Synthesis and characterization of a fatty acid self-assembled monolayer on CeO2 nanoparticles: to explore solution-state property of a SAM

Decanoic acid self-assembled monolayer (SAM) in the quasi-crystalline state was prepared on the surface of the cubic CeO₂ nanoparticles (6.5 ± 1.1 nm) by hydrothermal synthesis. The purification method to obtain quasi-crystalline SAM without residual (free) decanoic acid was developed. The SAM was carefully washed (purified) and characterized carefully by FT-IR, TG, DSC, and NMR. The obtained results showed that good agreement with the property of the dry state SAM. The solution state properties of the SAM were also examined by the CeO₂ nanoparticles. It turned out that the quasi-crystalline SAM could be swollen by its good solvents, cyclohexane, and chloroform; however, the quasi-crystalline SAM showed that a size exclusion effect to the solvent, trans-decalin. In addition, it turned out that the molecular motion of the decanoic acids in the SAM was highly restricted even in the swollen state depending on the distance from the grafting point to the CeO₂ surface. The strong osmosis was also observed. The solvent molecules were not easily released from the SAM even after the solvent molecules outside of the SAM were frozen.     

Design variable tolerance effects on the natural frequency variance of constrained multi-body systems in dynamic equilibrium

The design variable tolerance effects on the natural frequency variance of constrained multi-body systems in dynamic equilibrium are investigated in this study. Monte-Carlo simulation is often employed for such investigations, but it is known to have serious drawbacks. Excessive amount of computation time needs to be consumed since a large number of evaluations are usually required for the method. Furthermore, the solution accuracy cannot be always guaranteed in spite of the excessive amount of computation time. In order to overcome such drawbacks, a method employing eigenvalue sensitivity information is proposed to obtain the variance of natural frequency in this study. In order to verify the accuracy and the efficiency of the method, some numerical examples of multi-body systems in dynamic equilibrium are solved and the results are compared to those obtained by an analytical method and Monte-Carlo simulation.     

Prediction of the global energy minimum conformation of polypeptides by the High Directional Monte Carlo procedure

Abstract

A new Monte Carlo sampling scheme, namely High Directional Monte Carlo procedure, is used to obtain the global energy minimum conformations of polypeptides such as enkephalin and melittin. The resultant structures of enkephalin and melittin agree well with previous results of theoretical and experimental studies. Particularly, it is shown that some important parts in the conformation, such as the hinge region that principally determines the tertiary structure of proteins, are correctly described by the new method. The resultant structures are compared with those of other works and their stereoscopic views are shown.     

Fast parallel detection of feline panleukopenia virus DNA by multi‐channel microchip electrophoresis with programmed step electric field strength

A multi‐channel microchip electrophoresis using a programmed step electric field strength (PSEFS) method was investigated for fast parallel detection of feline panleukopenia virus (FPV) DNA. An expanded laser beam, a 10× objective lens, and a charge‐coupled device camera were used to simultaneously detect the separations in three parallel channels using laser‐induced fluorescence detection. The parallel separations of a 100‐bp DNA ladder were demonstrated on the system using a sieving gel matrix of 0.5% poly(ethylene oxide) (M_r = 8 000 000) in the individual channels. In addition, the PSEFS method was also applied for faster DNA separation without loss of resolving power. A DNA size marker, FPV DNA sample, and a negative control were simultaneously analyzed with single‐run and one‐step detection. The FPV DNA was clearly distinguished within 30 s, which was more than 100 times faster than with conventional slab gel electrophoresis. The proposed multi‐channel microchip electrophoresis with PSEFS was demonstrated to be a simple and powerful diagnostic method to analyze multiple disease‐related DNA fragments in parallel with high speed, throughput, and accuracy.     

Facile Fabrication of Multi‐targeted and Stable Biochemical SERS Sensors

The direct transfer of single‐crystalline Au nanowires (NWs) onto Au substrates was achieved by a simple attachment and detachment process. In the presence of a lubricant, Au NWs grown vertically on a sapphire substrate were efficiently moved to an Au substrate through van der Waals interactions. We demonstrate that the transferred Au NWs on the Au substrate can act as sensitive, reproducible, and long‐term‐stable surface‐enhanced Raman scattering (SERS) sensors by detecting human α‐thrombin as well as Pb²⁺ and Hg²⁺ ions. These three biochemically and/or environmentally important analytes were successfully detected with high sensitivity and selectivity by Au NW‐SERS sensors bound by a thrombin‐binding aptamer. Furthermore, the as‐prepared sensors remained in working order after being stored under ambient conditions at room temperature for 80 days. Because Au NWs can be routinely transferred onto Au substrates and because the resultant Au NW‐SERS sensors are highly stable and provide with high sensitivity and reproducibility of detection, these sensors hold potential for practical use in biochemical sensing.