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Carbon dioxide capture and utilization is a strategic technology for moving away from fossil‐C. The conversion of CO2 into fuels demands energy and hydrogen that cannot be sourced from fossil‐C. Co‐processing of CO2 and water under solar irradiation will have a key role in the long‐term for carbon‐recycling and energy products production. This article discusses the synthesis, characterization and application of the two‐phase composite photocatalyst, In2O3@g‐C3N4, formed by thermal condensation of melamine in the presence of indium(III)nitrate. The composite exhibits a n,n‐heterojunction between two n‐type semiconductors, g‐C3N4 and In2O3, leading to a more efficient charge separation. The composite has a flat band potential enabling it to effectively catalyze the reduction of CO2 in the gas phase to produce CO, CH4 and CH3OH. While the composite's overall photocatalytic efficiency is comparable to that of neat g‐C3N4, its ability to promote multielectron‐transfer and Proton Coupled to Electron Transfer (PCET) suggests that there is a potential for further optimization of its properties. The use of labelled 13CO2 has allowed us to clearly exclude that the reduced species are derived from the photocatalyst decomposition or the degradation of contaminants. [ABSTRACT FROM AUTHOR]

The enzymatic effectiveness in the reaction cascade that reduces CO2 to methanol in water at room‐temperature faces various constraints. One of the major challenges is the short life of costly enzymes: immobilization is used to make them more stable and recyclable. The comparative analysis of the several immobilization techniques reported in the literature is challenging due to the diverse reaction conditions (single enzyme test or pool of enzymes test) and experimental setups, as well as the high variability in the amount of enzymes and cofactor. In the present study, a comparison is presented among three different methods (co‐encapsulation into Ca–alginate beads, co‐absorption onto zirconium(IV) phosphate (ZrP) and covalent binding to dialdehydecellulose [DAC]) of co‐immobilization of the three dehydrogenases Fatedehydrogenase (DH), FaldDH, and alcohol dehydrogenase, used in equal amount and under the same experimental conditions, so to check at what extension the support and the immobilization method can influence the activity of the enzymatic pool. DAC is used for the first time to support the three DHs and results to be the best method of immobilization with respect to those used here, that also allows longer life on enzymes and repeated recycling of the supported enzymes, increasing the overall methanol production with respect to the free enzymes. [ABSTRACT FROM AUTHOR]

Background/Aims Methods Results Conclusions As a microvascular complication, diabetic kidney disease is the leading cause of chronic kidney disease and end‐stage renal disease worldwide. While the underlying pathophysiology driving transition of diabetic kidney disease to renal failure is yet to be fully understood, recent studies suggest that cellular senescence is central in disease development and progression. Consequently, understanding the molecular mechanisms which initiate and drive senescence in response to the diabetic milieu is crucial in developing targeted therapies that halt progression of renal disease.To understand the mechanistic pathways underpinning cellular senescence in the context of diabetic kidney disease, we reviewed the literature using PubMed for English language articles that contained key words related to senescence, inflammation, fibrosis, senescence‐associated secretory phenotype (SASP), autophagy, and diabetes.Aberrant accumulation of metabolically active senescent cells is a notable event in the progression of diabetic kidney disease. Through autocrine‐ and paracrine‐mediated mechanisms, resident senescent cells potentiate inflammation and fibrosis through increased expression and secretion of pro‐inflammatory cytokines, chemoattractants, recruitment of immune cells, myofibroblast activation, and extracellular matrix remodelling. Compounds that eliminate senescent cells and/or target the SASP – including senolytic and senomorphics drugs – demonstrate promising results in reducing the senescent cell burden and associated pro‐inflammatory effect.Here we evidence the link between senescence and diabetic kidney disease and highlight underlying molecular mechanisms and potential therapeutic targets that could be exploited to delay disease progression and improve outcomes for individuals with the disease. Trials are now required to translate their therapeutic potential to a clinical setting. [ABSTRACT FROM AUTHOR]

