Daria A. Kotova

A.M. Obukhov Institute of Atmospheric Physics

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Dmitry S. Bilan

Pirogov Russian National Research Medical University

Vsevolod V. Belousov

Institute of Bioorganic Chemistry

Ilya V. Kelmanson

Institute of Bioorganic Chemistry

A. B. Fedotov

Lomonosov Moscow State University

M. S. Pochechuev

Texas A&M University

АМ

А. М. Желтиков

Texas A&M University

Alexandra D. Ivanova

Institute of Bioorganic Chemistry

Anastasiya S. Panova

Institute of Bioorganic Chemistry

AА

A. А. Lanin

Lomonosov Moscow State University

Artem S. Chebotarev

Lomonosov Moscow State University

Cooperative Institutions

Lomonosov Moscow State University

Institute of Bioorganic Chemistry

Moscow State University

Pirogov Russian National Research Medical University

Russian Academy of Sciences

Russian Quantum Center

Texas A&M University

Federal Medical-Biological Agency

University of Göttingen

Kazan State Technical University named after A. N. Tupolev

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Stain-free subcellular-resolution astrocyte imaging using third-harmonic generation

Optics Letters (2019)

M. S. Pochechuev A. А. Lanin Ilya V. Kelmanson Dmitry S. Bilan Daria A. Kotova

We demonstrate stain-free, high-contrast, subcellular-resolution imaging of astroglial cells using epi-detected third-harmonic generation (THG). The astrocyte-imaging capability of THG is verified by colocalizing THG images with fluorescence images of astrocytes expressing a genetically encodable fluorescent reporter. We show that THG imaging with an optimized point-spread function can reliably detect significant subcellular features of astrocytes, including cell nuclei, as well as the soma shape and boundaries.

Stain

Point spread function

Fluorescence-lifetime imaging microscopy

10.1364/ol.44.003166

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Citations (13)

The many faces of anti-competitive practices in digital markets

Pravovedenie (2019)

Ekaterina V. Erofeeva Daria A. Kotova Anna E. Pozdnyakova

This article looks at some curious examples of restrictive practices typical for digital markets. Digital markets are a unique phenomenon for the new digital economy that is structurally based on and driven by digital platforms. The largest digital platforms such as Facebook or Amazon and large digital companies such as Google, Microsoft and Apple dominate the digital markets of today and thus have a huge potential to restrict competition in these dynamic markets. This article takes an analytical approach to several restrictive practices that have recently received attention from competition authorities around the world and have largely influenced law enforcement as well as our understanding of how digital markets function. First of all, the authors consider the so-called price parity clauses. Broadly speaking, these are a particular type of arrangements that oblige suppliers to not offer more favorable terms to their business partners than those offered to digital platforms (for example hotel websites as compared to online booking platforms). However, when narrowed down to contractual relations between a platform and a supplier, price parity clauses present a much more complex case. Further, the authors look at the multitude of restrictive practices in the online search market illustrated by a series of cases initiated against Google by the European Commission. By setting its search engine in a particular way, Google prioritized its own services so that they received more consumer traffic. Notably, these series of cases is just a part of the collection of anticompetitive tendencies in this market. Finally, this article looks at a less well-known, but all the more dangerous case of geo-blocking, which occurs when IP-protected content is blocked from distribution outside the framework that is reasonably justified by the protection of exclusive rights. Such cases must be examined through the complex relationship between the individualistic nature of IP rights and public interest. The collection of practices examined in the article highlights both the need to significantly reform competition enforcement and the need to rethink the role of competition law in the new economy.

Competition Law

Price fixing

Digital Economy

Digital ecosystem

10.21638/spbu25.2019.404

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Citations (1)

In vivo dynamics of acidosis and oxidative stress in the acute phase of an ischemic stroke in a rodent model

Redox Biology (2021)

Ilya V. Kelmanson Arina G. Shokhina Daria A. Kotova M. S. Pochechuev Alexandra D. Ivanova

Ischemic cerebral stroke is one of the leading causes of death and disability in humans. However, molecular processes underlying the development of this pathology remain poorly understood. There are major gaps in our understanding of metabolic changes that occur in the brain tissue during the early stages of ischemia and reperfusion. In particular, it is generally accepted that both ischemia (I) and reperfusion (R) generate reactive oxygen species (ROS) that cause oxidative stress which is one of the main drivers of the pathology, although ROS generation during I/R was never demonstrated in vivo due to the lack of suitable methods. In the present study, we record for the first time the dynamics of intracellular pH and H

