scholarly journals Unfolding of Helical Poly(L-Glutamic Acid) in N,N-Dimethylformamide Probed by Pyrene Excimer Fluorescence (PEF)

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1690
Author(s):  
Weize Yuan ◽  
Remi Casier ◽  
Jean Duhamel
Keyword(s):  
Glutamic Acid ◽  
Local Density ◽  
Guanidine Hydrochloride ◽  
Racemic Mixture ◽  
Excimer Fluorescence ◽  
Excimer Formation ◽  
Blob Model ◽  
Α Helix ◽  
The Relationship ◽  
Pyrene Excimer Formation

The denaturation undergone by α–helical poly(L-glutamic acid) (PLGA) in N,N-dimethylformamide upon addition of guanidine hydrochloride (GdHCl) was characterized by comparing the fluorescence of a series of PLGA constructs randomly labeled with the dye pyrene (Py-PLGA) to that of a series of Py-PDLGA samples prepared from a racemic mixture of D,L-glutamic acid. The process of pyrene excimer formation (PEF) was taken advantage of to probe changes in the conformation of α–helical Py-PLGA. Fluorescence Blob Model (FBM) analysis of the fluorescence decays of the Py-PLGA and Py-PDLGA constructs yielded the average number (<Nblob>) of glutamic acids located inside a blob, which represented the volume probed by an excited pyrenyl label. <Nblob> remained constant for randomly coiled Py-PDLGA but decreased from ~20 to ~10 glutamic acids for the Py-PLGA samples as GdHCl was added to the solution. The decrease in <Nblob> reflected the decrease in the local density of PLGA as the α–helix unraveled in solution. The changes in <Nblob> with GdHCl concentration was used to determine the change in Gibbs energy required to denature the PLGA α–helix in DMF. The relationship between <Nblob> and the local density of macromolecules can now be applied to characterize the conformation of macromolecules in solution.

How switching the substituent of a pyrene derivative from a methyl to a butyl affects the fluorescence response of polystyrene randomly labeled with pyrene

2010 ◽  
Vol 88 (3) ◽  
pp. 217-227 ◽  
Author(s):  
Mark Ingratta ◽  
Manoj Mathew ◽  
Jean Duhamel
Keyword(s):  
Organic Solvents ◽  
Excellent Agreement ◽  
Fluorescence Spectra ◽  
Series Solutions ◽  
Specific Nature ◽  
Polymer Backbone ◽  
Excimer Fluorescence ◽  
Fluorescence Response ◽  
Different Types ◽  
Blob Model

A series of polystyrenes randomly labeled with 1-pyrenebutanol were prepared by copolymerizing styrene and 1-pyrenebutylacrylate yielding the CoBuE–PS series. Solutions of CoBuE–PS were prepared in nine organic solvents having viscosities ranging from 0.36 to 5.5 mPa·s and the fluorescence spectra and pyrene monomer and excimer fluorescence decays were acquired. Analysis of the fluorescence spectra yielded the IE/IM ratio, whereas analysis of the fluorescence decays with the fluorescence blob model (FBM) yielded the parameters N blobo , <kblob × Nblob> , and k blobo . These parameters were compared to those obtained with two other series of pyrene-labeled polystyrenes, which had been studied earlier, namely CoA–PS and CoE–PS where pyrene was attached to the polymer backbone via a methylamide and benzyl methylether linker, respectively. Although the parameters IE/IM, N blobo , <kblob × Nblob>, and k blobo took different values according to the specific nature of the linker connecting pyrene to the polystyrene backbone, they exhibited trends that were quite similar for all the pyrene-labeled polystyrene constructs. The excellent agreement between the parameters retrieved for the three different types of pyrene-labeled polystyrenes suggests that the FBM accounts satisfyingly for differences in the nature of the label used, while still retrieving information pertinent to the polymer of interest.

‘Excimer’ fluorescence I. Solution spectra of 1:2-benzanthracene derivatives

1963 ◽  
Vol 274 (1359) ◽  
pp. 552-564 ◽  
Keyword(s):  
Quantum Yield ◽  
Crystal Lattice ◽  
Excited States ◽  
Concentration Dependence ◽  
Fluorescence Spectra ◽  
Excimer Fluorescence ◽  
Relative Quantum Yield ◽  
Relative Quantum ◽  
Different Types ◽  
Excimer Formation

Observations have been made of the concentration dependence of the fluorescence spectra of solutions of 1:2-benzanthracene and fifteen of its hydrocarbon derivatives. All of the compounds, except the 9,10-dim ethyl derivative, exhibit dim er emission at higher concentrations. The lower excited states, 1 L b and 1 L a , satisfy Förster’s conditions for fluorescent dim er formation. The factors determining the relative quantum yield of excimer fluorescence are discussed. The different types of crystal fluorescence spectra shown by the compounds are explained in terms of excimer formation in the crystal lattice.

