Ultramicrodetermination of nitrogen in organic compounds: 8. Weighing of hygroscopic and volatile samples for the sealed-tube method

A new method for handling hygroscopic and volatile samples for decimilligram determination of organic nitrogen by the sealed-tube method was described. It involves the use of a copper-foil capsule in which hygroscopic and volatile samples can be dried to constant weight and weighed. Satisfactory results were obtained with this method.     

Ultramicrodetermination of nitrogen in organic compounds: IX. A new method for handling volatile liquids in the sealed-tube method

A new method for handling volatile liquids in the ultramicrodetermination of nitrogen by the sealed-tube method, using a weighing tube of thin-walled capillary containing a capillary of sample, is described. Before sealing the weighing tube, the air present can be replaced with a gas mixture of CO₂ and CH₄ having approximately the density of air. The weighing tube is broken by tapping prior to combustion, and analysis is not affected by volatilization.     

Freezing phenomena of lennard-jones fluid confined in jungle-gym nanospace: a monte carlo study

We performed grand canonical Monte Carlo simulations for a Lennard-Jones fluid confined in a jungle-gym (JG) nanospace of cubic structure modeled on a specific type of metal organic frameworks (MOFs) to investigate freezing phenomena. Our simulations clarified that the JG nanospace with the pore sizes from 5sigma to 11sigma strongly depresses freezing due to a geometrical hindrance effect, resulting in far lower freezing temperature than the bulk freezing point. The fluid-rod interaction is found to give little effect on the freezing temperature in the larger pore sizes. For smaller pores from 2sigma to 3sigma, on the other hand, a dominant factor is a template effect to enhance the localization of molecules into a specific configuration that matches the locations of potential minima, leading to a variety of molecular configurations. In this range of smaller pore sizes, the solidification temperatures are higher than those of the larger pores mainly due to strong influence of the fluid-rod interaction but are still lower than the bulk freezing temperature. In addition, a unique solid-to-solid transition is observed in a specific size of pore of 2.73sigma, which is caused by structural correlation between adjacent cells. On the basis of these results, a phase diagram in the JG nanospace is drawn.     

Unusual condensation of 3-Thia[5](1,1')ferrocenophane-1,5-dione with glyoxal. Formation of [1.1](2,3)thiopheno(1,1')ferrocenophane-1,7-dione

When 3-thia [5](1,1')ferrocenophane-1,5-dione 2 was condensed with glyoxal in the presence of sodium ethoxide, a thiophene-2,3-diyl derivative 3 was obtained as a sole product, instead of the expected 2,5-substituted compound 1.     

Stable immobilization of an oligonucleotide probe on a gold substrate using tripodal thiol derivatives

We proposed an interface molecule for immobilization of DNA probes on solid substrates of DNA chips. We have designed and synthesized tripodal thiol derivatives for stable immobilization of oligonucleotide probes on a gold surface. On the basis of the tetrahedral structure of tripod, the tripodal thiol derivatives were bonded upright to the gold substrate, which would control the orientation of oligonucleotide probes. When the gold substrate with oligonucleotide probes tethered using the thiol derivatives was exposed to deionized water at higher temperatures, the tripodal interface molecules were attached to the gold surface more stably than the single contact molecules. The DNA chip platform combined with the functional interface molecule is suitable for a reproducible, inexpensive, and high-throughput detection system for genetic analyses in clinical diagnostics.     

Size-tuneable and micro-patterned iron nanoparticles derived from biomolecules via microcontact printing SAM-modified substrates and controlled-potential electrolyses

Site-selected and size-controlled iron nanoparticles were prepared on coplanar surfaces via microcontact printing of SAM-modified Au/mica electrodes and controlled-potential electrolytic reactions using ferritin biomolecules. Ferritin molecules packed like a full monolayer on 6-amino-1-hexanethiol (AHT)- and 11-amino-1-undecanethiol (AUT)-modified Au/mica surface via electrostatic interactions, which did not depend on the chain length of the amino terminal alkane thiols. After heat-treatment at 400 degrees C for 60 min, iron oxide nanoparticles (ca. 5 nm in diameter) derived from ferritin cores were observed at the Au/mica surface by atomic force microscopy (AFM). On the study on the electrochemistry of ferritin immobilized onto AHT- and AUT-modified Au/mica electrodes, the redox response of the ferritin immobilized AHT-modified electrode was clearly observed. On the other hand, no redox peak for ferritin was obtained at the AUT-modified electrode. The electron transfer between ferritin and the electrode through the AUT membrane could not take place. The difference in the electrochemical response of ferritin immobilized onto AHT- and AUT-modified Au/mica was caused by the chain length of the amino terminal alkane thiols. Uniform patterns of AHT and AUT on the Au/mica electrode surface were performed by use of a poly(dimethylsiloxane) (PDMS) stamp. After the immobilization of ferritin onto both AHT- and AUT-modified electrode surfaces, the modified electrode was applied to a -0.5 V potential for 30 min in a phosphate buffer solution. After this procedure, the PDMS stamp patterning image appeared by scanning electron microscopy (SEM) image. The SEM results induced by the size change of the ferritin core consisting of iron(III) by electrolysis.