In search of female sterility causes in the tetraploid and pentaploid cytotype of Pilosella brzovecensis (Asteraceae)

Within the agamic Pilosella complex, apomixis (asexual reproduction through seed) involves apospory, parthenogenesis, and autonomous endosperm development. Observations of reproductive biology in P. brzovecensis throughout four growing seasons in the garden have shown that both tetraploid and pentaploid plants of this species do not produce viable seeds and reproduce exclusively vegetatively by underground stolons. The reasons for the seed development failure were unknown, therefore our research focused on the analysis of reproductive events in the ovules of this taxon. We found that apospory was initiated in the ovules of both cytotypes. Multiple aposporous initial (AI) cells differentiated in close proximity to the megaspore mother cell (MMC) and suppressed megasporogenesis at the stage of early prophase I. However, none of the AI cells was able to further develop into a multi-nucleate aposporous embryo sac (AES) due to the inhibition of mitotic divisions. It was unusual that callose was accumulated in the walls of AI cells and its synthesis was most likely associated with a response to the dysfunction of these cells. Callose is regarded as the isolating factor and its surprising deposition in the ovules of P. brzovecensis may signal disruption of reproductive processes that cause premature termination of the aposporous development pathway and ultimately lead to ovule sterility. The results of our embryological analysis may be the basis for undertaking advanced molecular studies aimed at fully understanding of the causes of female sterility in P. brzovecensis.

     

Synthesis and Mass Spectrometry Analysis of Mimosine-Containing Peptides

Non-proteinogenic amino acids are widely explored group of compounds due to their chemical properties and great potential of application in the combinatorial chemistry, medicinal investigation etc. Therefore the synthetic methods of their incorporation to the peptide chain are required. l-Mimosine, (S)-α-amino-β-(3-hydoxy-4-oxo-1,4-dihydropyridin-1-yl)-propanoic acid), is a plant amino acid, known to induce apoptosis in human pancreatic cancer xenografts. Here we present our investigations on the synthesis of mimosine-containing peptide and their ESI-MS/MS analysis. We successfully applied Fmoc-protected mimosine a with a free hydroxy ketone group for efficient peptide synthesis in the presence of HATU as a coupling reagent without the formation of side products. Additionally the tandem mass spectrometry analysis revealed the characteristic loss of the heterocyclic ring from mimosine residue side chain. The described method allows insertion of mimosine residue at any endo-position within a peptide sequence. The obtained results may be useful in the synthesis and mass spectrometry analysis of various mimosine-containing peptides.

     

Changes in Electric Properties of Human Breast Cancer Cells

Studies of the electrical surface properties of biological cells have provided fundamental knowledge about the cell surface. The change in biological functions of cells may affect the surface properties and can be detected by electrokinetic measurements. The surface density of fibroblasts and breast cancer cells (MDA-MB-231 and MCF-7) as a function of pH was measured by electrophoresis. The interaction between solution ions and the breast cancer cell or fibroblast surface was described by a four-component equilibrium model. The agreement between the experimental and theoretical charge variation curves of the breast cancer cells and fibroblasts was good at pH 2.5–9. The extent of fibroblast and breast cancer cell lipid peroxidation was estimated by HPLC measurement of the malondialdehyde level. The acid (C _TA) and basic (C _TB) functional group concentrations and the average association constant with hydroxyl (K _BOH) ions values of the breast cancer cell membranes were higher than in normal cells, while the average association constant with hydrogen (K _AH) value was smaller. The level of lipid peroxidation products was higher in breast cancer cells than in normal cells.     

Molecular studies did not support the distinctiveness of Malva alcea and M. excisa (Malvaceae) in Central and Eastern Europe

Relics of Malva alcea are found in Central and Western Europe. A similar taxon, M. excisa, is native to the eastern parts of Europe. According to selected sources, the geographical range boundary of the above taxa intersects Poland. Taxonomic research relying on key morphological features (the depth of corolla petal incisions and the type of hairs covering the stem) did not clearly validate the distinctness of those species. Genetic variation between Malva alcea and M. excisa was analyzed using ISSR and ISJ markers. The performed analysis did not reveal statistically significant differences at the level of genetic diversity between M. alcea and M. excisa populations. The obtained genetic identity values (I = 0.985) do not support the identification of eastern populations as a distinct biological species of M. excisa. The applied DNA markers did not reveal species-specific bands supporting molecular identification of those taxa. The obtained genetic identity values were verified by neighbor-joining grouping which showed that M. alcea and M. excisa did not form corresponding clusters, thus pointing to an absence of significant differences between the analyzed taxa. Differences between the above species were not revealed by an analysis of the sequences of chloroplast regions trnHpsbA and rpoC1, either.     

Structure of muramic acid TMS derivative mass spectrum's base ion (m/z=185) used for quantification of bacterial peptidoglycan.

The use of trimethylsilyl (TMS)-derivatisation for determining muramic acid in environmental and clinical samples by gas chromatography-mass spectrometry provides high detection sensitivity; however, questions have been raised as concerns the chemical structure of the entity giving the strong signal of m/z 185. In the present communication we present evidence that this entity results from the formation of a lactam structure of muramic acid upon derivatisation.     

Proteins at atomic resolution

Experimental advances in data collection, including bright sources, cryogenic cooling and two-dimensional detectors, have made it tractable to record data to beyond 1.2 Å for several proteins, yielding high-accuracy models and fine details of structure. For small metalloproteins, atomic-resolution data have enabled ab initio solution of the phase problem.