoexponential decays with ssDNA and dsDNA, but there was no discrimination between them. High dye-DNA ratios (e.g. 1:1) resulted in multiexponential decays for cyanine dyes, resulting from energy transfer or self-quenching deactivation. Shifts in both absorption and fluorescence maxima for both ssDNA and dsDNA DNA-cyanine dye complexes were small. Broadening of dye-ssDNA absorption and fluorescence bands for the cyanine dyes relative to dye-dsDNA bands was detected and attributed to higher degrees of rotational freedom in the former.
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Affiliation(s)
- G Cosa
- Department of Chemistry, University of Ottawa, 10 Marie-Curie, Ottawa, Ontario, Canada K1N 6N5
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Moon JH, Kim SK, Sehlstedt U, Rodger A, Nordén B. DNA structural features responsible for sequence-dependent binding geometries of Hoechst 33258. Biopolymers 1998. [DOI: 10.1002/(sici)1097-0282(199605)38:5<593::aid-bip5>3.0.co;2-n] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Moon JH, Kim SK, Sehlstedt U, Rodger A, Nordén B. DNA structural features responsible for sequence-dependent binding geometries of Hoechst 33258. Biopolymers 1996; 38:593-606. [PMID: 8722229 DOI: 10.1002/(sici)1097-0282(199605)38:5%3c593::aid-bip5%3e3.0.co;2-n] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The complexes of Hoechst 33258 with poly[d(A-T)2], poly[d(I-C)2], and poly[d(G-C)2], and poly[d(G-m5C)2] were studied using linear dichroism, CD, and fluorescence spectroscopies. The Hoechst-poly[d(I-C)2] complex, in which there is no guanine amino group protruding in the minor groove, exhibits spectroscopic properties that are very similar to those of the Hoechst-poly[d(A-T)2] complex. When bound to both of these polynucleotides, Hoechst exhibits an average orientation angle of near 45 degrees relative to the DNA helix axis for the long-axis polarized low-energy transition, a relatively strong positive induced CD, and a strong increase in fluorescence intensity--leading us to conclude that this molecule also binds in the minor groove of poly[d(I-C)2]. By contrast, when bound to poly[d(G-C)2] and poly[d(G-m5C)2], Hoechst shows a distinctively different behavior. The strongly negative reduced linear dichroism in the ligand absorption region is consistent with a model in which part of the Hoechst chromophore is intercalculated between DNA bases. From the low drug:base ratio onset of excitonic effects in the CD and fluorescence emission spectra, it is inferred that another part of the Hoechst molecule may sit in the major groove of poly[d(G-C)2] and poly[d(G-m5C)2] and preferentially stacks into dimers, though this tendency is strongly reduced for the latter polynucleotide. Based on these results, the importance of the interactions of Hoechst with the exocyclic amino group of guanine and the methyl group of cytosine in determining the binding modes are discussed.
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Affiliation(s)
- J H Moon
- Department of Chemistry, Yeungnam University, Kyoungbuk, Republic of Korea
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