Gasförmige Acetate

Gaseous Acetates Thermoanalytical and mass-spectrometrical observations are undertaken with some acetates and oxiacetates. The volatilization of copper(I) acetate takes place like that of the silver acetate as M₂Ac₂⁺ (besides the deposition of Ag). On the volatilization of the anhydrous compounds Cu₂Ac₄, Cr₂Ac₄, Rh₂Ac₄, and Mo₂Ac₄ in the vacuum of a mass spectrometer is observed that Cu₂Ac₄ vaporizes dissociative as Cu₂Ac₂⁺ (+ 2 “Ac”), while the other compounds vaporize as M₂Ac₄⁺ and simultaneously is formed an oxidic (e.g. Cr₂O₄) or metallic residue. PdAc₂ vaporizes in the mass spectrometer as a trimeric molecule Pd₃Ac₆. M₄OAc₆, which is formed from the dihydrates, vaporizes in a mass spectrometer with M ? Co, Mn as M₄OAc₆⁺. Other complexes of the same type appear as Be₄OAc₅⁺, Mg₄OAc₅⁺, and Zn₄OAc₅⁺.     

Routine measurement of plasma catecholamines in clinical pharmacology by high-performance liquid chromatography with electrochemical detection

A method for the simultaneous determination of epinephrine, norepinephrine and dopamine in human plasma is described, which combines the advantages of liquid-liquid extraction sample preparation, high-performance liquid chromatography on weak cation-exchange stationary phases and dual-electrode coulometric detection. The limits of quantification are less than 5 pg/ml (at a signal-to-noise ratio greater than 5) for each analyte. The influence of various experimental parameters (e.g., composition of the mobile phase, pretreatment of the assay buffer, components of the re-extraction system) on the performance of the assay is reported in detail. A number of applications are presented, which demonstrate the quality of the data obtained in terms of sensitivity, reproducibility and significance.     

The Oracle

Experimental Techniques -     

Distinctive Molecular Abnormalities in Benign and Malignant Skin Lesions: Studies by Raman Spectroscopy

Abstract— Near-infrared Fourier transform Raman spectroscopy is an analytical, nondestructive technique that provides information about the molecular structure of the investigated sample. The molecular structure of proteins and lipids differs between neoplastic and normal tissues and therefore Raman spectroscopy has been considered promising for the diagnosis of cancer. We aimed to compare the molecular structure of normal skin, benign and malignant skin lesions by the near-infrared Fourier transform Raman spectroscopy. Biopsies were obtained from the following skin lesions: skin tag, dermatofibroma, seborrhoeic keratosis, actinic keratosis, keratoacan-thoma, basal cell carcinoma, squamous cell carcinoma, nevus intradermal, nevus compositus, dysplastic nevus and lentigo maligna. Control skin was harvested from the vicinity of these lesions. In the Raman spectra, the secondary structure of the proteins was reflected by the amide vibrations of peptide bonds. The principal lipid vibrations were twisting and wagging (CH₂) and CH stretching vibrations. Histologically distinguishable lesions showed specific combinations of band changes indicating alterations in the protein conformation and in the molecular structure of the lipids. Histogenetically related lesions (actinic keratosis and sqamous cell carcinoma) produced similar but not identical patterns of spectral changes. Because the examined skin lesions produced reproducible and unique spectra, we suggest that Raman spectroscopy will be useful for diagnosis of skin lesions.     

Molecular dosimetry of 8-MOP + UVA-induced DNA photoadducts in Saccharomyces cerevisiae: correlation of lesions number with genotoxic potential

Acid hydrolysis of purified DNA extracted from cells of a haploid repair-proficient (RAD) yeast strain that had been treated with 8-MOP + UVA revealed the existence of two major and one minor thymine photoproduct. At survival levels of the RAD strain between 100% and 1% furanside monoadducts constituted the major DNA lesion, followed by diadducts that, at the lowest survival level, nearly reached 50% of the thymine photoproducts; pyrone-side monoadducts were only detectable at the highest UVA exposure dose applied and clearly constitute a minority photoproduct. The number of induced diadducts was verified by determination of interstrand cross-links via denaturation and renaturation of 8-MOP + UVA-treated DNA from RAD and rad2 yeast strain. 8-MOP + UVA was shown to induce two types of locus-specific mutations: reversion of the lys1-1 ochre allele was between 20- to 50-fold higher than that of the his4-38 frameshift allele. Mutant yield for the lys 1-1 reversion was the same in RAD and excision repair-deficient rad2-20 strains whereas frameshift mutagenesis was about eightfold higher in the rad2-20 background.     

