Chain Conformations

Abe, Akihiro

doi:10.1016/b978-0-08-096701-1.00039-2

Cited by 5 publications

(2 citation statements)

References 80 publications

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“…Accumulation of various experimental evidences suggest that the side-chain conformation may play a key role in triggering such transitions. Examples are abundantly known for conventional polymers in which the conformational asymmetry involved in the side chain largely affects the spatial configuration of the skeletal chain. − In an asymmetric polymer, the side-chain conformation varies more or less with the configuration of the main chain. Since bond conformations are often neighbor dependent along the polymer chain, small free energy differences accumulated in the individual side chains may become a driving force for a large deformation of the skeletal chain. ,, Since helical polypeptides are regularly hydrogen bonded, the screw-sense inversion inevitably occurs in a highly cooperative fashion.…”

Section: Discussionmentioning

confidence: 99%

“…Examples are abundantly known for conventional polymers in which the conformational asymmetry involved in the side chain largely affects the spatial configuration of the skeletal chain. [25][26][27][28] In an asymmetric polymer, the sidechain conformation varies more or less with the configuration of the main chain. Since bond conformations are often neighbor dependent along the polymer chain, small free energy differences accumulated in the individual side chains may become a driving force for a large deformation of the skeletal chain.…”

Section: Discussionmentioning

confidence: 99%

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Reversible Helix−Helix Transition of Poly(β-phenylpropyl l-aspartate) Involving a Screw-Sense Inversion in the Solid State

et al. 1996

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Poly(β-phenylpropyl l-aspartate) exhibits a novel helix−helix transition in the solid state at around 160 °C. The transition takes place reversibly in a narrow temperature range during a heating and cooling cycle, indicating that it is essentially of a first order. A combined use of circular dichroism, X-ray, and 13C CP/MAS NMR measurements revealed that the transition is due to an interconversion of the helical screw sense from a right-handed α-helix to a left-handed helix. An unwinding and rewinding of the helical screw occurs concertedly along the polypeptide backbone without disturbing the uniaxial orientation of the helix axes.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Reversible Helix−Helix Transition of Poly(β-phenylpropyl l-aspartate) Involving a Screw-Sense Inversion in the Solid State

et al. 1996

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Ionotropic crosslinking of sodium carboxymethylcellulose and sodium carboxymethylcellulose‐gelatin matrices and their erosion properties

Prasad

Kalyanasundaram

1993

J of Applied Polymer Sci

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SYNOPSISHydrophilic sodium carboxymethylcellulose ( NaCMC ) matrices were chemically modified into hydrophobic gels by ionotropic crosslinking with cupric or ferric ion under ambient temperature and pH. Insoluble matrices were also prepared using an interactive polymer gelatin in combination with NaCMC. These matrices underwent erosion at the crosslinks, followed by matrix erosion when released in water. The matrix erosion in water was influenced by the gelling agent, initial crosslinker density, and gelatin content in the insolubilized matrices. The apparent diffusion coefficients of fenthion ranged from 7.2 X lo-' to 175.6 X cm*/sec, with matrices prepared under different conditions. These erosion-controlled matrices can be used for the controlled release of various biologically active agents. 0 1993

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Spatial configuration of chain molecules incorporated in liquid crystals and thermodynamic significance

Abe

1997

Macromolecular Symposia

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The ccmtormation ol chain molecules participating variously in the lormation of liquid crystalline mesophase has been elucidated Two examples are mentioned (1) the side chain llanhmg the a-helical bachbone ol polypeptides, and (3) the spacer joining mesogenic units in mainchain liquid crystals thermodynamic properties of these systems Flexible segments play an imporant role in determining Chain molecules comprising flexible or semillexible units normally assume a vanety of spatial configurations. The most well-known arrangement is either one of the two extremes. The one is the ordered conlormation Itkc in those encountered in the crystalline state. The other is the s-called "random-coil" conlormation in the state unperturbed by longrange intramolecular interactions. Mathematical treatment of the random-coil conformation has been greatly advanced since 1960's [l].Chain molecules are also often found in a variety of anisotropic media, where we can no longer disregard the environment as an isotropic continuum 121. Chain conformations may be anisotropic, involving long-range onentational correlations. Such conformations are generally unpredictable from the conventional RIS calculations. Recent advances in the deuterium NMR technique allow us to investigate conformational characteristics of cham molecules incorporated in liquid crystals [3]. The quadrupolar splittings arising from deuterium-substituted bonds bear information regarding the onentational order of given bonds averaged over all allowed conformations. In these several years, we have been trying to elucidate the conformation of chain molecules participating variously in the formation of liquid crystalline mesophase.Flexible chains often play a crucial role in determining thermodynamic properties of the system.(1) Sidechain conformation is the key to determine the a-Helical Screw- Sense of Polyaspartatesmutually isomenc in their chemical structures:Poly(p-phenethyl L-aspartate) (PPLA) and poly(y-benzyl L-glutamate) (PBLG) are

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Chain Conformations

Cited by 5 publications

References 80 publications

Reversible Helix−Helix Transition of Poly(β-phenylpropyl l-aspartate) Involving a Screw-Sense Inversion in the Solid State

Reversible Helix−Helix Transition of Poly(β-phenylpropyl l-aspartate) Involving a Screw-Sense Inversion in the Solid State

Ionotropic crosslinking of sodium carboxymethylcellulose and sodium carboxymethylcellulose‐gelatin matrices and their erosion properties

Spatial configuration of chain molecules incorporated in liquid crystals and thermodynamic significance

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