Infrared probing of 4-azidoproline conformations modulated by azido configurations.

4-Azidoproline (Azp) can tune the stability of the polyproline II (P(II)) conformation in collagen. The azido group in the 4R and 4S configurations stabilizes and destabilizes the P(II) conformation, respectively. To obtain insights into the dependence of the conformational stability on the azido configuration, we carried out Fourier transform (FT) IR experiments with four 4-azidoproline derivatives, Ac-(4R/S)-Azp-(NH/O)Me.