Journal articles: 'Equation stern volmer'

1

Yekta, Ahmad, Zahra Masoumi, and Mitchell A. Winnik. "Luminescence measurements of oxygen permeation and oxygen diffusion in thin polymer films." Canadian Journal of Chemistry 73, no. 11 (November 1, 1995): 2021–29. http://dx.doi.org/10.1139/v95-250.

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A new method is developed for analyzing the diffusion of oxygen in thin polymer films via fluorescence quenching measurements. We begin by reviewing previous methods, all of which involve approximations, for the measurement of permeability and diffusion coefficient by luminescence quenching; their shortcomings are clarified. An exact analytic theory is developed that successfully couples Fick's laws of diffusion to the Stern–Volmer equation of intensity quenching. Various modes of experimentation with polymeric films are considered. The equations we derive make the unexpected prediction that the rate of emission intensity decay when O2 diffuses into a polymer film is much faster than the rate of emission intensity enhancement when O2 diffuses out of the same film, even when the molecular diffusivity remains unchanged. Experiments show that this is indeed the observed behaviour. Keywords: diffusion coefficient, oxygen permeability, polymers, quenching, luminescence quenching, Fick's laws. Stern–Volmer equation.

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Htun, Than. "A Negative Deviation from Stern–Volmer Equation in Fluorescence Quenching." Journal of Fluorescence 14, no. 2 (March 2004): 217–22. http://dx.doi.org/10.1023/b:jofl.0000016294.96775.fd.

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Qu, Binhong, Zhiyuan Mu, Yang Liu, Yingsha Liu, Rui Yan, Jianhui Sun, Zishu Zhang, Peng Li, and Liqiang Jing. "The synthesis of porous ultrathin graphitic carbon nitride for the ultrasensitive fluorescence detection of 2,4,6-trinitrophenol in environmental water." Environmental Science: Nano 7, no. 1 (2020): 262–71. http://dx.doi.org/10.1039/c9en01165j.

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The porous ultrathin g-C₃N₄ nanosheets with strong adsorption capacity have been synthesized for the ultrasensitive fluorescence detection of 2,4,6-trinitrophenol in water by the frequently neglected double-logarithmic Stern–Volmer equation.

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Ogunsipe, Abimbola, and Tebello Nyokong. "Effects of central metal on the photophysical and photochemical properties of non-transition metal sulfophthalocyanine." Journal of Porphyrins and Phthalocyanines 09, no. 02 (February 2005): 121–29. http://dx.doi.org/10.1142/s1088424605000186.

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The photophysical and photochemical properties and quenching (by 1,4-benzoquinone) of metallophthalocyanine sulfonates of aluminium ( AlPcSmix), zinc ( ZnPcSmix), silicon ( SiPcSmix), germanium ( GePcSmix) and tin ( SnPcSmix) are presented. The quantum yield values of fluorescence (ΦF), triplet state (ΦT), singlet oxygen (ΦΔ) and photodegradation (Φd) were determined and the observed trends in their variation among the complexes discussed in terms of aggregation and the heavy atom effect. 1,4-benzoquinone effectively quenched the fluorescence of the complexes. Quenching analyses gave positive deviations from Stern-Volmer behavior, suggesting the existence of static quenching in addition to dynamic quenching. The static and dynamic components of the quenching were separated using a modified Stern-Volmer equation and the “sphere of action quenching model”. The quenching constant was found to be a function of the radius of the central metal ion.

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Chen, Jingrun, Jason D. A. Lin, and Thuc-Quyen Nguyen. "Towards a Unified Macroscopic Description of Exciton Diffusion in Organic Semiconductors." Communications in Computational Physics 20, no. 3 (August 31, 2016): 754–72. http://dx.doi.org/10.4208/cicp.050615.010216a.

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AbstractWe study the exciton diffusion in organic semiconductors from a macroscopic viewpoint. In a unified way, we conduct the equivalence analysis between Monte-Carlo method and diffusion equation model for photoluminescence quenching and photocurrent spectrum measurements, in both the presence and the absence of Förster energy transfer effect. Connections of these two models to Stern-Volmer method and exciton-exciton annihilation method are also specified for the photoluminescence quenching measurement.

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Wiczk, Wiesław M., and Tadeusz Latowski. "Photophysical and Photochemical Studies of Polycyclic Aromatic Hydrocarbons in Solutions Containing Tetrachloromethane II. The Solvent Effect on the Fluorescence Quenching of Aromatic Hydrocarbons by Tetrachloromethane." Zeitschrift für Naturforschung A 42, no. 11 (November 1, 1987): 1290–95. http://dx.doi.org/10.1515/zna-1987-1111.

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Fluorescence quenching of aromatic hydrocarbons in a large concentration range of the quencher has been studied in a variety of two-component mixtures of tetrachloromethane with other solvents. In aliphatic solvents the process could be described by the Stern-Volmer equation, whereas in the remaining mixtures the fluorescence quenching curves showed a parabolic behaviour which has been explained in terms of specific interactions between the components of the mixtures.

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Amézqueta, Susana, Anna Bolioli Maria Bolioli, José Luis Beltrán, and Clara Ràfols. "Evaluation of the interactions between human serum albumin (HSA) and warfarin or diflunisal by using molecular fluorescence using two approaches." ADMET and DMPK 6, no. 1 (March 25, 2018): 47. http://dx.doi.org/10.5599/admet.6.1.473.

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<p class="PaperH1">Serum albumin is the main drug transporter of the bloodstream and contains two main binding sites: Sudlow I or acidic drug binding site, and Sudlow II or benzodiazepine binding site. Warfarin, a well-known anticoagulant drug commonly used in the prevention of thrombosis and thromboembolism, binds to Sudlow I site, whereas non-steroidal antiinflammatory drugs (NSAIDs) such as diflunisal bind preferentially to Sudlow II site. Albumin is a fluorophore that modifies its fluorescence (quenching or enhancement effect) when it is bound to a drug. The application of the double logarithm Stern-Volmer equation allows the calculation of the stoichiometry and the binding constant of the process. This procedure does not consider the possible interferences coming from the fluorescence of the drug though. Another strategy to evaluate the binding constants is to consider the whole spectrum, taking into account all the possible species in equilibrium; in this case we have used an extended version of the STAR program, which can deal with 300 spectra, each containing up to 300 data points. The aim of this work is to compare both approaches to evaluate the interaction between warfarin (Sudlow I) and diflunisal (Sudlow II) and HSA: the double logarithm Stern-Volmer equation and the STAR program.</p>

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Wang, Junsheng, Yongxin Song, Sun Jinyang, Xudong Wu, Yeqing Sun, Xinxiang Pan, and Dongqing Li. "Miniature fluorescent sensor for chloride ion concentration determination based on modified Stern–Volmer Equation." Measurement 46, no. 10 (December 2013): 3982–87. http://dx.doi.org/10.1016/j.measurement.2013.07.020.

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Friedl, Felix, Nils Krah, and Bernd Jähne. "Optical sensing of oxygen using a modified Stern–Volmer equation for high laser irradiance." Sensors and Actuators B: Chemical 206 (January 2015): 336–42. http://dx.doi.org/10.1016/j.snb.2014.09.073.

