Phase studies of model biomembranes: Macroscopic coexistence of Lα + Lβ, with light-induced coexistence of Lα + Lo Phases

Phase diagrams of 3-component lipid bilayer mixtures containing cholesterol reveal major differences among the different types of lipids. Here we report that mixtures of cholesterol together with POPC and a high-melting temperature PC or sphingomyelin show different phase behavior from similar mixtures that contain DOPC or di-phytanoyl-PC instead of POPC. In particular, only one region of macroscopic phase coexistence occurs with POPC, a region of coexisting liquid disordered and solid phases, {Lα + Lβ}. Fluorescence microscopy imaging is useful for these studies, but is subject to artifactual light-induced domain formation, as reported by Ayuyan and Cohen [A.G. Ayuyan, F.S. Cohen, Lipid peroxides promote large rafts: Effects of excitation of probes in fluorescence microscopy and electrochemical reactions during vesicle formation, Biophys. J. 91 (2006) 2172-2183.]. This artifact can be attenuated by decreased illumination and low dye concentration. The use of the free radical scavenger n-propyl gallate can reduce the artifact, but this molecule enters the bilayer and itself perturbs the phase behavior. We suggest that the light-induced domain separation artifact might actually arise from pre-existing lipid clusters that are induced to coalesce, and therefore indicates highly nonrandom mixing of the lipid components.     

Cyclooxygenase-2 169C > G and 8473T > C gene polymorphisms and prostaglandin E2 level in breast cancer: A case–control study

Aims

Cyclooxygenase 2 (COX-2) with the resulting prostaglandin E2 (PGE2) is linked to increased risk of human breast cancer (BC). The aim of this study was to determine COX-2 169C > G and 8473T > C gene polymorphisms and PGE2 level at various stages of BC clarifying the role of COX-2 gene polymorphism and PGE2 in relation to BC.

Methods

The study population comprised 160 women at different stages of BC and 150 gender- and age-matched healthy control subjects. Plasma PGE2 was measured by ELISA, the COX-2 gene polymorphisms were determined using PCR-RFLP.

Results

The variant alleles COX-2 169G and 8473C were significantly associated with BC susceptibility [OR = 3.1, 95% CI (2.2–4.4), P < 0.001 for 169C>G and OR = 1.74, 95%CI (1.3–2.4), P = 0.005 for 8473C]. However, both COX-2 gene polymorphisms were not associated with breast cancer stage. Plasma PGE2 levels were significantly increased in patients compared to the controls. In early and late stages of BC, there was a significant increase in the plasma PGE2 levels towards the presence of homozygous GG compared with homozygous CC (P < 0.001) for 169 C>G, also towards the presence of CC than TT (P < 0.001) for 8473T>C SNP.

Conclusion

The 169C>G and 8473T>C polymorphisms of the COX-2 gene were associated with the BC in Egyptian women. Furthermore, individuals with COX-2 169GG and 8473CC genotypes showed significant increase in plasma PGE2 levels. PGE2 levels may serve as a predictor of poor prognosis in patients with BC.     

Synthesis, crystal structures, and spectroscopic characterization of the neutral monomeric tetrahedral [M(Diap)2(OAc)2] · H2O complexes (M = Zn,Cd; Diap = 1,3-diazepane-2-thione; OAc = acetate) with N-H?O and O-H?O intra- and intermolecular hydrogen bonding interactions

The title complexes, [M(Diap)₂(OAc)₂] · H₂O (M = Zn,Cd; Diap = 1,3-diazepane-2-thione; OAc = acetate) with an MO₂S₂ configuration, have been characterized by X-ray crystallography as well as FT-IR, ¹H and ¹³C NMR spectroscopy. In these complexes, the metal atoms lie in a pseudo-tetrahedral environment and are coordinated by the thione sulfur atoms of two neutral 1,3-diazepane-2-thione ligands and one oxygen atom from each of two monodentate acetate anions. In both complexes, there are two intramolecular N-H?O hydrogen bonds, each being between one NH group of a Diap ligand and the uncoordinated O atom of an OAc ligand. The water molecule is also involved in hydrogen bonds, as an acceptor and as a donor twice, linking together three symmetry-related complexes. The Cd complex undergoes a structural phase transition from a monoclinic form at 150 K with Z′ = 2 to a smaller monoclinic cell at room temperature with Z′ = 1 without loss of crystallinity. The Zn complex does not exhibit an equivalent phase transition, and at 150 K is isostructural with the room-temperature form of the Cd complex. All three crystallographically independent molecules found for the Cd complex (two at low temperature and one at room temperature) have essentially the same structure except for small changes in the conformations of the ligands. Tetrahedral coordination with monodentate carboxylate ligands is common for Zn complexes of this kind, but is unusual for Cd complexes, and is the result of the bulky Diap ligands.     

