scholarly journals Molecular interaction studies of peptides using steady-state fluorescence intensity. Static (de)quenching revisited

2008 ◽  
Vol 14 (4) ◽  
pp. 401-406 ◽  
Author(s):  
Marta M. B. Ribeiro ◽  
Henri G. Franquelim ◽  
Miguel A. R. B. Castanho ◽  
Ana Salomé Veiga
Keyword(s):  
Steady State ◽  
Fluorescence Intensity ◽  
Molecular Interaction ◽  
Steady State Fluorescence ◽  
Interaction Studies

Steady-State Fluorescence of Polystyrene Plasticized by Supercritical Carbon Dioxide

1996 ◽  
Vol 50 (6) ◽  
pp. 740-746 ◽  
Author(s):  
Ming Li ◽  
Frank V. Bright
Keyword(s):  
Molecular Weight ◽  
Steady State ◽  
Conformational Changes ◽  
Fluorescence Intensity ◽  
Excitation Wavelength ◽  
Fluorescence Intensity Ratio ◽  
Steady State Fluorescence ◽  
Proposed Model ◽  
Major Increase ◽  
Reduced Density

A steady-state fluorescence study of low-molecular-weight polystyrene (MW = 1060 g/mol and 13,000 g/mol) plasticized in supercritical CO2 is reported. In addition to excitation wavelength, molecular weight, and polystyrene concentration dependencies, CO2 density also strongly affects the emission spectral contours. A major increase in the steady-state fluorescence intensity and a significant decrease in the polystyrene 320- to 365-nm fluorescence intensity ratio are observed when CO2 density is increased. Concentration and conformational changes in the polystyrene molecules are used to explain the observations, and these results are proposed to arise from changes in the plasticization power of supercritical CO2 over the density range studied. A theoretical model is proposed that is based on the assumption that, at low CO2 densities and low polymer concentrations, polystyrene intermolecular interactions are negligible. The proposed model is able to fit our observed fluorescence data from a CO2 reduced density of 0.3 to 1.4.

2‘,7‘-Difluorofluorescein Excited-State Proton Reactions:  Correlation between Time-Resolved Emission and Steady-State Fluorescence Intensity

2005 ◽  
Vol 109 (12) ◽  
pp. 2840-2846 ◽  
Author(s):  
Angel Orte ◽  
Ruperto Bermejo ◽  
Eva M. Talavera ◽  
Luis Crovetto ◽  
Jose M. Alvarez-Pez
Keyword(s):  
Excited State ◽  
Steady State ◽  
Fluorescence Intensity ◽  
Time Resolved ◽  
Steady State Fluorescence

Fluorescence Energy Transfer between Fluorescein Label and DNA Intercalators to Detect Nucleic Acids Hybridization in Homogeneous Media

2003 ◽  
Vol 57 (2) ◽  
pp. 208-215 ◽  
Author(s):  
Eva M. Talavera ◽  
Ruperto Bermejo ◽  
Luis Crovetto ◽  
Angel Orte ◽  
Jose M. Alvarez-Pez
Keyword(s):  
Energy Transfer ◽  
Steady State ◽  
Nucleic Acid ◽  
Fluorescence Intensity ◽  
Single Strand ◽  
Fluorescence Energy Transfer ◽  
Steady State Fluorescence ◽  
Fluorescein Label ◽  
Homogeneous Media ◽  
Fluorescence Energy

