The Valence and Spin State Tuning of Iron(II/III) Porphyrazines with Bulky Pyrrolyl Periphery in Solution and Solid State.

Iron(III) porphyrazines containing peripheral 2,5-dimethyl-, 2-methyl-5-phenyl-, and 2,3,5-triphenyl-1H-pyrrol-1-yl substituents were synthesized and subjected to physicochemical characterization. This was accomplished by high-resolution mass spectrometry, nuclear magnetic resonance (as diamagnetic Fe(II) derivatives), HPLC purity analysis, and UV-Vis spectroscopy, accompanied by the solvation study in dichloromethane and pyridine. X-ray structure analysis was performed for a single crystal of the previously obtained 2,5-diphenyl-substituted derivative of porphyrazine complex (5d). The octahedral geometries of iron cation, present in the porphyrazine core, influenced the packing mode of molecules in the crystals. Mössbauer studies, performed for solid samples of iron porphyrazines, indicated that low-spin reduced iron states might occupy low- or high-symmetry binding sites. It was found that the hyperfine parameters and the subsequent contribution of the iron cations depend on the number of phenyl groups surrounding the pyrrolyl moiety. For iron(II) porphyrazine 2,3,5-triphenylpyrrol-1-yl substituents (5b), a high-spin ferrous state fraction was observed. Temperature-dependent measurements showed that the freed rotation of the peripheral porphyrazine ligands and the increased flexibility of the macrocycle ring result in the Fe2+ ion being stabilized in a diamagnetic state at a binding site of high symmetry at room temperature in the solid state. This process is most probably stimulated by the range of collective motions of the polymeric ribbons consisting of iron(II) porphyrazines observed in the X-ray.

Effect of Grinding and the Mill Type on Magnetic Properties of Carboxylated Multiwall Carbon Nanotubes.

The influence of the grinding process on the magnetic properties of as prepared and functionalized multiwall carbon nanotubes (MWCNTs) is presented. We have observed that 3 h mechanical grinding at 400 rpm in contrast to functionalization does not remove the iron contamination from MWCNTs. However, it changes the Fe chemical states. The magnetic properties of iron nanoparticles (Fe-NPs) embedded in the carbon matrix of MWCNTs have been analyzed in detail. We have proven that single-domain non-interacting Fe(C,O)-NPs enriched in the Fe3C phase (~10 nm) enclosed inside these nanotubes are responsible for their magnetic properties. Mechanical grinding revealed a unique impact of -COOH groups (compared to -COONH4 groups) on the magnetism of functionalized MWCNTs. In MWCNT-COOH ground in a steel mill, the contribution of the Fe2O3 and α-Fe phases increased while the content of the magnetically harder Fe3C phase decreased. This resulted in a 2-fold coercivity (Hc) decrease and saturation magnetization (MS) increase. A 2-fold remanence (Mr) decrease in MWCNT-COOH ground in an agate mill is related to the modified Fe(C,O)-NP magnetization dynamics. Comparison of the magnetostatic exchange and effective anisotropy length estimated for Fe(C,O)-NPs allows concluding that the anisotropy energy barrier is higher than the magnetostatic energy barrier. The enhanced contribution of surface anisotropy to the effective anisotropy constant and the unique effect of the -COOH groups on the magnetic properties of MWCNTs are discussed. The procedure for grinding carboxylated MWCNTs with embedded iron nanoparticles using a steel mill has a potential application for producing Fe-C nanocomposites with desired magnetic properties.

ß-Carotene-Induced Alterations in Haemoglobin Affinity to O2.

ß-Carotene (ß-Crt) can be dispersed in hydrophobic regions of the membrane of red blood cells (RBC). Its location, orientation and distribution strongly depend on carotenoid concentration. In the present pilot trial (six human subjects involved), it is demonstrated that incubation of RBCs with ß-Crt (1.8 × 107 ß-Crt molecules per RBC, 50 µmol/L) results in expansion of the membrane of RBCs and slight elongation of the cell. The changes are of statistical significance, as verified by the Wilcoxon test at p < 0.05. They indicate (i) a highly random orientation and location of ß-Crt inside the membrane and (ii) a tendency for its interaction with membrane skeleton proteins. The accompanying effect of decreased RBC resistance to lysis is possibly a result of the incorrect functioning of ion channels due to their modification/disruption. At higher ß-Crt concentrations, its clustering inside membranes may occur, leading to further alterations in the shape and size of RBCs, with the most pronounced changes observed at 1.8 × 108 ß-Crt molecules per RBC (500 µmol/L). Due to the reduced permeability of ions, such membranes exhibit increased resistance to haemolysis. Finally, we show that interactions of ß-Crt with the membrane of RBCs lead to an alteration in haemoglobin-oxygen affinity, shifting the oxyhaemoglobin dissociation curve toward higher oxygen partial pressures. If the impact of ß-Crt on a curve course is confirmed in vivo, one may consider its role in the fine tuning of O2 transportation to tissues. Hence, at low concentrations, providing unchanged elastic and functional properties of RBCs, it could serve as a beneficial agent in optimising heart performance and cardiovascular load.