Physicochemical Studies of Conglutin γ, a Storage Globulin From Seeds of Lupinus angustifolius

1980 ◽  
Vol 7 (1) ◽  
pp. 1 ◽  
Author(s):  
RJ Blagrove ◽  
JM Gillespie ◽  
GG Lilley ◽  
EF Woods
Keyword(s):  
Molecular Weight ◽  
Guanidine Hydrochloride ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Optical Rotatory Dispersion ◽  
Sedimentation Equilibrium ◽  
Native Protein ◽  
Equilibrium Studies ◽  
Physicochemical Studies ◽  
Α Helix

Physicochemical studies are reported for conglutin �, the minor globulin isolated from seeds of L. angustifolius cv. Uniwhite. Isoelectric focusing of the native protein in polyacrylamide gel slabs resolved major and minor broad bands near pH 8.0 and 7.8 respectively. Following reduction of disulfide bonds with β-mercaptoethanol in 8 M urea, the smaller polypeptide chain of known sequence focused near pH 6.9 while the larger chain focused near pH 8.0. Sedimentation equilibrium studies showed that the major component in aqueous buffers at neutral pH is a hexamer of molecular weight 280 000 which dissociates to the monomer of molecular weight 47 000 at pH 4.8. The sequence molecular weight of the small subunit polypeptide is 16 517 [Elleman, T.C. (1977). Aust. J. Biol. Sci. 30, 33-45]. The molecular weights determined for the larger chain by sedimentation equilibrium or column chromatography in 6 M guanidine hydrochloride, and by dodecyl sulfate-polyacrylamide gel electrophoresis, were in the range 28 000-30 000. Optical rotatory dispersion and circular dichroism measurements have been used to establish the approximate proportions of α-helix (15%), β-structure (35%), β-turns (18%) and unordered regions (32%) in the native protein. The denaturation curve for guanidine hydrochloride and the proportions of α-helix (50%), β-turns (18%) and unordered regions (32%) in 80 % trifluoroethanol have been determined.

A MINIMAL SYNTHETIC MEDIUM SUPPORTING GROWTH OF A MICROCOCCUS SPECIES

1960 ◽  
Vol 6 (3) ◽  
pp. 251-256 ◽  
Author(s):  
I. J. McDonald
Keyword(s):  
Glutamic Acid ◽  
Aspartic Acid ◽  
Synthetic Medium ◽  
Ammonium Salts ◽  
Nutritional Requirements ◽  
Inorganic Sulphur ◽  
Relationship Of ◽  
The Relationship

Nutritional requirements of a Micrococcus species (M. freudenreichii, A.T.C.C. No. 407) were studied. The organism required glutamic acid, thiamine, biotin, magnesium, iron, and potassium for growth. Cells from such a synthetic medium were shown to contain methionine indicating that inorganic sulphur was used. Glutamic acid could not be replaced with glutamine (unheated), aspartic acid, asparagine, nor ammonium salts. The relationship of nutritional requirements of micrococci and staphylococci to classification is discussed.

Einfluß der Deuterierung auf die Excimerenkinetik des Pyrens

1976 ◽  
Vol 31 (8) ◽  
pp. 990-994
Author(s):  
Günther Heidt
Keyword(s):  
Partition Function ◽  
Rate Constants ◽  
Formation Rate ◽  
Kinetic Constants ◽  
Theoretical Expectation ◽  
Excimer Emission ◽  
Anomalous Effect ◽  
Excimer Formation ◽  
Pyrene Excimer Formation

AbstractThe effect of deuteration on all six photophysical and kinetic constants of pyrene excimer formation is investigated. The rate constants of monomer and excimer emission and the rate of dissociation of the excimer are not affected by deuteration. The increase of the radiationless deactivation of the monomer (anomalous effect) agrees with the theoretical expectation. The radiationless deactivation of the excimer at various temperatures shows no effect and therefore does not take place via the excimer triplet. The decrease of the excimer formation rate can be explained by the effect of deuteration on the partition function and hence on the entropy.

Excimer fluorescence - XI. Solvent-solute energy transfer

1968 ◽  
Vol 303 (1472) ◽  
pp. 85-95 ◽  
Keyword(s):  
Energy Transfer ◽  
Molecular Diffusion ◽  
Dissociation Rate ◽  
Excimer Fluorescence ◽  
Transfer Distance ◽  
Diffusion Migration ◽  
Benzene Toluene ◽  
Excimer Formation ◽  
Alkyl Benzenes

The rate parameters of solvent-solute energy transfer and of oxygen-solvent quenching have been determined for solutions of 2, 5-diphenyloxazole in benzene, toluene, p -xylene and mesitylene. The role of excited molecules and excimers in transfer to the solute molecules is considered in terms of the Voltz relations, which include the Förster critical transfer distance, the molecular diffusion coefficients, and the solvent excitation migration coefficient. It is proposed that the migration is due to excimer formation and dissociation, and that the energy transfer occurs by a diffusion/migration-controlled collisional process. Dilution of the solvent decreases the migration, but increases the transfer distance, so that the transfer efficiency remains practically constant. The excimer formation and dissociation rate parameters in the pure alkyl benzenes are evaluated.

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