22 research outputs found
Molecular Assembly of Alkylated Fused Expanded Pyridinium for a Highly Conductive Anion-Exchange Membrane
Alkylated fused expanded pyridinium (CxFEP) with alkyl chain lengths (x) of 0, 6,
12, and
18 was newly synthesized and introduced into polymers as side chains
for anion-exchange membrane (AEM) applications. FEP is characterized
by a large π cation that offers weak electrostatic interactions
with anions such as hydroxide (OH–) ions and therefore
leads to high OH– conductivity in AEM. CxFEP shows a synergetic effect between the π–π
interactions of FEP and van der Waals interactions of the alkyl chains
and forms a strong assembly, particularly for C6FEP. On the other
hand, when CxFEP was introduced into the
polymers, C12FEP formed an ordered stacking assembly in
the films, whereas the other polymers with shorter (C0 and
C6) and longer (C18) alkyl chains exhibited
no such ordered structure. For the AEM, all of the polymers showed
higher ion conductivities than that of commercial ammonium-based AEM,
even with their low ion-exchange capacities (IEC), probably because
of their characteristic weak interactions between the FEP cation and
OH–. In particular, the AEM with C12FEP showed the
highest ion conductivity of 143.3 ± 27.3 mS cm–1, even with a very low IEC of 0.41 mmol g–1. In
addition to the high level of ion dissociation of FEP, the molecular
assembly of FEP provides ionic conduction paths. This study demonstrates
the importance of high ion dissociation and the formation of a conduction
pathway for AEM with high conductivity
Circular dichroism spectrometry in the ultraviolet wavelength range.
<p>The polypeptide solution of 1mg/mL was preheated for one hour at 80°C.</p
Role of the N‑Terminal Amphiphilic Region of Ovalbumin during Heat-Induced Aggregation and Gelation
Ovalbumin (OVA), a major globular
protein in egg white, forms semiflexible
fibrillar aggregates during heat-induced gelation. The N-terminal
amphiphilic region (pN<sub>1–22</sub>) of OVA is removed after
treatment with pepsin at pH 4 to leave a large OVA fragment (pOVA).
The conformation and thermal stability of pOVA and OVA are similar,
but the rheological strength of the heat-induced gel of pOVA is much
lower compared to that of OVA. The aggregation rate of pOVA, which
forms spherical aggregates, was lower than that of OVA. These results
suggest that the N-terminal amphiphilic region of OVA facilitates
the α-to-β conformational transition, which triggers OVA
fibril formation. Heat treatment of OVA in the presence of pN<sub>1–22</sub> consistently resulted in the formation of straight
fibrils. The strength of OVA and collagen gels was increased when
prepared in the presence of pN<sub>1–22</sub>, suggesting that
pN<sub>1–22</sub> may be used to control the properties of
protein gels
Typical images obtained with the transmission electron microscope.
<p>(a) in the case of the non-preheated solution, ×12,000; (b) in the case of the non-preheated solution, ×40,000; (c) in the case with one-hour preheating at 80°C, ×12,000; and (d) in the case with one-hour preheating at 80°C, ×40,000.</p
Contour maps of brightness for the polypeptide solutions.
<p>(a) non-preheated solution (1mg/mL); (b) preheated solution (1mg/mL) for 1-hour at 80°C. The arrows show the locations of tips of the interface.</p
Typical images with an ice/solution interface captured with a CCD camera.
<p>The black lines on the left-hand side of each image show the element wires of the thermocouple. (a) pure water; (b) HPLC6 solution; (c) polypeptide solution (1mg/mL) at t = t<sub>0</sub> s; (d) polypeptide solution (1mg/mL) at t = t<sub>0</sub>+5 s; (e) polypeptide solution in the case with one-hour preheating at 80°C (1mg/mL) at t = t<sub>0</sub> s; (f) polypeptide solution in the case with one-hour preheating at 80°C (1mg/mL) at t = t<sub>0</sub>+26 s; (g) polypeptide solution in the case with 5-hour preheating at 80°C (1mg/mL); and (h) polypeptide solution in the case with 24-hour preheating at 80°C (1mg/mL).</p
Details of cooling section.
<p>The solutions were stored in a space of 25 mm × 22 mm × 0.02 mm between parallel cover glasses. The gap between the cover glasses was realized by the presence of a screen, printed on the lower side of the upper cover glass. The transparent cover and plastic film were used to reduce the influence of air-conditioning flow on the measurements.</p
Polypeptide and Winter Flounder Antifreeze Protein.
<p>Polypeptide and Winter Flounder Antifreeze Protein.</p