The 1.2 Å crystal structure of an E. coli tRNA acceptor stem microhelix reveals two magnesium binding sites

tRNA identity elements assure the correct aminoacylation of tRNAs by the cognate aminoacyl-tRNA synthetases. tRNA^Ser belongs to the so-called class II system, in which the identity elements are rather simple and are mostly located in the acceptor stem region, in contrast to ‘class I’, where tRNA determinants are more complex and are located within different regions of the tRNA.The structure of an Escherichia coli tRNA^Ser acceptor stem microhelix was solved by high resolution X-ray structure analysis. The RNA crystallizes in the space group C2, with one molecule per asymmetric unit and with the cell constants a = 35.79, b = 39.13, c = 31.37 Å, and β = 111.1°. A defined hydration pattern of 97 water molecules surrounds the tRNA^Ser acceptor stem microhelix. Additionally, two magnesium binding sites were detected in the tRNA^Ser aminoacyl stem.     

New oligo-/poly-meric forms for MX:dpex (1:1) complexes (M = Cu, Ag; X = (pseudo-)halide; dpex = Ph2E(CH2)xEPh2, E = (P), As; x = 1, 2)

Single-crystal X-ray structural characterizations of MX:dpam (1:1) (‘dpam’ = Ph₂AsCH₂AsPh₂) are reported for MX = AgCl, Br; CuI, CN/Cl (all isomorphous) and AgI, AgSCN, CuSCN arrays, all being of the novel form [(μ-X){M(μ-X)(As-dpam-As′)₂M′}]_∞, essentially the familiar M(E-dpem-E′)₂M′ binuclear array with both ‘bridging’ and (linking) ‘terminal’ (pseudo-)halides involved in the polymer. A different arrangement of bridging and linking entities is found with AgX:dpae (1:1)_2(∞|∞), X = Br, NCO, ‘dpae’ = Ph₂As(CH₂)₂AsPh₂, now comprising [M(μ-X)₂(As-dpae-As)M] kernels linked by As-dpae-As′, while in the thiocyanate analogue units are linked by the dpae ligands into a two-dimensional web. Synthetic procedures for all adducts have been reported. All compounds have been characterized both in solution (¹H, ¹³C, ³¹P NMR, ESI MS) and in the solid state (IR).     

Synthesis and structural characterization of adducts of silver(I) carboxylate salts AgX (X = CF3COO, CH3COO) with ER3 (E = P, As; R = Ph, cy, o-tolyl) and oligodentate aromatic bases derivative of 2,2′-bipyridyl, L, AgX:PR3:L (1:1:1)

Twenty-one adducts of the form AgX:ER₃:L (1:1:1) (X = CF₃COO (‘tfa’), CH₃COO (‘ac’), E = P, As; R = Ph, cy, o-tolyl; L = 2,2′-bipyridyl (‘bpy’)-based ligand) have been synthesized and characterized by analytical, spectroscopic (IR, far-IR, ¹H, ¹⁹F and ³¹P NMR) and single crystal X-ray diffraction studies. The resulting complexes are predominantly of the form [(R₃E)AgL]⁺X⁻, with a trigonal EAgN₂ coordination environment, the planarity of which may be perturbed by the approach of anion or solvent. The carboxylate anions have been found to be uni-, or semi-bidentate, or also completely ionic, as in the complexes [Ag(PPh₃)(bpy)(H₂O)](tfa) and [Ag(PPh₃)(dpk · H₂O)](tfa) (‘dpk · H₂O’ = bis(2-pyridyl)ketone (hydrated)). The complexes Agac:PPh₃:dpa (1:1:1) and Agac:P(o-tol)₃:dpa:MeCN (1:1:1:1) are dinuclear, with bridging unidentate acetate and terminal unidentate dpa (‘dpa’ = bis(2-pyridyl)amine).     

