Silicon isotope separation utilizing infrared multiphoton dissociation of Si<Subscript>2</Subscript>F<Subscript>6</Subscript> irradiated with two-frequency CO<Subscript>2</Subscript> laser lights

Silicon isotope separation has been performed utilizing the infrared multiphoton dissociation (IRMPD) of Si₂F₆ irradiated with two-frequency CO₂ laser lights. The two-frequency excitation method improved the separation efficiency by keeping the high enrichment factors. For example, Si₂F₆ with the ²⁸Si fraction of 99.4% was obtained at 40.0% dissociation of Si₂F₆ after the simultaneous irradiation of 100 pulses with 966.23 cm^-1 photons (0.089 J/cm²) and 954.55 cm^-1 photons (0.92 J/cm²), while 1000 pulses were needed to obtain 99.0% of ²⁸Si at 27.2% dissociation in the case of single frequency irradiation at 954.55 cm^-1 (0.92 J/cm²). The single-step enrichment factors of ²⁹Si and ³⁰Si increased with increasing Si₂F₆ pressure. The reason for this enhancement has been discussed in terms of the rotational and vibrational relaxations by collisions with ambient gases. PACS 42.62.Cf; 82.30.Lp; 82.50.Bc     

The fibril structure of type V collagen triple-helical domain

Although the triple-helical structure of fibrillar collagen is regarded in general as being quite similar, each type of collagen molecule has inherent characteristics in the triple-helical domain. Few studies have ever been performed in terms of the aggregate structure of the triple-helical domain of fibrillar collagen. Reconstituted aggregates from the purified triple-helical domain of each type of fibrillar collagen might amplify the subtle differences in the structural characteristics of each type of collagen molecule. In this study, the reconstituted aggregate structure of pepsin-treated type V collagen (type Vp collagen), that is, virtually its triple-helical domain was characterized by transmission electron microscopy. Pepsin-treated type I (type Ip) and type II (type IIp) collagen were compared with type Vp collagen. Unique features of the aggregate structure of the triple-helical domain of the type V collagen can be summarized as follows:These results suggested that the lateral packing of the triple-helical domain of type V collagen is determined by its molecular structure. The characteristics of type Vp collagen fibrils might be explained by their characteristic amino acid composition. A significant feature of the triple-helical domain of type V collagen is the high content of glycosylated hydroxylysine residues. Molecular model building of the collagenous structure suggests that a change in surface roughness is conspicuous by incorporating the glycosylated hydroxylysine residues. More than a ten-fold content of bulky glycosylated hydroxylysine residues in type V collagen compared to that of type I might have a significant influence on both the intermolecular and interfibrillar interactions of the triple-helical domain of type V collagen molecule.     

Photoelectron spectra and orbital assignments by sum rule consideration: Ethyl and n-propyl fluorides

The He I photoelectron (PE) spectra of C₂H₅F and n-C₃H₇F have been obtained. The PE spectra indicate that the first ionization potentials are about 0.4 eV higher than those of the parent alkanes owing to the inductive effect of fluorine. All the PE bands obtained here have been interpreted in terms of appropriate p-type localized MO's using the sum rule described previously by the authors. Orbital energy diagrams involving the inductive effect of fluorine are illustrated. The semi-empirical CNDO/2 and MINDO/2 methods were also employed to help confirm the present orbital assignments.     

Zeeman levels with exotic field dependence in the high field phase of an S=1 Heisenberg antiferromagnetic chain

We have performed electron spin resonance measurements over a wide frequency and magnetic field range on a single crystal of the S=1 quasi-one-dimensional Heisenberg antiferromagnet Ni(C5H14N2)2N3(PF6). We observed gapped excitation branches above the critical field H(c) where the Haldane gap closes. These branches are analyzed by a phenomenological field theory using the complex-field phi(4) model. A satisfactory agreement between experiment and theory is obtained.     

A new flow-injection determination of glucose based on the redox reaction of hydroquinone with iron(III) in the presence of 1,10-phenanthroline

A new spectrophotometric flow-injection (FI) method is proposed for the determination of glucose based on the redox reaction of hydroquinone with iron(III). When a glucose solution containing quinone is passed through the immobilized glucose oxidase column introduced in FI system, quinone is reduced to hydroquinone by glucose. In the presence of 1,10-phenanthroline (phen), iron(III) is then quantitatively reduced by hydroquinone to iron(II) followed by the formation of iron(II)-phen complex (λ_max=510 nm). An FI peak observed at 510 nm corresponds to the concentration of glucose. The wide dynamic range for glucose was obtained in the range of 1×10⁻⁶–1×10⁻³ mol l⁻¹ at a sampling rate of 24 h⁻¹ and the detection limit (S/N=3) was 5×10⁻⁷ mol l⁻¹. Relative standard deviations were 0.78, 0.44 and 0.23% (n=5) for 5×10⁻⁶, 5×10⁻⁵ and 5×10⁻⁴ mol l⁻¹ of glucose, respectively. The proposed method was successfully applied to the determination of glucose in control blood sera, human blood plasma and wine.     

