  To better understand lipid membranes in living organisms, the study of
intermolecular forces using the osmotic pressure technique applied to model
lipid membranes has constituted the ground knowledge in the field of biophysics
since four decades. However, the study of intermolecular forces in lipid
systems other than phospholipids, like glycolipids, has gained a certain
interest only recently. Even in this case, the work generally focuses on the
study of membrane glycolipids, but little is known on new forms of non-membrane
functional compounds, like microbial bolaform glycolipids. This works explores,
through the osmotic stress method involving an adiabatic humidity chamber
coupled to neutron diffraction, the short-range (< 2 nm) intermolecular forces
of membranes entirely composed of interdigitated glucolipids. Experiments are
performed at pH 6, when the glucolipid is partially negatively charged and for
which we explore the effect of low (16 mM) and high (100 mM) ionic strength. We
find that this system is characterized by primary and secondary hydration
regimes, respectively insensitive and sensitive to ionic strength and with
typical decay lengths of 0.37 +- 0.12 nm and 1.97 +- 0.78 nm.