The complete mitochondrial genome of the leafminer Liriomyza sativae (Diptera: Agromyzidae): great difference in the A+T-rich region compared to Liriomyza trifolii

The complete mitochondrial genome sequence of Liriomyza sativae Blanchard (15,551 bp) was determined and analyzed in this study. The circular genome contained 37 genes including 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and an A + T-rich region. The initiation codons of COI and ND1 were ‘ATCA’ and ‘GTG’, respectively. ND2 gene used the truncated termination codon ‘T’. All the tRNA genes had the typical cloverleaf secondary structures except for tRNA^Ser(AGN) gene, which was found with the absence of a DHU arm. In addition, a tRNA-like secondary structure (tRNA^Met) was found in the A + T-rich region. The great difference was that the length of L. sativae A + T-rich region was 597 bp shorter than that of Liriomyza trifolii (Burgess). Meanwhile, some minor differences such as ‘TATA’ block were also observed in L. sativae in contrast to ‘TACA’ block in L. trifolii. There were also some essential structure elements such as ‘TATA’ block, ‘G(A)_nT’ block, poly-T stretch and stem-and-loop structure in the A + T-rich region of L. sativae mitochondrial genome.     

Quality of T-cells after stimulation with leukemia-derived dendritic cells (DC) from patients with acute myeloid leukemia (AML) or myeloid dysplastic syndrome (MDS) is predictive for their leukemia cytotoxic potential

Myeloid leukemic cells can differentiate into leukemia-derived dendritic cells (DC_leu), presenting known/unknown leukemic-antigens. Induced anti-leukemic T-cell-responses are variable. To further elicit DC/DC_leu-induced T-cell-response-patterns we performed (functional)flow-cytometry/fluorolysis-assays before/after mixed lymphocyte cultures (MLC) of matched (allogeneic) donor-T-cells (n = 6), T-cells prepared at relapse after stem cell transplantation (n = 4) or (autologous) patients’-T-cells (n = 7) with blast-containing-mononuclear-cells (‘MNC’) or DC_leu-containing DC (‘DC’). Compared to ‘MNC’ ‘DC’ were better mediators of anti-leukaemic T-cell-activity, although not in every case effective. We could define cut-off proportions of mature DC, DC_leu, proliferating, CD4⁺, CD8⁺ and non-naive T-cells after ‘MNC’- or ‘DC’-stimulation, that were predictive for an anti-leukemic-activity of stimulated T-cells as well as a response to immunotherapy. Interestingly especially ratios >1 of CD4:CD8 or CD45RO:CD45RA T-cells were predictive for anti-leukemic function after DC-stimulation.In summary the composition and quality of DC and T-cells after a MLC-stimulating-phase is predictive for a successful ex-vivo and in-vivo anti-leukemic response, especially with respect to proportions of proliferating, CD4⁺ and CD45RO⁺ T-cells. Successful cytotoxicity and the development of a T-cell-memory after ‘DC’-stimulation could be predictive for the clinical course of the disease and may pave the way to develop adoptive immunotherapy, especially for patients at relapse after SCT.     

Molecular and pharmacological characterization of zebrafish ‘contractile’ and ‘inhibitory’ prostanoid receptors

Prostanoids comprising prostaglandins (PGs) and thromboxanes (TXs) have been shown to play physiological and pathological roles in zebrafish. However, the molecular basis of zebrafish prostanoid receptors has not been established. Here, we demonstrate that there exist at least five ‘contractile’ (Ca²⁺-mobilizing) and one ‘inhibitory’ (G_i-coupled) prostanoid receptors in zebrafish; five ‘contractile’ receptors consisting of two PGE₂ receptors (EP1a and EP1b), two PGF_2α receptors (FP1 and FP2), and one TXA₂ receptor TP, and one ‘inhibitory’ receptor, the PGE₂ receptor EP3. [³H]PGE₂ specifically bound to the membranes of cells expressing zebrafish EP1a, EP1b and EP3 with a Kd of 4.8, 1.8 and 13.6 nM, respectively, and [³H]PGF_2α specifically bound to the membranes of cells expressing zebrafish FP1 and FP2, with a Kd of 6.5 and 1.6 nM, respectively. U-46619, a stable agonist for human and mouse TP receptors, significantly increased the specific binding of [³⁵S]GTPγS to membranes expressing the zebrafish TP receptor. Upon agonist stimulation, all six receptors showed an increase in intracellular Ca²⁺ levels, although the increase was very weak in EP1b, and pertussis toxin abolished only the EP3-mediated response. Zebrafish EP3 receptor also suppressed forskolin-induced cAMP formation in a pertussis toxin-sensitive manner. In association with the low structural conservation with mammalian receptors, most agonists and antagonists specific for mammalian EP1, EP3 and TP failed to work on each corresponding zebrafish receptor. This work provides further insights into the diverse prostanoid actions mediated by their receptors in zebrafish.     