Rodent model

Stroke

Dynamics

10.1016/j.redox.2021.102178

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Citations (33)

Two‐ and three‐photon absorption cross‐section characterization for high‐brightness, cell‐specific multiphoton fluorescence brain imaging

Journal of Biophotonics (2019)

A. А. Lanin Artem S. Chebotarev M. S. Pochechuev Ilya V. Kelmanson Daria A. Kotova

We demonstrate an accurate quantitative characterization of absolute two- and three-photon absorption (2PA and 3PA) action cross sections of a genetically encodable fluorescent marker Sypher3s. Both 2PA and 3PA action cross sections of this marker are found to be remarkably high, enabling high-brightness, cell-specific two- and three-photon fluorescence brain imaging. Brain imaging experiments on sliced samples of rat's cortical areas are presented to demonstrate these imaging modalities. The 2PA action cross section of Sypher3s is shown to be highly sensitive to the level of pH, enabling pH measurements via a ratiometric readout of the two-photon fluorescence with two laser excitation wavelengths, thus paving the way toward fast optical pH sensing in deep-tissue experiments.

Two-photon excitation microscopy

Fluorescence-lifetime imaging microscopy

Two-Photon Absorption

Characterization

10.1002/jbio.201900243

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Citations (24)

Lipid metabolic changes in rat brain during permanent cerebral ischemia

Bulletin of Russian State Medical University (2019)

Alexander I. Kostyuk Daria A. Kotova А. Д. Демидович Anastasiya S. Panova Ilya V. Kelmanson

With each year, millions of people remain targeted by brain stroke, it still is by all means a global concern of the mankind. Despite all efforts to understand this disease better, there is still a lack of information on pathophysiology of ischemic stroke. Scrutinized data on biochemical changes at early stages of ischemia may help understand the mechanisms of the disorder and possibly reveal ways to finding the cure. The key role in the pathogenesis of stroke belongs to lipids as well as to the molecules associated with their biosynthesis and functionality. On the one hand, stroke evokes a deep oxidative stress leading to damage to biomolecules including lipids while on the other hand, due to the lack of reducing equivalents, the cellular biosynthesis processes are interrupted. The focus of this work was to study the changes taking place in the tissues of rat brain as a result of ischemia including estimation of levels of total cholesterol, FFA, MDA, GSH, and NADP(H). It was shown that in 24 hours from the onset of ischemia, there was a significant decrease in levels of FFA, total cholesterol and GSH, and an increase in the level of MDA, a marker of lipid peroxidation. NADP(H) pool level decreases twice in 6 hours from MCAO.

Stroke

Pathogenesis

Pathophysiology

Brain ischemia

Brain damage

10.24075/brsmu.2019.008

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Citations (0)

Real‐time fiber‐optic recording of acute‐ischemic‐stroke signatures

Journal of Biophotonics (2022)

M. S. Pochechuev Dmitry S. Bilan Ilya V. Fedotov Ilya V. Kelmanson Maxim A. Solotenkov

We present an experimental framework and methodology for in vivo studies on rat stroke models that enable a real-time fiber-optic recording of stroke-induced hydrogen peroxide and pH transients in ischemia-affected brain areas. Arrays of reconnectable implantable fiber probes combined with advanced optogenetic fluorescent protein sensors are shown to enable a quantitative multisite time-resolved study of oxidative-stress and acidosis buildup dynamics as the key markers, correlates and possible drivers of ischemic stroke. The fiber probes designed for this work provide a wavelength-multiplex forward-propagation channel for a spatially localized, dual-pathway excitation of genetically encoded fluorescence-protein sensors along with a back-propagation channel for the fluorescence return from optically driven fluorescence sensors. We show that the spectral analysis of the fiber-probe-collected fluorescence return provides means for a high-fidelity autofluorescence background subtraction, thus enhancing the sensitivity of real-time detection of stroke-induced transients and significantly reducing measurement uncertainties in in vivo acute-stroke studies as inherently statistical experiments operating with outcomes of multiply repeated measurements on large populations of individually variable animal stroke models.

