Arsenic accumulation and thiol status in lichens exposed to As(V) in controlled conditions

Thalli of epiphytic lichen Hypogymnia physodes (L.) Nyl. and terricolous Cladonia furcata (Huds.) Schrad., collected from an area with background arsenic concentrations, were exposed to 0, 0.1, 1 and 10 μg mL⁻¹ arsenate (As(V)) solutions for 24 h. After exposure they were kept in the metabolically active state for 0, 24 and 48 h in a growth chamber. In the freeze dried samples glutathione (GSH), glutathione disulphide (GSSG), cysteine (Cys) and cystine were analysed and induction of phytochelatin (PC) synthesis measured by reversed-phase high-performance liquid chromatography in combination with fluorescence detection or UV spectrometry. Total arsenic content in thalli was measured by instrumental neutron activation analysis (INAA). In H. physodes, which contained higher amounts of arsenic compared to C. furcata, total glutathione content significantly decreased in samples exposed to 10 μg mL⁻¹ As(V), whereas in C. furcata a significant increase was observed. In both species PC synthesis was induced in thalli exposed to 10 μg mL⁻¹.     

Binuclear manganese(III) complexes of an unsymmetric pyrazolate-based compartmental ligand with hard donor set

The synthesis, crystal structure and magnetic properties of manganese(III) binuclear complexes [Mn^III₂(L-3Н)₂(CH₃ОH)₄]·2CH₃ОH (1) and [Mn^III₂(L-3Н)₂(Py)₄]·2Py (2) (L = 3-[(1E)-N-hydroxyethanimidoyl]-4-methyl-1H-pyrazole-5-carboxylic acid) are reported. The ligand contains two distinct donor compartments formed by the pyrazolate-N and the oxime or the carboxylic groups. The complexes were characterized by X-ray single crystal diffraction, revealing that both 1 and 2 consist of dinuclear units in which the two metal ions are linked by double pyrazolate bridges with a planar {Mn₂N₄} core. Cryomagnetic measurements show antiferromagnetic interaction with g = 1.99, J = −3.6 cm⁻¹, Θ = −2.02 K for 1 and g = 2.00, J = −3.7 cm⁻¹, Θ = 1.43 K for 2.     

Limited validity of group additivity for the folding energetics of the peptide group

The principle of group additivity is a standard feature of analyses of the energetics of protein folding, but it is known that it may not always be valid for the polar peptide group. The neighboring residue effect shows that group additivity is not strictly valid for a heteropeptide. We show here that group additivity fails seriously for peptide groups close to either peptide end, even for a homopeptide that has blocked end groups with no formal charges involved. The failure of group additivity is caused by the electrostatic character of the solvation of peptide polar groups and is illustrated with values of the electrostatic solvation free energy (ESF) calculated by DelPhi. Solvation free energies and enthalpies are known experimentally for monoamides and are often used to model the solvation of peptide groups, but ESF results show that monoamide values are very different from those of peptide groups. A main cause of the difference is that peptide solvation depends on the dipole-dipole interactions made between adjacent peptide groups, which vary with peptide conformation. Ligands that interact with the peptide backbone by an electrostatic mechanism could show a similar peptide end effect, and hydrogen exchange results from the literature confirm that exchange rates are position-dependent close to peptide ends.     

Role of the cellular prion protein in oligodendrocyte precursor cell proliferation and differentiation in the developing and adult mouse CNS

There are numerous studies describing the signaling mechanisms that mediate oligodendrocyte precursor cell (OPC) proliferation and differentiation, although the contribution of the cellular prion protein (PrP(c)) to this process remains unclear. PrP(c) is a glycosyl-phosphatidylinositol (GPI)-anchored glycoprotein involved in diverse cellular processes during the development and maturation of the mammalian central nervous system (CNS). Here we describe how PrP(c) influences oligodendrocyte proliferation in the developing and adult CNS. OPCs that lack PrP(c) proliferate more vigorously at the expense of a delay in differentiation, which correlates with changes in the expression of oligodendrocyte lineage markers. In addition, numerous NG2-positive cells were observed in cortical regions of adult PrP(c) knockout mice, although no significant changes in myelination can be seen, probably due to the death of surplus cells.     

