A Fluorinated Detergent for Membrane‐Protein Applications

Abstract

Surfactants carrying fluorocarbon chains hold great promise as gentle alternatives to conventional hydrocarbon-based detergents for the solubilization and handling of integral membrane proteins. However, their inertness towards lipid bilayer membranes has limited the usefulness of fluorinated surfactants in situations where detergent-like activity is required. We demonstrate that fluorination does not necessarily preclude detergency, as exemplified by a fluorinated octyl maltoside derivative termed F6 OM. This nonionic compound readily interacts with and completely solubilizes phospholipid vesicles in a manner reminiscent of conventional detergents without, however, compromising membrane order at subsolubilizing concentrations. Owing to this mild and unusual mode of detergency, F6 OM outperforms a lipophobic fluorinated surfactant in chaperoning the functional refolding of an integral membrane enzyme by promoting bilayer insertion in the absence of micelles.

Automated analysis of calorimetric demicellization titrations

“…Here, we show that a combination of both approaches provides an unbiased and reproducible data analysis strategy without the need for user input other than the calorimetric data proper. The approach is explained and exemplified using demicellization isotherms of the fluorinated surfactant F 6 OPC (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-n-octylphosphocholine) and the zwitterionic detergent CHAPSO (3-([3-cholamidopropyl]dimethylammonio)-2-hydroxy-1-propanesulfonate).…”

“…as detailed elsewhere [7][8][9]. Here, Q denotes the normalized heat of reaction, c D the surfactant concentration in the calorimeter cell, and Dc D the above-mentioned parameter affecting the width of the transition range.…”

“…(1), (2), and (4À6) have previously been used [7][8][9] to fit demicellization isotherms that largely differed in terms of CMC, demicellization heat (i.e., signal amplitude), and steepness of the transition. One disadvantage inherent to this earlier approach is that the micellization enthalpy does not show up directly as a fitting parameter but, instead, is calculated from Eqs.…”

“…We have tested this approach on calorimetric data for the demicellization of the fluorinated surfactant F 6 OPC (3,3,4,4,5,5,6,6,7,7, 8,8,8-tridecafluoro-n-octylphosphocholine) [8] and on the zwitterionic detergent CHAPSO (3-([3-cholamidopropyl]dimethylammonio)-2-hydroxy-1-propanesulfonate). Both titrations were carried out on a VP-ITC instrument (Malvern Instruments, Worcestershire, UK) at a stirrer speed of 310 rpm and a filter period of 2 s; additional experimental settings are summarized in Table 1.…”

“…Then, Q demic is obtained from the difference in heat between linear preand post-transition baselines at the CMC [6]. In an alternative approach, a generic sigmoidal function can be fitted to the isotherm to derive the CMC as well as Q demic through nonlinear least-squares fitting [7][8][9]. In both cases, the standard molar micellization enthalpy, DH mic , is then calculated from Q demic .…”