The xanthophyll cycle in diatom Phaeodactylum tricornutum in response to light stress.

Chosen aspects of the functioning of diadinoxanthin cycle in a model diatom Phaeodactylum tricornutum grown under low light conditions (LL) and under high light conditions (HL), which cause activation of violaxanthin cycle, were examined. Heterogeneity of the kinetics of diadinoxanthin ↔ diatoxanthin conversions regulated by de-epoxidase/epoxidase enzymes was detected. Three different rates of diadinoxanthin de-epoxidation (τ > 20 min, 5 min > τ > 1.5 min and τ ≤ 1 min) were observed. Appearance and contribution of these phases depended on the light conditions and xanthophylls subpopulations in membranes. Moreover, diadinoxanthin de-epoxidation was postulated to occur in darkness and its rate was estimated to be almost two times faster (τ ≈ 14 min) than diatoxanthin-epoxidation in LL- and HL-grown diatoms collected after the dark phase of the photoperiod and exposed to very high light and subsequent darkness. The level of lipid hydroperoxides and the expression of genes encoding xanthophyll cycle enzymes was measured. Our observations suggest that isoforms of these enzymes may participate in carotenoid synthesis or be exclusively involved in xanthophyll conversions. Violaxanthin cycle pigments present in HL-acclimated diatoms change thermodynamic properties of thylakoid membranes. Zeaxanthin is known to localize preferentially in the inner part of the lipid bilayer and diatoxanthin in its outer part. The different localization of these pigments probably decide about their complementary action in protection of the membranes against reactive oxygen species.

The influence of very small doses of alpha radiation on the stability of erythrocytes.

Our aim was to study the influence of low doses (0.2-4 µGy) of α radiation on the stability of human erythrocytes isolated from healthy and diabetic erythrocytes. Absorption spectroscopy was used to measure the level of red blood cell (RBC) hemolysis, along with Mössbauer spectroscopy, which is a highly specific method suited to monitoring various hemoglobin forms. States of hemoglobin are sensitive to a homeostatic imbalance in red blood cells. Changes in the membrane skeleton organization of irradiated erythrocytes isolated from healthy donors were studied using atomic force microscopy (AFM). Hemolysis, in healthy red blood cells, showed characteristic discontinuities, depending on the α particle flux and the exposure time to the low doses applied. This phenomenon was not observed in severe diabetic cases, which could be a result of modified protein-lipid-sugar complexes and the attenuation/absence of some antioxidative enzymatic processes in their RBC membranes. Similar effects were also observed for red blood cells treated with low doses of neutron and γ-radiation. AFM measurements demonstrated a reorganization of the RBC membrane skeleton network depending on the time of RBC exposure to α radiation. This suggests that the changes in the activity of the acute defense processes against free radicals which are activated within the erythrocyte membrane irradiated with α-particles could additionally be up- or down regulated by modifications to the membrane-skeleton network. However, even the highest dose of α radiation applied in these studies did not cause any significant changes in the ability of hemoglobin to transport oxygen. Microsc. Res. Tech. 80:131-143, 2017. © 2016 Wiley Periodicals, Inc.

Oxidative insult can induce malaria-protective trait of sickle and fetal erythrocytes.

Plasmodium falciparum infections can cause severe malaria, but not every infected person develops life-threatening complications. In particular, carriers of the structural haemoglobinopathies S and C and infants are protected from severe disease. Protection is associated with impaired parasite-induced host actin reorganization, required for vesicular trafficking of parasite-encoded adhesins, and reduced cytoadherence of parasitized erythrocytes in the microvasculature. Here we show that aberrant host actin remodelling and the ensuing reduced cytoadherence result from a redox imbalance inherent to haemoglobinopathic and fetal erythrocytes. We further show that a transient oxidative insult to wild-type erythrocytes before infection with P. falciparum induces the phenotypic features associated with the protective trait of haemoglobinopathic and fetal erythrocytes. Moreover, pretreatment of mice with the pro-oxidative nutritional supplement menadione mitigate the development of experimental cerebral malaria. Our results identify redox imbalance as a causative principle of protection from severe malaria, which might inspire host-directed intervention strategies.

