Improved dilute bicelle solutions for high-resolution NMR of biological macromolecules

Dissolving biological macromolecules in dilute bicelle solutions, which form oriented liquid crystals in the presence of a magnetic field, permits measurement of anisotropic spin interactions such as dipolar couplings [Tjandra, N. and Bax, A., Science, 278, 1111-1114]. However, the lifetimes and temperature ranges of orientation for these samples are critically dependent on sample composition and experimental conditions. This paper demonstrates that doping dilute bicelle solutions with small amounts of charged amphiphiles substantially improves the stability and degree of alignment, as well as extends the temperature range of orientation for these systems. An explanation of the dependence of bicelle aggregation on sample composition is proposed based on the DLVO theory of colloids.