Interleukin-1α − 899 (+ 4845) C→T polymorphism increases the risk of chronic periodontitis: Evidence from a meta-analysis of 23 case–control studies

Many epidemiological studies have indicated that interleukin-1α (IL-1α) − 899 (+ 4845) C→T polymorphism increases the risk of chronic periodontitis (CP), whereas some studies have reported opposite results. Accordingly, the aim of this meta-analysis is to investigate the association of the IL-1α − 899 (+ 4845) C→T polymorphism with CP. We searched the PubMed database up to May 1, 2013 and finally obtained 23 case–control studies. After data extraction, we performed meta-analysis using Comprehensive Meta-Analysis v2.2 software. The overall result based on the fixed-effect model showed that IL-1α − 899 (+ 4845) C→T polymorphism was significantly associated with increased risk of CP: [odds ratio (OR) = 1.29, 95% confidence interval (CI) = 1.15–1.44, p < 0.001] for T vs. C; (OR = 1.59, 95%CI = 1.22–2.07, p = 0.0005) for TT vs. CC; (OR = 1.30, 95% CI = 1.12–1.51, p = 0.0004) for CT vs. CC; and (OR = 1.40, 95% CI = 1.21–1.61, p < 0.001) for (CT+TT) vs. CC; (OR = 1.47, 95% CI = 1.16–1.87, p = 0.002) for TT vs. (CT+CC). Stratified analyses revealed that there was a significantly increased risk for Caucasians and Asians. In conclusion, current evidence showed that IL-1α − 899 (+ 4845) C→T polymorphism probably increased the risk of CP.     

How do leaf trait values change spatially and temporally with light availability in a grassland diversity experiment?

Complementarity in light use might increase light exploitation and could be an important mechanism explaining the coexistence of multiple species in plant communities of increasing diversity. We measured vertical light profiles and leaf traits related to light acquisition and light use in 40 mixtures of varying species richness (SR, 2, 4, 8 and 16) and functional group richness (FR, 1‐4) in a large grassland biodiversity experiment at five different times during the growing season. Light attenuation within the canopy differed significantly among mixtures of varying SR at peak biomass, with 40% in 2‐species mixtures and up to 80% in 16‐species mixtures. In contrast, increasing SR did not affect light attenuation at the beginning of the growing season or during regrowth after mowing, when large fractions of incoming radiation reached the ground level. These patterns suggested the presence of highly variable light niches over space and time. Trait expression differed among functional groups (except specific leaf area (SLA)) and varied within the growing season. However, we found no direct effect of increased SR or FR on the expression of leaf traits, except for positive species richness‐effects on SLA at peak biomass time. SLA and stomatal conductance increased and leaf dry matter content decreased at lower light at leaf height, while leaf greenness was independent of relative light availability. Dissimilarity of leaf traits (except SLA) at the community level increased with increasing SR. Thus, our results suggest that after accounting for light availability, which was driven by SR and time of year, variations in leaf trait expression within the grassland canopies did not depend on SR, but rather on functional group identity and time of year. Consequently, increased complementarity in light use at higher plant diversity is due to presence of more species with different leaf trait expression and trait variation in response to the actual light environment.     

A family of lanthanide-containing molecular open frameworks with high porosity: [Ln(abdc)(Habdc), nH2O]∞ with Ln = La-Eu and 8 ? n ? 11

