Seasonal impact of waterfowl on communities of macrophytes in a shallow lake

From 2005 to 2007, we established bird-proof enclosures in a small, shallow and semi-permanent lake, lacking fish, at Brown Moss, Shropshire, UK, to investigate the effects of aquatic birds on seasonal growth of submerged and emergent macrophytes. The highest density of birds on the lake was in winter (110 individuals ha⁻¹) and the lowest in summer 2005 (6 ha⁻¹). Plant growth varied with season but there were significantly different (F = 8.03, p < 0.05, df = 1) standing crops of macrophytes between bird-proof enclosures (proportion of volume occupied, 0.47 ± 0.04) and control treatments (0.36 ± 0.11). Different densities of birds occurred in different areas and this was reflected in their effects. Ducks, mainly mallard (Anas platyrhynchos, Linnaeus), and teal (Anas crecca, Linnaeus), damaged plants by direct consumption, uprooting and trampling, whereas larger birds, such as mute swan (Cygnus olor, Gmelin), were able to remove Typha latifolia (Linnaeus). In summer, grazing pressure was reduced as the population of birds declined. Waterfowl caused seasonal impacts on the re-development of the water plant community. However, waterfowl herbivory had low potential to shift a macrophyte-dominated state into a phytoplankton-dominated state because aquatic plants could recover, during the growing season, when bird populations declined.     

Ecology of aquatic Ranunculus communities under the Mediterranean climate

The Iberian Peninsula encompasses more than 80% of the species richness of European aquatic ranunculi. The floristic diversity of the phytocoenosis characterised by aquatic Ranunculus and the main physical–chemical factors of the water were studied in 43 localities of the central Iberian Peninsula. Four aquatic Ranunculus communities are found in most of the aquatic environments. These are species-poor and have an uneven distribution: three species of Batrachium are heterophyllous and their communities are distributed in different aquatic ecosystems on silicated substrates; one species is homophyllous and its community occurs in various aquatic ecosystems with carbonated waters. In the Mediterranean climate, Ranunculus species are present in different habitats, as shown by the results of all the statistical analyses. Ranunculus trichophyllus communities occur in base-rich waters with a high buffering capacity (2273.44 ± 794.57 mg CaCO₃ L⁻¹) and a high concentration of cations (Ca²⁺, 121 ± 33.12 mg L⁻¹; Mg²⁺, 71.64 ± 82.77 mg L⁻¹), nitrates (2.89 ± 4.80 mg L⁻¹), ammonium (2.19 ± 1.36 mg L⁻¹) and sulphates (216.25 ± 218.54 mg L⁻¹). Ranunculus penicillatus communities are found in flowing waters with a high concentration of phosphates (0.48 ± 0.6 mg L⁻¹) and intermediate buffering capacity (683.66 ± 446.76 mg CaCO₃ L⁻¹). Both Ranunculus pseudofluitans and Ranunculus peltatus communities grow in waters with low buffering capacity (R. pseudofluitans, 385.91 ± 209.2 mg CaCO₃ L⁻¹; R. peltatus, 263.3 ± 180.36 mg CaCO₃ L⁻¹), and a low concentration of cations (R. pseudofluitans: Ca²⁺, 12.57 ± 9.42 mg L⁻¹; Mg²⁺, 3.42 ± 1.67 mg L⁻¹; R. peltatus: Ca²⁺, 15 ± 18.26 mg L⁻¹; Mg²⁺, 6.26 ± 8.89 mg L⁻¹) and nutrients (R. pseudofluitans: nitrates, 0.23 ± 0.2 mg L⁻¹; phosphates, 0.09 ± 0.1 mg L⁻¹; R. peltatus: nitrates, 0.19 ± 0.21 mg L⁻¹; phosphates, 0.09 ± 0.12 mg L⁻¹); the first in flowing waters, the latter in still waters.     

