Binding of polyamines by the double-helical DNA molecule in unfolded and compact forms

The influence of the natural polyamines [spermine (Sp) and spermidine (Spd)] on the conformation of thymus DNA molecule (M = 4 and 15 MDa) was studied by means of the viscometric method over the range of low supporting electrolyte concentrations (CNaCl = 0.6 divided by 8.4 mM). In was shown that at sufficiently low degrees of ligand binding (theta PA) which satisfy the condition ZPA theta PA less than 0.76 (where ZPA is the valence of PA), the PA addition results in a slight decrease of the volume effects in the DNA molecule due to the increase of the ionic strength (mu) of solution conditioned by the presence of polyvalent PA cations and also to the supplanting of "bound" Na+ cations. The further increase in CPA induces the corresponding increase in theta PA up to the value which provides ZPA theta PA greater than 0.76, and is accompanied by drastic decrease of macromolecule's dimensions and partial DNA condensation as well. At larger degrees of binding (ZPA theta PA approximately 0.90) a transition from the expanded to compact form of the DNA molecule is observed. The calculations of theta 1 = theta Na + theta PA and rcr = theta 1 + ZPA theta PA as a function of mu were carried out according to Manning's two-variables theory on the basis of the obtained dependences of the critical PA concentrations (Ccr PA), which correspond to the midpoint of the condensational transition, versus CNaCl. The increase of rcr and/or decrease of the effective site dimensions (ZPA) was shown to be necessary for the DNA molecule collapse over the range of low mu less than 0.01. The binding constants of the PA association to the compact DNA form were evaluated by the simplest model of McGhee and von Hippel. On the basis of the results obtained for Spd it was hypothesized that the non-electrostatic interactions are significant by the binding of the PA to the compact form of the DNA molecule.     

The modifying effect of novocaine on the clinical manifestations of the intestinal form of radiation sickness]

On rats and dogs exposed to absolute lethal doses of X-irradiation (rats--10, 12 Gy; dogs--15 Gy sublethally) it has been shown that novocaini injection to animals immediately after radiation exposure reduces the primary radiation reaction and at the same time shifts the changes in morphofunctional state of peripheric blood on 24 hours, reduces the symptoms of acute radiation sickness, increases the average life length of the animals on 1,5 days. A conclusion concerning the expressed therapeutic influence of intraperitoneal novocaini injection immediately after radiation has been drawn.     

Conditioning of gray crows (Corvus cornix L.) in a "giant" eight-arm radial maze

Twelve adult hooded crows (Corvus cornix) were trained to perform a standard radial-maze task in a giant eight-arm outdoor radial maze constructed at the "Chistyi les" Biological Station (Tver oblast) for comparative investigations of spatial memory in birds and mammals. The maze consists of a central part of 250 cm diameter, and has arms of 650 cm length, 170 cm height and 80 cm width. The examined hooded crows showed good task performance. Errors (repeated visits to empty arms) were few in number and were predominantly connected with the tendency to avoid arms close to an observer.     

The effect of spermine on acid-base equilibrium in DNA molecule

The influence of spermine (Sp) on the acid-induced predenaturational and denaturational transitions in the DNA molecule structure has been studied by means of circular dichroism, spectrophotometric and viscometric titration at supporting electrolyte concentration 10 mM NaCl. The data available indicate that at [N]/[P] less than or equal to 0.60 (here [N] and [P] are molar concentrations of Sp nitrogen and DNA phosphours, respectively) the cooperative structural B----B(+)----S transitions are accompanied by the DNA double-helice winding. No competition for proton acceptor sites in the DNA molecule between H+ and Sp4+ cations has been observed when binding to neutral macromolecule. At 0.60 less than or equal to [N]/[P] less than or equal to 0.75 the displacement of the B----B(+)----S transitions midpoints to acidic pH region has been established. This is accompanied by DNA condensation and the appearance of differential scattering of circularly polarized light. The calculations carried out in the framework of the two-variable Manning theory have shown that the acid-induced reduction of the effective polyion charge density facilitates the Sp-induced DNA condensation. It has been shown that the acid-base equilibrium in the DNA molecule is determined by local [H+] in the 2-3 A hydrated monolayer of the macromolecule. An adequate estimation of [H+] can be obtained on the basis of the Poisson-Boltzman approach. The data obtained are consistent with recently proposed hypothesis of polyelectrolyte invariance of the acid-base equilibrium in the DNA molecule.     