Syntheses, structures and vibrational spectroscopy of some 1:2 and 1:3 adducts of silver(I) oxyanion salts with pyridine and piperidine bases containing non-coordinating 2(,6)-substituents

Synthetic, single crystal X-ray structural characterizations and vibrational spectroscopic studies are recorded for a number of adducts of 1:2 stoichiometry of silver(I) oxyanion salts for oxyanions of differing basicity (perchlorate, nitrate, carboxylate (as trifluoroacetate (≡‘tfa’))), with a variety of pyridine (≡‘py’) or piperidine (≡‘pip’) bases hindered in the 2- (and, sometimes, 6-) position(s) by methyl or non-coordinating functionalities of other types, the ligands employed being 2-methylpyridine (‘2mp’), 2,6-dimethylpyridine (‘lut’), 2,4,6-trimethylpyridine (‘coll’), quinoline (‘quin’), 2,2,6,6-tetramethylpiperidine (‘tmp’), 2-amino-,6-methylpyridine (‘nmp’), 2-methoxypyridine (‘mop’) and 2-cyanomethylpyridine (‘pcn’); studies are also recorded of adducts with the parent, ‘py’, base and with 4-cyanopyridine (‘cnp’). In the majority of the complexes, the NAgN motif predominates, as might be expected, variously distorted from linearity in response to changes in (competing) basicities of the nitrogen base and any nearby anion or solvent molecule; an unusual variation is found in the highly hindered tmp/tfa adduct which is a monohydrate with interacting water displacing the rather basic anion, the converse being the case in the corresponding nitrate, also a monohydrate. With the less-hindered base mpy, both nitrate and trifluoroacetate are binuclear, with O and OCO bridges corresponding to centrosymmetric four- and eight-membered rings, respectively; the quin/nitrate adduct is more complex, also binuclear but with bis(chelating) nitrate. AgNO₃:py (1:3) is found to be binuclear, while with Agtfa/py, a 3:2 adduct [Ag(py)₂][Ag₂(tfa)₃]_(∞|∞) is found with a novel, polymeric, strongly interacting anion. A further pair of 1:3 adducts, AgNO₃:2np (2np = 2-aminopyridine) and Agtfa:nmp, both mononuclear [AgL₃]⁺X⁻ are described, differing in the modes of interaction of silver with the three N-bases. In all simple NAgN systems with aromatic ligands, the pair of ligand ‘planes’ is disposed quasi-parallel.The far-IR spectra of [AgL₂]Y (L = lut, coll; Y = ClO₄, NO₃, tfa) and of [Ag(py)_n](ClO₄) (n = 2,4) have been recorded and the ν(AgN) bands assigned in the range 80-240 cm⁻¹. For the L = lut, coll complexes, there is a clear trend of decreasing ν(AgN) following increasing r(AgN) as the interaction with the counterion increases along the series Y = ClO₄, NO₃, tfa.     

Effect of CDP-choline on age-dependent modifications of energy- and glutamate-linked enzyme activities in synaptic and non-synaptic mitochondria from rat cerebral cortex

The effect of aging and CDP-choline treatment (20 mg kg⁻¹ body weight i.p. for 28 days) on the maximal rates (V_max) of representative mitochondrial enzyme activities related to Krebs’ cycle (citrate synthase, α-ketoglutarate dehydrogenase, malate dehydrogenase), glutamate and related amino acid metabolism (glutamate dehydrogenase, glutamate–oxaloacetate- and glutamate–pyruvate transaminases) were evaluated in non-synaptic and intra-synaptic “light” and “heavy” mitochondria from frontal cerebral cortex of male Wistar rats aged 4, 12, 18 and 24 months.     

