Experimental Measurement Methods for Engineered Membranes
Bibliographic record
Abstract
Introduction In previous chapters we described how to construct engineered membranes and devices including the ion-channel switch biosensor, electroporation measurement platform, and electrophysiological response platform. An important question is: How can one verify that the artificial membranes constructed in previous chapters have the precisely engineered structure that we have claimed? This chapter focuses on how experimental measurements can be performed on engineered membranes to estimate important biological parameters such as the membrane conductance and capacitance, and also how such measurements can be used to verify the structure of the membrane. We describe three important measurement methods to determine the properties of engineered membranes: (i) impedance measurements, (ii) time-dependent electrical measurements, and (iii) spectroscopy and imaging techniques. Impedance measurement and time-dependent electrical measurement techniques require minimal experimental setup and low-cost laboratory equipment compared with optical and imaging techniques. For example, a standard computer sound card can be used to perform impedance measurements; in comparison, spectroscopic and imaging techniques require both labor-intensive experimental setup and access to equipment that can perform fluorescence correlation spectroscopy, X-ray and neutron reflectometry, and electron microscopy. In practice this is why either impedance measurements or time-dependent electrical measurements are used for estimating properties of engineered membranes. The measurement methods in this chapter also play an important role in Part III, where we construct dynamic models of engineered membranes which can be used to relate the experimental measurements from tethered membranes to biological parameters of interest (e.g., reaction pathway of pore-forming peptides, the concentration estimation of analyte species, and the population and dynamics of aqueous pores in the membrane). Electrical Response of Engineered Membranes A very useful yet straightforward procedure for performing measurements of an engineered membrane is to apply an excitation potential across the membrane and then record the current response. Indeed, in Part III, we construct mathematical models for the electrical response of engineered membranes at several levels of abstraction (from atoms to device). When the engineered tethered membrane is excited by a low-level (below 50 mV) external alternating voltage, the ions in the electrolyte solution migrate to and from the gold electrode surface and insulating barrier of the membrane. Additionally, ions can also pass through aqueous pores and ion channels in the membrane.
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.004 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.004 |
| Insufficient payload (model declined to judge) | 0.024 | 0.015 |
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".