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10

Manjushree, M., and Hosakere D. Revanasiddappa. "A Diversified Spectrometric and Molecular Docking Technique to Biophysical Study of Interaction between Bovine Serum Albumin and Sodium Salt of Risedronic Acid, a Bisphosphonate for Skeletal Disorders." Bioinorganic Chemistry and Applications 2018 (June 28, 2018): 1–13. http://dx.doi.org/10.1155/2018/6954951.

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The binding interaction between bovine serum albumin (BSA) and sodium salt of risedronic acid (RSN) was studied by using the FT-IR (Fourier transform infrared), UV-Vis (ultraviolet–visible), fluorescence (emission and synchronous), CD (circular dichroism) spectrometric, and computational (molecular docking) techniques at 289, 297, and 305 K temperatures with physiological buffer of pH 7.40. The conformational and secondary structural changes observed for BSA from CD spectra and by curve fitting procedure were applied to Fourier self-deconvolution in FT-IR spectra. The formation of a BSA-RSN complex was confirmed from UV-Vis spectroscopy. The static type of quenching shown for RSN to BSA was verified from Stern–Volmer and modified Stern–Volmer equations. The binding constant of order 105 was obtained to be confirming that there exists a strong binding interaction between BSA and RSN. Synchronous fluorescence shows that the microenvironment of tryptophan was altered, not tyrosine of BSA; in addition to this, the distance between tryptophan of BSA and RSN was found out from Forster’s theory of nonradiation energy transfer. The interaction between BSA and RSN mainly occurred as a result of hydrogen bonds and van der Waals forces, the process is exothermic and spontaneous, and it was achieved through van ’t Hoff equation. This interaction was affected by the presence of biologically active Fe2+, Ni2+, Ca2+, Mg2+, and Cd2+ ions and was also studied. The subdomain IIIA of BSA involved with RSN interaction was authenticated from molecular docking analysis.

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Boguta, Patrycja, and Zofia Sokołowska. "Zinc Binding to Fulvic acids: Assessing the Impact of pH, Metal Concentrations and Chemical Properties of Fulvic Acids on the Mechanism and Stability of Formed Soluble Complexes." Molecules 25, no. 6 (March 12, 2020): 1297. http://dx.doi.org/10.3390/molecules25061297.

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The aim of the study was defined as a complementary analysis of molecular interactions between zinc (Zn) and fulvic acids (FAs) at a broad pH range (3–7), different metal concentrations (0–50 mg dm−3) and chemical properties of FAs and their impact on the Zn binding mechanism, stability, and efficiency. The results showed that the complexation reaction prevailed at pH 6 and 7, whereas protons exchange dominated interactions at pH 3. Stability constant of the complexes increased along with pH (logK increased from ~3.8 to 4.2). Complexation was preferred by less-humidified structures of lower molecular mass containing more oxygen groups. The number of fluorophores available for Zn(II) increased from pH 3 to 7 by ~44%. Depending on the pH, complexation involved a bidentate chelate, monodentate and bidentate bridging mode. Zn(II) binding was insufficiently modeled by the classic Stern–Volmer equation and well described by the double logarithmic equation (R > 0.94) as well as by a modified Stern–Volmer formula assuming the existence of available and unavailable fluorophore populations (R > 0.98). The fluorescence ratio of different fluorophores was proposed as an indicator of the binding affinity of various structures. A positive relationship was found between the fraction of accessible fluorophores and Zn(II) binding at pH 7 determined based on proton release (R = 0.91–0.97). The obtained results can find application in controlling the mobility and bioavailability of Zn in different conditions.

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Khan, Md Rasal Hossain, Asma Rahman, Md Zakir Sultan, Md Zamil Sultan, and Mohammad A. Rashid. "Fluorescence Spectroscopic Studies of in vitro Interactions of Famotidine and Tapentadol Hydrochloride with Bovine Serum Albumin." Dhaka University Journal of Pharmaceutical Sciences 15, no. 1 (August 8, 2016): 21–26. http://dx.doi.org/10.3329/dujps.v15i1.29187.

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The in vitro interactions of Famotidine (FT) and Tapentadol hydrochloride (TAP) with bovine serum albumin (BSA) have been studied by fluorescence emission spectroscopy under different conditions. Quenching constants were determined using the Stern-Volmer equation. Two moles FT bound with 1 mole of BSA at 298 K and 3 mole FT bound with 1 mole of BSA at 308 K in presence of TAP. BSA was used for the study as it shows approximately 76% sequence homology to human serum albumin (HSA).Dhaka Univ. J. Pharm. Sci. 15(1): 21-26, 2016 (June)

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Chu, Feng Hong, Lei Ye, Jian Qiang Zhang, Ben Shang Yang, Mian Zhao, Deng Zheng Huang, and Si Hua Zhen. "Study of TNT Sensor Based on Fluorescence Quenching of Conjugated Polymer MEH-PPV." Applied Mechanics and Materials 58-60 (June 2011): 2688–92. http://dx.doi.org/10.4028/www.scientific.net/amm.58-60.2688.

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A nitro aromatic explosives sensor based on fluorescence quenching was studied in this paper. U-shaped plastic optical fiber was used as sensor head and light emitting conjugated polymer MEH-PPV as fluorescence indictor. The light source was modulated sinusoidal to eliminate the external light disturbance. TNT quenching characteristics of fluorescence intensity were measured; When TNT concentration was lower than 10mg/ml, the relationship between fluorescence intensity and TNT concentration was linearly, when TNT concentration was higher than 10mg/100ml the obtained characteristics showed deviation from linear relation described by Stern-Volmer equation.

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14

Hao, Zhi Feng, Can Huang Yu, Shao Bing Yang, Jia Hao Tan, and Jian Yu. "Study on the Interaction between Gadolinium(III) Aminopolycarboxlicacid Complex and Bovine Serum Album by Spectroscopic Methods." Advanced Materials Research 912-914 (April 2014): 346–51. http://dx.doi.org/10.4028/www.scientific.net/amr.912-914.346.

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A novel gadolinium diethylenetriamine-N, N-bis (2-acetamide benzoic acid)-N, N-bisacetic acid complex has been synthesized and characterized by elemental analysis, infrared spectrum, ultraviolet spectroscopy and thermal analysis. The interaction between Gd3+and aminopolycarboxlicacid ligand was investigated by fluorescence titration. The binding constant of this complex is calculated to be 1.2018×104L·mol-1, and binding stoichiometry is 1:1. Fluorescence spectra was also used to study the interaction between Gd (III) complex and bovine serum album (BSA). The results showed that Gd (III) complex can effectively quench the intrinsic fluorescence of BSA via static quenching. According to Stern-Volmer equation and Linewerver-Burk equation, the binding constant is calculated to be 3.7491×104L·mol-1and binding site is about 1.0.

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Ding, Mei, Ying Jie Lei, Fang Xu, and Ou Yang Jie. "Study on the Interaction of Fluorescent Probe 2-(2'-Chloro Phenyl)-5-(2'-Hydroxyl Phenyl)1,3,4-Oxadiazole with DNA." Advanced Materials Research 284-286 (July 2011): 2392–96. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.2392.

