Fluorescence Anisotropy of Riboflavin vis-à-vis Protochlorophyllide in Lemon Juice

Area of Science:

• Photochemistry
• Biophysics
• Analytical Chemistry

Background:

• Fluorescence spectroscopy is a powerful tool for analyzing molecular properties.
• Natural pigments like riboflavin and chlorophyll precursors exhibit unique spectral characteristics.
• Understanding molecular mobility in biological fluids is crucial for biochemical studies.

Purpose of the Study:

• To investigate the fluorescence properties of lemon juice using a violet laser.
• To determine and compare the fluorescence anisotropy of riboflavin and protochlorophyllide in lemon juice.
• To infer differences in rotational mobility between these two molecules based on anisotropy values.

Main Methods:

• Excitation of lemon juice steady-state fluorescence using a 405 nm violet laser.
• Measurement of emission spectra with prominent peaks at 520 nm (riboflavin) and 670 nm (protochlorophyllide).
• Polarized fluorescence spectroscopy using an analyzer in parallel and perpendicular orientations to measure fluorescence anisotropy.

Main Results:

• Distinct fluorescence emission peaks were observed at 520 nm and 670 nm.
• Fluorescence anisotropy at 520 nm (riboflavin) was approximately twice the value at 670 nm (protochlorophyllide).
• Calculated anisotropies indicate significantly restricted rotational mobility for riboflavin compared to protochlorophyllide.

Conclusions:

• Riboflavin exhibits considerably less rotational mobility than protochlorophyllide in the acidic environment of lemon juice.
• Despite its larger and more complex structure, protochlorophyllide demonstrates greater rotational freedom.
• Fluorescence anisotropy measurements provide insights into the microenvironment and molecular dynamics of natural pigments.