Modification by transferrin increases the efficiency of delivery and the photodynamic effect of the quantum dot-phthalocyanine complex on A431 cells.

Hybrid complexes of fluorescent nanoparticles and tetrapyrrole dyes are currently considered as promising third-generation photosensitizers for photodynamic therapy, including cancer treatment. Using nanoparticles as a platform for delivery of photosensitizers to target cells can increase the efficiency of photodynamic action. In this work, we synthesized a complex of polymer-coated CdSe/ZnS quantum dots, substituted phthalocyanines and human transferrin. Such complexes effectively enter human epidermoid carcinoma cells (A431) due to transferrin-mediated endocytosis and are localized in the perinuclear compartment. We observed an efficient excitation energy transfer from the quantum dot to phthalocyanine in the cells, which indicates stability of the complex upon its internalization. It was shown that the photodynamic activity of hybrid complexes covalently bonded to transferrin is 15% higher than the activity of unmodified hybrid complexes. Our results confirm the feasibility of using fluorescent nanoparticles to enhance the photodynamic properties of photosensitizers based on tetrapyrrole dyes.

[Femtolaser-assisted refractive autokeratoplasty in the management of advanced keratoconus (three-years outcomes)]. / Femtolazernaia refraktsionnaia autokeratoplastika v lechenii dalekozashedshikh stadii keratokonusa (trekhletnie rezul'taty).

PURPOSE: To evaluate the long-term results of a new method of femtosecond laser-assisted refractive autokeratoplasty (FRAK) in the management of advanced keratoconus. MATERIAL AND METHODS: The study included 45 patients with stable advanced keratoconus (31 males, 14 females; stage III of the disease - 5 eyes, stage IV - 40 eyes). All patients were operated and observed at the 10th Minsk City Hospital (the follow-up period varied from 12 months to 3 years). Mean age was 33.8±10.1 years (16 to 55 years). Uncorrected visual acuity (UCVA) was 0.07±0.03 (0.02 to 0.1). FRAK was performed with the use of the femtolaser device 'IntraLase 60 kHz'. The principal idea behind the new method is reshaping patient's conically changed cornea by performing a 2-step resection of corneal stroma, removing the tissue flap and suturing. RESULTS: UCVA significantly improved from 0.07±0.03 to 0.26±0.11 at 12 months after the surgery (from 0.08 to 0.5). UCVA varied from 0.2 to 0.5 in 77.8% of patients (p<0.05). Mean best corrected visual acuity (BCVA) was 0.4±0.18 (0.2 to 0.7) in 24-36 months postoperatively. The indices of keratotopography significantly improved: Ks 49.8±4.7 D, Kf 44.2±5.19 D, Cyl 4.8±1.9 D, Kmax 53.7±3.9 D (p<0.05). 82.2% of patients were satisfied with resulting visual acuity. CONCLUSION: Long term results of FRAK prove that this method allows reshaping of optical zone of the cornea in advanced keratoconus, improving both UCVA and BCVA while avoiding corneal transplantation and improving the quality of patient's life.

The photocycle of orange carotenoid protein conceals distinct intermediates and asynchronous changes in the carotenoid and protein components.

The 35-kDa Orange Carotenoid Protein (OCP) is responsible for photoprotection in cyanobacteria. It acts as a light intensity sensor and efficient quencher of phycobilisome excitation. Photoactivation triggers large-scale conformational rearrangements to convert OCP from the orange OCPO state to the red active signaling state, OCPR, as demonstrated by various structural methods. Such rearrangements imply a complete, yet reversible separation of structural domains and translocation of the carotenoid. Recently, dynamic crystallography of OCPO suggested the existence of photocycle intermediates with small-scale rearrangements that may trigger further transitions. In this study, we took advantage of single 7 ns laser pulses to study carotenoid absorption transients in OCP on the time-scale from 100 ns to 10 s, which allowed us to detect a red intermediate state preceding the red signaling state, OCPR. In addition, time-resolved fluorescence spectroscopy and the assignment of carotenoid-induced quenching of different tryptophan residues derived thereof revealed a novel orange intermediate state, which appears during the relaxation of photoactivated OCPR to OCPO. Our results show asynchronous changes between the carotenoid- and protein-associated kinetic components in a refined mechanistic model of the OCP photocycle, but also introduce new kinetic signatures for future studies of OCP photoactivity and photoprotection.

Features of Protein-Protein Interactions in the Cyanobacterial Photoprotection Mechanism.

Photoprotective mechanisms of cyanobacteria are characterized by several features associated with the structure of their water-soluble antenna complexes - the phycobilisomes (PBs). During energy transfer from PBs to chlorophyll of photosystem reaction centers, the "energy funnel" principle is realized, which regulates energy flux due to the specialized interaction of the PBs core with a quenching molecule capable of effectively dissipating electron excitation energy into heat. The role of the quencher is performed by ketocarotenoid within the photoactive orange carotenoid protein (OCP), which is also a sensor for light flux. At a high level of insolation, OCP is reversibly photoactivated, and this is accompanied by a significant change in its structure and spectral characteristics. Such conformational changes open the possibility for protein-protein interactions between OCP and the PBs core (i.e., activation of photoprotection mechanisms) or the fluorescence recovery protein. Even though OCP was discovered in 1981, little was known about the conformation of its active form until recently, as well as about the properties of homologs of its N and C domains. Studies carried out during recent years have made a breakthrough in understanding of the structural-functional organization of OCP and have enabled discovery of new aspects of the regulation of photoprotection processes in cyanobacteria. This review focuses on aspects of protein-protein interactions between the main participants of photoprotection reactions and on certain properties of representatives of newly discovered families of OCP homologs.