Reactions in water between the di-sodium salt of amino terepthalic acid (C₈H₃NO₄Na₂) and a lanthanide chloride lead to a family of 3D-coordination polymers with general chemical formula [Ln(C₈H₃NO₄)(C₈H₄NO₄), O]_∞ where Ln = La-Eu (except Pm) and 8 ? n ? 11. All these compounds are isostructural. High quality single crystals of [Ln(C₈H₃NO₄)(C₈H₄NO₄), nH₂O]_∞ with Ln = La-Sm (except Pm) and 8 ? n ? 11 have been obtained by slow diffusion in agar-agar gels. The crystal structure has been solved for the Nd-containing compound. This compound crystallizes in the cubic system, space group Ia-3 (no. 206) with a = 26.8056(5) Å. The crystal structure can be described as the juxtaposition of large channels with square cross-section.The channels are filled by highly disordered crystallization water molecules. The dehydration of the compounds by freeze-drying is possible and most of the crystallization water molecules can be removed without destruction of the molecular skeleton. The partially dehydrated compounds have general chemical formula [Ln(abdc)(Habdc), 2H₂O]_∞ with Ln = La-Eu except Pm. The porosity of the Nd-containing compound has been estimated by computational methods to 2170 m² g⁻¹. This dehydrated compound reversibly binds water when exposed to wet atmosphere restoring the initial hydrated phase.     

PPARβ mRNA expression,reduced by n − 3 PUFA diet in mammary tumor,controls breast cancer cell growth

The effect of numerous anticancer drugs on breast cancer cell lines and rodent mammary tumors can be enhanced by a treatment with long-chain n − 3 polyunsaturated fatty acids (n − 3 PUFA) such as docosahexaenoic acid (DHA, 22:6n − 3) which is a natural ligand of peroxisome proliferator-activated receptors (PPAR). In order to identify the PPAR regulating breast cancer cell growth, we tested the impact of siRNA, selected to suppress PPARα, PPARβ or PPARγ mRNA in MDA-MB-231 and MCF-7 breast cancer cell lines. The siPPARβ was the most effective to inhibit breast cancer cell growth in both cell lines. Using PPARα, PPARβ and PPARγ pharmacological antagonists, we showed that PPARβ regulated DHA-induced inhibition of growth in MDA-MB-231 and MCF-7 cells. In addition, the expressions of all 3 PPAR mRNA were co-regulated in both cell lines, upon treatments with siRNA or PPAR antagonists. PPAR mRNA expression was also examined in the NitrosoMethylUrea (NMU)-induced rat mammary tumor model. The expressions of PPARα and PPARβ mRNAs were correlated in the control group but not in the n − 3 PUFA group in which the expression of PPARβ mRNA was reduced. Although PPARα expression was also increased in the n − 3 PUFA-enriched diet group under docetaxel treatment, it is only the expression of PPARβ mRNA that correlated with the regression of mammary tumors: those that most regressed displayed the lowest PPARβ mRNA expression. Altogether, these data identify PPARβ as an important player capable of modulating other PPAR mRNA expressions, under DHA diet, for inhibiting breast cancer cell growth and mammary tumor growth.     

Mixed-valent and radical states of complexes [(bpy)2M(μ-abpy)M′(bpy)2], M,M′ = Ru or Os, abpy = 2,2′-azobispyridine: Electron transfer vs. hole transfer mechanism in azo ligand-bridged complexes

The title complexes were obtained as M^IIM′^II species [(bpy)₂M(μ-abpy)M′(bpy)₂](PF₆)₄, M,M′ = Ru or Os, using the new mononuclear precursor [(bpy)₂Os(abpy)](PF₆)₂ for the osmium-containing dinuclear complexes. One-electron reduction produces radical complexes [(bpy)₂M(μ-abpy)M′(bpy)₂]³⁺ and [(bpy)₂M(abpy)]⁺ with significant contributions from the metals, as evident from the EPR effects on successive replacement of ruthenium by osmium with its much higher spin-orbit coupling constant. The diruthenium and diosmium radical complexes were also studied by EPR at high-frequency (285 GHz), the latter shows an unusually large g anisotropy g₁ − g₃ = 0.25 in frozen solution. Further reduction was monitored by UV/Vis spectroelectrochemistry. Oxidation produced Os^III EPR signals for [(bpy)₂Os(abpy)]³⁺ and [(bpy)₂Os(μ-abpy)Ru(bpy)₂]⁵⁺, indicating a Ru^IIOs^III species for the latter. The diosmium(III,II) and diruthenium(III,II) mixed-valent species remained EPR silent at 4 K, however, they exhibit weak inter-valence charge transfer (IVCT) bands at about 1460 nm. Whereas the cyclic voltammetric response towards reduction is only marginally different for the three dinuclear complexes, successive replacement of ruthenium by osmium causes the first oxidation potential to decrease. The much higher comproportionation constant K_c for the mixed valent diosmium(III,II) state (K_c > 10¹⁵) in comparison to the diruthenium(III,II) analogue with K_c = 10¹⁰ confirms the electron transfer alternative for the valence exchange mechanism, in contrast to the hole transfer established for analogous dinuclear complexes with the formally related diacylhydrazido(2−) bridging ligands.     

