Kinetics and Control of Self-Assembly of ABH1 Hydrophobin from the Edible White Button Mushroom

Hydrophobins are small fungal proteins that self-assemble at hydrophobic/hydrophilic interfaces to form stable, amyloid membranes that are resistant to denaturation. Their remarkable surface activity has driven intense research for their potential utility in biomedical and cosmetic applications. In this research, the self-assembly characteristics of the Class I hydrophobin ABH1 from Agaricus bisporus, the edible white button mushroom, were evaluated as a function of solution and interface properties, in an attempt to gain greater mechanistic understanding. The kinetics of self-assembly were examined using dynamic quartz crystal microbalance techniques in combination with AFM, ellipsometry, contact angle goniometry, light scattering, and circular dichroism spectroscopy. It was found that the strength of interfacial tension between two phases drives the speed of ABH1 assembly and that the nature and location of the molecular ordering was influenced by temperature. ABH1 demonstrates different characteristics and self-assembly properties than those reported for other Class I hydrophobins, including causing an instantaneous decrease in surface tension in aqueous solution and undergoing a direct transition to β-sheet conformation on self-assembly at elevated temperature

Antimicrobial Peptide Mimicking Primary Amine and Guanidine Containing Methacrylamide Copolymers Prepared by Raft Polymerization

Naturally occurring antimicrobial peptides (AMPs) display the ability to eliminate a wide variety of bacteria, without toxicity to the host eukaryotic cells. Synthetic polymers containing moieties mimicking lysine and arginine components found in AMPs have been reported to show effectiveness against specific bacteria, with the mechanism of activity purported to depend on the nature of the amino acid mimic. In an attempt to incorporate the antimicrobial activity of both amino acids into a single water-soluble copolymer, a series of copolymers containing lysine mimicking aminopropyl methacrylamide (APMA) and arginine mimicking guanadinopropyl methacrylamide (GPMA) were prepared via aqueous RAFT polymerization. Copolymers were prepared with varying ratios of the comonomers, with degree of polymerization of 35–40 and narrow molecular weight distribution to simulate naturally occurring AMPs. Antimicrobial activity was determined against Gram-negative and Gram-positive bacteria under conditions with varying salt concentration. Toxicity to mammalian cells was assessed by hemolysis of red blood cells and MTT assays of MCF-7 cells. Antimicrobial activity was observed for APMA homopolymer and copolymers with low concentrations of GPMA against all bacteria tested, with low toxicity toward mammalian cells