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The interaction between self-synthesized fluorescent probe 2-(2'- Chloro phenyl)- 5- (2'- hydroxyl phenyl)1,3,4-oxadiazole (HOXD) and Calf thymus DNA was studied using UV absorption spectra and fluorescence quenching spectra．The data of fluorescence quenching of HOXD by DNA were analyzed according to Stern-Volmer equation and Lineweaver-Burk double-reciprocal equation．The results indicated that the fluorescence quenching of HOXD might be static one attributed to the formation of adduct from HOXD and DNA, which was confirmed by the data of temperature effect experiment. Further results presented in the paper showed that intercalation binding might be the interaction mode between HOXD and DNA.

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Tanwir, Ahmad, Rahat Jahan, Mohiuddin Abdul Quadir, Mohammad A. Kaisar, and Md Khalid Hossain. "Spectroscopic Studies of the Interaction between Metformin Hydrochloride and Bovine Serum Albumin." Dhaka University Journal of Pharmaceutical Sciences 11, no. 1 (November 4, 2012): 45–49. http://dx.doi.org/10.3329/dujps.v11i1.12486.

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The affinity of a drug to serum albumin has influence on the pharmacokinetics of a drug. In the present study, the mutual interaction of metformin hydrochloride (MET) with bovine serum albumin (BSA) was investigated using fluorescence spectroscopy under different conditions. It was observed that the fluorescence quenching of BSA by metformin hydrochloride is a result of the formation of metformin hydrochloride- BSA complex with probable involvement of tryptophan residue. Fluorescence quenching constants were determined using the Stern- Volmer equation and Vant Hoff equation to provide a measure of the thermodynamic parameters ?G, ?H, and ?S at different temperatures indicating that the hydrogen bond and the hydrophobic forces play a major role for metformin hydrochloride- BSA association. DOI: http://dx.doi.org/10.3329/dujps.v11i1.12486 Dhaka Univ. J. Pharm. Sci. 11(1): 45-49, 2012 (June)

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17

Liu, Yu Fen, Hai Tao Xia, and De Fu Rong. "Study of the Interaction between Zinc Complex and Bovine Serum Albumin by Fluorescence Spectroscopy." Advanced Materials Research 554-556 (July 2012): 1678–81. http://dx.doi.org/10.4028/www.scientific.net/amr.554-556.1678.

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The binding reaction of Zn(II) complex [Zn(C8H10N)2Cl2] with bovine serum albumin(BSA) was studied by fluorescence spectroscopy under the simulative physiological conditions. The intrinsic fluorescence of BSA could be quenched by Zn(II) complex. The quenching mechanism was suggested as static quenching according to the Stern–Volmer equation. The binding constants Kband the number of binding sites n were calculated. The Zn(II) complex exhibit good binding propensity to bovine serum albumin having relatively high binding constant values. The thermodynamic parameters indicate that the hydrogen bonds and van der Waals forces play a major role in BSA-Zn(II) complex association. The process of binding was spontaneous, in which Gibbs free energy change (ΔG) was negative.

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Grigoryan, K. R., H. A. Shilajyan, and V. A. Hovhannisyan. "BOVINE SERUM ALBUMIN FLUORESCENCE QUENCHING BY TANNIC ACID IN DIMETHYLSULFOXIDE CONTAINING SOLUTIONS." Proceedings of the YSU B: Chemical and Biological Sciences 54, no. 2 (252) (August 17, 2020): 99–104. http://dx.doi.org/10.46991/pysu:b/2020.54.2.099.

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Bovine serum albumin (BSA) interaction with tannic acid (TA) has been studied in dimethylsulfoxide (DMSO) aqueous solutions at different temperatures (293 and 303 K). To find out the fluorescence quenching mechanism of BSA in the presence of TA, the fluorescence data were analyzed according to the modified Stern-Volmer equation based on the approach of the existence of a “sphere of action” (a type of apparent static quenching). The values of apparent static and bimolecular quenching constants were calculated. The effect of DMSO and temperature on BSA–TA interactions is explained on the basis of structural changes in the “sphere of action” of the fluorophore due to the possible inclusion of DMSO molecules in this sphere.

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Zhou, J. H., X. H. Wu, C. Yang, X. T. Gu, L. Zhou, K. X. Song, Y. Y. Feng, and J. Shen. "Spectroscopic studies on the interaction of hypocrellin A with myoglobin." Spectroscopy 21, no. 4 (2007): 235–43. http://dx.doi.org/10.1155/2007/503537.

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Experimental results of UV-visible absorption spectroscopy and fluorescence spectroscopy indicate that hypocrellin A, which has been studied in photodynamic therapy, can interact with the surface of myoglobin through hydrophobic forces, and form a complex. Based on the Stern–Volmer equation, the quenching constants of the process can be calculated to be 4.81×1012L mol−1s−1(t=25°C) and 4.54×1012L mol−1s−1(t=42°C) respectively, and the binding constant is 5.53×104M−1(t=25°C), while the binding sites is 0.94 (t=25°C). In addition, Electron paramagnetic resonance and fluorescence spectroscopic analysis suggests that that the quenching mechanism of the interaction process occurs through the electron transfer between hypocrellin A and myoglobin.

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Geethanjali, H. S., D. Nagaraja, R. M. Melavanki, and R. A. Kusanur. "Fluorescence quenching of boronic acid derivatives by aniline in alcohols – A Negative deviation from Stern–Volmer equation." Journal of Luminescence 167 (November 2015): 216–21. http://dx.doi.org/10.1016/j.jlumin.2015.06.040.

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Kontarov, N. A., E. I. Dolgova, I. V. Pogarskaja, E. O. Kontarova, Ju B. Grishunina, and N. V. Yuminova. "Determination of thermodynamic binding parameters and type of interaction between the А/Bangkok/1/1979 (Н3N2) influenza virus hemagglutinin and phosphatidylcholine liposome." Biomeditsinskaya Khimiya 66, no. 5 (2020): 401–5. http://dx.doi.org/10.18097/pbmc20206605401.

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The study of interaction between surface viral proteins and model phospholipids is important for learning more details about the mechanisms of viral penetration into cells during infection. In this context, liposomes represent suitable systems for modeling a cell membrane. The binding of hemagglutinin (HA) of influenza virus with phosphatidylcholine liposomes was studied by equilibrium adsorption. It was interesting elucidate changes occurring in the structure of a protein during its translocation from the surface into the interior part of the membrane. In this work, we have studied characteristics of the protein-lipid interaction during HA complex formation with phospholipids including adsorption of HA on a phospholipid bilayer. Using the Scatchard equation and the Gibbs-Helmholtz equation at pH 4.0 and pH 6.0 thermodynamic parameters were determined. The results concluded the hydrophobic type of interaction between viral protein and liposomes. The additional confirmation of hydrophobic protein-lipid interaction presence was determination of HA distribution constants in two-phase systems: dextran-polyethylene glycol (K1) and dextran-polyethylene glycol esterified with palmitic acid (K2). The presence of hydrophobic interaction between HA and the liposome membrane was also confirmed using the quenching method of intrinsic protein fluorescence by a neutral quencher with acrylamide. At pH 4.0, an increase in the Stern-Volmer quenching constant was observed for the HA+liposome from phosphatidylcholine system, which is caused by structural changes in HA upon incorporation into the liposome bilayer. The fluorescence quenching rate constants calculated using the Stern-Volmer equation indicate a static quenching mechanism in which the quencher interacts with fluophors of a stationary protein molecule. The obtained results are interesting for not only studying virus and cell fusion theoretically, but also have practical applications. Using values of the protein-bilayer binding constant and free energy constant, it is possible to select the optimal phospholipid composition of liposomes or virosomes to obtain a stronger complex with various viral proteins. With two-phase systems, it is possible to determine the presence of hydrophobic sites on the viral protein surface, which can be used for evaluation both protein-lipid and protein-protein interaction.