Dehydration mediated microRNA response in the African clawed frog Xenopus laevis

Exposure to various environmental stresses induces metabolic rate depression in many animal species, an adaptation that conserves energy until the environment is again conducive to normal life. The African clawed frog, Xenopus laevis, is periodically subjected to arid summers in South Africa, and utilizes entry into the hypometabolic state of estivation as a mechanism of long term survival. During estivation, frogs must typically deal with substantial dehydration as their ponds dry out and X. laevis can endure > 30% loss of its body water. We hypothesize that microRNAs play a vital role in establishing a reversible hypometabolic state and responding to dehydration stress that is associated with amphibian estivation. The present study analyzes the effects of whole body dehydration on microRNA expression in three tissues of X. laevis. Compared to controls, levels of miR-1, miR-125b, and miR-16-1 decreased to 37 ± 6, 64 ± 8, and 80 ± 4% of control levels during dehydration in liver. By contrast, miR-210, miR-34a and miR-21 were significantly elevated by 3.05 ± 0.45, 2.11 ± 0.08, and 1.36 ± 0.05-fold, respectively, in the liver. In kidney tissue, miR-29b, miR-21, and miR-203 were elevated by 1.40 ± 0.09, 1.31 ± 0.05, and 2.17 ± 0.31-fold, respectively, in response to dehydration whereas miR-203 and miR-34a were elevated in ventral skin by 1.35 ± 0.05 and 1.74 ± 0.12-fold, respectively. Bioinformatic analysis of the differentially expressed microRNAs suggests that these are mainly involved in two processes: (1) expression of solute carrier proteins, and (2) regulation of mitogen-activated protein kinase signaling. This study is the first report that shows a tissue specific mode of microRNA expression during amphibian dehydration, providing evidence for microRNAs as crucial regulators of metabolic depression.     

An unusual thermostable aspartic protease from the latex of Ficus racemosa (L.)

The most extensively studied ficins have been isolated from the latex of Ficus glabrata and Ficus carica. However the proteases (ficins) from other species are less known. The purification and characterization of a protease from the latex of Ficus racemosa is reported. The enzyme purified to homogeneity is a single polypeptide chain of molecular weight of 44,500 ± 500 Da as determined by MALDI-TOF. The enzyme exhibited a broad spectrum of pH optima between pH 4.5-6.5 and showed maximum activity at 60 ± 0.5 °C. The enzyme activity was completely inhibited by pepstatin-A indicating that the purified enzyme is an aspartic protease. Far-UV circular dichroic spectra revealed that the purified enzyme contains predominantly β-structures. The purified protease is thermostable. The apparent T_m, (mid point of thermal inactivation) was found to be 70 ± 0.5 °C. Thermal inactivation was found to follow first order kinetics at pH 5.5. Activation energy (E_a) was found to be 44.0 ± 0.3 kcal mol⁻¹. The activation enthalpy (ΔH^∗), free energy change (ΔG^∗) and entropy (ΔS^∗) were estimated to be 43 ± 4 kcal mol⁻¹, −26 ± 3 kcal mol⁻¹ and 204 ± 10 cal mol⁻¹ K⁻¹, respectively. Its enzymatic specificity studied using oxidized B chain of insulin indicates that the protease preferably hydrolyzed peptide bonds C-terminal to glutamate, leucine and phenylalanine (at P₁ position). The broad specificity, pH optima and elevated thermal stability indicate the protease is distinct from other known ficins and would find applications in many sectors for its unique properties.     

Disparity between Multilocus Enzyme Electrophoresis, Microsatellite Markers and Pulsed-Field Gel Electrophoresis in epidemiological tracking of Candida albicans

