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Copyright of Studia Poliana is the property of Studia Poliana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work we deny the validity of the following modern notions accepted like "transcendentals": equality, totality, reason, memory, will, movement, time, world, subject, saying and fact. On the other hand, we defend the validity of three transcendental notions that some modern thinkers have accepted: the being, the truth and the good. [ABSTRACT FROM AUTHOR]

The effects of D1-V185T and D1-V185N mutations in Photosystem II (PSII) from Thermosynechococcus vestitus (formerly T. elongatus) and Synechocystis 6803, respectively, were studied using both EPR and optical kinetics. EPR spectroscopy reveals the presence of a mixture of a S 2 state in a high spin configuration (S 2 HS ) and in a low spin configuration (S 2 LS ) in both mutants. In contrast to the S 2 HS in the wild type, the S 2 HS state in the D1-V185T mutant does not progress to the S 3 state at 198 K. This inability is likely due to alterations in the protonation state and hydrogen-bonding network around the Mn 4 CaO 5 cluster. Optical studies show that these mutations significantly affect proton release during the S 3 -to-S 0 transition. While the initial fast proton release associated with Tyr Z ● formation remains unaffected within the resolution of our measurements, the second, and slower, proton release is delayed, suggesting that the mutations disrupt the hydrogen-bonding interactions necessary for efficient deprotonation of substrate water (O6). This disruption in proton transfer also correlates with slower water exchange in the S 3 state, likely due to non-native hydrogen bonds introduced by the threonine or asparagine side chains at position 185. These findings point to a critical role of D1-V185 in regulating both proton transfer dynamics and water binding, underscoring a complex interplay between structural and functional changes in PSII., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

An absorption change responding to the change in the trans-thylakoid electric field (Δψ), also known as the electrochromic shift (ECS) signal, is widely used to probe multiple photosynthetic processes. The ECS signals either display a linear response of absorption changes to Δψ, independent of the trans-thylakoid electric field preexisting before actinic light (ψ O ), or a quadratic response, dependent on ψ O . In the acidothermophilic red algae Cyanidioschyzon merolae and Galdieria partita, the absorption changes induced by single turnover saturating light flashes were affected by external pH. The effects of elevated external pH on the flash-induced absorption changes were explained by diminished ψ O , as shown with the treatment of ionophores. We identified three contributions to the absorption changes: c-type cytochrome oxidized-minus-reduced signal and ECS signals showing both ψ O -dependent and ψ O -independent responses. Based on this, we could reveal that the effects of elevated external pH on the flash-induced absorption changes were due to variations of ψ O , which in turn changed the contribution of the ψ O -dependent ECS, as shown with the treatment of ionophores. Further analysis revealed that the ψ O -dependent ECS signal exhibited a quadratic response to Δψ at low ψ O , but the quadraticity was lost at higher ψ O , providing insights for comprehending the atypical nature of the ECS signal. Our approach to identifying the ψ O -dependent and ψ O -independent ECS signals enables the ECS-based measurements for further investigation of the bioenergetics of electron and proton transport in red algae., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Han-Yi Fu reports financial support was provided by National Science and Technology Council, Taiwan. Han-Yi Fu reports financial support was provided by Ministry of Education, Taiwan. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

The active site for water oxidation in photosystem II (PSII) comprises a Mn 4 CaO 5 cluster adjacent to a redox-active tyrosine residue (Tyr Z ). During the water-splitting process, the enzyme transitions through five sequential oxidation states (S 0 to S 4 ), with O 2 evolution occurring during the S 3 Tyr Z · to S 0 Tyr Z transition. Chloride also plays a role in this mechanism. Using PSII from Thermosynechococcus vestitus, where Ca and Cl were replaced with Sr and Br to slow the S 3 Tyr Z · to S 0 Tyr Z  + O 2 transition (t 1/2  ~ 5 ms at room temperature), it was observed that the recovery of a S 0 state, defined as the state able to progress to S 1 , exhibits similar kinetics (t 1/2  ~ 5 ms). This suggests that in CaCl-PSII, the reformation of the functional S 0 state directly follows the S 3 Tyr Z · to S 0 Tyr Z  + O 2 transition, with no additional delay required for the insertion of a new substrate water molecule (O5) and associated protons., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s), under exclusive licence to Springer Nature B.V.)

