Skip to content
Login Register

#critical micelle concentration

2 public questions tagged with this topic.

Lipid Link Protein

What happens when detergent concentration is below the CMC?

Understanding CMC highlights phase behavior of amphiphiles. At subsaturation detergent monomers exist dissolved in aqueous phase hydration shell disordered, partial insertion into outer leaflet may increase permeability but leaves bilayer structure largely intact. When monomer concentration reaches thermodynamic threshold where entropic cost of ordering water around hydrophobic tails outweighs micellization free energy, spontaneous aggregation into micelles occurs with hydrocarbon tails sequestered interior and polar heads facing water forming spherical or ellipsoidal particles thirty to fifty angstroms diameter. Below this point no micelles detected by dye solubilization, surface tension or NMR; membranes not disrupted into mixed micelles, so integral proteins remain embedded and organelle barriers persist demonstrated by retention of luminal markers. This intentional sub-CMC usage allows delivery of hydrophobic drugs or limited permeabilization. For complete lysis and purification supra-CMC concentrations mandatory providing sufficient micelles to sequester phospholipids and proteins into soluble particles preventing aggregation and inactivation during biochemical isolation. Experimental determination of CMC using light scattering fluorescent probes ANS or N-phenyl naphthylamine tracks abrupt intensity increase indicating micellization.

Ref: le Maire et al., Interaction of Membrane Proteins and Detergents, Biochim Biophys Acta 2000.

View Details
Lipid Link Protein

What is the critical micelle concentration (CMC)?

Amphipathic detergents in aqueous solution exhibit concentration-dependent self-assembly thermodynamically governed by hydrophobic effect. Monomers exist freely at low concentration with hydrophobic tails partially exposed to water energetically unfavorable. Upon reaching threshold called critical micelle concentration CMC, tail sequestration drives spontaneous formation of spherical or ellipsoidal aggregates called micelles where hydrophobic tails cluster inward forming oily core while hydrophilic heads face water outward, minimizing free energy. CMC is characteristic for each detergent influenced by tail length, head group, ionic strength, temperature and pH. Below CMC detergents exist mainly as monomers insufficient to solubilize membranes; above CMC monomer concentration remains roughly constant and additional detergent forms micelles capable of solubilizing lipids and membrane proteins. Measurements via surface tension, dye solubilization or fluorescence track CMC. It does not denote protein denaturation point, detergent inactivation pH or phosphorylation requirement, purely physical chemistry parameter defining aggregate formation essential for membrane biology and purification strategies. Such detailed mechanistic insight is frequently examined in competitive tests including NEET, CUET, CSIR-NET and GATE where transporter classification, energetics and disease linkage are integrated into problem-solving questions.

Ref: Garavito & Ferguson-Miller, J Biol Chem 2001, Detergent micellization; le Maire et al., 2000.

View Details