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San Andrés MP, Baños-Cabrera M, Gutiérrez-Fernández L, Díez-Pascual AM, Vera-López S. Fluorescence Study of Riboflavin Interactions with Graphene Dispersed in Bioactive Tannic Acid. Int J Mol Sci 2021; 22:ijms22105270. [PMID: 34067835 PMCID: PMC8156842 DOI: 10.3390/ijms22105270] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/07/2021] [Accepted: 05/13/2021] [Indexed: 12/23/2022] Open
Abstract
The potential of tannic acid (TA) as a dispersing agent for graphene (G) in aqueous solutions and its interaction with riboflavin have been studied under different experimental conditions. TA induces quenching of riboflavin fluorescence, and the effect is stronger with increasing TA concentration, due to π-π interactions through the aromatic rings, and hydrogen bonding interactions between the hydroxyl moieties of both compounds. The influence of TA concentration, the pH, and the G/TA weight ratio on the quenching magnitude, have been studied. At a pH of 4.1, G dispersed in TA hardly influences the riboflavin fluorescence, while at a pH of 7.1, the nanomaterial interacts with riboflavin, causing an additional quenching to that produced by TA. When TA concentration is kept constant, quenching of G on riboflavin fluorescence depends on both the G/TA weight ratio and the TA concentration. The fluorescence attenuation is stronger for dispersions with the lowest G/TA ratios, since TA is the main contributor to the quenching effect. Data obey the Stern–Volmer relationship up to TA 2.0 g L−1 and G 20 mg L−1. Results demonstrate that TA is an effective dispersant for graphene-based nanomaterials in liquid medium and a green alternative to conventional surfactants and synthetic polymers for the determination of biomolecules.
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Wiśniewski M, Czarnecka J, Bolibok P, Świdziński M, Roszek K. New Insight into the Fluorescence Quenching of Nitrogen-Containing Carbonaceous Quantum Dots-From Surface Chemistry to Biomedical Applications. MATERIALS (BASEL, SWITZERLAND) 2021; 14:ma14092454. [PMID: 34065161 PMCID: PMC8125974 DOI: 10.3390/ma14092454] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Revised: 05/01/2021] [Accepted: 05/05/2021] [Indexed: 12/13/2022]
Abstract
Carbon-based quantum dots are widely suggested as fluorescent carriers of drugs, genes or other bioactive molecules. In this work, we thoroughly examine the easy-to-obtain, biocompatible, nitrogen-containing carbonaceous quantum dots (N-CQDs) with stable fluorescent properties that are resistant to wide-range pH changes. Moreover, we explain the mechanism of fluorescence quenching at extreme pH conditions. Our in vitro results indicate that N-CQDs penetrate the cell membrane; however, fluorescence intensity measured inside the cells was lower than expected from carbonaceous dots extracellular concentration decrease. We studied the mechanism of quenching and identified reduced form of β-nicotinamide adenine dinucleotide (NADH) as one of the intracellular quenchers. We proved it experimentally that the elucidated redox process triggers the efficient reduction of amide functionalities to non-fluorescent amines on carbonaceous dots surface. We determined the 5 nm-wide reactive redox zone around the N-CQD surface. The better understanding of fluorescence quenching will help to accurately quantify and dose the internalized carbonaceous quantum dots for biomedical applications.
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Abstract
![]()
Following the advancements
and diversification in synthetic strategies
for porous covalent materials in the literature, the materials science
community started to investigate the performance of covalent organic
polymers (COPs) and covalent organic frameworks (COFs) in applications
that require large surface areas for interaction with other molecules,
chemical stability, and insolubility. Sensorics is an area where COPs
and COFs have demonstrated immense potential and achieved high levels
of sensitivity and selectivity on account of their tunable structures.
In this review, we focus on those covalent polymeric systems that
use fluorescence spectroscopy as a method of detection. After briefly
reviewing the physical basis of fluorescence-based sensors, we delve
into various kinds of analytes that have been explored with COPs and
COFs, namely, heavy metal ions, explosives, biological molecules,
amines, pH, volatile organic compounds and solvents, iodine, enantiomers,
gases, and anions. Throughout this work, we discuss the mechanisms
involved in each sensing application and aim to quantify the potency
of the discussed sensors by providing limits of detection and quenching
constants when available. This review concludes with a summary of
the surveyed literature and raises a few concerns that should be addressed
in the future development of COP and COF fluorescence-based sensors.