A general approach to detecting nucleic acid sequences in homogeneous media by means of steady-state fluorescence measurements is proposed. The methodology combines the use of a fluorescence-labeled single-strand DNA model probe, the complementary single-strand DNA target, and a DNA intercalator. The probe was fluorescein labeled to a spacer arm at the N4 position of the cytosine amino groups in polyribocytidylic acid (5′), poly(C), which acts as a model DNA probe. The complementary strand was polyriboinosinic acid (5′), poly(I), as a model of the target, and the energy transfer acceptor was an intercalator, either ethidium bromide or ethidium homodimer. In previous papers we have shown that the fluorescence intensity of the fluorescein label decreases when labeled poly(C) hybridizes with poly(I), and this fluorescence quenching can be used to detect DNA hybridization or renaturation in homogeneous media. In this paper we demonstrate that fluorescence resonance energy transfer (FRET) between fluorescein labeled to poly(C) and an intercalator agent takes place when single-stranded poly(C) hybridizes with poly(I), and we show how the fluorescence energy transfer further decreases the steady-state fluorescence intensity of the label, thus increasing the detection limit of the method. The main aim of this work was to develop a truly homogeneous detection system for specific nucleic acid hybridization in solution using steady-state fluorescence and FRET, but with the advantage of only having to label the probe with the energy donor since the energy acceptor is intercalated spontaneously. Moreover, the site label is not critical and can be labeled randomly in the DNA strand. Thus, the method is simpler than those published previously based on FRET. The experiments were carried out in both direct and competitive formats.

scholarly journals Swelling of iota-carrageenan gels prepared with various CaCl2 content: A fluorescence study

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Özlem Tarı ◽  
Önder Pekcan
Keyword(s):  
Steady State ◽  
Water Vapor ◽  
Fluorescence Intensity ◽  
Diffusion Coefficients ◽  
Fluorescence Probe ◽  
Activation Energies ◽  
The Other ◽  
Fluorescence Study ◽  
Time Constants ◽  
Steady State Fluorescence

AbstractIota carrageenan gels prepared with various CaCl2 content were completely dried and then swelled in water vapor. Steady-state fluorescence (SSF) technique was used to monitor the swelling process of each iota carrageenan gels at various temperatures. Pyranine was used as a fluorescence probe. Apparent fluorescence intensity, I increased as swelling time increased for all gel samples. The increase in I was modelled using Li-Tanaka equation from which the swelling time constants, τ1 and cooperative diffusion coefficients, Dc were determined. It was observed that Dc increased as the swelling temperature was increased. On the other hand at each temperature, it was seen that Dc decreased as CaCl2 content was increased. Activation energies for swelling were obtained and found to be 60.5, 61.0, 61.5 and 62.8 kJmol-1 for the gels prepared with increasing amount of CaCl2 content.

scholarly journals Differential effects of spermine and its analogues on the structures of polynucleotides complexed with ethidium bromide

1993 ◽  
Vol 291 (1) ◽  
pp. 269-274 ◽  
Author(s):  
J G Delcros ◽  
M C J M Sturkenboom ◽  
H S Basu ◽  
R H Shafer ◽  
J Szöllösi ◽  
...  
Keyword(s):  
Steady State ◽  
Ethidium Bromide ◽  
Fluorescence Intensity ◽  
Fluorescence Polarization ◽  
Structural Changes ◽  
Fluorescence Depolarization ◽  
Polyamine Analogues ◽  
Steady State Fluorescence ◽  
Base Sequences ◽  
Spermine Analogues

The interactions of spermine and polyamine analogues with synthetic polynucleotides of various base sequences complexed with ethidium bromide (EB) were investigated using measurements of fluorescence intensity and steady-state fluorescence polarization. Spermine and polyamine analogues displaced some but not all of the EB bound to poly(dA-dT).poly(dA-dT) or poly(dG-dC).poly(dG-dC), suggesting that polyamines may stabilize these polynucleotides in a conformation with reduced affinity for EB. Modifications of the aliphatic backbone of spermine have pronounced effects on its ability to displace EB from poly(dA-dT).poly(dA-dT) but not from poly-(dG-dC).poly(dG-dC). Spermine and some but not all of the polyamine analogues caused fluorescence depolarization when they interacted with the complex of EB and poly(dA-dT).poly-(dA-dT). Neither spermine nor any of the analogues, however, induced fluorescence depolarization in the complex of EB with poly(dG-dC).poly(dG-dC) or poly(dA).poly(dT). This suggests that spermine and some spermine analogues induce structural changes specific to alternating A-T sequences.

