The pathological process of Alzheimer's disease is closely related to amyloid fibril formation by the causative protein, amyloid (A). The growth behavior of A fibrils is predominated by the seeds-monomeric A interaction. In this study, the local hydrophobicity of seeds of A fibrils was investigated by the aqueous two-phase partitioning method to evaluate the hydrophobic interaction between the seed-monomeric A. The seeds showed a high local hydrophobicity relative to the monomer and fibrils. From the fibril growth experiment and the additive effect of Triton X-100, we could demonstrate the contribution of the hydrophobic seeds-monomer interaction to fibril formation.
The measurements of enthalpies of combustion by use of precision oxygen-bomb combustion calorimeter together with the measurement of carbon dioxide recovery were made for double- and triple-layered [2.2]paracyclophanes. The enthalpies of sublimation were also determined by the measurement of temperature dependence of the vapor pressures for the two compounds. The following values are reported for the standard enthalpy of combustion ΔHco(298.15 K)/kJ mol−1 and standard enthalpy of sublimation ΔHso(298.15 K)/kJ mol−1, respectively: double-layered [2.2]paracyclophane, 8729.48±1.80, 99.6±1.8; triple-layered [2.2]paracyclophane, 14230.87±3.59, 125.9±2.5. From analyses of the derived standard enthalpy of formation in gaseous state the following two values for total strain energy Us⁄kJ mol−1 of a molecule of triple-layered [2.2]paracyclophane were obtained: 251.9±5.6 with group method and 245.6±9.8 with chemical similarity method, respectively. These values are approximately twice the magnitudes of the corresponding quantities for double-layered [2.2]paracyclophane. From the analysis of the total strain energy by use of the result of Boyd’s molecular mechanical calculation, the contribution from the twisting of the inner benzene ring to the total strain energy of triple-layered [2.2]paracyclophane was estimated to be almost twice that from one outer bent benzene ring.
Standard energies of combustion at 298.15 K have been determined for crystalline acetanilide and nicotinic acid by static oxygen bomb calorimetry. Derived standard enthalpies of combustion and of formation are −(4224.8±1.0) and −(209.5±1.5) kJ mol−1 for acetanilide, and −(2730.83±0.48) and −(344.81±0.92) kJ mol−1 for nicotinic acid, respectively. Nicotinic acid pellets of 1.2 g in mass showed remarkable tendency to spatter when partially burnt. Factors governing the completeness of combustion of the material have been explored through 28 test combustion experiments.
Precision oxygen bomb combustion calorimetry was carried out for the title compounds in the crystalline states. Standard enthalpies of formation at 298.15 K for the crystalline and gaseous states were derived.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.