The ability to spatially control and modify material properties on the nanoscale, including within nanoscale objects themselves, is a fundamental requirement for the development of advanced nanotechnologies. The development of a platform for nanoscale advanced materials engineering (P-NAME) designed to meet this demand is demonstrated. P-NAME delivers a high-resolution focused ion beam system with a coincident scanning electron microscope and secondary electron detection of single-ion implantation events. The isotopic mass-resolution capability of the P-NAME system for a wide range of ion species is demonstrated, offering access to the implantation of isotopes that are vital for nanomaterials engineering and nanofunctionalization. The performance of the isotopic mass selection is independently validated using secondary ion mass spectrometry (SIMS) for a number of species implanted into intrinsic silicon. The SIMS results are shown to be in good agreement with dynamic ion implantation simulations, demonstrating the validity of this simulation approach. The wider performance capabilities of P-NAME, including sub-10 nm ion beam imaging resolution and the ability to perform direct-write ion beam doping and nanoscale ion lithography, are also demonstrated. [ABSTRACT FROM AUTHOR]

The synthesis and reactivity in an [4+2] inverse electron demand hetero Diels‐Alder reaction (ihDA) of an original class of electron‐poor heterodienes, the N‐substituted‐1H‐benzo[c][1,2]thiazin‐4‐one‐2,2‐dioxides, are described. These are highly reactive electrophiles that allow easy access to unprecedented benzo‐thiazine glyco‐fused derivatives in a remarkably selective way, even when using acetylated glycals, previously unexplored within this version of ihDA. DFT calculations support the experimental data, and moreover show that acetylated dienophiles can easily react making cycloadditions feasible. [ABSTRACT FROM AUTHOR]

African trypanosomes cause disease in humans and livestock, avoiding host immunity by changing the expression of variant surface glycoproteins (VSGs); the major glycosylphosphatidylinositol (GPI) anchored antigens coating the surface of the bloodstream stage. Proper trafficking of VSGs is therefore critical to pathogen survival. The valence model argues that GPI anchors regulate progression and fate in the secretory pathway and that, specifically, a valence of two (VSGs are dimers) is critical for stable cell surface association. However, recent reports that the MITat1.3 (M1.3) VSG N‐terminal domain (NTD) behaves as a monomer in solution and in a crystal structure challenge this model. We now show that the behavior of intact M1.3 VSG in standard in vivo trafficking assays is consistent with an oligomer. Nevertheless, Blue Native Gel electrophoresis and size exclusion chromatography‐multiangle light scattering chromatography of purified full length M1.3 VSG indicates a monomer in vitro. However, studies with additional VSGs show that multiple oligomeric states are possible, and that for some VSGs oligomerization is concentration dependent. These data argue that individual VSG monomers possess different propensities to self‐oligomerize, but that when constrained at high density to the cell surface, oligomeric species predominate. These results resolve the apparent conflict between the valence hypothesis and the M1.3 NTD VSG crystal structure. [ABSTRACT FROM AUTHOR]

Keywords: Brosimum wood; case report; catholic bracelet; coumarins; patch test; wood EN Brosimum wood case report catholic bracelet coumarins patch test wood 71 73 3 06/19/20 20200701 NES 200701 Wood is used to manufacture furniture, household utensils, musical instruments, and ornaments such as crafts jewelry. Brosimum wood, case report, catholic bracelet, coumarins, patch test, wood. [Extracted from the article]

Dihydrodibenzo[b,f]azepines and dibenzo[b,f]azepines can be efficiently synthesized from aryl bromides, o‐bromoanilines and norbornene or norbornadiene by means of palladium catalysis. This protocol gives access to dibenzo[b,f]azepine core containing a variety of electron‐withdrawing substituents on both aromatic rings and complements the previously reported methodology where electron rich aryl iodides were preferentially used. The presence of KI, even in sub‐stoichiometric amount, is crucial for this three‐component reaction. The proper addition of iodide anions has a dramatic effect on reaction rate and selectivity. A formal three‐step synthesis of the tricyclic antidepressant Clomipramine (Anafranil®) is also described. KI‐ck‐start required: Dibenzo[b,f]azepine derivatives can be efficiently synthesized from aryl bromides, o‐bromoanilines and norbornene or norbornadiene by means of palladium catalysis. The presence of KI, even in sub‐stoichiometric amount, is crucial for this three‐component reaction, as it promotes reaction rate and selectivity. A formal three‐step synthesis of the tricyclic antidepressant Clomipramine (Anafranil®) is also described. [ABSTRACT FROM AUTHOR]

