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Articoli di riviste sul tema "Radical quantification"

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Autore: Grafiati

Pubblicato: 25 maggio 2024

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1

Schwarz-Selinger, T., V. Dose, W. Jacob e A. von Keudell. "Quantification of a radical beam source for methyl radicals". Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 19, n. 1 (gennaio 2001): 101–7. http://dx.doi.org/10.1116/1.1326939.

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2

Gardner, Jonathan M., e Steven D. Aust. "Quantification of hydroxyl radical produced during phacoemulsification". Journal of Cataract & Refractive Surgery 35, n. 12 (dicembre 2009): 2149–53. http://dx.doi.org/10.1016/j.jcrs.2009.06.030.

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3

Cho, Eun Chul, Ju A. La, Sora Lim e Ji Eun Song. "Gold/Silver-Polymer Hybrid Nanostructures as Thermoreversible Optical Sensors and Probes for the Quantification Radical Compounds". MRS Proceedings 1802 (2015): 41–44. http://dx.doi.org/10.1557/opl.2015.833.

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ABSTRACTWe present gold (Au) and silver (Ag) nanoparticles (NPs) could be used not only for stimuli-responsive optical sensors but also for the quantification of radical compounds when these nanoparticles are suitably combined with polymeric materials. When Au NPs are assembled 2-dimensionally on the surface of hydrogel NPs which respond to temperatures, the hybrid NPs displayed thermoreversible multiple color switching. Accordingly, optical bandwidths of the hybrid NPs are reversibly changed with temperatures: with hybrid NPs assembled with 51 nm Au NPs, prominent optical signals are recorded at 900 nm at 50 °C while most of extinction signals are shown below 600 nm at room temperatures. In addition, we demonstrate the modification of Ag NPs’ surfaces (nanocubes and nanospheres) with polyelectrolytes (either positive or negative) could extend the quantifiable detection ranges of radical compounds. Through the surface modification of Ag NPs, the polyelectrolytes protect the Ag NPs by probably either retarding (forming diffusion barriers) or preventing (blocking/entrapping/scavenging) the arrival of radicals to Ag NPs or both. The roles of the polyelectrolytes are demonstrated by using radical compounds produced from tetrahydrofuran and H2O2. From the results, we could obtain calibration curves for the wide-range quantification of radical compounds.

4

Blakley, Richard L., Dwight D. Henry, Walter T. Morgan, William L. Clapp, Carr J. Smith e David Barr. "Quantitative Electron Paramagnetic Resonance: The Importance of Matching the Q-Factor of Standards and Samples". Applied Spectroscopy 55, n. 10 (ottobre 2001): 1375–81. http://dx.doi.org/10.1366/0003702011953504.

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Electron paramagnetic resonance (EPR) quantification of free radicals from different samples facilitates comparison of free radical concentrations. Stable free radicals, such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), in a suitable solvent (e.g., benzene) can be used as a quantification standard. Free radicals found in samples can be shorter lived than radicals in prepared standards and require stabilizing spin-trapping agents such as N-tert-butyl-α-phenylnitrone (PBN) in an appropriate solvent (e.g., benzene). Analysis in our laboratory showed that free radicals from spin-trapped samples quantified against a standard of TEMPO in benzene displayed large differences among identical samples measured on either a Micro-Now 8300, Micro-Now 8400, or Bruker EMX EPR instrument. The Bruker instrument reported that the typical TEMPO in benzene standard had a Q-factor of ∼4400 while the Q-factor of our PBN-containing samples was ∼2500. (The Q-factor is inversely proportional to the amount of dissipated microwave energy in an EPR cavity.) By placing the TEMPO standard in a PBN/benzene solvent matrix we were able to match the Q-factor of our standards and samples, resulting in each of the three EPR instruments giving the same quantified free radical yields for the samples. This result points out the importance of matching the Q-factor between samples and standards for any quantitative EPR measurement.

5

Morgan, Christopher G., Mark M. Gleason e Ronald Vane. "Quantification of Contaminant Removal by Evactron Cleaning Using Quartz Crystal Thickness Monitors". Microscopy Today 15, n. 5 (settembre 2007): 22–25. http://dx.doi.org/10.1017/s1551929500061198.

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Hydrocarbon (HC) contamination is a persistent problem for users of electron microscopes (EMs), often leading to image distortion and interference with nanoprobing. The Evactron De-Contaminator (D-C) has been available for HC contamination removal in EMs since 1999. The Evactron D-C uses low power radio frequency (RF) generated plasma in order to produce oxygen radicals that clean the EM. The Oxygen Radical Source (ORS) is attached to the EM chamber, and a controlled leak of oxygen containing gas such as room air is passed through the plasma in order to produce oxygen radicals. The oxygen radicals chemically react with the HCs to form volatile oxidation products such as H2O, CO and CO2. These volatile compounds are pumped out of the EM chamber.

6

Rutely C., Burgos Castillo, Fontmorin Jean-M., Tang Walter Z., Dominguez-Benetton Xochitl e Sillanpää Mika. "Towards reliable quantification of hydroxyl radicals in the Fenton reaction using chemical probes". RSC Advances 8, n. 10 (2018): 5321–30. http://dx.doi.org/10.1039/c7ra13209c.

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7

ICHIKAWA, Kazuhiro, Sang-Kuk HAN e Hideo UTSUMI. "Quantification of hydroxyl radical during ozonation in batch system." Journal of Japan Society on Water Environment 22, n. 11 (1999): 921–25. http://dx.doi.org/10.2965/jswe.22.921.