Titanium dioxide nanoparticles (100-1000 mg/l) can affect vitamin E response in Arabidopsis thaliana.

In the present study we analyze the effect of seed treatment by a range of nano-TiO2 concentrations on the growth of Arabidopsis thaliana plants, on the vitamin E content and the expression of its biosynthetic genes, as well as activity of antioxidant enzymes and lipid peroxidation. To conduct the mechanistic analysis of nano-TiO2 on plants growth and antioxidant status we applied nanoparticles concentrations that are much higher than those reported in the environment. We find that as the concentration of nano-TiO2 increases, the biomass, and chlorophyll content in 5-week-old Arabidopsis thaliana plants decrease in a concentration dependent manner. In opposite, higher nano-TiO2 concentration enhanced root growth. Our results indicate that a high concentration of nano-TiO2 induces symptoms of toxicity and elevates the antioxidant level. We also find that the expression levels of tocopherol biosynthetic genes were either down- or upregulated in response to nano-TiO2. Thermoluminescence analysis shows that higher nano-TiO2 concentrations cause lipid peroxidation. To the best of our knowledge, this is the first report concerning the effect of nano-TiO2 on vitamin E status in plants. We conclude that nano-TiO2 affects the antioxidant response in Arabidopsis thaliana plants. This could be an effect of a changes in vitamin E gene expression that is diminished under lower tested nano-TiO2 concentrations and elevated under 1000 µg/ml.

Influence of polar and nonpolar carotenoids on structural and adhesive properties of model membranes.

Carotenoids, which are known primarily for their photoprotective and antioxidant properties, may also strongly influence the physical properties of membranes. The localization and orientation of these pigments in the lipid bilayer depends on their structure and is determined by their interactions with lipid molecules. This affects both phase behavior and the mechanical properties of membranes. Differential scanning calorimetry (DSC) and atomic force microscopy (AFM) allowed us to gain a direct insight into the differences between the interaction of the non-polar ß-carotene and polar zeaxanthin embedded into DPPC liposomes. DSC results showed that zeaxanthin, having polar ionone rings, interacts more strongly with the membrane lipids than ß-carotene. The decrease in molar heat capacity by a factor of 2 with a simultaneous broadening of the main phase transition (gel-to-liquid crystalline phase transition) as compared to the two other systems studied suggests some increased length of the coupled interactions between the polar xanthophyll and lipids. Long-distance interactions lead to the formation of larger clusters which may exhibit higher flexibility than small clusters when only short-distance interactions occur. AFM experiments show that adhesive forces are 2 and 10 times higher for DPPC membranes enriched in ß-carotene and zeaxanthin, respectively, than those observed for an untreated system. Temperature dependent measurements of adhesion revealed that subphases can be formed in the gel lamellar state of DPPC bilayers. The presence of the non-polar carotenoid enhanced the effect and even a bifurcation of the substates was detected within a temperature range of 30.0-32.5°C prior to pretransition. It is the first time when the presence of subphases has been demonstrated. This knowledge can be helpful in better understanding the functioning of carotenoids in biological membranes. AFM seem to be a very unique and sensitive method for detecting such fine changes in the lipid bilayers.

Undifferentiated bronchial fibroblasts derived from asthmatic patients display higher elastic modulus than their non-asthmatic counterparts.

