Nanobiotechnology and its role in the development of new analytical devices

Physical methods of molecule observation and manipulation will prove useful, not only as research tools for investigating biomolecular structure and behavior, but also for the creation of nanostructures. Supramolecular and self-assembling structures are able to generate nanostructures, with many such systems being of biological origin. They form the interface between nanotechnology and biotechnology. Whereas biotechnological processes usually involve populations of cells or molecules, nanotechnological methods operate at the level of individual molecule manipulation. This article considers what advances have been made through cross-fertilisation between nanotechnology and biotechnology to develop for the next millennium new analytical tools at the microscale, using nanostructures as the sensitive part and with the ability to detect individual molecules.     

Zu Struktur,Bindung und Ligandenaustauschverhalten von Nitrosyltechnetium(II)-Verbindungen Eine. EPR-Untersuchung

Structure, Bonding, and Ligand Exchange Behaviour of Nitrosyl-Technetium (II) Compounds. An EPR Study EPR investigations on the nitrosyltechnetium(II) compounds (Bu₄N)₂[Tc(NO)Cl₅], (Bu₄N)[Tc(NO)Br₄], (Bu₄N)[Tc(NO)I₄], and (Ph₄As)₂[Tc(NO)(NCS)₅] having a 4 t low-spin configuration are reported. The EPR parameters g?, Ã^Tc as well as ligand hyperfine data are used to analyze the bonding properties. The isotropic parameters g₀ and a are found to be clearly correlated to the composition of the coordination sphere. Therefore, they can be used to characterize mixed-ligand complexes unambiguously. The formation of mixed-ligand complexes was investigated for ligand-exchange reactions on [Tc(NO)Cl₅]^2? and [Tc(NO)Br₄]^?. In these investigations unsaturated dichalcogeno ligands are included.     

Geometric structure and electronic properties of neutral and anionic Fe2C3 and Fe2C4 clusters, as obtained by density-functional calculations

We calculated the geometrical structures and electronic properties of neutral and anionic Fe2Cn clusters (n = 3,4) using a density-functional method that employs linear combinations of atomic orbitals as basis sets, standard nonlocal norm-conserving pseudopotentials, and the generalized gradient approximation to exchange and correlation. We show that the ground-state structures of Fe2C3 and Fe2C4 are essentially the same in the neutral and anionic states, namely, planar rings that feature nonadjacent Fe atoms. For the anionic clusters, these findings contrast with previously published results.     

Studies in polyphenol chemistry and bioactivity. 4.(1) Synthesis of trimeric,tetrameric, pentameric,and higher oligomeric epicatechin-derived procyanidins having all-4beta,8-interflavan connectivity and their inhibition of cancer cell growth through cell cycle arrest

We report an improved synthesis of bis(5,7,3',4'-tetra-O-benzyl)epicatechin 4beta,8-dimer (3) from 5,7,3',4'-tetra-O-benzylepicatechin (1) and 5,7,3',4'-tetra-O-benzyl-4-(2-hydroxyethoxy)epicatechin (2) by replacing the previously employed Lewis acid, titanium tetrachloride, with the clay mineral Bentonite K-10. Under the same conditions, the benzyl-protected all-4beta,8-trimer, -tetramer, and -pentamer were obtained regioselectively from their lower homologues, albeit in rapidly decreasing yields. Reaction of 2 with an organoaluminum thiolate generated from 2-mercaptobenzothiazole and trimethylaluminum followed by acetylation produced 3-O-acetyl-4-[(2-benzothiazolyl)thio]-5,7,3',4'-tetra-O-benzylepicatechin (12). Medium-sized protected oligomers with 4beta,8-interflavan linkages are obtained in improved yields by using this compound as the electrophile and silver tetrafluoroborate as activator and are isolated by reversed-phase HPLC. Their deprotection by ester saponification followed by hydrogenolysis yielded the free procyanidins, which were characterized as their peracetates. The synthetic procyanidins are identical by normal-phase HPLC with fractions isolated from cocoa. The principle of chain extension by two members was demonstrated using a dimeric electrophile obtained by self-condensation of compound 12. Both the synthetic and natural pentamer 32 inhibit the growth of several breast cancer cell lines. Using the MDA MB 231 line, it was established that this outcome is based on the induction of cell cycle arrest in the G0/G1 phase. Subsequent cell death is more likely necrotic rather than apoptotic. Control experiments demonstrate that the polyphenol itself, rather than hydrogen peroxide potentially formed by its autoxidation, is the causative agent.     

