Infrared techniques, such as Fourier-transform infrared spectroscopy (FTIR) can be used to measure the lineshapes associated with the different vibrational modes in the samples. Figure (lower panel) shows an annotated example of an FTIR spectrum with the vibrational modes from phospholipid headgroup, ester linkage, acyl chain, and water molecule across a broad spectral range from 1000 to 4000 cm -1 . The center frequencies and lineshapes of vibrational modes in IR spectra provide molecular information about the phase of the membrane as described by the ordering of the acyl chains, interfacial hydrogen bond networks of water reported by the -OH vibrational mode, and lipid hydration by phosphate headgroup and ester linkage .