pH responsiveness of fibrous assemblies of repeat-sequence amphipathic α-helix polypeptides.

We reported previously that our designed polypeptide α3 (21 residues), which has three repeats of a seven-amino-acid sequence (LETLAKA)3, forms not only an amphipathic α-helix structure but also long fibrous assemblies in aqueous solution. To address the relationship between the electrical states of the polypeptide and its α-helix and fibrous assembly formation, we characterized mutated polypeptides in which charged amino acid residues of α3 were replaced with Ser. We prepared the following polypeptides: 2Sα3 (LSTLAKA)3, in which all Glu residues were replaced with Ser residues; 6Sα3 (LETLASA)3, in which all Lys residues were replaced with Ser; and 2S6Sα3 (LSTLASA)3; in which all Glu and Lys residues were replaced with Ser.

Single-cell cloning and expansion of human induced pluripotent stem cells by a microfluidic culture device.

The microenvironment of cells, which includes basement proteins, shear stress, and extracellular stimuli, should be taken into consideration when examining physiological cell behavior. Although microfluidic devices allow cellular responses to be analyzed with ease at the single-cell level, few have been designed to recover cells. We herein demonstrated that a newly developed microfluidic device helped to improve culture conditions and establish a clonality-validated human pluripotent stem cell line after tracing its growth at the single-cell level.

Subcellular glucose exposure biases the spatial distribution of insulin granules in single pancreatic beta cells.

In living tissues, a cell is exposed to chemical substances delivered partially to its surface. Such a heterogeneous chemical environment potentially induces cell polarity. To evaluate this effect, we developed a microfluidic device that realizes spatially confined delivery of chemical substances at subcellular resolution.

Improved hypothermic short-term storage of isolated mouse islets by adding serum to preservation solutions.

Preserving isolated islets at low temperature appears attractive because it can keep islet quantity comparable to freshly isolated islets. In this study, we evaluated the effect of serum as an additive to preservation solutions on islet quality after short-term hypothermic storage. Isolated mouse islets were preserved at 4°C in University of Wisconsin solution (UW) alone, UW with serum, M-Kyoto solution (MK) alone or MK with serum.

A perfusable microfluidic device with on-chip total internal reflection fluorescence microscopy (TIRFM) for in situ and real-time monitoring of live cells.

A microfluidic device integrated with a Total Internal Reflection (TIR)-based chip for cell observation and analysis was developed. This integrated device enables in situ Total Internal Reflection Fluorescence Microscopy (TIRFM) on adherent cells cultured under continuous medium perfusion. This TIR-based chip, allows TIRFM to be easily performed on cells without the assembly of complicated optical components and cell culture chambers.

Open-access and multi-directional electroosmotic flow chip for positioning heterotypic cells.

We propose a novel method of cell positioning using electroosmotic flow (EOF) to analyze cell-cell interactions. The EOF chip has an open-to-air configuration, is equipped with four electrodes to induce multi-directional EOF, and allows access of tools for liquid handling and of physical probes for cell measurements. Evaluation of the flow within this chip indicated that it controlled hydrodynamic transport of cells, in terms of both speed and direction.

The effects of the side chains of hydrophobic aliphatic amino acid residues in an amphipathic polypeptide on the formation of alpha helix and its association.

The polypeptide alpha3, which was synthesized by us to produce an amphipathic helix structure, contains the regular three times repeated sequence (LETLAKA)(3), and alpha3 forms a fibrous assembly. To clarify how the side chains of amino acid residues affect the formation of alpha helix, Leu residues, which are located in the hydrophobic surface of an amphipathic helix, were replaced by other hydrophobic aliphatic amino acid residues systematically, and the characters of the resulting polypeptides were studied. According to the circular dichroism (CD) spectra, the Ile-substituted polypeptides formed alpha helix like alpha3.