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New Assay Method Based on Raman Spectroscopy for Enzymes Reacting with Gaseous Substrates
摘要： Enzyme activity is typically assayed by quantitatively measuring the initial and final concentrations of the substrates and/or products over a defined time period. For enzymatic reactions involving gaseous substrates, the substrate concentrations can be estimated either directly by gas chromatography or mass spectrometry, or indirectly by absorption spectroscopy, if the catalytic reactions involve electron transfer with electron mediators that exhibit redox-dependent spectral changes. We have developed a new assay system for measuring the time course of enzymatic reactions involving gaseous substrates based on Raman spectroscopy. This system permits continuous monitoring of the gas composition in the reaction cuvette in a non-invasive manner over a prolonged time period. We have applied this system to the kinetic study of the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F. This enzyme physiologically catalyzes the reversible oxidation of H2 and also possesses the non-physiological functions of H/D exchange and nuclear spin isomer conversion reactions. The proposed system has the additional advantage of enabling us to measure all of the hydrogenase-mediated reactions simultaneously. Using the proposed system, we confirmed that H2 (the fully exchanged product) is concomitantly produced alongside HD by the H/D exchange reaction in the D2/H2O system. Based on a kinetic model, the ratio of the rate constants of the H/D exchange reaction (k) at the active site and product release rate (kout) was estimated to be 1.9±0.2. The proposed assay method based on Raman spectroscopy can be applied to the investigation of other enzymes involving gaseous substrates.
关键词： kinetic experiment,H/D exchange reaction,quantitative analysis of gaseous substrates,Raman spectroscopy,non-invasive measurement,[NiFe] hydrogenase
更新于2025-09-23 15:23:52
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Paramagnetic surface defects in LiMgPO<sub>4</sub>
摘要： The EPR spectra obtained at 300 K and 115 K are indicative of the existence of charged defects in LiMgPO4. The main imperfections are identified as a radical CO-3 (g=2) and a singly charged oxygen vacancy (g1=2.45, g2=2.20, g3=2.00). The presence of carbon-containing groups is proved by Raman spectroscopy. The assumption is made that the defects are located mainly on the surface of the grains. Thermoluminescent characteristics of LiMgPO4 annealed in atmospheres with different pO2 demonstrate that the surface defects impair the efficiency of LiMgPO4 as a dosimetric material.
关键词： Thermoluminescence.,Defects,EPR,Raman spectroscopy,LiMgPO4
更新于2025-09-23 15:23:52
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Structural and vibrational properties of PVT grown BiTeCl microcrystals
摘要： High-quality BiTeCl microcrystals are grown by the physical vapor transport (PVT) method without using a foreign transport agent. The plate-like microcrystals with a developed (0001) surface are up to ~500 μm in diameter. The grown crystal phase composition was identified by the X-ray single crystal structure analysis in space group P63mc: a = 4.2475(6) ?, c = 12.409(2) ?, Z = 2 (R = 0.0343). The BiTeCl microcrystal phase purity was verified by Raman microspectrometry under excitation at λ = 632.8 and 532.1 nm.
关键词： PVT crystal growth,crystal structure,topological insulator,SEM,BiTeCl,Raman spectroscopy
更新于2025-09-23 15:23:52
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Raman-Enhanced Spectroscopy (RESpect) Distinguishes Anal Squamous Intraepithelial Lesions in HIV-Serodiscordant Couples
摘要： HIV-positive individuals are at increased risk for pre-cancerous anal squamous intraepithelial lesions (SILs). Anal cytology and digital rectal examination are performed as screening tools but extensive training and appropriate instruments are required to follow-up on an abnormal anal cytology. Thus novel approaches to SIL evaluation could improve better healthcare follow up by efficient and timely diagnosis to offer treatment options. Recently, Raman-enhanced spectroscopy (RESpect) has emerged as a potential new tool for early identification of SIL. RESpect is a non-invasive, label-free, laser-based technique that identifies molecular composition of tissues and cells. HIV-serodiscordant couples had anal biopsies obtained during high resolution anoscopy. RESpect was performed on the specimens. Principal Component Analysis of the data identified differences between normal and abnormal tissue as well as HIV-positive and HIV-negative individuals of each couple even with similar pathologies. RESpect has the potential to change the paradigm of anal pathology diagnosis and could provide insight into different pathways leading to SIL in HIV-serodiscordant couples.
关键词： Anal Neoplasia,Raman Spectroscopy,HIV-Serodiscordant
更新于2025-09-23 15:23:52
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Raman spectroscopy and its use for live cell and tissue analysis
摘要： As research progresses in the field of life sciences, there is an increased demand for new technologies that can allow us to study intact cells and tissues. The quantitative analysis and mathematical modeling of living things based on empirical data is useful for connecting molecular biology to new areas, such as computational biology. Raman spectroscopy is regarded as one of the possible methods by which we can observe living organisms in a noninvasive manner. This could improve the quality of research in the field of medicine and health and will largely contribute to society in the future. The present review introduces some techniques based on Raman spectroscopy and evaluates their applications in intact live samples.
关键词： Raman probe,Raman spectroscopy,Biomedical,in vivo
更新于2025-09-23 15:22:29
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Transverse phonons and intermediate-range order in Sr-Mg fluorophosphate glasses
摘要： Vibrational and ultrasonic spectroscopies have been employed to study the composition and polarization dependence of the vibrational and elastic properties of the pseudo-binary mixed fluoride-phosphate glass-forming system xSr(PO3)2-(1-x)(0.62MgF2-0.38AlF3) with x: 0, 0.04, 0.06, 0.1, 0.15, 0.2, 0.3, 0.4, 0.8, 0.9 and 1. Composition-induced alterations in the short-range order have been quantitatively followed by means of Raman and IR spectroscopies. The analysis has shown that the incorporation of the phosphate groups in the fluoride network results in a less interconnected network with suppressed rigidity. The specific amorphous materials have been used as a model system in terms of wide glass-forming ability to elucidate the effect of variation in connectivity between the fluoride and phosphate sub-networks on the Boson peak nature. Emphasis has been given in the low-frequency Raman phenomenology, which in conjunction with the elastic properties allowed us to establish a possible link between the Boson peak and the transverse phonons in these glasses.