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Influence of Quenching and Subsequent Annealing on the Conductivity and Electromechanical Properties of Na 1/2Bi 1/2TiO 3-BaTiO 3. MATERIALS 2021; 14:ma14092149. [PMID: 33922624 PMCID: PMC8122941 DOI: 10.3390/ma14092149] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 04/08/2021] [Accepted: 04/18/2021] [Indexed: 11/17/2022]
Abstract
Na1/2Bi1/2TiO3-based materials have gained considerable attention for their potential to exhibit giant strain, very-high ionic conductivity comparable to yttria stabilized zirconia or high mechanical quality factor for use in high power ultrasonics. In recent times, quenching Na1/2Bi1/2TiO3-based compositions have been demonstrated to enhance the thermal depolarization temperature, thus increasing the operational temperature limit of these materials in application. This work investigates the role of quenching-induced changes in the defect chemistry on the dielectric, ferroelectric and piezoelectric properties of quenched Na1/2Bi1/2TiO3-BaTiO3. The quenched samples indeed demonstrate an increase in the bulk conductivity. Nevertheless, while subsequent annealing of the quenched samples in air/oxygen atmosphere reverts back the depolarization behaviour to that of a furnace cooled specimen, the bulk conductivity remains majorly unaltered. This implies a weak correlation between the defect chemistry and enhanced thermal stability of the piezoelectric properties and hints towards other mechanisms at play. The minor role of oxygen vacancies is further reinforced by the negligible (10–15%) changes in the mechanical quality factor and hysteresis loss.
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Tolba M, Elmansi H. Studying the quenching resulted from the formation of an association complex between olsalazine or sulfasalazine with acriflavine. ROYAL SOCIETY OPEN SCIENCE 2021; 8:210110. [PMID: 33996130 PMCID: PMC8059630 DOI: 10.1098/rsos.210110] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/22/2021] [Indexed: 05/03/2023]
Abstract
We report the detection and quantification of important ulcerative colitis drugs olsalazine (OLS) and sulfasalazine (SUL) by the spectrofluorometric method. The proposed method was optimized and validated by using the quenching effect on the acriflavine fluorescence. The method was applied on the detection and quantification of OLS and SUL under optimized conditions showing the calibration curves were linear (range: 1.0-10.0 µg ml-1), with correlation coefficients R 2 of 0.9999 for both drugs. The limits of detection (LOD) and quantification (LOQ) were 53 and 104 ng ml-1 for the OLS and 160 and 315 ng ml-1 for the SUL. This method permitted the analysis of OLS and SUL in their pure and pharmaceutical forms. The proposed spectrofluorimetric method was also evaluated against 'green' criteria and all the experimental results make it an eco-friendly and safe method for the detection of OLS and SUL.
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Junaidi J, Saputra MW, Marjunus R, Sembiring S, Hadi S. The Quenching and Sonication Effect on the Mechanical Strength of Silver Nanowires Synthesized Using the Polyol Method. Molecules 2021; 26:2167. [PMID: 33918851 PMCID: PMC8069117 DOI: 10.3390/molecules26082167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/07/2021] [Accepted: 04/08/2021] [Indexed: 11/24/2022] Open
Abstract
This study aims to determine the effect of fast cooling (quenching) on thermal properties, mechanical strength, morphology and size of the AgNWs. The synthesis of AgNWs was carried out at three different quenching-medium temperatures as follows: at 27 °C (ambient temperature), 0 °C (on ice), and -80 °C (in dry ice) using the polyol method at 130 °C. Furthermore, the AgNWs were sonified for 45 min to determine their mechanical strength. Scanning electron microscopy analysis showed that the quenched AgNWs had decreased significantly; at 27 °C, the AgNWs experienced a change in length from (40 ± 10) to (21 ± 6) µm, at 0 °C from (37 ± 8) to (24 ± 8) µm, and at -80 °C from (34 ± 9) to (29 ± 1) µm. The opposite occurred for their diameter with an increased quenching temperature: at 27 °C from (200 ± 10) to (210 ± 10) nm, at 0 °C from (224 ± 4) to (239 ± 8) nm, and at -80 °C from (253 ± 6) to (270 ± 10) nm. The lower the temperature of the quenching medium, the shorter the length and the higher the mechanical strength of AgNWs. The UV-Vis spectra of the AgNWs showed peak absorbances at 350 and 411 to 425 nm. Thermogravimetric analysis showed that AgNWs quenched at -80 °C have better thermal stability as their mass loss was only 2.88%, while at the quenching temperatures of 27 °C and 0 °C the mass loss was of 8.73% and 4.17%, respectively. The resulting AgNWs will then be applied to manufacture transparent conductive electrodes (TCEs) for optoelectronic applications.
