vestnik-bio-msuВестник Московского университета. Серия 16. БиологияVestnik Moskovskogo universiteta. Seriya 16. Biologiya0137-0952Lomonosov Moscow State University, School of Biologyvestnik-bio-msu-1055Research ArticleОРИГИНАЛЬНОЕ ИССЛЕДОВАНИЕRESEARCH ARTICLEОсобенности использования 2,6-дихлорофенолиндофенола в качестве акцептора электронов в исследованиях фотосинтезаFeatures of using 2,6-dichlorophenolindophenol as an electron acceptor in photosynthesis studieshttps://orcid.org/0000-0002-9082-1966ЛоктюшкинА. В.LoktyushkinA. V.

Локтюшкин Алексей Владимирович – канд. биол. наук, ст. преподаватель кафедры биофизики биологического факультета

119234, г. Москва, Ленинские горы, д. 1, стр. 12

Тел.: 8-495-939-33-15

Department of Biophysics, School of Biology

Leninskiye gory 1–12, Moscow 119234

allokt@gmail.comhttps://orcid.org/0000-0002-3586-0575ЛовягинаЕ. Р.LovyaginaE. R.

Ловягина Елена Рудольфовна – канд. биол. наук, ст. науч. сотр. кафедры биофизики биологического факультета

119234, г. Москва, Ленинские горы, д. 1, стр. 12

Тел.: 8-495-939-33-15

Department of Biophysics, School of Biology

Leninskiye gory 1–12, Moscow 119234

elena.lovyagina@gmail.comhttps://orcid.org/0000-0002-0058-2798СеминБ. К.SeminB. K.

Семин Борис Константинович – докт. биол. наук, вед. науч. сотр. кафедры биофизики биологического факультета

119234, г. Москва, Ленинские горы, д. 1, стр. 12

Тел.: 8-495-939-33-15

Department of Biophysics, School of Biology

Leninskiye gory 1–12, Moscow 119234

semin@biophys.msu.ruМосковский государственный университет имени М.В. ЛомоносоваРоссияLomonosov Moscow State UniversityRussian Federation202101122021764234240Copyright © Локтюшкин А.В., Ловягина Е.Р., Семин Б.К., 20212021Локтюшкин А.В., Ловягина Е.Р., Семин Б.К.Loktyushkin A.V., Lovyagina E.R., Semin B.K.Данная работа распространяется под лицензией Creative Commons Attribution 4.0.This work is licensed under a Creative Commons Attribution 4.0 License.https://vestnik-bio-msu.elpub.ru/jour/article/view/1055

2,6-дихлорофенолиндофенол (ДХФИФ) – редокс-индикатор, широко используемый для исследования реакций переноса электрона в биологических системах, в том числе в процессе фотосинтеза. При восстановлении ДХФИФ, поглощающий свет в видимой области, обесцвечивается. ДХФИФ существует в растворе в двух формах – «розовой» и «синей», которые переходят друг в друга при протонировании/депротонировании. Нами исследована рН-зависимость скорости восстановления ДХФИФ фотосистемой 2 (ФС2) при двух длинах волн – 522 нм (изобестическая точка ДХФИФ) и 600 нм (вблизи максимума поглощения депротонированной «синей» формы). Показано, что при изменении рН среды измерения на длине волны 600 нм требуют внесения поправок, связанных с изменением соотношения «синей» и «розовой» форм акцептора, а также использования для расчета скорости восстановления ДХФИФ параметра рК этого акцептора, значения которого варьируют в различных источниках. Измерения в изобестической точке (522 нм) позволяют избежать этих сложностей. Также нами установлено, что максимум на рН-зависимости скорости восстановления ДХФИФ ФС2 сдвинут примерно на одну единицу в кислую область относительно максимума рН-зависимости скорости восстановления акцепторной пары 2,6-дихлоро-п-бензохинон – феррицианид калия. Этот сдвиг может быть связан с меньшей доступностью QB-сайта на акцепторной стороне ФС2 для заряженной депротонированной формы ДХФИФ по сравнению с незаряженной протонированной формой.

2,6-dichlorophenolindophenol (DCPIP) is a redox indicator widely used to study electron transfer reactions in biological systems, including in the process of photosynthesis. DCPIP exists in solution in two forms – “pink” and “blue,” which transform into each other during protonation/deprotonation. Upon reduction, the DCPIP is discolored. We investigated the pH-dependence of DCPIP reduction rate in the presence of the photosystem II (PSII) at two wavelengths – 522 nm (isobestic DCPIP point) and 600 nm (near the absorption maximum of the deprotonated “blue” form). It was shown that in experiments with change of the pH medium, measuring at a wavelength of 600 nm requires corrections related to changing the ratio of the “blue” and “pink” forms of the acceptor, as well as using the pK parameter of this acceptor, whose values рК vary in various sources, to calculate the DCPIP reduction rate. Measurements at the isobestic point (522 nm) avoid these complexities. We also found that the maximum at the pH-dependence of the DCPIP reduction rate by PSII shifted by about 1 unit to the acidic region relative to the maximum of the acceptor pair 2,6-dichloro-p-benzoquinone – potassium ferricyanide reduction rate pH-dependence. This shift may be due to the lower availability of the QB site on the acceptor side PSII for the charged deprotonated DCPIP form compared to the uncharged protonated form.

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The authors declare that there are no conflicts of interest present.