Abstract: The sustainable chemical industry encompasses a shift from the use of fossil carbon to renewable carbon. The synthesis of chemicals from nonedible biomass (cellulosic or oil) represents one of the key steps for “greening” the chemical industry. In this paper, we report the aerobic oxidative cleavage of C6 polyols (5‐HMF, glucose, fructose and sucrose) to oxalic acid (OA) and succinic acid (SA) in water under mild conditions using M@CNT and M@NCNT (M=Fe, V; CNT=carbon nanotubes; NCNT=N‐doped CNT), which, under suitable conditions, were recoverable and reusable without any loss of efficiency. The influence of the temperature, O2 pressure (P O 2 ), reaction time and stirring rate are discussed and the best reaction conditions are determined for an almost complete conversion of the starting material and a good OA yield of 48 %. SA and formic acid were the only co‐products. The former could be further converted into OA by oxidation in the presence of formic acid, resulting in an overall OA yield of >62 %. This process was clean and did not produce organic waste nor gas emissions. [ABSTRACT FROM AUTHOR]

In the recent decade, CO2 has increasingly been regarded not only as a greenhouse gas but even more as a chemical feedstock for carbon-based materials. Different strategies have evolved to realize CO2 utilization and conversion into fuels and chemicals. In particular, biological approaches have drawn attention, as natural CO2 conversion serves as a model for many processes. Microorganisms and enzymes have been studied extensively for redox reactions involving CO2. In this review, we focus on monitoring nonliving biocatalyzed reactions for the reduction of CO2 by using enzymes. We depict the opportunities but also challenges associated with utilizing such biocatalysts. Besides the application of enzymes with co-factors, resembling natural processes, and co-factor recovery, we also discuss implementation into photochemical and electrochemical techniques. [ABSTRACT FROM AUTHOR]

Fe0(bpy)(pyea) ( 2; bpy=2,2′-bipyridine, pyea=2-aminoethyl-pyridine), a 16-electron species, was synthesized by reduction of FeCl2(bpy)(pyea) ( 1) using Na-strips. It is a diamagnetic low-melting solid (m.p. 295 K) stable under N2 and easily decomposed by radiations even at low temperature. It was fully characterized by elemental analyses and multinuclear NMR. Complex 2 acts as an active hydrogenation catalyst, but has a very short lifetime. In fact, it reacts with H2 (0.1-1 MPa) at room temperature in toluene and affords in a few minutes a new Fe0 complex characterized as Fe0(bpy)(η6-picoline) ( 3), inactive to hydrogenation. Picoline is derived from the sp3-sp3 C−C bond cleavage of the aminoethyl arm of the pyea ligand. The rapid evolution of the putative intermediate FeH2(bpy)(pyea) ( 4) has not allowed the isolation such Fe-hydrido species. The interaction of H2 with 2 has been studied by DFT, which has allowed to demonstrate that 3 is lower in energy than 2+H2, justifying the fact that the intermediate dihydride was not isolated. Interestingly, 3 was also obtained by reaction of 1 with NaBH4 or with glycerol-KOH. Complex 2 is one of the rare examples of Fe0 complex stabilized by a set of only N-donor atoms. The reaction with glycerol confirms the potential role of Fe in catalytic hydrogenation reactions using bio-glycerol as a H-source. [ABSTRACT FROM AUTHOR]

Highlights from the article: Using fossil-C for powering reduction of CO SB 2 sb and producing hydrogen for its reduction would be a I nonsense i in a fossil-C based energy frame, as more CO SB 2 sb would be emitted than is converted. Making an extrapolation of the use of CO SB 2 sb in only low-energy processes brings to an increase up to I ca i 350 Mt y SP -1 sp in 10-12 years from now, with a possible 1 Gt y SP -1 sp avoided CO SB 2 sb .[1] Such amount is a drop in the ocean of the 37+ Gt y SP -1 sp emitted CO SB 2 sb and will not save the world. If catalysis is a direct conversion of CO SB 2 sb , use of biomass is its indirect use leaving to Nature the hard job of converting CO SB 2 sb into useful products and applying the biorefinery approach to biomass valorization.