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Acid-Sphingomyelinase Triggered Fluorescently Labeled Sphingomyelin Containing Liposomes in Tumor Diagnosis after Radiation-Induced Stress. Int J Mol Sci 2021; 22:ijms22083864. [PMID: 33917976 PMCID: PMC8068344 DOI: 10.3390/ijms22083864] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/26/2021] [Accepted: 03/29/2021] [Indexed: 11/21/2022] Open
Abstract
In liposomal delivery, a big question is how to release the loaded material into the correct place. Here, we will test the targeting and release abilities of our sphingomyelin-consisting liposome. A change in release parameters can be observed when sphingomyelin-containing liposome is treated with sphingomyelinase enzyme. Sphingomyelinase is known to be endogenously released from the different cells in stress situations. We assume the effective enzyme treatment will weaken the liposome making it also leakier. To test the release abilities of the SM-liposome, we developed several fluorescence-based experiments. In in vitro studies, we used molecular quenching to study the sphingomyelinase enzyme-based release from the liposomes. We could show that the enzyme treatment releases loaded fluorescent markers from sphingomyelin-containing liposomes. Moreover, the release correlated with used enzymatic activities. We studied whether the stress-related enzyme expression is increased if the cells are treated with radiation as a stress inducer. It appeared that the radiation caused increased enzymatic activity. We studied our liposomes’ biodistribution in the animal tumor model when the tumor was under radiation stress. Increased targeting of the fluorescent marker loaded to our liposomes could be found on the site of cancer. The liposomal targeting in vivo could be improved by radiation. Based on our studies, we propose sphingomyelin-containing liposomes can be used as a controlled release system sensitive to cell stress.
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Schleyer KA, Fetrow B, Zannes Fatland P, Liu J, Chaaban M, Ma B, Cui L. Dual-Mechanism Quenched Fluorogenic Probe Provides Selective and Rapid Detection of Cathepsin L Activity*. ChemMedChem 2021; 16:1082-1087. [PMID: 33295147 PMCID: PMC8202353 DOI: 10.1002/cmdc.202000823] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Indexed: 12/18/2022]
Abstract
Cathepsin L (CTL) is a cysteine protease demonstrating upregulated activity in many disease states. Overlapping substrate specificity makes selective detection of CTL activity difficult to parse from that of its close homologue CTV and the ubiquitous CTB. Current probes of CTL activity have limited applications due to either poor contrast or extra assay steps required to achieve selectivity. We have developed a fluorogenic probe, CTLAP, that displays good selectivity for CTL over CTB and CTV while exhibiting low background fluorescence attributed to dual quenching mechanisms. CTLAP achieves optimum CTL selectivity in the first 10 min of incubation, thus suggesting that it is amenable for rapid detection of CTL, even in the presence of competing cathepsins.
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Investigation of the Microstructural Evolution during Hot Stamping of a Carburized Complex Phase Steel by Laser-Ultrasonics. MATERIALS 2021; 14:ma14081836. [PMID: 33917237 PMCID: PMC8068057 DOI: 10.3390/ma14081836] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/01/2021] [Accepted: 04/06/2021] [Indexed: 11/16/2022]
Abstract
Prior carburization of semi-finished steel sheets is a new process variant in hot stamping to manufacture parts with tailored properties. Compared to conventional hot stamping processes, a complex phase typed steel alloy is used instead of 22MnB5. Yet recent investigations focused on final mechanical properties rather than microstructural mechanisms cause an increase in strength. Thus, the influence of additional carburization on the microstructural evolution during hot stamping of a complex phase steel CP-W®800 is investigated within this work. The phase transformation behavior, as well as the grain growth during austenitization, is evaluated by in-situ measurements employing a laser-ultrasound sensor. The results are correlated with additional hardness measurements in as-quenched condition and supplementary micrographs. The experiments reveal that the carburization process significantly improves the hardenability of the CP-W®800. However, even at quenching rates of 70 K/s no fully martensitic microstructure was achievable. Still, the resulting hardness of the carburized samples might exceed the fully martensitic hardness of 22MnB5 derived from literature. Furthermore, the carburization process has no adverse effect on the fine grain stability of the complex phase steel. This makes it more robust in terms of grain size than the conventional hot stamping steel 22MnB5.
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60
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Fu T, Deng X, Tian X, Liu G, Wang Z. Experimental study on temperature drop during roller quenching process of large-section ultra-heavy steel plate. Sci Prog 2021; 104:368504211009330. [PMID: 33979249 PMCID: PMC10305812 DOI: 10.1177/00368504211009330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Large-section ultra-heavy steel plates feature low cooling rate of central part during quenching process, as well as great differences in texture and performance along thickness direction. Wet jet impingement quenching test apparatus and multi-channel temperature recorder were developed to explore the temperature drop characteristics and its influential factors of ultra-heavy steel plate. The temperature drop curves of plates with different thickness (160, 220, and 300 mm) and weight (23-43 tons) were recorded during the quenching process, accompanied with the exploration on distribution rules of temperature gradient, heat flux density and cooling rate along thickness direction under different water volumes (9000-9400 m3/h) and pressures (0.4-0.8 MPa), upon which the three-dimensional inverse heat conduction model, surface heat transfer coefficient model and thermophysical parameter model were established using finite element and optimization methods. The overall results indicate the symmetric heat transfer between the upper and lower plate surfaces can be realized, when the water flow ratios of the upper and lower surfaces were 1:1.25 and 1:1.4 under pressures of 0.8 MPa and 0.4 MPa, respectively. The "temperature return" phenomenon was accompanied with changing heat flux density of wall surface of 220 mm- and 300 mm-thick plates. The lowest cooling rate along thickness direction appeared at 1/4 thickness position for the 160 mm- and 220 mm- thick plates during quenching, which was attributable to the synergy between heat flux density and temperature gradient. This work may pave a way for improving the cooling rate and quenching uniformity of ultra-heavy steel plates along thickness direction.
