Microbial rhodopsins are light-activated proteins that contain seven transmembrane alpha-helices. Spectral tuning in microbial rhodopsins is a useful optogenetic tool. In this study, we report a new site that controls spectral tuning. In the proteorhodopsins ISR34 and ISR36, a single amino-acid substitution at Cys189 caused an absorption maximum shift of 44 nm, indicating spectral tuning at a specific site. Comparison of single amino acid substitutions was conducted using photochemical and photobiological approaches. The maximum absorption for red-shift was measured for mutations at positions 189 and 105 in ISR34, both residues being equally important. Structural changes resulting from amino acid substitutions are related to pK values, pumping activity and spectral tuning.
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http://dx.doi.org/10.1002/1873-3468.14297 | DOI Listing |
Biomimetics (Basel)
November 2024
Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, SK S7N 5C9, Canada.
Herein, we report a study that provides new insight on the knowledge gaps that relate to the role of biopolymer structure and adsorption properties for chitosan adsorbents that are cross-linked with glutaraldehyde. The systematic modification of chitosan cross-linked with glutaraldehyde (CG) and its quaternized forms (QCG) was studied in relation to the reaction conditions: mole ratios of reactants and pH conditions. Complementary adsorbent characterization employed C NMR/FTIR spectroscopy, TGA and DSC, point-zero-charge (PZC), solvent swelling, and sorption studies using selected dye probes.
View Article and Find Full Text PDFJ Phys Chem B
December 2024
Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via A. Moro 2, Siena 53100, Italy.
The functional units of natural photosynthetic systems control the process of converting sunlight into chemical energy. In this article, we explore a series of chemically and structurally modified bacteriochlorophyll and chlorophyll pigments through computational chemistry to evaluate their electronic spectroscopy properties. More specifically, we use multiconfigurational and time-dependent density functional theory methods, along with molecular dynamics simulations, to compute the models' energetics both in an implicit and explicit solvent environment.
View Article and Find Full Text PDFCascaded Raman fiber lasers (CRFLs) with wavelength-independent feedback can provide power at any wavelength in near-IR regions. However, broad feedback leads to a broad output spectrum, decreasing spectral power density at a desired wavelength. The output characteristics of CRFLs can be controlled by controlling the feedback.
View Article and Find Full Text PDFData Brief
December 2024
Purdue University, 610 Purdue Mall, West Lafayette, IN 47907, United States.
Cone and spectral opponency are fundamental to colour processing in many species and are well studied in primates. The data required to make interspecific comparisons of the neural mechanisms associated with colour processing is spread across a broad body of literature reaching back to the 1950's across four retinal cell types and multiple brain regions. We aimed to produce a comprehensive dataset of all known cone opponent cells in non-primate vertebrates in image forming visual pathways.
View Article and Find Full Text PDFScience
December 2024
Center for Complex Particle Systems (COMPASS), University of Michigan, Ann Arbor, MI, USA.
Planck's law ignores but does not prohibit black-body radiation (BBR) from being circularly polarized. BBR from nanostructured filaments with twisted geometry from nanocarbon or metal has strong ellipticity from 500 to 3000 nanometers. The submicrometer-scale chirality of these filaments satisfies the dimensionality requirements imposed by fluctuation-dissipation theorem and requires symmetry breaking in absorptivity and emissivity according to Kirchhoff's law.
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