Phase Separation of Nonionic Detergents by Salt Addition and Its Application to Membrane Proteins

Phase Separation in the Isolation and Purification of Membrane Proteins

“…The detergent-rich phase becomes solid at (NH 4 ) 2 SO 4 concentrations >20%, probably forming a liquid crystalline phase as discussed previously. NP-40 behaves similarly but needs slightly lower salt concentrations for phase separation at room temperature (9). …”

“…Thus, the cloud point of a micelle solution can be reached by adding salt instead of changing the temperature. This has been extensively studied for detergents of the Triton family (9). Other additives like glycerol or urea strongly affect the phase behavior of a detergent, as does the presence of lipids in mixed micelles (10) and the addition of polymers (see next section).…”

“…Adding >9% of (NH 4 ) 2 SO 4 or >16% NaCl reduces the cloud point of 2% Triton X-100 to room temperature (9), which can be exploited for the fractionation of membrane proteins (26). The detergent-rich phase becomes solid at (NH 4 ) 2 SO 4 concentrations >20%, probably forming a liquid crystalline phase as discussed previously.…”

Membrane proteins and proteomics: Un amour impossible?

“…Increasing ionic strengths induce ªsalting outº of the detergent and thus lowering the transition temperature. This critical temperature for Triton X-100 goes from 60 o C in water to 20 o C in 3 M NaCl [18]. This would be of little importance if the behavior of the proteins did not also strongly depend on the ionic strength.…”

Quantitative Determination of Zwitterionic Detergents Using Salt-Induced Phase Separation of Triton X-100

“…This phase separation could be induced only when salt was added (salt-induced phase separation). A comparable behavior of nonionic detergents has previously been described for members of the Triton, Brij, and Tween series (3)(4)(5). As far as we know, such a delay of phase separation for nonionic detergents, caused by the presence of zwitterionic detergents, is a new phenomenon not described until now, which is of common interest for scientists working with membrane proteins and detergents.…”