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Qiao Q, Guo X, Wen F, Chen L, Xu Q, Zheng N, Cheng J, Xue X, Wang J. Aptamer-Based Fluorescence Quenching Approach for Detection of Aflatoxin M 1 in Milk. Front Chem 2021; 9:653869. [PMID: 33842437 PMCID: PMC8024576 DOI: 10.3389/fchem.2021.653869] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 02/18/2021] [Indexed: 11/13/2022] Open
Abstract
Aflatoxin M1 (AFM1), one of the most toxic mycotoxins, is a feed and food contaminant of global concern. In this study, we developed a fast and simple method for detection of AFM1 based on a structure-switching signaling aptamer. This aptasensor is based on the change in fluorescence signal due to formation of an AFM1/aptamer complex. To generate the aptasensor, the specific aptamer was modified with FAM (carboxyfluorescein), and their complementary DNAs (cDNA) were modified with a carboxytetramethylrhodamine (TAMRA) quenching group. In the absence of AFM1, the aptamers were hybridized with cDNA, resulting in quenching of the aptamer fluorescence due to the proximity of the aptamer's fluorophore to the quenching group on the cDNA. On the other hand, in the presence of AFM1, a structural switch in the aptamer was induced by formation of an AFM1/aptamer complex. Changes in the structure of the aptamer led to the release of the cDNA, causing the generation of a fluorescence signal. Thus, AFM1 concentrations could be quantitatively monitored based on the changes in fluorescences. Under optimized conditions, this assay exhibited a linear response to AFM1 in the range of 1-100 ng/mL and a limit of detection of 0.5 ng/mL was calculated. This proposed aptasensor was applied to milk samples spiked with a dilution series of AFM1, yielding satisfactory recoveries from 93.4 to 101.3%. These results demonstrated that this detection technique could be useful for high-throughput and quantitative determination of mycotoxin levels in milk and dairy products.
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Straube H, Witte CP, Herde M. Analysis of Nucleosides and Nucleotides in Plants: An Update on Sample Preparation and LC-MS Techniques. Cells 2021; 10:689. [PMID: 33804650 PMCID: PMC8003640 DOI: 10.3390/cells10030689] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 03/15/2021] [Accepted: 03/16/2021] [Indexed: 02/06/2023] Open
Abstract
Nucleotides fulfill many essential functions in plants. Compared to non-plant systems, these hydrophilic metabolites have not been adequately investigated in plants, especially the less abundant nucleotide species such as deoxyribonucleotides and modified or damaged nucleotides. Until recently, this was mainly due to a lack of adequate methods for in-depth analysis of nucleotides and nucleosides in plants. In this review, we focus on the current state-of-the-art of nucleotide analysis in plants with liquid chromatography coupled to mass spectrometry and describe recent major advances. Tissue disruption, quenching, liquid-liquid and solid-phase extraction, chromatographic strategies, and peculiarities of nucleotides and nucleosides in mass spectrometry are covered. We describe how the different steps of the analytical workflow influence each other, highlight the specific challenges of nucleotide analysis, and outline promising future developments. The metabolite matrix of plants is particularly complex. Therefore, it is likely that nucleotide analysis methods that work for plants can be applied to other organisms as well. Although this review focuses on plants, we also discuss advances in nucleotide analysis from non-plant systems to provide an overview of the analytical techniques available for this challenging class of metabolites.
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Mei S, Zhou J, Sun H, Cai Y, Sun L, Jin D, Yan C. Networking State of Ytterbium Ions Probing the Origin of Luminescence Quenching and Activation in Nanocrystals. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2003325. [PMID: 33747733 PMCID: PMC7967042 DOI: 10.1002/advs.202003325] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 11/05/2020] [Indexed: 05/24/2023]
Abstract
At the organic-inorganic interface of nanocrystals, electron-phonon coupling plays an important but intricate role in determining the diverse properties of nanomaterials. Here, it is reported that highly doping of Yb3+ ions within the nanocrystal host can form an energy-migration network. The networking state Yb3+ shows both distinct Stark splitting peak ratios and lifetime dynamics, which allows quantitative investigations of quenching and thermal activation of luminescence, as the high-dimensional spectroscopy signatures can be correlated to the attaching and de-attaching status of surface molecules. By in-situ surface characterizations, it is proved that the Yb-O coordination associated with coordinated water molecules has significantly contributed to this reversible effect. Moreover, using this approach, the prime quencher -OH can be switched to -CH in the wet-chemistry annealing process, resulting in the electron-phonon coupling probability change. This study provides the molecular level insights and dynamics of the surface dark layer of luminescent nanocrystals.
