Reversible Screw-Sense Inversion of α-Helical Poly(β-phenethyl aspartate) in the Solid State

Okamoto, Satoshi; Furuya, Hidemine; Watanabe, Junji; Abe, Akihiro

doi:10.1295/polymj.28.41

Cited by 12 publications

(9 citation statements)

References 26 publications

(16 reference statements)

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“…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. Essentially the same mechanism has been presented for the thermally induced helix−helix inversion observed for a racemic mixture comprising PPLA and PPDA in the solid state …”

Section: Discussionmentioning

confidence: 65%

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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: 65%

“…Essentially the same mechanism has been presented for the thermally induced helix-helix inversion observed for a racemic mixture comprising PPLA and PPDA in the solid state. 29…”

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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“…The latter behavior IS widely known ils a characteristic o l poly(aspartic acid ester)s [7]. A pseudo first-order transition between the two tx-helical regimes has been observed for PPLA under various conditions such as in a dilute isotropic solution, in a moderately concentrated liquid-crystallme (LC) phase, as well as in the bulk solid state [6,8]. The transition behaviors are schematically illustratcd in Fig.1, wherc experimental techniques used to identify the helix-sense inversion are also included [ 6 ] .…”

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confidence: 99%

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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“…In our series of papers,20–24 we have carried out detailed studies on the intramolecular helix–helix transitions of poly(β‐phenethyl L ‐aspartatate) (PPLA) in various states such as a dilute isotropic, a moderately concentrated liquid crystalline (LC), and the solid phase. In a ternary solution containing a denaturant organic acid as a component, PPLA possibly exhibits transformation of the α‐helix sense in the order left → right → left as a function of temperature.…”

Section: Introductionmentioning

confidence: 99%

Three‐dimensional EPR/NMR image coregistration using a MATLAB‐based software

Ohfuchi

Goodwin

Fujii

et al. 2011

Concepts Magn Reson

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ABSTRACT:The coregistration of electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) images in three-dimensional (3D) data space typically involves a process of visual inspection and manual alignment of the images. This is due primarily to the use of separate scanners, which can result in a number of potential differences between the two image types, such as resolution, field-of-view, and image orientation. In this article, we describe recently developed methodology and software that enables automatic coregistration of EPR and NMR acquired images without the need for manual alignment. The technique requires the use of fiducial markers during both EPR and NMR image acquisition, which contain a solution of free radical spin probes, and allow adjustment of the positions and the fields-of-view of the measured images. In this work we present results for EPR/NMR image coregistration using an isoflurane-anesthetized mouse, injected with triarylmethyl radical (Oxo63) spin probes. The same spin probes were also used inside the fiducial markers and in plastic tubes used for phantom measurements. Using our MATLAB-based software, we were able to successfully coregister EPR/NMR images in approximately 60 s.

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Reversible Screw-Sense Inversion of α-Helical Poly(β-phenethyl aspartate) in the Solid State

Cited by 12 publications

References 26 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

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

Three‐dimensional EPR/NMR image coregistration using a MATLAB‐based software

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