Use of mass spectrometry to measure aspartic acid racemization for ageing beluga whales
Bibliographic record
Abstract
Abstract We developed a novel analytical method to measure the D‐ and L‐isomers of aspartic acid (AA) in the eye lens of beluga whales (Delphinapterus leucas) for age determination. The method was based on hydrolysis of the eye lens under acidic conditions followed by direct injection onto a Chirobiotic T (25 cm × 4.6 ID, 5 μm particle size) high performance liquid chromatography analytical column and detection by tandem mass spectrometry operated in the negative ionization mode. The detection limit of the method was 550 pg for each isomer, the repeatability expressed as the relative standard deviation was 8% and the linear dynamic range was from 0.05 mM to 1 mM. The validated method was used to estimate, for the first time, the rate of racemization (Kasp) of the two AA isomers and also the ratio of D/L at age 0, (D/L)0, in 34 beluga whales from the Canadian Arctic. At a mean ocular lens temperature of 17.8°C, respective Kasp and (D/L)0 were 3.48 ± 1.47 × 10−3/yr and 0.010 ± 0.005. We evaluated factors that impact Kasp and affect uncertainty in age estimation and outline the steps required to incorporate the method in wildlife management decisions.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.000 | 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".