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Glazier R, Shinde P, Ogasawara H, Salaita K. Spectroscopic Analysis of a Library of DNA Tension Probes for Mapping Cellular Forces at Fluid Interfaces. ACS APPLIED MATERIALS & INTERFACES 2021; 13:2145-2164. [PMID: 33417432 DOI: 10.1021/acsami.0c09774] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Oligonucleotide-based probes offer the highest spatial resolution, force sensitivity, and molecular specificity for cellular tension sensing and have been developed to measure a variety of molecular forces mediated by individual receptors in T cells, platelets, fibroblasts, B-cells, and immortalized cancer cell lines. These fluorophore-oligonucleotide conjugate probes are designed with a stem-loop structure that engages cell receptors and reversibly unfolds due to mechanical strain. With the growth of recent work bridging molecular mechanobiology and biomaterials, there is a need for a detailed spectroscopic analysis of DNA tension probes that are used for cellular imaging. In this manuscript, we conducted an analysis of 19 DNA hairpin-based tension probe variants using molecular dynamics simulations, absorption spectroscopy, and fluorescence imaging (epifluorescence and fluorescence lifetime imaging microscopy). We find that tension probes are highly sensitive to their molecular design, including donor and acceptor proximity and pairing, DNA stem-loop structure, and conjugation chemistry. We demonstrate the impact of these design features using a supported lipid bilayer model of podosome-like adhesions. Finally, we discuss the requirements for tension imaging in various biophysical contexts and offer a series of experimental recommendations, thus providing a guide for the design and application of DNA hairpin-based molecular tension probes.
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65
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Robkis DM, Hoang EM, Po P, Deutsch CJ, Petersson EJ. Side-chain thioamides as fluorescence quenching probes. Biopolymers 2021; 112:e23384. [PMID: 32740927 PMCID: PMC7744324 DOI: 10.1002/bip.23384] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 12/11/2022]
Abstract
Thioamides, single atom oxygen-to-sulfur substitutions of canonical amide bonds, can be valuable probes for protein folding and protease studies. Here, we investigate the fluorescence quenching properties of thioamides incorporated into the side-chains of amino acids. We synthesize and incorporate Fmoc-protected, solid-phase peptide synthesis building blocks for introducing Nε -thioacetyl-lysine and γ-thioasparagine. Using rigid model peptides, we demonstrate the distance-dependent fluorescence quenching of these thioamides. Furthermore, we describe attempts to incorporate of Nε -thioacetyl-lysine into proteins expressed in Escherichia coli using amber codon suppression.
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Sahoo J, Jaiswar S, Chatterjee PB, Subramanian PS, Jena HS. Mechanistic Insight of Sensing Hydrogen Phosphate in Aqueous Medium by Using Lanthanide(III)-Based Luminescent Probes. NANOMATERIALS 2020; 11:nano11010053. [PMID: 33379340 PMCID: PMC7824681 DOI: 10.3390/nano11010053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 12/17/2020] [Accepted: 12/23/2020] [Indexed: 11/16/2022]
Abstract
The development of synthetic lanthanide luminescent probes for selective sensing or binding anions in aqueous medium requires an understanding of how these anions interact with synthetic lanthanide probes. Synthetic lanthanide probes designed to differentiate anions in aqueous medium could underpin exciting new sensing tools for biomedical research and drug discovery. In this direction, we present three mononuclear lanthanide-based complexes, EuLCl3 (1), SmLCl3 (2), and TbLCl3 (3), incorporating a hexadentate aminomethylpiperidine-based nitrogen-rich heterocyclic ligand L for sensing anion and establishing mechanistic insight on their binding activities in aqueous medium. All these complexes are meticulously studied for their preferential selectivities towards different anions such as HPO42−, SO42−, CH3COO−, I−, Br−, Cl−, F−, NO3−, CO32−/HCO3−, and HSO4− at pH 7.4 in aqueous HEPES (2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid) buffer. Among the anions scanned, HPO42− showed an excellent luminescence change with all three complexes. Job’s plot and ESI-MS support the 1:2 association between the receptors and HPO42−. Systematic spectrophotometric titrations of 1–3 against HPO42− demonstrates that the emission intensities of 1 and 2 were enhanced slightly upon the addition of HPO42− in the range 0.01–1 equiv and 0.01–2 equiv., respectively. Among the three complexes, complex 3 showed a steady quenching of luminescence throughout the titration of hydrogen phosphate. The lower and higher detection limits of HPO42− by complexes 1 and 2 were determined as 0.1–4 mM and 0.4–3.2 mM, respectively, while complex 3 covered 0.2–100 μM. This concludes that all complexes demonstrated a high degree of sensitivity and selectivity towards HPO42−.
