The alkyl linkers in tandem-homodimers of a ß-sheet-forming nonapeptide affect the self-assembled nanostructures.

There is increasing interest in designing smart biomaterials by employing the self-assembly characteristics of synthetic peptides. The use of amyloid-like fibrils is one approach to nanometer- and micrometer-sized supramolecular structures. However, it is generally difficult to predict and/or analyze peptide conformations in nanostructures generated by the self-assembly of ß-sheet-forming peptides such as amyloid-ß peptide because each peptide experiences a slightly different environment. Therefore, a methodology for rationally designing peptide-based smart materials is required. In this study, we demonstrate the design and synthesis of tandem-homodimers of a ß-sheet-forming peptide where the amino acid sequence is duplicated in series and joined via alkyl linkers of different chain length. The conformations of these tandem-homodimers within the self-assembled nanoarchitectures in aqueous solution were characterized. Our findings demonstrate that the hydrophobicity and/or flexibility of the alkyl linkers significantly affect the peptide conformation (extended or bent) of the self-assembled peptide nanostructures. We believe that the present tandem-homodimerization method represents a new direction for the rational design of peptide-based smart biomaterials.

Degradation of methyl orange using short-wavelength UV irradiation with oxygen microbubbles.

A novel wastewater treatment technique using 8 W low-pressure mercury lamps in the presence of uniform-sized microbubbles (diameter = 5.79 microm) was investigated for the decomposition of methyl orange as a model compound in aqueous solution. Photodegradation experiments were conducted with a BLB black light blue lamp (365 nm), a UV-C germicidal lamp (254 nm) and an ozone lamp (185 nm+254 nm) both with and without oxygen microbubbles. The results show that the oxygen microbubbles accelerated the decolorization rate of methyl orange under 185+254 nm irradiation. In contrast, the microbubbles under 365 and 254 nm irradiation were unaffected on the decolorization of methyl orange. It was found that the pseudo-zero order decolorization reaction constant in microbubble system is 2.1 times higher than that in conventional large bubble system. Total organic carbon (TOC) reduction rate of methyl orange was greatly enhanced by oxygen microbubble under 185+254 nm irradiation, however, TOC reduction rate by nitrogen microbubble was much slower than that with 185+254 nm irradiation only. Possible reaction mechanisms for the decolorization and mineralization of methyl orange both with oxygen and nitrogen mirobubbles were proposed in this study.