Transformation of peptide nanotubes into a vesicle via fusion driven by stereo-complex formation.

Two types of peptide nanotubes, one is prepared from an amphiphilic peptide having a right-handed helix segment and the other from that having a left-handed helix segment, are shown to transform the morphology into a vesicle by membrane fusion due to stereo-complex formation between these helical segments

Solid Phase Biosensors for Arsenic or Cadmium Composed of A trans Factor and cis Element Complex

The presence of toxic metals in drinking water has hazardous effects on human health. This study was conducted to develop GFP-based-metal-binding biosensors for on-site assay of toxic metal ions. GFP-tagged ArsR and CadC proteins bound to a cis element, and lost the capability of binding to it in their As- and Cd-binding conformational states, respectively. Water samples containing toxic metals were incubated on a complex of GFP-tagged ArsR or CadC and cis element which was immobilized on a solid surface. Metal concentrations were quantified with fluorescence intensity of the metal-binding states released from the cis element. Fluorescence intensity obtained with the assay significantly increased with increasing concentrations of toxic metals. Detection limits of 1 μg/L for Cd(II) and 5 μg/L for As(III) in purified water and 10 µg/L for Cd(II) and As(III) in tap water and bottled mineral water were achieved by measurement with a battery-powered portable fluorometer after 15-min and 30-min incubation, respectively. A complex of freeze dried GFP-tagged ArsR or CadC binding to cis element was stable at 4 °C and responded to 5 μg/L As(III) or Cd(II). The solid phase biosensors are sensitive, less time-consuming, portable, and could offer a protocol for on-site evaluation of the toxic metals in drinking water

Polymeric micelle of a3 b-type lactosome as a vehicle for targeting meningeal dissemination

Polymeric micelle of the A₃B-type lactosome comprising (poly(sarcosine))₃-b-poly(l-lactic acid) was labeled with ¹¹¹In. The ¹¹¹In-labeled A₃B-type lactosome was administered to the model mice bearing meningeal dissemination and bone metastasis at mandible. With single-photon emission computed tomography (SPECT) imaging, the meningeal dissemination was identified successfully by ¹¹¹In-labeled A₃B-type lactosome, which was superior to ²⁰¹TlCl in regard of the imaging contrast. The ¹¹¹In-labeled A₃B-type lactosome was also potential in imaging selectively of bone metastasis at mandible, whilst a nonspecific imaging of the whole bone was obtained by the SPECT imaging using ⁹⁹mTc-HMDP. The polymeric micelle of the A₃B-type lactosome was therefore found to be effective as a vehicle of ¹¹¹In to be targeted to meningeal dissemination and bone metastasis

Fluorescent bioassays for toxic metals in milk and yoghurt

<p>Abstract</p> <p>Background</p> <p>From a human health viewpoint, contaminated milk and its products could be a source of long-term exposure to toxic metals. Simple, inexpensive, and on-site assays would enable constant monitoring of their contents. Bioassays that can measure toxic metals in milk or yoghurt might reduce the risk. For this purpose, the green fluorescent protein (GFP)-tagged <it>trans</it> factors, ArsR-GFP and CadC-GFP, together with their <it>cis</it> elements were used to develop such bioassays.</p> <p>Results</p> <p>ArsR-GFP or CadC-GFP, which binds either toxic metal or DNA fragment including <it>cis</it> element, was directly mixed with cow’s milk or yoghurt within a neutral pH range. The fluorescence of GFP, which is reflected by the association/dissociation ratio between <it>cis</it> element and <it>trans</it> factor, significantly changed with increasing externally added As (III) or Cd (II) whereas smaller responses to externally added Pb (II) and Zn (II) were found. Preparation and dilution of whey fraction at low pH were essential to intrinsic zinc quantification using CadC-GFP. Using the extraction procedure and bioassay, intrinsic Zn (II) concentrations ranging from 1.4 to 4.8 mg/l for milk brands and from 1.2 to 2.9 mg/kg for yoghurt brands were determined, which correlated to those determined using inductively coupled plasma atomic emission spectroscopy.</p> <p>Conclusions</p> <p>GFP-tagged bacterial <it>trans</it> factors and <it>cis</it> elements can work in the neutralized whole composition and diluted whey fraction of milk and yoghurt. The feature of regulatory elements is advantageous for establishment of simple and rapid assays of toxic metals in dairy products.</p

Joining Nanotubes Comprising Nucleobase-carrying Amphiphilic Polypeptides

Three kinds of amphiphilic polypeptides, X-poly(sarcosine)-b-(L-Leu-Aib)6 (X = adenine, thymine, glycolic acid), were synthesized and self-assembled in a tris buffer to take on nanotube morphology. The nanotubes were joined together to extend the nanotube length with the addition of trifluoroethanol and heat treatment at 50 °C for 24 h. The length extension rate decreased in the order of adenine > glycolic acid > thymine depending on the N-terminal chromophores. Adenine–adenine interactions between the nanotubes were found to be more prevalent upon joining the nanotubes than adenine–thymine interactions. Further, adenines on the nanotube surface could chelate with Cu(ii) to thermodynamically stabilize the nanotube membrane. AFM imaging in liquid environment revealed that the membrane elasticity of the adenine nanotube was as high as ca. 1 MPa, which is considered to be strengthened as a result of the adenine–adenine interactions