The dynamics of the non-heme iron in bacterial reaction centers from Rhodobacter sphaeroides

AbstractWe investigate the dynamical properties of the non-heme iron (NHFe) in His-tagged photosynthetic bacterial reaction centers (RCs) isolated from Rhodobacter (Rb.) sphaeroides. Mössbauer spectroscopy and nuclear inelastic scattering of synchrotron radiation (NIS) were applied to monitor the arrangement and flexibility of the NHFe binding site. In His-tagged RCs, NHFe was stabilized only in a high spin ferrous state. Its hyperfine parameters (IS=1.06±0.01mm/s and QS=2.12±0.01mm/s), and Debye temperature (θD0~167K) are comparable to those detected for the high spin state of NHFe in non-His-tagged RCs. For the first time, pure vibrational modes characteristic of NHFe in a high spin ferrous state are revealed. The vibrational density of states (DOS) shows some maxima between 22 and 33meV, 33 and 42meV, and 53 and 60meV and a very sharp one at 44.5meV. In addition, we observe a large contribution of vibrational modes at low energies. This iron atom is directly connected to the protein matrix via all its ligands, and it is therefore extremely sensitive to the collective motions of the RC protein core. A comparison of the DOS spectra of His-tagged and non-His-tagged RCs from Rb. sphaeroides shows that in the latter case the spectrum was overlapped by the vibrations of the heme iron of residual cytochrome c2, and a low spin state of NHFe in addition to its high spin one. This enabled us to pin-point vibrations characteristic for the low spin state of NHFe

Dipoid-Specific Genome Stability Genes of S. cerevisiae: Genomic Screen Reveals Haploidization as an Escape from Persisting DNA Rearrangement Stress

Maintaining a stable genome is one of the most important tasks of every living cell and the mechanisms ensuring it are similar in all of them. The events leading to changes in DNA sequence (mutations) in diploid cells occur one to two orders of magnitude more frequently than in haploid cells. The majority of those events lead to loss of heterozygosity at the mutagenesis marker, thus diploid-specific genome stability mechanisms can be anticipated. In a new global screen for spontaneous loss of function at heterozygous forward mutagenesis marker locus, employing three different mutagenesis markers, we selected genes whose deletion causes genetic instability in diploid Saccharomyces cerevisiae cells. We have found numerous genes connected with DNA replication and repair, remodeling of chromatin, cell cycle control, stress response, and in particular the structural maintenance of chromosome complexes. We have also identified 59 uncharacterized or dubious ORFs, which show the genome instability phenotype when deleted. For one of the strongest mutators revealed in our screen, ctf18Δ/ctf18Δ the genome instability manifests as a tendency to lose the whole set of chromosomes. We postulate that this phenomenon might diminish the devastating effects of DNA rearrangements, thereby increasing the cell's chances of surviving stressful conditions. We believe that numerous new genes implicated in genome maintenance, together with newly discovered phenomenon of ploidy reduction, will help revealing novel molecular processes involved in the genome stability of diploid cells. They also provide the clues in the quest for new therapeutic targets to cure human genome instability-related diseases

Origin and Neoholocene evolution of spring-fed fens in Wardzyń, Łódź Upland, central Poland

Spring-fed fens in Wardzyń represent the rare group of alkaline mires supplied by artesian groundwater. Using multidisciplinary methods (including sedimentological, hydrometric and hydrochemical, pollen, macrofossil, malacological, geochemical, radiocarbon dating, and stable oxygen and carbon isotope analyses) we have been able to (1) reconstruct the main phases of spring-fed fen development, and to (2) determine the cause of Neoholocene groundwater ascension responsible for the mire inception. These phases are characterized by cyclic organic (peat) and carbonate (tufa) sedimentation associated with the Holocene fluctuations in humidity and temperature. The beginning of the activation of hydrological systems (involving the flow of confined groundwater of the Cretaceous aquifer) at Wardzyń occurred in the Subboreal period of the Holocene, after a long episode of decreased humidity initiated ca. 4.2 ka cal BP

Application of Spin Labels for Research of Vanadyl Acetylacetonate Concentration in Model Bilayer Membranes by EPR Spectroscopy

The compounds and complexes of vanadium are used to treat diabetes and cancer. Research on the effectiveness and mechanism of action of new derivatives of vanadium, and their toxicity is currently very intense. The research shows that the vanadium(IV) acetylacetonate complex [VO(acac)2] shows a synergism with insulin in treating diabetes, high pharmacological activity and low toxicity. In order to improve the effectiveness of drugs and minimize their toxicity, the active compounds are often closed in the liposome membranes. The objective of the work was preparation of bilayer liposomes from egg yolk phosphatidylcholine (EYPC), closing the complex VO(acac)2 in these membranes and estimating the concentration of vanadium complex after incorporation into liposomes membranes. Due to the paramagnetic properties of vanadium(IV) the concentration of this metal complex can be determined directly by EPR. Entering the spin label CTPO in the water phase into the studied arrangement allows for the indirect measurement of the concentration of complex, on the basis of changes of the EPR spectrum of the spin label caused by the presence of the vanadium(IV) complex. In the work the dependence of the α parameter based on the analysis of CTPO EPR spectra on the concentration of VO(acac)2 was determined. To demonstrate the presence of the complex in the membrane directly by measuring the EPR sulfate(IV) sodium was used in order to remove the EPR signal of vanadium(IV) from the water phase. The presence of vanadium(IV) in the membrane was also demonstrated indirectly using a spin label 12-SASL. Based on the results of EPR spectroscopy the concentration of the complex in the membrane was determined together with the partition coefficient of VO(acac)2 between the membrane and outer water environment of the membrane