查看更多>>摘要：Taking formamide (FA) as a model compound of protein, the water structure in the ternary mixtures of dimethyl sulfoxide (DMSO)-water-FA was studied by near-infrared (NIR) spectroscopy. The interaction of DMSO and water, and the effect of FA on the interaction, were analyzed with the help of chemometric methods. Continuous wavelet transform (CWT) was used to enhance the resolution of the spectra. A peak at 6437 cm-1 depicting the interaction of DMSO and water through hydrogen bonding (S=O.. .H-O) was observed in the transformed spectra. When FA exists in the mixture, the intensity of the peak decreases with the increase of formamide content, showing that FA may replace the water to form the hydrogen bond of S=O and H-N. In addition, temperature-dependent NIR spectroscopy was used to analyze the effect of the three components on the spectral variation with temperature. Analyzing the spectral data by alternating trilinear decomposition (ATLD) and multiple linear regression, two varying spectral fea-tures were obtained that are related to water and DMSO, but no spectral feature was found that signif-icantly varies with the content of FA. The result implies that DMSO is still the key component to prevent the water from icing, although FA may reduce slightly the anti-freezing effect. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Nanogaps are one of the most useful systems in nanooptics. The gap modes in a film coupled dielectric nanoparticle dimer system are influenced by both of the film and the electric and magnetic modes of the particles. In this work, strong confinement of gap modes of dielectric (Si) nanoparticle dimer on Au/Si film is investigated. The results show an abnormal electric field enhancement obtained between Si nanoparticle dimer on metal film, which is attributed to film coupled electric and magnetic dipole modes in dielectric nanoparticle dimer. The results are further analyzed with mode hybridization theory. Furthermore, the surface enhanced Raman spectroscopy (SERS) is performed to demonstrate these theoretical analyses. The film induced electromagnetic field redistribution in dielectric nanoparticle dimer not only extend the knowledge of dielectric gap modes but also has tremendous applications, e.g. light manipulating in subwavelength, light harvest, surface enhanced spectrum, etc. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Hydrogen sulfide (H2S), a recognized environmental pollutant, comes from a wide range of sources. For example, H2S will be produced in the process of plant protein corruption, the decomposition of domestic sewage and garbage, food processing (wine brewing), etc. and once the concentration is too high, it will cause significant damage of environment and human body. Besides H2S is an important gas signal molecule in vivo, which can be transferred through lipid membrane. Its existence level is closely related to many diseases. If we can "visually" trace the transmembrane transmission of hydrogen sulfide, it will be very helpful for the study of oxidative stress processes, cell protection, signal transduction and related diseases closely related to H2S. Although some probes can detect H2S in environment, cytoplasm and organelles, there are few reports on the release and internalization of H2S. In this work, we report a H2S fluorescence probe that can retain on the cell membrane, named PCM. The probe PCM can not only detect endogenous and exogenous H2S, but also distinguish them, this provides a general strategy for the construction of probes to detect other biomarkers. In addition, PCM has been successfully applied to the detection of endogenous and exogenous H2S in zebrafish, which has the potential to become a new chemical tool and provide help for the research of H2S-related diseases. (C) 2021 Elsevier B.V. All rights reserved.
Kumar, NaveenMurli, C.Varma, MeeraPoswal, H. K....
8页
查看更多>>摘要：Trans-urocanic acid (t-UCA) is an important epidermal UV protector predominantly found in human skin. Exposure of UV radiation triggers photoisomerization of t-UCA into its other conformer, cis-urocanic acid (cis-UCA), which has been shown to be a mediator of UV-induced immune-suppression leading to skin cancer. In this report, we present the investigation of molecular changes of t-UCA under high pressures by in-situ high pressure Raman spectroscopy. The study indicates onset of ring opening polymerization of t-UCA at pressure above 1.4 GPa. At pressures beyond 5 GPa, a well discernible characteristic vibrational mode (C=C stretch) accompanied by several other spectral features such as delta CO2- and delta N-H modes of cis-UCA point towards the isomerization of residual t-UCA monomers into cis-UCA. The content of cisUCA gradually increased with increase in pressure. On release to ambient conditions, the spectrum of the quenched sample showed Raman modes of polymer and cis-UCA indicating that the changes are irreversible. (C) 2021 Elsevier B.V. All rights reserved.
