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In this study, we prepared and characterized enzyme (α-chymotrypsin or lactase)-encapsulating core-shell fibermats by electrospinning. The hydrophilic copolymer of acrylamide (AM) and diacetone acrylamide (DAAM), poly(AM/DAAM), was used as the base material to obtain the core unit of nanofibers. During electrospinning, poly(AM/DAAM) was crosslinked with the bifunctional crosslinker adipic acid dihydrazide (ADH) in the presence of enzyme molecules. The cores were wrapped with hydrophobic poly(ε-caprolactone) (PCL) layers as shell unit. Different from the fibermats of only poly(AM/DAAM)/ADH, the core-shell fibermat of poly(AM/DAAM)/ADH and PCL exhibited sufficient mechanical strength and stability of the stacked nanofibrous structure in a neutral-pH buffer. Furthermore, when the PCL-shell thickness was controlled to be less than 150 nm, the encapsulated enzymes exhibited an apparent activity of >70–80% for low-molecular weight substrates in an immersion buffer. These results indicate that the core-shell fibermats of poly(AM/DAAM)/ADH and PCL (or other hydrophobic polymer) could be used as effective enzyme-immobilizing platforms.

The development of additional extraction surfactants for membrane proteins is necessary for membrane protein research, since optimal combinations for the successful extraction of target membrane proteins from biological membranes that minimize protein denaturation are hard to predict. In particular, those that have a unique basal molecular framework are quite attractive and highly desired in this research field. In this study, we successfully constructed a new extraction surfactant for membrane proteins, NPDGCKK, from the peptide-gemini-surfactant (PG-surfactant) molecular framework. The PG-surfactant is a U-shaped lipopeptide scaffold, consisting of a short linker peptide (-X-) between two long alkyl-chain-modified Cys residues and a peripheral peptide (Y-) at the N-terminal side of long alkyl-chain-modified Cys residues. Using photosystem I (PSI) and photosystem II (PSII) derived from Thermosynecoccus vulcanus as representative membrane proteins, we evaluated whether NPDGCKK could solubilize membrane proteins while maintaining structure and functions. Neither the membrane integral domain nor the cytoplasmic domain of PSI and PSII suffered any damage upon the use of NPDGCKK based on detailed photophysical measurements. Using thylakoid membranes of T. vulcanus as a representative biological membrane sample, we performed experiments to extract membrane proteins, such as PSI and PSII. Based on the extraction efficiency and maintenance of protein supramolecular structure established using clear native-PAGE analyses, we proved that NPDGCKK functions as a novel class of peptide-containing extraction surfactants for membrane proteins.

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