ABSTRACT
We study nonlinear dynamics of the DNA molecule relying on a helicoidal Peyrard-Bishop model. We look for traveling wave solutions and show that a continuum approximation brings about kink solitons moving along the chain. This statement is supported by the numerical solution of a relevant dynamical equation of motion. Finally, we argue that an existence of both kinks and localized modulated solitons (breathers) could be a useful tool to describe DNA-RNA transcription.
Subject(s)
DNA/metabolism , Nonlinear Dynamics , Nucleic Acid Conformation , Hydrogen Bonding , Protein Structure, Secondary , Transcription, Genetic/geneticsABSTRACT
Nonlinear dynamics of DNA molecule at segments where DNA-RNA transcription occurs is studied. Our basic idea is that the solitary wave, moving along the chain, transforms into a demodulated one at these segments. The second idea is that the wave becomes a standing one due to interaction with DNA surrounding, e.g., RNA polymerase molecules. We explain why this is biologically convenient and show that our results match the experimental ones. In addition, we suggest how to experimentally determine crucial constant describing covalent bonds within DNA.
Subject(s)
DNA/metabolism , Models, Biological , Nonlinear Dynamics , RNA/biosynthesis , Transcription, Genetic/physiologyABSTRACT
The objective of the Third International Intercomparison on EPR Tooth Dosimetry was to evaluate laboratories performing tooth enamel dosimetry <300 mGy. Final analysis of results included a correlation analysis between features of laboratory dose reconstruction protocols and dosimetry performance. Applicability of electron paramagnetic resonance (EPR) tooth dosimetry at low dose was shown at two applied dose levels of 79 and 176 mGy. Most (9 of 12) laboratories reported the dose to be within 50 mGy of the delivered dose of 79 mGy, and 10 of 12 laboratories reported the dose to be within 100 mGy of the delivered dose of 176 mGy. At the high-dose tested (704 mGy) agreement within 25% of the delivered dose was found in 10 laboratories. Features of EPR dose reconstruction protocols that affect dosimetry performance were found to be magnetic field modulation amplitude in EPR spectrum recording, EPR signal model in spectrum deconvolution and duration of latency period for tooth enamel samples after preparation.
Subject(s)
Electron Spin Resonance Spectroscopy/methods , Forensic Dentistry/methods , Radioisotopes/analysis , Radiometry/methods , Tooth/chemistry , Electron Spin Resonance Spectroscopy/trends , Forensic Dentistry/trends , Humans , Radiometry/trends , Reference Values , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
The objective of the 3rd International Intercomparison on Electron Paramagnetic Resonance (EPR) Tooth Dosimetry was the evaluation of laboratories performing tooth enamel dosimetry below 300 mGy. Participants had to reconstruct the absorbed dose in tooth enamel from 11 molars, which were cut into two halves. One half of each tooth was irradiated in a 60Co beam to doses in the ranges of 30-100 mGy (5 samples), 100-300 mGy (5 samples), and 300-900 mGy (1 sample). Fourteen international laboratories participated in this intercomparison programme. A first analysis of the results and an overview of the essential features of methods applied in different laboratories are presented. The relative standard deviation of results of all methods was better than 27% for applied doses in the range of 79-704 mGy. In the analysis of the unirradiated tooth halves 8% of the samples were identified as outliers with additional absorbed dose above background dose.
Subject(s)
Electron Spin Resonance Spectroscopy/methods , Electron Spin Resonance Spectroscopy/standards , Radiometry/methods , Radiometry/standards , Reference Standards , Tooth/chemistry , Tooth/radiation effects , Benchmarking/methods , Body Burden , Humans , In Vitro Techniques , Internationality , Quality Assurance, Health Care/methods , Quality Assurance, Health Care/standards , Radiation Dosage , Relative Biological Effectiveness , Reproducibility of Results , Retrospective Studies , Risk Assessment/methods , Risk Assessment/standards , Sensitivity and SpecificityABSTRACT
The International Atomic Energy Agency has established a dose quality audit service for radiation processing facilities. The objective of the service is to provide an independent check on the routine dosimetry system in use at the facility. The audit service is based on the use of alanine EPR dosimetry. Generally, alanine dosimeters are irradiated at the facility together with a product, and the response is then analyzed at the IAEA laboratory. Practice of the audit service has shown that the main uncertainty in alanine dosimetry is due to absence of temperature control at the irradiation facilities. Here, a method for stabilizing the temperature of the dosimeter during irradiation is proposed.