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Battaje RR, Bhondwe P, Dhaked HPS, Panda D. Evidence of conformational switch in Streptococcus pneumoniae FtsZ during polymerization. Protein Sci 2020; 30:523-530. [PMID: 33341988 DOI: 10.1002/pro.4015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 12/18/2020] [Accepted: 12/18/2020] [Indexed: 12/11/2022]
Abstract
FtsZ, the master coordinator of bacterial cell division, assembles into filaments in the presence of nucleotide. FtsZ from Streptococcus pneumoniae bears two tryptophan residues (W294 and W378) in its amino acid sequence. The tryptophan fluorescence of FtsZ increases during the assembly of FtsZ. We hypothesized that this increase in the fluorescence intensity was due to the change in the environment of one or both tryptophan residues. To examine this, we constructed two mutants (W294F and W378F) of FtsZ by individually replacing tryptophan with phenylalanine. The mutants displayed similar secondary structures, GTPase activity, and polymerization ability as the wild type FtsZ. During the polymerization, only one tryptophan (W294) showed an increase in its fluorescence intensity. Using time-correlated single-photon counting, the fluorescence lifetime of W294 was found to be significantly higher than W378, indicating that W294 was more buried in the structure than W378. The lifetime of W294 further increased during polymer formation, while that of W378 remained unchanged. Fluorescence quenching experiment suggested that the solvent exposure of W294 reduced during the polymerization of FtsZ. W294 is located near the T-7 loop of the protein, a region important for the monomer-monomer interaction during the formation of a protofilament. The results indicated that the region around W294 of S. pneumoniae FtsZ undergoes a conformational switch during polymerization as seen for FtsZ from other bacteria.
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Garoub M, Hefny AH, Omer WE, Elsaady MM, Abo-Aly MM, Sayqal AA, Alharbi A, Hameed A, Alessa H, Youssef AO, Mohamed EH, Gouda AA, Sheikh RE, Abou-Omar MN, El-Kemary MA, Attia MS. Highly Selective Optical Sensor Eu (TTA) 3 Phen Embedded in Poly Methylmethacrylate for Assessment of Total Prostate Specific Antigen Tumor Marker in Male Serum Suffering Prostate Diseases. Front Chem 2020; 8:561052. [PMID: 33324607 PMCID: PMC7724366 DOI: 10.3389/fchem.2020.561052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 09/01/2020] [Indexed: 11/13/2022] Open
Abstract
A low-cost, simple, and highly selective method was used for the assessment of total prostate specific antigen (tPSA) in the serum of prostate cancer patients. This method is based on quenching the intensity of luminescence displayed by the optical sensor Eu (TTA)3 phen/poly methylmethacrylate (PMMA) thin membrane or film upon adding different concentrations of tPSA. The luminescent optical sensor was synthesized and characterized through absorption, emission, scanning electron microscopy (SEM), and x-ray diffraction (XRD), and is tailored to present red luminescence at 614 nm upon excitation at 395 nm in water. The fabricated sensor fluorescence intensity is quenched in the presence of tPSA in aqueous media. The fluorescence resonance energy transfer (FRET) is the main mechanism by which the sensor performs. The sensor was successfully utilized to estimate tPSA in the serum of patients suffering prostate cancer in a time and cost effective way. The statistical results of the method were satisfactory with 0.0469 ng mL-1 as a detection limit and 0.99 as a correlation coefficient.
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Investigation of a Truncated Aptamer for Ofloxacin Detection Using a Rapid FRET-Based Apta-Assay. Antibiotics (Basel) 2020; 9:antibiotics9120860. [PMID: 33287135 PMCID: PMC7761777 DOI: 10.3390/antibiotics9120860] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 11/24/2020] [Accepted: 12/01/2020] [Indexed: 11/17/2022] Open
Abstract
In this work, we describe the use of a new truncated aptamer for the determination of ofloxacin (OFL), being a principal quinolone commonly used in both human and animal healthcare. Since the affinity of a 72-mer ssDNA sequence has been previously described without further investigations, this paper demonstrates the first computational prediction of the binding motif between this aptamer and OFL through in silico molecular docking studies. Besides, we suggest the application of the characterized recognition mechanism in a simple FRET (Förster Resonance Energy Transfer) pattern for the rapid aptasensing of the quinolone of interest. Accordingly, our approach harnesses the fluorescence quenching of the fluorescein-tagged aptamer (FAM-APT) induced by its partial hybridization to a tetramethyl rhodamine-labelled complementary ssDNA (TAMRA-cDNA). In such a structure, dye labels brought into close proximity act as a FRET pair. Upon ofloxacin addition, an affinity competition occurs to form a more stable FAM-APT/OFL complex, thus unquenching the FAM-APT signal. Interestingly, the recovered fluorescence intensity was found to correlate well with the antibiotic's concentrations in the range of 0.2-200 μM in HEPES buffer, with a linear response that ranged between 0.2 and 20 μM. The rapid apta-assay achieved limits of detection and quantification of 0.12 and 0.40 μM, respectively. The truncated aptamer has also shown an improved specificity toward OFL than other quinolones, compared to the original full-length aptamer described in previous works. Finally, the practical application of the developed apta-assay was successfully confirmed to detect OFL quinolone in spiked milk samples, with satisfactory recoveries ranging between 97.4% and 111.4%.
