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Label-Free Optical Method for Quantifying Molecular Transport Across Cellular Membranes In Vitro
Mohammad Sharifian Gh1, Michael J Wilhelm1, Hai-Lung Dai1
1Department of Chemistry, Temple University , 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.
The Journal of Physical Chemistry Letters
|August 13, 2016
Summary
This study introduces a label-free nonlinear optical method to quantify membrane transport rates. The technique uses a reference molecule to indirectly measure the transport of target molecules, enabling broader applications in cell biology.
Area of Science:
- Biophysics
- Cell Biology
- Optical Methods
Background:
- Label-free quantification of membrane transport is crucial for understanding cellular processes.
- Second-harmonic generation (SHG) laser scattering offers surface-specific membrane transport characterization.
- Most biologically relevant molecules lack SHG activity, limiting current SHG-based transport studies.
Discussion:
- This research extends SHG-based membrane transport analysis to SHG-inactive molecules.
- The method involves monitoring an SHG-active reference molecule's transport in the presence of an SHG-inactive target molecule.
- The transport rate of the SHG-inactive target is deduced from perturbations in the reference molecule's transport rate.
Key Insights:
- A novel competitive transport assay is developed using SHG-active and SHG-inactive molecules.
- The method successfully quantifies the transport rate of propidium (Pro), an SHG-inactive dication, using malachite green (MG) as a reference.
- Validation was achieved by comparing extracted and directly measured Pro transport rates across bacterial outer-membrane protein channels.
Outlook:
- This technique significantly broadens the scope of SHG-based membrane transport studies.
- It offers a versatile platform for label-free quantification of diverse small/medium-sized molecules in living cells.
- Future applications may include drug delivery studies and understanding transporter kinetics.