DNA aptamers bind specifically and selectively to (1 → 3)-β-d-glucans

(1 → 3)-β-d-Glucans are structural cell wall components of fungi, plants, and some bacteria and have been linked with human respiratory symptoms following aerosol exposure. A clear interpretation of the health impact of (1 → 3)-β-d-glucans is limited by the high cost and uncertainties associated with current glucan quantitation methods. The objective of this research is to develop DNA aptamers for the measurement of (1 → 3)-β-d-glucans. Aptamers are synthetic DNA functional binding molecules that fold into unique conformations, allowing them to bind specifically to their target. Through the in vitro selection process SELEX, we have produced aptamers that are able to bind with sub-micromolar affinity to curdlan, a linear unbranched form of (1 → 3)-β-d-glucans. These aptamers display high selectivity to curdlan and do not bind to non-(1 → 3)-β-d-polysaccharides, suggesting specificity for the β-(1 → 3)-glycosidic linkage. The aptamers produced here will enable the production of more cost-effective, less ambiguous assays for the environmental measurement of (1 → 3)-β-d-glucans.     

Salmo macrostigma (Teleostei,Salmonidae): Nothing more than a brown trout (S. trutta) lineage?

We examined specimens of the macrostigma trout Salmo macrostigma, which refers to big black spots on the flanks, to assess whether it is an example of taxonomic inflation within the brown trout Salmo trutta complex. Using new specimens, publicly available data and a mitogenomic protocol to amplify the control and cytochrome b regions of the mitochondrial genome from degraded museum samples, including one syntype specimen, the present study shows that the macrostigma trout is not a valid species. Our results suggest the occurrence of a distinct evolutionary lineage of S. trutta in North Africa and Sicily. The name of the North African lineage is proposed for this lineage, which was found to be sister to the Atlantic lineage of brown trout, S. trutta.     

Functional properties of the newly observed γ-chain fetal hemoglobin variant Hb F-Monserrato-Sassari (HBG2:c.280T > C) or [γ93 (F9) Cys → Arg]

Background

HbF-Monserrato-Sassari is a newly discovered abnormal fetal hemoglobin observed in an apparently normal newborn baby during a hemoglobinopathies survey at birth in North Sardinian population.

Methods

Electrophoretic analysis of the cord blood lysate evidenced for an abnormal tetramer due to a mutated fetal globin chain. Electrospray ionisation-mass spectrometry and gene sequencing were used to identify the mutation. Oxygen binding ability of the variant Hb was determined.

Results

Sequencing of the γ globin genes revealed the TGT → CGT transition at codon 93 in one of the two ^Gγ genes, which leads to the Arg for Cys amino acid replacement at position 9 of the F α-helix. The amino acid substitution was confirmed by mass spectrometric analysis of the globin chains. Since modifications or substitutions at position β93 are known to affect the arrangement of a salt bridge at the α1β2 sliding contacts that are crucial for subunit cooperativity, the functional properties of the variant were studied to evaluate the effect of the replacement at the same position in the γ globin chain. With respect to normal HbF, the variant showed a significant increase in oxygen affinity and a slight decrease of both Bohr effect and cooperativity.

General significance

Result indicates a key role of the Cys γ93 residue for subunit cooperativity in the T → R transition of the HbF tetramer. Substitutions at the F9 position of the ^Gγ globin may result in stabilization of the high affinity R-state of the Hb tetramer. Because of the loss of Cys γ93 residue, this variant is considered to be potentially compromised in nitric oxide transport.     

Spin crossover behavior of a one-dimensional polymeric-chain compound {[Fe(abpt)2(μ-Ni(CN)4)]·xH2O}n (x = 0.5 → 0): Synthesis, spectral, thermal and magnetic properties

A one-dimensional polymeric-chain iron(II)-nickel(II) cyanido-bridged complex of the composition {[Fe(abpt)₂(μ-Ni(CN)₄)]·0.5H₂O}_n (1·0.5H₂O), where abpt = 4-amino-3,5-di-2-pyridyl-4H-1,2,4-triazole, was prepared and characterized by elemental and thermal analyses, FTIR and ⁵⁷Fe Mössbauer spectroscopies, and magnetic measurements. The incomplete spin crossover phenomenon was observed with approximately 12% of the frozen high-spin fraction at low temperatures and with the spin transition critical temperature above room temperature.     