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8

Hu, Na, e Sarah A. Green. "Acetyl radical generation in cigarette smoke: Quantification and simulations". Atmospheric Environment 95 (ottobre 2014): 142–50. http://dx.doi.org/10.1016/j.atmosenv.2014.06.027.

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9

Goyal, Parveen Kumar, Santosh Kumar Verma e Anil Kumar Sharma. "Quantification of Total Phenolic and Flavonoid Contents, and Evaluation of Free Radical Scavenging Potential of Vernonia cinerea". Asian Pacific Journal of Health Sciences 4, n. 3 (30 settembre 2017): 279–87. http://dx.doi.org/10.21276/apjhs.2017.4.3.42.

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10

Koshiishi, Ichiro, Kazunori Tsuchida, Tokuko Takajo e Makiko Komatsu. "Quantification of lipid alkyl radicals trapped with nitroxyl radical via HPLC with postcolumn thermal decomposition". Journal of Lipid Research 46, n. 11 (16 agosto 2005): 2506–13. http://dx.doi.org/10.1194/jlr.d500006-jlr200.

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Botelho, Ricardo Vieira, Matheus Fernandes de Oliveira e Jose Marcus Rotta. "Quantification of Vertebral Involvement in Metastatic Spinal Disease". Open Orthopaedics Journal 7, n. 1 (19 agosto 2013): 286–91. http://dx.doi.org/10.2174/1874325001307010286.

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Introduction: For patients with a solitary and well-delimitated spinal metastasis that resides inside the vertebral body, without vertebral canal invasion, and who are in good general health with a long life expectancy, en bloc spondylectomy/total vertebrectomy combined with the use of primary stabilizing instrumentation has been advocated. However, clinical experience suggests that these qualifying conditions occur very rarely. Objective: The purpose of this paper is to quantify the distribution of vertebral involvement in spinal metastases and determine the frequency with which patients can be considered candidates for radical surgery (en bloc spondylectomy). Methods: Consecutive patients were classified accordingly to Enneking’s and Tomita’s schemes for grading vertebral involvement of metastases. Results: Fifty-one (51) consecutive patients were evaluated. Eighty-three percent of patients presented with the involvement of multiple vertebral levels and/or spinal canal invasion. Conclusion: Because of diffuse vertebral involvement of metastases, no patients in this sample were considered to be candidates for radical spondylectomy of vertebral metastasis.

12

Gielis, Jan F., Gaëlle A. Boulet, Jacob J. Briedé, Tessa Horemans, Tom Debergh, Max Kussé, Paul Cos e Paul E. Y. Van Schil. "Longitudinal quantification of radical bursts during pulmonary ischaemia and reperfusion". European Journal of Cardio-Thoracic Surgery 48, n. 4 (5 gennaio 2015): 622–29. http://dx.doi.org/10.1093/ejcts/ezu518.

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Tannous, Joy H., e Arno de Klerk. "Quantification of the Free Radical Content of Oilsands Bitumen Fractions". Energy & Fuels 33, n. 8 (12 luglio 2019): 7083–93. http://dx.doi.org/10.1021/acs.energyfuels.9b01115.

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14

Zhang, Xianhui, Renwu Zhou, Kateryna Bazaka, Yan Liu, Rusen Zhou, Guangliang Chen, Zhong Chen, Qinghuo Liu, Size Yang e Kostya Ken Ostrikov. "Quantification of plasma produced OH radical density for water sterilization". Plasma Processes and Polymers 15, n. 6 (30 aprile 2018): 1700241. http://dx.doi.org/10.1002/ppap.201700241.

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15

Cassin, Savannah R., Sean Flynn, Pierre Chambon e Steve P. Rannard. "Quantification of branching within high molecular weight polymers with polyester backbones formed by transfer-dominated branching radical telomerisation (TBRT)". RSC Advances 11, n. 39 (2021): 24374–80. http://dx.doi.org/10.1039/d1ra03886a.

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The characterisation and quantification of branching is key to understanding new complex macromolecules. Here we establish approaches to evaluate the unique and novel architectures formed by Transfer-dominated Branching Radical Telomerisation (TBRT).

16

Tanev, Mihail, Georgi Tomov e Yordanka Karakirova. "EPR Spectroscopy Investigation of Oxygen Radical Production by Methylene Blue and Indocyanine Green in Aqueous Solutions under Laser Irradiation in the Context of Antibacterial Photodynamic Therapy". Folia Medica 63, n. 3 (30 giugno 2021): 372–76. http://dx.doi.org/10.3897/folmed.63.e52102.

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Introduction: Antibacterial photodynamic therapy is a promising treatment modality in the anti-infective therapy of numerous oral diseases. It involves photo activation of a reactive substance (dye), thus releasing reactive oxygen species (ROS-radicals) which are highly destructive to the bacterial cell. However, thorough investigation of radical production properties of different dyes is not common in literature.Aim: The aim of this study was to investigate and evaluate oxygen radical-producing potential of two commonly used photoactive dyes in the context of antibacterial photodynamic therapy.Materials and methods: The radical-producing properties of two commonly used dyes for photodynamic therapy in oral medicine, methylene blue and indocyanine green, irradiated under laser irradiation are investigated using electron paramagnetic resonance (EPR) spectroscopy. The detection of reactive oxygen species is performed with “spin-trapping” technique.Results: The selected photoactive dyes showed promising yields of reactive oxygen species (ROS) in aqueous solutions. The comparative analysis of the results deemed methylene blue as the more productive photoactive agent.Conclusions: By employing the spin-trapping technique, this study indicates EPR-spectroscopy as a promising method of relative quantification of reactive oxygen species released by the photodynamic reaction in aqueous solutions.

