The plutonium isotopes and strontium-90 determination in hot particles by characteristic X-rays.

This paper reports the developed non-destructive methods for the plutonium isotopes and strontium-90 content determination in hot particles and other samples. The proposed methods are based on the measurement of the characteristic X-rays accompanying the decay of these radionuclides. For hot particles of NPP accident origin, the proposed method's error limits are 10-15% for hot particles (samples) with activity above 100 Bq and 15-20% for hot particles (samples) with activity less than 100 Bq. For explosive particles, the determination accuracy is 10-15% for activity more than 5 Bq and 20-30% for 0.1-5 Bq activity. The accuracy of the proposed method for determining 90Sr in samples with its specific content of more than 104 Bq/sample is 5%, with ~102 Bq/sample its content is 15-20%. The cost of one sample measurement and the processing time of these methods are significantly reduced compared to traditional studies. The proposed methods are reasonably simple measurement methods and can be carried out even in the field condition. They open up new possibilities for the quick search and study of hot particles and environmental samples.

Speciation of actinides in groundwater samples collected near deep nuclear waste repositories.

Actinide binding to colloidal particles of different nature was studied under oxic and anoxic conditions of an underground nuclear waste disposal site using successive micro- and ultrafiltration techniques. According to the actinide redox speciation, under oxic conditions they were present in high oxidation states except for plutonium, for which a significant part was found in the tetravalent state. In case of the anoxic conditions, the share of An (IV) was proportional to the total U(IV) concentration. This indicated formation of intrinsic U(IV) hydroxocolloids, which bound other actinides. Formation of the intrinsic actinide colloids was proven by the secondary ion mass spectrometry (SIMS) with the submicron resolution. In contrast, under the oxic conditions uranium and plutonium were sorbed by natural colloids (amorphous hydrous ferric oxide and Mn oxides).

[Molecular evolution: creation of nucleic acids capable of specific complex formation and possessing catalytic functions]. / Molekuliarnaia évoliutsiia: sozdanie nukleinovykh kislot, sposobnykh k spetsificheskomu kompleksoobrazovaniiu i obladaiushchikh kataliticheskimi funktsiiami.

Method of designing nucleic acids capable of specific complex formation with arbitrary ligands (aptamers) and catalytically competent nucleic acids are described. The methods rely on generation of libraries of random nucleotide sequences, selection of molecules possessing the desired property from these libraries, and amplification of the selected molecules. Repeating of the selection and amplification procedures results in evolutional improvement of the molecule ability to accomplish the function under consideration. This molecular evolution approach opens up broad possibilities for investigation of mechanisms of molecular recognition of small ligands and biopolymers by nucleic acids and mechanisms of reactions catalyzed by ribozymes. Design of novel ribozymes and nucleic acids capable of specific binding to certain biopolymers may become an efficient approach for development of practically important compounds, biologically active compounds and affinity sorbents.

[Effect of transcription inhibitors on RNA synthesis in the polytene chromosomes of Drosophila melanogaster]. / Vliianie ingibitirov transkriptsii na sintez RNK v politennykh khromosomakh Drosophila melanogaster.

The inhibition of RNA synthesis by DRB (5,6-dichloro-1-beta-D-ribofuranosyl benzimidazole) differs in different regions of D. melanogaster polytene chromosomes. In the majority of regions RNA synthesis is greatly inhibited, but in certain regions, including different development stage-specific puffs, it is still on. A case of transcription initiation in the heat shock puffs was also found. alpha-Amanitin considerably reduced RNA transcription in the majority of nuclei but some part of the nuclei are not affected at all. A combined action of alpha-amanitin and DRB exerts a considerably higher inhibitory effect.

[Combined effect of heat shock and ecdysone on the transcription of Drosophila melanogaster polytene chromosomes]. / Kombinirovannoe deistvie teplovogo shoka i ékdizona na transkriptsiipolitennykh khromosom Drosophila melanogaster.

The combined action of ecdysone and temperature elevation (heat shock) on D. melanogaster polytene chromosome transcription has been investigated. It was shown that heat shock while blocking the transcription in ecdysone--induced puffs is not effective in decreasing their size. Thus we are able to observe chromatin decondensation without transcription. The indirect immunofluorescence using an antiserum directed against DNA/RNA hybrids revealed an intense fluorescence in the polytene chromosomes of heat shocked larvae both in the actively transcribed heat shock puffs and in ecdysone stimulated "primary puffs" with blocked transcription. Ecdysone introduced into the media during heat shock is unable to induce any puffs. On the other hand the hormone introduced into the media after temperature elevation (30' of heat shock + 1 hour of ecdysone stimulation) induces some of the "primary puffs". A new approach for cloning the genes inducible by ecdysone and other inducible loci as well has been developed using the data obtained.

[Quantitative analysis of the DNA content in salivary gland chromosomes of Chrironomus thummi in the larval and prepupal stages]. / Kolichestvennyi analiz soderzhaniia DNK v khromosomakh sliunnykh zhelez Chironomus thummi na stadiiakh lichinki i predkukolki

Relative DNA content during the polytenization of the salivary gland nuclei of Chironomus thummi was measured by cytophotometric and cytofluorometric methods. To estimate polyteny degree, DNA content was calculated in hemocyte and spermatocyte nuclei. Chromosome polytenization is associated with the 10th-12th replication rounds. There are 4-5 replication rounds in the 1st instar, 2-3 rounds in the 2nd instar, the 3rd and the 4th instars have 1-2 rounds each. From early postembryonic development, larvae already have salivary gland nuclei representing two polyteny classes (2-2-2-4c), this heterogeneity being retained in all instars. Approximate DNA content is 0.51-0.58 picogram per a diploid set.

Quantitative analysis of DNA content in the salivary gland chromosomes of Chironomus thummi at larval and prepupal stages.

Relative DNA content during the polytenization of the salivary gland nuclei of Chironomus thummi was measured by cytophotometric and cytofluorometric methods. To estimate the degree of polyteny, the DNA content was calculated in hemocyte and spermatocyte nuclei. Chromosome polytenization is associated with 10 to 12 replication rounds. There are 4-5 replication rounds in 1st instar, 2-3 rounds in 2nd instar; 3rd and 4th instars have 1-2 rounds each. From early postembryonic development, larvae already have salivary gland nuclei representing two polyteny classes (2-3 - 2-4C); A similar heterogeneity is retained in all instars. The approximate DNA content is 0.51-0.58 picogram per diploid set.