Egorov’s narrow-skulled vole (Rodentia,Arvicolinae) from the Late Pleistocene of Eastern Siberia,a North American immigrant

A comparative study of the Late Pleistocene Egorov’s narrow-skulled vole from the Indigirka River basin is performed. The taxon was previously regarded as a subspecies of Microtus (Stenocranius) gregalis (Pallas, 1779). Based on a number of morphological characters, it is shown that this vole is closer to the American species Mynomes (Vocalomys) miurus (Osgood, 1901). It is proposed that Mynomes (V.) miurus egorovi (Fejgin in Baranova et Fejgin, 1980) penetrated into northeastern Siberia during the Zyryanian glacial.     

Structural and magnetic behavior of mono- and dinuclear nickel (II) complexes of N,N′-bis-(3,5-dipiperidin-1-yl-[2,4,6]triazin-1-yl)-pyridin-2-ylmethyl-ethane-1,2-diamine

Reaction of nickel (II) perchlorate with the ligand N,N′-bis-(3,5-dipiperidin-1-yl-[2,4,6]triazin-1-yl)-pyridin-2-ylmethyl-ethane-1,2-diamine yields an octahedral Ni(II) high-spin complex 1 ([C₄₀H₅₆N₁₄Ni(H₂O)(CH₃OH)](ClO₄)₂(CH₃OH)₂) with moderate zero-field splitting (ZFS) axial distortion parameter D/k_B = 5.37 K. The ligand contributes a N4 donor set; the remaining two coordinating positions are occupied by coordinating solvents molecules. Exchange of the coordinating solvents molecules in complex 1 to thiocyanate moieties leads to formation of complex 2 ([C₄₀H₅₆N₁₄Ni(NCS)₂](CHCl)₃) with an extended parameter D/k_B = 8.80 K. The analysis of the structural and magnetic properties of complexes 1 and 2 led to the design of dinuclear complex 3 ([C₄₀H₅₆N₁₄NiN₃]₂(ClO₄)₂(CH₃OH)₂), where two azido groups were utilized as bridging ligands. The double azido bridges in complex 3 cross each other to form a rarely observed non-coplanar (N₃)₂ structure. The magnetic behavior of complex 3 reveals ferromagnetic coupling interactions characterized by J/k_B = 23.25 K, D₁/k_B = 7.90 K, D₂/k_B = 0.54 K.     

红豆杉高产细胞系快速建立和更新的新方法

目的：通过优化培养基和培养条件,建立太行红豆杉速生细胞系,为红豆杉细胞工厂化生产提供原种细胞系和繁殖技术。方法：以太行红豆杉为材料,筛选B5、WPS、MS等3种培养基和6-卞基嘌呤（6-BA）、萘乙酸（NAA）、2,4-二氯苯氧乙酸（2,4-D）等3种激素组合,采用液体、半固体、纸桥共3种培养方法继代培养并筛选高产细胞系。结果：B5＋NAA（1.0mg/L）＋6-BA（0.5mg/L）＋2,4-D（1.0mg/L）为最适愈伤组织诱导培养基,诱导率达100%;B5＋NAA（1.0～1.5mg/L）＋2,4-D（1.5～2.0mg/L）＋6-BA（0.5mg/L）为最佳继代培养基,生长量最高可达0.30g/（g·d）（鲜重）。结论：初步建立了红豆杉细胞系快速建立和繁殖新方法,用半固体培养产生初代细胞系、液体培养将细胞系同步化、纸桥培养快速繁殖细胞系,并通过检测紫杉醇含量不断更新细胞系。该细胞系体系建立方法简单,纯化速度快,易更新,产物细胞系可作为工厂化生产的原种细胞系。     

Calculation of Proteins’ Total Side-Chain Torsional Entropy and Its Influence on Protein-Ligand Interactions

Despite the high density within a typical protein fold, the ensemble of sterically permissible side-chain repackings is vast. Here, we examine the extent of this variability that survives energetic biases due to van der Waals interactions, hydrogen bonding, salt bridges, and solvation. Monte Carlo simulations of an atomistic model exhibit thermal fluctuations among a diverse set of side-chain arrangements, even with the peptide backbone fixed in its crystallographic conformation. We have quantified the torsional entropy of this native-state ensemble, relative to that of a noninteracting reference system, for 12 small proteins. The reduction in entropy per rotatable bond due to each kind of interaction is remarkably consistent across this set of molecules. To assess the biophysical importance of these fluctuations, we have estimated side-chain entropy contributions to the binding affinity of several peptide ligands with calmodulin. Calculations for our fixed-backbone model correlate very well with experimentally determined binding entropies over a range spanning more than 80 kJ/(mol·308 K).     