Various molecular systems are available for epidemiological, genetic, evolutionary, taxonomic and systematic studies of innumerable fungal infections, especially those caused by the opportunistic pathogen C. albicans. A total of 75 independent oral isolates were selected in order to compare Multilocus Enzyme Electrophoresis (MLEE), Electrophoretic Karyotyping (EK) and Microsatellite Markers (Simple Sequence Repeats - SSRs), in their abilities to differentiate and group C. albicans isolates (discriminatory power), and also, to evaluate the concordance and similarity of the groups of strains determined by cluster analysis for each fingerprinting method. Isoenzyme typing was performed using eleven enzyme systems: Adh, Sdh, M1p, Mdh, Idh, Gdh, G6pdh, Asd, Cat, Po, and Lap (data previously published). The EK method consisted of chromosomal DNA separation by pulsed-field gel electrophoresis using a CHEF system. The microsatellite markers were investigated by PCR using three polymorphic loci: EF3, CDC3, and HIS3. Dendrograms were generated by the SAHN method and UPGMA algorithm based on similarity matrices (S_SM). The discriminatory power of the three methods was over 95%, however a paired analysis among them showed a parity of 19.7-22.4% in the identification of strains. Weak correlation was also observed among the genetic similarity matrices (S_SM^MLEE × S_SM^EK × S_SM^SSRs). Clustering analyses showed a mean of 9 ± 12.4 isolates per cluster (3.8 ± 8 isolates/taxon) for MLEE, 6.2 ± 4.9 isolates per cluster (4 ± 4.5 isolates/taxon) for SSRs, and 4.1 ± 2.3 isolates per cluster (2.6 ± 2.3 isolates/taxon) for EK. A total of 45 (13%), 39 (11.2%), 5 (1.4%) and 3 (0.9%) clusters pairs from 347 showed similarity (S_J) of 0.1-10%, 10.1-20%, 20.1-30% and 30.1-40%, respectively. Clinical and molecular epidemiological correlation involving the opportunistic pathogen C. albicans may be attributed dependently of each method of genotyping (i.e., MLEE, EK, and SSRs) supplemented with similarity and grouping analysis. Therefore, the use of genotyping systems that give results which offer minimum disparity, or the combination of the results of these systems, can provide greater security and consistency in the determination of strains and their genetic relationships.     

Bicarbonate use in three aquatic plants

Our study aimed to test the ability of aquatic plants to use bicarbonate when acclimated to three different bicarbonate concentrations. To this end, we performed experiments with the three species Ceratophyllum demersum, Egeria densa, Lagarosiphon major to determine photosynthetic rates under varying bicarbonate concentrations. We measured bicarbonate use efficiency, photosynthetic performance and respiration. For all species, our results revealed that photosynthetic rates were highest in replicates grown at low alkalinity. Thus, E. densa had approx. five times higher rates at low (264 ± 15 μmol O₂ g⁻¹ DW h⁻¹) than at high alkalinity (50 ± 27 μmol O₂ g⁻¹ DW h⁻¹), C. demersum had three times higher rates (336 ± 95 and 120 ± 31 μmol O₂ g⁻¹ DW h⁻¹), and L. major doubled its rates at low alkalinity (634 ± 114 and 322 ± 119 μmol O₂ g⁻¹ DW h⁻¹). Similar results were obtained for bicarbonate use efficiency by E. densa (136 ± 44 and 43 ± 10 μmol O₂ mequiv. L⁻¹ g⁻¹ DW h⁻¹) and L. major (244 ± 29 and 82 ± 24 μmol O₂ mequiv. L⁻¹ g⁻¹ DW h⁻¹). As to C. demersum, efficiency was high but unaffected by alkalinity, indicating high adaptation ability to varied alkalinities. A pH drift experiment supported these results. Overall, our results suggest that the three globally widespread worldwide species of our study adapt to low inorganic carbon availability by increasing their efficiency of bicarbonate use.     

Diastereomeric preference in 1,4,7-tris((S)-2-hydroxy-3-phenylpropyl)-1,4,7-triazacyclononanelithium(I) and its sodium(I) analogue

In N,N-dimethylformamide (DMF), 1,4,7-tris((S)-2-hydroxy-3-phenylpropyl)-1,4,7-triazacyclononane forms metal complexes, [M(S-thppc9)]⁺, for which log K (dm³ mol⁻¹)=3.01, 2.65, 2.66, 2.65, 2.42 and 7.59 (all±0.05) where M⁺=Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and Ag⁺, respectively. Variable temperature ¹³C{¹H} NMR spectroscopy shows that the interchange between equivalent forms of a single diastereomer occurs for [Li(S-thppc9)]⁺ and [Na(S-thppc9)]⁺ characterised by: k=43±5 and 2900±100 s⁻¹, at 298.2 K, ΔH^‡=22.5±1.6 and 33.8±1.6 kJ mol⁻¹, and ΔS^‡=−133±5 and −59±6 J K⁻¹ mol⁻¹, respectively. Gas phase ab initio modelling shows these complexes and their K⁺ analogue to preferentially form distorted trigonal prismatic Λ, Δ, and Λ diastereomers, respectively.     