Analysis of N-glycosylation in maize cytokinin oxidase/dehydrogenase 1 using a manual microgradient chromatographic separation coupled offline to MALDI-TOF/TOF mass spectrometry

Cytokinin oxidase/dehydrogenase (CKO; EC 1.5.99.12) irreversibly degrades the plant hormones cytokinins. A recombinant maize isoenzyme 1 (ZmCKO1) produced in the yeast Yarrowia lipolytica was subjected to enzymatic deglycosylation by endoglycosidase H. Spectrophotometric assays showed that both activity and thermostability of the enzyme decreased after the treatment at non-denaturing conditions indicating the biological importance of ZmCKO1 glycosylation. The released N-glycans were purified with graphitized carbon sorbent and analyzed by MALDI-TOF MS. The structure of the measured high-mannose type N-glycans was confirmed by tandem mass spectrometry (MS/MS) on a Q-TOF instrument with electrospray ionization. Further experiments were focused on direct analysis of sugar binding. Peptides and glycopeptides purified from tryptic digests of recombinant ZmCKO1 were separated by reversed-phase chromatography using a manual microgradient device; the latter were then subjected to offline-coupled analysis on a MALDI-TOF/TOF instrument. Glycopeptide sequencing by MALDI-TOF/TOF MS/MS demonstrated N-glycosylation at Asn52, 63, 134, 294, 323 and 338. The bound glycans contained 3-14 mannose residues. Interestingly, Asn134 was found only partially glycosylated. Asn338 was the sole site to carry large glycan chains exceeding 25 mannose residues. This observation demonstrates that contrary to a previous belief, the heterologous expression in Y. lipolytica may lead to locally hyperglycosylated proteins.     

Insecticide and acaricide molecules and/or combinations to prevent pet infestation by ectoparasites

External antiparasitic drugs used in cats and dogs have evolved in terms of active ingredients but also regarding formulations. Old chemical groups have been supplanted by phenylpyrazoles, neonicotinoids, oxadiazines, spinosyns or others which are entering the veterinary market. In addition to insecticides-acaricides, insect and mite growth inhibitors (IGRs) have emerged. These IGRs are used in animals or in the environment, either alone or in combination with insecticides-acaricides. The notion of antiparasitic treatment has evolved to the concept of prevention of ectoparasite infestation but also of transmitted diseases through the introduction of formulations providing long-lasting activity. At the same time, ease-of-use has been improved with the development of spot-on formulations. Progress has also been achieved through the development of antiparasitic drugs providing control of both external and internal parasites.     

Long-range correlations improve understanding of the influence of network structure on contact dynamics

Models of infectious diseases are characterized by a phase transition between extinction and persistence. A challenge in contemporary epidemiology is to understand how the geometry of a host’s interaction network influences disease dynamics close to the critical point of such a transition. Here we address this challenge with the help of moment closures. Traditional moment closures, however, do not provide satisfactory predictions close to such critical points. We therefore introduce a new method for incorporating longer-range correlations into existing closures. Our method is technically simple, remains computationally tractable and significantly improves the approximation’s performance. Our extended closures thus provide an innovative tool for quantifying the influence of interaction networks on spatially or socially structured disease dynamics. In particular, we examine the effects of a network’s clustering coefficient, as well as of new geometrical measures, such as a network’s square clustering coefficients. We compare the relative performance of different closures from the literature, with or without our long-range extension. In this way, we demonstrate that the normalized version of the Bethe approximation-extended to incorporate long-range correlations according to our method-is an especially good candidate for studying influences of network structure. Our numerical results highlight the importance of the clustering coefficient and the square clustering coefficient for predicting disease dynamics at low and intermediate values of transmission rate, and demonstrate the significance of path redundancy for disease persistence.