Abstract. Proline homopolymer motifs are found in many proteins;
their peculiar conformational and dynamic properties are often directly
involved in those proteins' functions. However, the dynamics of proline
homopolymers is hard to study by NMR due to a lack of amide protons and small
chemical shift dispersion. Exploiting the spectroscopic properties of
fluorinated prolines opens interesting perspectives to address these issues.
Fluorinated prolines are already widely used in protein structure
engineering – they introduce conformational and dynamical biases – but
their use as 19F NMR reporters of proline conformation has not yet been
explored. In this work, we look at model peptides where Cγ-fluorinated prolines with opposite configurations of the chiral Cγ
centre have been introduced at two positions in distinct polyproline
segments. By looking at the effects of swapping these (4R)-fluoroproline and
(4S)-fluoroproline within the polyproline segments, we were able to
separate the intrinsic conformational properties of the polyproline sequence
from the conformational alterations instilled by fluorination. We assess the
fluoroproline 19F relaxation properties, and we exploit the latter in
elucidating binding kinetics to the SH3 (Src homology 3) domain.