Inter-simple sequence repeat (ISSR) analysis of genetic variation of Chondrus crispus populations from North Atlantic

ISSR analysis was used to investigate genetic variations of 184 haploid and diploid samples from nine North Atlantic Chondrus crispus Stackhouse populations and one outgroup Yellow Sea Chondrus ocellatus Holmes population. Twenty-two of 50 primers were selected and 163 loci were scored for genetic diversity analysis. Genetic diversity varied among populations, percentage of polymorphic bands (PPB) ranged from 27.0 to 55.8%, H (Nei's genetic diversity) ranged from 0.11 to 0.20 and I (Shannon's information index) ranged from 0.16 to 0.30. Estimators PPB, H and I had similar values in intra-population genetic diversity, regardless of calculation methods. Analysis of molecular variance (AMOVA) apportioned inter-population and intra-population variations for C. crispus, showing more genetic variance (56.5%) occurred in intra-population, and 43.5% variation among nine populations. The Mantel test suggested that genetic differentiation between nine C. crispus populations was closely related with geographic distances (R = 0.78, P = 0.002). Results suggest that, on larger distance scale (ca. >1000 km), ISSR analysis is useful for determining genetic differentiations of C. crispus populations including morphologically inseparable haploid and diploid individuals.     

Development of high performance liquid chromatography/electrospray ionization mass spectrometry for assay of ginkgolic acid (15:1) in rat plasma and its application to pharmacokinetics study

A highly sensitive HPLC–ESI-MS method has been developed and validated for the quantification of ginkgolic acid (15:1) in a small quantity of rat plasma (50 μL) using its homologous compound ginkgolic acid (17:1) as an internal standard. GA (15:1) and GA (17:1) were extracted from biological matrix by direct protein precipitation with 5-fold volume of methanol and separated on an Elite hypersil BDS C₁₈ column (2.1 × 100 mm, 3 μm), eluted with acetonitrile:water (92:8, v/v, containing 0.3% glacial acetic acid). Linear range was 8–1000 ng/mL with the square regression coefficient (r²) of 0.996. The lowest concentration (8 ng/mL) in the calibration curve was estimated as LLOQ with both deviation of accuracy and RSD of precision <20% (n = 6). The intra- and inter-day precision ranged from 3.6% to 9.9%, and the intra- and inter-day accuracy was between 89.9% and 101.3%. This method was successfully applied to study pharmacokinetics of GA (15:1) in rats after oral administration at a dose of 10 mg/kg. GA (15:1) pharmacokinetic parameters C_max, T_max, t_1/2, AUC_0–12h are 1552.9 ± 241.0 ng/mL, 0.9 ± 0.7 h, 5.5 ± 2.6 h, 3356.0 ± 795.3 ng h/mL, respectively.     

Synthesis and isomerisation of two metallated N,O-complexes of ruthenium: Models for the Murai reaction

Two isomers of the N,O-coordinated acetylpyrrolyl complex [Ru(PPh₃)₂(CO)(NC₄H₃C(O)CH₃)H] {cis-N,H (1) and trans-N,H (2)} have been prepared as models for catalytic intermediates in the Murai reaction. Complex 2 isomerises to 1 upon heating via a dissociative pathway (ΔH^‡ = 195 ± 41 kJ mol⁻¹; ΔS^‡ = 232 ± 62 J mol⁻¹ K⁻¹); the mechanism of this process has been modeled using density functional calculations. Complex 2 displays moderate catalytic activity for the Murai coupling of 2′-methylacetophenone with trimethylvinylsilane, but 1 proved to be catalytically inactive under the same conditions.     