Autofluorescence

Stroke

10.1002/jbio.202200050

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Citations (6)

Enhanced‐contrast two‐photon optogenetic pH sensing and pH‐resolved brain imaging

Journal of Biophotonics (2020)

Artem S. Chebotarev M. S. Pochechuev A. А. Lanin Ilya V. Kelmanson Daria A. Kotova

We present experiments on cell cultures and brain slices that demonstrate two-photon optogenetic pH sensing and pH-resolved brain imaging using a laser driver whose spectrum is carefully tailored to provide the maximum contrast of a ratiometric two-photon fluorescence readout from a high-brightness genetically encoded yellow-fluorescent-protein-based sensor, SypHer3s. Two spectrally isolated components of this laser field are set to induce two-photon-excited fluorescence (2PEF) by driving SypHer3s through one of two excitation pathways-via either the protonated or deprotonated states of its chromophore. With the spectrum of the laser field accurately adjusted for a maximum contrast of these two 2PEF signals, the ratio of their intensities is shown to provide a remarkably broad dynamic range for pH measurements, enabling high-contrast optogenetic deep-brain pH sensing and pH-resolved 2PEF imaging within a vast class of biological systems, ranging from cell cultures to the living brain.

Chromophore

Fluorescence-lifetime imaging microscopy

Two-photon excitation microscopy

10.1002/jbio.202000301

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Citations (7)

Single‐beam optogenetic multimodal χ⁽³⁾/χ⁽⁵⁾ nonlinear microscopy and brain imaging

Journal of Raman Spectroscopy (2020)

A. А. Lanin Artem S. Chebotarev M. S. Pochechuev Ilya V. Kelmanson Daria A. Kotova

Abstract We demonstrate single‐beam optogenetic multimodal nonlinear‐optical microscopy that combines third‐harmonic generation (THG) and three‐photon‐excited fluorescence (3PEF) – two nonlinear‐optical processes related to the third‐ and fifth‐order susceptibilities, χ (3) and χ (5) . A carefully tailored unamplified short‐pulse output of mode‐locked solid‐state lasers is shown to provide an ample parameter space for the optimization of such a single‐beam multimodal microscopy, enabling subcellular‐resolution, cell‐specific imaging using genetically encoded fluorescent‐protein‐based reporters in a vast variety of biological systems and settings, ranging from HeLa to brain cells. Experiments on brain slices and cell cultures presented in this paper demonstrate the potential of short‐pulse 3PEF/THG microscopy for a subcellular‐resolution, high‐contrast imaging of HeLa‐line cancer‐cell derivatives, as well as mitochondrial and somatic intracellular structures within deep‐brain neurons and astrocytes. As a step beyond the state of the art in optical brain imaging, single‐beam subcellular‐resolution, cell‐specific optogenetic 3PEF/THG imaging of fundamental functional brain units is experimentally demonstrated. One fundamental question that this work brings up for the future nonlinear absorption and Raman/hyper‐Raman studies is whether the Herzberg–Teller corrections, needed for an accurate description of two‐photon absorption in fluorescent proteins (FPs), would be also sufficient for an adequate treatment of higher‐ n n ‐photon absorption in FP‐based systems or models that include other quantum pathways would be necessary for the analysis of FP agents for higher‐ n nonlinear microscopy.

Two-photon excitation microscopy

Fluorescence-lifetime imaging microscopy

10.1002/jrs.5933

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Citations (4)

Multiphoton tools for hydrogen peroxide imaging in vivo with subcellular resolution

Sensors and Actuators B Chemical (2024)

Artem S. Chebotarev Ilya V. Kelmanson Alexandra D. Ivanova Yulia V. Khramova V. A. Katrukha

Autofluorescence

Two-photon excitation microscopy

Fluorescence-lifetime imaging microscopy

Temporal resolution

10.1016/j.snb.2024.135646

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Citations (3)

Which Antioxidant System Shapes Intracellular H₂O₂ Gradients?

Antioxidants and Redox Signaling (2019)

Natalia M. Mishina Yulia A. Bogdanova Yulia G. Ermakova Anastasiya S. Panova Daria A. Kotova

Cellular antioxidant systems control the levels of hydrogen peroxide (H2O2) within cells. Multiple theoretical models exist that predict the diffusion properties of H2O2 depending on the rate of H2O2 generation and amount and reaction rates of antioxidant machinery components. Despite these theoretical predictions, it has remained unknown how antioxidant systems shape intracellular H2O2 gradients. The relative role of thioredoxin (Trx) and glutathione systems in H2O2 pattern formation and maintenance is another disputed question. Here, we visualized cellular antioxidant activity and H2O2 gradients formation by exploiting chemogenetic approaches to generate compartmentalized intracellular H2O2 and using the H2O2 biosensor HyPer to analyze the resulting H2O2 distribution in specific subcellular compartments. Using human HeLa cells as a model system, we propose that the Trx system, but not the glutathione system, regulates intracellular H2O2 gradients. Antioxid. Redox Signal. 31, 664-670.

HeLa

10.1089/ars.2018.7697

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Citations (57)