查看更多>>摘要：Ultra-sensitive detection of target molecules by surface-enhanced Raman scattering (SERS) is crucial in a wide range of fields but remains a great challenge. In this work, we report a simple and effective protocol for obtaining highly SERS-sensitive probe by mixing iodide with silver sol. The specific iodide effect on the SERS sensitivity is systematically investigated. It is found that, iodide can effectively promote the SERS enhancement of anionic and cationic analytes, and I- ion has a higher activating effect on SERS than that of Cl- ion. The as-prepared SERS-active substrate demonstrates excellent enhancement for rhodamine 6G with a high Raman enhancement factor of 1.8 x 10(8), which allows the detection limit of 1.0 x 10(-13) M. Our findings in this work should be important for the developing of SERS theory and ultra-sensitive detection applications. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The spectral and photophysical properties of two four-ring alloxazine derivatives, naphtho[2,3-g] pteridine-2,4(1H,3H)-dione (1a) and 1,3-dimethylnaphtho[2,3-g]pteridine-2,4(1H,3H)-dione, (1b) were studied. The propensity of 1a for excited-state proton transfer reactions in the presence of acetic acid as a catalyst was also studied, showing no signature of the reaction occurring. In addition, quenching of 1a fluorescence by acetic acid was investigated. Singlet and triplet states and spectral data for 1a and 1b were calculated using density functional theory TD-DFT at B3LYP/6-31G(d) and UB3LYP levels. Finally, fluorescence lifetime imaging microscopy (FLIM) using 1a and 1b as fluorescence probes was applied to in vitro human red blood cells (RBCs) with and without tert-butyl hydroperoxide (TB) as an oxidising agent. To evaluate and compare the effects of 1a and 1b on the redox properties of RBCs, the fluorescence lifetime, amplitude and fractional intensities were calculated, and phasor plot analysis was performed. The results obtained show the appearance of a new proximal cluster in the phasor fingerprint of RBCs in the presence of 1b and a shorter fluorescence lifetime of RBCs in the presence of 1a.(c) 2022 Elsevier B.V. All rights reserved.
Al-Qaisi, Zyad H. J.Al-Garawi, Zahraa S.Al-Karawi, Ahmed Jasim M.Hammood, Ali JAsim...
17页
查看更多>>摘要：Two new water-soluble thiadiazole compounds are prepared and characterized with various techniques. These compounds, 5-amino-1,3,4-thiadiazole hydrochloride (1) and 5-amino-3-(N-propane-2-imine)-1, 3,4-thiadiazole chloride salt (2) were synthesized via Mannich reaction, and characterized by microelemental analysis, and some spectroscopic means (FTIR, UV-Vis, H-1 NMR, C-13 NMR and mass), in addition to single-crystal X-ray diffraction for compound 2. DFT calculations were conducted to study their geometry optimization, vibrational spectra, MEP maps, and NBO analysis. In addition, TD-DFT calculations were performed to study their absorption spectra. The prepared compounds were tested against Jack beans urease enzyme (in vitro) to indicate their antiureolytic activity potency. The activity of the enzyme was measured under optimal conditions, before and after mixing with the prepared organic compounds. The results showed that both compounds have potentially inhibited the enzyme activity with respect to their IC50 values: 13.76 mu M +/- 0.15 for 1, and 18.81 mu M +/- 0.18 for 2. These values are even lower than that of thiourea (21.40 +/- 0.21 mu M) as a standard inhibitor. The inhibition activity of urease enzyme was confirmed by a Lineweaver-Burk plot. According to the kinetic parameters obtained from the Lineweaver- Burk plot, the inhibition of urease enzyme by compounds 1 and 2 seems to be non-competitive. Molecular docking studies of the prepared compounds 1 and 2 were performed in order to interpret the obtained biological results and to investigate their interactions with the urease enzyme active site. These studies reveal that compounds 1 and 2 are good candidates as inhibitors for urease enzyme. Moreover, compound 1 exhibits a higher promising inhibition activity. (c) 2022 Elsevier B.V. All rights reserved.
Shafaq, SyedaMajeed, Muhammad IrfanNawaz, HaqRashid, Nosheen...
