NMR and MO Studies on the Molecular Structure of a Fluoranthene-Benzene Complex

Fluoranthene (FA) forms a 1:1 van der Waals complex with benzene in cyclohexane. The ¹H NMR spectrum of this complex shows that the FA moiety in the complex state has five kinds of hydrogen atoms and that the ¹H NMR peaks assigned to the protons attached to the naphthalene skeleton are largely shifted to higher magnetic field on complex formation with benzene. These observations indicate that the complex takes the structure of C_S symmetry, in which the benzene molecule mainly interacts with the electronic system localized on the naphthalene moiety of FA. The present ab initio calculations reproduce well the ¹H NMR spectral shifts mentioned above and the experimentally predicted C_S structure of the complex. According to the PPP calculations for the electronic absorption spectral changes on the complex formation, the FA-benzene complex is considered to take a sandwich type structure.     

Electrophoretic mobility of a soft particle in a salt-free medium

A theory is presented for the electrophoretic mobility mu of dilute spherical soft particles (i.e., polyelectrolyte-coated particles) in salt-free media containing only counterions. As in the case of other types of particles (rigid particles and liquid drops) in salt-free media, there is a certain critical value of the particle charge separating two cases, the low-surface-charge case and the high-surface-charge case. For the low-charge case, the mobility is proportional to the particle charge and coincides with that of a soft particle in an electrolyte solution in the limit of very low electrolyte concentrations kappa-->0 (Hückel's limit), where kappa is the Debye-Hückel parameter. For the high-charge case, however, mu becomes essentially constant, independent of the particle charge, due to the counterion condensation effect.     

Effect of Coriolis force on counter-current chromatographic separation by centrifugal partition chromatography

The effect of Coriolis force on the counter-current chromatographic separation was studied using centrifugal partition chromatography (CPC) with four different two-phase solvent systems including n-hexane-acetonitrile (ACN); tert-butyl methyl ether (MtBE)-aqueous 0.1% trifluoroacetic acid (TFA) (1:1); MtBE-ACN-aqueous 0.1% TFA (2:2:3); and 12.5% (w/w) polyethylene glycol (PEG) 1000-12.5% (w/w) dibasic potassium phosphate. Each separation was performed by eluting either the upper phase in the ascending mode or the lower phase in the descending mode, each in clockwise (CW) and counterclockwise column rotation. Better partition efficiencies were attained by the CW rotation in both mobile phases in all the two-phase solvent systems examined. The mathematical analysis also revealed the Coriolis force works favorably under the CW column rotation for both mobile phases. The overall results demonstrated that the Coriolis force produces substantial effects on CPC separation in both organic-aqueous and aqueous-aqueous two-phase systems.     

Spectral variations in background light emission of surface-enhanced resonance hyper Raman scattering coupled with plasma resonance of individual silver nanoaggregates

We demonstrate the origin of spectral variations in background light emission of surface enhanced resonance hyper Raman scattering (SERHRS) from single Ag nanoaggregates. Ag nanoaggregate-by-nanoaggregate variations in background light emission spectra are related to plasma (plasmon) resonance spectra. Temporal variations in background light emission spectra with temporal blueshifts in plasma resonance spectra are also observed under continuous laser excitation. Both types of the variations in background light emission are reproduced by multiplying background light emission spectra measured from a Ag microaggregate by Lorentz function spectra derived from plasma resonance spectra. The reproduction reveals that second electromagnetic (EM) enhancement by plasma resonance is the origin of the variations. Additionally, spectral variations in background light emission of SERHRS are similar to that of surface enhanced resonance Raman scattering (SERRS). The similarity indicates that both types of background light emission commonly obtain second EM enhancement from identical plasma resonance.     

Analytical aspects of cyanobacterial volatile organic compounds for investigation of their production behavior

In order to fully understand the role of volatile organic compounds (VOCs) under natural conditions, an adaptable analytical method was developed as the first step. β-Ionone, β-cyclocitral, 2-methyl-1-butanol and 3-methyl-1-butanol were simultaneously analyzed in addition to geosmin and 2-MIB using GC/MS with SPME. The slight modification of a known method allowed the simultaneous detection and quantification of these VOCs. The SIM of the 3-methyl-1-butanol was always accompanied by a shoulder peak, suggesting the presence of two compounds. In order to separate both compounds, the GC/MS conditions were optimized, and the additional peak was identified as 2-methyl-1-butanol by direct comparison of the authentic compound, indicating that the Microcystis strain always produces a mixture of 2-methyl-1-butanol and 3-methyl-1-butanol. Furthermore, it was found that 2-methyl-1-butanol and 3-methyl-1-butanol were predominant in the dissolved fractions. β-Cyclocitral was easily oxidized to provide the oxidation product, 2,6,6-trimethylcyclohexene-1-carboxylic acid, which causes the blue color formation of cyanobacteria as a consequence of acid stress. The intact acid could be satisfactorily analyzed using the usual GC/MS without derivatization.     

Characterization of a mesophilic aliphatic-aromatic copolyester-degrading fungus

We isolated 5 mesophilic microorganisms that form clear zones around the colony on an opaque medium containing the aliphatic-aromatic copolyester poly(60 mol% butylene adipate-co-40 mol% butylene terephthalate) (PBAT). Among all strains, the fungal strain NKCM1712 degraded PBAT at the fastest rate (3.5 ± 0.3 μg cm⁻² h⁻¹). Genetic and morphological analyses revealed that this strain was closely related to Isaria fumosorosea (phylum Ascomycota). Mass spectroscopic analysis revealed that the degradation products were T, AB, TB, BAB, and ABT (T, terephthalic acid unit; A, adipic acid unit; B, 1,4-butanediol unit)] in the culture of the strain that used PBAT as the sole carbon source. Furthermore, the PBAT degradation ability of this strain in terms of BOD suggested that it could utilize the PBAT degradation products as growth substrates. This is the first report of a mesophilic strain that can mineralize an aliphatic-aromatic polyester into carbon dioxide on its own.     

Chiral ligand-controlled asymmetric conjugate addition of lithium amides to enoates

The external chiral ligand-controlled asymmetric conjugate addition reaction of lithium amides with alpha,beta-unsaturated esters provided beta-amino esters in high yields and high enantioselectivities.     

Electrophoretic mobility of a charged cylindrical colloidal particle covered with an ion-penetrable uncharged polymer layer

Expressions are derived for the electrophoretic mobility of a cylindrical charged colloidal particle carrying a low zeta potential covered with an ion-penetrable uncharged polymer layer in an electrolyte solution. These expressions involve numerical integration of modified Bessel functions but are easily calculable with Mathematica. The obtained mobility expressions are a modification of Henry's mobility formula for a cylindrical particle taking into account the presence of the uncharged polymer layer.