Structures of homoleptic eight- and nine-coordinate uranium(IV) perchlorate complexes with sulfoxide molecules as ligands

Homoleptic eight- and nine-coordinate U(IV) perchlorate complexes with sulfoxide ligands have been characterized crystallographically. Crystals of [U(dmso)₈](ClO₄)₄ · 0.75CH₃NO₂, [U(dmso)₉](ClO₄)₄ · 4dmso (dmso = dimethyl sulfoxide), and [U(tmso)₈](ClO₄)₄ · 2tmso (tmso = tetramethylene sulfoxide) were found to have dodecahedral, tricapped trigonal prismatic, and square antiprismatic geometries, respectively. Average U-O bond distances in [U(dmso)₈](ClO₄)₄ · 0.75CH₃NO₂, [U(dmso)₉](ClO₄)₄ · 4dmso, and [U(tmso)₈](ClO₄)₄ · 2tmso are 2.35(3), 2.41 (4), and 2.35(3) Å, respectively. Furthermore, it was found that [U(dmso)₈]⁴⁺ is in equilibrium with [U(dmso)₉]⁴⁺ in CH₃NO₂ solution containing dmso. Thermodynamic parameters for such an equilibrium are as follows: K (25 °C) = 3.4 ± 0.2 dm³ mol⁻¹, ΔH = −54.9 ± 4.5 kJ mol⁻¹, and ΔS = −174 ± 15 J K⁻¹ mol⁻¹.     

Pharmacology of a new tritiated endomorphin-2 analog containing the proline mimetic cis-2-aminocyclohexanecarboxylic acid

As part of ongoing work aimed at generating proteolytically stable, readily applicable, radiolabeled endomorphin-2 (EM-2) analogs for elucidation of the topological requirements of peptide binding to μ-opioid receptors, we report here on the synthesis, radiolabeling, binding kinetics and binding site distribution of an EM-2 analog in which Pro² is replaced by 2-aminocyclohexanecarboxylic acid, ACHC. [³H][(1S,2R)ACHC]²EM-2 (specific activity 63.49 Ci × mmol⁻¹) bound specifically to its binding sites with high affinity (K_D = 0.55 ± 0.06 nM) and saturably, yielding a receptor density, B_max of 151 ± 4 fmol × mg protein⁻¹ in rat brain membranes. A similar affinity value was obtained in kinetic assays. Both Na⁺ and Gpp(NH)p decreased the affinity, proving the agonist character of the radioligand. Specific μ-opioid ligands displaced the radioligand with much higher affinities than did δ- and κ-ligands. The autoradiographic distribution of the binding sites of [³H][(1S,2R)ACHC]²EM-2 agreed well with the known locations of the μ-opioid receptors in the rat brain. In consequence of its high affinity, selectivity and enzymatic resistance [19], the new radioligand will be a good tool in studies of the topographical requirements of μ-opioid-specific peptide binding.     

One-dimensional azido bridge [1-ethyl-2-(phenylazo)imidazole]manganese(II): Structure of low bridge angle system and magnetism

The reaction of 1-ethyl-2-(phenylazo)imidazole (PaiEt), NaN₃ and Mn(OAc)₂ · 4H₂O at 1:2:1 molar ratio has isolated azido bridge 1-D coordination polymer. In monomeric unit of the complex, MnN₆ distorted octahedral coordination is achieved by two EO-N₃, two EE-N₃ and N,N′-chelation of PaiEt. Bridge angle Mn-(EO)N₃-Mn is 98.55(10)°. Variable temperature (300-2 K) magnetic measurements determine J values −13.63 ± 0.10 and 2.31 ± 0.15 cm⁻¹ and support antiferromagnetic (EE-N₃) and ferromagnetic (EO-N₃) interaction, respectively. Maximum susceptibility (χ_M = 0.0251 cm³ mol⁻¹) is observed at 43 K.     

