1. Nuclear Magnetic Resonance Facility; IQAC-CSIC; Jordi Girona, 18-26 08034 Barcelona Spain
2. Unit of Synthesis and Biomedical Applications of Peptides; IQAC-CSIC; Jordi Girona, 18-26 08034 Barcelona Spain
3. Department of Chemical Engineering (ETSEIB); Universitat Politecnica de Catalunya; 08034 Barcelona Spain
4. Present address: AIDS Immunopathology Unit; Centro Nacional Microbiología; Instituto de Salud Carlos III; 28029 Madrid Spain
5. AIDS Research Unit; Hospital Clínic; 08034 Barcelona Spain