Helix-Sense Inversion in Polyaspartates

Sasaki, Shintaro; Ogawa, Hiroshi; Kimura, Shigeo S.

doi:10.1295/polymj.23.1325

Cited by 16 publications

(6 citation statements)

References 24 publications

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“…11 PBLA and its derivatives carrying a methyl or chloro substituent at the para position of the terminal aromatic residue are known to exhibit a screw-sense inversion from the righthanded R-helix to the left-handed ω-helix at around 150 °C. [12][13][14] Recently, one of the present authors has reported a helix-helix transformation of poly(L-aspartic acid ester) with long n-alkyl side chains (R ) (CH 2 ) n H, n ) 12-18) at around 150 °C. 15 In all these examples, however, the transition is observed only on heating and the high-temperature form remains unchanged on cooling.…”

Section: Introductionmentioning

confidence: 88%

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: Introductionmentioning

confidence: 88%

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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“…In 1991, Sasaki et al described the solid-state inversion of helicity in thin films of poly(β-(pchlorobenzyl)-L-aspartate) and poly(β-(p-methylbenzyl)-L-aspartate) prepared by drop casting from a CHCl 3 solution: an inversion of the ECD band at 230 nm was observed for both samples after thermal annealing at 180−220 °C, thus revealing an irreversible transition from a right-handed α-helix to a lefthanded ω-helix (further confirmed by X-ray diffraction analysis). 498 Cho and co-workers reported a comparison of the ECD properties for drop-casted films and Langmuir− Blodgett layers of poly(γ-benzyl-L-glutamate)/poly(propylene oxide) 499 and of poly(γ-benzyl-L-glutamate)/poly(ethylene oxide)/poly(γ-benzyl-L-glutamate) 500 block copolymers, show- ing different degrees of orientation depending on the length of polyether blocks. Structural properties of drop-casted thin films of poly(L-glutamic acid) derivatives with aromatic 501 and azobenzene 502 groups as side-chain chromophores, as well as poly(L-glutamine)s bearing pyrene chromophores in the side chains, 503 have also been studied through ECD.…”

Section: Ecd In Thin Films Of π-Conjugated Oligomers and Polymersmentioning

confidence: 99%

“…Here, we will briefly discuss only oligo- and polypeptides with π-conjugated moieties in side chains, which have been investigated only more recently. In 1991, Sasaki et al described the solid-state inversion of helicity in thin films of poly(β-( p -chlorobenzyl)- l -aspartate) and poly(β-( p -methylbenzyl)- l -aspartate) prepared by drop casting from a CHCl 3 solution: an inversion of the ECD band at 230 nm was observed for both samples after thermal annealing at 180–220 °C, thus revealing an irreversible transition from a right-handed α-helix to a left-handed ω-helix (further confirmed by X-ray diffraction analysis) . Cho and co-workers reported a comparison of the ECD properties for drop-casted films and Langmuir–Blodgett layers of poly(γ-benzyl- l -glutamate)/poly(propylene oxide) and of poly(γ-benzyl- l -glutamate)/poly(ethylene oxide)/poly(γ-benzyl- l -glutamate) block copolymers, showing different degrees of orientation depending on the length of polyether blocks.…”

Section: Ecd Properties In Thin Films Of π-Conjugated Systems: Litera...mentioning

confidence: 99%

Chiroptical Properties in Thin Films of π-Conjugated Systems

2020

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Chiral π-conjugated molecules provide new materials with outstanding features for current and perspective applications, especially in the field of optoelectronic devices. In thin films, processes such as charge conduction, light absorption, and emission are governed not only by the structure of the individual molecules but also by their supramolecular structures and intermolecular interactions to a large extent. Electronic circular dichroism, ECD, and its emission counterpart, circularly polarized luminescence, CPL, provide tools for studying aggregated states and the key properties to be sought for designing innovative devices. In this review, we shall present a comprehensive coverage of chiroptical properties measured on thin films of organic π-conjugated molecules. In the first part, we shall discuss some general concepts of ECD, CPL, and other chiroptical spectroscopies, with a focus on their applications to thin film samples. In the following, we will overview the existing literature on chiral π-conjugated systems whose thin films have been characterized by ECD and/or CPL, as well other chiroptical spectroscopies. Special emphasis will be put on systems with large dissymmetry factors (g abs and g lum) and on the application of ECD and CPL to derive structural information on aggregated states.

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“…Poly(β‐ p ‐chlorobenzyl L ‐aspartate) (PClBLA) is one of the well‐studied polyaspartate derivatives in both solution and the solid state 29–35. The chemical structure of PClBLA differs from those of PBLA and PPLA only at the terminal of the relatively long side chain.…”

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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Helix-Sense Inversion in Polyaspartates

Cited by 16 publications

References 24 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

Chiroptical Properties in Thin Films of π-Conjugated Systems

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

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