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The Emergence of Temporal Order within a Living Being
Published in Pier Luigi Gentili, Untangling Complex Systems, 2018
Magnitude amplification is the production of some output molecules far higher than the elementary particles of the stimulus; it trusts in chain reactions. For example, in vision, the absorption of one photon can be amplified almost 5,000-fold and becomes perceptible. The first step in human vision is the absorption of one photon by the chromophore of the photoreceptor protein rhodopsin, which is 11-cis retinal. The excited state of 11-cis retinal isomerizes to all-trans retinal (see Figure 7.22) in 200 fs and with a quantum yield of Φ = 0.67. The isomerization is so fast that is vibrationally coherent (Wang et al. 1994).
Medium Design for Cell Culture Processing
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
A group of compounds generally referred to as retinoids possess vitamin A activities. Their forms are retinol, retinal, retinoic acids, and ester. Their most important role is the vision function, with retinal serving as the photosensitive chromophore through a covalent link to the photoreceptor protein rhodopsin. In addition to operating as a vitamin, the retinoic acid derived from retinol plays a role in the regulation of transcriptional regulation in embryo development and in stem cell differentiation. Vitamin B is used to guide the differentiation process of specific lineages.
Coherent Optical Measurements in ND
Published in Thomas C. Weinacht, Brett J. Pearson, Time-Resolved Spectroscopy, 2018
Thomas C. Weinacht, Brett J. Pearson
We begin by considering a measurement of the primary stage of vision: isomerization of the 11-cis retinal chromophore to its all-trans form [2]. The retinal chromophore sits within the photoreceptor protein rhodopsin, which is located in the rods of the eye retina. Upon absorption of light, the retinal system experiences rotations of bond angles near the center of the molecule. This experiment uses ultrafast electronic transient absorption to track isomerization dynamics through a conical intersection between the ground and excited electronic states.
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]