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Beckford, Floyd A. "Reaction of the Anticancer Organometallic Ruthenium Compound, [(η6-p-Cymene)Ru(ATSC)Cl]PF6 with Human Serum Albumin." International Journal of Inorganic Chemistry 2010 (January 26, 2010): 1–7. http://dx.doi.org/10.1155/2010/975756.

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The reaction of [(η6-p-cymene)Ru(ATSC)Cl]PF6 (ATSC =9-anthraldehyde thiosemicarbazone) with human serum albumin was investigated at different temperatures using fluorescence and infrared spectrophotometry. The binding constant, K, for the reaction was determined using a number of different methods. Using a modified Stern-Volmer equation, K was determined to be 9.09×104,12.1×104, and 13.1×104 M−1 at 293 K, 298 K, and 308 K, respectively. A thermodynamic analysis showed that the reaction is spontaneous with ΔG being negative. The enthalpy of reaction ΔH=16.5 kJ mol−1 and the entropy of reaction ΔS=152 Jmol−1K−1. The values of ΔH and ΔS suggest that hydrophobic forces are dominant in the mode of interaction and that the process is mostly entropy driven.

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Amézqueta, Susana, José Luís Beltrán, Anna Maria Bolioli, Lluís Campos-Vicens, Francisco Javier Luque, and Clara Ràfols. "Evaluation of the Interactions between Human Serum Albumin (HSA) and Non-Steroidal Anti-Inflammatory (NSAIDs) Drugs by Multiwavelength Molecular Fluorescence, Structural and Computational Analysis." Pharmaceuticals 14, no. 3 (March 4, 2021): 214. http://dx.doi.org/10.3390/ph14030214.

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The interaction between drugs and transport proteins, such as albumins, is a key factor in drug bioavailability. One of the techniques commonly used for the evaluation of the drug-protein complex formation is fluorescence. This work studies the interaction of human serum albumin (HSA) with four non-steroidal anti-inflammatory drugs (NSAIDs)—ibuprofen, flurbiprofen, naproxen, and diflunisal—by monitoring the fluorescence quenching when the drug-albumin complex is formed. Two approaches—the double logarithm Stern-Volmer equation and the STAR program—are used to evaluate the binding parameters. The results are analyzed considering the binding properties, determined by using other complementary techniques and the available structural information of albumin complexes with NSAID-related compounds. Finally, this combined analysis has been synergistically used to interpret the binding of flurbiprofen to HSA.

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Fu, Yiying, Enli Guan, Jiangong Liang, Guolan Ren, and Lu Chen. "Probing the Effect of Ag2S Quantum Dots on Human Serum Albumin Using Spectral Techniques." Journal of Nanomaterials 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/7209489.

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The understanding of the interaction between protein and quantum dots (QDs) has significant implications for biological applications of QDs. Herein, we studied the effect of Ag2S QDs on human serum albumin (HSA) using UV-Vis absorption spectra and fluorescence spectroscopy and found that the fluorescence intensity of HSA was gradually decreased with increasing Ag2S QDs concentrations. By using the Stern-Volmer equation for the fluorescence quenching constant (KSV) of the response of Ag2S QDs to HSA as well as thermodynamic equations, the values of thermodynamic enthalpy change (ΔHθ), entropy change (ΔSθ), and free energy change (ΔGθ) were calculated to be −10.79 KJ·mol−1, 37.80 J·mol−1·K−1, and −22.27 KJ·mol−1, respectively. The results indicate that Ag2S QDs exert an obvious static fluorescence quenching effect on HSA and electrostatic interaction plays a key role in the binding process. Furthermore, Raman spectral analysis reveals that Ag2S QDs alter the external environment of tyrosine and tryptophan or the C-H bending of HSA but not the α-helical content.

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Deepa, H. R., J. Thipperudrappa, and H. M. Suresh Kumar. "A study on fluorescence quenching of a laser dye by aromatic amines in alcohols." Canadian Journal of Physics 93, no. 4 (April 2015): 469–74. http://dx.doi.org/10.1139/cjp-2014-0190.

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The fluorescence quenching of 1,2,3,8-tetrahydro-1,2,3,3,8-pentamethyl-5-(trifluoromethyl)-7H-pyrrolo[3,2-g]quinolin-7-one (LD-473) by aromatic amines, namely, aniline, dimethyl aniline, and diethyl aniline, in methanol, ethanol, propanol, and butanol has been studied at room temperature using steady-state and time-resolved methods. A positive deviation from linearity has been observed in Stern–Volmer (S–V) plots. Various quenching rate parameters have been determined using the extended S–V equation and are found to be dependent on the dielectric constant of alcohols. The quenching ability of amines increases with increasing their ionization energies. Further, with the use of the sphere of action, static quenching model, and finite sink approximation model, it is concluded that the bimolecular quenching reactions are due to the combined effect of both dynamic and static quenching processes.

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Qin, Ying, Yixuan Zhang, Shulian Yan, and Ling Ye. "A comparison study on the interaction of hyperoside and bovine serum albumin with Tachiya model and Stern–Volmer equation." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 75, no. 5 (May 2010): 1506–10. http://dx.doi.org/10.1016/j.saa.2010.02.007.

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Lin, Haitao, Liyun Ding, Bingyu Zhang, and Jun Huang. "Detection of nitrite based on fluorescent carbon dots by the hydrothermal method with folic acid." Royal Society Open Science 5, no. 5 (May 2018): 172149. http://dx.doi.org/10.1098/rsos.172149.

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A fluorescent carbon dots probe for the detection of aqueous nitrite was fabricated by a one-pot hydrothermal method, and the transmission electron microscope, X-ray diffractometer, UV–Vis absorption spectrometer and fluorescence spectrophotometer were used to study the property of carbon dots. The fluorescent property of carbon dots influenced by the concentration of aqueous nitrite was studied. The interaction between the electron-donating functional groups and the electron-accepting nitrous acid could account for the quenching effect on carbon dots by adding aqueous nitrite. The products of the hydrolysis of aqueous nitrite performed a stronger quenching effect at lower pH. The relationship between the relative fluorescence intensity of carbon dots and the concentration of nitrite was described by the Stern–Volmer equation ( I 0 / I − 1 = 0.046[ Q ]) with a fine linearity ( R 2 = 0.99). The carbon dots-based probe provides a convenient method for the detection of nitrite concentration.

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Gehlen, Marcelo H. "The centenary of the Stern-Volmer equation of fluorescence quenching: From the single line plot to the SV quenching map." Journal of Photochemistry and Photobiology C: Photochemistry Reviews 42 (March 2020): 100338. http://dx.doi.org/10.1016/j.jphotochemrev.2019.100338.

