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The Biological Basis of Non-Image-Forming Vision
Published in Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe, Visual and Non-Visual Effects of Light, 2020
Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe
Chemically, melanopsin is a photopigment with a signature which is an unusual tyrosine residue in the counterion position for the Schiffbase linkage between the chromophore and the opsin protein [Provencio et al. 2000; Provencio et al. 2002]. In mammals, melanopsin expression is typical for ipRGCs. Melanopsin has peak absorbance at about 480 nm (blue light). It is isomerized on light absorption, converting 11-cis retinal to all-trans-retinal such as rod and cone photopigment. Like all photopigments, melanopsin is a prototypical G-protein-coupled receptor. TPR channels are nonselective cation channels, mediated by iPRGCs phototransduction. Cyclic nucleotide-gated ion channels (CNG channels) mediating phototransduction in rods and cones are not present in ipRGCs. Melanopsin physiological response is characterized by slow temporal kinetics and sustained signaling after light cessation.
Molecular Electronics: Device-Level and System-Level Considerations
Published in Sergey Edward Lyshevski, Molecular Electronics, Circuits, and Processing Platforms, 2018
The photochemical reaction, which should be referenced as the elec-trochemomechanical transitions, changes the shape of retinal, causing a conformational change in the opsin protein, which consists of 348 amino acids covalently linked together to form a single chain. The sensitivity of the photoreceptor in the eye is one photon. Thus, the energy of a single photon, which is E = 4 × 10−19 J, ensures the functionality of a molecular complex of 348 amino acids (~5000 atoms). We derived the excitation energy (signal energy) sufficient to ensure electrochemomechanically induced state transitions and interactions leading to processing in Mdevice. This provides a conclusive evidence that ~1 × 10−19 to 1 × 10−18 J of energy is required to guarantee state transitions for molecular aggregates in the biomolecular processing hardware.
Biological Effects: Why We Care About Laser Exposure
Published in Ken Barat, Laser Safety Management, 2017
Four kinds of light-sensitive receptors are found in the retina: rods and three types of cones. Each cone is tuned to absorb light from a portion of the spectrum of visible light, long-wavelength light (red), middle-wavelength light (green), and short-wavelength light (blue). Each type of receptor has its own special pigment for absorbing light. Each consists of a transmembrane protein called opsin, which is coupled to the prosthetic group retinal. Retinal is a derivative of vitamin A and is used by all four types of receptors.
Buildings, Lighting, and the Myopia Epidemic
Published in LEUKOS, 2023
Kevin W. Houser, Lisa Heschong, Richard Lang
The light sensing proteins of animals are called opsins (Shichida and Matsuyama 2009). The human eye contains at least six opsins, four of which are involved in our visual function through rod and cone photoreceptors. The remaining two are the so-called nonvisual opsins, melanopsin (OPN4) and neuropsin (OPN5). Preclinical studies have implicated all six opsins in the regulation of eye growth and optimization of focal length (Brown et al. 2022). Melanopsin has a peak light sensitivity around 480 nm, a sky-blue color. This opsin has a role in systemic circadian function, but also regulates eye growth and focal length through its retinal expression (Chakraborty et al. 2022). Neuropsin is of special interest for this discussion because it has a peak sensitivity at 380 nm, a violet wavelength that is at the edge of visual perception for most adults. As with melanopsin, preclinical studies of the violet light-OPN5 response have shown that it regulates eye growth and focal length (Jiang et al. 2021). More specifically, when OPN5 is stimulated by violet light, myopic elongation of the eye is suppressed (Jiang et al. 2021). These basic science findings are complemented by studies performed in humans: Torii et al. (2017a) found that myopic children with corrective lenses that transmitted violet light had less myopic progression than those with lenses that blocked violet light. Likewise, in myopic adults, Torii et al. (2017b) found that wearing lenses with more violet light transmittance was associated with less myopic progression. When combined, these studies have led to the hypothesis that the myopia boom (Dolgin 2015) may be caused by a modern lifestyle that results in insufficient exposure to the violet light that stimulates OPN5 (Jiang et al. 2021).
Mechanism of peripheral nerve modulation and recent applications
Published in International Journal of Optomechatronics, 2021
Heejae Shin, Minseok Kang, Sanghoon Lee
Optogenetic neuromodulation is a technology that has a higher selectiveness than electrical neuromodulation.[62] This technology modulates nerves using a photoreceptor protein called opsin, which can open and close ion channels in cells according to specific wavelengths of light. There are different types of opsin that respond to specific wavelengths of light.[63–65] One of these opsins, channelrhodopsin is expressed in the sodium ion channel. When the blue light is irradiated, sodium ion channels are opened, allowing Na+ ions to enter the cell and induce depolarization to cause excitation (Figure 3(a)). One of the types of Channelrhodopsin, channelrhodopsin-2 (ChR2) has the maximum relative activity at a wavelength of 470 nm.[66] Conversely, as opsins that cause inhibition rather than excitation, archaerhodopsin and halorhodopsin exist. ArchT1.0 and eArch3.0 of archaerhodopsin are expressed in the proton pump and when the green light is irradiated, the pump is activated to move the H+ ions from inside to the outside of the cell, inducing hyperpolarization, which in turn causes inhibition. For ArchT1.0 and eArch3.0, the relative activity is maximized at 566 nm wavelengths, respectively. NpHR, a type of halorhodopsin, is expressed in the chloride ion channel and when the yellow light is irradiated, the chloride ion channel opens, and Cl- ions enter the inside of the cell and cause hyperpolarization. For NpHR, the relative activity is maximum at 589 nm. However, in the case of these opsins, since the wavelength range of the activated light overlaps (Figure 3(b)), there is a limitation that several types of opsins cannot be used in target neurons. To compensate for this limitation, research is underway on opsins whose wavelength ranges do not overlap, such as C1V1 and red-active ChR.[67]