Real‐Time Observation of Diarylethene‐Based Photoswitches in a Cyclic Peptide Environment

Abstract

We report the photophysical properties of diarylethene‐based photoswitches (DAE) which were incorporated into the backbones of macrocyclic peptides of variable sizes (6, 10 and 14 amino acids: cDAE‐6, cDAE‐10, and cDAE‐14). The insertion leads to a consistent bathochromic shift in UV/Vis absorption bands, a considerable peptide‐size‐dependent fluorescence intensity increase (up to a factor of 1.7), and a drastically reduced photoisomerization efficiency leading to formation of the ring‐closed DAE fragment. The compounds were studied by time‐resolved photoinduced broadband absorption spectroscopy, revealing a ring closure reaction for the unconstrained DAE reference system and, to a lesser extent, for cyclic cDAE‐14. The smallest cyclic peptide cDAE‐6 does not undergo any photoisomerization process at all. Furthermore, the DAE fragment ring closure reaction in the reference system is concurrent with intersystem crossing that is complete within a few picoseconds. Further analysis showed dominant triplet absorption throughout the observed spectral window (350–700 nm) in all macrocyclic systems. As a consequence, ring closure is favored in the unconstrained system in contrast to the cyclic peptides. Our studies demonstrate the importance of understanding the population dynamics of DAE rotamers when designing efficiently photocontrollable diarylethene‐based peptidomimetics.

Light-controllable dithienylethene-modified cyclic peptides: photoswitching the in vivo toxicity in zebrafish embryos

“…All peptides (Table 1) were synthesized as was previously described [30] and initially handled as ring-open photoforms under ambient (visual, vis) light conditions. Each of the ringopen photoforms was converted into the ring-closed photoforms by UV irradiation in a solution of denaturing agents, reproducing previously documented results [29,30,52]. All Table 1: Nomenclature, sequences, molecular masses of the peptides synthesized and explored in this study.…”

Photoexcitation of Ge9− Clusters in THF: New Insights into the Ultrafast Relaxation Dynamics and the Influence of the Cation

“…Molecules 2019, 24, x FOR PEER R EVIEW 3 of 22 relaxation pathways. This study also includes results obtained from a new experimental setup [5,41] that now allows long timescale (1 ns) broadband probe in the UV -Vis as well as in the NIR spectral range. This should allow the observation of at least a section of the high-energy tail of the solvated electron spectrum in THF, which still peaks (ca.…”

“…Complementing studies on [(Hyp) 3 Ge 9 ZnGe 9 (Hyp) 3 ] [27,33] (Ge 9 ZnGe 9 ) show a strong influence of dimerization on the long timescale dynamics of the cluster which is crucial for the understanding of possible relaxation pathways. This study also includes results obtained from a new experimental setup [5,41] that now allows long timescale (1 ns) broadband probe in the UV-Vis as well as in the NIR spectral range. This should allow the observation of at least a section of the high-energy tail of the solvated electron spectrum in THF, which still peaks (ca.…”

The influence of the FeCp(CO)2+moiety on the dynamics of the metalloid [Ge9(Si(SiMe3)3)3]−cluster in thf: synthesis and characterization by time-resolved absorption spectroscopy

“…To obtain time resolved spectra in the UV-Vis wavelength range, an experimental setup described elsewhere 47 was used. Briefly, the Astrella laser system (Coherent) generates 38 fs pulses with 800 nm central wavelength at a repetition rate of 1 kHz.…”