A series of poly-β-benzyl-l-aspartate-co-poly-β-phenethyl-l-aspartates varying in their copolymer composition as well as with selectively introduced deuterium labels in the backbone or the side-chain ...were synthesized and their temperature-dependent conformation and orientation with respect to an external magnetic field were characterized by measuring 2H quadrupolar splittings nuclear magnetic resonance (NMR) spectroscopy and circular dichroism. All copolymers demonstrate a temperature-dependent change of their helical conformation from right-handed to left-handed (helix reversal) and a change of their alignment from perpendicular to parallel with respect to the magnetic field in an anisotropic solution (helix realignment) at different temperatures. Both effects react differently to a change of copolymer composition, but are concentration, dispersity, and molecular weight independent as well as unaffected by the initiator used for polymerization. The helix realignment by 90° in a magnetic field has not been observed previously for these copolyaspartates. Its existence is proven directly by measurement of the quadrupolar splitting of the specifically labeled polymers and comparison to calculated quadrupolar splittings. Furthermore, the temperature of both transitions was found to be dependent on deuteration at the N-position. The uncovering of the thermo and magnetoresponsiveness will lead to an improved understanding and application scope of the copolyaspartates (e.g., in their use as alignment media in NMR spectroscopy).
The application of anisotropic parameters in NMR-spectroscopy enables the acquisition of spatial and angular information, complementary to those from conventional isotropic NMR-measurements. The use ...of alignment media is a well-established method for inducing anisotropy. PBPMLG is a recently discovered polyglutamate-based alignment medium, exhibiting thermoresponsive behavior in the lyotropic liquid crystalline (LLC) phase, thus offering potential for deeper understanding of the alignment process. We present one approach for investigating the thermoresponsive behavior by synthesizing specifically deuterated PBPMLG-isotopologues and their subsequent analyses using
H NMR-spectroscopy. It was possible to relate the observed thermoresponsive behavior to a flip of the polymer with respect to the external magnetic field-an effect never observed before in glutamate-based polymeric alignment media. Furthermore, a solvent-induced temperature dependent gelation was verified in THF, which might provide yet another opportunity to manipulate the properties of this alignment medium in the future.
The application of anisotropic parameters in NMR‐spectroscopy enables the acquisition of spatial and angular information, complementary to those from conventional isotropic NMR‐measurements. The use ...of alignment media is a well‐established method for inducing anisotropy. PBPMLG is a recently discovered polyglutamate‐based alignment medium, exhibiting thermoresponsive behavior in the lyotropic liquid crystalline (LLC) phase, thus offering potential for deeper understanding of the alignment process. We present one approach for investigating the thermoresponsive behavior by synthesizing specifically deuterated PBPMLG‐isotopologues and their subsequent analyses using 2H NMR‐spectroscopy. It was possible to relate the observed thermoresponsive behavior to a flip of the polymer with respect to the external magnetic field—an effect never observed before in glutamate‐based polymeric alignment media. Furthermore, a solvent‐induced temperature dependent gelation was verified in THF, which might provide yet another opportunity to manipulate the properties of this alignment medium in the future.
Deuterated isotopologues of a thermoresponsive, glutamate‐based alignment medium have been synthesized and investigated by 2H NMR‐spectroscopy, vibrating sample magnetometry and polarized optical microscopy. The measurements show a flip of the polymeric α‐helix in lyotropic liquid crystalline phase, providing further insights into the alignment process of the polymer inside the magnetic field.
The application of anisotropic parameters in NMR‐spectroscopy enables the acquisition of spatial and angular information, complementary to those from conventional isotropic NMR‐measurements. The use ...of alignment media is a well‐established method for inducing anisotropy. PBPMLG is a recently discovered polyglutamate‐based alignment medium, exhibiting thermoresponsive behavior in the lyotropic liquid crystalline (LLC) phase, thus offering potential for deeper understanding of the alignment process. We present one approach for investigating the thermoresponsive behavior by synthesizing specifically deuterated PBPMLG‐isotopologues and their subsequent analyses using 2H NMR‐spectroscopy. It was possible to relate the observed thermoresponsive behavior to a flip of the polymer with respect to the external magnetic field—an effect never observed before in glutamate‐based polymeric alignment media. Furthermore, a solvent‐induced temperature dependent gelation was verified in THF, which might provide yet another opportunity to manipulate the properties of this alignment medium in the future.
Deuterated isotopologues of a thermoresponsive, glutamate‐based alignment medium have been synthesized and investigated by 2H NMR‐spectroscopy, vibrating sample magnetometry and polarized optical microscopy. The measurements show a flip of the polymeric α‐helix in lyotropic liquid crystalline phase, providing further insights into the alignment process of the polymer inside the magnetic field.
Residual dipolar couplings (RDCs) offer great potential in modern structure elucidation of organic compounds. Current developments focus on “smart” alignment media, which are able to change the ...induced alignment via external stimuli to enable de novo structure elucidation. We recently introduced poly-γ-p-biphenylmethyl-l-glutamate (PBPMLG) as a thermoresponsive alignment medium with outstanding enantiodiscriminating properties. In this work we present PBPMLG derivates containing spacer groups, separating the biphenyl mesogene of the side chain from the α-helical backbone, with the aim of better understanding the underlying effects and potentially inducing further orientations. Two thermoresponsive effects were observed separately: first, the 90° reorientation of the helix with respect to the external magnetic field and, second, a gelation of the LLC phase. The thermoresponsive gelation has been thoroughly investigated via NMR, polarized optical microscopy, and rheometry. We discuss the implication of the effects observed on RDC-based structure elucidation protocols.
Abstract
The application of anisotropic parameters in NMR‐spectroscopy enables the acquisition of spatial and angular information, complementary to those from conventional isotropic NMR‐measurements. ...The use of alignment media is a well‐established method for inducing anisotropy. PBPMLG is a recently discovered polyglutamate‐based alignment medium, exhibiting thermoresponsive behavior in the lyotropic liquid crystalline (LLC) phase, thus offering potential for deeper understanding of the alignment process. We present one approach for investigating the thermoresponsive behavior by synthesizing specifically deuterated PBPMLG‐isotopologues and their subsequent analyses using
2
H NMR‐spectroscopy. It was possible to relate the observed thermoresponsive behavior to a flip of the polymer with respect to the external magnetic field—an effect never observed before in glutamate‐based polymeric alignment media. Furthermore, a solvent‐induced temperature dependent gelation was verified in THF, which might provide yet another opportunity to manipulate the properties of this alignment medium in the future.
The physical, endocrine, and metabolic responses of livestock to road transport have been evaluated by conventional hematological and biochemistry parameters for more than 20 years. However, these ...measures are relatively insensitive to subtle metabolic adaptations. We applied NMR-based metabonomics to assess system-wide metabolic responses as expressed in urine and serum of a large cohort of animals (n = 80) subjected to 12 and 48 h road transport. The profiling of 1H NMR spectra revealed that the transported animals experienced altered gut and energy metabolism, muscle catabolism, and possibly a renal response. The animals transported for 48 h exhibited a deeper metabolic response to the transport event and a complex and expanded metabolic trajectory over the 72 h recovery period. Intriguingly, excretion of acyl glycines and a dicarboxylic acid was observed after transport and during recovery, implicating peroxisomal fatty acid oxidation as a metabolic response to transport-induced stress.
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