9页
查看更多>>摘要：Raman spectroscopy is an outstanding analytical tool increasingly utilized in the pharmaceutical field for the solid-state pharmaceutical drug analysis. In current study, the potential of Raman spectroscopy has been investigated for qualitative and quantitative analysis of solid dosage form of Losartan potassium. For this purpose, different solid dosage forms/concentrations of losartan potassium were prepared to compensate the commercially available pharmaceutical drug formulations and their Raman spectral data showed a gradual change in the specific Raman spectral features associated with the active pharmaceutical ingredient (API) of Losartan potassium as a function of change in the concentration. The Raman spectral data was analyzed by using Principal Component Analysis (PCA) for the classification of different spectral data sets of different concentrations of drug. Moreover, partial least square regression (PLSR) analysis was performed for monitoring the quantitative relation among different concentrations of Losartan potassium API and spectral data by constructing a predictive model. From the model, the value of root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were observed to be 0.38 and 2.98 respectively and the value of goodness of fit was found to be 0.99. Furthermore, the quantity of unknown/blind sample of Losartan potassium formulation was also estimated by using PLSR model. From these results, it is demonstrated that Raman spectroscopy can be considered to be used for quick and reliable quantitative analysis of pharmaceutical solids.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：We explore the mechanism specifically on quantum yields difference of 2-(4,4-Dimethyl-4,5-dihydroox azol-2-yl)-3-hydroxybenzonitrile (1-CN) and 4-(4,4-Dimethyl-4,5-dihydrooxazol-2-yl)-3-hydroxybenzo nitrile (3-CN) by density functional theory and time-dependent density functional theory within the Tamm-Dancoff approximation. The structures optimization and the potential energy curves scanning of singlet excited state directly prove that the excited state intramolecular proton transfer (ESIPT) can take place in 1-CN and 3-CN molecules. The calculated spectra show that the fluorescence peaks of two molecules come from the emission of keto* configuration. The non-covalent interaction and the atomic dipole moment corrected Hirshfeld charge are also analyzed. Through the comparison of emission oscillator strength between 1-CN and 3-CN molecules suggests that the radiative transition process is not the main reason for the difference on quantum yields. Internal conversion process is also excluded on account of the large energy gap between S-0 and S-1. Considering the interaction between singlet and tri-plet states, both molecules can undergo intersystem crossing. The prominent difference is that, compared with 3-CN, the larger spin-orbit coupling constant and smaller energy level difference promote the inter -system crossing process of 1-CN. This provides direct evidence for the fluorescence quantum yield of 1-CN is lower than that of 3-CN. We envision that the present work can provide help for the synthesis and application of ESIPT compounds with high quantum yields. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：A universal ratiometric fluorescence and colorimetric dual-mode sensing platform for detecting hydrogen peroxide (H2O2) and related metabolites in human fluid was constructed based on iron and nitrogen co-doped carbon dots (Fe/N-CDs). As a fluorescent nanomaterial with peroxidase-like property, Fe/N-CDs emits fluorescence at 449 nm (F-449) under excitation of incident ultraviolet light, and can catalyze the oxi-dation of o-phenylenediamine (OPD) by H2O2 for generating 2,3-diaminophenazine (oxOPD) that exhibits obvious absorption at 420 nm (A(420)) and fluorescence emission at 555 nm (F-555). The Forster resonance energy transfer (FRET) between Fe/N-CDs and oxOPD would result in the fluorescence quenching Fe/N- CDs and the fluorescence enhancement of oxOPD, which facilitates the quantitation of oxOPD by ratio metric fluorometry. Since the amount of generated oxOPD is determined by the amount of H2O2 consumed during the oxidation reaction, the detection of H2O2 and related metabolites can be realized by monitoring both ratiometric fluorescent (F-555/F-449) and colorimetric (absorption, A(420)) signals of oxOPD. This dual-mode sensing platform exhibits excellent selectivity and sensitivity toward with H2O2, xanthine and uric acid in both human serum and urine samples, demonstrating its good potential for monitoring H2O2 and metabolites involved in H(2)O(2)metabolism in human body. The detection limits (LODs) of H2O2, xanthine and uric acid obtained by this sensing platform were 0.07, 0.15, and 0.14 mu M for ratiometric fluorescence mode, and 0.12, 0.52, and 0.47 mu M for colorimetric mode, respectively. By utilizing appropriate oxidases in this universal sensing platform, the determination of other metabolites involved with producing H(2)O(2)can also be realized facilely. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：ABSTR A C T Dedicated handheld spectrometers have been adopted by first responders and law enforcement agencies for in situ identification of unknown substances. Real-time spectral matching process is a pixel-by-pixel comparing of the unknown spectra with reference data. In fact, the success rate of this process using a miniaturized portable Raman spectrometer relies mainly on the variety of reference data carried on the memory. This is a hurdle in miniaturizing and affordability of the current handheld spectrometers due to limited memory and computational power. In this study, we aim to mitigate this issue by utilizing the power of one-dimensional Convolutional Neural Networks (1DCNN) trained on millions of Raman spectra augmented from standard available reference databases. Specifically, an intentionally overfitted 1DCNN model can be substituted with the reference database of handheld spectrometers to alleviate the memory size and increase the identification process speed and accuracy. Our experimental results revealed that 1DCNN could identify one pure unknown Raman instance from thousands of classes with a high accuracy. Crown Copyright (c) 2022 Published by Elsevier B.V. All rights reserved.