Characterization of the complete mitochondrial genome of Tryporyza incertulas, in comparison with seven other Pyraloidea moths

The complete 15,223-bp mitochondrial genome (mitogenome) of Tryporyza incertulas (Walker) (Lepidoptera: Pyraloidea: Crambidae) was determined, characterized and compared with seven other species of superfamily Pyraloidea. The order of 37 genes was typical of insect mitochondrial DNA sequences described to date. Compared with other moths of Pyraloidea, the A + T biased (77.0%) of T. incertulas was the lowest. Eleven protein-coding genes (PCGs) utilized the standard ATN, but cox1 used CGA and nad4 used AAT as the initiation codons. Ten protein-coding genes had the common stop codon TAA, except nad3 having TAG as the stop codon, and cox2, nad4 using T, TA as the incomplete stop codons, respectively. All of the tRNA genes had typical cloverleaf secondary structures except trnS1(AGN), in which the dihydrouridine (DHU) arm did not form a stable stem-loop structure. There was a spacer between trnQ and nad2, which was common in Lepidoptera moths. A 6-bp motif ‘ATACTA’ between trnS2(UCN) and nad1, a 7-bp motif “AGC(T)CTTA” between trnW and trnC and a 6-bp motif “ATGATA” of overlapping region between atp8 and atp6 were found in Pyraloidea moths. The A + T-rich region contained an ‘ATAGT(A)’-like motif followed by a poly-T stretch. In addition, two potential stem-loop structures, a duplicated 19-bp repeat element, and two microsatellites ‘(TA)₁₂’ and ‘(TA)₉’ were observed in the A + T-rich region of T. incertulas mitogenome. Finally, the phylogenetic relationships of Pyraloidea species were constructed based on amino acid sequences of 13 PCGs of mitogenomes using Bayesian inference (BI) and maximum likelihood (ML) methods. These molecular-based phylogenies supported the morphological classification on relationships within Pyraloidea species.     

Synthesis and structural characterization of adducts of silver(I) perchlorate with PR3 (R = Ph, cy, o-tolyl) and oligodentate aromatic bases derivative of 2,2′-bipyridyl, L, AgClO4:PR3:L (1:1:1)

Ten novel adducts of the form AgClO₄:PR₃:L (1:1:1) (R = Ph, cy, o-tolyl; L = 2,2′-bipyridyl (‘bpy’), 2,2′-biquinoline (‘bq’), bis(2-pyridyl)amine (‘dpa’), bis(2-picolyl)amine (‘dpca’)) have been synthesized and characterized by analytical, spectroscopic (IR, far-IR, ¹H and ³¹P NMR) and single crystal X-ray diffraction studies. The solid state molecular structures show that the complexes predominantly take the form [(R₃P)AgL]⁺X⁻, with a trigonal PAgN₂ coordination environment, where the approach of the anion or the solvent may perturb the planarity of the silver environment. The ClO₄ anion shows uni- or semi-bidentate coordination, except in the complexes AgClO₄:PR₃:dpca (1:1:1) (R = Ph and o-tolyl), where the anion remains uncoordinated and the dpca donor is a three-coordinate pincer-like ligand.     

Exploring the relationship between groundwater geochemical factors and denitrification potentials on a dairy farm in southeast Ireland

