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When exposed to stress conditions, all cells induce mechanisms resulting in an attempt to adapt to stress that involve proteins which, once activated, trigger cell responses by modulating specific signaling pathways. In this work, using a combination of pulldown assays and mass spectrometry analyses, we identified the Neurospora crassa SEB-1 transcription factor that binds to the Stress Response Element (STRE) under heat stress. Orthologs of SEB-1 have been functionally characterized in a few filamentous fungi as being involved in stress responses; however, the molecular mechanisms mediated by this transcription factor may not be conserved. Here, we provide evidences for the involvement of N. crassa SEB-1 in multiple cellular processes, including response to heat, as well as osmotic and oxidative stress. The Δseb-1 strain displayed reduced growth under these conditions, and genes encoding stress-responsive proteins were differentially regulated in the Δseb-1 strain grown under the same conditions. In addition, the SEB-1-GFP protein translocated from the cytosol to the nucleus under heat, osmotic, and oxidative stress conditions. SEB-1 also regulates the metabolism of the reserve carbohydrates glycogen and trehalose under heat stress, suggesting an interconnection between metabolism control and this environmental condition. We demonstrated that SEB-1 binds in vivo to the promoters of genes encoding glycogen metabolism enzymes and regulates their expression. A genome-wide transcriptional profile of the Δseb-1 strain under heat stress was determined by RNA-seq, and a broad range of cellular processes was identified that suggests a role for SEB-1 as a protein interconnecting these mechanisms.

Circularly polarized luminescence (CPL) from lanthanide (LnIII) complexes has aroused extensive attention in the last decade owing to its potential use in displays or as anti-counterfeiting devices, for instance. However, the design of LnIII complexes matching high luminescence dissymmetry factor and CPL brightness still limits their real application. To help deal with this challenging task, presented herein is a series of [Eu(hfa)3(chiral)] complexes, (chiral = S-Bn-pybox = 2,6-bis((S)-4-benzyl-4,5-dihydrooxazole-2-yl)pyridine, S-Ph-pyox = (S)-4-phenyl-2-(pyridin-2-yl)-4,5-dihydrooxazole, or (R)-Cl-(S)-Ph-pzox = N-((R)-2-cloro-1-phenyletyl)-3-((S)-4-phenyl-4,5-dihydrooxazole-2-yl)pyrazine-2-carboxamide; hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione), aiming to understand through opto-structural correlations how the overall emission quantum yield (φ LLn), dissymmetry factor (glum), as well as CPL brightness can be finely tuned by changing the electronic structure and symmetry of the EuIII coordination polyhedron. [(Eu(hfa)3(S)-Bn-pybox)] displayed the largest ‖glum‖ values (0.36 in dichloromethane) for the 5D0 → 7F1 transition and the highest CPL brightness reported so far (465 M−1 cm−1 in dichloromethane) for the 5D0 → 7F2 transition. By combining the experimental photoluminescence and computational data, we were able to show that the bright CPL is a consequence of the quite high emission quantum yield in dichloromethane (41.4%), the large branching ratio of the 5D0 → 7F2 transition, and the increase of the magnetic dipole momentum contribution to the EuIII transitions owing to the low EuIII local microsymmetry. Thus, our investigation helps to provide further guidance on how the electronic structure of the complexes and the EuIII local microsymmetry can play synergistically to improve the CPL brightness of EuIII complexes. [ABSTRACT FROM AUTHOR]

The reactions of the electrophilic fluorinating agent, gaseous SF(sub)3 ions, with members of five-membered heteroaromatic compounds are described. The fluorinating agent reacts by both electron abstraction and F(sup)+ transfer with furan, thiophene, pyrrole, and alkyl-substituted derivatives producing protonated monofluorinated compounds.

Research has been conducted on meta-substituted allyl aryl ethers. The authors report that isomeric product composition and theoretical calculations of these ethers confirm the reliability of the (super)1 NMR methodology used for prediction of aromatic Claisen regioselectivity of the reactant alloxy group.

