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Biomedical subjects

I A Sobolev

Publications and source records attributed to I A Sobolev.

10 recordsLinked to original sources
PubMed2006

[Processing of liquid radioactive waste by RADON Industrial Research Association].

The authors present experience accumulated by "RADON" Industrial Research Association in treating liquid radioactive waste. According to the presentation, activities of "R ADON" Industrial Research Association develop in three directions--evolving technical means to purify radioactive waters in "RADON" Industrial Research Association, advancing mobile plants to purify radioactive waters in other institutions, elaborating new technologies for liquid radioactive waste purifications within numerous national and international projects and agreements with various organizations (including those associated with nuclear power stations and nuclear submarines).

Humans↗
PubMed1998

Interdependence between DNA template secondary structure and priming efficiencies of short primers.

Here we analyze the effect of DNA folding on the performance of short primers and describe a simple technique for assessing hitherto uncertain values of thermodynamic parameters that determine the folding of single-stranded DNA into secondary structure. An 8mer with two degenerate positions is extended simultaneously at several complementary sites on a known template (M13mp18) using one, two or three (but never all four) of the possible dNTPs. The length of the extension is site specific because it is limited by the first occurrence in the downstream template sequence of a base whose complementary dNTP is not present. The relative priming efficiencies of different sites are then ranked by comparing their band brightnesses on a gel. The priming efficiency of a short primer (unlike conventional long primers) depends dramatically on the secondary structure of the template at and around the priming site. We calculated the secondary structure and its effect on priming using a simple model with relatively few parameters which were then optimized to achieve the best match between the predictions and the actual rankings of the sites in terms of priming efficiency. This work introduces an efficient and conceptually novel approach that in the future can make use of more data to optimize a larger set of DNA folding parameters in a more refined model. The model we used, however crude it may be, significantly improved the prediction of priming efficiencies of 8mer primers and appreciably raised the success rate of our DNA sequencing technique (from 67 to 91% with a significance of P < 7 x 10(-5)), which uses such primers.

Base Composition↗
PubMed1997

DNA sequencing using differential extension with nucleotide subsets (DENS).

Here we describe template directed enzymatic synthesis of unique primers, avoiding the chemical synthesis step in primer walking. We have termed this conceptually new technique DENS (differential extension with nucleotide subsets). DENS works by selectively extending a short primer, making it a long one at the intended site only. The procedure starts with a limited initial extension of the primer (at 20-30 degrees C) in the presence of only two out of the four possible dNTPs. The primer is extended by 6-9 bases or longer at the intended priming site, which is deliberately selected, (as is the two-dNTP set), to maximize the extension length. The subsequent termination reaction at 60-65 degrees C then accepts the extended primer at the intended site, but not at alternative sites, where the initial extension (if any) is generally much shorter. DENS allows the use of primers as long as 8mers (degenerate in two positions) which prime much more strongly than modular primers involving 5-7mers and which (unlike the latter) can be used with thermostable polymerases, thus allowing cycle-sequencing with dye-terminators compatible with Taq DNA polymerase, as well as making double-stranded DNA sequencing more robust.

DNA Primers↗
PubMed1995

On the mechanism of the modular primer effect.

Modular primers are strings of three contiguously annealed unligated oligonucleotides (modules) as short as 5- or 6-mers, selected from a presynthesized library. It was previously found that such strings can prime DNA sequencing reactions specifically, thus eliminating the need for the primer synthesis step in DNA sequencing by primer walking. It has remained largely a mystery why modular primers prime uniquely, while a single module, used alone in the same conditions, often shows alternative priming of comparable strength. In a puzzling way, the single module, even in a large excess over the template, no longer primes at the alternative sites, when modules with which it can form a contiguous string are also present. Here we describe experiments indicating that this phenomenon cannot be explained by cooperative annealing of the modules to the template. Instead, the mechanism seems to involve competition between different primers for the available polymerase. In this competition, the polymerase is preferentially engaged by longer primers, whether modular or conventional, at the expense of shorter primers, even though the latter can otherwise prime with similar or occasionally higher efficiency.

Base Sequence↗
PubMed1993

DNA sequencing: modular primers assembled from a library of hexamers or pentamers.

Here we report a striking effect displayed by "modular primers," which consist of hexamer or pentamer oligonucleotide modules base-stacked to each other upon annealing to a DNA template. Such a combination of modules is found to prime DNA sequencing reactions uniquely, unlike either of the modules alone. We attribute this effect in part to the increase in the affinity of an oligonucleotide for the template in the presence of an adjacent module. All possible pentamer (or hexamer) sequences total 1024 (or 4096) samples, a manageable size for a presynthesized library. This approach can replace the synthesis of primers, which is the current bottleneck in time and cost of the primer walking sequencing, and can allow full automation of the closed cycle of walking.

Base Sequence↗
PubMed1983

[Automated system for collecting, processing and storing individual dosimetric control data].

Organization of a automated system of individual dosimetric control on the basis of mini-computer M-6000 was described. The hard ware system was considered, a coding principle for initial information was proposed. A block diagram of the soft ware consisting of a set of six interrelated programs was presented. Each one was considered in detail. As a result of this system a data bank is being set up for 10000 persons under central individual dosimetric control. The introduction of the automated system made it possible to do away with manual processing, to improve the reliability of processing, to classify registration forms, to control the time course of individual exposures, to detect the most hazardous from the radiation point of view departments and places of work, occupations, and to issue recommendations to improve technological processes to make radiation situation better. The automated system of individual dosimetric control can be recommended for factories and institutions where centralized individual dosimetric control is needed for a numerous staff.

Computers↗