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.

scholarly journals Solvent Effect on Fluorescence Quenching of 7, 8 Benzo‑4‑azido Methyl Coumarin by Aniline

2013 ◽  
Vol 12 (1) ◽  
pp. 69-85 ◽  
Author(s):  
R M Melavanki ◽  
N R Patil ◽  
D Nagaraja ◽  
H D Patil ◽  
J S Kadadevarmath ◽  
...  
Keyword(s):  
Fluorescence Quenching ◽  
Empirical Relation ◽  
Biologically Active ◽  
Static Quenching ◽  
Einstein Relation ◽  
Positive Deviation ◽  
Quenching Rate ◽  
R And D ◽  
Diffusion Limited ◽  
Static And Dynamic Quenching

Fluorescence quenching of biologically active studies of 7, 8 benzo-4-azidomethyl coumarin (7BAMC) by aniline in four different organic solvents namely benzene, dioxane, tetrahydrofuran and acetonitrile has been carried out at room temperature with a view to understand the quenching mechanisms. The Stern–Volmer (S-V) plot has been found to be non-linear with a positive deviation for all the solvents studied. In order to interpret these results we have invoked the ground state complex formation and sphere of action static quenching models. Using these models various quenching rate parameters have been determined. The magnitudes of these parameters suggest that sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check these bimolecular reactions as diffusion-limited and to estimate independently distance parameter R’ and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R’ and D with the values of the encounter distance R and the mutual coefficient D determined using the Edward’s empirical relation and Stokes – Einstein relation.

Effect of fluorescence quenching on 6BAAC in different solvents

2014 ◽  
Vol 92 (1) ◽  
pp. 41-45 ◽  
Author(s):  
N.R. Patil ◽  
R.M. Melavanki
Keyword(s):  
Fluorescence Quenching ◽  
Empirical Relation ◽  
Static Quenching ◽  
Einstein Relation ◽  
Positive Deviation ◽  
Quenching Rate ◽  
R And D ◽  
Diffusion Limited ◽  
Quenching Mechanisms ◽  
Static And Dynamic Quenching

The fluorescence quenching studies of 6-bromo-3-azidoacetyl coumarin (6BAAC) by aniline in four different solvents, namely acetonitrile, benzene, dioxane, and toluene, were carried out at room temperature to understand quenching mechanisms. The Stern–Volmer plots have been found to be nonlinear with a positive deviation for all the solvents studied. To interpret these results we have invoked the ground state complex formation and sphere of action static quenching models. Using these models various quenching rate parameters have been determined. The magnitudes of these parameters suggest that the sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation is attributed to the static and dynamic quenching. Further, with the use of the finite sink approximation model, it was possible to check these bimolecular reactions as diffusion-limited and to estimate independently distance parameter R′ and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R′ and D with the values of the encounter distance R and the mutual coefficient D determined using Edward’s empirical relation and the Stokes–Einstein relation.

scholarly journals Microwave-Assisted Synthesis and Fluorescent Properties of 4-Phenyl-1,8-naphthalimide

Molbank ◽  
10.3390/m1127 ◽  
2020 ◽  
Vol 2020 (2) ◽  
pp. M1127
Author(s):  
Frank Betancourt ◽  
James Helmkay ◽  
Hongbin Yan
Keyword(s):  
Bovine Serum Albumin ◽  
Fluorescence Quenching ◽  
Boronic Acid ◽  
Bovine Serum ◽  
Microwave Assisted Synthesis ◽  
Fluorescent Properties ◽  
Naphthalic Anhydride ◽  
Microwave Assisted ◽  
Phenyl Boronic Acid ◽  
Chloroform Methanol

4-Phenyl-1,8-naphthalimide was synthesized by imidation of commercially available 4-bromo-1,8-naphthalic anhydride, followed by Suzuki coupling with phenyl boronic acid, both under microwave heating. The microwave-assisted reactions were found to be faster and more efficient than reactions carried out by heating in oil-baths. While this compound was quite fluorescent in solvents such as chloroform, methanol and ethanol, it is virtually non-fluorescent in DMSO; however, upon the addition of water to DMSO solutions of this dye, fluorescence was restored, suggesting a tendency for aggregation-induced emission. The fluorescent properties of 4-phenyl-1,8-naphthalimide were found to be influenced by salt concentrations, likely as a result of hydrophobic effects. While this dye does not show binding to DNA, presence of bovine serum albumin leads to effective fluorescence quenching.