查看更多>>摘要：The binding of caffeic acid (CA) and/or (-)-epicatechin gallate (ECG) to lysozyme was investigated by multispectroscopic methods and molecular docking. The effects of the single and combined binding on the structure, activity and stability of lysozyme and the synergistic antioxidant activity of CA and ECG were also studied. Fluorescence quenching spectra, time-resolved fluorescence spectra, and UV-vis absorption difference spectra all ascertained the static quenching mechanism of lysozyme by CA/ECG. Thermodynamic parameters indicated that CA and ECG competitively bound to lysozyme, and CA had a stronger binding affinity, which was consistent with the results of molecular docking. Hydrogen bonding, van der Waals' force and electrostatic interaction were the main driving forces for the binding process. Synchronous fluorescence spectra displayed that the interaction of CA/ECG exposed the tryptophan residues of lysozyme to a more hydrophilic environment. Circular dichroism spectroscopy, Fourier transform infrared spectroscopy and dynamic light scattering indicated that the binding of CA and/or ECG to lysozyme resulted in the change of the secondary structure and increased the particle size of lysozyme. The binding of CA and/or ECG to lysozyme inhibited the enzyme activity and enhanced the thermal stability of lysozyme. The combined application of CA and ECG showed antioxidant synergy which was influenced by the encapsulation of lysozyme and cellular uptake. In summary, this work provides theoretical guidance for lysozyme as a carrier for the combined application of CA and ECG.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：One of the advantages of investigating lipid phase transitions by thermoanalytical techniques such as DSC is manifested in the proportionality of the signal strength on a DSC curve, attributed to a particular thermotropic event, and its cooperativity degree. Accordingly, the pretransition of 1,2-dipalmitoyl-sn- glycero-3-phosphocholine (DPPC) is less noticeable than its main phase transition; as a matter of fact, when DSC measurements are performed at low heating rate, such low-cooperativity phase transition could go (almost) unnoticed. The aim of this work is to present temperature-dependent UV/Vis spectroscopy, based on a temperature-dependent change in DPPC suspension turbidity, as a technique applicable for determination of lipid phase transition temperatures. Multivariate analyzes of the acquired UV/ Vis spectra show that phase transitions of the low-cooperativity degree, such as pretransitions, can be identified with the same certainty as transitions of a high-cooperativity degree.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：By incorporating 4-nitrobenzene as the recognition unit into a stable hemicyanine skeleton based on IR 780, a designed near-infrared fluorescent off-on probe DNXI shows excellent analytical performance in real-time monitoring of carbon monoxide releasing molecule-2 (CORM-2) in living HeLa cells and zebra fish without transition metals. The response mechanism of CORM-2 with DNXI may reduce the nitro group to an amino group, followed by 1,6-rearrangement elimination reaction, resulting in the recovery of both color and fluorescence signal. As a result, DNXI shows very low background signal, which is rather desired for achieving sensitive detection of CORM-2. Compared with the existing CORM-2 probes, DNXI shows excellent optical performance in vitro and in vivo, high selectivity and sensitivity to CORM-2, as well as near-infrared fluorescence emission 712 nm, with a low detection limit of 103 nM. More importantly, DNXI is low cytotoxic, cell membrane permeable, and its applicability has been demonstrated for monitoring CORM-2 in living HeLa cells and zebrafish. These superior properties of the probe enable it have great potential to be used in biological systems or in vivo related studies.(c) 2022 Elsevier B.V. All rights reserved.
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