关键词： phonons,amorphous materials,oxide glasses,Boson peak,elastic properties,Raman spectroscopy,ATR spectroscopy
更新于2025-09-23 15:22:29
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Biodegradability of Disulfide-Organosilica Nanoparticles Evaluated by Soft X-ray Photoelectron Spectroscopy: Cancer Therapy Implications
摘要： Two kinds of organosilica nanoparticles (NPs) that were fabricated from thiol-containing precursors, (3-mercaptopropyl)trimethoxysilane and (3-mercaptopropyl)methyldimethoxysilane (MPDMS), are potential delivery vehicles of anticancer drugs. MPMS can form three siloxane bonds, but MPDMS forms two siloxane bonds as the maximum limit. Hence, disulfide bonds can be involved in the three-dimensional morphology of MPDMS NPs. In addition, NPs containing disulfide bonds are potentially degraded by a reduced form of glutathione (GSH). To examine reactions between the organosilica NPs and GSH, the NPs were incubated in 10 mM GSH aqueous solution at 37 °C for 7 d and the products were analyzed using field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and soft X-ray photoelectron spectroscopy (XPS). The Raman spectra showed the presence of disulfide bonds in the MPDMS NPs and the absence of disulfide bonds in MPMS NPs. The results of XPS measurements suggested that the disulfide bonds in the outer layer of MPDMS NPs were reduced to thiol groups. FE-SEM observations of MPDMS NPs detected changes in NP morphology after the GSH incubation. These results support the idea that MPDMS NPs contain disulfide bonds and are degradable by GSH. Therefore, MPDMS NPs possess a biodegradable feature that is advantageous for clinical translation, that is, nanomedicine.
关键词： (3-mercaptopropyl)methyldimethoxysilane,nanoparticles,(3-mercaptopropyl)trimethoxysilane,biodegradability,glutathione,X-ray photoelectron spectroscopy,Raman spectroscopy
更新于2025-09-23 15:22:29
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Analyzing carotenoids of snow algae by Raman microspectroscopy and high-performance liquid chromatography
摘要： We tested the potential of Raman microspectroscopy to determine carotenoid pigments — both primary (lutein, beta-carotene) and secondary (astaxanthin) carotenoids — in the different species and life-cycle stages of snow algae from the order Chlamydomonadales (Chlorophyta). We compared the performance of Raman spectrometry to a reference method of biological pigment analysis, high-performance liquid chromatography (HPLC). The three main carotenoid Raman bands of the astaxanthin-rich red cysts were located at 1520, 1156 and 1006 cm-1. The shifts (orange aplanozygotes and green motile cells with flagella) in the position of the ν1(C=C) Raman band of the polyenic chain is consistent with the expected changes in the ratios of the various carotenoid pigments. Flagellated green cells commonly contain lutein as a major carotenoid, together with minor amounts of β-carotene and varying amounts of antheraxanthin, violaxanthin and neoxanthin. Aplanozygotes contain mixtures of both primary and secondary carotenoids. In most cases, the ν1(C=C) band is an overlapping set of bands, which is due to the signal of all carotenoid pigments in the sample, and a deconvolution along with the band position shifts (mainly ν1) could be used to characterize the mixture of carotenoids. However, the ability of Raman spectroscopy to discriminate between structurally slightly differing carotenoid pigments or several carotenoids in an admixture in an unknown biological system remains limited.
关键词： HPLC,Snow algae,Biomarker,Raman spectroscopy,Exobiology,Carotenoids
更新于2025-09-23 15:22:29
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Probing the Domain Architecture in 2D α-Mo <sub/>2</sub> C via Polarized Raman Spectroscopy
摘要： MXenes are emerging 2D materials with intriguing properties such as excellent stability and high conductivity. Here, a systematic study on the Raman spectra of 2D α-Mo2C (molybdenum carbide), a promising member in MXene family, is conducted. Six experimentally observed Raman modes from ultrathin α-Mo2C crystal are first assigned with the assistance of phonon dispersion calculated from density functional theory. Angle-resolved polarized Raman spectroscopy indicates the anisotropy of α-Mo2C in the b–c plane. Raman spectroscopy is further used to study the unique domain structures of 2D α-Mo2C crystals grown by chemical vapor deposition. A Raman mapping investigation suggests that most of the α-Mo2C flakes contain multiple domains and the c-axes of neighboring domains tend to form a 60° or 120° angle, due to the weak Mo–C bonds in this interstitial carbide and the low formation energy of the carbon chains along three equivalent directions. This study demonstrates that polarized Raman spectroscopy is a powerful and effective way to characterize the domain structures in α-Mo2C, which will facilitate the further exploration of the domain-structure-related properties and potential applications of α-Mo2C.
关键词： α-Mo2C,in-plane anisotropy,2D crystals,transition metal carbides,Raman spectroscopy
更新于2025-09-23 15:22:29
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Raman Spectroscopy through the Indenter Working as an Optical Objective
摘要： The transparent indenter which can used as an optical objective were tested to obtained a spectra during the indentation. A special device which comprises the transparent indenter and actuator was developed and embedded into the Raman spectrometer. An indentation into the silicon sample was performed and phases that exist under the load and without it were identi?ed.
关键词： transparent tip,hardness,Raman spectroscopy,in-situ observation
更新于2025-09-23 15:22:29