Water and hydrogen bonds in DMPA and DMPC membranes seen from near infrared spectroscopy

WENZ J.J.

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Comité Organizador

By exploiting the sensitivityof the NIR spectrum to hydrogen bonds, particularly in the first overtone ofwater around 1450/55 nm, the influence of temperature and phospholipid headgroup on the H-bond network and water polymerization in membranes of DMPA andDMPC was studied. Principal components analysis of the spectra was used todisclose subtle spectral changes that mirror alterations in the vibrationalenergy of the water O-H bonds, as a measure of the H-bond network. Increasingtemperatures drastically diminished the number of strongly H-bonded watermolecules and increased the number of weakly H-bonded waters. This dominatingeffect of temperature was missing after the subtraction of the pure waterspectra from the lipid-containing ones, suggesting the presence of two waterpopulations. An intriguing secondary effect of temperature was also revealed. Atthe water:lipid interface, phospholipids exhibited an effect qualitativelysimilar to that of the temperature. DMPA, and particularly DMPC, disrupted theH-bond network in the neighboring water, reducing water polymerization andstrengthening the water O-H bonds. The type of the polar head affects theH-bonds more than duplicate the concentration of the lipid from 250 to 500 μM.A relation between head group structure and the effect on the H-bonds networkand the existence of two populations of water molecules are discussed.