Carbon-13 nuclear magnetic resonance measurements of local segmental dynamics of polyisoprene in dilute solution: nonlinear viscosity dependence

Głowinkowski, S.; Gisser, Daniel J.; Ediger, M. D.

doi:10.1021/ma00216a021

Cited by 72 publications

(107 citation statements)

References 20 publications

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“…For D72R1 T4L, the activation barrier was determined to be due solely to the activation barrier of viscous flow of the 30% sucrose solution (10). Although the activation energy for viscous flow in the interior of the OG micelle is not known, the activation energy for viscous flow was determined to be 2.2 and 3.6 kcal mol −1 for toluene and n-hexadecane, respectively (51), and 3.8 kcal mol −1 in hexadecyltrimethylammonium chloride (CTACl) micelles (52), similar to values measured here.…”

Section: Discussionsupporting

confidence: 68%

Structural Origins of Nitroxide Side Chain Dynamics on Membrane Protein α-Helical Sites,

Kroncke¹,

Horanyi²,

Columbus³

2010

Biochemistry

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Understanding the structure and dynamics of membrane proteins in their native, hydrophobic environment is important to understanding how these proteins function. EPR spectroscopy in combination with site directed spin labeling (SDSL) can measure dynamics and structure of membrane proteins in their native lipid environment; however, until now the dynamics measured have been qualitative due to limited knowledge of the nitroxide spin label's intramolecular motion in the hydrophobic environment. Although several studies have elucidated the structural origins of EPR lineshapes of water-soluble proteins, EPR spectra of nitroxide spin labeled proteins in detergents or lipids have characteristic differences from their water-soluble counterparts suggesting significant differences in the underlying molecular motion of the spin label between the two environments. To elucidate these differences, membrane exposed α-helical sites of the leucine transporter, LeuT, from A. aeolicus, were investigated using X-ray crystallography, mutational analysis, nitroxide side chain derivatives, and spectral simulations in order to obtain a motional model of the nitroxide. For each crystal structure, the nitroxide ring of a disulfide-linked spin label side chain (R1) is resolved and makes contacts with hydrophobic residues on the protein surface. The spin label at site I204 on LeuT makes a non-traditional hydrogen bond with the ortho hydrogen on its nearest neighbor F208, whereas the spin label at site F177 makes multiple van der Waals contacts with a hydrophobic pocket formed with an adjacent helix. These results coupled with the spectral effect of mutating the i ± 3, 4 residues suggest that the spin label has a greater affinity for its local protein environment in the low dielectric than on a water-soluble protein surface. The simulations of the EPR spectra presented here suggest the spin label oscillates about the terminal bond nearest the ring while maintaining weak contact with the protein surface. Combined, the results provide a starting point for determining a motional model for R1 on membrane proteins allowing quantification of nitroxide dynamics in the aliphatic environment of detergent and lipids. In addition, initial contributions to a rotamer library of R1 on membrane proteins are provided, which will assist in reliably modeling the R1 conformational space for pulsed dipolar EPR and NMR paramagnetic relaxation enhancement distance determination.Site directed spin labeling (SDSL) is a powerful method uniquely suited for investigating structure and dynamics of soluble and membrane proteins of arbitrary molecular weight (1-9). In SDSL, a radical containing nitroxide spin label is site specifically introduced into a protein (e.g., selectively reacted with the free sulfhydryl of a single cysteine). The most Supporting Information: Two tables containing theoretical fit ranges and parameters and further details of background EPR signal and structural influences of EPR spectra. The supplemental materials may be accessed free of ...

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Section: Discussionsupporting

confidence: 68%

Structural Origins of Nitroxide Side Chain Dynamics on Membrane Protein α-Helical Sites,

Kroncke¹,

Horanyi²,

Columbus³

2010

Biochemistry

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“…[7][8][9][10][11][12][13][14] These motions have been studied within dilute polymer solutions as a function of solvent viscosity using thermodynamically good solvents where the dynamics are observed to scale by a fractional power of solvent viscosity, . 5,14 This violates a hydrodynamic scaling prediction that the dynamics would scale by to the first power and is attributed to the overlap of the time scales for local polymer dynamics and solvent reorientation. Within the melt, short length scale polymer dynamics become an essential mode of relaxation since chain congestion and chain entanglement create an enormous frictional resistance to large-scale reorientational motion of the polymer backbone.…”

Section: Introductionmentioning

confidence: 82%

An investigation into the local segmental dynamics of polyethylene: An isothermal/isobaric molecular dynamics study

Hotston

Adolf

Karatasos

2001

The Journal of Chemical Physics

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Molecular dynamics simulations of unentangled linear polyethylene melts have been performed for systems composed of 10 chains of 100 united atoms over a pressure range of 1 to 5000 bar and a temperature range of 375 to 475 K. Transition rates, activation volumes, and activation energies are in good agreement with values from similar simulations quoted in literature for systems well above T g . Second-neighbor torsional angle coupling is observed to increase with increasing pressure and decreasing temperature. The lifetime of this coupling between conformational events is presented for the first time. Geometric autocorrelation functions are analyzed in terms of their distribution of relaxation times and reveal a process on the time scale of a few picoseconds and another on the time scale of a few nanoseconds. An intermediate process develops between these two time scales at high pressure and low temperature.

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“…Secondly, Glowinkowski et al 7 reported the local segmental dynamics of PI with cis-1,4 content= 70-80% by 13 C NMR. They also used the solvents in a wide viscosity range.…”

Section: The Activation Energy For Cis-pimentioning

confidence: 99%

Local Chain Dynamics of Poly(cis-1,4-isoprene) in Dilute Solutions Studied by the Fluorescence Depolarization Method

Ono

Ueda

Yamamoto

1994

Polym J

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ABSTRACT:Local segmental motions of poly(cis-1,4-isoprene) (cis-PI) labeled with anthracene were examined by the method of fluorescence depolarization using 1,4-dioxane, n-dodecane, cyclohexane, benzene, ethylbenzene, and a-xylene as the solvents with a viscosity of less than 2 cP. The anisotropy ratio was measured in these dilute solutions, and the mean relaxation time, Tm, for the chain local motion was obtained. The activation energy, E*, was obtained by using the theory of Kramers' diffus10n limit. The reduced relaxation time, Tm/I/, for cis-PI was much shorter than that for polystyrene and was independent of the local segment density differing from that of polystyrene. The dependence of activation energy, E*, on the solvent was very weak, compared to that of polystyrene. These findings could be interpreted in terms of the dynamic flexibility of the polymer chain.

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Carbon-13 nuclear magnetic resonance measurements of local segmental dynamics of polyisoprene in dilute solution: nonlinear viscosity dependence

Cited by 72 publications

References 20 publications

Structural Origins of Nitroxide Side Chain Dynamics on Membrane Protein α-Helical Sites,

Structural Origins of Nitroxide Side Chain Dynamics on Membrane Protein α-Helical Sites,

An investigation into the local segmental dynamics of polyethylene: An isothermal/isobaric molecular dynamics study

Local Chain Dynamics of Poly(cis-1,4-isoprene) in Dilute Solutions Studied by the Fluorescence Depolarization Method

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