Related Experiment Video
Updated: Jun 19, 2026
08:33
Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings
Published on: February 26, 2016
THE CHEMISTRY OF DAYLIGHT VISION
1Laboratory of Biophysics, Columbia University, New York.
The Journal of General Physiology
|October 30, 2009
Summary
Researchers isolated and characterized iodopsin, a chicken eye pigment. This photosensitive pigment, similar to rhodopsin, has a bleaching maximum at 560 nm, differing slightly from human cone sensitivity.
Area of Science:
- Biochemistry
- Vision Science
- Retinal Physiology
Background:
- Previous studies reported photosensitive pigments in animals with numerous cone cells.
- Wald's discovery of iodopsin in chicken retinas was a key confirmed finding.
- Iodopsin is a red-sensitive pigment crucial for understanding color vision.
Purpose of the Study:
- To isolate and purify iodopsin from chicken retinas.
- To characterize the chemical and physical properties of iodopsin.
- To determine the bleaching effectiveness spectrum of iodopsin.
Main Methods:
- Partial purification using prehardened retinas and digitonin extraction.
- Minimizing rhodopsin contamination through specific extraction techniques.
- Spectrophotometric analysis to determine the bleaching effectiveness spectrum.
Main Results:
- Iodopsin exhibits chemical properties similar to rhodopsin but is less stable.
- A method was developed to partially purify iodopsin and reduce rhodopsin contamination.
- The bleaching effectiveness spectrum of iodopsin shows a maximum at 560 nm.
Conclusions:
- Iodopsin's properties were characterized, revealing its lability and spectral characteristics.
- The determined spectrum aligns with human cone sensitivity, with a noted difference in peak wavelength.
- Key findings from previous reports regarding pH and phosphate level changes during bleaching were not confirmed.
Related Concept Videos
01:22Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
01:16Energy Transfer in Chemical Reactions
Chemical reactions require sufficient energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy is the form of energy powering any type of matter in motion. Imagine a person building a brick wall. The energy it takes to lift and place one brick on top of another is the kinetic energy—the energy matter possesses because of its motion. Once the wall is in place, it stores potential energy. Potential...
01:24Color Vision
Color perception begins in the retina, the light-sensitive layer at the back of the eye. Two main theories explain how colors are seen: the trichromatic theory and the opponent-process theory. The trichromatic theory, proposed by Thomas Young in 1802 and extended by Hermann von Helmholtz in 1852, suggests that color vision is based on three types of cone receptors in the retina. These cones are sensitive to different but overlapping ranges of wavelengths corresponding to red, blue, and green.
01:35Light as Energy
The energy required to carry out photosynthesis is light— typically electromagnetic radiation from the sun. The range of all possible wavelengths is known as the electromagnetic spectrum.
Photons
A photon is a discrete electromagnetic particle or bundle of energy. Photons are characterized by their frequency, wavelength, and amplitude, similar to the properties of a wave. Waves with higher frequencies transmit more energy and have shorter wavelengths than longer wavelengths that transmit less...
Photons
A photon is a discrete electromagnetic particle or bundle of energy. Photons are characterized by their frequency, wavelength, and amplitude, similar to the properties of a wave. Waves with higher frequencies transmit more energy and have shorter wavelengths than longer wavelengths that transmit less...
01:20Anatomy of the Eyeball
The eye is a spherical, hollow structure composed of three tissue layers. The outer layer — the fibrous tunic, comprises the sclera — a white structure — and the cornea, which is transparent. The sclera encompasses some of the ocular surface, most of which is not visible. However, the 'white of the eye' is distinctively visible in humans compared to other species. The cornea, a clear covering at the front of the eye, enables light penetration. The eye's middle layer, the vascular tunic,...
01:11Channel Rhodopsins
Most organisms use photoreceptors to sense and respond to light. Examples of photoreceptors include bacteriorhodopsins and bacteriophytochromes in some bacteria, phytochromes in plants, and rhodopsins in the photoreceptor cells of the vertebral retina. The light-sensitive property of these receptors is because of the bound chromophores, such as bilin in the phytochromes and retinal in the rhodopsins.
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...