Supramolecular networks of dinuclear copper(II): Synthesis, crystal structure and magnetic study

The complexes [Cu₂(ox)(phen)₂(H₂O)₂](NO₃)₂ (1), [Cu₂(sq)(pmdien)₂(H₂O)₂](ClO₄)₂ (2) and {[Cu₃(pdc)₃(4,4′-bipy)_1.5(H₂O)_2.25] · 2.5(H₂O)}_n (3) [phen = 1,10-phenanthroline; pmdien = N,N,N′,N′,N″-pentamethyldiethylenetriamine; 4,4′-bipy = 4,4′-bipyridine; ox = oxalate dianion; sq = squarate dianion and pdc = pyridine 2,6-dicarboxylate] have been synthesized and characterized by X-ray single crystal structure determination, low temperature magnetic measurement and thermal study. Structure determination reveals that 1 and 2 are dinuclear copper(II) complexes bridged by oxalate and squarate dianions, respectively, while 3 is a hexanuclear species formed by three Cu(pdc)(H₂O)-(4,4′-bipy)-Cu(pdc)(H₂O) fragments, connected through long Cu-O(pdc) bonds in a centrosymmetric arrangement. In complex 1 H-bonds occurring between the coordinated water molecules and lattice nitrate anions result in eight-membered ring clusters with the concomitant formation of 1D supramolecular chain. The adjacent chains undergo π-π stacking forming a 2D architecture. In the crystal of 3 an extensive H-bonding scheme gives rise to a 3D supramolecular network. Low temperature magnetic study shows a strong antiferromagnetic coupling in 1 (J = −288 ± 2 cm⁻¹, g = 2.21 ± 0.01, R = 1.2 × 10⁻⁶); and a very weak interaction in 2 and 3, the best-fit parameters being: J = −0.21 cm⁻¹, g = 2.12 ± 0.01, R = 1.1 × 10⁻⁶ (2) and J = −1.34 cm⁻¹ ± 0.1, g = 2.14 ± 0.01, R = 1.2 × 10⁻⁶ (3) (R defines as .     

Distribution and residual activity of two insecticidal proteins, avidin and aprotinin, expressed in transgenic tobacco plants, in the bodies and frass of Spodoptera litura larvae following feeding

To understand how a major cosmopolitan pest responds to two very different insecticidal proteins and to determine whether herbivorous insects and their frass could be environmental sources of recombinant proteins from transgenic plants, Spodoptera litura (Fab.) (Lepidoptera, Noctuidae) larvae were fed on tobacco leaves expressing either the biotin-binding protein, avidin, or the protease inhibitor, aprotinin. Control larvae received non-transgenic tobacco. Samples of larvae were taken after 5, 6 or 7 days’ feeding and frass was collected after two 24-h periods at 6 and 7 days. Insects in all treatments grew significantly during the experiment, but the avidin-fed larvae were significantly smaller than the others on Day 7. Avidin was found in all samples of avidin-fed larvae (7.0±0.86 ng mg⁻¹, n=45), at a lower level than in their frass (31.9±5.08 ng mg⁻¹, n=30), and these frass levels were lower than those of the the leaves fed to the larvae (69.0±6.71 ng mg⁻¹, n=45). All of the avidin detected in these samples was capable of binding biotin. On average, between 10 and 28% of avidin was recovered with the methods used, whereas almost full recovery of aprotinin was effected. Aprotinin levels in larvae (8.2±0.53 ng mg⁻¹, n=45) were also lower than aprotinin levels in frass (77.4±6.9 ng mg⁻¹, n=30), which were somewhat lower than those in the leaves fed to the larvae (88.6±2.51 ng mg⁻¹, n=45). Approximately half the trypsin-binding ability of aprotinin was lost in larvae, and in frass, aprotinin had lost about 90% of its ability to bind trypsin.     

Physiological,morphological and anatomical trait variations between winter and summer leaves of Cistus species