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Dominique, Dumas, Latger Véronique, Marie L. Viriot, and Jean F. Stoltz. "Permeability Oxygen Through Endothelium By Time-Resolved Fluorescence Microscopy : Influence.of Plasma Viscosity on Tissue Hypoxia." Microscopy and Microanalysis 5, S2 (August 1999): 1106–7. http://dx.doi.org/10.1017/s1431927600018857.

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Vascular endothelial cells (EC) forms a continuous monolayer, a selective barrier that coats the inner surface of the vascular system, representing the primary anatomical site between blood and tissue. Under closed conditions (shear stress, hypoxia-reoxygenation..), EC are activated and the level of adhesion molecules (ICAM-1) expression increased. A technique of fluorescence quenching by oxygen in cell membrane was used to study molecular transport processes on a larger scale1-4. Collisional fluorescence quenching is described by the Stern-Volmer equation : τ0 / τ = 1 + kd.PO2 where τ0 and τ are respectively the excited state lifetimes in the absence and in the presence of oxygen, Kd the quenching dynamic constant and PO2 the oxygen partial pressure. The main purpose of the present study was to investigate the relation a) between the plasma viscosity and PO2 across human EC monolayer by Time-Resolved Fluorescence Microscopy (TRFM5-6 ) between the PO2 calculated and the level of ICAM-1 expression by flow cytometry (FCM)7 and Conventional Optical Scanning Microscopy (COSM8).

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Deepa, N., and A. Balaji Ganesh. "Fiber Optic Sensor for Simultaneous Measurement of pH and Dissolved Oxygen." Applied Mechanics and Materials 573 (June 2014): 842–47. http://dx.doi.org/10.4028/www.scientific.net/amm.573.842.

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The work describes the constructions of optical fiber based minimal invasive sensing system to measure pH and dissolved oxygen using sol-gel membranes which are attached internally in any transparent container. The disposable sensing membranes are very thin size and prepared as fluorescent dye doped in silica film using simple procedures. The sensor characteristics such as response time, linearity, repeatability and reversibility are evaluated and the performance of the sensor also compared with commercial meters. The experiments such as, chemical stability and photo stability are also carried out. The detection limit of pH sensor is found between 3 pH and 10 pH, however good sensitivity is obtained for the ranges from 4 pH and 9 pH with the response time of 7 seconds. Non-linear response is obtained for dissolved oxygen sensor and it is made linear by applying Stern-Volmer equation. The oxygen sensor shows good sensitivity in the ranges from 2 mg/L to 8 mg/L.

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Christova, Petya, Kristina Todorova, Ilijana Timtcheva, Genoveva Nacheva, Andrey Karshikoff, and Peter Nikolova. "Fluorescence Studies on Denaturation and Stability of Recombinant Human Interferon-Gamma." Zeitschrift für Naturforschung C 58, no. 3-4 (April 1, 2003): 288–94. http://dx.doi.org/10.1515/znc-2003-3-425.

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Unfolding/folding transitions of recombinant human interferon-gamma (hIFNγ) in urea and guanidine chloride (Gn.HCl) solutions were studied by fluorescence spectroscopy. At pH 7.4 Gn.HCl was a much more efficient denaturant (midpoint of unfolding C* = 1.1 m and ΔG0 = 13.4 kJ/mol) than urea (C* = 2.8 m and ΔG0 = 11.7 kJ/mol). The close ΔG0 values indicate that the contribution of electrostatic interactions to the stability of hIFNγ is insignificant. Both the pH dependence of the fluorescence intensity and the unfolding experiments in urea at variable pH showed that hIFNγ remains native in the pH range of 4.8-9.5. Using two quenchers, iodide and acrylamide, and applying the Stern-Volmer equation, a cluster of acidic groups situated in close proximity to the single tryptophan residue was identified. Based on the denaturation experiments at different pH values and on our earlier calculations of the electrostatic interactions in hIFNγ, we assume that the protonation of Asp63 causes conformational changes having a substantial impact on the stability of hIFNγ.

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Zhao, Wu-xing, Chao Zhou, and Hong-shang Peng. "Ratiometric Luminescent Nanoprobes Based on Ruthenium and Terbium-Containing Metallopolymers for Intracellular Oxygen Sensing." Polymers 11, no. 8 (August 2, 2019): 1290. http://dx.doi.org/10.3390/polym11081290.

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A collection of luminescent metal complexes have been widely used as oxygen probes in the biomedical field. However, single intensity-based detection approach usually suffered from errors caused by the signal heterogeneity or fluctuation of the optoelectronic system. In this work, respective ruthenium (II) and terbium (III) complexes were chosen to coordinate a bipyridine-branched copolymer, so that to produce oxygen-sensitive metallopolymer (Ru-Poly) and oxygen-insensitive metallopolymer (Tb-Poly). Based on the hydrophobic Ru-Poly and Tb-Poly, a ratiometric luminescent oxygen nanoprobe was facilely prepared by a nanoprecipitation method. The nanoprobes have a typical size of ~100 nm in aqueous solution, exhibiting a green-red dual-wavelength emission under the excitation of 300 nm and 460 nm, respectively. The red emission is strongly quenched by dissolved oxygen while the green one is rather stable, and the ratiometric luminescence was well fitted by a linear Stern–Volmer equation. Using the ratiometric biocompatible nanoprobes, the distribution of intracellular oxygen within three-dimensional multi-cellular tumor spheroids was successfully imaged.

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Po Cheng, Wen, Yi Tsang Lu, Ruey Fang Yu, Xin Ru Lin, and Han Xin Li. "Finding the Reaction Constant Between Humic Acid and Metal Ions by Fluorescence Quenching Effect." International Journal of Engineering & Technology 7, no. 3.32 (August 26, 2018): 4. http://dx.doi.org/10.14419/ijet.v7i3.32.18379.

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Humic acid was used as the removal target for evaluating the coagulation efficiency in this study. When the metal ions mix with humic acid solution, a Fluorescence quenching effect may be observed conditionally. This effect can be described by Stern-Volmer linear equation which can be used for quantifying the quenching constant (KQ) of the Fluorescence quenching effect. In addition, the result of the quenching constant (KQ) was used to explain the electron-neutralization capability of the metal ions at different pH. The results indicated that there is no significant Fluorescence quenching effect between the additions of monovalent Na+ ion, divalent Ca2+ and humic acid. Otherwise, when pH of the FeCl3 solution was between 4.5 and 5.5, fluorescence quenching effect obviously occurred. The maximum KQ value was found to be 305,990 at pH 5. It means that the higher KQ value is, the better complex reaction between humic acid and aluminum salts will be. Through the KQ value study, the optimum pH can be quantified when humic acid solution is reacted with ferric ion.

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Evingür, Gülşen Akın, and Önder Pekcan. "Drying of polyacrylamide-multiwalled carbon nanotube (MWNT) composites with various MWNTs contents: a fluorescence study." Journal of Polymer Engineering 33, no. 1 (February 1, 2013): 33–39. http://dx.doi.org/10.1515/polyeng-2012-0128.

