Polarized Two-Photon Absorption and Heterogeneous Fluorescence Dynamics in NAD(P)H

Area of Science:

• Biophysics
• Photochemistry
• Biochemistry

Background:

• Biological systems often display complex fluorescence decay due to multiple species or environments.
• Two-photon absorption (2PA) is a valuable technique for probing biological samples.
• Understanding molecular dynamics and structural heterogeneity is crucial in biological research.

Purpose of the Study:

• To develop a method for separately determining two-photon transition tensors in heterogeneous populations.
• To identify structural differences between the two fluorescent states of the redox cofactor NAD(P)H.
• To elucidate the molecular basis of fluorescence heterogeneity in NAD(P)H.

Main Methods:

• Combined polarized 2PA with time-resolved fluorescence intensity and anisotropy decay measurements.
• Utilized spectral analysis to resolve contributions from different molecular states.
• Applied theoretical analysis to interpret transition tensor properties.

Main Results:

• Successfully resolved the two-photon transition tensors for distinct components within a heterogeneous NAD(P)H population.
• Identified significant structural differences between the two fluorescent states of NAD(P)H.
• Demonstrated that these differences arise from alternate configurations of the nicotinamide ring.

Conclusions:

• The study provides a powerful approach to analyze heterogeneous photophysical processes in biological molecules.
• The findings support a model where NAD(P)H fluorescence heterogeneity is attributed to nicotinamide ring conformations.
• This work advances the understanding of cofactor dynamics and their implications in biological functions.