Morphological, anatomical and physiological summer and winter leaf traits of Cistus incanus subsp. incanus, C. salvifolius and C. monspeliensis growing at the Botanical garden of Rome were analyzed. With regard to differences between summer and winter leaves of the considered species, leaf thickness (L) was 21% higher in summer than in winter leaves (mean of the considered species) and this increase was mostly the result of the increased palisade parenchyma thickness over the spongy parenchyma one (24 and 16% higher in summer than in winter leaves, respectively). Leaf mass area (LMA) and leaf tissue density (LTD) were 38% and 17% higher in summer than in winter leaves, respectively (mean of the considered species). The photosynthetic rate (P_N), stomatal conductance (g_s) and chlorophyll content (Chl) of summer leaves were 54%, 17% and 14% lower, respectively, than in winter leaves. C. monspeliensis summer leaves had the highest LMA, LTD, adaxial cuticle thickness (14.6 ± 1.8 mg cm⁻², 1091 ± 94 mg cm⁻³, and 5.8 ± 1.7 μm, respectively) and the lowest mesophyll intercellular spaces (f_ias 38 ± 3%). Moreover, C. monspeliensis had the highest P_N in summer (2.6 ± 0.1 μmol m⁻² s⁻¹) and C. incanus the highest P_N and WUE (84% and 59% higher than the other species) in the favorable period, associated to a higher f_ias (42 ± 2%). C. salvifolius had the highest P_N (54% higher than the other species) in winter. The plasticity index could allow a better interpretation of the habitat preference of the considered species. The physiological plasticity (PI_p = 0.39, mean value of the considered species) was higher than the morphological (PI_m = 0.22, mean value) and anatomical (PI_a = 0.13, mean value) plasticity. Moreover, among the considered species, C. salvifolius and C. incanus are characterized by a larger PI_a (0.14, mean value) which seems to be correlated with their wider ecological distribution and the more favorable conditions of the environments where they naturally occur. The highest PI_m (0.29) of C. monspeliensis indicates that it can play a high adaptive role in highly stressed environments, like fire degraded Mediterranean areas in which it occurs.     

An in vitro propagation protocol of two submerged macrophytes for lake revegetation in east China

Thirty-six programs have been set up to revegetate the degraded lake wetlands in east China since 2002. Most projects however faced deficiency of submerged macrophyte propagules. To solve the problem, alternative seedling sources must be found besides traditional field collection. This paper deals with an in vitro propagation protocol for two popularly used submerged macrophytes, Myriophyllum spicatum L. and Potamogeton crispus L. Full strength Murashige and Skoog-based liquid media (MS) plus 3% sucrose in addition to 0–2.0 mg l⁻¹ 6-benzylaminopurine (BA) and 0–1.0 mg l⁻¹ indoleacetic acid (IAA) were tried for shoot regeneration. Meanwhile, full, half or quarter strength MS in addition to 0, 0.1 or 0.2 mg l⁻¹ naphthaleneacetic acid (NAA) were tested for root induction, respectively. Results indicated that both species had the ability of regeneration from stem fragments in MS without further regulators. However, the addition of 2.0 mg l⁻¹ BA with 0.2 or 1.0 mg l⁻¹ IAA in MS drastically stimulated the regeneration efficiency of M. spicatum, while the addition of 2.0 mg l⁻¹ BA with 0.2 or 0.5 mg l⁻¹ IAA in MS significantly stimulated that of P. crispus. For root induction, full strength MS in combination with 0.1or 0.2 mg l⁻¹ NAA was preferred by M. spicatum, and the same MS without or with 0.1 mg l⁻¹ NAA was preferred by P. crispus. Seedlings of each species produced from tissue culture room had a 100% survival rate on clay, sandy loam or their mixture (1:1) in an artificial pond, and phenotypic plasticity was exhibited when the nutrient levels varied among the three types of sediments. This acclimation of seedlings helped develop the shoot and root systems, which ensured seedling quality and facilitated the transplantation. Our study has established an effective protocol to produce high quality seedlings for lake revegetation programs at a larger scale. Since the two species we tested represent different regeneration performances in nature but shared similar in vitro propagation conditions, this study has indicated a potentially wide use of the common media for preparing seedlings of other submerged macrophytes.     

Initial synthesis and characterization of an immobilized heat shock protein 90 column for online determination of binding affinities