Aquatic life is strongly structured by the distribution of light, which, besides attenuation in intensity, exhibits a continuous change in the spectrum with depth 1 . The extent to which these light changes are perceived by phytoplankton through photoreceptors is still inadequately known. We addressed this issue by integrating functional studies of diatom phytochrome (DPH) photoreceptors in model species 2 with environmental surveys of their distribution and activity. Here, by developing an in vivo dose-response assay to light spectral variations mediated by DPH, we show that DPH can trigger photoreversible responses across the entire light spectrum, resulting in a change in DPH photoequilibrium with depth. By generating dph mutants in the diatom Thalassiosira pseudonana, we also demonstrate that under simulated low-blue-light conditions of ocean depth, DPH regulates photosynthesis acclimation, thus linking optical depth detection with a functional response. The latitudinal distribution of DPH-containing diatoms from permanently stratified regions to seasonally mixed regions suggests an adaptive value of DPH functions in coping with vertical displacements in the water column. By establishing DPH as a detector of optical depth, this study provides a new view of how information embedded in the underwater light field can be exploited by diatoms to modulate their physiology throughout the photic zone., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Flash-induced absorption changes in the Soret region arising from the [P D1 P D2 ] + state, the chlorophyll cation radical formed upon light excitation of Photosystem II (PSII), were measured in Mn-depleted PSII cores at pH 8.6. Under these conditions, Tyr D is i) reduced before the first flash, and ii) oxidized before subsequent flashes. In wild-type PSII, when Tyr D ● is present, an additional signal in the [P D1 P D2 ] + -minus-[P D1 P D2 ] difference spectrum was observed when compared to the first flash when Tyr D is not oxidized. The additional feature was "W-shaped" with troughs at 434 nm and 446 nm. This feature was absent when Tyr D was reduced, but was present (i) when Tyr D was physically absent (and replaced by phenylalanine) or (ii) when its H-bonding histidine (D2-His189) was physically absent (replaced by a Leucine). Thus, the simple difference spectrum without the double trough feature at 434 nm and 446 nm, seemed to require the native structural environment around the reduced Tyr D and its H bonding partners to be present. We found no evidence of involvement of P D1 , Chl D1 , Phe D1 , Phe D2 , Tyr Z , and the Cytb 559 heme in the W-shaped difference spectrum. However, the use of a mutant of the P D2 axial His ligand, the D2-His197Ala, shows that the P D2 environment seems involved in the formation of "W-shaped" signal., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Some cyanobacteria can do photosynthesis using not only visible but also far-red light that is unused by most other oxygenic photoautotrophs because of its lower energy content. These species have a modified photosynthetic apparatus containing red-shifted pigments. The incorporation of red-shifted pigments decreases the photochemical efficiency of photosystem I and, especially, photosystem II, and it might affect the distribution of excitation energy between the two photosystems with possible consequences on the activity of the entire electron transport chain. To investigate the in vivo effects on photosynthetic activity of these pigment changes, we present here the adaptation of a spectroscopic method, based on a physical phenomenon called ElectroChromic Shift (ECS), to the far-red absorbing cyanobacteria Acaryochloris marina and Chroococcidiopsis thermalis PCC7203. ECS measures the electric field component of the trans-thylakoid proton motive force generated by photosynthetic electron transfer. We show that ECS can be used in these cyanobacteria to investigate in vivo the stoichiometry of photosystem I and photosystem II and their absorption cross-section, as well as the overall efficiency of light energy conversion into electron transport. Our results indicate that both species use visible and far-red light with similar efficiency, despite significant differences in their light absorption characteristics. ECS thus represents a new non-invasive tool to study the performance of naturally occurring far-red photosynthesis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Phthalocyanines are artificial macrocycles that can harbour a central metal atom with four symmetric coordinations. Similar to metal-porphyrins, metal-phthalocyanines (M-PCs) may bind small molecules, especially diatomic gases such as NO and O 2 . Furthermore, various chemical chains can be grafted at the periphery of the M-PC macrocycle, which can change its properties, including the interaction with diatomic gases. In this study, we synthesized Zn-PCs with two different substituents and investigated their effects on the interaction and dynamics of nitric oxide (NO). Time-resolved absorption spectroscopy from picosecond to millisecond revealed that NO dynamics dramatically depends on the nature of the groups grafted to the Zn-PC macrocycle. These experimental results were rationalized by DFT calculations, which demonstrate that electrostatic interactions between NO and the quinoleinoxy substituent modify the potential energy surface and decrease the energy barrier for NO recombination, thus controlling its affinity.