17

Agatonovic-Kustrin, Snezana, e David W. Morton. "Quantification of polyphenolic antioxidants and free radical scavengers in marine algae". Journal of Applied Phycology 30, n. 1 (26 aprile 2017): 113–20. http://dx.doi.org/10.1007/s10811-017-1139-x.

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18

Kozuleva, Marina, Irina Klenina, Ivan Mysin, Igor Kirilyuk, Vera Opanasenko, Ivan Proskuryakov e Boris Ivanov. "Quantification of superoxide radical production in thylakoid membrane using cyclic hydroxylamines". Free Radical Biology and Medicine 89 (dicembre 2015): 1014–23. http://dx.doi.org/10.1016/j.freeradbiomed.2015.08.016.

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19

Rostro, Lizbeth, Aditya G. Baradwaj e Bryan W. Boudouris. "Controlled Radical Polymerization and Quantification of Solid State Electrical Conductivities of Macromolecules Bearing Pendant Stable Radical Groups". ACS Applied Materials & Interfaces 5, n. 20 (3 ottobre 2013): 9896–901. http://dx.doi.org/10.1021/am403223s.

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20

Pugalenthi, M., M. Pradheeba, S. Vishnu Kumar, G. Vasukipriyadharshini, S. Swathi e G. Divya Bharathi. "UNVEILING THE PHYTOCHEMICAL PROFILE, SECONDARY METABOLITE QUANTIFICATION AND ANTIOXIDANT ACTIVITY OF CLEMATIS WIGHTIANA WALL. EX WIGHT and ARN." Journal of Advanced Scientific Research 13, n. 03 (30 aprile 2022): 70–77. http://dx.doi.org/10.55218/jasr.202213312.

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Traditionally, the leaves of Clematis wightiana have been used in the treatment of rheumatism, indigestion, headaches, varicose veins, bone problems, nasal congestion and sinus. The present study was conducted to evaluate the phytochemical profile, quantification of secondary metabolites and free radical scavenging capacity of C. wightiana leaf. The total phenolic, tannin and flavanoid content of C. wightiana leaves were quantified and were found to be higher in the ethyl acetate extract. Subsequently, the extracts were subjected to appraise their antioxidant capacity by availing various in vitro antioxidant assays namely DPPH radical scavenging assay, ABTS assay, Phosphomolybedenum assay, Ferric Reducing assay, Superoxide Radical Scavenging assay and Reducing power assay. The results of the antioxidant assays revealed that the ethyl acetate extract of C. wightiana leaves possess better free radical scavenging activity than other solvent extracts. Thus, the finding of the study elucidates the perception on phytochemical and bioactivity of C. wightiana which could be used in development of phytotherapeutics to enchance human health. Keywords: Clematis wightiana, Antioxidant, Superoxide radical scavenging, In vitro antioxidant assay, DPPH, Ethnomedicine.

21

Jackson, Malcolm J. "An overview of methods for assessment of free radical activity in biology". Proceedings of the Nutrition Society 58, n. 4 (novembre 1999): 1001–6. http://dx.doi.org/10.1017/s0029665199001317.

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Assays which purport to assess free radical activity in biological systems are multiple. However, despite numerous published descriptions of new methods and modifications of methods to assess free radical activity in biological materials, there is still a lack of reliable techniques for quantification of activity in vivo. Analysis of a number of related indicators and use of a variety of approaches appears the only reliable way to evaluate these processes in vivo. In studies of free radical generation by contracting skeletal muscle we have attempted to use a variety of indicators, including measurement of endogenous antioxidant levels, measurement of indirect indicators of free radical activity (e.g. products of lipid peroxidation, DNA oxidation or protein oxidation) and, where possible, measurement of direct indicators of free radical activity by electron spin resonance techniques. In view of the relative lack of specificity of many available techniques, caution should be exerted in evaluating the numerous examples of isolated single measures of free radical activity which are present in the scientific literature.

22

Hughes, H. M., I. M. George, J. C. Evans, C. C. Rowlands, G. M. Powell e C. G. Curtis. "The role of the liver in the production of free radicals during halothane anaesthesia in the rat. Quantification of N-tert-butyl-alpha-(4-nitrophenyl)nitrone (PBN)-trapped adducts in bile from halothane as compared with carbon tetrachloride". Biochemical Journal 277, n. 3 (1 agosto 1991): 795–800. http://dx.doi.org/10.1042/bj2770795.

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Halothane or CCl4 was co-administered with the spin trap N-tert-butyl-alpha-(4-nitrophenyl)nitrone (PBN) to rats fitted with bile duct cannuli or to isolated perfused liver preparations. Rats maintained under halothane anaesthesia generated significant amounts of free radicals, and 5-9 nmol was excreted in bile over 1 h. No adducts were detected in urine or plasma. The hepatic origin of these free radicals was confirmed by studies on isolated perfused livers where the addition of halothane to the perfusate resulted in the biliary elimination of the same PBN-trapped radical adducts. Similarly, following CCl4 administration, the same radical species were eliminated in bile in the whole animal and the perfused liver preparation. In the perfused liver, over 3 h the total biliary elimination of radicals derived from halothane or CCl4 (administered at equimolar concentrations) was approximately the same (5-7 nmol); however, the elimination of halothane-derived radicals was more rapid over the first 1 h.

23

Sushila Saini. "In vitro antioxidant activity and total phenolic content of Digera muricata leaves". World Journal of Biology Pharmacy and Health Sciences 14, n. 3 (30 giugno 2023): 105–12. http://dx.doi.org/10.30574/wjbphs.2023.14.3.0255.

