scholarly journals Spectroscopic Study on the Reaction of Singlet-Excited Nile Blue with Certain Antioxidants

2021 ◽  
Author(s):  
C. Manivannan ◽  
S. Baskaran ◽  
Anbazhagan V
Keyword(s):  
Antioxidant Activity ◽  
Fluorescence Quenching ◽  
Electronic Properties ◽  
Nile Blue ◽  
Quenching Rate ◽  
Visible Absorption ◽  
Time Resolved ◽  
Fluorescence Measurements ◽  
Different Temperatures ◽  
Bimolecular Quenching

Abstract The photoinduced interaction of nile blue (NB) with various antioxidant molecules was investigated by fluorescence quenching technique and lifetime measurements. The various substituted catecholic compounds are employed as quenchers to evaluate their antioxidant activity. The formations of ground state complex between NB and quencher molecules observed from the UV-Visible absorption spectroscopy. The bimolecular quenching rate constants (kq) values depend on presence of substituent and its electronic properties of quencher molecules. Fluorescence quenching experiments have been performed at three different temperatures to assess the thermodynamic parameters. Time resolved fluorescence measurements suggest that the fluorescence quenching of NB with antioxidant molecules undergoes static quenching mechanism. The bond dissociation enthalpy (BDE) values reveal the discharge of HTfrom the antioxidant molecules. The electronic properties play an important role in the antioxidant activity of quencher molecules. The mechanism of fluorescence quenching between NB and quencher molecules are analysed based on the fluorescence quenching experiments, cyclic voltammetry experiments and BDE calculations.

A study on fluorescence quenching of a laser dye by aromatic amines in alcohols

2015 ◽  
Vol 93 (4) ◽  
pp. 469-474 ◽  
Author(s):  
H.R. Deepa ◽  
J. Thipperudrappa ◽  
H.M. Suresh Kumar
Keyword(s):  
Fluorescence Quenching ◽  
Aromatic Amines ◽  
Room Temperature ◽  
Static Quenching ◽  
Laser Dye ◽  
Approximation Model ◽  
Positive Deviation ◽  
Quenching Rate ◽  
Time Resolved ◽  
Bimolecular Quenching

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.

A Spectroscopic Approach with Theoretical Studies to Study the Interaction of 9-aminoacridine with Certain Phenols

2017 ◽  
Vol 231 (5) ◽  
Author(s):  
Chandrakumar Manivannan ◽  
Rajadurai Vijay Solomon ◽  
Ponnambalam Venuvanalingam ◽  
Rajalingam Renganathan
Keyword(s):  
Steady State ◽  
Bathochromic Shift ◽  
Acetonitrile Solution ◽  
Theoretical Studies ◽  
Time Resolved Fluorescence ◽  
Quenching Rate ◽  
Time Resolved ◽  
Fluorescence Measurements ◽  
Quenching Rate Constant ◽  
Bimolecular Quenching

AbstractThe influence of phenols upon the fluorescence quenching of 9-aminoacridine (9-AA) was examined in acetonitrile solution by employing steady state and time-resolved fluorescence measurements. On increasing the concentration of quencher molecules the absorption spectra of 9-AA change with significant bathochromic shift. The fluorescence intensity of 9-AA change in presence of quencher molecules were measured at various temperatures as a function of the quencher concentrations. The observed bimolecular quenching rate constant (k

scholarly journals Fluorescence Quenching Studies on the Interactions between Chosen Fluoroquinolones and Selected Stable TEMPO and PROXYL Nitroxides

2021 ◽  
Vol 22 (2) ◽  
pp. 885
Author(s):  
Krzysztof Żamojć ◽  
Irena Bylińska ◽  
Wiesław Wiczk ◽  
Lech Chmurzyński
Keyword(s):  
Fluorescence Quenching ◽  
Rate Constants ◽  
Quenching Rate ◽  
Time Resolved ◽  
Radiative Processes ◽  
Diffusion Limited ◽  
Fluoroquinolone Antibiotics ◽  
Quenching Efficiency ◽  
Bimolecular Quenching ◽  
The Impact

The influence of the stable 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) nitroxide and its six C4-substituted derivatives, as well as two C3-substituted analogues of 2,2,5,5-tetramethylpyrrolidynyl-N-oxyl (PROXYL) nitroxide on the chosen fluoroquinolone antibiotics (marbofloxacin, ciprofloxacin, danofloxacin, norfloxacin, enrofloxacin, levofloxacin and ofloxacin), has been examined in aqueous solutions by UV absorption as well as steady-state and time-resolved fluorescence spectroscopies. The mechanism of fluorescence quenching has been specified and proved to be purely dynamic (collisional) for all the studied systems, which was additionally confirmed by temperature dependence experiments. Moreover, the selected quenching parameters—that is, Stern–Volmer quenching constants and bimolecular quenching rate constants—have been determined and explained. The possibility of electron transfer was ruled out, and the quenching was found to be diffusion-limited, being a result of the increase in non-radiative processes. Furthermore, as the chosen nitroxides affected the fluorescence of fluoroquinolone antibiotics in different ways, an influence of the structure and the type of substituents in the molecules of both fluoroquinolones and stable radicals on the quenching efficiency has been determined and discussed. Finally, the impact of the solvent’s polarity on the values of bimolecular quenching rate constants has been explained. The significance of the project comes from many applications of nitroxides in chemistry, biology and industry.