Photosystem II is the water/plastoquinone photo-oxidoreductase of photosynthesis. The photochemistry and catalysis occur in a quasi-symmetrical heterodimer, D1D2, that evolved from a homodimeric ancestor. Here, we studied site-directed mutants in PSII from the thermophilic cyanobacterium Thermosynechoccocus elongatus, focusing on the primary electron donor chlorophyll a in D1, Chl D1 , and on its symmetrical counterpart in D2, Chl D2 , which does not play a direct photochemical role. The main conserved amino acid specific to Chl D1 is D1/T179, which H-bonds the water ligand to its Mg 2+ , while its counterpart near Chl D2 is the non-H-bonding D2/I178. The symmetrical-swapped mutants, D1/T179I and D2/I178T, and a second Chl D2 mutant, D2/I178H, were studied. The D1 mutations affected the 686 nm absorption attributed to Chl D1 , while the D2 mutations affected a 663 nm feature, tentatively attributed to Chl D2 . The mutations had little effect on enzyme activity and forward electron transfer, reflecting the robustness of the overall enzyme function. In contrast, the mutations significantly affected photodamage and protective mechanisms, reflecting the importance of redox tuning in these processes. In D1/T179I, the radical pair recombination triplet on Chl D1 was shared onto a pheophytin, presumably Phe D1 and the detection of 3 Phe D1 supports the proposed mechanism for the anomalously short lifetime of 3 Chl D1 ; e.g. electron transfer quenching by Q A - of 3 Phe D1 after triplet transfer from 3 Chl D1 . In D2/I178T, a charge separation could occur between Chl D2 and Phe D2 , a reaction that is thought to occur in ancestral precursors of PSII. These mutants help understand the evolution of asymmetry in PSII., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In the cyanobacterium Thermosynechococcus elongatus, there are three psbA genes coding for the Photosystem II (PSII) D1 subunit that interacts with most of the main cofactors involved in the electron transfers. Recently, the 3D crystal structures of both PsbA2-PSII and PsbA3-PSII have been solved [Nakajima et al., J. Biol. Chem. 298 (2022) 102668.]. It was proposed that the loss of one hydrogen bond of Phe D1 due to the D1-Y147F exchange in PsbA2-PSII resulted in a more negative E m of Phe D1 in PsbA2-PSII when compared to PsbA3-PSII. In addition, the loss of two water molecules in the Cl-1 channel was attributed to the D1-P173M substitution in PsbA2-PSII. This exchange, by narrowing the Cl-1 proton channel, could be at the origin of a slowing down of the proton release. Here, we have continued the characterization of PsbA2-PSII by measuring the thermoluminescence from the S 2 Q A - /DCMU charge recombination and by measuring proton release kinetics using time-resolved absorption changes of the dye bromocresol purple. It was found that i) the E m of Phe D1 - /Phe D1 was decreased by ∼30 mV in PsbA2-PSII when compared to PsbA3-PSII and ii) the kinetics of the proton release into the bulk was significantly slowed down in PsbA2-PSII in the S 2 Tyr Z • to S 3 Tyr Z and S 3 Tyr Z •  → (S 3 Tyr Z • )' transitions. This slowing down was partially reversed by the PsbA2/M173P mutation and induced by the PsbA3/P173M mutation thus confirming a role of the D1-173 residue in the egress of protons trough the Cl-1 channel., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A very high rate for cyclic electron flow (CEF) around PSI (~180 s - 1 or 210 s -1 in minimum medium or in the presence of a carbon source respectively) is measured in the presence of methyl viologen (MV) in intact cells of Chlamydomonas reinhardtii under anaerobic conditions. The observation of an efficient CEF in the presence of methyl viologen is in agreement with the previous results reports of Asada et al. in broken chloroplasts (Plant Cell Physiol. 