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2PE cross sections of intrinsic chromophores -- with their respective fluorescence spectra |
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| We have identified and investigated the nonlinear
photophysical properties of a basis set of tissue chromophores, all of which
are ultimately derived from the aromatic amino acids, Trp, Tyr and Phe,
with absorptions at 280nm, 280nm and 260nm respectively (3PE
cross sections). Longer wavelength (blue, green and yellow) autofluorescence
primarily originates from vitamin derivatives, with retinol and riboflavin
being classic examples. The chromophore responsible for NAD(P)H fluorescence
is the nicotinamide ring derived from niacin. The pyridolamine crosslinks
that provide structural stability to elastin and some collagens are based
on pyridoxine (vitamin B6). The figure to the right shows measured two photon action cross sections of several fluorescent vitamin derivatives (a) and their respective emission spectra (b). This information serves only as a rough guide to fluorescent tissue constituents since excitation and emission properties of fluorophores can be extremely sensitive to the tissue environment. |
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