Use of Silicone Membrane Permeation to Assess Thermodynamic Activities of Ionic Liquids and Their Component Cation and Anion.

Ionic liquid (IL) was prepared by mixing lidocaine and ibuprofen as a cation and anion, respectively, at various ratios. We determined the permeation of both compounds from the IL through a silicone membrane selected as a model biological membrane, and mathematically analyzed the permeation data from the viewpoint of the thermodynamic activities of lidocaine, ibuprofen, and the IL. As a result, IL and ibuprofen diffusely permeated through the membrane in the case of applying IL preparations with a molar fraction of ibuprofen of 0.5 or higher. The IL was thought to separate into lidocaine and ibuprofen in the receiver. On the other hand, when applying IL preparations with a molar fraction of lidocaine of 0.5 or higher, IL and lidocaine permeated. The permeation rate of IL itself was maximized when the applied IL was prepared using equimolar amounts of lidocaine and ibuprofen, and it decreased when the fraction of lidocaine or ibuprofen increased by more than 0.5. Their membrane permeation rates increased with an increase in their activity, and no more increase was found when the drugs were saturated in the IL. These membrane permeation profiles reflected well the mathematically calculated ones according to the concept of activity.

Effect of reparation of repeat sequences in the human alpha-synuclein on fibrillation ability.

The aggregation and fibrillation of alpha-synuclein has been implicated as a causative factor in the Parkinson's disease. The hexamer motif KTKEGV is found in each of the seven imperfect repeat sequences in the N-terminal half of alpha-synuclein. The motif is not fully conserved in the sixth and seventh repeats. We created mutants in which the motif was repaired to be fully conserved in either (Rep6 and Rep7) or both (Rep67) of these two repeats. The Rep6 and Rep67 mutants showed a greatly reduced propensity to aggregate and fibrillate while all three mutants showed greater resistance to HFIP-induced formation of the alpha-helix intermediate. Resistance to formation in the partially folded intermediate may repress the folding of alpha-synuclein, consequently interfering with the aggregation and fibril formation. These results demonstrated that KTKEGV repeats may have a significant role in keeping native unfolded status of alpha-synuclein.

Engineered alpha-synuclein prevents wild type and familial Parkin variant fibril formation.

Alpha-synuclein is a major component of several pathological lesions diagnostic of specific neurodegenerative disease such as Parkinson's disease. This study focuses on the non-amyloid beta component of Alzheimer's disease amyloid, a key region for the aggregation and fibril formation of alpha-synuclein. Several mutations were introduced in an attempt to repress beta-strand formation and hydrophobic interaction-based aggregation. Although reducing the hydrophobicity drastically decreased fibril formation, the Val70Thr and Val70Pro mutations resulted in an unstable secondary structure thereby increasing non-structural aggregation, instead of fibril formation. Therefore, the stabilization of non-structural natively unfolded status is important to prevent alpha-synuclein fibril formation. Mixing the Val70Thr/Val71Thr double mutant, which has inherently low potential, with the fibril forming alpha-synucleins, WT and Ala53Thr, greatly reduced their fibril formation and aggregation. This double mutant has great potential for further therapeutic approaches.