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In the present study quantification of total phenolic content and evaluation of in vitro antioxidant capability of five different extracts of Digera muricata was carried out by different assays. DPPH radical, superoxide radical, hydroxyl radical scavenging activity and metal chelating activity were calculated and compared with standard antioxidants. Reducing power of the extract was also determined. All extracts showed good free radical scavenging ability which gets enhanced with increasing concentration. Methanolic extract possessed highest scavenging ability and it has maximum phenolic content (41.87 mg/g GAE). Significant correlation was observed between antioxidant assays and total phenolic content indicating that phenolics may be contributing towards antioxidant activity. The results conclude that D. muricata extracts are a potential source of natural antioxidants and could show promise as therapeutic agent in preventing the progression of oxidative stress related degenerative disorders.

24

Baradwaj, Aditya G., Lizbeth Rostro, Muhammad A. Alam e Bryan W. Boudouris. "Quantification of the solid-state charge mobility in a model radical polymer". Applied Physics Letters 104, n. 21 (26 maggio 2014): 213306. http://dx.doi.org/10.1063/1.4880118.

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Strother*, Marshall, Kristen Koepsell, Jennifer Faerber, Lihai Song, Joshua Bernard, Stanley Malkowicz, Thomas Guzzo e Gregory Tasian. "PD60-09 QUANTIFICATION OF 5- AND 30-DAY AMBULATION AFTER RADICAL CYSTECTOMY". Journal of Urology 203 (aprile 2020): e1277-e1278. http://dx.doi.org/10.1097/ju.0000000000000977.09.

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Lisdat, F., B. Ge, R. Reszka e E. Kozniewska. "An electrochemical method for quantification of the radical scavenging activity of SOD". Fresenius' Journal of Analytical Chemistry 365, n. 6 (8 novembre 1999): 494–98. http://dx.doi.org/10.1007/s002160051511.

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Cominos, M., M. A. Mosleh-Shirazi, D. Tait, A. Henrys e P. Cornes. "Quantification and reduction of cardiac dose in radical radiotherapy for oesophageal cancer". British Journal of Radiology 78, n. 936 (dicembre 2005): 1069–74. http://dx.doi.org/10.1259/bjr/20742408.

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28

Wang, Yun, Xuefei Lv, Yu Li, Guang Peng, Javed Iqbal e Yulin Deng. "Preparation of trypsin aptamer modified silica particles by surface initiated atom transfer radical polymerization for proteome identification". Analytical Methods 8, n. 21 (2016): 4277–84. http://dx.doi.org/10.1039/c5ay02080h.

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29

Faith Robert Owabhel e Abraham Sisein Eboh. "Antioxidant, chelating and HPLC quantification of phenols in extract of Phyllanthus niruri". World Journal of Advanced Pharmaceutical and Life Sciences 3, n. 1 (30 agosto 2022): 001–6. http://dx.doi.org/10.53346/wjapls.2022.3.1.0029.

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Phyllanthus niruriis a known medicinal plant. The leaves of Phyllanthus niruri were evaluated for antioxidant activity utilizing different methods and the quantification of phenols and flavonoid using HPLC (High Performance Liquid Chromatography). The leaves of Phyllanthus niruri were harvested, shade dried, grounded and extracted with methanol. The extract was subjected to total antioxidant capacity, DPPH radical scavenging, nitric oxide (NO) scavenging, ferrous chelation and HPLC quantification of phenolics and flavonoids. The result showed total antioxidant capacity of 13.04 ±0.08 mgAAE/g. The % scavenging of DPPH radical of gallic acid a standard antioxidant was slightly higher than Phyllanthus niruri at concentrations of 0.1 – 1 mg/ml. In the case of nitric oxide (NȮ), the scavenging ability of Phyllanthus niruri was higher than the standard antioxidant quercetin at 0.1 – 1 mg/ml. the chelating ability of Phyllanthus niruri and EDTA at the same concentrations of 0.1 – 1 mg/ml shown in table 3 shows that Phyllanthus niruri has about 70 % of the chelating ability of EDTA. Some important phenols and flavonoids detected in Phyllanthus niruri are P-coumaric acid, gallic acid, caffeic acid, kaempferol, ferulic, luteolin, quercetin amongst others. This investigation shows that extract of Phyllanthus niruri acts as an antioxidant due to the abundance of phenolics and flavonoids.

30

Norma, P. Melndez, Nevrez-Moorilln Virginia, Rodrguez-Herrera Ral, C. Espinoza Jos e N. Aguilar Cristbal. "A microassay for quantification of 2,2-diphenyl-1-picrylhydracyl (DPPH) free radical scavenging". African Journal of Biochemistry Research 8, n. 1 (31 gennaio 2014): 14–18. http://dx.doi.org/10.5897/ajbr2013.0669.

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Ichikawa, K., Y. H. Han, S. K. Han e H. Utsumi. "Quantification of hydroxyl radical generation with spin trapping ESR technique in batch system". Journal of Water and Environment Technology 1, n. 1 (2003): 43–48. http://dx.doi.org/10.2965/jwet.2003.43.

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32

Cho, Chulhee, Sijun Kim, Youngseok Lee, Wonnyoung Jeong, Inho Seong, Jangjae Lee, Minsu Choi et al. "Refined Appearance Potential Mass Spectrometry for High Precision Radical Density Quantification in Plasma". Sensors 22, n. 17 (31 agosto 2022): 6589. http://dx.doi.org/10.3390/s22176589.

