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Optical Activity of Homochiral Polyamides in Solution and Solid State: Structural Function for Chiral Induction.

ABSTRACT: In this work, we have explored a simple and facile approach to prepare optically active helical polyamides. The hydroxyl groups of l-TA and d-TA were protected by O-alkoyl ester, and the resulting enantiomers, l-2,3-di-O-acetyl-tartaric acid (l-ATA) and d-2,3-di-O-acetyl-tartaric acid (d-ATA) crystals, were obtained. A pair of aliphatic homochiral polyamides of PA-l and PA-d are prepared using l-ATA, d-ATA, and achiral 1,11-undecanediamine as building blocks via interfacial polycondensation. PA-l and PA-d display negative and positive mirror circular dichroism (CD) spectra images in both solution and solid state. Moreover, the polyamides in solid state display different CD signals and stronger optical activity compared to those in ethanol and even the related chiral monomers in solid state, which was due to the helical conformation of the polyamides in solid state. Scanning electron microscopy results indicated that the aggregations of PA-l express left-handed helical sense, whereas those of PA-d express right-handed helix. In addition, the induced CD signals from the chiral conformation of the backbone become weaker when increasing the temperature from 0 to 60 °C in dilute solution. Either of the polyamides displays relatively stable CD images in solid state when elevating the temperature from 0 to 90 °C.

SUBMITTER: Zhang L

PROVIDER: S-EPMC6641245 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Optical Activity of Homochiral Polyamides in Solution and Solid State: Structural Function for Chiral Induction.

Zhang Lingli L Zhang Chenxi C Zhang Wenjie W Cui Zhe Z Fu Peng P Liu Minying M Pang Xinchang X Zhao Qingxiang Q

ACS omega 20180228 2

In this work, we have explored a simple and facile approach to prepare optically active helical polyamides. The hydroxyl groups of l-TA and d-TA were protected by O-alkoyl ester, and the resulting enantiomers, l-2,3-di-O-acetyl-tartaric acid (l-ATA) and d-2,3-di-O-acetyl-tartaric acid (d-ATA) crystals, were obtained. A pair of aliphatic homochiral polyamides of PA-l and PA-d are prepared using l-ATA, d-ATA, and achiral 1,11-undecanediamine as building blocks via interfacial ...[more]

PMID: 31458541

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Project description:Atomic-level structural information on alphaB-Crystallin (alphaB), a prominent member of the small heat-shock protein family, has been a challenge to obtain due its polydisperse oligomeric nature. We show that magic-angle spinning solid-state NMR can be used to obtain high-resolution information on an approximately 580-kDa human alphaB assembled from 175-residue 20-kDa subunits. An approximately 100-residue alpha-crystallin domain is common to all small heat-shock proteins, and solution-state NMR was performed on two different alpha-crystallin domain constructs isolated from alphaB. In vitro, the chaperone-like activities of full-length alphaB and the isolated alpha-crystallin domain are identical. Chemical shifts of the backbone and C(beta) resonances have been obtained for residues 64-162 (alpha-crystallin domain plus part of the C-terminus) in alphaB and the isolated alpha-crystallin domain by solid-state and solution-state NMR, respectively. Both sets of data strongly predict six beta-strands in the alpha-crystallin domain. A majority of residues in the alpha-crystallin domain have similar chemical shifts in both solid-state and solution-state, indicating similar structures for the domain in its isolated and oligomeric forms. Sites of intersubunit interaction are identified from chemical shift differences that cluster to specific regions of the alpha-crystallin domain. Multiple signals are observed for the resonances of M68 in the oligomer, identifying the region containing this residue as existing in heterogeneous environments within alphaB. Evidence for a novel dimerization motif in the human alpha-crystallin domain is obtained by a comparison of (i) solid-state and solution-state chemical shift data and (ii) (1)H-(15)N heteronuclear single quantum coherence spectra as a function of pH. The isolated alpha-crystallin domain undergoes a dimer-monomer transition over the pH range 7.5-6.8. This steep pH-dependent switch may be important for alphaB to function optimally (e.g., to preserve the filament integrity of cardiac muscle proteins such as actin and desmin during cardiac ischemia, which is accompanied by acidosis).

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Optical Activity of Homochiral Polyamides in Solution and Solid State: Structural Function for Chiral Induction.

Publications

Optical Activity of Homochiral Polyamides in Solution and Solid State: Structural Function for Chiral Induction.

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