Direct photomodulation of peptide backbone conformationsElectronic Supplementary Information (ESI) available: details of the monochromatic light source, kinetic parameters, UV-vis spectroscopy and capillary electrophoresis. See http://www.rsc.org/suppdata/cc/b3/b309927j/

Abstract

Significant photoswitching ability is found for secondary thioxopeptide bonds and can be used for the photomodulation of the backbone conformation of peptides or proteins.

cis/trans Photoisomerization of Secondary Thiopeptide Bonds

“…Therefore, the equilibrium of the cis and trans conformers of 1 is dualdirectionally photoswitchable. [23] Similar results were also observed for 2-4.…”

“…[23,24] When the new electropherogram was compared to the electropherogram of the nonirradiated peptide, it could be seen that a new peak appeared after irradiation. This peak was assigned to the cis conformer, which was generated by irradiation (supported by its UV-visible spectrum, obtained in situ with a diode-array CE instrument), and its relative concentration was determined to be about 9 % for peptide 1.…”

“…The wavelength-tunable monochromatic light source was described previously. [23] Data analysis of the time-course curves, performed by single-exponential nonlinear regression by using a SigmaPlot scientific graphing system (Version 2000), gave the isomerization rate constants (k obsd ).…”

“…The photoswitch effect discussed above was also applicable to oligothiopeptides, such as the His 12 -thio-S-peptide (a peptide with 20 amino acid residues). [23] Preliminary results show that the activity of the (1) and (2) by using parameter values from Table 4 (solid lines represent the fitting result). For clarity, only half of the recorded raw data points are displayed.…”

An Evaluation of Peptide‐Bond Isosteres

“…Despite the larger rotational barrier, the photoisomerization of a thioamide is more facile than is that of an amide. [15] The photodecomposition during photoisomerization is reduced considerably in thioamides, as the π → π* electronic transition, which is required for photoisomerization, is red-shifted in thioamides (260 nm) relative to amides (200 nm). [16] Photoswitching has been used to increase the population of the cis isomer of prolyl peptide bonds.…”