# Energetics of Channel-Bilayer Interactions

> **NIH NIH R01** · WEILL MEDICAL COLL OF CORNELL UNIV · 2021 · $522,867

## Abstract

Membrane protein function is regulated by changes in the host membrane's lipid composition by mechanisms
that range from specific (chemical) interactions between proteins and individual lipid molecules, to non-specific
(physical) interactions between proteins and the bilayer. The proposed studies focus on the physical regulation
of membrane protein function, and explores how biologically active molecules (including drugs and drug
candidates) alter lipid bilayer properties, as sensed by bilayer-spanning channels. This bilayer regulation of
protein function occurs because hydrophobic interactions between membrane proteins and their host bilayer,
couple a protein's conformational preference to the bilayer physical properties. This means that membrane
protein conformational transitions (between states I and II) that involve the protein/bilayer boundary will have
I→II
an associated energetic cost, which becomes the bilayer contribution ( ΔGbilayer ) to the free energy difference for
the conformational change.
The rationale for the proposed studies is that drug-induced changes in lipid bilayer properties alter membrane
 I→II I→II
protein function through the ensuing changes in ΔGbilayer ). Drug-induced changes in ΔGbilayer will be determined
for a well-defined conformational transition, the gramicidin (gA) monomer↔dimer equilibrium, using both
stopped-flow fluorescence quench experiments to screen libraries of compounds and single-channel
experiments to dissect how selected compounds alter bilayer properties. These results will be combined with
results of cytotoxicity studies on selected cell lines, to understand how the changes in membrane protein
function that arise from drug-induced changes in lipid bilayer properties may alter cell function. Our results to
I→II
date show that more 90% of molecules that alter ΔGbilayer (for the gA monomer↔dimer equilibrium) by more
than kBT (where kB is Boltzmann's constant and T is temperature in kelvin) are cytotoxic at the tested
I→II
concentration, and that all molecules that alter ΔGbilayer by more than 2 kBT are cytotoxic. For comparison, less
than 20% of compounds with minimal bilayer-modifying effect are cytotoxic. This provides mechanistic insight
into drug toxicity (though a drug may be toxic for any number of reasons not related to changes in bilayer
properties). The proposed studies will use select groups of drugs to elucidate the molecular basis for the
altered bilayer properties using symmetric and asymmetric bilayers. We will extend these studies in larger-
scale studies on chemical libraries and explore the relationship between molecular structure, bilayer-modifying
potency and cytotoxicity. The biological implications of this mechanism will be explored in studies on “real” ion
channels (Kv and Nav channels in whole-cell electrophysiological studies and KcsA reconstituted in bilayers of
defined composition). We also will pursue the larger scale implications for cell and organism function in toxicity
...

## Key facts

- **NIH application ID:** 10173791
- **Project number:** 5R01GM021342-45
- **Recipient organization:** WEILL MEDICAL COLL OF CORNELL UNIV
- **Principal Investigator:** OLAF S. ANDERSEN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $522,867
- **Award type:** 5
- **Project period:** 1977-06-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10173791

## Citation

> US National Institutes of Health, RePORTER application 10173791, Energetics of Channel-Bilayer Interactions (5R01GM021342-45). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/10173791. Licensed CC0.

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