Hydrogen Bond Switching among Flavin and Amino Acids Determines the Nature of Proton-Coupled Electron Transfer in BLUF Photoreceptors

BLUF domains are flavin-binding photoreceptors that can be reversibly switched from a dark-adapted state to a light-adapted state. Proton-coupled electron transfer (PCET) from a conserved tyrosine to the flavin that results in a neutral flavin semiquinone/tyrosyl radical pair constitutes the photoactivation mechanism of BLUF domains. Whereas in the dark-adapted state PCET occurs in a sequential fashion where electron transfer precedes proton transfer, in the light-adapted state the same radical pair is formed by a concerted mechanism. We propose that the altered nature of the PCET process results from a hydrogen bond switch between the flavin and its surrounding amino acids that preconfigures the system for proton transfer. Hence, BLUF domains represent an attractive biological model system to investigate and understand PCET in great detail

Visualization 6: Third harmonic generation imaging for fast, label-free pathology of human brain tumors

A depth scan through the transition zone between a low-grade glioma and normal human brain tissue. Originally published in Biomedical Optics Express on 01 May 2016 (boe-7-5-1889

Visualization 3: Third harmonic generation imaging for fast, label-free pathology of human brain tumors

A depth scan through white matter of structurally normal human brain tissue. Originally published in Biomedical Optics Express on 01 May 2016 (boe-7-5-1889

Visualization 5: Third harmonic generation imaging for fast, label-free pathology of human brain tumors

2D inspection mode THG/SHG imaging of a high-grade glioma (glioblastoma) sample. Originally published in Biomedical Optics Express on 01 May 2016 (boe-7-5-1889