Deletion of the Helical Motif in the Intestinal Fatty Acid-Binding Protein Reduces Its Interactions with Membrane Monolayers: Brewster Angle Microscopy, IR Reflection-Absorption Spectroscopy, and Surface Pressure Studies
Bibliographic record
Abstract
Intestinal fatty acid binding protein (IFABP) appears to interact directly with membranes during fatty acid transfer [Hsu, K. T., and Storch, J. (1996) J. Biol. Chem. 271, 13317-13323]. The largely alpha-helical "portal" domain of IFABP was critical for these protein--membrane interactions. In the present studies, the binding of IFABP and a helixless variant of IFABP (IFABP-HL) to acidic monolayers of 1,2-dimyristoylphosphatidic acid (DMPA) has been monitored by surface pressure measurements, Brewster angle microscopy (BAM), and infrared reflection-absorption spectroscopy (IRRAS). Protein adsorption to DMPA exhibited a two phase kinetic process consisting of an initial slow phase, arising from protein binding to the monolayer and/or direct interfacial adsorption, and a more rapid phase that parallels formation of lipid-containing domains. IFABP exhibited more rapid changes in both phases than IFABP-HL. The second phase was absent when IFABP interacted with zwitterionic monolayers of 1,2-dipalmitoylphosphatidylcholine, revealing the important role of electrostatics at this stage. BAM images of DMPA monolayers with either protein revealed the formation of domains leading eventually to rigid films. Domains of DMPA/IFABP-HL formed more slowly and were less rigid than with the wild-type protein. Overall, the IRRAS studies revealed a protein-induced conformational ordering of the lipid acyl chains with a substantially stronger ordering effect induced by IFABP. The physical measurements thus suggested differing degrees of direct interaction between the proteins and DMPA monolayers with the IFABP/DMPA interaction being somewhat stronger. These data provide a molecular structure rationale for previous kinetic measurements indicating that the helical domain is essential for a collision-based mechanism of fatty acid transfer to phospholipid membranes [Corsico, B., Cistola, D. P., Frieden, C. and Storch, J. (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 12174-12178].
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".