During asthma development, differentiation of epithelial cells and fibroblasts towards the contractile phenotype is associated with bronchial wall remodeling and airway constriction. Pathological fibroblast-to-myofibroblast transition (FMT) can be triggered by local inflammation of bronchial walls. Recently, we have demonstrated that human bronchial fibroblasts (HBFs) derived from asthmatic patients display some inherent features which facilitate their FMT in vitro. In spite of intensive research efforts, these properties remain unknown. Importantly, the role of undifferentiated HBFs in the asthmatic process was systematically omitted. Specifically, biomechanical properties of undifferentiated HBFs have not been considered in either FMT or airway remodeling in vivo. Here, we combine atomic force spectroscopy with fluorescence microscopy to compare mechanical properties and actin cytoskeleton architecture of HBFs derived from asthmatic patients and non-asthmatic donors. Our results demonstrate that asthmatic HBFs form thick and aligned 'ventral' stress fibers accompanied by enlarged focal adhesions. The differences in cytoskeleton architecture between asthmatic and non-asthmatic cells correlate with higher elastic modulus of asthmatic HBFs and their increased predilection to TGF-ß-induced FMT. Due to the obvious links between cytoskeleton architecture and mechanical equilibrium, our observations indicate that HBFs derived from asthmatic bronchi can develop considerably higher static tension than non-asthmatic HBFs. This previously unexplored property of asthmatic HBFs may be potentially important for their myofibroblastic differentiation and bronchial wall remodeling during asthma development.

Effect of functionalized and non-functionalized nanodiamond on the morphology and activities of antioxidant enzymes of lung epithelial cells (A549).

The development of nanotechnology opens up new ways for biomedical applications of unmodified and modified diamond nanoparticles which are one of the most popular nanomaterials used in biology, biotechnology, medicine, cosmetics and engineering. They have been applied as diagnostic and therapeutic agents because they can be targeted to and localized in cells causing apoptosis and necrosis. The problem of biocompatibility of nanodiamonds at higher concentrations is thus of primary importance. The first step in the modification of DNPs is usually the introduction of hydrogen groups, which can bind other functional groups. The basic method to introduce -OH groups onto nanoparticles is the Fenton reaction. The aim of this study was to compare the effect of unmodified nanodiamond particles and nanoparticles modified by introduction of -OH groups and etoposide onto their surface reaction on human non-small lung cancer cells. A549 cells were incubated with 2-100µg/ml nanopowders and at 0.6-24µg/ml etoposide in the DMEM medium. We observed a decrease of cells viability and generation of reactive oxygen/ nitrogen species in the cells after incubation, estimated by oxidation of H2DCF-DA and DAF-FM-DA. Modified detonation nanoparticles affected also the cellular content of glutathione and activities of main antioxidant enzymes (glutathione peroxidase, glutathione reductase, glutathione S-transferase, superoxide dismutase and catalase). The results of TEM microscopy show changes in cell morphology. These data demonstrate that modified nanoparticles induce oxidative stress in the target cells.

Cell elasticity is an important indicator of the metastatic phenotype of melanoma cells.

The relationship between melanin pigmentation and metastatic phenotype of melanoma cells is an intricate issue, which needs to be unambiguously determined to fully understand the process of metastasis of malignant melanoma. Despite significant research efforts undertaken to solve this problem, the outcomes are far from being satisfying. Importantly, none of the proposed explanations takes into consideration biophysical aspects of the phenomenon such as cell elasticity. Recently, we have demonstrated that melanin granules dramatically modify elastic properties of pigmented melanoma cells. This prompted us to examine the mechanical effects of melanosomes on the transmigration abilities of melanoma cells. Here, we show for the first time that melanin granules inhibit transmigration abilities of melanoma cells in a number of granules dependent manner. Moreover, we demonstrate that the inhibitory effect of melanosomes is mechanical in nature. Results obtained in this study demonstrate that cell elasticity may play a key role in the efficiency of melanoma cells spread in vivo. Our findings may also contribute to better understanding of the process of metastasis of malignant melanoma.

AtomicJ: an open source software for analysis of force curves.

We present an open source Java application for analysis of force curves and images recorded with the Atomic Force Microscope. AtomicJ supports a wide range of contact mechanics models and implements procedures that reduce the influence of deviations from the contact model. It generates maps of mechanical properties, including maps of Young's modulus, adhesion force, and sample height. It can also calculate stacks, which reveal how sample's response to deformation changes with indentation depth. AtomicJ analyzes force curves concurrently on multiple threads, which allows for high speed of analysis. It runs on all popular operating systems, including Windows, Linux, and Macintosh.

Functional links between Snail-1 and Cx43 account for the recruitment of Cx43-positive cells into the invasive front of prostate cancer.

