I am looking for a relatively high throughput method of detecting the CMC of detergent or protein micelles. Does any one know of another high throughput method besides fluorescence or other chemical probes besides pyrene fluorescence?
The best and also easy way it to use NMR. You need to make some standard detergent samples to compare with your protein/detergent sample. It's a very precise method and takes not more than 5 min/ sample. It can be applied to all detergents on the market independent on their head groups.
Indeed, NMR can help. It is diffusion-ordered NMR spectroscopy (DOSY) or simply self-diffusion measurements. If CMC of your detergent (protein) is not too low, you can measure DOSY spectra in the concentration range, encompassing the CMC-value. The latter can be determined precisely. One of the papers on this subject:
http://www.ncbi.nlm.nih.gov/pubmed/20192181 (pdf of this article is attached). In fact, if you need to determine CMC reliably, the use of several methods (including, e.g. UV-spectroscopy) is desirable.
When studying proteins:detergent mixed micelles you will have to determine the CMC by comparing the diffusion coefficient of the free detergent, protein:detergent micelles and protein-free micelles. These can be achieved by considering specific areas of the 1D 1H spectra in the DOSY experiments and using some additives. These references may help you:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2893019/
http://www.ncbi.nlm.nih.gov/pubmed/22335573
We have used DOSY before for this purpose before to characterize protein micelles (our main focus).
https://www.researchgate.net/publication/51894755_NMR_characterization_of_monomeric_and_oligomeric_conformations_of_human_calcitonin_and_its_interaction_with_EGCG?ev=prf_pub
https://www.researchgate.net/publication/232764089_Side_Chain_Dynamics_Reveals_Transient_Association_of_A(1-40)_Monomers_with_Amyloid_Fibers?ev=prf_pub
https://www.researchgate.net/publication/24392603_Association_of_highly_compact_type_II_diabetes_related_islet_amyloid_polypeptide_intermediate_species_at_physiological_temperature_revealed_by_diffusion_NMR_spectroscopy?ev=prf_pub
I can say the method is pretty rugged and works well, giving the hydrodynamic radius with much higher precision than DLS. However, NMR is not high throughput like fluorescence and it is very difficult to get CMC values in the low micromolar range.
The Coomassie method worked really well for us with SDS but we did not have enough protein to check it with the protein. I am concerned that Coomassie may bind the monomeric form of the proteien.
Article NMR Characterization of Monomeric and Oligomeric Conformatio...
Article Side-Chain Dynamics Reveals Transient Association of Aβ 1–40...
Article Association of Highly Compact Type II Diabetes Related Islet...
Have you considered the very basic approach from surface and colloid chemistry where you simply measure the surface tension of your liquid as a function of concentration of your sample? This might not be a truly high throughput approach, but it is a rather simple approach and you work without labels which might influence your micelle structure. See the link below for a few examples, but there should be a vast amount of literature available of measuring CMC by this approach.
http://www.sciencedirect.com/science/article/pii/S0927776505002389#
http://www.sciencedirect.com/science/article/pii/S1570963907002841#
Although standard surface tension equipment normally needs quite a large sample volume, there are a few solutions where you can measure surface tension of samples with a volume of ca. 10-100 microliter (e.g. pendant drop method or rod method).
You can also consider Light Scattering Technique... Unimers scatter less while micelles scatter more....So the Scatttered light intensity vs concentration plot can give the CMC ....
Hi all dear
The given answers are interesting. I think you can do conductivity or Uv-Vis spectroscopy as a simple methods for CMC determination.
If you have access to x-rays, x-ray scattering can be high-throughput (96-well) and will readily detect micelles plus define their radius, mass, and maximum dimension (see Nature Methods 6:606-12).
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