Carbon-13 chemical shifts of α,β-unsaturated acids

Carbon-13 spectra of 59 α,β-unsaturated carboxylic acids have been measured. Large differential shieldings of ethylenic carbons in the cis and trans isomers of acrylic acid derivatives were found (altogether 15 isomeric Z- and E-pairs of acids were investigated). The origin of differential shieldings is complex and both molecular ground states as well as changes in excited states appear to be involved. All measured ¹³C chemical shifts can be described by additive parameters that provide a straightforward new technique by which structural assignments can be made for a wide variety of isomeric mono-, di- and tri- substituted α,β-unsaturated acids.     

New labdane diterpenes from Solidago canadensis

The ethanol extract of roots of Solidago canadensis yielded eight labdane-type diterpenes. Five of those were new natural compounds (9,13,15,16-bisepoxy-labdane-7-ene-6,15-dione (3a), 13-epi-9,13,15,16-bisepoxy-labdane-7-ene-6,15-dione (3b), 15,16-epoxy-labdane-7,13-diene-6,16-dione (5), 15-ethoxy-9,13,15,16-bisepoxy-labdane-7-ene-6-one (6a) and 13-epi-15-ethoxy-9,13,15,16-bisepoxy-labdane-7-ene-6-one (6b). The known labdane diterpenes deoxysolidagenone (1), solidagenone (2) and 15,16-epoxy-labdane-7,13-diene-6,15-dione (4) were also isolated. Chemical structures were determined using 1D and 2D NMR techniques and MS analysis.     

In situ photoemission study of Pr1-xCaxMnO3 epitaxial thin films with suppressed charge fluctuations

We have performed an in situ photoemission study of Pr1-xCaxMnO3 (PCMO) thin films grown on LaAlO3 (001) substrates and observed the effect of epitaxial strain on the electronic structure. We found that the chemical potential shifted monotonically with doping, unlike bulk PCMO, implying the disappearance of incommensurate charge fluctuations of bulk PCMO. In the valence-band spectra, we found a doping-induced energy shift toward the Fermi level (EF) but there was no spectral weight transfer, which was observed in bulk PCMO. The gap at EF was clearly seen in the experimental band dispersions determined by angle-resolved photoemission spectroscopy and could not be explained by the metallic band structure of the C-type antiferromagnetic state, probably due to localization of electrons along the ferromagnetic chain direction or due to another type of spin-orbital ordering.     

Study of the dimethyl ester of nitromalonic acid and some of its derivatives by the NMR method on13C and14N nuclei

Conclusions The data of the¹³C and¹⁴N NMR spectra testify to the strong delocalization of the charge in the anion of the dimethyl ester of nitromalonic acid, and to the averaging of the NO bonds in the trimethylsilyl ether of biscarbomethoxymethanenitronic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 188–190, January, 1972.     

Simplified and rapid method for extraction of ergosterol from natural samples and detection with quantitative and semi-quantitative methods using thin-layer chromatography

A new and simplified method for extraction of ergosterol (ergosta-5,7,22-trien-3beta-ol) from fungi in soil and litter was developed using pre-soaking extraction and paraffin oil for recovery. Recoveries of ergosterol were in the range of 94-100% depending on the solvent to oil ratio. Extraction efficiencies equal to heat-assisted extraction treatments were obtained with pre-soaking extraction. Ergosterol was detected with thin-layer chromatography (TLC) using fluorodensitometry with a quantification limit of 8 ng. Using visual evaluation of images of TLC plates photographed in UV-light the quantification limit was 16 ng.     

Zum Aufbau schlecht geordneter Calciumhydrogensilicate. VII. 29Si-NMR-Untersuchungen an C?S?H(Di,Poly)

On the Structure of Ill-crystallized Calcium Hydrogen Silicates. VII. Solid State ²⁹Si N.M.R. Studies on C? S? H(Di, Poly) High-resolution solid-state MAS ²⁹Si n.m.r. studies prove that C? S? H(Di, Poly) contains end and middle group SiO₄ tetrahedra (di- and polysilicate) only. Further on it is shown that the ratio of OH groups linked to polysilicate to such linked to disilicate anions is constant in the region 1–1.5 CaO/SiO₂ but decreases with increasing temperature of formation of C? S? H(Di, Poly).     

Early prediction of wheat quality: analysis during grain development using mass spectrometry and multivariate data analysis

Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry and multivariate data analysis have been used for the determination of wheat quality at different stages of grain development. Wheat varieties with one of two different end-use qualities (i.e. suitable or not suitable for bread-making purposes) were investigated. The samples were collected from grains from 15 until 45 days post-anthesis (dpa). Gluten proteins from wheat grains were extracted and subsequently analysed by mass spectrometry. Discrimination partial least-squares regression and soft independent modelling of class analogy were used to determine the quality of new and unknown wheat samples. With these methods, we were able to predict correctly the end-use qualities at every stage investigated. This new fast technique, based on the rapidity of mass spectrometry combined with the objectivity of multivariate data analysis, offers a method that can replace the traditional rather time-consuming ones such as gel electrophoresis. This study focused on the determination of wheat quality at 15 dpa, when the grain is due for harvest 1 month later.