The permeability of highway in Gorski kotar (Croatia) for large mammals

The highway from Zagreb to Rijeka stretches 68.5 km through a wildlife core area in Gorski kotar (Croatia). It has 43 viaducts and tunnels, and one specifically constructed (100 m wide) green bridge (Dedin). One quarter of the total highway length consists of possible crossing structures. At Dedin green bridge, a total of 12,519 crossings have been recorded during 793 different days of active infrared monitors being in operation, or 15.8 crossings per day. Two monitored tunnel overpasses had 11.2 and 37.0 crossings per day, respectively, whilst 4.3 crossings occurred per day under one monitored viaduct. Of those crossings, 83.2% were by ungulates and 14.6% by large carnivores. Radio-tracked large carnivores, brown bear (Ursus arctos), grey wolf (Canis lupus) and Eurasian lynx (Lynx lynx), expressed strong positive selection for tunnels and viaducts, whilst avoiding small underpasses or bridges. Selection for the use of Dedin green bridge was equal to its availability. We conclude that this green bridge, constructed as a measure to mitigate the negative effects of the studied highway, served its purpose acceptably. Territorial and dispersing radio-tracked large carnivores crossed the highway 41 times, using both sides of the highway as parts of their home ranges. Overall, the highway in Gorski kotar does not seem to be a barrier. This demonstrates that it is possible to maintain habitat connectivity during the process of planning the highway route.     

Aqua bridge cleavage and metal ion extrusion by thiocyanate anions in a dicopper complex

Reaction of the imidazolidinyl phenolate-based ligand, H₃L [(2-(2′-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine)] with Cu(ClO₄)₂·6H₂O produces an aqua-bridged cationic reactant complex [Cu₂(μ-H₂O)(μ-L)][ClO₄]·1.5H₂O (1·1.5H₂O). Solution phase interaction of 1·1.5H₂O with SCN⁻ anions in 1:1 molar ratio leads to [Cu₂(μ-L)(NCS)]·2H₂O (2·2H₂O) that does not possess anymore the reactive aqua bridge but instead a terminal SCN⁻ anion coordinated only to one Cu^II ion. Whereas in 1:2 molar ratio, partial extrusion of the Cu^II ions takes place to generate in situ [Cu(NCS)₃(OH₂)]⁻ anions. These complex anions then quantitatively replace anions in 1·1.5H₂O via ‘anion metathesis’ and concurrently remove the aqua bridge by coordination of linear MeCN to one of the Cu^II ions to give [Cu₂(μ-L)(CH₃CN)][Cu(NCS)₃(OH₂)] (3). The literature unknown [Cu(NCS)₃(OH₂)]⁻ anion forms an intimate H-bonded assembly with the cationic part of 3 to yield a novel [Cu₃] isosceles triangle. The precursor complex is known as antiferromagnetic whereas in 2·2H₂O, the Cu^II (S = 1/2) ions in a dinuclear entity exhibit ferromagnetic interactions (J/k_B = +15.0 K and g = 2.22) to yield an S_T = 1 spin ground state in good agreement with the M versus H data below 8 K.     

Cyanato bridged binuclear nickel(II) and copper(II) complexes with pyridylpyrazole ligand: Synthesis, structure and magnetic properties

Binuclear cyanate bridged nickel(II) complex [Ni(L)(NCO)]₂(PF₆)₂ (1) and copper(II) complex [Cu(L)(NCO)]₂(PF₆)₂ (2), where L is N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)aminomethylpyridine, a tetradentate N₄-coordinated ligand have been synthesized and characterized by physicochemical method. The structures of complexes 1 and 2 have been studied by single crystal X-ray diffraction analysis. The structure analysis reveals that both nickel(II) and copper(II) center are coordinated in distorted octahedral fashion and coordination mode of cyanate ligand is end-to-end (μ-1,3) for complex 1 but it is double end-on (μ-1,1) mode for complex 2. The variable temperature magnetic susceptibility data, measured from 2 to 300 K, show weak antiferromagnetic interaction with J value −6.2(1) cm⁻¹ for complex 1, whereas complex 2 has very weak ferromagnetic interaction with J value +0.5(1) cm⁻¹.     

