Two-color two-photon excitation of indole

✍ Scribed by Ignacy Gryczynski; Henryk Malak; Joseph R. Lakowicz

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 150 KB
• Volume: 3
• Category: Article
• ISSN: 1075-4261
• DOI: 10.1002/(sici)1520-6343(1997)3:2<97::aid-bspy2>3.0.co;2-p

✦ Synopsis

We observed two-color two-photon (2C2P) excitation of indole upon simultaneous illumination at 380 and 760 nm with picosecond pulses from a cavity-dumped dye laser. The emission spectrum of indole with 2C2P excitation was the same as observed for one-photon excitation with an equivalent energy of 250 nm. Observation of the 2C2P signal required temporal and spatial overlap of the 380-and 760-nm pulses. Illumination at 380 nm alone resulted in a background emission due to one-color twophoton excitation at 380 nm. This background was rendered insignificant compared to the 2C2P signal by attenuation of the 380-nm beam and amplification of the 760-nm beam. The ability to control the intensity of each beam is a unique advantage of 2C2P excitation. The amplitude of the 2C2P signal depended on the angle between the polarization of each beam in a manner which suggests participation of both the 1 L a and 1 L b states of indole to the 2C2P transitions. 2C2P excitation can provide a new tool to investigate the photophysical properties of indole, tryptophan, and proteins. ᭧ 1997