Suppressive function of connexin(Cx)43 in carcinogenesis was recently contested by reports that showed a multifaceted function of Cx43 in cancer progression. These studies did not attempt to model the dynamics of intratumoral heterogeneity involved in the metastatic cascade. An unorthodox look at the phenotypic heterogeneity of prostate cancer cells in vitro enabled us to identify links between Cx43 functions and Snail-1-regulated functional speciation of invasive cells. Incomplete Snail-1-dependent phenotypic shifts accounted for the formation of phenotypically stable subclones of AT-2 cells. These subclones showed diverse predilection for invasive behavior. High Snail-1 and Cx43 levels accompanied high motility and nanomechanical elasticity of the fibroblastoid AT-2_Fi2 subclone, which determined its considerable invasiveness. Transforming growth factor-ß and ectopic Snail-1 overexpression induced invasiveness and Cx43 expression in epithelioid AT-2 subclones and DU-145 cells. Functional links between Snail-1 function and Cx43 expression were confirmed by Cx43 downregulation and phenotypic shifts in AT-2_Fi2, DU-145 and MAT-LyLu cells upon Snail-1 silencing. Corresponding morphological changes and Snail-1 downregulation were seen upon Cx43 silencing in AT-2_Fi2 cells. This indicates that feedback loops between both proteins regulate cell invasive behavior. We demonstrate that Cx43 may differentially predispose prostate cancer cells for invasion in a coupling-dependent and coupling-independent manner. When extrapolated to in vivo conditions, these data show the complexity of Cx43 functions during the metastatic cascade of prostate cancer. They may explain how Cx43 confers a selective advantage during cooperative invasion of clonally evolving, invasive prostate cancer cell subpopulations.

Potential role of carotenoids as antioxidants in human health and disease.

Carotenoids constitute a ubiquitous group of isoprenoid pigments. They are very efficient physical quenchers of singlet oxygen and scavengers of other reactive oxygen species. Carotenoids can also act as chemical quenchers undergoing irreversible oxygenation. The molecular mechanisms underlying these reactions are still not fully understood, especially in the context of the anti- and pro-oxidant activity of carotenoids, which, although not synthesized by humans and animals, are also present in their blood and tissues, contributing to a number of biochemical processes. The antioxidant potential of carotenoids is of particular significance to human health, due to the fact that losing antioxidant-reactive oxygen species balance results in "oxidative stress", a critical factor of the pathogenic processes of various chronic disorders. Data coming from epidemiological studies and clinical trials strongly support the observation that adequate carotenoid supplementation may significantly reduce the risk of several disorders mediated by reactive oxygen species. Here, we would like to highlight the beneficial (protective) effects of dietary carotenoid intake in exemplary widespread modern civilization diseases, i.e., cancer, cardiovascular or photosensitivity disorders, in the context of carotenoids' unique antioxidative properties.

Erythrocyte membrane properties in patients with essential hypertension.

In spite of the extensive research efforts that have been conducted over the last decades, it is still very difficult to point out genetic determinants or environmental conditions responsible for the development of essential hypertension. We searched for differences in the RBC membrane skeleton structure and O2 membrane permeability between RBCs from patients with both essential arterial hypertension and hypercholesterolemia, from patients having only hypercholesterolemia and from healthy donors. The topography of RBCs and the content of various hemoglobin forms were detected using atomic force microscopy and Mössbauer spectroscopy, respectively. We found that the membrane skeleton of RBCs from healthy donors displayed a well-known honeycomb pattern, whereas in patients with essential hypertension and/or hypercholesterolemia, who had never received anti-hypertensive therapy, it displayed a corncob pattern. Hypertensive RBCs had an oval shape and the average lateral to longitudinal diameter ratio for the changed cells (about 70%) did not exceed 0.80. We observed that after the incubation of RBCs under high nitrogen (low O2) pressure at room temperature and then their transfer into 85 K, a content of oxyHb (deoxyHbOH) already after 1 h reached a stable level of about 85 ± 3% (15 ± 3%) in hypertensives, whereas in healthy individuals it showed a decrease for deoxyHbOH and an increase for oxyHb, which stabilized at a level of about 81 ± 5% and 19 ± 5%, respectively, only after 9 h. Quantitative analysis of the Δ(oxyHb) change estimated as the difference between the oxyHb level measured after 9 and 2 h at 85 K under low N2 pressure (to slow down oxyHb formation) was significantly higher in normotensives than in hypertensive patients with or without hypercholesterolemia, 19.9 versus -4.2, p < 0.02. Our findings indicate an impaired oxygen release by Hb in RBCs of patients with hypertension under low oxygen pressure which if present in vivo may cause hypoxemia and, in turn, further increase of blood pressure.

Nanomechanical analysis of pigmented human melanoma cells.