An analysis of temperature adaptation in cold active, mesophilic and thermophilic Bacillus α-amylases

A comparative biochemical and structural study was performed on a cold active α-amylase from Bacillus cereus (BCA) and two well-known homologous mesophilic and thermophilic α-amylases from Bacillus amyloliquefaciens (BAA) and Bacillus licheniformis (BLA). In spite of a high degree of sequence and structural similarity, drastic variations were found for T_opt as 50, 70 and 90 °C for BCA, BAA and BLA, respectively. The half-lives of thermoinactivation were 1 and 9 min for BCA and BAA at 80 °C respectively, whilst there was no inactivation for BLA at this temperature. Thermodynamic studies on inactivation process suggested that lower thermostability of BCA is due to lower inactivation slope of the Arrhenius plots and subsequently, lower E_a and ΔH^#. Increased K_m and accessible surface area for catalytic residues along with a decreased number of internal interactions in this region in BCA compared to BLA suggest that BCA substrate-binding site might be temperature sensitive and is probably more flexible. On the other hand, fewer ion pairs, destructive substitutions and disruption of aromatic interaction networks in structurally critical regions of Bacillus α-amylases result in a severe decrease in BCA thermostability compared to its mesophilic and thermophilic homologues.     

Common structural traits across pathogenic mutants of the human prion protein and their implications for familial prion diseases

Human (Hu) familial prion diseases are associated with about 40 point mutations of the gene coding for the prion protein (PrP). Most of the variants associated with these mutations are located in the globular domain of the protein. We performed 50 ns of molecular dynamics for each of these mutants to investigate their structure in aqueous solution. Overall, 1.6 μs of molecular dynamics data is presented. The calculations are based on the AMBER(parm99) force field, which has been shown to reproduce very accurately the structural features of the HuPrP wild type and a few variants for which experimental structural information is available. The variants present structural determinants different from those of wild-type HuPrP and the protective mutation HuPrP(E219K-129M). These include the loss of salt bridges in α₂-α₃ regions and the loss of π-stacking interactions in the β₂-α₂ loop. In addition, in the majority of the mutants, the α₃ helix is more flexible and Y169 is more solvent exposed. The presence of similar traits in this large spectrum of mutations hints to a role of these fingerprints in their known disease-causing properties. Overall, the regions most affected by disease-linked mutations in terms of structure and/or flexibility are those involved in the pathogenic conversion to the scrapie form of the protein and in the interaction with cellular partners. These regions thus emerge as optimal targets for antibody- and ligand-binding studies.     

Structure–function relationships of the peptide Paulistine: A novel toxin from the venom of the social wasp Polybia paulista

Background

The peptide Paulistine was isolated from the venom of wasp Polybia paulista. This peptide exists under a natural equilibrium between the forms: oxidised — with an intra-molecular disulphide bridge; and reduced — in which the thiol groups of the cysteine residues do not form the disulphide bridge. The biological activities of both forms of the peptide are unknown up to now.

Methods

Both forms of Paulistine were synthesised and the thiol groups of the reduced form were protected with the acetamidemethyl group [Acm-Paulistine] to prevent re-oxidation. The structure/activity relationships of the two forms were investigated, taking into account the importance of the disulphide bridge.

Results

Paulistine has a more compact structure, while Acm-Paulistine has a more expanded conformation. Bioassays reported that Paulistine caused hyperalgesia by interacting with the receptors of lipid mediators involved in the cyclooxygenase type II pathway, while Acm-Paullistine also caused hyperalgesia, but mediated by receptors involved in the participation of prostanoids in the cyclooxygenase type II pathway.

Conclusion

The acetamidemethylation of the thiol groups of cysteine residues caused small structural changes, which in turn may have affected some physicochemical properties of the Paulistine. Thus, the dissociation of the hyperalgesy from the edematogenic effect when the actions of Paulistine and Acm-Paulistine are compared to each other may be resulting from the influence of the introduction of Acm-group in the structure of Paulistine.

General significance

The peptides Paulistine and Acm-Paulistine may be used as interesting tools to investigate the mechanisms of pain and inflammation in future studies.