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Abstract We studied the drying of polyacrylamide (PAAm)-multiwalled carbon nanotube (MWNT) composites, prepared by free radical crosslinking copolymerization in water, with a steady state fluorescence technique. Composite gels were prepared at room temperature with pyranine (Py) doped as a fluorescence probe. Drying experiments were performed in air at various MWNT contents by real time monitoring of the Py fluorescence intensity (I) which increased as the drying proceeded. The Stern-Volmer equation, combined with the moving boundary diffusion model, was used to explain the behavior of I during drying. It was observed that the desorption coefficient (D) increased as the temperature increased. Drying energies (ΔE) were measured for the drying processes for each MWNT content gel, by using fluorescence, gravimetrical and volumetric methods. It is understood that ΔE values decrease by increasing MWNT content, until 1 wt% MWNT, and then increase above the level of this threshold value. The energy of drying is strongly correlated with the MWNT content in the composite. ΔE drops to its lowest value, at which conducting cluster starts to appear.

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Chowdhury, Sanchari, Venkat R. Bhethanabotla, and Rajan Sen. "Measurement of Oxygen Diffusivity and Permeability in Polymers Using Fluorescence Microscopy." Microscopy and Microanalysis 16, no. 6 (August 5, 2010): 725–34. http://dx.doi.org/10.1017/s1431927610000401.

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AbstractA simple fluorescence microscopy technique is developed and presented to investigate heterogeneities in emission intensity and quenching responses of luminescence sensors and to measure diffusion and permeation coefficients of oxygen in polymers. Most luminescence oxygen sensors do not follow linearity of the Stern-Volmer (SV) equation due to heterogeneity of luminophore in the polymer matrix. To circumvent this limitation, inverted fluorescence microscopy is utilized in this work to investigate the SV response of the sensors at the micron scale. It was found that intensity is higher in regions where the luminophore is aggregated, but the response is poorer to oxygen concentration. In contrast, the nearly homogeneous regions exhibit linearity with high SV constants. In these diffusion experiments, oxygen concentration was measured by luminescence changes in regions with high SV constants and good linearity. Two diffusion experiments were performed—termed film-on-sensor and accumulation-in-volume techniques. A new Fick's law based quasi-steady-state diffusion model was developed and combined with the SV equation to obtain effective permeation coefficients for the accumulation-in-volume technique. Using these experimental techniques, oxygen diffusion properties in free-standing Teflon polymer films, cast silicon elastomers, and cast polydimethylsiloxane films containing different weight percentages of zeolite were determined with good precision.

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Michelucci, Umberto, Michael Baumgartner, and Francesca Venturini. "Optical Oxygen Sensing with Artificial Intelligence." Sensors 19, no. 4 (February 14, 2019): 777. http://dx.doi.org/10.3390/s19040777.

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Luminescence-based sensors for measuring oxygen concentration are widely used in both industry and research due to the practical advantages and sensitivity of this type of sensing. The measuring principle is the luminescence quenching by oxygen molecules, which results in a change of the luminescence decay time and intensity. In the classical approach, this change is related to an oxygen concentration using the Stern-Volmer equation. This equation, which in most cases is non-linear, is parameterized through device-specific constants. Therefore, to determine these parameters, every sensor needs to be precisely calibrated at one or more known concentrations. This study explored an entirely new artificial intelligence approach and demonstrated the feasibility of oxygen sensing through machine learning. The specifically developed neural network learns very efficiently to relate the input quantities to the oxygen concentration. The results show a mean deviation of the predicted from the measured concentration of 0.5% air, comparable to many commercial and low-cost sensors. Since the network was trained using synthetically generated data, the accuracy of the model predictions is limited by the ability of the generated data to describe the measured data, opening up future possibilities for significant improvement by using a large number of experimental measurements for training. The approach described in this work demonstrates the applicability of artificial intelligence to sensing technology and paves the road for the next generation of sensors.

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Golub, Aleksander S., and Roland N. Pittman. "Barometric calibration of a luminescent oxygen probe." Journal of Applied Physiology 120, no. 7 (April 1, 2016): 809–16. http://dx.doi.org/10.1152/japplphysiol.01007.2015.

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The invention of the phosphorescence quenching method for the measurement of oxygen concentration in blood and tissue revolutionized physiological studies of oxygen transport in living organisms. Since the pioneering publication by Vanderkooi and Wilson in 1987, many researchers have contributed to the measurement of oxygen in the microcirculation, to oxygen imaging in tissues and microvessels, and to the development of new extracellular and intracellular phosphorescent probes. However, there is a problem of congruency in data from different laboratories, because of interlaboratory variability of the calibration coefficients in the Stern-Volmer equation. Published calibrations for a common oxygen probe, Pd-porphyrin + bovine serum albumin (BSA), vary because of differences in the techniques used. These methods are used for the formation of oxygen standards: chemical titration, calibrated gas mixtures, and an oxygen electrode. Each method in turn also needs calibration. We have designed a barometric method for the calibration of oxygen probes by using a regulated vacuum to set multiple Po2 standards. The method is fast and accurate and can be applied to biological fluids obtained during or after an experiment. Calibration over the full physiological Po2 range (1–120 mmHg) takes ∼15 min and requires 1–2 mg of probe.

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Lin, Haitao, Jun Huang, and Liyun Ding. "Preparation of Carbon Dots with High-Fluorescence Quantum Yield and Their Application in Dopamine Fluorescence Probe and Cellular Imaging." Journal of Nanomaterials 2019 (October 17, 2019): 1–9. http://dx.doi.org/10.1155/2019/5037243.

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Carbon dots represent a kind of fluorescent nanomaterial and have broad application prospects in the field of biosensing and optoelectronics. Here, we explored carbon dots with a high-fluorescence quantum yield rate synthesized from L-cysteine and citric acid by the microwave-assisted method. The characteristics of the carbon dots were studied using a transmission electron microscope, an X-ray diffractometer, X-ray photoelectron spectra, a UV-Vis absorption spectrometer, a FTIR spectrometer, and a fluorescence spectrophotometer. The obtained carbon dots exhibited a high-fluorescence quantum yield (up to 85%), which is due to the combination of amidogens and sulfydryl with carbon dots, and hence bring the improved fluorescence property. We used carbon dots for in vitro imaging of CRL-5822 cells and human umbilical vein endothelial cells, which showed the low inhibitory rate (0.8%) of cells for 48 h with good biocompatibility demonstrated by the cell viability assay. The image of cells can be observed clearly under UV light. The Stern-Volmer equation was introduced to describe the quenching effect between the fluorescence intensity of carbon dots and the concentration of aqueous dopamine (DA).

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39

Hays, Michael D., David K. Ryan, and Stephen Pennell. "A Modified Multisite Stern−Volmer Equation for the Determination of Conditional Stability Constants and Ligand Concentrations of Soil Fulvic Acid with Metal Ions." Analytical Chemistry 76, no. 3 (February 2004): 848–54. http://dx.doi.org/10.1021/ac0344135.

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40

Wahba, M. E. K., N. El-Enany, and F. Belal. "Application of the Stern–Volmer equation for studying the spectrofluorimetric quenching reaction of eosin with clindamycin hydrochloride in its pure form and pharmaceutical preparations." Analytical Methods 7, no. 24 (2015): 10445–51. http://dx.doi.org/10.1039/c3ay42093k.

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A sensitive, selective, economic, and validated spectrofluorimetric method was developed for the determination of clindamycin hydrochloride in pharmaceutical preparations, depending on the reaction of its tertiary amino group with eosin Y.

