23Na and 35/37Cl as NMR probes of growth and shape of sodium taurodeoxycholate micellar aggregates in the presence of NaCl

► Primary-secondary micelles transition of sodium taurodeoxycholate due to NaCl/NaBr. ► It was followed by 23Na longitudinal relaxation times. ► Secondary micelles give 23Na, 35Cl, and 37Cl double quantum filtered NMR spectra. ► They interact strongly with added NaCl and NaBr and have anisotropic shape.