Synthesis and Crystal Structure of the First Thallium Hydrous Nesosilicate Tl4SiO4·0.5H2O

Orange prismatic crystals of the first thallium hydrous nesosilicate Tl₄SiO₄·0.5H₂O have been obtained by evaporation from aqueous solution. There are three symmetrically independent Tl⁺ cations and five symmetrically independent oxygen atoms in the structure of Tl₄SiO₄·0.5H₂O. The O(4) and O(5) atoms belong to water molecules. Coordination polyhedra of the Tl⁺ cations are strongly distorted because of the stereoactive behavior of lone electron pairs. The structure of Tl₄SiO₄·0.5H₂O contains sheets of SiO₄ tetrahedra and Tl coordination polyhedra. The sheets have the composition [Tl₃SiO₄]^– and are parallel to [100]. Within the sheets, SiO₄ tetrahedra link to thallium polyhedra though common corners. The sheets are linked by dimers of face‐sharing Tl(3)O₅ polyhedra, thus providing interconnection of the sheets into a framework. The framework has large elliptical channels occupied by water molecules (OW2) and electron pairs of Tl⁺ cations.The comparison with some other M⁺ (M = K, Ag, Tl) silicates is given.     

8-METHOXYPSORALEN INCREASES DAYTIME PLASMA MELATONIN LEVELS IN HUMANS THROUGH INHIBITION OF METABOLISM

Abstract It is well established that in healthy humans oral intake of 5-or 8-methoxypsoralen (5-and 8-MOP) is followed by a significant increase in plasma melatonin concentrations. The effect of psoralen on rat melatonin has been studied in vitro and in vivo and a stimulation of release or secretion from the pineal gland has been suggested. In this study we examined the time-related changes in plasma concentrations of 8-MOP, melatonin and 6-sulfatoxymelatonin in 15 patients admitted for routine psoralen plus UVA therapy. On the first day of treatment blood samples were collected before, and 30, 60 , 66 and 90 rnin after intake of 8-MOP (0.6 mg/kg). Although the rate of 8-MOP absorption vaned greatly, a significant increase ( P = 0.0002) in melatonin levels was found 60 min after 8-MOP intake. During UVA exposure a strongly correlated decrease in mean melatonin and mean 8-MOP concentrations was found, indicating an effect of UVA radiation, either direct or 8-MOP mediated, on circulating melatonin levels. Plasma 6-sulfatoxymelatonin concentrations decreased significantly between all time points, suggesting inhibition of melatonin metabolism.     

Particular topological complexity of lead oxide blocks in Pb31O22X18 (X = Br, Cl)

Dark-green platy crystals of the new compound Pb31O22Br10Cl8 (1) have been obtained by rapid quenching of a lead oxide halide melt. The structure of 1 (triclinic, P1, a = 12.1192(7) angstroms, b = 16.2489(10) angstroms, c = 18.3007(11) angstroms, alpha = 93.104(2) degrees, beta = 95.809(2) degrees, gamma = 111.252(1) degrees, V = 3325.4(3) angstroms3, Z = 2) can be viewed as incorporation of [PbX6]4- halide units (X = Br, Cl) into the defect PbO matrix. The latter represents a two-dimensional [O22Pb30]16+ cationic layer of OPb4 tetrahedra that can be derived from the [OPb] tetrahedral layer observed in tetragonal PbO. The layer consists of 22 symmetrically inequivalent OPb4 tetrahedra and represents the topologically most complicated arrangement of tetrahedra known to date.     

Structure and dynamics of water confined in dimethyl sulfoxide.

We study the structure and dynamics of hydrogen-bonded complexes of H2O/D2O and dimethyl sulfoxide (DMSO) by infrared spectroscopy, NMR spectroscopy and ab initio calculations. We find that single water molecules occur in two configurations. For one half of the water monomers both OH/OD groups form strong hydrogen bonds to DMSO molecules, whereas for the other half only one of the two OH/OD groups is hydrogen-bonded to a solvent molecule. The H-bond strength between water and DMSO is in the order of that in bulk water. NMR deuteron relaxation rates and calculated deuteron quadrupole coupling constants yield rotational correlation times of water. The molecular reorientation of water monomers in DMSO is two-and-a-half times slower than in bulk water. This result can be explained by local structure behavior.