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41

Amin, Toufiq Ul, Md Reazul Islam, Md Zakir Sultan, Sonia Sultana, Md Saiful Islam, and Abul Hasnat. "Study of Interaction of Dextromethorphan Hydrobromide with Deoxyribonucleic Acid by Fluorescence Quenching." Bangladesh Pharmaceutical Journal 19, no. 2 (August 12, 2016): 197–205. http://dx.doi.org/10.3329/bpj.v19i2.29280.

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Interactions with many clinically active therapeutic agents with deoxyribonucleic acid (DNA) are well studied and it expedites deciphering the structure of DNA and to investigate the pathological implication of those molecules in a living organism. The interaction of dextromethorphan hydrobromide (DEX) with calf thymus DNA (ct DNA) was studied employing UV absorption and fluorescence spectroscopic techniques. The binding affinity of DEX to DNA was calculated at different temperatures and the stoichiometry of binding was characterized to be about 1 dextromethorphan molecule per nucleotide. Hypochromic effect was found in the absorption spectra of dextromethorphan, and its wavelength had no shift in the presence of DNA indicating external binding mode of dextromethorphan to DNA. Quenching constants 3532 L/ mol and 12446L/ mol at 298 K and 308 K respectively with correlation co-efficient of 0.974 and 0.976, using Stern-Volmer equation and the quenching mechanism was found to be dynamic. Fluorescence spectroscopic results showed the quenching of fluorescence intensity of DEX in the presence of DNA, indicating the interaction between DEX and DNA. Based on this, hydrophobic interaction were found to play the dominating role in DEX-DNA binding and those binding forces also indicate the binding site of dextromethorphan to be in the minor groove of DNA.Bangladesh Pharmaceutical Journal 19(2): 197-205, 2016

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Qiao, Pan, Li, Yang, Wen, Zhong, Wu, Su, and Tian. "Extracellular Oxygen Sensors Based on PtTFPP and Four-Arm Block Copolymers." Applied Sciences 9, no. 20 (October 17, 2019): 4404. http://dx.doi.org/10.3390/app9204404.

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Three four-arm amphiphilic block copolymers with different chain lengths, consisting of a hydrophilic chain of polyethylene glycol (PEG) and hydrophobic segment of polycaprolactam (PCL), were synthesized and used to encapsulate the high-efficient and hydrophobic oxygen probe of platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin (PtTFPP) to form polymer micelles. This approach enabled the use of PtTFPP in aqueous solution for biosensing. Experimental results demonstrated that the particle sizes of these nano-oxygen sensors between 40.0 and 203.8 nm depend on the structures of block copolymers. PtTFPP in these micelles showed an effective quantum yield under nitrogen environment, ranging from 0.06 to 0.159. The new sensors are suitable for analyzing dissolved oxygen concentrations in the range of 0.04–39.3 mg/L by using the linear Stern–Volmer equation at room temperature. In addition, it has been shown that these sensors are capable of in situ monitoring the dissolved oxygens in the culture medium of E. coli and Romas cells during the respiration process, and distinguishing the drug activity of antibiotic ampicillin from that of antimycin A. This study showed that the use of these nanostructured multi-arm block copolymer micelles can achieve efficient biological applications without specific structural modification of the hydrophobic PtTFPP probe, which is expected to have broad prospects.

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Ayodhya, Dasari, and Guttena Veerabhadram. "Synthesis and characterization of N, O-donor Schiff base capped ZnS NPs as a sensor for fluorescence selective detection of Fe 3+, Cr 2+ and Cd 2+ ions." Modern Electronic Materials 4, no. 4 (December 1, 2018): 151–62. http://dx.doi.org/10.3897/j.moem.4.4.35062.

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We report the simple synthesis of zinc sulfide nanoparticles (ZnSNPs) by a co-precipitation method using Schiff base, (2-[(4-methoxy-phenylimino)-methyl]-4-nitro phenol) as a capping agent. Here, Schiff base is also used as N, O-donor ligand to control the morphology of NPs and fluorescence interactions. The formation of ZnSNPs and their optical, structural, thermal properties and morphologies were studied by means of UV–vis DRS, fluorescence, FTIR, XRD, SEM, TEM, zeta potential and TGA. The optical properties and quantum confinement effect of the products were confirmed by means of spectroscopic measurements. XRD and TEM image shows that the synthesized ZnSNPs have cubic structures with a diameter of about less than 10 nm. The prepared ZnSNPs exhibited as a selective probe detection of Fe3+, Cr2+ and Cd2+ ions by fluorometrically and the emission band which disappears in the presence of increasing concentrations of Fe3+, Cr2+ and Cd2+ ions. Based on the fluorescence quenching of the NPs in the presence of metal ion of interest, the feasibility of their determinations was examined according to the Stern-Volmer equation. Our work suggested that Schiff base capped ZnSNPs could be a potential selective sensor in the detection of heavy metal ions.

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Yang, Yi, Xinpei Ma, Xiaxia Yang, and Huining Xu. "Influence of heavy metal ions on the spectra and charge characteristics of DOM of municipal sewage secondary effluent." Water Science and Technology 77, no. 4 (December 22, 2017): 1098–106. http://dx.doi.org/10.2166/wst.2017.639.

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Abstract The spectral and charged characteristics of dissolved organic matter (DOM) in municipal sewage secondary effluent influenced by heavy metal ions were studied by three-dimensional fluorescence spectroscopy, ultraviolet spectrometry, etc. As the Cu(II) concentration increased, the fluorescence intensity of the DOM's fluorescence peak reduced. When the Cu(II) concentration was 100 μmol/L, the fluorescence intensity of the humic-like acid in the DOM reduced by 19.5%–27.6%. However, there was no obvious change in the fluorescence intensity when Cd(II) was added. According to the modified Stern–Volmer equation, the conditional stability constant lgK and the proportion of the fluorescent functional groups of the DOM binding with Cu(II) were 2.19–2.69 and 16%–48%, respectively. The UV253/UV203 value changed little with the additional dosage of metal ions below 10 μmol/L, which increased as the concentration of Cu(II) or Pb(II) increased from 10–100 μmol/L. As the metal concentrations increase, the absolute values of the Zeta potential and the particle sizes of the DOM basically increased. The results showed that Cu(II) had the strongest binding ability to the groups that emitted fluorescence in the secondary effluent DOM compared to Pb(II) and Cd(II).

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Torres Filho, I. P., and M. Intaglietta. "Microvessel PO2 measurements by phosphorescence decay method." American Journal of Physiology-Heart and Circulatory Physiology 265, no. 4 (October 1, 1993): H1434—H1438. http://dx.doi.org/10.1152/ajpheart.1993.265.4.h1434.

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A system is described for the in vivo noninvasive measurement of intravascular PO2 at the microscopic level. Under special circumstances the method can also be used to measure interstitial PO2. The PO2 determination is based on the O2-dependent quenching of phosphorescence of palladium-porphyrins bound to albumin. This compound was injected intravenously in the dosage of 30 mg/kg body wt and dissolved in saline to a concentration of 15 mg/ml. The phosphorescence emission was excited by epi-illumination with a strobe xenon arc and measured by a photomultiplier in a well-defined tissue area as small as 15 x 30 microns. A selected portion of the phosphorescence decay was fitted by a single exponential, and the Stern-Volmer equation was used to calculate PO2. Calibration was performed in vitro using saline and blood and was in agreement with previous reports. In vivo observations were made in normal tissue regions from the unanesthetized hamster transparent skin fold chamber preparation. The method allows PO2 determinations, in the range of 0-80 mmHg, in microvessels with diameters of 15-100 microns. Simultaneous transillumination of the tissue also allows measurement of vessel diameter and red blood cell velocity in the same vessels.