Resonance energy transfer study of laser dyes LD 489 and LD 473 with rhodamine 6G

2014 ◽  
Vol 92 (4) ◽  
pp. 302-306 ◽  
Author(s):  
H.R. Deepa ◽  
J. Thipperudrappa ◽  
H.M. Suresh Kumar
Keyword(s):  
Energy Transfer ◽  
Rhodamine 6G ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Laser Dyes ◽  
Rate Parameter ◽  
Quenching Rate ◽  
Range Interaction ◽  
Time Resolved ◽  
Bimolecular Quenching

The energy transfer using two laser dyes 6,7,8,9-tetrahydro-6,8,9-trimethyl-4-(trifluoromethyl)-2H-pyrano[2,3-b][1,8]naphthyridin-2-one (LD-489) and 1,2,3,8-tetrahydro-1,2,3,3,8-pentamethyl-5-(trifluoromethyl)-7H-pyrrolo[3,2-g]quinolin-7-one (LD-473) as donors and rhodamine 6G (Rh6G) as acceptor was investigated in methanol using steady state and time resolved fluorescence spectroscopy. The bimolecular quenching rate parameter, kq, and the translation diffusion rate parameter, kd, were calculated and these values indicated that the diffusion process alone does not operate in energy transfer process. The mean diffusion length, d1, is found to be less than the Förster distance, R0, supporting the dominance of long-range interaction. The critical transfer distances determined from both the Förster equation and the half quenching concentration are close to one another, revealing that the Förster mechanism plays an important role in overall energy transfer of the donors.

scholarly journals Sequestration Effect on the Open-Cyclic Switchable Property of Warfarin by Cyclodextrin: Ultrafast Dynamical Study

2017 ◽  
Author(s):  
Naji Al-Dubaili ◽  
Na'il Saleh
Keyword(s):  
Excited State ◽  
Excited States ◽  
Time Resolved Fluorescence ◽  
Excited State Lifetime ◽  
Deprotonated Form ◽  
Dynamical Study ◽  
Visible Absorption ◽  
Time Resolved ◽  
Pka Values ◽  
Fluorescence Measurements

The excited-state lifetimes of the anticoagulant drug warfarin (W) in water and in the absence and presence of methyl-β-cyclodextrins (Me-β-CD) were recorded using time-resolved fluorescence measurements. Selective excitation of the open and cyclic protonated isomers of W were acquired with laser emitting diodes (LED) producing 320 and 280 nm excitation pulses, respectively. Formation of the inclusion complex was checked by UV–visible absorption spectroscopy, and the values of binding constants (2.9 × 103 M–1 and 4.2 × 102 M–1 for protonated and deprotonated forms, respectively) were extracted from the spectrophotometric data. Both absorption and time-resolved fluorescence results established that the interior of the macromolecular host binds preferentially the open protonated form, red shifts the maximum of its absorption of light at ~305 nm, extends its excited-state lifetime, and decreases its emission quantum yield (ФF). Collectively, sequestration of the open guest molecules decreases markedly their radiative rate constants (kr), likely due to formation of hydrogen-bonded complexes in both the ground and excited states. Due to lack of interactions, no change was observed in the excited-state lifetime of the cyclic form in the presence of Me-β-CD. The host also increases the excited-state lifetime and ФF of the drug deprotonated form (W¯). These later findings could be attributed to the increased rigidity inside the cavity of Me-β-CD. The pKa values extracted from the variations of the UV–visible absorption spectra of W versus the pH of aqueous solution showed that the open isomer is more acidic in both ground and excited states. The positive shifts in pKa values induced by three derivatives of cyclodextrins: HE-β-CD, Ac-β-CD, and Me-β-CD supported the preferential binding of these hosts to open isomers over cyclic.

