Large two-photon absorptivity of hemoglobin in the infrared range of 780–880nm

Department of Physics, University of California at San Diego, La Jolla, California 92093, USA.
The Journal of Chemical Physics (Impact Factor: 2.95). 02/2007; 126(2):025102. DOI: 10.1063/1.2404678
Source: PubMed

ABSTRACT Porphyrin molecules have a highly conjugated cyclic structure and are theorized to have unusually large two-photon absorptivities (sigmaTPA), i.e., sigmaTPA approximately 10(2) GM. The authors tested this claim. Ultrafast two-photon absorption (TPA) spectroscopy was performed on solutions of hemoglobin, which contains a naturally occurring metaloporphyrin. They used a pump-probe technique to directly detect the change in transmission induced by TPA over the wavelength range of lambda0=780-880 nm. As controls, they measured the TPA of the dyes rhodamine 6G and B; their measurements both verify and extend previously reported values. In new results, hemoglobin was found to have a peak two-photon absorptivity of sigmaTPA approximately 150 GM at lambda0=825 nm, near a resonance of the Soret band. This value supports theoretical expectations. They also found a significant difference in the TPA of carboxyhemoglobin versus oxyhemoglobin, e.g., sigmaTPA=61 GM versus sigmaTPA=18 GM, respectively, at lambda0=850 nm, which shows that the ligand affects the electronic states involved in TPA.

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    • "4. Tissue staining may also appear faint owing to blood at the tissue surface. Hemoglobin has a large two-photon absorption cross section and may interfere with fluorescence imaging (Clay et al. 2007). "
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    • "350 400 450 500 550 600 650 0 50 100 150 200 250 700 800 900 1000 1100 1200 1300 0 50 100 150 200 250 0 20 40 60 80 100 120 140 160 180 200 700 750 800 850 900 950 1000 1050 1100 0 20 40 60 80 100 120 140 160 180 200 σ 2 , GM Transition wavelength, nm Rhodamine 610 (B) Xu, 1996 Xu, 1996 Xu, 1996 Xu, 1996 Xu, 1996 Hermann, 1972 Clay, 2007 Li, 1982 Bradley, 1972 Catalano, 1981 Oulianov, 2001 Kauert, 2006 Kaatz, 1999 Sperber, 1986 Karotki, 2006 Sailaja, 2007 "
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