31(4) (1990) 557-564). From the analysis of the P700 and PC absorbance changes, we propose that a confinement between 2 PC molecules, 1 PSI and 1 cytb 6 f corresponding to a functional supercomplex is responsible for these high rates of CEF. Supercomplex formation is also observed in the absence of methyl viologen, but with lower maximal CEF rate (about 100 s -1 ) suggesting that this compound facilitates the mediation of electron transfer from PSI acceptors to the stromal side of cytb 6 f. Further analysis of CEF in mutants of Chlamydomonas defective in state transitions shows the requirement of a kinase-driven transition to state 2 to establish this functional supercomplex configuration. However, a movement of the LHCII antennae is not involved in this process. We discuss the possible involvement of auxiliary proteins, among which is a small cytb 6 f-associated polypeptide, the PETO protein, which is one of the targets of the STT7 kinase., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Photosystem II (PSII) uses the energy from red light to split water and reduce quinone, an energy-demanding process based on chlorophyll a (Chl-a) photochemistry. Two types of cyanobacterial PSII can use chlorophyll d (Chl-d) and chlorophyll f (Chl-f) to perform the same reactions using lower energy, far-red light. PSII from Acaryochloris marina has Chl-d replacing all but one of its 35 Chl-a, while PSII from Chroococcidiopsis thermalis , a facultative far-red species, has just 4 Chl-f and 1 Chl-d and 30 Chl-a. From bioenergetic considerations, the far-red PSII were predicted to lose photochemical efficiency and/or resilience to photodamage. Here, we compare enzyme turnover efficiency, forward electron transfer, back-reactions and photodamage in Chl-f-PSII, Chl-d-PSII, and Chl-a-PSII. We show that: (i) all types of PSII have a comparable efficiency in enzyme turnover; (ii) the modified energy gaps on the acceptor side of Chl-d-PSII favour recombination via P D1 + Phe - repopulation, leading to increased singlet oxygen production and greater sensitivity to high-light damage compared to Chl-a-PSII and Chl-f-PSII; (iii) the acceptor-side energy gaps in Chl-f-PSII are tuned to avoid harmful back reactions, favouring resilience to photodamage over efficiency of light usage. The results are explained by the differences in the redox tuning of the electron transfer cofactors Phe and Q A and in the number and layout of the chlorophylls that share the excitation energy with the primary electron donor. PSII has adapted to lower energy in two distinct ways, each appropriate for its specific environment but with different functional penalties., Competing Interests: SV, WR, SS, DN, RA, HD, JS, AB, AF, AR No competing interests declared, (© 2022, Viola et al.)

The stoichiometry and kinetics of the proton release were investigated during each transition of the S-state cycle in Photosystem II (PSII) from Thermosynechococcus elongatus containing either a Mn 4 CaO 5 (PSII/Ca) or a Mn 4 SrO 5 (PSII/Sr) cluster. The measurements were done at pH 6.0 and pH 7.0 knowing that, in PSII/Ca at pH 6.0 and pH 7.0 and in PSII/Sr at pH 6.0, the flash-induced S 2 -state is in a low-spin configuration (S 2 LS ) whereas in PSII/Sr at pH 7.0, the S 2 -state is in a high-spin configuration (S 2 HS ) in half of the centers. Two measurements were done; the time-resolved flash dependent i) absorption of either bromocresol purple at pH 6.0 or neutral red at pH 7.0 and ii) electrochromism in the Soret band of P D1 at 440 nm. The fittings of the oscillations with a period of four indicate that one proton is released in the S 1 to S 2 HS transition in PSII/Sr at pH 7.0. It has previously been suggested that the proton released in the S 2 LS to S 3 transition would be released in a S 2 LS Tyr Z •  → S 2 HS Tyr Z • transition before the electron transfer from the cluster to Tyr Z • occurs. The release of a proton in the S 1 Tyr Z •  → S 2 HS Tyr Z transition would logically imply that this proton release is missing in the S 2 HS Tyr Z • to S 3 Tyr Z transition. Instead, the proton release in the S 1 to S 2 HS transition in PSII/Sr at pH 7.0 was mainly done at the expense of the proton release in the S 3 to S 0 and S 0 to S 1 transitions. However, at pH 7.0, the electrochromism of P D1 seems larger in PSII/Sr when compared to PSII/Ca in the S 3 state. This points to the complex link between proton movements in and immediately around the Mn 4 cluster and the mechanism leading to the release of protons into the bulk., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Photosystem II (PSII), the oxygen-evolving enzyme, consists of 17 trans-membrane and 3 extrinsic membrane proteins. Other subunits bind to PSII during assembly, like Psb27, Psb28, and Tsl0063. The presence of Psb27 has been proposed (Zabret et al. in Nat Plants 7:524-538, 2021; Huang et al. Proc Natl Acad Sci USA 118:e2018053118, 2021; Xiao et al. in Nat Plants 