Control of peptide assembly through directional interactions

We demonstrate the self-assembly of tripeptide amphiphiles into spherical hollow capsules from linear nanoribbons via control of the molecular packing. We achieved a transition of arrangement from anisotropic to isotropic by an elaborate design of the molecular architecture.close3

Multivalent Nanofibers of a Controlled Length: Regulation of Bacterial Cell Agglutination

Control of the size and shape of molecular assemblies on the nanometer scale in aqueous solutions is very important for the regulation of biological functions. Among the well-defined supramolecular structures of organic amphiphiles, one-dimensional nanofibers have attracted much attention because of their potential applications in biocompatible materials. Although much progress has been made in the field of self-assembled nanofibers, the ability to control the fiber length remains limited. The approach for control of the fiber length presented herein overcomes this limitation through the coassembly of amphiphilic rod–coil molecules in which the crystallinity of the aromatic segment can be regulated by π–π stacking interactions. The introduction of carbohydrate segments into the fiber exterior endows the nanofibers with the ability to adhere to bacterial cells. Notably, the fiber length systematically regulates the agglutination and proliferation of bacterial cells exposed to these fibers

Glycoconjugate Nanoribbons from Self-Assembly of Carbohydrate-Peptide Block Molecules for Controllable Bacterial Cell Cluster Formation

We demonstrate here the rational design strategy to control the length of 1-dimensional ??-sheet peptide nanoassembly. We synthesized the ??-sheet peptides with attached coils and carbohydrates. We reasoned that the bulkiness of the coils affects the final length of the assembled ??-sheet peptide nanostructures because of the steric crowding effect. The nanostructure from the peptide with a small and linear coil was several micrometers long, whereas the one from the peptide with a high-volume-fraction dendritic coil was only about 150 nm long. For potential biological applications of the peptide nanoassemblies, we investigated the interactions of the carbohydrate-coated nanoassemblies with E. coli cells containing cognate binding proteins. The results showed that both of the nanoassemblies could immobilize and/or aggregate bacterial cells. The degrees of immobilization were similar for both nanoassemblies; however, only the long nanoribbon was shown to induce the formation of bacterial clusters.close0

Observation of an unprecedented body centered cubic micellar mesophase from rod-coil molecules

We have demonstrated that rod-coil molecules based on a tetra-p-phenylene rod and a poly(propylene oxide) coil self-assemble into an unprecedented body centered cubic micellar structure in the melt, through detailed morphological analysis by X-ray scattering and transmission electron microscopy experimentsclose5

Strain versus Tunable Terahertz Nanogap Width: A Simple Formula and a Trench below

A flexible zerogap metallic structure is periodically formed, healing metal cracks on a flexible substrate. Zerogap is continuously tunable from nearly zero to one hundred nanometers by applying compressive strains on the flexible substrate. However, there have been few studies on how the gap width is related to the strain and periodicity, nor the mechanism of tunability itself. Here, based on atomic force microscopy (AFM) measurements, we found that 200 nm-deep nano-trenches are periodically generated on the polymer substrate below the zerogap owing to the strain singularities extant between the first and the second metallic deposition layers. Terahertz and visible transmission properties are consistent with this picture whereby the outer-bending polyethylene terephthalate (PET) substrate controls the gap size linearly with the inverse of the radius of the curvature

Phosphate-Responsive Promoter of a Pichia pastoris Sodium Phosphate Symporter▿ †

To develop a functional phosphate-regulated promoter in Pichia pastoris, a phosphate-responsive gene, PHO89, which encodes a putative sodium (Na+)-coupled phosphate symporter, was isolated. Sequencing analyses revealed a 1,731-bp open reading frame encoding a 576-amino-acid polypeptide with 12 putative transmembrane domains. The properties of the PHO89 promoter (PPHO89) were investigated using a bacterial lipase gene as a reporter in 5-liter jar fermentation experiments. PPHO89 was tightly regulated by phosphate and was highly activated when the cells were grown in a phosphate-limited external environment. Compared to translation elongation factor 1α and the glyceraldehyde-3-phosphate dehydrogenase promoter, PPHO89 exhibited strong transcriptional activity with higher specific productivity (amount of lipase produced/cell/h). Furthermore, a cost-effective and simple PPHO89-based fermentation process was developed for industrial application. These results demonstrate the potential for efficient use of PPHO89 for controlled production of recombinant proteins in P. pastoris

NADPH-dependent pgi-gene knockout Escherichia coli metabolism producing shikimate on different carbon sources

10.1111/j.1574-6968.2011.02378.xFEMS Microbiology Letters324110-16FMLE