China
Africa
Explore chapters and articles related to this topic
Time scales
Published in Guo-ping Zhang, Georg Lefkidis, Mitsuko Murakami, Wolfgang Hübner, Tomas F. George, Introduction to Ultrafast Phenomena from Femtosecond Magnetism to high-harmonic Generation, 2020
Guo-ping Zhang, Georg Lefkidis, Mitsuko Murakami, Wolfgang Hübner, Tomas F. George
Retinal molecules in rhodopsin are fundamental to our vision. Rhodopsin consists of seven helices.c Rhodopsin is a light-sensitive pigment and appears in the retinas of humans and animal eyes and bacteria. The retinal molecule is situated around the seven helices. When light strikes rhodospin, photoisomerization occurs. In mammals, light excitation loosens up the double bond around C11 and C12 (see Fig. 1.6) and allows the molecular motif to rotate around the bond, so that 11-cis-retinal is transformed to an all-trans-retinal.d The top figure in Fig. 1.6 shows the resting structure which has a cis structure. This is energetically unfavorable, but docking proteins create a potential that favors this configuration. Under light excitation, 11-cis retinal transforms to all-trans retinal (see the bottom figure) within a few hundred femtoseconds. Such a process is extremely efficient. In bacteriorhodopsin [Gai et al. (1998)], the situation is similar, but there is a crucial difference: Photoisomerization occurs from all-trans retinal to 13-cis retinal around the C13-C14 bond.
The Biological Bases of Photoreception in the Process of Image 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
As described above, highly sensitive rod photoreceptors are responsible for low-light vision, whereas cone photoreceptors are less sensitive, but respond to a broad range of light wavelengths, and thereby they are responsible for daylight and color vision. Over 100 mutations identified in rhodopsin are involved in various ocular impairments, including congenital stationary night blindness and retinitis pigmentosa [Ortega et al. 2019; Athanasiou et al. 2018]. There is also great interest in finding novel ligand molecules that would improve the folding and stability of rhodopsin mutants [Ortega et al. 2019; Behnen et al. 2018]. Ortega et al. [2019] suggested that flavonoids could be utilized as lead compounds in the development of effective non-retinoid therapeutics for managing retinitis, i.e. pigmentosa-related retinopathies.
Electronics and Emerging Paradigms
Published in Sergey Edward Lyshevski, Molecular Electronics, Circuits, and Processing Platforms, 2018
Terminology Used and Justifications: The electrochemomechanically induced transitions, interactions, and events in the biomolecular hardware ultimately result in processing, memory storage, and other related tasks. Do we have an evidence and substantiation of the correctness and accuracy of this hypothesis? With a high degree of confidence, the answer is yes. We do not depart from the generally accepted biophysics, though the conventional neuroscience doctrine on the key role of action potential in the processing and memory, as well as neuron-as-a-device doctrine, are refined. Referencing to the light receptors (photon absorption) and production (photon emission), we recall that: A photon-absorbing retinal molecule is bonded to a membrane protein called opsin. The resulting biomolecule is rhodopsin. When rhodopsin absorbs light, the retinal changes shape due to a photochemical reaction. In addition, there are red, green, and blue cones in the retina, each with its own type of opsin associated with retina ensuring high selectivity to the wavelength absorption capabilities of photopsins.Bioluminescence is the production and emission of photons (light). This enzyme-catalyzed chemoluminescence reaction was reported.
Norethisterone exposure alters the transcriptome of Marine Medaka (Oryzias melastigma) larvae
Published in Chemistry and Ecology, 2021
Xueyou Li, Xiaona Lin, Yuebi Chen, Zhongduo Wang, Yusong Guo, Gyamfua Afriyie, Ning Zhang, Zhongdian Dong
The phototransduction pathway was also significantly affected by NET exposure in the experimental fish. Many fish species rely on visual perception to survive during development. Exposure to NET in aquatic systems may affect the visual function of developing fish [29]. Studies have confirmed that 21 days of exposure to environmentally relevant concentrations of synthetic progestins, such as drospirenone (DRS), medroxyprogesterone acetate (MPA), and dydrogesterone (DDG) can disrupt the phototransduction cascade in adult D. rerio [30,31]. G protein-coupled receptor kinase 7a (grk7a) and G protein-coupled receptor kinase 1a (grk1a) are the retinal-specific members of the G protein-coupled receptor kinase (GRK) family. They participate in the light response process through the phosphorylation of rhodopsin in rods and cones [32]. The recovery of the light response was delayed, and time contrast sensitivity was reduced in D. rerio with grk7a knockout [33]. In this study, exposure to 10 ng/L NET for 24 h significantly down-regulated several genes related to vision in the phototransduction pathway (such as pde6ga, guca1c, saga, and grk1a) (Table S3) in marine medaka larvae, which may affect eye development. This could subsequently hinder feeding, prey avoidance, and swimming, as well as affecting the growth of larvae.
Simulative structure and binding sites of lyral with olfactory receptor 10J5 using computational prediction methods
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Pu Wang, Rui Zhang, Shunbang Yu, Charles Lee, He Wang
The 3D structural model of the bovine rhodopsin with its ligand was downloaded from RCSB Protein Data Bank (RCSB PDB) website (www.rcsb.org) (Berman et al. 2000). The initial coordinate of OR10J5 was generated by MODELER (Šali and Blundell 1993). Subsequently, the overly folded structures were removed and the models were eliminated, which exhibited excessive hydrophobic residues in the EL. Further, the Protein Data Bank file illustrating the 3D structure of bovine rhodopsin had the waters removed which is essential for ligand docking simulation. The models were then assessed to determine conformational energy. Restrained minimization was then performed by setting converge heavy atoms to RMSD (0.30Å) via the Protein Preparation Wizard (Sastry et al. 2013) of Schrödinger Suite 2018. In addition, “force field (OPLS3)” and “create zero-order bonds to metals” settings were also selected. It is noteworthy that OPLS3 provides a high accuracy specific to assessing small-molecule conformational propensities (Harder et al. 2015). Consequently, the minimal energy conformation was selected as the preferred model. A Ramachandran plot of our preferred model is presented in Figure 2. This structure was considered to be sufficiently stable according to the results of the Ramachandran plot.