7:1132-1142, 2021) to prevent the binding of PsbJ, a single transmembrane α-helix close to the quinone Q B binding site. Consequently, a PSII rid of Psb27, Psb28, and Tsl0034 prior to the binding of PsbJ would logically correspond to an assembly intermediate. The present work describes experiments aiming at further characterizing such a ∆PsbJ-PSII, purified from the thermophilic Thermosynechococcus elongatus, by means of MALDI-TOF spectroscopy, thermoluminescence, EPR spectroscopy, and UV-visible time-resolved spectroscopy. In the purified ∆PsbJ-PSII, an active Mn 4 CaO 5 cluster is present in 60-70% of the centers. In these centers, although the forward electron transfer seems not affected, the Em of the Q B /Q B - couple increases by ≥ 120 mV , thus disfavoring the electron coming back on Q A . The increase of the energy gap between Q A /Q A - and Q B /Q B - could contribute in a protection against the charge recombination between the donor side and Q B - , identified at the origin of photoinhibition under low light (Keren et al. in Proc Natl Acad Sci USA 94:1579-1584, 1997), and possibly during the slow photoactivation process., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Many cyanobacteria species can use both plastocyanin and cytochrome c 6 as lumenal electron carriers to shuttle electrons from the cytochrome b 6 f to either photosystem I or the respiratory cytochrome c oxidase. In Synechocystis sp. PCC6803 placed in darkness, about 60% of the active PSI centres are bound to a reduced electron donor which is responsible for the fast re-reduction of P 700 in vivo after a single charge separation. Here, we show that both cytochrome c 6 and plastocyanin can bind to PSI in the dark and participate to the fast phase of P 700 reduction, but the fraction of pre-bound PSI is smaller in the case of cytochrome c 6 than with plastocyanin. Because of the inter-connection of respiration and photosynthesis in cyanobacteria, the inhibition of the cytochrome c oxidase results in the over-reduction of the photosynthetic electron transfer chain in the dark that translates into a lag in the kinetics of P 700 oxidation at the onset of light. We show that this is true both with plastocyanin and cytochrome c 6 , indicating that the partitioning of electron transport between respiration and photosynthesis is regulated in the same way independently of which of the two lumenal electron carriers is present, although the mechanisms of such regulation are yet to be understood., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The Mn 4 CaO 5 cluster of photosystem II (PSII) advances sequentially through five oxidation states (S 0 to S 4 ). Under the enzyme cycle, two water molecules are oxidized, O 2 is generated and four protons are released into the lumen. Umena et al. (2011) have proposed that, with other charged amino acids, the R323 residue of the D1 protein could contribute to regulate a proton egress pathway from the Mn 4 CaO 5 cluster and Tyr Z via a proton channel identified from the 3D structure. To test this suggestion, a PsbA3/R323E site-directed mutant has been constructed and the properties of its PSII have been compared to those of the PsbA3-PSII by using EPR spectroscopy, polarography, thermoluminescence and time-resolved UV-visible absorption spectroscopy. Neither the oscillations with a period four nor the kinetics and S-state-dependent stoichiometry of the proton release were affected. However, several differences have been found: (1) the P 680 + decay in the hundreds of ns time domain was much slower in the mutant, (2) the S 2 Q A - /DCMU and S 3 Q A - /DCMU radiative charge recombination occurred at higher temperatures and (3) the S 0 Tyr Z • , S 1 Tyr Z • , S 2 Tyr Z • split EPR signals induced at 4.2 K by visible light from the S 0 Tyr Z , S 1 Tyr Z , S 2 Tyr Z , respectively, and the (S 2 Tyr Z • )' induced by NIR illumination at 4.2 K of the S 3 Tyr Z state differed. It is proposed that the R323 residue of the D1 protein interacts with Tyr Z likely via the H-bond network previously proposed to be a proton channel. Therefore, rather than participating in the egress of protons to the lumen, this channel could be involved in the relaxations of the H-bonds around Tyr Z by interacting with the bulk, thus tuning the driving force required for Tyr Z oxidation., (© 2020 Scandinavian Plant Physiology Society.)

