depurination

Purine release boundary

DNA depurination cleaves the purine-deoxyribose glycosidic bond without requiring initial phosphodiester backbone disruption. [Depurination decreases fidelity of DNA synthesis in vitro](https://www.nature.com/articles/270537a0)

1. Which purine-sugar bond was cleaved, and how was the departing base identified? definition
2. What evidence distinguishes this event from depyrimidination, base modification or direct backbone cleavage? boundary

Purine-bearing substrate

Record sugar type, base identity, molecular context and any prior base modification; do not transfer observations between substrate classes without justification.

1. Is the substrate DNA, RNA, a free nucleoside or nucleotide, or another specified purine-bearing molecule? definition
2. Which residue coordinates, sequence context and pre-existing purine modifications are established rather than inferred? provenance

Catalysis evidence

Record whether purine removal is attributed to background hydrolysis, chemical promotion or a specified catalyst, with controls supporting that attribution.

1. What observations support the assigned reaction route beyond merely detecting an abasic product? provenance
2. Which catalyst-free, untreated or otherwise matched controls distinguish the proposed cause from background purine loss? measurement

Condition-specific rate

Treat a reported rate as conditional on substrate, environment, sampling interval and fitted kinetic model; retain the underlying time-course evidence.

1. What pH, temperature, buffer composition and exposure durations applied before and during measurement? measurement
2. What time-course data and normalization justify the reported rate or half-life? measurement
3. Within which tested conditions may this rate be used to predict further purine loss? boundary

Base loss versus chain breakage

Depurination and subsequent cleavage at apurinic sites require separate observations; defined oligonucleotide experiments have characterized these successive transformations. [Mechanistic studies on depurination and apurinic site chain breakage](https://pubmed.ncbi.nlm.nih.gov/7800492/)

1. Which released purines and residual apurinic products were measured at each sampling time? measurement
2. Was backbone cleavage already present, produced during analysis, or observed after the initial purine-loss interval? boundary

Depurination attribution

Record whether an assay detects released purines, abasic residues or strand breaks, and identify alternative processes and handling artifacts that could generate the signal.

1. What analyte does the assay measure, with what calibration, detection limit and uncertainty? measurement
2. How are pyrimidine-derived abasic sites, pre-existing free purines and sample-preparation damage excluded or quantified? boundary
3. Which independent measurement would resolve the remaining ambiguity about purine loss? action

Application-specific damage assessment

Keep measured purine loss, remaining lesion burden, backbone integrity and performance in the intended application as distinct assessments.

1. What purine-loss burden, site distribution and backbone state are established for this material? measurement
2. Which application-specific evidence or acceptance criterion determines whether the material remains usable? action

Response selection

Link handling changes to evidence about further depurination and hand off lesion processing to the appropriate repair or recovery model.

1. Which tested change in exposure, storage or processing reduces additional purine loss for this substrate? action
2. What evidence supports preservation, repair, remeasurement or rejection of the affected material? action
3. Which proposed outcomes require a separate repair, replication or biological-effect model? boundary

Check these first

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these check these first hold for the sense of depurination this model covers, and on what evidence? provenance

Kinds and varieties

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these kinds and varieties hold for the sense of depurination this model covers, and on what evidence? provenance

Real-world use

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these real-world use hold for the sense of depurination this model covers, and on what evidence? provenance

Typical measurements

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these typical measurements hold for the sense of depurination this model covers, and on what evidence? provenance

Failure modes and hazards

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these failure modes and hazards hold for the sense of depurination this model covers, and on what evidence? provenance

Neighbouring kinds and how to tell them apart

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these neighbouring kinds and how to tell them apart hold for the sense of depurination this model covers, and on what evidence? provenance