Katilius Evaldas, Woodbury Neal W
Arizona State University, Biodesign Institute, Department of Chemistry and Biochemistry and the Center for BioOptical Nanotechnology, Tempe, Arizona 85287-5201, USA.
J Biomed Opt. 2006 Jul-Aug;11(4):044004. doi: 10.1117/1.2337521.
Multiphoton excitation was used to investigate properties of the fluorescent DNA base analogs, 2-aminopurine (2AP) and 6-methylisoxanthopterin (6MI). 2-aminopurine, a fluorescent analog of adenine, was excited by three-photon absorption. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2AP for DNA-protein interaction studies. However, high excitation power and long integration times needed to acquire high signal-to-noise fluorescence correlation curves render three-photon excitation FCS of 2AP not very useful for studying DNA base dynamics. The fluorescence properties of 6-methylisoxanthopterin, a guanine analog, were investigated using two-photon excitation. The two-photon absorption cross-section of 6MI was estimated to be about 2.5 x 10(-50) cm(4)s (2.5 GM units) at 700 nm. The two-photon excitation spectrum was measured in the spectral region from 700 to 780 nm; in this region the shape of the two-photon excitation spectrum is very similar to the shape of single-photon excitation spectrum in the near-UV spectral region. Two-photon excitation of 6MI is suitable for fluorescence correlation measurements. Such measurements can be used to study DNA base dynamics and DNA-protein interactions over a broad range of time scales.
采用多光子激发来研究荧光DNA碱基类似物2-氨基嘌呤（2AP）和6-甲基异黄蝶呤（6MI）的性质。2-氨基嘌呤是腺嘌呤的荧光类似物，通过三光子吸收进行激发。尝试通过荧光相关测量来评估利用2AP的三光子激发进行DNA-蛋白质相互作用研究的可行性。然而，获取高信噪比荧光相关曲线所需的高激发功率和长积分时间使得2AP的三光子激发荧光相关光谱法在研究DNA碱基动力学方面不太实用。利用双光子激发研究了鸟嘌呤类似物6-甲基异黄蝶呤的荧光性质。在700nm处，6MI的双光子吸收截面估计约为2.5×10(-50) cm(4)s（2.5 GM单位）。在700至780nm光谱区域测量了双光子激发光谱；在此区域，双光子激发光谱的形状与近紫外光谱区域的单光子激发光谱形状非常相似。6MI的双光子激发适用于荧光相关测量。此类测量可用于在广泛的时间尺度上研究DNA碱基动力学和DNA-蛋白质相互作用。