Electrochromic band-shifts have been investigated in Photosystem II (PSII) from Thermosynechoccocus elongatus. Firstly, by using Mn-depleted PsbA1-PSII and PsbA3-PSII in which the Q X absorption of Phe D1 differs, a band-shift in the Q X region of Phe D2 centered at ~ 544 nm has been identified upon the oxidation, at pH 8.6, of Tyr D . In contrast, a band-shift due to the formation of either Q A •- or Tyr Z • is observed in PsbA3-PSII at ~ 546 nm, as expected with E130 H-bonded to Phe D1 and at ~ 544 nm as expected with Q130 H-bonded to Phe D1 . Secondly, electrochromic band-shifts in the Chla Soret region have been measured in O 2 -evolving PSII in PsbA3-PSII, in the PsbA3/H198Q mutant in which the Soret band of P D1 is blue shifted and in the PsbA3/T179H mutant. Upon Tyr Z • Q A •- formation the Soret band of P D1 is red shifted and the Soret band of Chl D1 is blue shifted. In contrast, only P D1 undergoes a detectable S-state dependent electrochromism. Thirdly, the time resolved S-state dependent electrochromism attributed to P D1 is biphasic for all the S-state transitions except for S 1 to S 2 , and shows that: i) the proton release in S 0 to S 1 occurs after the electron transfer and ii) the proton release and the electron transfer kinetics in S 2 to S 3 , in T. elongatus, are significantly faster than often considered. The nature of S 2 Tyr Z • is discussed in view of the models in the literature involving intermediate states in the S 2 to S 3 transition., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Nearly 50% of patients with de novo acute myeloid leukemia (AML) harbor an apparently normal karyotype (NK) by conventional cytogenetic techniques showing a very heterogeneous prognosis. This could be related to the presence of cryptic cytogenetic abnormalities (CCA) not detectable by conventional methods. The study of copy number alterations (CNA) and loss of heterozygozity (LOH) in hematological malignancies is possible using a high resolution SNP-array. Recently, in clinical practice the karyotype study has been complemented with the identification of point mutations in an increasing number of genes. We analyzed 252 de novo NK-AML patients from Hospital La Fe (n = 44) and from previously reported cohorts (n = 208) to identify CCA by SNP-array, and to integrate the analysis of CCA with molecular alterations detected by Next-Generation-sequencing. CCA were detected in 58% of patients. In addition, 49% of them harbored CNA or LOH and point mutations, simultaneously. Patients were grouped in 3 sets by their abnormalities: patients carrying several CCA simultaneously, patients with mutations in FLT3, NPM1 and/or DNMT3A and patients with an amalgam of mutations. We found a negative correlation between the number of CCA and the outcome of the patients. This study outlines that CCA are present in up to 50% of NK-AML patients and have a negative impact on the outcome. CCA may contribute to the heterogeneous prognosis.