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As the analysis of complicated reaction chemistry in bulk plasma has become more important, especially in plasma processing, quantifying radical density is now in focus. For this work, appearance potential mass spectrometry (APMS) is widely used; however, the original APMS can produce large errors depending on the fitting process, as the fitting range is not exactly defined. In this research, to reduce errors resulting from the fitting process of the original method, a new APMS approach that eliminates the fitting process is suggested. Comparing the neutral densities in He plasma between the conventional method and the new method, along with the real neutral density obtained using the ideal gas equation, confirmed that the proposed quantification approach can provide more accurate results. This research will contribute to improving the precision of plasma diagnosis and help elucidate the plasma etching process.

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Zigah, Dodzi, Joaquín Rodríguez-López e Allen J. Bard. "Quantification of photoelectrogenerated hydroxyl radical on TiO2 by surface interrogation scanning electrochemical microscopy". Physical Chemistry Chemical Physics 14, n. 37 (2012): 12764. http://dx.doi.org/10.1039/c2cp40907k.

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Lankone, Ronald S., Alyssa R. Deline, Michael Barclay e D. Howard Fairbrother. "UV–Vis quantification of hydroxyl radical concentration and dose using principal component analysis". Talanta 218 (ottobre 2020): 121148. http://dx.doi.org/10.1016/j.talanta.2020.121148.

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Nagarajan, Sanjay, Nathan C. Skillen, Federica Fina, Guan Zhang, Chamnan Randorn, Linda A. Lawton, John T. S. Irvine e Peter K. J. Robertson. "Comparative assessment of visible light and UV active photocatalysts by hydroxyl radical quantification". Journal of Photochemistry and Photobiology A: Chemistry 334 (febbraio 2017): 13–19. http://dx.doi.org/10.1016/j.jphotochem.2016.10.034.

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Podbevšek, Darjan, Damien Colombet, Frederic Ayela e Gilles Ledoux. "Localization and quantification of radical production in cavitating flows with luminol chemiluminescent reactions". Ultrasonics Sonochemistry 71 (marzo 2021): 105370. http://dx.doi.org/10.1016/j.ultsonch.2020.105370.

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Li, Xiaoyan, Zixuan Li, Boer Xie e Joshua S. Sharp. "Supercharging by m-NBA Improves ETD-Based Quantification of Hydroxyl Radical Protein Footprinting". Journal of The American Society for Mass Spectrometry 26, n. 8 (28 aprile 2015): 1424–27. http://dx.doi.org/10.1007/s13361-015-1129-7.

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RHEMREV, JOHANN P. T., FLORIS W. P. C. VAN OVERVELD, GUIDO R. M. M. HAENEN, TOM TEERLINK, AALT BAST e JAN P. W. VERMEIDEN. "Quantification of the Nonenzymatic Fast and Slow TRAP in a Postaddition Assay in Human Seminal Plasma and the Antioxidant Contributions of Various Seminal Compounds". Journal of Andrology 21, n. 6 (12 novembre 2000): 913–20. http://dx.doi.org/10.1002/j.1939-4640.2000.tb03422.x.

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ABSTRACT: Total radical‐trapping antioxidant potential (TRAP) measurements of human seminal plasma (N = 25) were performed by using a post‐addition assay based on trapping 2,2′ Azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) (ABTS) radicals. This method enables the antioxidant capacity of human seminal plasma and its constituents to be quantified. The standard procedure consisted of determination of the Trolox equivalent antioxidant capacity (TEAC) after incubating the test sample in the ABTS radical solution for 10 seconds (fast TRAP) and 300 s (total TRAP). Interestingly, seminal plasma showed a fast TRAP and a high slow TRAP (Total TRAP ‐ Fast TRAP). The final total TRAP of seminal plasma is about 10 times higher than that of blood plasma. Various components of seminal plasma contribute to its fast TRAP; 37% can be attributed to vitamin C, uric acid, and tyrosine; proteins and polyphenolic compounds contribute a further 57%. In contrast, the slow TRAP was attributed to vitamin C (1%), uric acid (2%), and tyrosine (15%) and to proteins and polyphenolic compounds (33%). It was not possible to account for the remaining 49%. Neither known putative antioxidants, such as spermine, pyruvate, and taurine, nor other seminal compounds, such as carnitine, sialic acid, fructose, spermidine, glycerophosphorylcholine, and hyaluronic acid, contributed to any significant radical‐trapping activity at a standard concentration of 1 mM. Of the amino acids, only tyrosine possessed a slow TRAP, and it is present at a high concentration in seminal plasma. Glutathione and hypotaurine show high fast and slow TRAPs, respectively. However, because of their low concentration in seminal plasma, their contribution to the TRAP is negligible. In conclusion, seminal plasma possesses a high antioxidant buffer capacity that protects spermatozoa from oxidative stress. Moreover, these findings suggest that the fast and slow TRAPs may have an important role as infertility markers and treatment targets in future antioxidant therapies.

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Wilson, David H., David W. Hanlon, Gail K. Provuncher, Lei Chang, Linan Song, Purvish P. Patel, Evan P. Ferrell et al. "Fifth-Generation Digital Immunoassay for Prostate-Specific Antigen by Single Molecule Array Technology". Clinical Chemistry 57, n. 12 (1 dicembre 2011): 1712–21. http://dx.doi.org/10.1373/clinchem.2011.169540.