Spectroscopic Studies of Asparaginyl-tRNA Synthetase from Entamoeba histolytica

2019 ◽  
Vol 26 (6) ◽  
pp. 435-448
Author(s):  
Priyanka Biswas ◽  
Dillip K. Sahu ◽  
Kalyanasis Sahu ◽  
Rajat Banerjee
Keyword(s):  
Circular Dichroism ◽  
Steady State ◽  
Entamoeba Histolytica ◽  
Protein Concentration ◽  
Trna Synthetase ◽  
Solvent Exposure ◽  
Steady State Fluorescence ◽  
State Process ◽  
Wide Range ◽  
Circular Dichroïsm

Background: Aminoacyl-tRNA synthetases play an important role in catalyzing the first step in protein synthesis by attaching the appropriate amino acid to its cognate tRNA which then transported to the growing polypeptide chain. Asparaginyl-tRNA Synthetase (AsnRS) from Brugia malayi, Leishmania major, Thermus thermophilus, Trypanosoma brucei have been shown to play an important role in survival and pathogenesis. Entamoeba histolytica (Ehis) is an anaerobic eukaryotic pathogen that infects the large intestines of humans. It is a major cause of dysentery and has the potential to cause life-threatening abscesses in the liver and other organs making it the second leading cause of parasitic death after malaria. Ehis-AsnRS has not been studied in detail, except the crystal structure determined at 3 Å resolution showing that it is primarily α-helical and dimeric. It is a homodimer, with each 52 kDa monomer consisting of 451 amino acids. It has a relatively short N-terminal as compared to its human and yeast counterparts. Objective: Our study focusses to understand certain structural characteristics of Ehis-AsnRS using biophysical tools to decipher the thermodynamics of unfolding and its binding properties. Methods: Ehis-AsnRS was cloned and expressed in E. coli BL21DE3 cells. Protein purification was performed using Ni-NTA affinity chromatography, following which the protein was used for biophysical studies. Various techniques such as steady-state fluorescence, quenching, circular dichroism, differential scanning fluorimetry, isothermal calorimetry and fluorescence lifetime studies were employed for the conformational characterization of Ehis-AsnRS. Protein concentration for far-UV and near-UV circular dichroism experiments was 8 µM and 20 µM respectively, while 4 µM protein was used for the rest of the experiments. Results: The present study revealed that Ehis-AsnRS undergoes unfolding when subjected to increasing concentration of GdnHCl and the process is reversible. With increasing temperature, it retains its structural compactness up to 45ºC before it unfolds. Steady-state fluorescence, circular dichroism and hydrophobic dye binding experiments cumulatively suggest that Ehis-AsnRS undergoes a two-state transition during unfolding. Shifting of the transition mid-point with increasing protein concentration further illustrate that dissociation and unfolding processes are coupled indicating the absence of any detectable folded monomer. Conclusion: This article indicates that GdnHCl induced denaturation of Ehis-AsnRS is a two – state process and does not involve any intermediate; unfolding occurs directly from native dimer to unfolded monomer. The solvent exposure of the tryptophan residues is biphasic, indicating selective quenching. Ehis-AsnRS also exhibits a structural as well as functional stability over a wide range of pH.

In silico Screening and Molecular Interaction Studies of Tetrahydrocannabinol and its Derivatives with Acetylcholine Binding Protein

2018 ◽  
Vol 12 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Priya P. Panigrahi ◽  
Ramit Singla ◽  
Ankush Bansal ◽  
Moacyr Comar Junior ◽  
Vikas Jaitak ◽  
...  
Keyword(s):  
Molecular Interaction ◽  
In Silico ◽  
Binding Protein ◽  
In Silico Screening ◽  
Acetylcholine Binding Protein ◽  
Interaction Studies
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