Diffusional Behavior of Polypeptides in the Isotropic, Biphasic, and Liquid Crystalline Phases As Studied by the Pulse Field-Gradient Spin−Echo¹H NMR Method

Abstract

The self-diffusion coefficients (D) of R-helical poly(n-octadecyl L-glutamate) (POLG) and chloroform (CHCl3) as solvent in the isotropic, biphasic, and liquid crystalline phases were measured as a function of POLG concentration at 30°C by the pulse field-gradient spin-echo 1 H NMR method and the diffusion 1 H NMR imaging method, to elucidate diffusional behavior of the polypeptide and solvent. From the experimental results, it was found that the diffusion coefficient of POLG is largely decreased in going from the isotropic phase to the liquid crystalline phase, and in the biphasic phase two kinds of fast and small diffusion components with diffusion coefficients of ∼10 -6 and ∼10 -7 cm 2 /s, respectively, exist, which correspond to the isotropic and liquid crystalline regions, respectively. Further, it was found that in the liquid crystalline phase the diffusion coefficients of chloroform as solvent in the liquid crystalline phase in the directions parallel (D|) and perpendicular (D⊥) to the R-helical chain axis are different from each other and then D| is much larger than D⊥.

Polypeptides and 100 Years of Chemistry of α‐Amino Acid N‐Carboxyanhydrides

“…The diffusion coefficients, and thus, the mobility of the entire poly(g-octadecyl-l-Glu) helix were measured by means of the pulse-field-gradient spin-echo 1 H NMR method (PFG SE). [238] These measurements were conducted in chloroform solution at 30 8C in the isotropic phase, in a biphasic region, and in the cholesteric phase. The diffusion coefficient considerably decreased in this order, and the diffusion parallel to the a-helix axis was significantly higher than perpendicular.…”

Polypeptide und 100 Jahre Chemie der α‐Aminosäure‐N‐carboxyanhydride

“…Andererseits gelang es mit der PFGSE-1 H-NMR-Methode (pulse field-gradient spin-echo), [238] Diffusionskoeffizienten und somit die Beweglichkeit der gesamten Poly(g-octadecyl-l-Glu)-Helix zu messen. Diese Messungen wurden in Chloroform an isotropen, zweiphasigen und cholesterischen Lösungen durchgeführt.…”

Preparation and characterization of highly oriented poly(γ‐benzylL‐glutamate) networks and gels with long channels with micrometer‐scale diameters

“…Kishi et al14, 15 prepared PBLG gels in cholesteric and nematic liquid‐crystalline phases and then studied the properties of the obtained gels. In our previous works, it has been reported that a highly oriented PBLG gel can be prepared by the crosslinking reaction of highly oriented PBLG chains with a crosslinker in the magnetic field of an NMR magnet through the monitoring of the orientation of the PBLG chains with solid‐state static 13 C‐NMR;16 then, solvents and rodlike molecules in the PBLG gel anisotropically diffuse in the directions parallel and perpendicular to the α‐helix axis by a high‐field‐gradient NMR system 16–24. This shows that there exist long channels with small diameters of 15–20 Å in the highly oriented PBLG gel.…”