New catalytic systems based on ceria have been used in the direct carboxylation of ethanol. The catalytic behavior of Al2O3 and Nb2O5 loaded ceria is compared, the latter showing a better performance. A morphological and structural study has been carried out on Nb2O5/CeO2 catalysts in order to explain their behavior in catalysis. Pervaporation membranes have been used for water separation. The synthesis of diethylcarbonate (DEC) has been carried out either in a liquid phase (ethanol) pressurized with CO2 or in supercritical conditions. A set-up has been developed that allows the production of quite pure DEC (>90 %) with recycling of CO2 and ethanol. [ABSTRACT FROM AUTHOR]

A p-type semiconductor, CuI, has been synthesized, characterized, and tested as a photocatalyst for CO2 reduction under UV/Vis irradiation in presence of isopropanol as a hole scavenger. Formation of CO, CH4, and/or HCOOH was observed. The photocatalytic activity of CuI was attributed to the very low potential of the conduction band edge (i.e., -2.28 V vs. NHE). Photocurrents generated by the studied material confirm a high efficiency of the photoinduced interfacial electrontransfer processes. Our studies show that p-type semiconductors may be effective photocatalysts for CO2 reduction, even better than extensively studied n-type titanium dioxide, owing to the low potential of the conduction band edge. [ABSTRACT FROM AUTHOR]

A simple, cheap, and selective catalyst based on copper/cerium oxides is described for the oxidation of 5-(hydroxymethyl)furfural (5-HMF) in water. An almost quantitative conversion (99 %) with excellent (90 %) selectivity towards the formation of 5-formyl-2-furancarboxylic acid, a platform molecule for other high value chemicals, is observed. The catalyst does not require any pretreatment or additives, such as bases, to obtain high yield and selectivity in water as solvent and using oxygen as oxidant. When a physical mixture of the oxides is used, low conversion and selectivity are observed. Air can be used instead of oxygen, but a lower conversion rate is observed if the same overall pressure is used, and the selectivity remains high. The catalyst can be recovered almost quantitatively and reused. Deactivation of the catalyst, observed in repeated runs, is due to the deposition of humins on its surface. Upon calcination the catalyst almost completely recovers its activity and selectivity, proving that the catalyst is robust. [ABSTRACT FROM AUTHOR]

We describe a process for the selective conversion of C6-polyols into 5-hydroxymethylfurfural (5-HMF) in biphasic systems of organic carbonate/water (OC/W), with cerium(IV) phosphates as catalysts. Different reaction parameters such as the OC/W ratio, catalyst loading, reaction time, and temperature, were investigated for the dehydration of fructose. Under the best reaction conditions, a yield of 67.7 % with a selectivity of 93.2 % was achieved at 423 K after 6 h of reaction using [(Ce(PO4)1.5(H2O)(H3O)0.5(H2O)0.5)] as the catalyst. A maximum yield of 70 % with the same selectivity was achieved after 12 h. At the end of the reaction, the catalyst was removed by centrifugation, the organic phase was separated from water and evaporated in vacuo (with solvent recovery), and solid 5-HMF was isolated (purity >99 %). The recovery and reuse of the catalyst and the relationship between the structure of the OC and the efficiency of the extraction are discussed. The OC/W system influences the lifetime of the catalysts positively compared to only water. [ABSTRACT FROM AUTHOR]