Nitrate (NO₃⁻) loss from agriculture to shallow groundwater and transferral to sensitive aquatic ecosystems is of global concern. Denitrifying bioreactor technology, where a solid carbon (C) reactive media intercepts contaminated groundwater, has been successfully used to convert NO₃⁻ to di-nitrogen (N₂) gas. One of the challenges of groundwater remediation research is how to track denitrification potential spatially and temporally within reactive media and subsoil. First, using δ¹⁵N/δ¹⁸O isotopes, eight wells were divided into indicative transformational processes of ‘nitrification’ or ‘denitrification’ wells. Then, using N₂/argon (Ar) ratios these wells were divided into ‘low denitrification potential’ or high denitrification potential’ categories. Secondly, using falling head tests, the saturated hydraulic conductivity (K_sat) in each well was estimated, creating two groups of ‘slow’ (0.06 m day⁻¹) and ‘fast’ (0.13 m day⁻¹) wells, respectively. Thirdly, two ‘low denitrification potential’ wells (one fast and one slow) with high NO₃⁻ concentration were amended with woodchip to enhance denitrification. Water samples were retrieved from all wells using a low flow syringe to avoid de-gassing and analysed for N₂/Ar ratio using membrane inlet mass spectrometry. Results showed that there was good agreement between isotope and chemical (N₂/Ar ratio and dissolved organic C (DOC)) and physio-chemical (dissolved oxygen, temperature, conductivity and pH) parameters. To explain the spatial and temporal distribution of NO₃⁻ and other parameters on site, the development of predictive models using the available datasets for this field site was examined for NO₃⁻, Cl⁻, N₂/Ar and DOC. Initial statistical analysis was directed towards the testing of the effect of woodchip amendment. The analysis was formulated as a repeated measures analysis of the factorial structure for treatment and time. Nitrate concentrations were related to K_sat and water level (p < 0.0001 and p = 0.02, respectively), but did not respond to woodchip addition (p = 0.09). This non-destructive technique allows elucidation of denitrification potential over time and could be used in denitrifying bioreactor technology to assess denitrification hotspots in reactive media, while developing a NO₃⁻ spatial and temporal predictive model for bioreactor site specific conditions.     

Heterobimetallic M/Zn (M = Cu, Ni) complexes with open-chain N- and N,O-ligands: Template synthesis from metal powders and supramolecular crystal structures

A series of new heterometallic Cu^IIZn^II and Ni^IIZn^II complexes with N- and N,O open-chain multidentate ligands (L¹ = 4,6,6-trimethyl-1,9-diamino-3,7-diazanon-3-ene; L² = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3.3.1]nonane; L³ = 1,15-dihydroxy-7,9,9-trimethyl-3,6,10,13-tetraazapentadec-6-ene and L⁴ = 1-hydroxy-9-oxy-4,6,6-trimethyl-3,7-diazanon-3-ene) have been prepared through the “direct template synthesis” approach, which is a combination of classical template reactions of amines with acetone/formaldehyde and the “direct synthesis” method based on using elemental metals as starting materials. There is a significant decrease in the reaction time when the “direct synthesis” method is used compared to the conventional template condensation methods. X-ray crystallographic analyses of the complexes with the general formula M(L)ZnX₄ and [CuL⁴ZnCl₃]₂ (M = Cu²⁺, Ni²⁺; L = L¹-L³; X = Cl⁻, NCS⁻) reveal the presence of long intermolecular distance interactions, such as semi-coordination, S?S and H-bonding, in their crystal organization.     

Application of vibrational spectroscopy in the quality assessment of Buchu oil obtained from two commercially important Agathosma species (Rutaceae)

Quality assessment of natural raw materials and derived consumer products is often done using conventional analytical techniques such as liquid and gas chromatography which are expensive and time consuming. This paper reports on the use of vibrational spectroscopy techniques as possible alternatives for the rapid and inexpensive assessment of the quality of ‘buchu oil’ obtained from two South African species; Agathosma betulina and Agathosma crenulata belonging to the Rutaceae family. Samples of A. betulina (55) and A. crenulata (16) were collected from different natural localities and cultivation sites in South Africa. The essential oil was obtained by hydrodistillation and scanned on Near infrared (NIR), mid infrared (MIR) and Raman spectrometers. The spectral data obtained was processed using chemometric techniques and orthogonal partial least squares discriminant analysis (OPLS-DA) was used to clearly differentiate between A. betulina and A. crenulata. The OPLS-DA technique also proved to be a useful tool to identify wave regions that contain biomarkers (peaks) that contributed to the separation of the two species. The three spectroscopy techniques were also evaluated for their ability to accurately predict the percentage composition of seven major compounds that occur in A. betulina ‘buchu’ oil. Using GC–MS reference data, calibration models were developed for the MIR, NIR and Raman spectral data to predict/profile the major compounds in ‘buchu oil’. A comparison of the three spectroscopy techniques showed that MIR together with PLS algorithms produced the best model (R²X = 0.96; R²Y = 0.88 and Q²Ycum = 0.85) for the quantification of six of the seven major oil constituents. The MIR model showed high predictive power for pseudo-diosphenol (R² = 0.97), isomenthone (R² = 0.97), menthone (R² = 0.90), limonene (R² = 0.91), pulegone (R² = 0.96) and diosphenol (R² = 0.85). These results illustrate the potential of MIR spectroscopy as a rapid and inexpensive alternative to predict the major compounds in buchu oil.     

