Role of Guanidyl Moiety in the Insertion of Arginine and Nα-Benzoyl-l-argininate Ethyl Ester Chloride in Lipid Membranes

Abstract

Role of Guanidyl Moiety in the Insertion of Arginine and Nα-Benzoyl-l-argininate Ethyl Ester Chloride in Lipid Membranes AbstractFull Text HTMLHi-Res PDF[1247 KB]PDF w/ Links[216 KB]FiguresReferencesA. C. Fonseca‡, M. A. Frías†, A. M. Bouchet†, S. Jarmelo‡§, P. N. Simões‡, R. Fausto§, M. H. Gil‡, F. Lairion† and E. A. Disalvo*† Laboratory of Physical Chemistry of Lipid Membranes, Department of Analytical Chemistry and Physical Chemistry, Pharmacy and Biochemistry, University of Buenos Aires Junín 956 2° piso (1113), Buenos Aires, Argentina, Department of Chemical Engineering, University of Coimbra, Polo II, Pinhal de Marrocos, 3030-790 Coimbra, Portugal, and Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal J. Phys. Chem. B, 2010, 114 (17), pp 5946–5952 DOI: 10.1021/jp101007b Publication Date (Web): April 13, 2010 Copyright © 2010 American Chemical Society

* Corresponding author. Phone: 54 11 39648249. Fax: 54 11 45083645. E-mail: eadisal@yahoo.com.ar., † Department of Analytical Chemistry and Physical Chemistry, Pharmacy and Biochemistry, University of Buenos Aires Junín 956 2° piso (1113). , ‡ Department of Chemical Engineering, University of Coimbra. , § Department of Chemistry, University of Coimbra.

AbstractGuanidyl moieties of both arginine (Arg) and Nα-benzoyl-l-argininate ethyl ester chloride (BAEE) are protonated in all environments studied, i.e., dry solid state, D2O solutions, and dry and hydrated lipids as suggested by DFT(B3LYP)/6-31+G(d,p) calculations. Arg and BAEE are able to insert in the lipid interphase of both DMPC and DOPC monolayers as revealed by the observed decrease in the membrane dipole potential they induce. The larger decrease in the dipole potential induced by BAEE, compared to Arg, can be explained partially by the higher affinity of the hydrophobic benzoyl and ethyl groups for the membrane phase, which allows an easier insertion of this molecule. FTIR studies indicate that the guanidyl moiety of Arg is with all probability facing the hydrophobic part of the lipids, whereas in BAEE this group is facing the water phase. Zeta potential measurements provide a direct evidence that Arg orients in the lipid interphase of phosphatidylcholine (PC) bilayers with the negative charged carboxylate group (−COO−) toward the aqueous phase.