Based on hitherto measurements of elasticity of various cells in vitro and ex vivo, cancer cells are generally believed to be much softer than their normal counterparts. In spite of significant research efforts on the elasticity of cancer cells, only few studies were undertaken with melanoma cells. However, there are no reports concerning pigmented melanoma cells. Here, we report for the first time on the elasticity of pigmented human melanoma cells. The obtained data show that melanin significantly increases the stiffness of pigmented melanoma cells and that the effect depends on the amount of melanin inside the cells. The dramatic impact of melanin on the nanomechanical properties of cells puts into question widely accepted paradigm about all cancer cells being softer than their normal counterparts. Our findings reveal significant limitations of the nanodiagnosis approach for melanoma and contribute to better understanding of cell elasticity.

Antioxidant effects of carotenoids in a model pigment-protein complex.

The effect of carotenoids on stability of model photosynthetic pigment-protein complexes subjected to chemical oxidation with hydrogen peroxide or potassium ferricyanide was investigated. The oxidation of carotenoid-less and carotenoid-containing complexes was conducted in the presence or absence of ascorbic acid. The progress of the reactions was monitored by use of absorption and fluorescence spectroscopy. Our results show that carotenoids may significantly enhance the stability of photosynthetic complexes against oxidation and their protective (antioxidant) effect depends on the type of the oxidant.

Atomic force microscopy studies of the adhesive properties of DPPC vesicles containing ß-carotene.

A role of carotenoids as modulators of physical properties of model and biological membranes has been already postulated. However, there is a lack of information on the influence of these pigments on interactions between the lipids which form such membranes. This paper applies atomic force microscopy (AFM) in to study the effects of ß-carotene on the adhesion properties of DPPC multilamellar liposomes. This allowed us to gain, for the first time, a direct insight into the interactions between the components in model systems on a molecular level. We observe that the adhesive forces in DPPC multilamellar liposomes containing 1mol% of ß-carotene decrease exponentially with increasing temperature, and that at about 37°C they diminish. In the case of pure liposomes the decline in adhesion is of a different nature and the adhesive forces disappear at 34°C. The adhesive forces are about 5 times higher at 31°C in the presence of ß-carotene than in its absence. However, measurements using differential scanning calorimetry (DSC) showed a shift of the lamellar-to-undulled-lamellar phase transition toward lower temperatures by about 0.8 ± 0.2°C in a system containing ß-carotene. The enthalpy changes (ΔH) of this transition are similar for both systems. For the main transition, gel-to-liquid crystalline, the peak is shifted by about 0.5 ± 0.1°C, and ΔH decreases by about 30% in liposomes treated with ß-carotene in comparison to pure liposomes. Our results suggest increased cooperation between liposome components in a system with enriched ß-carotene, which cause a change in phase transition temperatures. Moreover, these interactions are very sensitive to temperature.

Effects of low doses of gamma rays on the stability of normal and diabetic erythrocytes.

We studied the influence of low doses of γ radiation (from 0.04 to 1.8 mGy) on the stability of human red blood cells (RBC) from healthy donors and diabetic patients using absorption spectroscopy. Because of the alteration of many enzymatic pathways in diabetic RBCs resulting in strong modification of the lipid and protein membrane components one could expect that the ionizing γ-radiation should influence the stability of the healthy and diabetic cells in a different way. Indeed, distinct discontinuities and monotonic changes of hemolysis detected in the healthy and diabetic RBCs suggest that various enzymatic and chemical processes are activated in these membranes by γ radiation. Mössbauer measurements showed that only the highest applied dose of γ radiation caused modification of hemoglobin in both types of RBCs.

Dynamics of electron transfer in photosystem II.

Photosystem II, being a constituent of light driven photosynthetic apparatus, is a highly organized pigment-protein-lipid complex. The arrangement of PSII active redox cofactors insures efficiency of electron transfer within it. Donation of electrons extracted from water by the oxygen evolving complex to plastoquinones requires an additional activation energy. In this paper we present theoretical discussion of the anharmonic fluctuations of the protein-lipid matrix of PSII and an experimental evidence showing that the fluctuations are responsible for coupling of its donor and acceptor side. We argue that the fast collective motions liberated at temperatures higher that 200 K are crucial for the two final steps of the water splitting cycle and that one can distinguish three different dynamic regimes of PSII action which are controlled by the timescales of forward electron transfer, which vary with temperature. The three regimes of the dynamical behavior are related to different spatial domains of PSII.