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.

scholarly journals New Insight into the Fluorescence Quenching of Nitrogen-Containing Carbonaceous Quantum Dots—From Surface Chemistry to Biomedical Applications

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2454
Author(s):  
Marek Wiśniewski ◽  
Joanna Czarnecka ◽  
Paulina Bolibok ◽  
Michał Świdziński ◽  
Katarzyna Roszek
Keyword(s):  
Quantum Dots ◽  
Fluorescence Quenching ◽  
Biomedical Applications ◽  
Bioactive Molecules ◽  
Reduced Form ◽  
Fluorescent Properties ◽  
Efficient Reduction ◽  
Wide Range ◽  
Ph Conditions

Carbon-based quantum dots are widely suggested as fluorescent carriers of drugs, genes or other bioactive molecules. In this work, we thoroughly examine the easy-to-obtain, biocompatible, nitrogen-containing carbonaceous quantum dots (N-CQDs) with stable fluorescent properties that are resistant to wide-range pH changes. Moreover, we explain the mechanism of fluorescence quenching at extreme pH conditions. Our in vitro results indicate that N-CQDs penetrate the cell membrane; however, fluorescence intensity measured inside the cells was lower than expected from carbonaceous dots extracellular concentration decrease. We studied the mechanism of quenching and identified reduced form of β-nicotinamide adenine dinucleotide (NADH) as one of the intracellular quenchers. We proved it experimentally that the elucidated redox process triggers the efficient reduction of amide functionalities to non-fluorescent amines on carbonaceous dots surface. We determined the 5 nm–wide reactive redox zone around the N-CQD surface. The better understanding of fluorescence quenching will help to accurately quantify and dose the internalized carbonaceous quantum dots for biomedical applications.

Using Quenching Kinetics and Thermodynamics of Amino-Fluorophores as Empirical Tools for Predicting Boronic Acid Sensors Suitable for Use in Physiological Conditions

2011 ◽  
Vol 64 (11) ◽  
pp. 1438 ◽  
Author(s):  
Nicholas McGregor ◽  
Christophe Pardin ◽  
W. G. Skene
Keyword(s):  
Electron Transfer ◽  
Fluorescence Quenching ◽  
Boronic Acid ◽  
Sulfonic Acid ◽  
Phenylboronic Acid ◽  
Water Soluble ◽  
Time Resolved ◽  
Diffusion Limited ◽  
Phenylboronic Acids ◽  
Acid Sensors

A series of water-soluble 1-amino-naphthalenes and 2-amino-fluorenes are prepared. These serve as model fluorophores for measuring the thermodynamics and kinetics of fluorescence quenching with phenylboronic acids and aliphatic amines. Steady-state and time-resolved fluorescence quenching kinetics are investigated using the Stern–Volmer method. Diffusion limited quenching constants and exergonic thermodynamics of electron transfer are derived for the 5-amino-1-napthol and 2-aminofluorene derivatives with phenylboronic acid and/or an aliphatic imine. No quenching and endergonic thermodynamics or electron transfer are observed for 5-sulfonamide, 5-sulfonic acid, or 5-hydroxy-7-sulfonic acid aminonaphthalene derivatives. Boronic acid sensors synthesized from these aminofluorophores by reductive amination with 2-formylphenylboronic acid undergo fluorescence revival in the presence of saccharides only when the fluorophore demonstrates diffusion limited quenching kinetics and exergonic thermodynamics of electron transfer with the boronic acid or imine quenchers. Thus, these two properties are suitable empirical tools for predicting saccharide-induced fluorescence revival of boronic acid sensors.

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.

Aspergillus sydowii Strain SCAU066 and Aspergillus versicolor Isolate BAB-6580: Potential Source of Xylanolytic, Cellulolytic and Amylolytic Enzymes

2020 ◽  
Vol 14 (2) ◽  
pp. 15
Author(s):  
Zaidah Zainal ariffin
Keyword(s):  
Extracellular Enzymes ◽  
Biologically Active ◽  
Aspergillus Versicolor ◽  
Aspergillus Sydowii ◽  
Aspergillus Tamarii ◽  
Alternative Source ◽  
Amylolytic Enzymes ◽  
Potato Dextrose Broth ◽  
Wide Range ◽  
Pharmaceutical Industries

Fungi is known to produce a wide range of biologically active metabolites and enzymes. Enzymes produced by fungi are utilized in food and pharmaceutical industries because of their rich enzymatic profile. Filamentous fungi are particularly interesting due to their high production of extracellular enzymes which has a large industrial potential. The aim of this study is to isolate potential soil fungi species that are able to produce functional enzymes for industries. Five Aspergillus species were successfully isolated from antibiotic overexposed soil (GPS coordinate of N3.093219 E101.40269) by standard microbiological method. The isolated fungi were identified via morphological observations and molecular tools; polymerase chain reactions, ITS 1 (5’- TCC GTA GGT GAA CCT GCG G3’) forward primer and ITS 4 (5’-TCC TCC GCT TAT TGA TAT GC-3’) reverse primer. The isolated fungi were identified as Aspergillus sydowii strain SCAU066, Aspergillus tamarii isolate TN-7, Aspergillus candidus strain KUFA 0062, Aspergillus versicolor isolate BAB-6580, and Aspergillus protuberus strain KAS 6024. Supernatant obtained via submerged fermentation of the isolated fungi in potato dextrose broth (PDB) and extracted via centrifugation was loaded onto specific media to screen for the production of xylanolytic, cellulolytic and amylolytic enzymes. The present findings indicate that Aspergillus sydowii strain SCAU066 and Aspergillus versicolor isolate BAB-6580 have great potential as an alternative source of xylanolytic, cellulolytic and amylolytic enzymes.

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