The spectral manifistation of the new luminescent styryl dyes photostability and phototoxic influence on the DNA

У роботі запропоновано методи спектральних досліджень фотостабільності та фото- токсичного впливу люмінесціюючих зондів-барвників на ДНК. Досліджено спектри оптичного поглинання, флюоресценції та фосфоресценції нових стирилових барвників та систем ДНК+барвник. Спектри оптичного поглинання досліджуваних сполук реєструвалися під час опромінювання зразків цих речовин видимим світлом. У роботі аналізуються результати цих експериментів, проведені на низці барвників. Зафіксовано зміни оптичної густини D розчинів систем ДНК+барвник на ділянці спектра 250+300 нм (що відповідає першому електронному переходу в ДНК) та 370+650 нм (що відповідає першому електронному переходу в молекулах барвників). Динаміка D(t) не є монотонною. Показано, що бавники Mn-Styr ma Di-Styr-30 є фотохімічно безпечними для ДНК; ці барвники є більш фотостабільними у зв 'язаному з ДНК стані, ніж: у вільному. Барвники Di-Styr-24 ma Dst-MdO, на відміну від попередніх, проявляють невеликий фототоксичний вплив на ДНК. Пропонуються версії щодо можливих механізмів фотогтокичності (та фотостабільності).The spectral investigation methods of the phenomena of luminescent dye probes photostability and phototoxic influence on the DNA were proposed. The optical absorption, fluorescence and phosphorescence spectra of the samples of the newest investigated styryl dyes and the systems DNA +dye were studied. The optical absorption spectra of the samples of these compounds were measured under the irradiation of these samples by visible light. The results of the investigations carried out on a number of dyes were analyzed and discussed. The changes of optical density D value in wavelength regions 250+300 nm (that corresponds to the DNA first electronic transition) and 370+650 nm (that corresponds to a dye electronic transition) of the DNA+dye solutions were fixed. The dynamics ofD(t) was not monotonous. It was shown the Mn-Styr and Di-Styr-30 dyes are photochemically safe for the DNA; these dyes bound to the DNA are more photostable than in free state. The Di-Styr-24 and Dst-MdO dyes show slight phototoxic effect on the DNA. The versions of possible phototoxicity (and photostability) mechanisms are proposed

Uptake of Chlorin e6 Photosensitizer by Polystyrene-Diphenyloxazole-Poly(N-Isopropylacrylamide) Hybrid Nanosystem Studied by Electronic Excitation Energy Transfer

Abstract Polystyrene (PS)-diphenyloxazole (PPO) nanoparticles with attached cross-linked poly-N-isopropylacrylamide (PNIPAM) chains were obtained resulting in PS-PPO-PNIPAM hybrid nanosystems (NS). Fluorescence spectra of chlorin e6 added to PS-PPO-PNIPAM hybrid NS revealed electronic excitation energy transfer (EEET) from PS matrix and encapsulated PPO to chlorin e6. EEET efficiency increased strongly during 1 h after chlorin e6 addition, indicating that uptake of chlorin e6 by PNIPAM part of hybrid NS still proceeds during this time. Heating of PS-PPO-PNIPAM-chlorin e6 NS from 21 to 39 °C results in an enhancement of EEET efficiency; this is consistent with PNIPAM conformation transition that reduces the distance between PS-PPO donors and chlorin e6 acceptors. Meanwhile, a relatively small part of chlorin e6 present in the solution is bound by PNIPAM; thus, further studies in this direction are necessary

Прояв у спектрах фотолюмінесценції та КРС впливу препарату берберину на ДНК

За допомогою спектрів електронного поглинання та фосфоресценції було досліджено розташування енергетичних рівнів ДНК, перенесення енергії електронного збудження триплетними рівнями та його відношення до руйнування ДНК під дією УФ-випромінювання. Показано, що найнижчий збуджений триплетний електронний рівень ДНК (а також: і найвищий синглетний) належить аденіновій ланці. Однак основними пастками триплетних збуджень в ДНК є AT- послідовності і фосфоресценція ДНК, пов'язана саме з цими пастками. Припускається, що мобільні триплетні збудження в ДНК можуть поширюватися на відстані, що дорівнюють довжині 16 базових пар нуклеотидів. Згідно з отриманими даними, переважна більшість триплетних збуджень у ДНК зрештою локалізується на фотостабільних пастках, пов 'язанш з АТ-послідовностями. Таким чином, ієрархія розташування електронних рівнів баз ДНК сприяє процесу перенесення енергії електронного збудження триплетними рівнями, що призводить до істотного стримування фотохімічного руйнування ДНК. Цей факт доведено дослідженнями, спричиненого УФ-випромінюванням фоторуйнування ДНК та модельних базових сполук. Останнє доводить існування механізму самозахисту ДНК проти руйнування π-електронних систем цієї макромолекули (спричиненого їх збудженням різного походження).The displacement of the DNA electronic energy levels, triplet electronic excitation energy transfer and their relation to the DNA damage under UV-irradiation were investigated by electronic absorption and phosphorescence studies. The lowest excited electronic triplet levels of the DNA (as well as the highest singlet levels) were shown to be related with adenine bases. However the AT-sequences are main traps for triplet excitation in the DNA and the DNA phosphorescence is connected namely with these traps. It was supposed that mobile triplet excitations in the DNA could spread on the distance of about 16 base pairs. According to the obtained results, main part of the triplet excitations in the DNA is finally localized on the photostable traps associated with AT-sequences. Thus, the hierarchy of the DNA bases electronic levels positions favors the triplet electronic excitation energy transfer process that leads to inhibition of photochemical destruction of the DNA. It was shown by the investigation of the DNA and base model compounds photodamage induced by UV-irradiation. The latter proves the existence of the DNA self-protection mechanism against damage of p-electronic systems of this macromolecule (caused by their excitations of different origins)