Heat shock protein 90α (Hsp90α) was immobilized on aminopropyl silica via the N terminus to create the Hsp90α(NT) column or via the C terminus to create the Hsp90α(CT) column. Binding to the exposed C terminus on the Hsp90α(NT) column was characterized using frontal chromatography and the C-terminus ligands coumermycin A₁ (CA1) and novobiocin (NOVO). The calculated K_d values were 220 ± 110 nM (CA1) and 100 ± 20 nM (NOVO). Nonlinear chromatography was used to determine the association and dissociation rate constants associated with the NOVO-Hsp90α complex: 22.2 ± 8.8 μM⁻¹ s⁻¹ and 2.7 ± 0.6 s⁻¹, respectively. Binding to the exposed N terminus on the Hsp90α(CT) column was characterized using frontal chromatography. The K_d values of the N-terminus ligands geldanamycin (GM, 90 ± 50 nM), 17-allylamino-17-demethoxygeldanamycin (17-AAG, 210 ± 50 nM), and radicicol (RAD, 20 ± 9 nM) were consistent with previously reported values. The effect of the immobilization on ATPase activity was investigated through the determination of IC₅₀ values for inhibition of ATPase activity on the Hsp90α(CT) column. The IC₅₀ for GM was 2.80 ± 0.18 μM, and the relative IC₅₀ values were 17-AAG > GM > RAD, in agreement with previously reported values and indicating that immobilization had not affected ATPase activity or sensitivity to inhibition.     

Mechanistic studies on monodentate-ligand substitution of five-coordinate trigonal-bipyramidal platinum (II) complexes with tris[2-(diphenylphosphino)ethyl]phosphine

Reaction of the five-coordinate trigonal-bipyramidal platinum(II) complex, [Pt(pt)(pp₃)](BF₄) (pt = 1-propanethiolate, pp₃ = tris[2-(diphenylphosphino)ethyl]phosphine), with I⁻ in chloroform gave the five-coordinate square-pyramidal complex with a dissociated terminal phosphino group and an apically coordinated iodide ion in equilibrium. The thermodynamic parameters for the equilibrium between the trigonal-bipyramidal and square-pyramidal geometries, [Pt(pt)(pp₃)]⁺ + I⁻ ? [PtI(pt) (pp₃)], and the kinetic parameters for the chemical exchange were obtained as follows: , ΔH⁰ = − 10 ± 2.4 kJ mol⁻¹, ΔS⁰ = − 36 ± 10 J K⁻¹ mol⁻¹, , ΔH^‡ = 34 ± 4.7 kJ mol⁻¹, ΔS^‡ = − 50 ± 21 J K⁻¹ mol⁻¹. The square-planar trinuclear platinum(II) complex was formed by bridging reaction of one of the terminal phosphino groups of trigonal-bipyramidal [PtCl(pp₃)]Cl with trans-[PtCl₂(NCC₆H₅)₂] in chloroform. From these facts, ligand substitution reactions of [PtX(pp₃)]⁺ (X = monodentate anion) are expected to proceed via an intermediate with a dissociated phosphino group. The rate constants for the chloro-ligand substitution reactions of [PtCl(pp₃)]⁺ with Br⁻ and I⁻ in chloroform approached the respective limiting values as concentrations of the entering halide ions are increased. These kinetic results confirmed the preassociation mechanism in which the square pyramidal intermediate with a dissociated phosphino group and an apically coordinated halide ion is present in the rapid pre-equilibrium.     

Synthesis, characterization, and magnetic properties of new binuclear CuCu bis(oxamato) complexes

Two new neutral, binuclear Cu^IICu^II bis(oxamato) complexes with the formula [Cu₂(opba)(pmdta)(MeOH)] · 1/2MeOH · dmf (3) and [Cu₂(nabo)(pmdta)(MeOH)] (4), with opba = o-phenylene-bis(oxamato), nabo = 2,3-naphthalene-bis(oxamato), pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine and dmf = dimethylformamide have been synthesized and their crystal structures have been determined. The structure of 3 consists of dimeric [Cu₂(opba)(pmdta)(MeOH)] entities, joined together by mutual intermolecular Cu?O contacts of the Cu²⁺ ion of one [Cu(opba)]²⁻ complex fragment and one carboxylate atom of the oxamato group of a second [Cu(opba)]²⁻ complex fragment. The structure of 4 consists of neutral binuclear complexes joined together by hydrogen bonds and π-π interactions, giving rise to an unique supramolecular 1D-chain. The magnetic properties of 3 and 4 were studied by susceptibility measurements versus temperature. For the intramolecular J parameter, identical values of (−114 ± 2) cm⁻¹ (3) and (−112 ± 2) cm⁻¹ (4) were obtained.