Interaction of L-phenylalanine with carbonyl groups in mixed lipid membranes

The interaction of L-Phe with the membrane components, i.e., lipids and proteins, has been discussed in the current literature due to the interest to understand the effect of single amino acids in relation to the formation of amyloid aggregates. In the present work, it is shown that L-Phe interacts with 9:1 DMPC (1,2-dimyristoyl-sn-glycero-3 phosphocholine)/DPPC (1,2-dipalmitoyl-sn-glycero-3 phosphocholine) mixtures but not in the 1:9 one. An important observation is that the interaction disappears when DPPC is replaced by diether PC (2-di-O-hexadecyl-sn-glycero-3-phosphocholine) a lipid lacking carbonyl groups (CO). This denotes that CO groups may interact specifically with L-Phe in accordance with the appearance of a new peak observed by Infrared spectroscopy (FTIR-ATR). The interaction of L-Phe affects the compressibility pattern of the 9:1 DMPC/DPPC mixture which is congruent with the changes observed by Raman spectra. The specific interaction of L-Phe with CO, propagates to phosphate and choline groups in this particular mixture as analyzed by FTIR-ATR spectroscopy and is absent when DMPC is dopped with diether PC.