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Mendonsa, Shaun D., and Robert J. Hurtubise. "Interactions of Phosphors in Glucose Glasses for Solid-Matrix Phosphorescence." Applied Spectroscopy 55, no. 10 (October 2001): 1385–93. http://dx.doi.org/10.1366/0003702011953522.

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Quenching of the room-temperature solid-matrix phosphorescence (SMP), near-infrared spectrometry, differential scanning calorimetry, and a polarity probe were used to study interactions of heterocyclic aromatic amines in glucose glasses prepared using crystalline glucose and a glucose melt. A near-infrared spectrometry method was developed to determine the wt % moisture in the glucose glasses. The wt % moisture of the glucose glasses was then related to phosphorescence intensities and lifetime ratios of the heterocyclic aromatic amines. A modified form of the Stern–Volmer equation was used to describe the changes in phosphorescence intensity and lifetime ratios. In other experiments, the glass transition temperatures of the glucose glasses were determined using differential scanning calorimetry. The glass transition temperatures were then correlated to the SMP of the heterocyclic aromatic amines in the glucose glasses. Lastly, the micro-environmental polarities of the glucose glasses were studied using a polarity probe. From these results a model was developed that described the effects of several parameters on the glucose glass matrices. For example, water was able to diffuse through channels in the glucose glasses and cause dynamic quenching of the phosphorescence. Also, the hydrogen bonding network in the glucose glasses was disrupted by water. This resulted in matrix quenching of the phosphorescence signals.

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Ren, Shuai, and M. Monica Giusti. "Monitoring the Interaction between Thermally Induced Whey Protein and Anthocyanin by Fluorescence Quenching Spectroscopy." Foods 10, no. 2 (February 3, 2021): 310. http://dx.doi.org/10.3390/foods10020310.

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The color stability of anthocyanins was shown to improve with addition of whey proteins (WP). The goal of this study was to investigate the binding mechanisms of purple corn, grape and black carrot anthocyanin extracts to native and preheated WP (40–80 °C, 3.6 μM) at a pH of 3 using fluorescence quenching spectroscopy. The fluorescence spectra were collected with an excitation wavelength of 280 nm at 25 °C, 35 °C and 45 °C. The quenching data were analyzed by using the Stern–Volmer equation. The fluorescence intensity of WP decreased (up to 73%) and its λmax increased (by ~5 nm) with increasing anthocyanin concentration (0–100 μM). The quenching data showed that the interaction between anthocyanin extracts and WP was a static quenching process. Thermodynamic analysis showed their binding was mainly through hydrophobic interactions. Their binding affinity was higher for preheated WP than native WP and decreased gradually with increasing preheating temperature. Black carrot anthocyanin extract had the lowest binding affinity with WP, likely due to the larger molecular structure. These results help better understand the protection mechanism of native and preheated WP on anthocyanin color stability, expanding the application of anthocyanins as food colorants that better withstand processing and storage.

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Patil, Omnath, P. K. Ingalagondi, Shivaraj Gounhalli, and S. M. Hanagodimath. "Dipole moments and quenching of fluorescence of a new coumarin dye." Canadian Journal of Physics 98, no. 8 (August 2020): 761–69. http://dx.doi.org/10.1139/cjp-2019-0517.

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The absorption and fluorescence emission spectra of a newly synthesized laser grade coumarin dye, 1-((4-methoxyphenoxy) methyl)-3H-benzo[f]chromen-3-one (4-MPMBC), have been recorded in various solvents having different polarities. The spectrum peak was found to shift toward a higher wavelength with an increase in the solvent polarity. The dipole moments of the ground state (μg) and excited state (μe) were estimated using the Lippert, Bakshiev, and Kawski–Chamma–Viallet equations. The μe values were found to be greater than the μg values in all solvents, indicating that the dye is more polar in the excited state than in the ground state. The absorption maximum and emission maximum energies, ground- and excited-state dipole moments, and HOMO–LUMO energy gaps were estimated using Gaussian 16W. These have been compared with the experimental results. The estimated chemical hardness of the dye molecule indicates the soft nature in all of the solvents. The reactive centers such as nucleophilic and electrophilic sites were identified along with contour action using electrostatic potential three-dimensional map density functional theory analysis. The fluorescence quenching has been studied in solvents of varying polarities using aniline as a quencher. The quenching process was found to follow the Stern–Volmer equation and was studied by considering the role of diffusion. In all solvents, the probability of quenching per encounter (p) was found to be less than unity. The activation energy for diffusion and activation energy for quenching were estimated using the values of p.

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Ibrahim, F., M. El-Din, and Heba El-Aziz. "New Validated Fluorescence Quenching Based Procedure for the Determination of Cilostazol and Clopidogrel in Bulk, Tablets and Biological Fluids, With Application of Stern-volmer Equation." British Journal of Pharmaceutical Research 12, no. 6 (January 10, 2016): 1–15. http://dx.doi.org/10.9734/bjpr/2016/28329.

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Al-Omari, Saleh. "Separation of static and dynamic thermodynamic parameters for the interaction between pyropheophorbide methyl ester and copper." Journal of Porphyrins and Phthalocyanines 18, no. 04 (April 2014): 297–304. http://dx.doi.org/10.1142/s1088424614500023.

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The interaction between pyropheophorbide methyl ester (PPME) and the ionic metal of copper ( Cu 2+) was investigated using fluorescence and UV-vis techniques. By analysis of the fluorescence spectra, it was observed that Cu 2+ has a strong ability to quench the intrinsic fluorescence of PPME through dynamic and static quenching process. The binding constants of Cu 2+ with PPME were determined at different temperatures depending on the results of fluorescence quenching. Based on the modified form of the Stern–Volmer equation, static binding constant (kS) and the dynamic binding constant (kD) of Cu 2+-PPME association were obtained at different temperatures. The static thermodynamic function of the enthalpy change (ΔHS), the dynamic thermodynamic function of the enthalpy change (ΔHD), the static thermodynamic function of the entropy change (ΔSS), and the dynamic thermodynamic function of the entropy change (ΔSD) for the binding interaction were determined according to the van't Hoff equation. The values of static Gibbs free energy change (ΔGS) and dynamic Gibbs free energy change (ΔGD) were determined to be negative indicating that the interaction process was a spontaneous. ΔHD and ΔSD values were positive indicating that the dynamic quenching process of Cu 2+-PPME interaction was driven mainly by hydrophobic forces. For the static binding quenching, ΔHS and ΔSS values were negative which indicated that hydrogen bond, electrostatic interaction, and van der Waals interaction were important driving forces for PPME- Cu 2+ association. Both static and dynamic fluorescence quenching were related to the distance between PPME and Cu 2+ indicating that the electron transfer process occurred.

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Journal articles on the topic 'Equation stern volmer'

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