Affinity of Phenylalanine Carbonyl Domains in DPPC/DMPC Membranes

BRANDAN CARDOZO MARIA ADRIANA; DISALVO ANIBAL; PÉREZ, H.A.; FRÍAS, M. DE LOS ÁNGELES

Córdoba

Congreso; LI Reunión Anual de la Sociedad Argentina de Biofísica; 2023

Sociedad Argentina de Biofísica

L-Phenylalanine (L-Phe) is an essential amino acid present in proteins that participate inbiochemical processes. It has been reported that L-Phe affinity is related to the membranestate and its water content [1-4]. In this work, it is shown that L-Phe interacts significantlywith membranes composed by 9:1 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine  (DPPC)  at  22C  but  not  with  1:9  DMPC/DPPC mixtures at the same temperature. In addition, no effect is observed when DPPC inthe 9:1 mixture with DMPC was replaced by DHPC a lipid lacking of carbonyl groups (CO).The membrane composed by 9:1 DMPC/DPPC shows an increase in the area per moleculein monolayers due to the presence of L-Phe, but not in the other lipid mixtures. Fouriertransform infrared  spectroscopy -  Attenuated  Total  Reflectance (FTIR-ATR) results showthat L-Phe interacts with the CO groups affecting also the phosphate, and choline groups.In contrast, when DPPC was replaced by DHPC no effect on phosphate (PO) and CO groupswere detected. It is concluded that DPPC forms defects in the gel state in a membranedominated by DMPC in the liquid-expanded state with a specific affinity for L-Phe at pH5.5.The results suggest that in  a mixture 9:1 DMPC/DPPC L-Phe inserts in  defects probablyforming  hydrogen  bonds  with  CO  groups  of  DPPC  in  the  condensed  state  which  ispropagated  to PO and  choline groups. The defects are due to the differences in  statephases between both lipids and their water content.