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Baruah S, Aier M, Puzari A. Fluorescent probe sensor based on (R)-(-)-4-phenyl-2-oxazolidone for effective detection of divalent cations. LUMINESCENCE 2020; 35:1206-1216. [PMID: 32510851 DOI: 10.1002/bio.3830] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 04/27/2020] [Accepted: 05/06/2020] [Indexed: 01/19/2023]
Abstract
Significant progress attained in sensor science in recent years has resulted in the development of highly efficient fluorescence probes for sensing metal ions. Fluorescent molecular probes based on (R)-(-)-4-phenyl-2-oxazolidone are reported here. Fluorescence studies indicated that the molecular probe could be used successfully to sense divalent metal cations such as Cu2+ , Co2+ , Pb2+ , and Zn2+ . The addition of divalent metal cations to the molecular probe produced a specific interaction pattern under UV-visible and fluorescence spectroscopy. These molecules could detect metal cations using fluorescence quenching. Stern-Volmer plots were used to determine quenching rate coefficients, which were calculated to be 2 × 101 , 1.06 × 103 and 7.39 × 102 M-1 s-1 for copper, cobalt, and zinc respectively. Calculation of limit of detection for heavy metal cations revealed that the reported molecular probes improved the limit of detection compared with available standard data. Limit of quantitation values were also well within the permissible range. The frontier energy gap of highest occupied molecular orbital to the lowest unoccupied molecular orbital was evaluated using the density functional theory approach and Gaussian 09 W software, which complemented the coordination of azetidinones with divalent metal ions.
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Krawczyk P, Jurczyszyn M, Pawlak J, Salamon W, Baran P, Kmita A, Gondek Ł, Sikora M, Kapusta C, Strączek T, Wyrwa J, Żywczak A. High-Entropy Perovskites as Multifunctional Metal Oxide Semiconductors: Synthesis and Characterization of (Gd 0.2Nd 0.2La 0.2Sm 0.2Y 0.2)CoO 3. ACS APPLIED ELECTRONIC MATERIALS 2020; 2:3211-3220. [PMID: 33196046 PMCID: PMC7660934 DOI: 10.1021/acsaelm.0c00559] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Accepted: 09/18/2020] [Indexed: 05/17/2023]
Abstract
Single-phase multicomponent perovskite-type cobalt oxide containing five cations in equiatomic amounts on the A-site, namely, (Gd0.2Nd0.2La0.2Sm0.2Y0.2)CoO3, has been synthesized via the modified coprecipitation hydrothermal method. Using an original approach for heat treatment, which comprises quenching utilizing liquid nitrogen as a cooling medium, a single-phase ceramic with high configuration entropy, crystallizing in an orthorhombic distorted structure was obtained. It reveals the anomalous temperature dependence of the lattice expansion with two weak transitions at approx. 80 and 240 K that are assigned to gradual crossover from the low- via intermediate- to high-spin state of Co3+. The compound exhibits weak ferromagnetism at T ≤ 10 K and signatures of antiferromagnetic correlations in the paramagnetic phase. Ab initio calculations predict a band gap Δ = 1.18 eV in the ground-state electronic structure with the dominant contribution of O_p and Co_d orbitals in the valence and conduction bands, respectively. Electronic transport measurements confirm the negative temperature coefficient of resistivity characteristic to a semiconducting material and reveal a sudden drop in activation energy at T ∼ 240 K from E a ∼ 1 eV in the low-temperature phase to E a ∼ 0.3 eV at room temperature. The possibility of fine tuning of the semiconducting band gap via a subtle change in A-site stoichiometry is discussed.
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Dilatometric and Microstructural Study of Martensite Tempering in 4% Mn Steel. MATERIALS 2020; 13:ma13194442. [PMID: 33036358 PMCID: PMC7579211 DOI: 10.3390/ma13194442] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/01/2020] [Accepted: 10/02/2020] [Indexed: 11/17/2022]
Abstract
This paper presents the results of martensite tempering resistance in 4% Mn steel. The material was quenched and tempered at 350 °C for 15, 30, and 60 min. The analysis of the quenching and tempering was carried out using dilatometric and microstructural approaches. The phase composition was assessed using X-ray diffraction. The Ms temperature and tempering progress were simulated using JMatPro software. The dilatometric analysis revealed a small decrease in the relative change in length (RCL) during tempering. This decrease was connected to the precipitation kinetics of cementite within the martensite laths. The microstructure investigation using a scanning electron microscope showed a very small amount of carbides, even for the longest tempering time. This showed the high tempering resistance of the martensite in medium-Mn steels. The hardness results showed an insignificant decrease in the hardness depending on the tempering time, which confirmed the high tempering resistance of martensite.