Abstract: Direct analysis of polyisoprenoids by electrospray ionization mass spectrometry (ESI–MS) often produces poor results requiring off-line time and sample-consuming derivatization techniques. We describe a simple ESI–MS approach for the direct analysis of polyisoprenoids using several dolichols and polyprenols with different chain sizes as proof-of-principle cases. Lithium iodide is used to promote cationization by intense formation of [M+Li]+ adducts. Thus, detection of polyisoprenoids with mass determination can be performed with high sensitivity (limit of detection [LOD] ∼100ρM), whereas characteristic collision-induced dissociations observed for both dolichols and polyprenols permit investigation of their structure. Using ESI(Li+)–MS and ESI(Li+)–MS/MS analysis, we screened for polyprenol products of an octaprenyl pyrophosphate synthase of Plasmodium falciparum and dolichols in a complex mixture of compounds produced by Leishmania amazonensis and P. falciparum. [Copyright &y& Elsevier]

The classical microbial strategy for depolymerization of β-mannan polysaccharides involves the synergistic action of at least two enzymes, endo-1,4-β-mannanases and β-mannosidases. In this work, we describe the first exo-β-mannanase from theGH2family, isolated from Xanthomonas axonopodis pv. citri (XacMan2A), which can efficiently hydrolyze both mannooligosaccharides and β-mannan into mannose. It represents a valuable process simplification in the microbial carbon uptake that could be of potential industrial interest. Biochemical assays revealed a progressive increase in the hydrolysis rates from mannobiose to mannohexaose, which distinguishes XacMan2A from the known GH2 β-mannosidases. Crystallographic analysis indicates that the active-site topology of XacMan2A underwent profound structural changes at the positive-subsite region, by the removal of the physical barrier canonically observed in GH2 β-mannosidases, generating a more open and accessible active site with additional productive positive subsites. Besides that, XacMan2A contains two residue substitutions in relation to typical GH2 β-mannosidases, Gly439 and Gly556, which alter the active site volume and are essential to its mode of action. Interestingly, the only other mechanistically characterized mannose-releasing exo-β-mannanase so far is from the GH5 family, and its mode of action was attributed to the emergence of a blocking loop at the negative-subsite region of a cleft-like active site, whereas in XacMan2A, the same activity can be explained by the removal of steric barriers at the positive-subsite region in an originally pocket-like active site. Therefore, the GH2 exo-β-mannanase represents a distinct molecular route to this rare activity, expanding our knowledge about functional convergence mechanisms in carbohydrate-active enzymes. [ABSTRACT FROM AUTHOR]

When exposed to stress conditions, all cells induce mechanisms resulting in an attempt to adapt to stress that involve proteins which, once activated, trigger cell responses by modulating specific signaling pathways. In this work, using a combination of pulldown assays and mass spectrometry analyses, we identified the Neurospora crassa SEB-1 transcription factor that binds to the Stress Response Element (STRE) under heat stress. Orthologs of SEB-1 have been functionally characterized in a few filamentous fungi as being involved in stress responses; however, the molecular mechanisms mediated by this transcription factor may not be conserved. Here, we provide evidences for the involvement of N. crassa SEB-1 in multiple cellular processes, including response to heat, as well as osmotic and oxidative stress. The Δseb-1 strain displayed reduced growth under these conditions, and genes encoding stress-responsive proteins were differentially regulated in the Dseb-1 strain grown under the same conditions. In addition, the SEB-1-GFP protein translocated from the cytosol to the nucleus under heat, osmotic, and oxidative stress conditions. SEB-1 also regulates the metabolism of the reserve carbohydrates glycogen and trehalose under heat stress, suggesting an interconnection between me- tabolism control and this environmental condition. We demonstrated that SEB-1 binds in vivo to the promoters of genes encoding glycogen metabolism enzymes and regulates their expression. A genome-wide transcriptional profile of the Dseb-1 strain under heat stress was determined by RNA-seq, and a broad range of cellular processes was identified that suggests a role for SEB-1 as a protein interconnecting these mechanisms. [ABSTRACT FROM AUTHOR]

Direct analysis of polyisoprenoids by electrospray ionization mass spectrometry (ESI-MS) often produces poor results requiring off-line time and sample-consuming derivatization techniques. We describe a simple ESI-MS approach for the direct analysis of polyisoprenoids using several dolichols and polyprenols with different chain sizes as proof-of-principle cases. Lithium iodide is used to promote cationization by intense formation of [M+Li]+ adducts. Thus, detection of polyisoprenoids with mass determination can be performed with high sensitivity (limit of detection [LOD] approximately 100 rhoM), whereas characteristic collision-induced dissociations observed for both dolichols and polyprenols permit investigation of their structure. Using ESI(Li+)-MS and ESI(Li+)-MS/MS analysis, we screened for polyprenol products of an octaprenyl pyrophosphate synthase of Plasmodium falciparum and dolichols in a complex mixture of compounds produced by Leishmania amazonensis and P. falciparum.