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BACKGROUND Measurement of prostate-specific antigen (PSA) in prostate cancer patients following radical prostatectomy (RP) has been hindered by the limit of quantification of available assays. Because radical prostatectomy removes the tissue responsible for PSA production, postsurgical PSA is typically undetectable with current assay methods. Evidence suggests, however, that more sensitive determination of PSA status following RP could improve assessment of patient prognosis and response to treatment and better target secondary therapy for those who may benefit most. We developed an investigational digital immunoassay with a limit of quantification 2 logs lower than current ultrasensitive third-generation PSA assays. METHODS We developed reagents for a bead-based ELISA for use with high-density arrays of femtoliter-volume wells. Anti-PSA capture beads with immunocomplexes and associated enzyme labels were singulated within the wells of the arrays and interrogated for the presence of enzymatic product. We characterized analytical performance, compared its accuracy with a commercially available test, and analyzed longitudinal serum samples from a pilot study of 33 RP patients. RESULTS The assay exhibited a functional sensitivity (20% interassay CV) <0.05 pg/mL, total imprecision <10% from 1 to 50 pg/mL, and excellent agreement with the comparator method. All RP samples were well within the assay measurement capability. PSA concentrations following surgery were found to be predictive of prostate cancer recurrence risk over 5 years. CONCLUSIONS The robust 2-log improvement in limit of quantification relative to current ultrasensitive assays and the validated analytical performance of the assay allow for accurate assessment of PSA status after RP.

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Fuchs, Hendrik, Sascha Albrecht, Ismail–Hakki Acir, Birger Bohn, Martin Breitenlechner, Hans-Peter Dorn, Georgios I. Gkatzelis et al. "Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR". Atmospheric Chemistry and Physics 18, n. 11 (7 giugno 2018): 8001–16. http://dx.doi.org/10.5194/acp-18-8001-2018.

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Abstract. The photooxidation of methyl vinyl ketone (MVK) was investigated in the atmospheric simulation chamber SAPHIR for conditions at which organic peroxy radicals (RO2) mainly reacted with NO (“high NO” case) and for conditions at which other reaction channels could compete (“low NO” case). Measurements of trace gas concentrations were compared to calculated concentration time series applying the Master Chemical Mechanism (MCM version 3.3.1). Product yields of methylglyoxal and glycolaldehyde were determined from measurements. For the high NO case, the methylglyoxal yield was (19 ± 3) % and the glycolaldehyde yield was (65 ± 14) %, consistent with recent literature studies. For the low NO case, the methylglyoxal yield reduced to (5 ± 2) % because other RO2 reaction channels that do not form methylglyoxal became important. Consistent with literature data, the glycolaldehyde yield of (37 ± 9) % determined in the experiment was not reduced as much as implemented in the MCM, suggesting additional reaction channels producing glycolaldehyde. At the same time, direct quantification of OH radicals in the experiments shows the need for an enhanced OH radical production at low NO conditions similar to previous studies investigating the oxidation of the parent VOC isoprene and methacrolein, the second major oxidation product of isoprene. For MVK the model–measurement discrepancy was up to a factor of 2. Product yields and OH observations were consistent with assumptions of additional RO2 plus HO2 reaction channels as proposed in literature for the major RO2 species formed from the reaction of MVK with OH. However, this study shows that also HO2 radical concentrations are underestimated by the model, suggesting that additional OH is not directly produced from RO2 radical reactions, but indirectly via increased HO2. Quantum chemical calculations show that HO2 could be produced from a fast 1,4-H shift of the second most important MVK derived RO2 species (reaction rate constant 0.003 s−1). However, additional HO2 from this reaction was not sufficiently large to bring modelled HO2 radical concentrations into agreement with measurements due to the small yield of this RO2 species. An additional reaction channel of the major RO2 species with a reaction rate constant of (0.006 ± 0.004) s−1 would be required that produces concurrently HO2 radicals and glycolaldehyde to achieve model–measurement agreement. A unimolecular reaction similar to the 1,5-H shift reaction that was proposed in literature for RO2 radicals from MVK would not explain product yields for conditions of experiments in this study. A set of H-migration reactions for the main RO2 radicals were investigated by quantum chemical and theoretical kinetic methodologies, but did not reveal a contributing route to HO2 radicals or glycolaldehyde.

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Taha, Youssef M., Matthew T. Saowapon, Faisal V. Assad, Connie Z. Ye, Xining Chen, Natasha M. Garner e Hans D. Osthoff. "Quantification of peroxynitric acid and peroxyacyl nitrates using an ethane-based thermal dissociation peroxy radical chemical amplification cavity ring-down spectrometer". Atmospheric Measurement Techniques 11, n. 7 (17 luglio 2018): 4109–27. http://dx.doi.org/10.5194/amt-11-4109-2018.

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Abstract. Peroxy and peroxyacyl nitrates (PNs and PANs) are important trace gas constituents of the troposphere which are challenging to quantify by differential thermal dissociation with NO2 detection in polluted (i.e., high-NOx) environments. In this paper, a thermal dissociation peroxy radical chemical amplification cavity ring-down spectrometer (TD-PERCA-CRDS) for sensitive and selective quantification of total peroxynitrates (ΣPN = ΣRO2NO2) and of total peroxyacyl nitrates (ΣPAN = ΣRC(O)O2NO2) is described. The instrument features multiple detection channels to monitor the NO2 background and the ROx ( = HO2 + RO2 + ΣRO2) radicals generated by TD of ΣPN and/or ΣPAN. Chemical amplification is achieved through the addition of 0.6 ppm NO and 1.6 % C2H6 to the inlet. The instrument's performance was evaluated using peroxynitric acid (PNA) and peroxyacetic or peroxypropionic nitric anhydride (PAN or PPN) as representative examples of ΣPN and ΣPAN, respectively, whose abundances were verified by iodide chemical ionization mass spectrometry (CIMS). The amplification factor or chain length increases with temperature up to 69 ± 5 and decreases with analyte concentration and relative humidity (RH). At inlet temperatures above 120 and 250 °C, respectively, PNA and ΣPAN fully dissociated, though their TD profiles partially overlap. Furthermore, interference from ozone (O3) was observed at temperatures above 150 °C, rationalized by its partial dissociation to O atoms which react with C2H6 to form C2H5 and OH radicals. Quantification of PNA and ΣPAN in laboratory-generated mixtures containing O3 was achieved by simultaneously monitoring the TD-PERCA responses in multiple parallel CRDS channels set to different temperatures in the 60 to 130 °C range. The (1 s, 2σ) limit of detection (LOD) of TD-PERCA-CRDS is 6.8 pptv for PNA and 2.6 pptv for ΣPAN and significantly lower than TD-CRDS without chemical amplification. The feasibility of TD-PERCA-CRDS for ambient air measurements is discussed.

