Tatsuya Oshima

Amyloid protein aggregates pose a significant challenge due to their extreme insolubility and association with neurodegenerative diseases. To identify effective solvents for dissolving amyloid-forming proteins, a screening of deep eutectic solvents (DESs), including natural DESs (NADES), and related solvents was conducted. Aggregated lysozyme (LA) was reproducibly prepared under acidic and thermal conditions as a model of poorly soluble protein aggregates. Spectroscopic analyses using Thioflavin T fluorescence and circular dichroism (CD), along with morphological observations under polarized light and SEM, confirmed the formation of β-sheet-rich amyloid-like structures. The citric acid−glycerol DES showed the highest solubility for LA, outperforming other DESs and DMSO. Its performance was further enhanced by the addition of ∼5% water. This result also suggests a strong contribution of multivalent organic acids, such as citric and malic acid, to protein solubilization. CD analysis indicated that lysozyme recovered a native-like secondary structure, suggesting partial structural recovery after dissolution in this DES. These findings highlight the potential of DESs as effective media for dissolving protein aggregates and suggest their possible utility in protein refolding and related biotechnological applications, including potential future biomedical applications.

Dibutyl carbitol (DBC) has been conventionally used for solvent extraction of Au­(III), which exists as tetrachloroauric acid (HAuCl₄), leached by chlorination. However, the water solubility of DBC (3 g/dm³) leads to organic contamination of the aqueous phase. To identify solvents with both high gold extractability and low water solubility, a model Y = f(X) was constructed to predict extractability and water solubility Y from molecular descriptors X of chemical structures using experimental data for various compounds. The charge density profile calculated with COSMO-RS was used as X in the extractability prediction model and genetic algorithm-based wavelength selection, which allows variable selection in regions, was applied. The constructed models showed high prediction accuracy, with correlation coefficients exceeding 0.9 for both extractability and water solubility. The inverse analysis of these models was used to search for solvents with both high extractability and low water solubility. Solvents including (−)-fenchone and 4-phenyl-2-butanone were identified as promising solvents exhibiting comparable extractability to DBC but lower water solubility.

Pillararenes are macrocyclic compounds that can have multiple functional groups and can provide a platform to develop multivalent ligands. Herein, a pillar[6]arene carboxylic acid derivative (OctP[6]CH₂COOH) was prepared to extract the cationic protein cytochrome c (Cyt-c) into organic solvents. OctP[6]CH₂COOH was synthesized by the condensation of ethyl 2-(4-octoxyphenoxy) acetate to obtain the pillar[6]arene derivative, followed by alkali hydrolysis. OctP[6]CH₂COOH showed high extractability for Cyt-c, while a monomer analog and a neutral pillar[6]arene ester derivative did not. The lysine-rich protein Cyt-c was selectively extracted using OctP[6]CH₂COOH over other cationic proteins because the complexation was a result of the inclusion of the NH₃⁺ groups of the lysine residues by the macrocyclic molecule. Cyt-c complexed with OctP[6]CH₂COOH partially underwent a structural change and exhibited peroxidase activity in organic solvents. This is the first report of protein extraction using pillararene derivatives that can be applied for the separation and modification of proteins.

柑橘類に多く含まれるβ-クリプトキサンチン（BCX）について，各種の健康機能性が報告されている．難溶性かつ化学的に不安定なカロテン類であるBCXは製剤によって安定性ならびに消化液への分散性を高め，経口吸収性を改善することが望まれる．本研究では，ミカン搾汁残渣から抽出したBCXを含む油相と，カゼインナトリウム（CasNa）およびショ糖脂肪酸エステル（L-1695）を含む水相とを用いてO/Wエマルションを調製し，さらに均一な細孔径を有するシラス多孔質ガラス（SPG）膜を透過させてSPG膜乳化を行った．粒子径測定により単分散粒子径のエマルションが得られたことを確認し，これを凍結乾燥して固体分散体を得た．得られた固体分散体においてBCXの水分散性ならびに熱安定性は大幅に改善され，その粒子径も単分散であった．調製された固体分散体に含まれるBCXの経口吸収性を評価するため，擬似消化処理を施した固体分散体のCaco-2細胞単層膜を用いた細胞膜透過および蓄積試験を行った．BCXの細胞膜透過は確認されなかったが，複合化によりCaco-2細胞への蓄積量の増加が確認された．