The Flavin–Tryptophan Dyad F10T as a Cryptochrome Model Compound: Synthesis and Photochemistry

Abstract

Many animals sense the Earth's magnetic field and use it for navigation. It has been proposed that a light‐dependent quantum effect in cryptochrome photoreceptor proteins residing in the retina allow for such an iron‐free spin‐chemical compass. The primary photochemistry in cryptochromes and photolyases is assumed to be confined mainly in a flavin adenine dinucleotide (FAD) residue and three nearby tryptophan residues. Functional studies require model compounds allowing for direct structural modifications. Inspired by the structure of natural cryptochrome, a flavin–tryptophan dyad (F10T) has been synthesized. 1H photochemically induced dynamic nuclear polarization (photo‐CIDNP) NMR studies on F10T demonstrate the spin‐correlated radical‐pair formation through photoinduced electron transfer from donor (tryptophan) to acceptor (flavin) moieties under illumination with a white light source similar to sunlight. This is the first model compound of natural cryptochromes with a provision for controlled structural modifications.

Magnetic field effect in natural cryptochrome explored with model compound

“…This slow process is presumably because of the strong exchange interaction between the two radical-centres. Due to strong coulomb interaction between the positive and the negative charge-centre (radical-centre), in these energy-states the biradicals obtain a deformed-Z-shaped conformation with reduced separation between the radical-centres compared to the Z-shaped conformation 27 . According to the conservation of spin angular momentum, during the fast electron transfer, the radical pair is formed with the same spin multiplicity as its precursor species.…”

“…The synthesis details of F10T are given in Paul et al . 27 . All the solutions were prepared in methanol-d 4 .…”

“…Recently, we presented the dyad compound F10T in which a flavin (F) residue is connected to a tryptophan (Trp) residue via an aliphatic chain (Fig. 1d ) 27 . The centre-to-centre distance between flavin and tryptophan (~16.5 Å) is close to that between FAD and TrpC (~18–20 Å) in natural cryptochromes (Fig.…”

Impact of 2.45 GHz Microwave Irradiation on the Fruit Fly, Drosophila melanogaster

“…No photolyase activity has been reported for cyclobutane pyrimidine dimers or 6–4 photoproducts; however, this protein is known to contribute to sensing Earth’s magnetic field in D. melanogaster [ 20 , 21 ]. This Cry activation is intermediated by radicals [ 10 , 36 ]. Hoang et al [ 36 ] reported that a Cry protein subfamily, which does not possess the light response, also showed photoreaction.…”

“…Evoked electrons under EMFs can affect chemical signaling in cell communications. Paul et al [ 10 ]. reported that EMFs at higher frequencies play an important role in sensing directions, especially in birds.…”