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DYKENS, JAMES A., J. MALCOLM SHICK, CRAIG BENOIT, GARRY R. BUETTNER e GARY W. WINSTON. "Oxygen Radical Production in the Sea Anemone Anthopleura Elegantissima and its Endosymbiotic Algae". Journal of Experimental Biology 168, n. 1 (1 luglio 1992): 219–41. http://dx.doi.org/10.1242/jeb.168.1.219.

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Host animals in algal-invertebrate endosymbiotic associations are exposed to photosynthetically generated hyperoxia while in sunlight, conditions conducive to photodynamic excitations and production of cytotoxic oxygen-derived radicals such as the superoxide anion (O2−) and the hydroxyl radical (OH). All previous vidence of oxyradical production in symbiotic associations has been circumstantial. We here present direct evidence, from electron paramagnetic resonance studies on tissue homogenates of the photosymbiont-containing sea anemone Anthopleura elegantissima (Brandt), of substantial light-dependent OH and O2 production that is abolished by dichlorophenyldimethylurea (DCMU), an inhibitor of photosynthesis. Shade-adapted A. elegantissima lacking endosymbiotic algae likewise show OH production upon illumination. The latter flux is not dependent on photosynthesis, and DCMU has no effect. Rather, OH production in apozooxanthellate anemones is via direct photoexcitations. The selective reaction of dimethyl sulfoxide (DMSO) with OH to form methane sulfinic acid allows quantification of OH produced in vivo. Such in vivo measurements confirm the production of OH in both host and algae in illuminated zooxanthellate anemones, where the amount of OH in the zooxanthellae is disproportionately large relative to their fractional contribution to the biomass of the symbiosis. In vivo studies using DMSO also suggest a photochemical production of OH in apozooxanthellate anemones exposed to simulated sunlight enriched in ultraviolet (UV) wavelengths, and the enhancement by UV light of OH production in zooxanthellate individuals. Such chronic radical exposure necessitates defenses

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McDermed, Jonathan E., Ron Sanders, Stephen Fait, Robert E. Klem, Mark J. Sarno, Thomas H. Adams e Eleftherios P. Diamandis. "Nucleic Acid Detection Immunoassay for Prostate-Specific Antigen Based on Immuno-PCR Methodology". Clinical Chemistry 58, n. 4 (1 aprile 2012): 732–40. http://dx.doi.org/10.1373/clinchem.2011.170290.

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Abstract BACKGROUND Serum prostate-specific antigen (PSA) concentrations after radical prostatectomy typically become undetectable with the use of current immunometric assay methods. Despite modern surgical techniques, 15%–30% of prostate cancer patients undergoing radical prostatectomy develop a biochemical recurrence during follow-up. Unfortunately, poor analytical sensitivity of standard PSA assays delays biochemical recurrence detection, and because of day-to-day assay imprecision ultrasensitive PSA assays cannot assess PSA kinetics. We developed an immuno-PCR assay for total PSA that has a limit of quantification >10 times lower than current ultrasensitive assays. METHODS The 2-site immunometric assay for total PSA employed 2 monoclonal antibodies, one conjugated to a double-stranded DNA label and the other bound to paramagnetic microparticles. After several washing steps, quantification cycles were determined and values were converted to PSA concentrations. We characterized analytical performance and compared accuracy with a commercially available total PSA assay. RESULTS The limit of quantification was 0.65 ng/L and the assay was linear in the range of 0.25–152.0 ng/L. Total imprecision estimates at PSA concentrations of 3.8, 24.1, and 69.1 ng/L were <15.2%, <9.4%, and <10.6%, respectively. Recovery of supplemented PSA ranged from 87.5% to 119.2% (mean 100.3%). Dilution recovery ranged from 96.4% to 115.3% (mean 102.3%). There was no high-dose hook effect up to 50 000 ng/L of PSA. Comparison with the commercial PSA assay showed a regression slope of 1.06 and a correlation coefficient of 0.996. CONCLUSIONS The analytical characteristics of the assay support the use of this assay for the accurate and precise measurement of serum PSA, even at sub–nanogram-per-liter concentrations.

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Sumi, Salma Akter, Md Afjalus Siraj, Amir Hossain, Md Sagir Mia, Seagufta Afrin e Md Mustafizur Rahman. "Investigation of the Key Pharmacological Activities of Ficus racemosa and Analysis of Its Major Bioactive Polyphenols by HPLC-DAD". Evidence-Based Complementary and Alternative Medicine 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/3874516.

