Tryptophan-Laurdan interaction in ester and ether PC membrane interfaces

HUGO A. PÉREZ; AGUSTIN GONZALES PAZ; DISALVO, EDGARDO ANIBAL; MARÍA DE LOS ANGELES FRIAS

San Luis

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Biofísica; 2019

Sociedad Argentina de Biofísica

Numerousinvestigations have been carried out to interpret the role of tryptophan (Trp) inthe peptides and proteins (such as melittin1, annexins2,among other molecules of biological importance) interaction with lipid membranesthrough various techniques, such as NMR3, FTIR, X ray diffraction,among others. In particular, studies using Laurdan as a fluorescent probe hasbeen extensively done to have an insight on the hydration states of theinterface. In this regard, the presence or absence of hydration centers such ascarbonyl groups can be decisive in the interaction of Trp with membranes.In thiswork, the interaction of Trp with lipid membranes models composed of ester andether lipids of different chain lengths in the presence of the Laurdanfluorescent probe is studied.The resultsshow that there is an interaction between Trp and Laurdan, regardless of thephase state in 1,2-dimyristoyl-sn-glycero-3-phosphocholine multilamellarvesicles (14: 0 PC-DMPC) and 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine(14: 0-DTPC). The values of the Stern Volmer constant (KSV) are approximatelyof 75 M-1, in both cases. In contrats, in vesicles of1,2-dipalmitoyl-sn-glycero-3-phosphocholine (16: 0-DPPC) and1,2-di-O-hexadecyl-sn-glycero-3-phosphocholine (16: 0-DHPC), the phase stateaffects Laurdan quenching by Trp, obtaining values of KSV ≈  55 M-1 for the gel phase and KSV≈ 80 M-1for crystalline liquid. These results indicate that the presence or absence ofthe carbonyl group for lipids having the same chain length does not influencethe penetration of Trp at the interface. However, the chain length produces a lower efficiency ofgel phase quenching when the lipid chain length increases. The latter suggeststhat vesicles formed by DPPC and DHPC in gel phase have a higher degree ofinterface ordering compared to DMPC and DTPC, decreasing the entrance of Trp inthe interface.