Methods & Assays

I built a microfluidic platform to quantify copper transport across lipid membranes mediated by purified proteins. By combining controlled gradients with fluorescence-based detection, this assay provides sensitive, high-resolution measurements of metal flux, offering a powerful tool for studying metal-binding proteins and membrane transporters.

I developed a 23Na-NMR method that uses an impermeable lanthanide-based shifting agent to cleanly separate intracellular and extracellular sodium signals in living cells. By splitting the 23Na resonance into two distinct peaks, the assay allows direct, real-time measurement of Na⁺ transport, leakage, and antiporter activity without disrupting the physiological environment of the cell.

The motivation behind this method was a long-standing question in complex I research: do its membrane subunits pump protons only, or do they retain the ability to pump sodium, as their evolutionary relationship to ancient Na⁺/H⁺ antiporters suggests? Traditional biochemical assays could not resolve intracellular sodium accurately enough to answer this.

With the NMR approach, we could monitor sodium movement inside intact cells with unprecedented clarity. This allowed us to test the ion-coupling properties of engineered strains and dissect how different membrane subunits contribute to ion transport. The method provided direct functional evidence supporting the evolutionary connection between complex I subunits and Na⁺/H⁺ antiporters, helping clarify how modern respiratory machinery inherited and adapted its ancestral ion-pumping mechanisms.