The structural definition of adducts of stoichiometry MX:dpex (2:3)(∞), M = Cu, Ag, X = simple anion, dpex = Ph2E(CH2)xEPh2, E = P, As

Single crystal X-ray structural characterizations are recorded for a number of adducts of MX:dpex (2:3) stoichiometry (MX = simple univalent copper or silver salt; dpex = Ph₂E(CH₂)_xEPh₂ (E = P, As)). CuX:dppe (2:3) (X = Cl, Br, I, CN) are binuclear [(dppe-P,P′)CuX(P-dppe-P′)CuX(P,P′-dppe)], all centrosymmetric. AgX:dpex (2:3) (dpex = ‘dpae’ (Ph₂As(CH₂)₂AsPh₂), X = Br, F₃CCO₂ (= ‘tfa’), F₃CSO₃ (≡ ‘tfs’); dpex = ‘dpape’ (Ph₂As(CH₂)₂PPh₂), X = CN, SCN, OClO₃) are one-dimensional polymers ?-E′)₁AgX(E-dpex-E′)₂-AgX(E-dpex-E′)₁AgX?, P, As sites scrambled in the latter. AgNO₃:dpam (2:3) is also a one-dimensional polymer, ?AgO·NO·OAg(As-dpam-As)AgO·NO·OAg? (‘dpam’ ≡ Ph₂As(CH₂)₂AsPh₂). AgX:dpae (2:3) (X = I, CN, ClO₄, NO₃) and AgX:dpape (2:3) (X = Br, I, NO₃) are two-dimensional polymers with large 30-membered macrocyclic rings; similar webs are found for dppx ligands in AgOH:dppb (2:3) and AgNCO, Agtfa:dpph (2:3) with 42- and 54-membered rings. Complexes AgX:dpape (1:3) (X = Cl, Br) are defined as mono-nuclear [XAg(Ph₂P(CH₂)₂AsPh₂)₃] arrays, the unidentate ligands predominantly P-bound. Synthetic procedures for the adducts are reported, selected compounds being characterized both in solution (¹H, ³¹P NMR, ESI MS) and in the solid state (IR).     

Competitive abilities of invasive Lagarosiphon major and native Ceratophyllum demersum in monocultures and mixed cultures in relation to experimental sediment dredging

Competitive abilities of Lagarosiphon major (Ridley) Moss (invasive in Belgium) and native Ceratophyllum demersum L. were assessed experimentally in relation to sediment dredging. We mimicked these conditions by taking undisturbed sediment (‘before dredging’ treatment) and by using restored sediment where the uppermost nutrient rich top layer was removed (‘after dredging’ treatment). Both the species were allowed to grow for seven weeks in monocultures and mixed cultures at different planting densities. Overall, invasive L. major performed better than native C. demersum independent of the characteristics of the growth environment. L. major achieved a higher relative growth rate (RGR) in both treatments based on total length (0.17-0.21 week⁻¹) and weight (0.10-0.19 week⁻¹) compared to C. demersum (length: 0.04-0.07 week⁻¹; weight: 0.03-0.17 week⁻¹). The better performance of L. major was due to a high plasticity under stressful conditions of low free CO₂ and high pH. Intraspecific competition and niche partitioning were observed between the two species indicating that species coexistence is favoured instead of competitive exclusion. L. major performed better in the ‘after dredging’ treatment. Consequently, we deduce that sediment dredging will not lead to a decline of the invasive L. major.     

