Direct observation of a photoinduced radical pair in a cryptochrome blue-light photoreceptor - PubMed (original) (raw)

Direct observation of a photoinduced radical pair in a cryptochrome blue-light photoreceptor

Till Biskup et al. Angew Chem Int Ed Engl. 2009.

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Figures

Figure 1

Figure 1

The conserved Trp triad of _Xl_Cry-DASH. (a) Three-dimensional protein structure homology model from the SWISS-MODEL repository (UniProt ID: CRYD_XENLA). (b) Sequence alignment of five members of the photolyase/cryptochrome family. The conserved Trp residues of the putative ET chain in E. coli photolyase (PHR_ECOLI), Syn. Cry-DASH (CRYD_SYNSP), _Xl_Cry-DASH (CRYD_XENLA), garden warbler Cry-1a (CRY1a_GW), and A. thaliana Cry-1 (CRY1_AT) are marked with green triangles. Columns with an alignment score >0.7 are surrounded with a blue frame and the conserved amino acids colored red on white background. If the residues are strictly conserved, they are colored white on red background. The alignment was performed with MultAlin[42] and further processed with ESPript 2.2.[43]

Figure 2

Figure 2

Optical absorption spectra of _Xl_Cry-DASH recorded at 273 K show the FAD cofactor in different oxidation states: FADox (solid line), FADH• (dotted line), and FADH− (dashed line). The inset shows _Xl_Cry-DASH with the FADox cofactor before illumination (solid line), and _Xl_Cry-DASH reoxidized by aerial oxygen after 12 hours of blue-light illumination (dotted line). This is to demonstrate that the protein remains intact in terms of its cofactor contents even upon intensive light illumination conditions.

Figure 3

Figure 3

Complete TREPR data set of _Xl_Cry-DASH measured at 274 K. To control for potential shape changes in the TREPR signal caused by gradual sample degradation, spectra were recorded from low to high magnetic field followed by detection in the opposite magnetic-field direction. Each time profile is the average of 120 acquisitions recorded with a laser pulse repetition rate of 1.25 Hz, a microwave frequency of 9.68 GHz, and a power of 2 mW at a detection bandwidth of 100 MHz. A: enhanced absorption; E: emission.

Figure 4

Figure 4

TREPR spectrum of WT (solid blue curve) and W324F (solid green curve) _Xl_Cry-DASH recorded 500 ns after pulsed laser excitation. Experimental parameters were as in Fig. 3. The dashed curve shows a spectral simulation of the WT protein EPR data using the following parameters: gFAD = (2.00431, 2.00360, 2.00217), gTrp = (2.00370, 2.00285, 2.00246), Ω(gFAD⋯gTrp) = (126.5°, 76.5°, 246.5°), D = −0.36 mT, E = 0, Ω(gFAD⋯D) = (0°, 109.9°, 110.5°), J = +0.24 mT.

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