Biology subjects

Maksimov, G. V.

Publications and source records attributed to Maksimov, G. V..

3 recordsLinked to original sources

bioRxiv2021

SERS uncovers the link between conformation of cytochrome c heme and mitochondrial membrane potential

The balance between the mitochondrial respiratory chain activity and the cells needs in ATP ensures optimal cellular function. Cytochrome c is an essential component of the electron transport chain (ETC), which regulates ETC activity, oxygen consumption, ATP synthesis and can initiate apoptosis. The impact of conformational changes in cytochrome c on its function is not understood for lack of access to these changes in intact mitochondria. We have developed a novel sensor that uses unique properties of label-free surface-enhanced Raman spectroscopy (SERS) to identify conformational changes in heme of cytochrome c and to elucidate their role in functioning mitochondria. We verify that molecule bond vibrations assessed by SERS is a reliable indicator of the heme conformation during changes in the inner mitochondrial membrane potential and ETC activity. We have found that cytochrome c heme reversibly switches between planar and ruffled conformations in response to the inner mitochondrial membrane potential and H+ concentration in the intermembrane space to regulate the efficiency of the mitochondrial respiratory chain, thus, adjusting the mitochondrial respiration to the cells consumption of ATP and the overall activity. The ability of the proposed SERS-based sensor to track mitochondrial function opens wide perspectives on cell bioenergetics. For Table of Contents Only O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/425119v2_ufig1.gif" ALT="Figure 1"> View larger version (66K): org.highwire.dtl.DTLVardef@eaaf42org.highwire.dtl.DTLVardef@19826f0org.highwire.dtl.DTLVardef@245e8forg.highwire.dtl.DTLVardef@1bc265d_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2020

Acetylcholine as a trigger of the somatic exocytosis in Retzius neurons

The redistribution of vesicles containing serotonin in leech neurons was studied using the fluorescent, scanning ion-conductance, and laser phase microscopy methods. During acetylcholine receptor (AChR) activation in Retzius neurons, the changes of Ca2+ desorption, cellular stiffness and the cell optical phase difference (OPD) were established. It was found that the amplitude of OPD changes in the near-membrane area (membrane and near-membrane of the cytoplasm layers) increases upon AChR activation and this is, possibly, associated with the neurons vesicle redistribution. The decrease in the cell stiffness upon AChR activation suggests the crucial role of cytoskeleton for vesicle transport and release. Ca2+ rise in the cytoplasm during AChR activation may regulate the mitochondrial recruitment to regions with high energy demand for vesicle trafficking.

neuroscience↗

bioRxiv2018

Radioprotective role of cyanobacterial phycobilisomes

It is now generally accepted that cyanobacteria are responsible for production of oxygen, which led to the so-called \"Great Oxygenation Event\". Appearance of dioxygen in Earths atmosphere resulted in formation of the ozone layer and the ionosphere, which caused significant reduction of ionizing radiation levels at the surface of our planet. This event not only increased biological diversity but also canceled the urgency of previously developed mechanisms of DNA protection, which allowed to survive and develop in harsh environmental conditions including exposure to cosmic rays. In order to test the hypothesis if one of the oldest organisms on Earth retained ancient protection mechanisms, we studied the effect of ionizing radiation (IoR, here: -particles with a kinetic energy of about 30 MeV) and space flight during the mission of the Foton-M4 satellite on cells of Synechocystis sp. PCC6803. By analyzing spectral and functional characteristics of photosynthetic membranes we revealed numerous similarities between cells exposed to IoR and after the space mission. In both cases, we found that excitation energy transfer from phycobilisomes to photosystems was interrupted and the concentration of phycobiliproteins was significantly reduced. Although photosynthetic activity was severely suppressed, the effect was reversible and the cells were able to rapidly recover from stress under normal conditions. Moreover, in vitro experiments demonstrated that the effect of IoR on isolated phycobilisomes was completely different from such in vivo. These observations suggest that the actual existence and the uncoupling of phycobilisomes under irradiation stress could play specific role not only in photo-, but also in radioprotection, which was crucial for early stages of evolution and the development of Life on Earth.

biophysics↗