“On-Off” Switching of Functional Guest Molecules via Exchange of Natural Product Solubilizing Agents

For the development of delivery systems, the solubilization of hydrophobic guest molecules in water is an important yet challenging task. This can be achieved by preparing stable aqueous solutions with a high concentration of guest molecules using a natural product as a solubilizing agent and a mechanochemical high-speed vibration milling apparatus as a solubilizing method. Various solubilizing agent-guest molecule complexes can be obtained via the exchange between solubilizing agents, which enables the “on-off” switching of the properties of functional guest molecules, such as fluorescence intensity, and photodynamic activity. In the exchange method, guest molecules can transfer into cell membranes such as lysosomes and exosomes. Therefore, the exchange method of the solubilizing agents not only creates novel solubilizing agent-guest molecule complexes but also is applied to drug delivery systems.     

Definition of an Index Parameter To Screen Highly Functional Enzymes Derived from a Biochemical and Thermodynamic Analysis of Ancestral meso-Diaminopimelate Dehydrogenases

Sequence-based protein design approaches are being adopted to generate highly functional enzymes; however, screening the enzymes remains a time-consuming task. In this study, by analyzing the enzymatic properties of four ancestral meso-2,6-diaminopimelate dehydrogenases (AncDAPDHs), AncDAPDH-N1, -N2, -N3, and -N4, we attempted to define a new index parameter that is helpful for efficiently screening the enzymes. Biochemical and thermodynamic analyses indicated that only AncDAPDH-N4 exhibited greater thermal stability than and activity similar to those of native DAPDHs. Structural and sequence comparisons between DAPDH from Corynebacterium glutamicum (CgDAPDH) and the AncDAPDHs suggested that “quality of mutations” is a potential index parameter. In fact, the mutations introduced from CgDAPDH to AncDAPDH-N4 correlated highly with the mutations accumulated during the evolution process from mesophiles to thermophiles. These results suggest that, although there are several exceptions, the correlation coefficient can be used as an index parameter for screening high-functioning enzymes from sequence data.     

A Cationic Copolymer Enhances Responsiveness and Robustness of DNA Circuits

Toehold-mediated DNA circuits are extensively employed to construct diverse DNA nanodevices and signal amplifiers. However, operations of these circuits are slow and highly susceptive to molecular noise such as the interference from bystander DNA strands. Herein, this work investigates the effects of a series of cationic copolymers on DNA catalytic hairpin assembly, a representative toehold-mediated DNA circuit. One copolymer, poly(_L-lysine)-graft-dextran, significantly enhances the reaction rate by 30-fold due to its electrostatic interaction with DNA. Moreover, the copolymer considerably alleviates the circuit's dependency on the length and GC content of toehold, thereby enhancing the robustness of circuit operation against molecular noise. The general effectiveness of poly(_L-lysine)-graft-dextran is demonstrated through kinetic characterization of a DNA AND logic circuit. Therefore, use of a cationic copolymer is a versatile and efficient approach to enhance the operation rate and robustness of toehold-mediated DNA circuits, paving the way for more flexible design and broader application.     

Fine dispersion of carbon black in fluorene‐based resin

The dispersion ability of fluorene‐based epoxy resin (FBE), bisphenol A based epoxy resin (PBE), fluorene‐based polyester (FBP), and polycarbonate (PC) in carbon black (CB) was evaluated. CB/FBE composite had a lower L value (reflectance, blackness) than that of CB/PBE composite, for the same CB content. Aggregations of CB in CB/FBE composites were much smaller than those in CB/PBE composites. The strong interaction between fluorene with cardo structure and CB resulted in a fine dispersion of CB in FBE. FBP had much higher dispersion ability of CB than PC. CB (50 wt%) was dispersed into FBP compared with the 10 wt% of CB dispersed in PC by melt blending. The effect of CB on the mechanical properties of FBP was much higher than that on PC due to fine dispersion of CB in FBP. The effect of CB addition on the T_g of FBP was also higher than that of CB on the T_g of PC. Computational simulation indicates that most stable energy between fluorene with a cardo structure and graphite structure was smaller than the energy between bisphenol A and graphite. It was also shown that the minimum energy appeared when the fluorene structure was almost parallel to the graphite plane. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

BAMO/NMMO Copolymer with Polyester Initiation

In order to improve of mechanical properties at low temperature region, 3,3-bis(azidomethyl)oxetan (BAMO), 3-nitratomethyl-3-methyloxetane (NMMO) and polyester (PE) copolymer were synthesized by using polyester initiator with boron trifluoride etherate. The molar ratio of each units in the BAMO/NMMO/PE copolymer was 7.4/2.6/0.39 according to the ¹H-NMR spectrum analysis and was almost exactly the same composition as the monomer fed (7/3/0.33). The relative composition of triad microstructures was same as theoretical value and they were randomly arranged. The PE, which was a replacement of 1,4-butanediol, acted as an excellent soft segment in the copolymer, and the glass transition point of the elastomer was 4.8 degrees lowered by the replacement. This effect was also verified in the mechanical properties of the composite propellant and the tensile elongation was increased from 15% to 40%percnt; at −40 °C.     

2D–3D-Convertible,pH-Responsive Lipid Nanosheets

2D nanosheets self-assembled with amphiphilic molecules are promising tools for biomedical applications; yet, there are challenges to form and stabilize these nanosheets under complex physiological conditions. Here, the development of lipid nanosheets with high structural stability that can be reversibly converted to cell-sized vesicles by changes in pH within the physiological range robustly, are described. The system is controlled by the membrane disruptive peptide E5 and a cationic copolymer anchored on lipid membranes. It is envisioned that nanosheets formed using the dual anchoring peptide/cationic copolymer system can be employed in dynamic lipidic nanodevices, such as the vesosomes described here, drug delivery systems, and artificial cells.