Two pale green mutants of the green alga Chlamydomonas reinhardtii, which have been used over the years in many photosynthesis studies, the BF4 and p71 mutants, were characterized and their mutated gene identified in the nuclear genome. The BF4 mutant is defective in the insertase Alb3.1 whereas p71 is defective in cpSRP43. The two mutants showed strikingly similar deficiencies in most of the peripheral antenna proteins associated with either photosystem I or photosystem 2. As a result the two photosystems have a reduced antenna size with photosystem 2 being the most affected. Still up to 20% of the antenna proteins remain in these strains, with the heterodimer Lhca5/Lhca6 showing a lower sensitivity to these mutations. We discuss these phenotypes in light of those of other allelic mutants that have been described in the literature and suggest that eventhough the cpSRP route serves as the main biogenesis pathway for antenna proteins, there should be an escape pathway which remains to be genetically identified., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In plants, algae, and some photosynthetic bacteria, the ElectroChromic Shift (ECS) of photosynthetic pigments, which senses the electric field across photosynthetic membranes, is widely used to quantify the activity of the photosynthetic chain. In cyanobacteria, ECS signals have never been used for physiological studies, although they can provide a unique tool to study the architecture and function of the respiratory and photosynthetic electron transfer chains, entangled in the thylakoid membranes. Here, we identified bona fide ECS signals, likely corresponding to carotenoid band shifts, in the model cyanobacteria Synechococcus elongatus PCC7942 and Synechocystis sp. PCC6803. These band shifts, most likely originating from pigments located in photosystem I, have highly similar spectra in the 2 species and can be best measured as the difference between the absorption changes at 500 to 505 nm and the ones at 480 to 485 nm. These signals respond linearly to the electric field and display the basic kinetic features of ECS as characterized in other organisms. We demonstrate that these probes are an ideal tool to study photosynthetic physiology in vivo, e.g., the fraction of PSI centers that are prebound by plastocyanin/cytochrome c 6 in darkness (about 60% in both cyanobacteria, in our experiments), the conductivity of the thylakoid membrane (largely reflecting the activity of the ATP synthase), or the steady-state rates of the photosynthetic electron transport pathways., Competing Interests: The authors declare no competing interest.

The monomeric chlorophyll, Chl D1 , which is located between the P D1 P D2 chlorophyll pair and the pheophytin, Pheo D1, is the longest wavelength chlorophyll in the heart of Photosystem II and is thought to be the primary electron donor. Its central Mg 2+ is liganded to a water molecule that is H-bonded to D1/T179. Here, two site-directed mutants, D1/T179H and D1/T179V, were made in the thermophilic cyanobacterium, Thermosynechococcus elongatus, and characterized by a range of biophysical techniques. The Mn 4 CaO 5 cluster in the water-splitting site is fully active in both mutants. Changes in thermoluminescence indicate that i) radiative recombination occurs via the repopulation of *Chl D1 itself; ii) non-radiative charge recombination reactions appeared to be faster in the T179H-PSII; and iii) the properties of P D1 P D2 were unaffected by this mutation, and consequently iv) the immediate precursor state of the radiative excited state is the Chl D1 + Pheo D1 - radical pair. Chlorophyll bleaching due to high intensity illumination correlated with the amount of 1 O 2 generated. Comparison of the bleaching spectra with the electrochromic shifts attributed to Chl D1 upon Q A - formation, indicates that in the T179H-PSII and in the WT*3-PSII, the Chl D1 itself is the chlorophyll that is first damaged by 1 O 2 , whereas in the T179V-PSII a more red chlorophyll is damaged, the identity of which is discussed. Thus, Chl D1 appears to be one of the primary damage site in recombination-mediated photoinhibition. Finally, changes in the absorption of Chl D1 very likely contribute to the well-known electrochromic shifts observed at ~430 nm during the S-state cycle., (Copyright © 2019. Published by Elsevier B.V.)

