RESUMO
Host-guest complexation has been mainly investigated in solution, and it is unclear how guest molecules access the assembled structures of host and dynamics of guest molecules in the crystal state. In this study, we studied the uptake, release, and molecular dynamics of n-hexane vapor in the crystal state of pillar[5]arenes bearing different substituents. Pillar[5]arene bearing 10 ethyl groups yielded a crystal structure of herringbone-type 1:1 complexes with n-hexane, whereas pillar[5]arene with 10 allyl groups formed 1:1 complexes featuring a one-dimensional (1D) channel structure. For pillar[5]arene bearing 10 benzyl groups, one molecule of n-hexane was located in the cavity of pillar[5]arene, and another n-hexane molecule was located outside of the cavity between two pillar[5]arenes. The substituent-dependent differences in molecular arrangement influenced the uptake, release, and molecular dynamics of the n-hexane guest. The substituent effects were not observed in host-guest chemistry in solution, and these features are unique for the crystal state host-guest chemistry of pillar[5]arenes.
RESUMO
Activated crystals of pillar[6]arene produced by removing the solvent upon heating were able to take up branched and cyclic alkane vapors as a consequence of their gate-opening behavior. The uptake of branched and cyclic alkane vapors by the activated crystals of pillar[6]arene induced a crystal transformation to form one-dimensional channel structures. However, the activated crystals of pillar[6]arene hardly took up linear alkane vapors because the cavity size of pillar[6]arene is too large to form stable complexes with linear alkanes. This shape-selective uptake behavior of pillar[6]arene was further utilized for improving the research octane number of an alkane mixture of isooctane and n-heptane: interestingly, the research octane number was dramatically improved from a low research octane number (17 %) to a high research octane number (>99 %) using the activated crystals of pillar[6]arene.
RESUMO
We report a simple and easy-to-operate method for separating n-alkanes: when we immersed activated pillar[5]arene crystals into a mixture of n-alkanes with various chain lengths, the crystals preferentially took up n-alkanes with longer chain lengths.
RESUMO
OBJECTIVE: The objective of the present study was to examine the utility of QuantiFERON TB-2G (QFT) in tuberculosis contact investigations performed by a public health center. METHODS: Adachi City Public Health Center, Tokyo, started using QFT in its laboratory service in June, 2005. The results of QFT, as well as tuberculin skin tests (TSTs) performed in tuberculosis contact investigations in the 10 month period since then were here analyzed. QFT was carried out for 67 contacts two months after their last contact with the index case. TST was given simultaneously. RESULTS: Of the total of 67 contacts investigated during the period, 9 were positive for QFT, 5 were doubtful positive, and the remaining 53 were negative. Among 48 subjects tested with TST, 22 had strong reactions with erythema > or = 30 mm, out of which 4 were positive for QFT. In addition, there were 5 QFT-positives among the remaining 26 with weak tuberculin reactions. These 9 subjects with positive QFT were indicated for chemoprophylaxis. CONCLUSIONS: Adachi City Public Health Center is pioneering the application of new technology for detection of latent tuberculosis infection in contact investigations of the inhabitants. As expected from trial findings, QFT was shown to be a useful tool in a practical setting for the purpose of detecting TB infection, with greater accuracy than with TST, independent of the history of BCG vaccination. This approach can help avoid both over-diagnosis and under-diagnosis.
