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Strong pH-Dependent Near-Infrared Fluorescence in a Microbial Rhodopsin Reconstituted with a Red-Shifting Retinal Analogue
摘要： Near-infrared (NIR)-driven rhodopsins are of great interest in optogenetics and other optobiotechnological developments such as artificial photosynthesis and deep-tissue voltage imaging. Here we report the proton pump proteorhodopsin (PR) containing a NIR-active retinal analogue (PR:MMAR) exhibits intense NIR fluorescence at a quantum yield of 3.3%. This is 130 times higher than native PR (Lenz, M. O.; et al. Biophys J. 2006, 91, 255?262) and 3?8 times higher than the QuasAr and PROPS voltage sensors (Kralj, J.; et al. Science 2011, 333, 345?348; Hochbaum, D. R.; et al. Nat. Methods 2014, 11, 825?833). The NIR fluorescence strongly depends on the pH in the range of 6?8.5, suggesting potential application of MMAR-binding proteins as ultrasensitive NIR-driven pH and/or voltage sensors. Femtosecond transient absorption spectroscopy showed that upon near-IR excitation, PR:MMAR features an unusually long fluorescence lifetime of 310 ps and the absence of isomerized photoproducts, consistent with the high fluorescence quantum yield. Stimulated Raman analysis indicates that the NIR-absorbing species develops upon protonation of a conserved aspartate, which promotes charge delocalization and bond length leveling due to an additional methylamino group in MMAR, in essence providing a secondary protonated Schiff base. This results in much smaller bond length alteration along the conjugated backbone, thereby conferring significant single-bond character to the C13C14 bond and structural deformation of the chromophore, which interferes with photoinduced isomerization and extends the lifetime for fluorescence. Hence, our studies allow for a molecular understanding of the relation between absorption/emission wavelength, isomerization, and fluorescence in PR:MMAR. As acidification enhances the resonance state, this explains the strong pH dependence of the NIR emission.
关键词： stimulated Raman analysis,fluorescence,voltage sensor,rhodopsins,optogenetics,artificial photosynthesis,proteorhodopsin,femtosecond transient absorption spectroscopy,pH sensor,Near-infrared,voltage imaging
更新于2025-09-23 15:21:01
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Physicala??Chemical Properties of Self-Assembled Structures in Solution of Zinc Phthalocyanine and Bis-3-pentyl-PTCDI Derivative
摘要： For the first time, in this work, we succeed in synthesizing in solution a novel supramolecular self-assembled zinc phthalocyanine (ZnPc) and N,N′-bis(3-pentyl)-perylene-3,4,9,10-bis(dicarboximide) (bis-3-pentyl-PTCDI) system with improved light absorption and phosphorescence lifetime of the charge separated states up to 2.5 ms. Moreover, the structural and optical properties of undoped and doped with iodine ZnPc thin films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman analysis, and UV?vis spectroscopy. Analysis of ZnPc:I2:bis-3-pentyl-PTCDI blend in a 2:1 ratio shows that sandwich complexes between them result in improved bulk properties as compared to those of the single-component systems.
关键词： light absorption,Fourier transform infrared spectroscopy,UV?vis spectroscopy,bis-3-pentyl-PTCDI,X-ray diffraction,supramolecular self-assembly,X-ray photoelectron spectroscopy,zinc phthalocyanine,phosphorescence lifetime,Raman analysis
更新于2025-09-23 15:19:57
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Synthesis, structural and photoluminescence studies on perovskites –A novel phosphor for WLEDs
摘要： (SrTiO3)1-x – (YInO3)x: Eu3+ perovskite type red phosphors with multiband emission is prepared by solid state reaction. The enhancement of R-point vibrations in the crystal, observed by Raman analysis indicates the increased asymmetry in local structure due to YInO3 incorporation. The augmentation of photo luminescence observed by increasing concentration of YInO3 evidences the host sensitized energy transfer in the system.
关键词： Raman analysis,perovskite,luminescence,red emission,titanate
更新于2025-09-16 10:30:52
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The effect of CdO content on the crystal structure, surface morphology, optical properties and photocatalytic efficiency of p-NiO/n-CdO nanocomposite
摘要： Pure NiO nanoparticles and NiO-CdO nanocomposite were prepared with different content of CdO by simple chemical precipitation method at 800 °C for 3 h. Crystal structure, surface morphology, elemental composition and function groups present in the prepared samples were characterized by XRD, SEM, EDX, Raman and FTIR analysis, respectively. From XRD, preparation of pure NiO and formation of nanocomposite samples confirmed by the presence of characteristic diffraction peaks of cubic phase structure of NiO and CdO. The particle size increases from 26 to 34 nm with the increase of CdO content in the prepared samples. SEM images show the spherical shape of NiO and plate like shape of nanocomposite samples. The EDX analysis revealed that the absence of any impurity peaks indicates the high quality of prepared samples. Raman and FTIR spectra show the fundamental peaks of NiO and CdO in the samples. The best photodegradation efficiency of methyl orange dye i.e. 60% was achieved as a result of the decrease in the energy band gap from 3.42 to 2.92 eV at the optimum content of CdO (0.12 wt.%).
关键词： Photocatalytic efficiency,Raman analysis,Nanocomposite,Optical properties,XRD
更新于2025-09-10 09:29:36