X-ray Crystal Structure of the Rotavirus Inner Capsid Particle at 3.8 Å Resolution

The rotavirus inner capsid particle, known as the “double-layered particle” (DLP), is the “payload” delivered into a cell in the process of viral infection. Its inner and outer protein layers, composed of viral protein (VP) 2 and VP6, respectively, package the 11 segments of the double-stranded RNA (dsRNA) of the viral genome, as well as about the same number of polymerase molecules (VP1) and capping-enzyme molecules (VP3). We have determined the crystal structure of the bovine rotavirus DLP. There is one full particle (outer diameter ∼ 700 Å) in the asymmetric unit of the P2₁2₁2₁ unit cell of dimensions a = 740 Å, b = 1198 Å, and c = 1345 Å. A three-dimensional reconstruction from electron cryomicroscopy was used as a molecular replacement model for initial phase determination to about 18.5 Å resolution, and the 60-fold redundancy of icosahedral particle symmetry allowed phases to be extended stepwise to the limiting resolution of the data (3.8 Å). The structure of a VP6 trimer (determined previously by others) fits the outer layer density with very little adjustment. The T = 13 triangulation number of that layer implies that there are four and one-third VP6 trimers per icosahedral asymmetric unit. The inner layer has 120 copies of VP2 and thus 2 copies per icosahedral asymmetric unit, designated VP2A and VP2B. Residues 101-880 fold into a relatively thin principal domain, comma-like in outline, shaped such that only rather modest distortions (concentrated at two “subdomain” boundaries) allow VP2A and VP2B to form a uniform layer with essentially no gaps at the subunit boundaries, except for a modest pore along the 5-fold axis. The VP2 principal domain resembles those of the corresponding shells and homologous proteins in other dsRNA viruses: λ1 in orthoreoviruses and VP3 in orbiviruses. Residues 1-80 of VP2A and VP2B fold together with four other such pairs into a “5-fold hub” that projects into the DLP interior along the 5-fold axis; residues 81-100 link the 10 polypeptide chains emerging from a 5-fold hub to the N-termini of their corresponding principal domains, clustered into a decameric assembly unit. The 5-fold hub appears to have several distinct functions. One function is to recruit a copy of VP1 (or of a VP1-VP3 complex), potentially along with a segment of plus-strand RNA, as a decamer of VP2 assembles. The second function is to serve as a shaft around which can coil a segment of dsRNA. The third function is to guide nascent mRNA, synthesized in the DLP interior by VP1 and 5′-capped by the action of VP3, out through a 5-fold exit channel. We propose a model for rotavirus particle assembly, based on known requirements for virion formation, together with the structure of the DLP and that of VP1, determined earlier.     

Syntheses and structures of some adducts of silver(I) oxyanion salts with some 2-N,O-donor-substituted pyridine bases

Syntheses and room-temperature single crystal X-ray structural characterizations are recorded for a variety of silver(I) oxyanion (perchlorate, nitrate and trifluoroacetate (‘tfa’) (increasing basicity)) adducts, AgX, with a number of pyridine (‘py’) bases, L, functionalized in the 2-position with N- or O-donor groups, namely 2-amino-, 2-amino-6-methyl-, 2-aminomethyl-, 2-hydroxy-, 2-methoxy- and 2-acetyl- pyridines, ‘2np’, ‘nmp’, ‘amp’, ‘ohp’, ‘mop’, and ‘acp’. A variety of stoichiometries and associated structural types are defined: [Ag(chelate)₂]X, L/X = amp,acp/ClO₄, [XAg(chelate)₂], L/X = acp/tfa, of 1:2 AgX:L stoichiometry; for 1:1 stoichiometry, although a discrete mononuclear complex [(chelate)Ag(O₂NO)] is defined for AgNO₃: acp (1:1), all others are polymers, successive silver atoms being linked by N,N′-bridging ligands singly (L/X = 2np/ClO₄ (?HAgHTAgTHAgH?), amp/ClO₄, NO₃ (?HTAgHTAg?) (‘H’ ≡ head, ‘T’ = tail)) or pairwise, ?L₂AgX₂AgL₂Ag? (L/X = 2np/tfa, nmp/NO₃). More complex polymeric arrays are found with L/X = ohp/NO₃, tfa, where interaction with the metal takes place via the O-donor only, the py functionality being protonated, and in adducts of more complex stoichiometry AgNO₃:mop (2:3) and AgNO₃:2np (3:4).     