PI Mtoyoura: a new PI M subtype found by separator and hybrid isoelectric focusing

In the course of a population study of alpha 1-antitrypsin polymorphism by separator isoelectric focusing, a variant phenotype having a somewhat narrower spacing than PI M1M3 was observed in a Japanese blood donor. Family studies by hybrid isoelectric focusing in a carrier ampholyte-supplemented immobilized pH gradient from 4.35-4.65 revealed that the products of the responsible gene, PI*Mtoyoura, were extremely close but slightly cathodal to those of PI*M1. The difference in isoelectric point between them corresponded to the resolving limit of isoelectric focusing. For this reason, although the propositus' father was deduced to have the genotype PI*M1/PI*Mtoyoura, the products of these two genes failed to form a double band pattern. Thus, the gene frequency for PI*Mtoyoura was unknown. These findings, however, indicate that a further microheterogeneity in the PI M subtype exists at least in the Japanese.     

Determination of nitric acid concentration by using europium ion fluorescence

A method is presented for the determination of 2-10M nitric acid based on the fact that the presence of high nitric acid concentration causes an enhancement of the intensity of some bands in the fluorescence spectra of rare earth ions in solution. The 616-nm band of Eu(3+) shows the most dramatic intensity enhancement with increasing nitric acid concentration. The present method, based on the measurement of the ratio of Eu(3+) fluorescent band intensities is shown to be independent of Eu(3+) concentration and relatively free of interference. This robust method allows the presence of an interferent to be determined from the experimental data.     

Performance,data and results with various chromatographic systems and various detection patterns in high-performance thin-layer chromatography

Summary A knowledge of the relationships between particle size and layer thickness on the one hand and migration distance and plate height on the other has prompted the development of the pre-coated HPTLC plate for nano-TLC. A separation performance which is very high with respect to time is achieved with a migration distance of 3–7 cm with a plate height of about 12 m and several thousand theoretical plates, thanks to the possibility of simultaneous chromatography. In HPTLC quantitative evaluation, standardised chromatographic conditions are essential. In this context the complex influences of different types of chamber and solvents on linear and circular chromatography are described. Various methods of conditioning the adsorbent by immersion impregnation, as well as detection procedures are discussed. The scope for varying TLC procedures and the advantages of TLC in general are listed.     

Studies on the analytical chemistry of iodonium compounds. Part. VII

Summary A procedure is described for the determination of 0.2–3.5 mg of the diphenyliodonium cation by extraction of its hexathiocyanatoferrate(III) Complex from slightly acidic solution into 1,2-dichloroethane. Absorbance measurements are made directly on the organic extract at 485 nm. Beer's law is not obeyed and a calibration curve must be used.

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Zusammenfassung Ein Verfahren für die Bestimmung von 0,2 bis 3,5 mg Diphenyljodoniumkation durch Extraktion seines Hexathiocyanatoferrat(III)-komplexes aus sehwach saurer Lösung mit 1,2-Dichloräthan wurde beschrieben. Die Absorption des organischen Extraktes wurde unmittelbar bei 485 nm gemessen. Das Beersche Gesetz ist nicht anwendbar, weshalb man eine Eichkurve verwenden muß.

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Part VI: Mikrochim. Acta [Wien]1967, 564. The work reported in this paper forms part of a thesis submitted byAnthony J. Bowd to the Faculty of Science of the University of London in partial fulfilment of the requirements for the degree of Doctor of Philosophy.     

Bistrifluoromethylcyclopropenes

Hexafluorobut-2-yne reacts with dichlorocarbene [generated by thermal decomposition of the silane CC1₃SiF₃] to give 3,3-dichlorobistrifluoromethyl- (I) and 1,3-dichlorobistrifluoromethyl-cyclopropene (II).

The 3,3-dichloro-compound (I) is isomerised to (II) by heat, light, or chemical catalysis, but high yields of either pure cyclopropene may be obtained by modification of the reaction conditions. The cyclopropenium ion (III) is formed when either (I) or (II) is treated with antimony pentafluoride.Both (I) and (II) undergo free-radical addition of halogens, but the slow reaction of (II) with trifluoromethyl radicals gives a mixture of products. Nucleophilic substitution of chloride ion from both cyclopropenes occurs very readily, and with ethoxide ions both mono- and di-ethoxybistrifluoromethylcyclopropenes are obtained. The cyclopropenes also react with fluoride ion, iodide ion, or Grignard compounds.