Hi,
I know that low molecular weight (MW) molecules generally tend to have higher mobility, while high molecular weight molecules tend to have lower mobility.
However, in my experimental results, high molecular weight complexes showed faster mobility.
Why is that?
(Same concentration, same environmental conditions)
Can you explain this observation?
To help you understand, we present experimental information.
● MicroScale Thermophoresis (MST) was used in the experiment.
● Subject: Dye-labeled DNA.
● Ligand: Protein.
● Purpose: To determine the binding affinity between DNA and protein.
● Principle of MST: Observing the degree of fluorescence reduction after irradiating the dye-DNA(or DNA-protein complex) with a laser. (Mobility changes due to MW changes)
If there is no binding, the complex will not form, so the mobility should increase.
Successful binding should result in a complex formation, so the mobility should decrease.
Reference of figure: M. Jerabek-Willemsen et al. / Journal of Molecular Structure 1077 (2014) 101–113
Microscale thermophoresis (MST) is used for to analyze molecular interactions, such as protein-protein and protein-ligand interactions. The thermally-induced mobility of any given macromolecule or complex depends on multiple factors, not just molecular weight. These include the surrounding hydration shell and charge. Considering that, it seems reasonable that the binding of the protein to the DNA could increase the mobility rather than decrease it.
Dear all, it depends on the medium. In GPC/SEC larger molecules exit first, smaller ones are retained by the stationary phase. In electrophoresis, charged molecules are more mobile compared to neutral ones. More specifc details are needed to focus the situation under study. My Regards
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