1. Criteria 1.The CF 3 -group has to be attached rigidly to the peptide backbone. 2.The CF 3 -AA should be compatible with standard solid phase peptide synthesis (SPPS) protocols, react rapidly and without racemization. 3. To replace a natural amino acid, the CF 3 -AA must not perturb the characteristics of the peptide (polarity, conformation, function). our ``new`` 19 F-NMR labels Synthesis of novel CF 3 -substituted α-amino acids as 19 F-NMR labels P. K. Mykhailiuk a, S. Afonin b, N. Gvozdovska a, P. Wadhwani b, M. Berditsch c, M. Ieronimo c, S. L. Grage b, A. S. Ulrich b,c, I. V. Komarov a a Kyiv National Taras Shevchenko University, Kyiv, Ukraine b Institute of Biological Interfaces, Forschungszentrum Karlsruhe, Karlsruhe, Germany c Institute of Organic Chemistry, University of Karlsruhe, Karlsruhe, Germany Criterion 1: rigid structure (X-ray analysis) Introduction CF 3 -substituted α-amino acids (CF 3 -AA) are highly useful as 19 F-NMR labels. They are especially informative in solid-state NMR studies of peptides in biomembranes. To be a ``good`` label the CF 3 -AA should meet several criteria. previously used 19 F-NMR labels CF 3 -Bpg CF 3 -Phg Criterion 3: unperturbed peptide (CD, biological function) 9-(CF 3 Bpg)-PGLa A single CF 3 -Bpg label was substituted in four different positions of the α-helical peptide PGLa: GMASKAGAI 9 A 10 GKI 13 A 14 KVALKAL-NH 2 Circular dichroism showed that a single CF 3 -Bpg label does not perturb the conformation of the peptide. 14-(CF 3 Bpg)-PGLa 10-(CF 3 Bpg)-PGLa 13-(CF 3 Bpg)-PGLa wild type-PGLa The antimicrobial α-helical peptide PGLa was used to test the incorporation of the „old“ CF 3 -Phg and the „new“ CF 3 -Bpg label. The antimicrobial function of the four labelled analogues of PGLa was tested, and all minimal inhibitory concentrations were found to be identical to the wild type peptide Synthetic schemes References 3. Mykhailiuk, P. K. et al, Angew. Chem. Int. Ed. 2006, 45, 5659-5661. 4. Afonin, S. et al, J. Pept. Sci. 2007, in print. 5. Mykhailiuk, P. K. et al, Angew. Chem. Int. Ed. 2007, submitted. 1. Ulrich A. et al, Prog. NMR Spectr. 2005, 46, 1-21. 2. Glaser R. et al, Biophysical Journal 2005, 88, 3392-3397. Contact: pashamk@gmx.de Several novel conformationally restricted CF 3 -labelled α-amino acids have been synthesized. These amino acids were designed as 19 F-NMR labels for solid state NMR studies of membrane-bound peptides. CF 3 -Bpg has been demonstrated to fulfil all criteria for optimal use as a 19 F-NMR. The application of the new CF 3 -Pro analogues as 19 F-NMR labels is currently under investigation. Conclusions F 3 -Aib F 3 -Ala CF 3 (3/4)-Pro CF 3 (4/5)-Pro Criterion 2: successful peptide synthesis (RP-HPLC) HPLC of 13-(CF 3 -Phg)-PGLa L-(CF 3 -Phg) racemizes during peptide synthesis. 2 diastereomers of 13-(CF 3 - Phg)-PGLa (containing D- and L-CF 3 -Phg) are formed. HPLC of 13-(CF 3 -Bpg)-PGLa L-(CF 3 -Bpg) does not racemize during solid phase Fmoc peptide synthesis. RT (min) λ (nm) MRE -15 -10 -5 0 5 10 15 20 25 30 180190200210220230240250260 PGLa-wt 15 16 17 18