Comparative analysis of inverted repeats of polypod fern (Polypodiales) plastomes reveals two hypervariable regions

Background

Ferns are large and underexplored group of vascular plants (~ 11 thousands species). The genomic data available by now include low coverage nuclear genomes sequences and partial sequences of mitochondrial genomes for six species and several plastid genomes.

Results

We characterized plastid genomes of three species of Dryopteris, which is one of the largest fern genera, using sequencing of chloroplast DNA enriched samples and performed comparative analysis with available plastomes of Polypodiales, the most species-rich group of ferns. We also sequenced the plastome of Adianthum hispidulum (Pteridaceae). Unexpectedly, we found high variability in the IR region, including duplication of rrn16 in D. blanfordii, complete loss of trnI-GAU in D. filix-mas, its pseudogenization due to the loss of an exon in D. blanfordii. Analysis of previously reported plastomes of Polypodiales demonstrated that Woodwardia unigemmata and Lepisorus clathratus have unusual insertions in the IR region. The sequence of these inserted regions has high similarity to several LSC fragments of ferns outside of Polypodiales and to spacer between tRNA-CGA and tRNA-TTT genes of mitochondrial genome of Asplenium nidus. We suggest that this reflects the ancient DNA transfer from mitochondrial to plastid genome occurred in a common ancestor of ferns. We determined the marked conservation of gene content and relative evolution rate of genes and intergenic spacers in the IRs of Polypodiales. Faster evolution of the four intergenic regions had been demonstrated (trnA- orf42, rrn16-rps12, rps7-psbA and ycf2-trnN).

Conclusions

IRs of Polypodiales plastomes are dynamic, driven by such events as gene loss, duplication and putative lateral transfer from mitochondria.

     

On the Correlation of S-S and C-S Raman Bands Frequencies and Intensities with Conformations of Disulfide Bridges in Proteins

Abstract

We have studied dependence of the S-S and C-S raman bands frequencies and intensities on the conformation of disulfide bridges. These correlations have been analyzed on the basis of the normal coordinates treatment in the valence force field and from comparison of the raman and X-ray data for the model compounds and proteins. The found regularity of the intensity variations with conformation make it possible to distinguish these spectral perturbations from those associated with the change in the number of disulfide bridges in proteins. Particularly, this was demonstrated on the γ-irradiated insulin solutions spectra. We also present some data appropriate for estimation of the content of disulfide bridges in proteins using internal intensity standards.     

The effect of a caudal hippocampus lesion on learning in a Morris water maze in Bank Voles (Clethrionomys glareolus)

The involvement of the caudal hippocampus in spatial learning is presently uncertain, compared to the well established role of the dorsal region. Therefore voles (Clethrionomys glareolus) with large (about 1/3 of the whole hippocampus) caudal cytotoxic lesions were tested in the Morris water maze. A version of the test intended to measure long term spatial memory was used. The lesion inhibited the learning process, as well as reducing the accuracy of platform location memory at early stages of training. The data obtained indicate the involvement of this area in control of spatial learning in rodents.     

On the correlation of S-S and C-S raman bands frequencies and intensities with conformations of disulfide bridges in proteins

We have studied dependence of the S-S and C-S raman bands frequencies and intensities on the conformation of disulfide bridges. These correlations have been analyzed on the basis of the normal coordinates treatment in the valence force field and from comparison of the raman and X-ray data for the model compounds and proteins. The found regularity of the intensity variations with conformation make it possible to distinguish these spectral perturbations from those associated with the change in the number of disulfide bridges in proteins. Particularly, this was demonstrated on the gamma-irradiated insulin solutions spectra. We also present some data appropriate for estimation of the content of disulfide bridges in proteins using internal intensity standards.