Copolymers of acrylic acid and styrene with styrene unit contents of 2.7, 5.7, and 9.5% were synthesized by free radical copolymerization. Poly(ethylenimine)s with benzylated unit contents of 2.4, 6.0, 10.6, and 16.7% were obtained by the reaction of poly(ethylenimine) with benzyl bromide. Polyelectrolyte complex capsules consisting of these polymers were prepared. Influence of the hydrophobic units on pH-responsive release property of the capsules was studied using phenylethylene glycol as a permeant. When the copolymer with styrene unit content of 5.7% or the poly(ethylenimine) with the benzylated unit content of 2.4 -10.6% was used as the membrane components, the permeability of the capsule membrane became minimum and was 10 -20 fold lower than that of the poly(acrylic acid)-poly(ethylenimine) complex capsule membrane in the pH region between 3 and 7. In contrast, the hydrophobic units did not lower the permeability of the capsule membranes significantly below pH 3 and above pH 7. Thus, the capsule membranes containing hydrophobic units exhibited remarkable permeability changes in the narrow pH regions of 2-3 and 7-9. Also, the capsule containing the benzylated PEI in the membrane changed the release rate of the contents very quickly, in response to the ambient pH alteration. Therefore, polyelectrolyte complex capsules, which are highly sensitive to pH change, were obtained by using the polyelectrolytes with the hydrophobic units as membrane components.

Dipeptidyl peptidase 4 (DPP-4) inhibitors are used for the treatment of type-2 diabetes mellitus. Various synthetic inhibitors have been developed to date, and plants containing natural DPP-4 inhibitors have also been identified. Here, 13 plant samples were tested for their DPP-4 inhibitory activity. Macrocarpals A–C were isolated from Eucalyptus globulus through activity-guided fractionation and shown to be DPP-4 inhibitors. Of these, macrocarpal C showed the highest inhibitory activity, demonstrating an inhibition curve characterised by a pronounced increase in activity within a narrow concentration range. Evaluation of macrocarpal C solution by turbidity, nuclear magnetic resonance spectroscopy and mass spectrometry indicated its aggregation, which may explain the characteristics of the inhibition curve. These findings will be valuable for further study of potential small molecule DPP-4 inhibitors.

The Pacific oyster, Crassostrea gigas, is a traditional food worldwide. The soft body of the oyster can easily accumulate heavy metals such as cadmium (Cd). To clarify the molecular mechanism of Cd accumulation in the viscera of C. gigas, we identified Cd-binding proteins. 5,10,15,20-Tetraphenyl-21H,23H-porphinetetrasulfonic acid, disulfuric acid, tetrahydrate, and Cd-binding competition experiments using immobilized metal ion affinity chromatography revealed the binding of water-soluble high molecular weight proteins to Cd, including C. gigas protein disulfide isomerase (cgPDI). Liquid chromatography–tandem mass spectrometry (LC–MS/MS) analyses revealed two CGHC motifs in cgPDI. The binding between Cd and rcgPDI was confirmed through a Cd-binding experiment using the TPPS method. Isothermal titration calorimetry (ITC) revealed the binding of two Cd ions to one molecule of rcgPDI. Circular dichroism (CD) spectrum and tryptophan fluorescence analyses demonstrated that the rcgPDI bound to Cd. The binding markedly changed the two-dimensional or three-dimensional structures. The activity of rcgPDI measured by a PDI Activity Assay Kit was more affected by the addition of Cd than by human PDI. Immunological analyses indicated that C. gigas contained cgPDI at a concentration of 1.0 nmol/g (viscera wet weight). The combination of ITC and quantification results revealed that Cd-binding to cgPDI accounted for 20% of the total bound Cd in the visceral mass. The findings provide new insights into the defense mechanisms of invertebrates against Cd.

A new device has been developed for measuring wave pressure at the field level. It is configured with a pressure and 3 directional acceleration sensors as well as a self-recording system with 32 MB memory. It can work for 45 days with a cell battery under 20Hz sampling frequency and costs less than one tenth of the existing cable type pressure measuring systems. Performance of the device has been tested on an upright section of a breakwater on coral reef flat in Okinawa of Japan. Data obtained shows that the new device may treat as reliable. The pressure acting on a breakwater on the reef flat is strongly influenced by the water surface level rise of surf beat waves. Pressure distribution shows that pressure due to a short period wave can be estimated by the partially reflected wave theory, so that the resultant depth of still water level, wave setup and surface level rise due to surf beat wave can be regarded as the design water depth.

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