A Study of Cooperative Phenyl Ring Flip Motions in Glassy Polystyrene by Molecular Simulations

Khare, Rajesh; Paulaitis, Michael E.

doi:10.1021/ma00117a018

Cited by 35 publications

(36 citation statements)

References 13 publications

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“…0.23-226.5 kcal mol 1 1 kcal D 4.184 kJ ]. 43 In a folded peptide structure, rotation of the 4F-Phg side-chain may be restricted to different degrees, depending on the environment. As illustrated by Fig.…”

Section: Aspects Of Molecular Mobilitymentioning

confidence: 99%

‘Boomerang’‐like insertion of a fusogenic peptide in a lipid membrane revealed by solid‐state ¹⁹F NMR

Afonin¹,

Dürr²,

Gläser³

et al. 2004

Magnetic Reson in Chemistry

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Solid state (19)F NMR revealed the conformation and alignment of the fusogenic peptide sequence B18 from the sea urchin fertilization protein bindin embedded in flat phospholipid bilayers. Single (19)F labels were introduced into nine distinct positions along the wild-type sequence by substituting each hydrophobic amino acid, one by one, with L-4-fluorophenylglycine. Their anisotropic chemical shifts were measured in uniaxially oriented membrane samples and used as orientational constraints to model the peptide structure in the membrane-bound state. Previous (1)H NMR studies of B18 in 30% TFE and in detergent micelles had shown that the peptide structure consists of two alpha-helical segments that are connected by a flexible hinge. This helix-break-helix motif was confirmed here by the solid-state (19)F NMR data, while no other secondary structure (beta-sheet, 3(10)-helix) was compatible with the set of orientational constraints. For both alpha-helical segments we found that the helical conformation extends all the way to the respective N- and C-termini of the peptide. Analysis of the corresponding tilt and azimuthal rotation angles showed that the N-terminal helix of B18 is immersed obliquely into the bilayer (at a tilt angle tau approximately 54 degrees), whereas the C-terminus is peripherally aligned (tau approximately 91 degrees). The azimuthal orientation of the two segments is consistent with the amphiphilic distribution of side-chains. The observed 'boomerang'-like mode of insertion into the membrane may thus explain how peptide binding leads to lipid dehydration and acyl chain perturbation as a prerequisite for bilayer fusion to occur.

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Section: Aspects Of Molecular Mobilitymentioning

confidence: 99%

‘Boomerang’‐like insertion of a fusogenic peptide in a lipid membrane revealed by solid‐state ¹⁹F NMR

Afonin¹,

Dürr²,

Gläser³

et al. 2004

Magnetic Reson in Chemistry

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“…Studies of the energy activation due to phenyl group rotation in polystyrene are in the range between 10 and 20 kcal/mol. [23][24][25][26][27] Molecular mechanics studies of phenyl ring flip motion in single chains of polystyrene indicates that the transition is due to a cooperative movement of Figure 6 Contour plot of the activation energy for the arelaxation, DH a , as function of the total crosslink density and the percentage of monosulphide linkages in the compound. the phenyl ring at the chain backbone.…”

Section: Resultsmentioning

confidence: 99%

“…The resistance to the phenyl group rotation depends on the conformation of the polymer backbone. [25][26][27] It is known that both high cis 1,4-polybutadiene and high trans 1,4-polybutadiene isomerise with heat in presence of elemental sulphur. 28 As it was mention previously, the chemical structure of butadiene in the used SBR consists of 55% trans-1,4, 9.5% cis-1,4, and 12% 1,2-butadiene.…”

Section: Resultsmentioning

confidence: 99%

About the activation energies of the main and secondary relaxations in cured styrene butadiene rubber

Ghilarducci

Salva

Marzocca

2009

J of Applied Polymer Sci

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This article studies the influence of the network structure on the activation energies of the a and b relaxations in vulcanized styrene butadiene rubber, SBR. A cure system based on sulphur and TBBS (N-t-butyl-2-benzothiazole sulfenamide) was used in the formulation of several compounds cured at 433 K. The activation energies were evaluated from internal friction (loss tangent) data of the compounds using an automated subresonant forced pendulum in a wide frequency range and between 80 K and 273 K. The internal friction data of the samples reveal two transitions, a and b, characterized by the temperatures T a and T b , due to the glass transition and the phenyl group rotation of the copolymer, respectively. Although T a increases at higher crosslink density, it shows also a dependence with the amount of polysulphide and monosulphide linkages present in the samples. The highest activation energy for this process is obtained for the samples with high crosslink density and 30% of monosulphides in this structure. In the case of the b-relaxation, there is a pronounced change in the activation energy between the uncured and the cured samples. The type of structure formed during vulcanization has an important effect in the activation energy of the segmental mode-process. In the case of the b-process, the cis-trans isomerization that takes place during vulcanization in the butadiene part of the SBR, might be the cause of conformational changes in the surrounding of the phenyl rings that affect the energy barrier associated to the phenyl rotation.

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“…In the particular case of polystyrene (PS) of interest here, T f was found to be 175 ± 25 K [3] and 200 K [4]. For PS the onset of the fast motion has been ascribed to the change of the librational dynamics of the side-chain phenyl ring [3,4] with expected involvement of the main-chain through the connecting bonds [12,13]. According to Nuclear Magnetic Resonance (NMR) the flip motion becomes frozen at about 190 K [14].…”

Section: Introductionmentioning

confidence: 84%

Signatures of the fast dynamics in glassy polystyrene by multi-frequency, high-field electron paramagnetic resonance of molecular guests

Bercu

Martinelli

Massa

et al. 2006

Journal of Non-Crystalline Solids

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A Study of Cooperative Phenyl Ring Flip Motions in Glassy Polystyrene by Molecular Simulations

Cited by 35 publications

References 13 publications

‘Boomerang’‐like insertion of a fusogenic peptide in a lipid membrane revealed by solid‐state ¹⁹F NMR

‘Boomerang’‐like insertion of a fusogenic peptide in a lipid membrane revealed by solid‐state ¹⁹F NMR

About the activation energies of the main and secondary relaxations in cured styrene butadiene rubber

Signatures of the fast dynamics in glassy polystyrene by multi-frequency, high-field electron paramagnetic resonance of molecular guests

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A Study of Cooperative Phenyl Ring Flip Motions in Glassy Polystyrene by Molecular Simulations

Cited by 35 publications

References 13 publications

‘Boomerang’‐like insertion of a fusogenic peptide in a lipid membrane revealed by solid‐state 19F NMR

‘Boomerang’‐like insertion of a fusogenic peptide in a lipid membrane revealed by solid‐state 19F NMR

About the activation energies of the main and secondary relaxations in cured styrene butadiene rubber

Signatures of the fast dynamics in glassy polystyrene by multi-frequency, high-field electron paramagnetic resonance of molecular guests

Contact Info

Product

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About

‘Boomerang’‐like insertion of a fusogenic peptide in a lipid membrane revealed by solid‐state ¹⁹F NMR

‘Boomerang’‐like insertion of a fusogenic peptide in a lipid membrane revealed by solid‐state ¹⁹F NMR