Single-Strand-Specific Radiosensitization of DNA by Bromodeoxyuridine
Bibliographic record
Abstract
The effects of bromodeoxyuridine (BrdUrd) substitution for thymidine on gamma-ray-induced strand breakage were determined in single- and double-stranded oligonucleotides and double-stranded oligonucleotides containing a mismatched bubble region. BrdUrd does not sensitize complementary double-stranded DNA to gamma-ray-induced strand breakage, but it greatly sensitizes single-stranded DNA. However, when the BrdUrd is present in a single-stranded bubble of a double-stranded oligonucleotide, the non-base-paired nucleotides adjacent to the BrdUrd as well as several unpaired sites on the opposite unsubstituted strand are strongly sensitized. The radiosensitization properties of BrdUrd result primarily from the electrophilic nature of the bromine, making it a good leaving group and leading to the irreversible formation of the uridine-yl radical (dUrd(.)) or the uridine-yl anion (dUrd(-)) upon addition of an electron. The radiolytic loss of the bromine atom is greatly suppressed in double-stranded compared to single-stranded DNA. Thus we propose that the radiosensitization effects of bromouracil in vivo will likely be limited to single-strand regions such as found in transcription bubbles, replication forks, DNA bulges and the loop region of telomeres. Our results may have profound implications for the clinical use of bromodeoxyuridine (BrdUrd) as a radiosensitizer as well as for the development of targeted radiosensitizers.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".