Metal(II)-organic coordination polymers with two distinct atropisomeric building units from an axially prochiral inner salt through interchain C-H?X hydrogen bonds (X = O, Cl; metal = cobalt, nickel)

Two isostructural photoluminescent metal-organic coordination polymers, namely, [M(H-mpypdc)(Cl)(H₂O)₃]_n (mpypdc = 2,6-dimethyl-4-(pyridin-4-yl)pyridine-3,5-dicarboxylate; M = Co (2) and Ni (3)), were synthesized from H₂mpypdc (1), and characterized by single crystal X-ray analyses. New ligand 1 is an inner salt. In the metal-organic coordination polymeric chains, two distinct S- and R-atropisomeric units are generated from the axially prochiral 1 through C-H?X (X = O, Cl) hydrogen bonds. There have interesting 2D supramolecular networks [M(Cl)(H₂O)₂]_n in the crystal structures of title compounds. The photoluminescence of new compounds are also investigated in solid state at ambient temperature.     

Preparation of (1 → 3)-β-d-glucan oligosaccharides by hydrolysis of curdlan with commercial α-amylase

Water soluble (1 → 3)-β-d-glucan oligosaccharides were prepared by hydrolyzing curdlan with α-amylase. The hydrolysis process was monitored by the DE values of the hydrolysates. Under the optimized conditions (pH, 5.98; temperature, 55.92 °C; α-amylase amount, 31.94 mg α-amylase/500 mL of reaction mixture containing 5 g curdlan; reaction time, 30 min), maximum DE value (15.62%) was obtained. The resulting products were composed of (1 → 3)-β-d-glucan oligosaccharides of DP 2-9. The hydrolysates were filtered, concentrated to ∼20% (w/v), and precipitated with 5 volumes of ethanol, which were then freeze dried to yield a water soluble powder. The (1 → 3)-β-d-glucan oligosaccharides content of the product and the yield were 97.7% and 97.6% (w/w), respectively.     

Key aromatic residues at subsites + 2 and + 3 of glycoside hydrolase family 31 α-glucosidase contribute to recognition of long-chain substrates

Glycoside hydrolase family 31 α-glucosidases (31AGs) show various specificities for maltooligosaccharides according to chain length. Aspergillus niger α-glucosidase (ANG) is specific for short-chain substrates with the highest k_cat/K_m for maltotriose, while sugar beet α-glucosidase (SBG) prefers long-chain substrates and soluble starch. Multiple sequence alignment of 31AGs indicated a high degree of diversity at the long loop (N-loop), which forms one wall of the active pocket. Mutations of Phe236 in the N-loop of SBG (F236A/S) decreased k_cat/K_m values for substrates longer than maltose. Providing a phenylalanine residue at a similar position in ANG (T228F) altered the k_cat/K_m values for maltooligosaccharides compared with wild-type ANG, i.e., the mutant enzyme showed the highest k_cat/K_m value for maltotetraose. Subsite affinity analysis indicated that modification of subsite affinities at + 2 and + 3 caused alterations of substrate specificity in the mutant enzymes. These results indicated that the aromatic residue in the N-loop contributes to determining the chain-length specificity of 31AGs.     

Do ‘we’ ‘do’ God? Linda Woodhead & Rebecca Catto (eds), Religion and change in modern Britain. London: Routledge.

What does it mean to talk of the religion ‘of’ a given country? I reflect on an edited volume dealing with religion in Britain and consider two related themes: the secular considered as ‘absence’ or ‘presence’, and the siting of religion not in conventional denominations or ritual practices but in spaces of encounter between religions, and between the so‐called ‘religious’ and ‘secular’.     

Recombination initiation: Easy as A, B, C, D… χ?

The octameric Chi (χ) sequence is a recombination hotspot in Escherichia coli. Recent studies suggest a singular mechanism by which χ regulates not only the nuclease activity of RecBCD enzyme, but also the ability of RecBCD to promote loading of the strand exchange protein, RecA, onto χ-containing DNA.