Flavin mononucleotide (FMN) belongs to the group of very efficient endogenous photosensitizers producing singlet oxygen, ¹O₂, but with limited ability to be targeted. On the other hand, in genetically-encoded photosensitizers, which can be targeted by means of various tags, the efficiency of FMN to produce ¹O₂ is significantly diminished due to its interactions with surrounding amino acid residues. Recently, an increase of ¹O₂ production yield by FMN buried in a protein matrix was achieved by a decrease of quenching of the cofactor excited states by weakening of the protein-FMN interactions while still forming a complex. Here, we suggest an alternative approach which relies on the blue light irradiation-induced dissociation of FMN to solvent. This dissociation unlocks the full capacity of FMN as ¹O₂ producer. Our suggestion is based on the study of an irradiation effect on two variants of the LOV2 domain from Avena sativa; wild type, AsLOV2 wt, and the variant with a replaced cysteine residue, AsLOV2 C450A. We detected irradiation-induced conformational changes as well as oxidation of several amino acids in both AsLOV2 variants. Detailed analysis of these observations indicates that irradiation-induced increase in ¹O₂ production is caused by a release of FMN from the protein. Moreover, an increased FMN dissociation from AsLOV2 wt in comparison with AsLOV2 C450A points to a role of C450 oxidation in repelling the cofactor from the protein.

黄素单核苷酸（FMN）属于非常有效的内源性光敏剂，可产生单线态氧¹ O ₂，但靶向能力有限。另一方面，在可以通过各种标签靶向的遗传编码的光敏剂中，FMN产生¹ O ₂的效率由于与周围氨基酸残基的相互作用而大大降低。最近增加了¹ O ₂通过掩埋在蛋白质基质中的FMN相互作用减弱了辅因子激发态的猝灭，从而实现了掩埋在蛋白质基质中的FMN的生产产量。在这里，我们建议一种替代方法，该方法依赖于蓝光辐照引起的FMN与溶剂的离解。这种解离释放了FMN作为¹ O ₂生产者的全部能力。我们的建议基于对Avena sativa的LOV2结构域的两个变体的辐照作用研究; 野生型AsLOV2 wt和具有取代的半胱氨酸残基的变体AsLOV2 C450A。我们检测到辐射诱导的构象变化以及两个AsLOV2变体中的几个氨基酸的氧化。对这些观察结果的详细分析表明，辐射诱导的¹ O ₂产量增加是由蛋白质中FMN的释放引起的。而且，与AsLOV2 C450A相比，从AsLOV2 wt增加的FMN解离表明C450氧化在从蛋白质排斥辅因子中的作用。