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Objective. Oxidative stress leads to numerous physiological disorders including infectious diseases, inflammation, and cancer. The present study was carried out to investigate antioxidant, antibacterial, and cytotoxic activity of methanol crude extract of leaves and fruits of the Ficus racemosa (LCME and FCME, resp.) and to analyse its major bioactive polyphenols by HPLC-DAD. Methods. Antioxidant capacity of the extracts was evaluated by DPPH free radical scavenging, reducing power, total phenolic, total flavonoid, total tannin content assay, superoxide radical, hydroxyl radical, and hydrogen peroxide scavenging assay. Identification and quantification of bioactive polyphenols were done by HPLC-DAD method. Antibacterial activity was tested by “disc diffusion” method. Brine shrimp lethality assay was carried out to check the cytotoxic potential. Result. Both LCME and FCME showed DPPH scavenging ability and concentration dependent reducing power activity. They had phenolic content, flavonoid content, and tannin content. Both the extracts showed superoxide radical scavenging ability, hydroxyl radical scavenging ability, and hydrogen peroxide scavenging ability. HPLC analysis of LCME and FCME indicated the presence of significant amount of gallic acid along with other phenolic constituents. Conclusion. Significant amount of gallic acid along with other phenolic constituents might have played an important role in the observed antioxidant, antibacterial, and cytotoxic activity.

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Konstantinou, Dimitris, Adamantios Mavrakis, Konstantinos Grintzalis, Ioannis Papapostolou, Stelios F. Assimakopoulos, Elisabeth Chroni e Christos Georgiou. "Quantification of Superoxide Radical in the Brain of Rats with Experimentally Induced Obstructive Jaundice". Neurochemical Research 33, n. 6 (20 dicembre 2007): 1101–5. http://dx.doi.org/10.1007/s11064-007-9556-x.

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Georgiou, Christos D., Ioannis Papapostolou, Nikolaos Patsoukis, Theodore Tsegenidis e Theodore Sideris. "An ultrasensitive fluorescent assay for the in vivo quantification of superoxide radical in organisms". Analytical Biochemistry 347, n. 1 (dicembre 2005): 144–51. http://dx.doi.org/10.1016/j.ab.2005.09.013.

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Wu, Shulin, Ling Xie, Sharron X. Lin, Gregory J. Wirth, Min Lu, Yifen Zhang, Michael L. Blute, Douglas M. Dahl e Chin-Lee Wu. "Quantification of perineural invasion focus after radical prostatectomy could improve predictive power of recurrence". Human Pathology 104 (ottobre 2020): 96–104. http://dx.doi.org/10.1016/j.humpath.2020.07.005.

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Remy, K. Bationo, M. Dabire Constantin, Abdoulaye Yougoubo, Kabore Boukare, Sawadogo Ousseni, Koala Moumouni, Pale Eloi e H. Ch Nebie Roger. "Major anthocyanin quantification, free radical scavenging properties and structural identification in Cymbopogon giganteus extracts". African Journal of Pure and Applied Chemistry 17, n. 3 (31 agosto 2023): 32–46. http://dx.doi.org/10.5897/ajpac2023.0902.

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Saini, Anuradha, Parmjit Singh Panesar e Manab Bandhu Bera. "Comparative Study on the Extraction and Quantification of Polyphenols from Citrus Peels Using Maceration and Ultrasonic Technique". Current Research in Nutrition and Food Science Journal 7, n. 3 (1 ottobre 2019): 678–85. http://dx.doi.org/10.12944/crnfsj.7.3.08.

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Citrus processing industry generates the large amount of byproducts, which are rich in polyphenols that have high antioxidant properties. These polyphenols can be extracted and utilized in different applications. In present investigation, comparative study was undertaken using maceration (M) and ultrasound assisted extraction (UAE) for the efficient extraction of polyphenols from citrus peels of different cultivars such as ‘kinnow mandarin’ (Citrus reticulata) and ‘mousambi’ (Citrus limetta). The total phenols (28.30 mg/GAE g dw), flavonoids (4.40 mg/CE g dw) and DPPH radical scavenging activity (48.23%) were attained from kinnow mandarin peels whereas total phenols (21.99 mg/GAE g dw), flavonoids (2.07 mg/CE g dw) and DPPH radical scavenging activity (39.73%) were obtained from mousambi peels using UAE method. Therefore, the results indicated the efficiency of UAE method as compared to maceration technique for the extraction of polyphenols in terms of high yield and their antioxidant properties.

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Mitra, Indrani, Achintya Saha e Kunal Roy. "Quantification of contributions of different molecular fragments for antioxidant activity of coumarin derivatives based on QSAR analyses". Canadian Journal of Chemistry 91, n. 6 (giugno 2013): 428–41. http://dx.doi.org/10.1139/cjc-2012-0527.

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Attempts have been made in the present work using in silico techniques for identification of essential structural features imparting antioxidant potential to naturally available coumarin molecules and their synthetic derivatives. Four different types of modeling tools have been employed for the qualitative and quantitative assessment of the molecular fragments constituting the biological pharmacophore. The descriptor-based quantitative structure–activity relationship (QSAR) and group-based QSAR (G-QSAR) models provide a quantitative estimation of the substituent requirements and the chemical nature of the parent moiety. Subsequently, 3D pharmacophore and hologram QSAR (HQSAR) models enable identification of the key molecular components necessary for the antioxidant potency to the molecules. All of the different models infer the importance of the hydrogen bond acceptor ketonic fragment for interaction of the antioxidant molecules with the neighbouring toxic radicals. Additionally, the phenyl substituent attached to the side chain and the benzene nucleus of the benzopyran moiety also constitute the response pharmacophore for the molecules under study. The models thus developed may serve as an essential query tool for screening of databases for selection of molecules bearing the essential fragments and subsequent prediction of their free radical scavenging potency.