Bathoiodopsin, a primary intermediate of iodopsin at physiological temperature

Area of Science:

• Photochemistry
• Biophysics
• Molecular Biology

Background:

• Iodopsin is a chicken red-sensitive cone visual pigment.
• Understanding the primary photochemical reactions of visual pigments is crucial for vision science.

Purpose of the Study:

• To investigate the primary photochemical reaction of iodopsin at room temperature using picosecond laser photolysis.
• To characterize the intermediate products formed after light excitation of iodopsin.

Main Methods:

• Picosecond (ps) laser photolysis with a 21 ps green pulse.
• Spectrophotometry at room and low temperatures.

Main Results:

• Excitation of iodopsin resulted in the instantaneous formation of a bathochromic product, potentially bathoiodopsin.
• At room temperature, bathoiodopsin decayed to all-trans-retinal and R-photopsin through intermediates.
• Room temperature bathoiodopsin had an absorption maximum at 625 nm and a lower extinction coefficient compared to low-temperature measurements.

Conclusions:

• The primary photochemical reaction of iodopsin at physiological temperatures differs from that observed at very low temperatures.
• The study provides insights into the early events of visual pigment photochemistry at biologically relevant temperatures.