Determination of nucleotides, nucleosides and nucleobases in cells of different complexity by reversed-phase and ion-pair high-performance liquid chromatography

Procedures are presented for the analysis of profiles of purine and pyridine compounds in human and rabbit red blood cells by reversed-phase high-performance liquid chromatography and in Ehrlich ascites tumour cells of mouse by ion-pair high-performance liquid chromatography. These compounds are present in rabbit erythrocytes in higher concentrations than in human blood cells, and in rabbit reticulocytes the concentration of purine compounds is still higher. During glucose-free incubation, human red cells accumulate adenosine and adenine in the presence of coformycin owing to the inhibition of adenosine and AMP deamination. Ehrlich ascites tumour cells lose major portions of purine mono-, di- and triphosphates between the seventh and eleventh day after inoculation into mouse peritoneal cavities.     

Influence of hydrostatic pressure on the polarization dynamics of order-disorder ferroelectrics: AgNa(NO2)2

The characteristic ferroelectric dispersion of the complex dielectric constant of the ferroelectric AgNa(NO₂)₂ is measured as function of temperature and hydrostatic pressure. For the first time the temperature and pressure dependences of the static order parameter susceptibility and the order parameter relaxation time could be reproducibly determined. The results are interpreted in terms of a kinetic Ising model, whose parameters show a characteristic pressure dependence. The results are discussed on the basis of thermodynamic relations and related to the dynamical behaviour of other order-disorder ferroelectrics.     

High resolution X ray spectroscopy in light antiprotonic atoms

At the LEAR facility, CERN, antiprotonic Lα transitions in light elements have been investigated with a focussing crystal spectrometer. The high resolution of the experiment allowed for the first time to resolve in H the 2³P₀ state from the close lying states 2³P₂, 2¹P₁, and 2³P₁. In D the corresponding transitions were found to be more than an order of magnitude broader. To a large extent the results for H support the meson exchange model. This revised version was published online in August 2006 with corrections to the Cover Date.     

Metabolic differences among melanoma and two prostate cancer cell lines by electrospray ion mobility mass spectrometry

Detecting early stages of cancer has been a challenge for analytical methods. Even with the advances in mammography and prostate specific antigen (PSA) testing the number of false positives and negatives is still significant. Cancer cell lines provide realistic simulations to assess detection technologies for different stages and types of cancer. Metabolomics, the measure of end products of all biological processes, is a recent addition to the field of systems biology and can be targeted towards early disease detection. For this study, the metabolomes of three cancer cell lines, two prostate (DU145 and PC3) and one melanoma (A375), were investigated by an ion mobility mass spectrometer (IMMS) for both positive and negative ion detection mode. IMMS produced multidimensional data that includes m/z, mobility and intensity for each ion detected in the sample. In order to see differences between the cancer cell lines, principal components analysis (PCA), a multi-variant technique used to pull patterns out of the data, was used in conjunction with the IMMS data. The sample patterns from the PCA were observed in the score plot and the individual metabolites that contributed the most to the model were shown in the loadings plot. For positive mode 127 metabolite ions were statistically analyzed and in the negative mode 115 metabolite ions were analyzed. PCA score plots were able to model 98% and 87% of the original data for positive and negative mode, respectively. The metabolite ions from the loadings plot were tentatively identified based on m/z.