New iron(II) compounds with N-donor ligands [2,2′-bipyridine (bpy) and 2-(2-pyridyl)ethylamine (pyea)] were synthesized, and their reactivity with carbon dioxide was investigated. The reactions of Fe(bpy)(pyea)Cl2 ( 1) with CO2 (0.9 MPa) afforded the carbamato derivative Fe(bpy)(pyea-CO2)Cl2 ( 2), which reacted with CH3Li to afford the monomethyl carbamato complex Fe(bpy)(pyea-CO2)ClCH3 ( 3), an example of a carbamato species that is stable over a carboxylato moiety. Fe[(bpy)(pyea)](CH3)2 ( 4), obtained by reaction of 1 with CH3Li, was treated with CO2 (0.3-0.5 MPa) to afford the dicarboxylato species Fe[(bpy)(pyea)](O2CCH3)2 ( 5), which provides evidence of normal double insertion of CO2 into the Fe-C bond. The reaction of 5 with HCl afforded 1 and CH3-CO2H, which confirmed the mode of bonding of the -O2CCH3 moiety to the Fe center. To verify the preference of insertion of CO2 into the Fe-C or the Fe-N bond, 1 was treated with MeLi (1 equiv.), and Fe(bpy)(pyea)Cl(CH3) ( 6) was isolated as a low-melting solid. The latter was treated with CO2 (0.5 MPa), and the product of insertion into the Fe-CH3 bond was observed as the only carboxylate ( 7). The faster insertion into the Fe-CH3 bond is explained by the fact that the N donor is quaternarized upon interaction with the metal center and has no free electrons available to interact with the C acceptor of the cumulene molecule; thus, more-forcing conditions (0.9 MPa) are required for the insertion to occur. [ABSTRACT FROM AUTHOR]

Epoxides are essential in organic chemistry. The of unsubstituted cyclic dienes 2, 3, 4 and triene 5 using dimethyldioxirane ( 1a) and its trifluoro analog 1b methyl(trifluoromethyl)dioxirane has been investigated. The excellent yields obtained (90-98%) are accompanied by outstandingly high diastereoselectivities (90-98%). Interpretation of results based upon the early idea that polar groups can direct the dioxirane attack by dipole-dipole interaction provides a likely rationale, along with a more generalized mechanistic view. [ABSTRACT FROM AUTHOR]

T rypanosoma brucei is a unicellular parasite that causes sleeping sickness in humans. Most of its transcription is constitutive and driven by RNA polymerase II. RNA polymerase I ( Pol I) transcribes not only ribosomal RNA genes, but also protein-encoding genes, including variant surface glycoproteins ( VSGs) and procyclins. In T . brucei, histone H1 ( H1) is required for VSG silencing and chromatin condensation. However, whether H1 has a genome-wide role in transcription is unknown. Here, using RNA sequencing we show that H1 depletion changes the expression of a specific cohort of genes. Interestingly, the predominant effect is partial loss of silencing of Pol I loci, such as VSG and procyclin genes. Labelling of nascent transcripts with 4-thiouridine showed that H1 depletion does not alter the level of labelled Pol II transcripts. In contrast, the levels of 4 sU-labelled Pol I transcripts were increased by two- to sixfold, suggesting that H1 preferentially blocks transcription at Pol I loci. Finally, we observed that parasites depleted of H1 grow almost normally in culture but they have a reduced fitness in mice, suggesting that H1 is important for host-pathogen interactions. [ABSTRACT FROM AUTHOR]

Photocatalytic carboxylation of acetylacetone with carbon dioxide has been performed by using ZnS-based photocatalysts. The formation of two isomeric carboxylic acids, as proven by IR and 13C NMR spectroscopy, was observed. The reaction yield was enhanced after deposition of ruthenium nanoparticles on ZnS. The reaction encompasses ruthenium-mediated one-electron reduction of CO2 to CO2.− with electrons from the conduction band of ZnS and one-hole oxidation of acetylacetone to the relevant radical. Coupling of photogenerated radicals leads to the formation of carboxylic acids. Generation of CO2.− has been confirmed by spin-trapping EPR measurements. The process described herein may find applications for the solar-light-driven green synthesis of C n+1 carboxylic compounds from C n substrates by utilising carbon dioxide. [ABSTRACT FROM AUTHOR]

