Switchable Solubility of Azobenzene‐Based Bolaamphiphiles

Abstract

The ability to design amphiphiles with predictable solubility properties is of everlasting interest in supramolecular chemistry. Relevant structural parameters include the hydrophobic–hydrophilic balance and structural flexibility. In this work, we investigate the water solubility of azobenzene‐based triglycerol bolaamphiphiles (TGBAs). In particular, we analyzed the structural effects of backbone hydrophobicity, flexibility, and cis/trans isomerization on the water solubility of a subset of five TGBAs. This leads to the first example of a non‐ionic bolaamphiphile whose water solubility can be changed by irradiation with light. The underlying kinetics were monitored using liquid chromatography and a closer analysis of the underlying aggregation processes provides a mechanistic understanding of the light‐driven dissolution process. We anticipate that the results obtained will help to engineer bolaamphiphiles with predictable solution properties in the future.

A new azobenzene-based design strategy for detergents in membrane protein research

“…Previous studies focused on the structure-based understanding of their self-assembly in solution and the potential of their aggregates to be used for the transport of hydrophobic guests. 23,24,27,42,43 The self-assembly and macroscopic properties of OGBAs and OGDs depend on the length of the hydrophobic alkyl chains, the size of the head group, and the isomeric state of azobenzene. Changing the length of alkyl linkers in [G1] OGBAs, for example, leads to detergents which exhibit either photo-switchable water-solubility, 27 photoswitchable aggregation behaviour, 24,27 or a strong propensity to form photo-resistant H-aggregates.…”

“…Changing the length of alkyl linkers in [G1] OGBAs, for example, leads to detergents which exhibit either photo-switchable water-solubility, 27 photoswitchable aggregation behaviour, 24,27 or a strong propensity to form photo-resistant H-aggregates. 27…”

“…The molecular shape of azobenzene detergents inuences their self-assembly in solution. 14,24,27 IM-MS is sensitive to the overall shape of molecules and therefore a valuable tool to deduce changes in molecular shape of azobenzene-based compounds. 24,44,47 To study how the shape of azobenzene detergents is affected by (i) the isomeric state, (ii) general molecular architecture, and (iii) structure of the hydrophobic backbone, we analysed the CCS values of cis and trans 1-10.…”

“…Second, long alkyl spacers facilitate more conformational freedom. 27 In comparison to OGBAs, only one head group is present in OGDs rendering a collapse of the gas-phase structure unlikely. As a consequence, clearly separated CCS values are obtained from singly charged cis and trans OGDs 6-10 (Fig.…”

“…[14][15][16] Research on azobenzene detergents has been focused on photoresponsive surface coatings, [17][18][19][20] catalysis systems, 21 and supramolecular aggregates. [22][23][24][25][26][27] The utility of anionic 4-hexylphenylazosulfonate for denaturing top-down proteomics has been outlined very recently. 28 As ionic detergents commonly denature membrane proteins more than non-ionic detergents, 29 this inspired us to investigate whether non-ionic azobenzene detergents can be used for the non-denaturing structural analysis of membrane proteins.…”