Energy Transfer in Ce0.85Tb0.15F3 Nanoparticles-CTAB Shell-Chlorin e6 System

Abstract Formation and electronic excitation energy transfer process in the nanosystem consisting of Ce0.85Tb0.15F3 nanoparticles, cetrimonium bromide (CTAB) surfactant, and chlorin e6 photosensitizer were studied. It was shown that chlorin e6 molecules bind to Ce0.85Tb0.15F3 NP in the presence of CTAB forming thus Ce0.85Tb0.15F3 NP-CTAB-chlorin e6 nanosystem. We consider that binding occurs via chlorin e6 embedding in the shell of CTAB molecules, formed around NP. In the Ce0.85Tb0.15F3 NP-CTAB-chlorin e6 nanosystem, electronic excitation energy transfer from Ce3+ to chlorin e6 takes place both directly (with the 0.33 efficiency for 2 μM chlorin e6) and via Tb3+

Application of MALDI-TOF mass spectrometry for study on fibrillar and oligomeric aggregates of alpha-synuclein

Aim. To study the α-synuclein (ASN) aggregates of different structural origin, namely amyloid fibrils and spherical oligomers, in comparison with a native protein. Methods. MALDI TOF mass spectrometry and atomic force microscopy (AFM). Results. The mass spectra of native and fibrillar ASN have similar character, i. e. they are characterized by the well pronounced peak of protein molecular ion, the low molecular weight associates, and rather low contain of fragmentation products. The spectrum of oligomeric aggregate is characterized by the high contain of fragmentation products, low intensity of protein molecular ion and the absence of peaks of associates. Conclusions. The difference between the spectra of fibrillar and oligomeric ASN could be explained, first, by the different content of the «residual» monomeric ASN and the protein degradation products in the studied samples, and, second, by the different structure-depended mechanisms of the protein degradation induced by the laser ionization. We suggested that theMALDI-TOF mass spectroscopy is a method useful for the investigation of ASN aggregation and characterization of its high order self-associates; besides, there is an interest in estimating the potency of the MALDI-TOF for the analysis of aggregation of various amyloidogenic proteins

Studies of Interaction Between Cyanine Dye T-284 and Fibrillar Alpha-Synuclein

A key feature of Parkinson’s disease is the formation and accumulation of amyloid fibrils of the natively unfolded protein α-synuclein (ASN) inside neurons. Recently we have proposed novel sensitive monomethinecyanine dye T-284 as fluorescent probe for quantitative detection of ASN amyloid fibrils. In this study the T-284 dye complex with ASN fibril was characterized by means of fluorescence anisotropy, atomic force microscopy and time-resolved fluorescence techniques to give further insights into the mode of dye interaction with amyloid fibrils. The fluorescence anisotropy of T-284 was shown to noticeably increase upon addition of aggregated proteins indicating on stable dye/amyloid fibril complex formation. AFM imaging of fibrillar wild-type ASN revealed differences in heights between ASN fibrils alone and in presence of the T-284 dye (6.37 ± 1.0 nm and 8.0 ± 1.1 nm respectively), that is believed to be caused by embedding of T-284 dye molecules in the “binding channel” running along the fibril. Fluorescence decay analysis of the T-284 in complexes with fibrillar ASN variants revealed the fluorescence lifetime values for T-284/fibril complexes to be an order of magnitude higher as compared to the free dye. Also, the fluorescence decay of free T-284 was bi-exponential, while dye bound to protein yields tri-exponential decay. We suppose that in complexes with fibrillar ASN variants T-284 dye might exist in different “populations” due to interaction with fibrils in different conformers and ways. The exact binding mode of T-284 with ASN fibrils needs further studies. Studied parameters of dye/amyloid fibril complexes are important for the characterization and screening of newly-developed amyloid-sensitive dyes