Diphenyl carbonate (DPC) plays a key role in phosgene-free carbonylation processes. It can be produced by transesterification of dimethyl carbonate (DMC) with phenol in the presence of catalysts. Methyl phenyl carbonate (MPC) is first produced that is then converted into DPC by either disproportionation or further transesterification with phenol. Cerium-based bimetallic oxides (with the heterometal being niobium, iron, palladium, or aluminum) are used as catalysts in the transesterification of DMC to synthesize MPC. The catalytic activity is affected by the type and concentration of the heterometal. XPS, IR and elementary analyses are employed to characterize the new catalysts. Differently from pure oxides, the mixed oxides produce a significant increase of the conversion and selectivity towards MPC. [ABSTRACT FROM AUTHOR]

Oxazolidinones have been synthesized by reacting glycerol carbonate or glycerol with urea in the presence of γ-Zr phosphate as a catalyst. The conversion yield of the polyol or its carbonate depends on the temperature. Below 408 K the selectivity is 100 % with a conversion of up to 25 %, whereas increasing the temperature means that conversion yield grows, but the selectivity decreases, which makes the separation process more difficult. Starting from glycerol carbonate, two isomers, 6 and 6′, are formed with a quasi 1:1 molar ratio because urea can attack the carbonate moiety on both sides of the carboxylic CO moiety. From glycerol the formation of the 6′ isomer is preferred: the ratio of 6′/ 6 is close to 7. The oxazolidinones formed act as templates because they interact through hydrogen bonding with glycerol. The intensity of the interaction depends on the 6 or 6′ isomer: DFT calculations showed that the energy was 22.6 kcal mol−1 for 6-oxazolidinone and 25.7 kcal mol−1 for 6′-oxazolidinone. [ABSTRACT FROM AUTHOR]

Background information. The appropriate regulation of cell–cell adhesion is an important event in the homoeostasis of different cell types. In epithelial cells, tight adhesion mediated by E‐cadherin receptors is essential for the differentiation and functionality of epithelial sheets. Upon assembly of cadherin‐mediated cell–cell contacts, it is well established that the small GTPases Rho and Rac are activated and are necessary for junction stability. However, the role of the small GTPase Cdc42 in cadherin adhesion is less clear. Cdc42 can be activated by E‐cadherin in a breast tumour cell line, but the requirement for Cdc42 function for new junction assembly or maintenance has been contradictory. Cdc42 participation in cell–cell contacts has been inferred from the presence of filopodia, the typical F‐actin structure induced by Cdc42 activation, as cells approach each other to establish cell–cell contacts. Yet, under these conditions, the contribution of migration to filopodia protrusion cannot be excluded and the results are difficult to interpret. Results. In the present study, we set out to address (a) whether Cdc42 is activated by new E‐cadherin cell–cell contacts when junction assembly occurs without prior migration and (b) whether Cdc42 function is necessary for cadherin stability. We found that junction formation in confluent keratinocytes or upon E‐cadherin clustering decreased Cdc42‐GTP levels. In the absence of serum‐ and migration‐induced Cdc42 activation, we demonstrated that cell–cell contacts do not induce filopodia or require Cdc42 function to assemble. Conclusion. We conclude that Cdc42 does not participate in the early events that initiate stable cadherin adhesion in keratinocytes. Yet, it is feasible that Cdc42 may be activated at later time points or by other receptors. Cdc42 can then participate in additional functions during polarization, such as Golgi re‐positioning or basolateral trafficking. [ABSTRACT FROM AUTHOR]