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Wittenzellner T, Sumarli S, Schaar H, Wang F, Ma D, Bührig-Polaczek A. Microstructural Investigations of Ni-Based Superalloys by Directional Solidification Quenching Technique. MATERIALS 2020; 13:ma13194265. [PMID: 32987951 PMCID: PMC7579343 DOI: 10.3390/ma13194265] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 09/19/2020] [Accepted: 09/21/2020] [Indexed: 11/26/2022]
Abstract
The improvement of the mechanical properties of Ni-based superalloys is achieved in most cases by modifying the chemical composition. Besides that, the processing can be modified to optimize the as-cast microstructure with regard to the mechanical properties. In this context, the present study highlights the solidification mechanism of several Ni-based superalloys by conducting experiments using a modified, laboratory-scale Bridgman-Stockbarger furnace. In that context, the single-crystal rods are partially melted, directionally solidified and quenched sequentially. Several characterization methods are applied to further analyze the influence of the alloying elements and the variation of the withdrawal rate on the as-cast microstructure. Four stages of solidification are distinguished whereby the morphology observed in the different stages mainly depends on the cooling rate and the local concentration of the carbide forming elements. The effect of carbide precipitation and the effect on the as-cast microstructure is investigated by employing energy dispersive X-ray spectrometry (EDX) and electron backscatter diffraction (EBSD) analysis techniques. A local polycrystalline structure is observed in the single-crystal system as consequence of the influence of the carbon content and the cooling rate. The present work aims to develop strategies to suppress the formation of the polycrystalline structure to maintain the single-crystal microstructure.
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Roshdy A, Elmansi H, Shalan S, Elbrashy A. Use of eosin for green spectroscopic determination of mebendazole. LUMINESCENCE 2020; 35:788-796. [PMID: 32026588 DOI: 10.1002/bio.3785] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 12/09/2019] [Accepted: 01/20/2020] [Indexed: 11/11/2022]
Abstract
New, sensitive, and reliable spectroscopic methods were constructed for the fast determination of the anthelmintic drug mebendazole. The methods depended on the reaction of the amino group in mebendazole with eosin in acidic medium forming an ion pair complex. The first method, Method I, relied on quenching of the native fluorescence of eosin after reaction with mebendazole at pH 3.7 using acetate buffer. Fluorescence quenching was measured at 538 nm after excitation at 518 nm. This method showed a linear response over the concentration range 5.0-20.0 μg/ml. The second method, Method II, was based on measuring the absorbance of the formed complex at 554 nm; the method showed good linearity from 7.0 to 22.0 μg/ml. Different parameters that influenced the formation of the reaction product were carefully investigated to reach the optimized conditions. A comparison between the proposed methods and a previous spectrophotometric method was carried out and there was no significant difference between them. The methods could be applied successfully to determine mebendazole in its tablet form. Moreover, the methods used water as diluting solvent, which made them compatible with the 'green' analytical chemistry principles. No organic solvents were used throughout the study.
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Parra-Rivero O, Paes de Barros M, Prado MDM, Gil JV, Hornero-Méndez D, Zacarías L, Rodrigo MJ, Limón MC, Avalos J. Neurosporaxanthin Overproduction by Fusarium fujikuroi and Evaluation of Its Antioxidant Properties. Antioxidants (Basel) 2020; 9:E528. [PMID: 32560158 PMCID: PMC7346100 DOI: 10.3390/antiox9060528] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 06/11/2020] [Accepted: 06/12/2020] [Indexed: 11/16/2022] Open
Abstract
Neurosporaxanthin (NX) is a carboxylic carotenoid produced by some filamentous fungi, including species of the genera Neurospora and Fusarium. NX biosynthetic genes and their regulation have been thoroughly investigated in Fusarium fujikuroi, an industrial fungus used for gibberellin production. In this species, carotenoid-overproducing mutants, affected in the regulatory gene carS, exhibit an upregulated expression of the NX pathway. Based on former data on a stimulatory effect of nitrogen starvation on carotenoid biosynthesis, we developed culture conditions with carS mutants allowing the production of deep-pigmented mycelia. With this method, we obtained samples with ca. 8 mg NX/g dry mass, in turn the highest concentration for this carotenoid described so far. NX-rich extracts obtained from these samples were used in parallel with carS-complemented NX-poor extracts obtained under the same conditions, to check the antioxidant properties of this carotenoid in in vitro assays. NX-rich extracts exhibited higher antioxidant capacity than NX-poor extracts, either when considering their quenching activity against [O2(1g)] in organic solvent (singlet oxygen absorption capacity (SOAC) assays) or their scavenging activity against different free radicals in aqueous solution and in liposomes. These results make NX a promising carotenoid as a possible feed or food additive, and encourage further studies on its chemical properties.
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