P3‐076: Time‐Resolved Hydrogen Deuterium Exchange Mass Spectrometry Provides a Detailed Picture of the Conformational Bias Shift that Drives TAU Pathogenesis
Bibliographic record
Abstract
The conventional tools of structural biology are largely ineffective at defining the 'structural biases' that drive function and pathogenesis in intrinsically disordered proteins (IDPs). In the case of Alzheimer's, this has left a substantial gap in our understanding of the earliest events in Tau and Aβ pathogenesis. We have developed a novel approach called Time-Resolved ElectroSpray Ionization mass spectrometry with Hydrogen Deuterium eXchange (TRESI-HDX), that provides a detailed picture of the conformational biases that underlie aggregation in IDPs. In the current study, we use TRESI-HDX to define the conformational bias shifts that accompany GSK3β-mediated hyperphosphorylation and subsequent fibrillization of Tau. Full-length Tau protein (hTau40) was produced from E. coli and purified using heating and cation exchange. Hyperphosphorylation was achieved by 30hr incubation of tau with GSK3β / ATP. 'Native' (unphosphorylated) and 'hyperphosphorylated' tau were then subjected to analysis by TRESI-HDX, which is implemented on a microfluidic chip. Protein was mixed 1:3 with D2O for labeling times between 50 ms and 2000 ms, followed immediately by exchange quenching (pH 2.4) and digestion using pepsin. Deuterium uptake on each peptide was analyzed using in-house software. Globally, native Tau adopts a globular 'paperclip-like' fold with significant protection from exchange at the N and C termini. Both hexapaptide motifs are in low-exchanging regions indicating that they are generally sequestered from solvent in the native ensemble. Upon hyperphosphorylation, Tau adopts an 'extended' configuration with generally higher uptake, particularly at the N and C termini. Hexapeptide II becomes much more exposed upon hyperphosphorylation, while hexapeptide I remains buried. There is also a new nucleus of structure in the microtubule-binding region. These conformational bias changes were visualized using TRESI-HDX papramaterized computer modeling based on the low computational complexity FRODAN algorithm.
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.010 | 0.003 |
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".