‘Single lay out’ and ‘mixed lay out’ enzymatic processes for bio-bleaching of kraft pulp

Xylanase alone as ‘single lay out’ (strategy I) and in combination with pectinase as ‘mixed lay out’ (strategy II) was used to investigate their bio-bleaching potentials. Strategy I was carried at 70 °C using 5 U/g of xylanase at pH 9.5 and 12.5 whereas strategy II was carried out at 70 °C using 5 U/g of each of the enzyme, respectively at pH 9.5. Bio-bleaching caused 15% and 20% less Cl₂ consumption though strategy I and II, respectively over chemical bleaching. Strategy II was proved to be 35.71% more efficient in ClO₂ saving than conventional method. Significant improvement in various pulp properties viz. tensile strength 25.70%, breaking length 21.80%, burst factor 20.00%, burstness 13.86%, tear factor 6.61% and tearness 18.88%, was also observed through ‘mixed lay out’ strategy.     

Fluorescein-labeled “arch-like” DNA probes for electrochemical detection of DNA on gold nanoparticle-modified gold electrodes

In the present study, a gold nanoparticle-modified gold electrode (nanogold electrode) was used to develop a novel fluorescein electrochemical DNA biosensor based on a target-induced conformational change. The nanogold electrode was obtained by electrodepositing gold nanoparticles onto a bare gold electrode. This modification not only immobilized probe oligonucleotides, but also adsorbed fluorescein onto the surface of the gold nanoparticles to form an “arch-like” structure. This article compares the electrochemical signal changes caused by the hybridization of “arch-like” DNA on nanogold electrode and linear DNA on bare gold electrode. The results showed that the adsorption effect of nanogold can enhance the sensitivity of the sensor. The linear range of target ssDNA is from 2.0 × 10⁻⁹ M to 2.0 × 10⁻⁸ M with a correlation coefficient of 0.9956 and detection limit (3σ) of 7.10 × 10⁻¹⁰ M. Additionally, the specificity and hybridization response of this simple sensor were investigated.     

Efficiency of estrous synchronization in tropical sheep by combining short-interval cloprostenol-based protocols and “male effect”

This study assessed the efficacy of a protocol combining short-interval cloprostenol-based protocols and “male effect” for estrous synchronization in hair sheep. In Experiment 1, 24 ewes were randomly assigned to three groups (n = 8) and treated with cloprostenol on Days 3, 5 and 7 after ovulation, respectively. Estradiol secretion during the follicular phase was similar among groups. Onset of estrus (P < 0.001) and the timing of maximum LH concentration (P < 0.01) were earlier in group D3 than in D5 and D7 groups. During the subsequent cycle, the number and size of corpora lutea were higher (P < 0.05) in ewes of the groups D3 (1.9 ± 0.3 and 115.1 ± 14.3 mm²) and D5 (1.8 ± 0.2 and 100.2 ± 11.2 mm²) than in group D7 (1.3 ± 0.2 and 75.6 ± 6.4 mm²) group. In Experiment 2, 24 ewes were treated with two cloprostenol injections (7 days apart). Twelve ewes were exposed to “male effect” previous to an isolation period (ME group), whereas the remaining ewes were controls without male exposure (CTR group). Male effect induced earlier preovulatory LH surge (P < 0.05) and ovulation (P < 0.001) than CTR group. In Experiment 3, the estrus was synchronized in 68 ewes. Nineteen of them (group FGA) were treated using intravaginal sponges impregnated with fluorogestone acetate for 12 days and inseminated at 55 h. Forty-nine females (group ME) were treated like ME group. Twenty-four (ME48 group) and 25 ewes (ME55 group) were inseminated at 48 and 55 h after treatment, respectively. The fertility rate was numerically higher in ME48 than ME55 and FGA groups (62.5, 44.0 and 47.4%, respectively). In conclusions, the combined use of short-interval cloprostenol treatment and “male effect” may be an adequate alternative for synchronizing estrus and applying artificial insemination in hair sheep throughout the entire year.