Interaction of Nitroglycerin with Bovine Serum Albumin and the Influence of Metal Ions on the Binding

2020 ◽  
Vol 42 (2) ◽  
pp. 180-180
Author(s):  
Chengman Bao Chengman Bao ◽  
Jialian Wang Jialian Wang ◽  
Xuehong Tong Xuehong Tong ◽  
Chunli Zhang Chunli Zhang ◽  
Xinhui Tang Xinhui Tang
Keyword(s):  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Metal Ions ◽  
Bovine Serum ◽  
Binding Constants ◽  
Entropy Change ◽  
Quenching Rate ◽  
Different Temperatures ◽  
Quenching Rate Constant ◽  
Bimolecular Quenching

The effect of Cu2+, Ca2+, Mg2+and Zn2+ on the interaction between nitroglycerin and bovine serum albumin was investigated. The bimolecular quenching rate constant, the Stern-Volmer quenching constant, the binding constants and the number of binding sites were calculated in the absence and presence of Cu2+, Ca2+, Mg2+and Zn2+. The quenching constants of nitroglycerin to bovine serum albumin were increased in the presence of metal ions. Static quenching mechanism was also confirmed. The binding constants of nitroglycerin to bovine serum albumin were influenced by different metal ions. The enthalpy change, free energy chang, entropy change and the distance between the donor and the acceptor at different temperatures were calculated. The results indicated that energy transfer from bovine serum albumin to nitroglycerin occurs with high probability.

Fluorescence study on transmembrane Ca2+ gradient-mediated conformation changes of sarcoplasmic reticulum Ca2+-ATPase

1994 ◽  
Vol 14 (6) ◽  
pp. 309-317 ◽  
Author(s):  
Y. P. Tu ◽  
F. Y. Yang
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Fluorescence Quenching ◽  
Conformational Changes ◽  
Dynamic Change ◽  
Parasitic Fungus ◽  
Time Resolved Fluorescence ◽  
Fluorescence Study ◽  
Time Resolved ◽  
Fluorescence Measurements ◽  
Tryptophan Residues

The conformational states of Ca2+-ATPase in sarcoplasmic reticulum (SR) vesicles with or without a thousand-fold transmembrane Ca2+ gradient have been studied by fluorescence spectroscopy and fluorescence quenching. In consequence of the establishment of the transmembrane Ca2+ gradient, the steady-state fluorescence results revealed a reproducible 8% decrease in the intrinsic fluorescence while time-resolved fluorescence measurements showed that 13 tryptophan residues in SR · Ca2+-ATPase could be divided into three groups. The fluorescence lifetime of one of these groups increased from 5.5 ns to 5.95 ns in the presence of a Ca2+ gradient. Using KI and hypocrellin B (a photosensitive pigment obtained from a parasitic fungus, growing in Yunnan, China), the fluorescence quenching further indicated that the dynamic change of this tryptophan group, located at the protein-lipid interface, is a characteristic of transmembrane Ca2+ gradient-mediated conformational changes in SR · Ca2+-ATPase.

Fluorescence quenching of a biologically active boronic acid derivative by aniline in different solvents

2018 ◽  
Vol 96 (6) ◽  
pp. 603-609 ◽  
Author(s):  
Raveendra M. Melavanki
Keyword(s):  
Fluorescence Quenching ◽  
Boronic Acid ◽  
Biologically Active ◽  
Fluorescent Properties ◽  
Quenching Rate ◽  
Diffusion Limited ◽  
Fluorescence Measurements ◽  
Wide Range ◽  
Boronic Acid Derivatives ◽  
Fluorescent Molecules

Boronic acid derivatives are novel biologically active fluorescent molecules with numerous applications in various fields. A study of their fluorescent properties reveals some information that can be utilized in sensor design. One such study is fluorescence quenching. Here fluorescence quenching of 2-methoxypyridin-3-yl-3-boronic acid (2MPBA) in different solvents of a wide range of polarities has been carried out at room temperature by steady state fluorescence measurements. Aniline is used as the quencher. The positive deviation observed in Stern–Volmer (S-V) plots is analyzed using different quenching models. Various quenching parameters like S-V constant (KSV), quenching rate parameter (kq), volume constant (V), and kinetic distance (r) have been estimated using extended S-V equations. KSV is found to vary from 12.94 to 62.49 (mol/L)−1 with respect to solvents. From the calculated values of these parameters it is concluded that the static quenching mechanism is active in the studied system. However the reactions are diffusion-limited, which is confirmed by invoking the finite sink approximation model.

BOVINE SERUM ALBUMIN FLUORESCENCE QUENCHING BY TANNIC ACID IN DIMETHYLSULFOXIDE CONTAINING SOLUTIONS

2020 ◽  
Vol 54 (2 (252)) ◽  
pp. 99-104
Author(s):  
K.R. Grigoryan ◽  
H.A. Shilajyan ◽  
V.A. Hovhannisyan
Keyword(s):  
Bovine Serum Albumin ◽  
Fluorescence Quenching ◽  
Serum Albumin ◽  
Tannic Acid ◽  
Bovine Serum ◽  
Structural Changes ◽  
Different Temperatures ◽  
Fluorescence Quenching Mechanism ◽  
Bimolecular Quenching ◽  
Bsa Interaction

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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