The two-photon excitation action cross section of Hc-Red fluorescent proteins (Hc-RFPs) is measured and found to be of the same order as that of enhanced green fluorescent proteins. With a 618 nm emission wavelength in the far-red region and with an excitation wavelength around 1200 nm, Hc-RPF-based two-photon fluorescence microscopy (2PFM) can offer deep penetration capability inside live samples and is ideal for in vivo gene expression study and biomolecular imaging in live objects. In vivo 2PFM of the developing heart deep inside a transgenic zebrafish embryo tagged by Hc-RFP is also successfully demonstrated.
© 2006 Optical Society of America
Medical Optics and Biotechnology
Original Manuscript: October 14, 2005
Revised Manuscript: January 7, 2006
Manuscript Accepted: January 9, 2006
Vol. 1, Iss. 5 Virtual Journal for Biomedical Optics
Tsung-Han Tsai, Cheng-Yung Lin, Huai-Jen Tsai, Szu-Yu Chen, Shih-Peng Tai, Kung-Hsuan Lin, and Chi-Kuang Sun, "Biomolecular imaging based on far-red fluorescent protein with a high two-photon excitation action cross section," Opt. Lett. 31, 930-932 (2006)