Determination of linuron in water samples by high performance liquid chromatography after preconcentration with octadecyl silanized magnetite

A sensitive and selective batch adsorption method is proposed for the preconcentration and determination of linuron. Linuron was preconcentrated on octadecyl silanized (ODS) magnetite as an adsorbent and then determined by high performance liquid chromatography (HPLC). Several parameters on the recovery of the analyte were investigated. The experimental results showed that it was possible to obtain sufficient preconcentration efficiency when the solution pH was 6 using 100 mL of sample solution containing 1.0 μg of linuron and 3 mL of ethanol as a desorption solution. Recovery of linuron was 50.7 ± 1.9% with a relative standard deviation for five determinations of 3.0% under optimum conditions. The calibration curve of linuron was linear up to 200 ng mL^− 1 with a correlation coefficient of 0.998 and the detection limit (3S/N) was 1.0 ng mL^− 1. The capacity of the adsorbent was also examined and found to be 0.15 mg g^− 1 for linuron. ODS-magnetite is suitable for repeated use without decreasing recovery at least 4 adsorption–desorption cycles. The proposed method was successfully applied to the determination of linuron in river water with high precision and accuracy.     

A powerful,novel, multiplex typing system for six short tandem repeat loci and the allele frequency distributions in two Japanese regional populations

A new multiplex system for six tetranucleotide short tandem repeat (STR) loci was devised based on multicolor dye technology. Six loci (D20S480, D6S2439, D6S1056, D9S1118, D4S2639, and D17S1290), each with high discriminating power (each unbiased estimates of expected heterozygosity, Exp. Hz, > 0.80 in a preliminary test), were selected from more than 100 tetranucleotide STRs included in a commercially available primer set. These loci were also selected so as not to link with general STRs in commercially released kits including the combined DNA index system (CODIS) 13 core STRs. The primers were newly designed in the present study, in which each amplicon size had a range of less than 200 base pairs (bp), in order to genotype from highly degraded template DNA. Using this system, we genotyped 270 Honshu (mainland)-Japanese and 187 Okinawa-Japanese. From these allele frequencies, we performed three tests, a homozygosity test, a likelihood ratio test and an exact test for Hardy-Weinberg equilibrium (HWE), and no significant deviations (p < 0.05) from HWE were observed. We also compared the allele distributions at six STRs between both populations, and they were significantly different (p < 0.05) at three loci (D6S2439, D9S1118 and D4S2639). Furthermore, the Exp. Hz and the power of discrimination (PD) at all loci in the Honshu-Japanese population were higher than 0.80 and 0.93, respectively. These statistical values for discriminating power in the Honshu-Japanese were almost the same as in the Okinawa-Japanese. This novel, multiplex polymerase chain reaction (PCR) amplification and typing system for six STR loci thus promises to be a convenient and informative new DNA profiling system in the forensic field.     

One-pot synthesis of 2,3-disubstituted benzofurans from 2-chlorophenols using palladium–dihydroxyterphenylphosphine catalyst

2,3-Disubstituted benzofurans possessing 2-hydroxyphenyl moiety at the C-3 position were synthesized from readily available 2-chlorophenols and terminal alkynes by hydroxy-directed ortho-Sonogashira coupling and subsequent oxypalladation/reductive elimination, using Pd-dihydroxyterphenylphosphine catalyst. The catalyst accelerates not only the Sonogashira coupling but also the introduction of 2-hydroxyphenyl group at the C-3 position of benzofuran.     

Viewing of complex molecules of ethidium bromide and plasmid DNA in solution by atomic force microscopy

Tertiary structure changes in plasmid DNA, induced by ethidium bromide intercalation, have been observed in aqueous solutions by the use of an atomic force microscope. A relaxed closed circular pBR322 molecule became a positively supercoiled complex on the drug binding. The supercoiling always resulted in an interwound (or a plectonemic) form, but never a solenoidal (or a toroidal) form. A quantitative analysis of the compactness of such supercoiled complexes has been carried out.