In Photosystem II (PSII), the Mn 4 CaO 5 -cluster of the active site advances through five sequential oxidation states (S 0 to S 4 ) before water is oxidized and O 2 is generated. The V185 of the D1 protein has been shown to be an important amino acid in PSII function (Dilbeck et al. Biochemistry 52 (2013) 6824-6833). Here, we have studied its role by making a V185T site-directed mutant in the thermophilic cyanobacterium Thermosynechococcus elongatus. The properties of the V185T-PSII have been compared to those of the WT*3-PSII by using EPR spectroscopy, polarography, thermoluminescence and time-resolved UV-visible absorption spectroscopy. It is shown that the V185 and the chloride binding site very likely interact via the H-bond network linking Tyr Z and the halide. The V185 contributes to the stabilization of S 2 into the low spin (LS), S = 1/2, configuration. Indeed, in the V185T mutant a high proportion of S 2 exhibits a high spin (HS), S = 5/2, configuration. By using bromocresol purple as a dye, a proton release was detected in the S 1 Tyr Z  → S 2 HS Tyr Z transition in the V185T mutant in contrast to the WT*3-PSII in which there is no proton release in this transition. Instead, in WT*3-PSII, a proton release kinetically much faster than the S 2 LS Tyr Z  → S 3 Tyr Z transition was observed and we propose that it occurs in the S 2 LS Tyr Z  → S 2 HS Tyr Z intermediate step before the S 2 HS Tyr Z  → S 3 Tyr Z transition occurs. The dramatic slowdown of the S 3 Tyr Z  → S 0 Tyr Z transition in the V185T mutant does not originate from a structural modification of the Mn 4 CaO 5 cluster since the spin S = 3 S 3 EPR signal is not modified in the mutant. More probably, it is indicative of the strong implication of V185 in the tuning of an efficient relaxation processes of the H-bond network and/or of the protein., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Nuclear Pore Complex (NPC) is of paramount importance for cellular processes since it is the unique gateway for molecular exchange through the nucleus. Unraveling the modifications of the NPC structure in response to physiological cues, also called nuclear pore plasticity, is key to the understanding of the selectivity of this molecular machinery. As a step towards this goal, we use the optical super-resolution microscopy method called direct Stochastic Optical Reconstruction Microscopy (dSTORM), to analyze oocyte development impact on the internal structure and large-scale organization of the NPC. Staining of the FG-Nups proteins and the gp210 proteins allowed us to pinpoint a decrease of the global diameter by measuring the mean diameter of the central channel and the luminal ring of the NPC via autocorrelation image processing. Moreover, by using an angular and radial density function we show that development of the Xenopus laevis oocyte is correlated with a progressive decrease of the density of NPC and an ordering on a square lattice.

We tested the hypothesis whether; the non-genomic action of progesterone (Pg) on vascular tissue would be associated with hormonal long term effect on the modulation of cell growth. Using rat aortic strips, we showed that the stimulatory effect of Pg on nitric oxide synthesis involved both kinase and phosphatase pathways. The increase in the vasoactive production was prevented by the MAPK inhibitor (PD98059). In addition, preincubation with a phosphatase antagonist potentiated the hormonal effect. Pg increased PKC activity, but the inhibition of PKC did not alter the stimulatory action of the hormone on nitric oxide generation. In endothelial cell cultures (EC), 24h treatment with Pg significantly diminished cell proliferation. This antiproliferative effect was suppressed by the PKC inhibitor chelerythrine (chel) and l-NAME (nitric oxide synthase inhibitor). We also observed that Pg stimulates EC migration. In summary, the present findings provide evidence of an integration of genomic and non-genomic effects in the mechanism of action displayed by Pg in vascular tissue. The fast effects elicited by the hormone implies signal transduction activation required for the regulation of vasoactive production, but also necessary for the modulation of endothelial cells growth.

The frequency of insulin-resistance (IR) and metabolic syndrome (MS) were examined in coronary patients using different criteria of definition. It was also analyzed which of them indicated a strong association with the presence and severity of the disease. This was a case-control study on 100 patients between 40 and 70 years old, assisted in a hospital center and there examined by angiography. IR was defined by insulin >15 mU/l, Homeostatic Model Assessment for insulin-resistance (HOMA-IR) >3.1 and the combination body mass index (BMI) >27.5 kg/m2 with HOMA-IR >3.6. MS was defined according to International Diabetes Federation and American Heart Association/National Heart, Lung and Blood Institute. Insulin >15 mU/l and HOMA-IR >3.1 had similar sensibility, 60.3%, and were significantly associated with the extension of coronary heart disease, p = 0.001 and p = 0.009 respectively. Whereas, BMI>27.5 kg/m2 with HOMA-IR>3.6 showed a lower sensibility, 43.1% and less association with severity, p = 0.028. The odds ratio (OR) for coronary heart disease were respectively: 3.16 (CI 95 1.28-7.79), p = 0.012; 2.93 (CI 95% 1.20-7.19) p = 0.019; 2.86 (CI 95% 1.10-7.41), p = 0.031. The frequency of SM defined according to American Heart Association/National Heart, Lung and Blood Institute was higher in coronary patients vs. controls (62.1% vs. 33.3%, p = 0.003). It was associated with disease in one or more vases (p = 0.011) and was its predictor, OR = 4.22 (CI 95% 1.65-10.83) p = 0.003. However, SM defined according to International Diabetes Federation was not associated with the presence or severity of coronary heart disease.