Protein Design Group, National Centre for Biotechnology (CNB-CSIC) C/Darwin, 3. Campus U. Autónoma, 28049 Cantoblanco, Madrid, Spain. pazos@cnb.uam.es|Protein Design Group, National Centre for Biotechnology (CNB-CSIC) C/Darwin, 3. Campus U. Autónoma, 28049 Cantoblanco, Madrid, Spain. pazos@cnb.uam.es|Protein Design Group, National Centre for Biotechnology (CNB-CSIC) C/Darwin, 3. Campus U. Autónoma, 28049 Cantoblanco, Madrid, Spain. pazos@cnb.uam.es