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 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

scholarly journals Synthesis of Dense 1,2,3-Triazole Polymers Soluble in Common Organic Solvents

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1627
Author(s):  
Shota Yamasaki ◽  
Yuri Kamon ◽  
Linlin Xu ◽  
Akihito Hashidzume
Keyword(s):  
Differential Scanning Calorimetry ◽  
Steady State ◽  
Melting Point ◽  
Organic Solvents ◽  
Fluorescence Band ◽  
Excitation Wavelength ◽  
Fluorescence Study ◽  
Scanning Calorimetry ◽  
Steady State Fluorescence ◽  
Calorimetry Data

Aiming at synthesis of dense 1,2,3-triazole polymers soluble in common organic solvents, a new 3-azido-1-propyne derivative, i.e., t-butyl 4-azido-5-hexynoate (tBuAH), was synthesized and polymerized by copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) and Huisgen cycloaddition (HC). CuAAC polymerization produced poly(tBuAH) composed of 1,4-disubstituted 1,2,3-triazole units (1,4-units), whereas HC polymerization gave poly(tBuAH) composed of 1,4- and 1,5-disubstituted 1,2,3-triazole units (1,4- and 1,5-units). In HC polymerization, the fraction of 1,4-unit (f1,4) decreased with the permittivity of solvent used. Differential scanning calorimetry data indicated that the melting point of poly(tBuAH) increased from 61 to 89 °C with increasing f1,4 from 0.38 to 1.0, indicative of higher crystallinity of poly(tBuAH) composed of 1,4-unit. Preliminary steady-state fluorescence study indicated that all the poly(tBuAH) samples of different f1,4 emitted weak but significant fluorescence in DMF. The maximum of fluorescence band shifted from ca. 350 to ca. 450 nm with varying the excitation wavelength from 300 to 400 nm.

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