Uriza-Prias, D. M.Mendez-Blas, A.Rivas-Silva, J. F.
9页
查看更多>>摘要：The luminescent properties of tryptophan in solvents less polar than water, such as acetone, and non-polar ones, such as cyclohexane, are experimentally studied and compared with theoretical calculations using time-dependent density functional theory (TD-DFT) methods. Since tryptophan may present different configurations and charge distributions, the most stable conformer is analyzed for both solvents, including its neutral and zwitterionic forms. To perform the simulation two clusters are proposed with the Zpt conformer in acetone: (Trp)(iota) - (C3H6O)(17) and (Trp)(2) - (C3H6O)(34), and four clusters with the Nag(+) conformer in cyclohexane: (Trp)(iota)' (C6H12), (Trp)(2) (C6H12), (Trp)(3) (C6H12) and (Trp)(4) (C6H12), in order to conveniently emulate the concentration in each solvent by reducing the distance between adjacent tryptophan molecules as the concentration increases, since there is no control over the volume parameter. In each case, the UV-vis absorption is computed and compared with the experimental excitation spectra; the results show a good agreement. This calculation allows a more detailed analysis of the experimental results based on the properties of the molecular orbitals involved in electronic transitions. In the present work, a strong effect of the solvent acetone on tryptophan is observed; for this solvent, a charge transfer from the solute to solvent happens. This behavior does not occur with water (polar solvent) or cyclohexane (non-polar solvent). Finally, experimental spectroscopic data of Trp in cyclohexane are explained through the hydrogen bonds between amino acid molecules present in the fluorescent states. In this case, the theoretical and experimental results are compared and also show good agreement. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Biothiols play an important role in many physiological and pathological processes, especially in the occurrence of oxidative stress caused by abnormal cysteine (Cys) concentration. Therefore, it is particu-larly critical to develop a method that can specifically identify Cys to avoid interference from other bio-logical analytes. However, most Cys-specific fluorescent probes are difficult to distinguish between homocysteine (Hcy) and glutathione (GSH). In this work, to avoid the interference of Hcy and GSH, we developed a fluorescent probe triarylimidazole-naphthalimide-piperazine-sulfonyl benzoxadiazole (TNP-SBD-Cl) based on fluorescence resonance energy transfer (FRET) on platform of naphthalimide-sulfonyl benzoxadiazole (SBD), the main SBD 4-chlorine groups have mild reactivity to undergo substitution and rearrangement to distinguish Hcy and GSH. The TNP-SBD-Cl response to Cys would turn on FRET and generate a new yellow fluorescence with a large Stokes shift (157 nm), and with excellent selectivity and low detection limit (0.87 mu M). Moreover, TNP-SBD-Cl can be used to monitor Cys in living HeLa cells with low cytotoxicity, suggesting that it has markedly diagnostic significance in physiological and patho-logical processes. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Several experimental and theoretical studies have shown that 2D hybrid structures formed by boron, nitrogen and carbon atoms (h-BNCs) possess a highly tunable linear and non-linear optical responses. Recent advances towards the controlled synthesis of these unique structures have motivated an important number of experimental and theoretical work. In this work, the confinement on the optical response induced by boron-nitride (BN) strings in h-BNC 2D structures is investigated using time-dependent density functional theory (TDDFT) and electron density response properties. The number of surrounding BN strings (N-BN) necessary to "isolate" the optical modes of a carbon nanoisland (nanographene) from the remaining substrate has been characterized in two different nanoisland models: benzene and pyrene. It was found that for N-BN >= 3 the excitation wavelengths of the optically active modes remain constant and the changes in the transition densities, the ground to excited state density differences and their associated electron deformation orbitals are negligible and strongly confined within the carbon nanoisland. Using a water molecule as model system, Raman enhancement factors of 10 [6] for the water vibrational modes are obtained when these electromagnetic "hot spots" are activated by an external electromagnetic field. The high tunability of the optical absorption bands of nanographenes through changes in size and morphology makes h-BNCs be perfect materials to construct platforms for surface enhancement Raman spectroscopy (SERS) for a wide range of laser sources. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Fluorescent silicon nanoparticles (SiNPs) were synthesized by a one-step, simple, and green method with 3-Aminopropyltriethoxysilane (APTES) and ascorbic acid (AA) as reaction agents. Subsequently, the SiNPs and AgNPs nanocomplex (SiNPs@AgNPs) was constructed as the probe for hydrogen peroxide (H2O2) detection. The fluorescence of SiNPs was quenched due to the surface plasmonic-enhanced energy transfer between SiNPs and AgNPs. Meanwhile, the color tends to be yellow due to the existence of AgNPs. As the AgNPs were etched by H2O2, the fluorescence recovers and color fadings. Based on the well-designed structure, the "off-on" fluorescence sensing and "on-off" color sensing platforms for H2O2 were fabricated. The as-synthesized materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Fluorescence and UV-vis absorption spectra were used to evaluate the optical performance. The fabricated sensor exhibited a linear range of 1.0-100.0 mu M, with a limit of detection of 0.36 mu M for the fluorescence sensing of H2O2. Additionally, a linear range of 1.0-50.0 mu M and a limit of detection of 0.45 mu M were displayed for the detection of H2O2 by colorimetric assay. The feasibility in complex medium of the fabricated fluorescent and colorimetric dual-signal sensor was evaluated by the detection of H2O2 in phosphate buffer saline (PBS) and lake water samples. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Besides the vast research regarding the hybrid organic-inorganic perovskite (HOIP) materials used in the solar cell production, their properties are still not fully uncovered. In this paper, detailed investigation on the phase transitions in guanidinium lead iodide (GAPbI(3)) using vibrational spectroscopy techniques (IR and Raman) are presented. In addition to the well-known three phases of GAPbI(3) (denoted as I, II and III) another one existing in the temperature range from 48 degrees C to 160 degrees C is characterized. The thorough inspection of the vibrational spectra revealed some interesting changes occurring in the low temperature region (from -90 to -62 degrees C) that suggest presence of a new phase. Finally, a redefinition of the phase nomenclature according to the recommendations given by the IUCr is proposed. (C) 2021 Elsevier B.V. All rights reserved.
Al Abrak, Eman S.Aly, Eman M.Fouly, Marwa A.Mahmoud, Sherif S....
9页
查看更多>>摘要：Although retinal degeneration is one of the causes of blindness worldwide and involve the loss of the photoreceptors of the retina, the cause(s) of its development still need to be determined in order to reach an effective treatment instead of trying to slow the progression of the disease. Retinal degeneration condition was induced by intravitreal injection of 2 mu l of adenosine triphosphate (ATP) solution. The progress of the disease was monitored by retinal imaging (ocular coherence tomography, OCT) after 1, 8 and 15 days of injecting ATP. At the end of each period, retinal tissue was obtained where retinal proteins were extracted and then subjected to spectroscopic studies. Another part of the retinal tissue was investigated by Fourier transform infrared spectroscopy. The OCT images reflect significant reduction in retinal full thickness and provide evidence of intraretinal inflammation while; the obtained results indicate that both primarily and secondary structure of retinal proteins are influenced by the degeneration condition and, the electrical conductance of retinal proteins is decreased due to degeneration condition. Multivariate principal component analysis identifies that the variance noticed in the infrared spectra due to degeneration condition is not time dependent and revealed intra-groups structural dissimilarity. This dissimilarity was clearly resolved by fluorescence study where the content of amino acids phenylalanine, tryptophan and tyrosine varies with the progress of the degeneration condition. All together provide scientific facts that vision impairment is due to loss of signal transduction and formation of protein aggregates as well. (C) 2021 Elsevier B.V. All rights reserved.
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