Investigating the water structures in reverse micelles by temperature-dependent near infrared spectroscopy combined with independent component analysis

Confined water has an important effect on the structural stability and biological activity of biomolecules. Reverse micelles (RM) are a good system for investigating the structure of water in confined environment. In this work, the structure of water in RMs with different water content (w0) was studied using near infrared spectra measured at different temperature. Independent component analysis was used to extract the spectral features changing with the w0 and temperature. Three independent components representing the spectral features of trapped water, bound water, and core water were obtained. Furthermore, through the variation of the trapped water and bound water with temperature, an increase of the former and a reduction of the latter were found, revealing that the two water structures play an important role for the mobility of the RM’s shell.