Background information. The appropriate regulation of cell–cell adhesion is an important event in the homoeostasis of different cell types. In epithelial cells, tight adhesion mediated by E‐cadherin receptors is essential for the differentiation and functionality of epithelial sheets. Upon assembly of cadherin‐mediated cell–cell contacts, it is well established that the small GTPases Rho and Rac are activated and are necessary for junction stability. However, the role of the small GTPase Cdc42 in cadherin adhesion is less clear. Cdc42 can be activated by E‐cadherin in a breast tumour cell line, but the requirement for Cdc42 function for new junction assembly or maintenance has been contradictory. Cdc42 participation in cell–cell contacts has been inferred from the presence of filopodia, the typical F‐actin structure induced by Cdc42 activation, as cells approach each other to establish cell–cell contacts. Yet, under these conditions, the contribution of migration to filopodia protrusion cannot be excluded and the results are difficult to interpret. Results. In the present study, we set out to address (a) whether Cdc42 is activated by new E‐cadherin cell–cell contacts when junction assembly occurs without prior migration and (b) whether Cdc42 function is necessary for cadherin stability. We found that junction formation in confluent keratinocytes or upon E‐cadherin clustering decreased Cdc42‐GTP levels. In the absence of serum‐ and migration‐induced Cdc42 activation, we demonstrated that cell–cell contacts do not induce filopodia or require Cdc42 function to assemble. Conclusion. We conclude that Cdc42 does not participate in the early events that initiate stable cadherin adhesion in keratinocytes. Yet, it is feasible that Cdc42 may be activated at later time points or by other receptors. Cdc42 can then participate in additional functions during polarization, such as Golgi re‐positioning or basolateral trafficking. [ABSTRACT FROM AUTHOR]

Background information. The appropriate regulation of cell–cell adhesion is an important event in the homoeostasis of different cell types. In epithelial cells, tight adhesion mediated by E-cadherin receptors is essential for the differentiation and functionality of epithelial sheets. Upon assembly of cadherin-mediated cell–cell contacts, it is well established that the small GTPases Rho and Rac are activated and are necessary for junction stability. However, the role of the small GTPase Cdc42 in cadherin adhesion is less clear. Cdc42 can be activated by E-cadherin in a breast tumour cell line, but the requirement for Cdc42 function for new junction assembly or maintenance has been contradictory. Cdc42 participation in cell–cell contacts has been inferred from the presence of filopodia, the typical F-actin structure induced by Cdc42 activation, as cells approach each other to establish cell–cell contacts. Yet, under these conditions, the contribution of migration to filopodia protrusion cannot be excluded and the results are difficult to interpret. Results. In the present study, we set out to address (a) whether Cdc42 is activated by new E-cadherin cell–cell contacts when junction assembly occurs without prior migration and (b) whether Cdc42 function is necessary for cadherin stability. We found that junction formation in confluent keratinocytes or upon E-cadherin clustering decreased Cdc42-GTP levels. In the absence of serum- and migration-induced Cdc42 activation, we demonstrated that cell–cell contacts do not induce filopodia or require Cdc42 function to assemble. Conclusion. We conclude that Cdc42 does not participate in the early events that initiate stable cadherin adhesion in keratinocytes. Yet, it is feasible that Cdc42 may be activated at later time points or by other receptors. Cdc42 can then participate in additional functions during polarization, such as Golgi re-positioning or basolateral trafficking. [ABSTRACT FROM AUTHOR]

Synergistic/antagonistic effects of multiple contaminants in marine environments are almost completely unexplored. In the present study, we investigated the effects of heavy metals (Zn and Pb) and PCBs on picoplankton abundance, biomass, cell size distribution, and bacterial C production. Natural picoplankton assemblages were exposed to heavy metals (Zn or Pb), organic contaminants (PCBs, Aroclor 1260), and to a mixture of different contaminants. The results of the present study indicate that Zn addition stimulated heterotrophic growth, whereas Pb has a negative impact on heterotrophic picoplankton, particularly significant in the first 24 h. Heavy metals had no effects on the autotrophic component. The addition of Aroclor 1260 had a significant impact on abundance, biomass, and cell size of autotrophic and heterotrophic picoplankton, and reduced significantly bacterial secondary production. Three weeks after PCB treatment, heterotrophic bacteria displayed a clear resilience, both in terms of abundance and biomass, reaching values comparable to those of the controls, but not in terms of bacterial C production. Our results indicate that picoplankton can be sensitive indicators of impact determined by heavy metals and PCBs in coastal marine systems. [ABSTRACT FROM AUTHOR]