The effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis)

To investigate the effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis), we measured the following: (1) the resting oxygen consumption rate $ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{rest}}}} } \right) $ , critical swimming speed (U _crit) and active oxygen consumption rate $ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} } \right) $ of fish at acclimation temperatures of 10, 15, 20, 25 and 30 °C and (2) the $ \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $ , U _crit and $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ of both exercise-trained (exhaustive chasing training for 14 days) and control fish at both low and high acclimation temperatures (15 and 25 °C). The relationship between U _crit and temperature (T) approximately followed a bell-shaped curve as temperature increased: U _crit = 8.21/{1 + [(T ? 27.2)/17.0]²} (R ² = 0.915, P < 0.001, N = 40). The optimal temperature for maximal U _crit (8.21 BL s^?1) in juvenile qingbo was 27.2 °C. Both the $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ and the metabolic scope (MS, $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} - \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $ ) of qingbo increased with temperature from 10 to 25 °C (P < 0.05), but there were no significant differences between fish acclimated to 25 and 30 °C. The relationships between $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ or MS and temperature were described as $ {\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} = 1,214.29/\left\{ {1 + \left[ {\left( {T - 28.8} \right)/10.6} \right]^{2} } \right\}\;\left( {R^{2} = 0.911,\;P < 0.001,\;N = 40} \right) $ and MS = 972.67/{1 + [(T ? 28.0)/9.34]²} (R ² = 0.878, P < 0.001, N = 40). The optimal temperatures for $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ and MS in juvenile qingbo were 28.8 and 28.0 °C, respectively. Exercise training resulted in significant increases in both U _crit and $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ at a low temperature (P < 0.05), but training exhibited no significant effect on either U _crit or $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ at a high temperature. These results suggest that exercise training had different effects on swimming performance at different temperatures. These differences may be related to changes in aerobic metabolic capability, arterial oxygen delivery, available dissolved oxygen, imbalances in ion fluxes and stimuli to remodel tissues with changes in temperature.     

Three years of soil respiration in a mature eucalypt woodland exposed to atmospheric CO<Subscript>2</Subscript> enrichment

Large amounts of atmospheric N deposition cause negative effects on ecosystems. Effective mitigation strategies require the sources of N deposition to be identified and the contributions from individual sources to be quantified. Determination of the isotopic composition represents a useful approach in source apportionment. In this study, the δ¹⁵N-NH_x of wet and dry atmospheric deposition and the main NH₃ emission sources were analyzed at an urban, a suburban and a rural site in the Taihu Lake region of China. The 2-year average δ¹⁵N-\( {\text{NH}}_{4}^{ + } \) of precipitation was ? 3.0 ± 2.3, ? 3.1 ± 2.8 and ? 0.5 ± 2.8‰ for the urban, suburban and rural sites, respectively. These values were much lower than the corresponding values for particulate \( {\text{NH}}_{4}^{ + } \) (15.9, 15.2 and 14.3‰ at the urban, suburban and rural sites, respectively), and much higher than those of gaseous δ¹⁵N-NH₃ (? 16.7, ? 18.2 and ? 17.4‰ at the urban, suburban and rural sites, respectively). The δ¹⁵N-NH₃ of NH₃ from the main emission sources ranged from ? 30.8 to ? 3.3‰ for volatilized fertilizer, from ? 35.1 to ? 10.5‰ for emissions from a pig farm, and ? 24.7 to ? 11.3‰ for emissions from a dairy farm. Temporal variations of deposition δ¹⁵N-NH_x indicated that δ¹⁵N-NH_x values were lower in summer and autumn, but higher in winter and spring for both precipitation \( {\text{NH}}_{4}^{ + } \)-N and gaseous NH₃-N. Weather conditions such as temperature and precipitation significantly influenced the spatial and temporal distribution of isotope values of the deposition. Analysis of δ¹⁵N-NH_x in deposition and emission sources identified volatilized fertilizer and livestock wastes as the origins of both gaseous NH₃-N and precipitation \( {\text{NH}}_{4}^{ + } \)-N over the region. A stable isotope mixing model estimated that volatilized fertilizer and animal excreta contributed more than 65% to precipitation \( {\text{NH}}_{4}^{ + } \)-N, more than 60% to particulate \( {\text{NH}}_{4}^{ + } \)-N, and more than 75% to gaseous NH₃-N.     

Relative CO2/NH3 Permeabilities of Human RhAG, RhBG and RhCG

Mammalian glycosylated rhesus (Rh) proteins include the erythroid RhAG and the nonerythroid RhBG and RhCG. RhBG and RhCG are expressed in multiple tissues, including hepatocytes and the collecting duct (CD) of the kidney. Here, we expressed human RhAG, RhBG and RhCG in Xenopus oocytes (vs. H₂O-injected control oocytes) and used microelectrodes to monitor the maximum transient change in surface pH (ΔpH_S) caused by exposing the same oocyte to 5 % CO₂/33 mM HCO₃ ^? (an increase) or 0.5 mM NH₃/NH₄ ⁺ (a decrease). Subtracting the respective values for day-matched, H₂O-injected control oocytes yielded channel-specific values (*). $({\Updelta {\text{pH}}_{\text{S}}^{*} })_{{{\text{CO}}_{ 2} }}$ and $({ - \Updelta {\text{pH}}_{\text{S}}^{*} })_{{{\text{NH}}_{ 3} }}$ were each significantly >0 for all channels, indicating that RhBG and RhCG—like RhAG—can carry CO₂ and NH₃. We also investigated the role of a conserved aspartate residue, which was reported to inhibit NH₃ transport. However, surface biotinylation experiments indicate the mutants RhBG_D178N and RhCG_D177N have at most a very low abundance in the oocyte plasma membrane. We demonstrate for the first time that RhBG and RhCG—like RhAG—have significant CO₂ permeability, and we confirm that RhAG, RhBG and RhCG all have significant NH₃ permeability. However, as evidenced by $({\Updelta {\text{pH}}_{\text{S}}^{*} })_{{{\text{CO}}_{ 2} }} /({ - \Updelta {\text{pH}}_{\text{S}}^{*} })_{{{\text{NH}}_{ 3} }}$ values, we could not distinguish among the CO₂/NH₃ permeability ratios for RhAG, RhBG and RhCG. Finally, we propose a mechanism whereby RhBG and RhCG contribute to acid secretion in the CD by enhancing the transport of not only NH₃ but also CO₂ across the membranes of CD cells.     

Litterfall and litter nutrient dynamics under cocoa ecosystems in lowland humid Ghana

There have been few studies quantifying litterfall, standing litterstock and gross litter decomposition following forest conversion to plantation crops such as cocoa. Additionally, an assessment of changing processes occurring in forest floor litter systems with plantation age is lacking. We investigated litterfall production, standing litter changes and litter decomposition along a chronosequence of shaded cocoa farm fields (secondary forest, 3, 15 and 30-year-old) in the moist semi-deciduous forest belt in the Ashanti Region of Ghana in West Africa over 24 months. Mean annual litterfall production differed significantly among study sites and ranged from 5.0 to 10.4 Mg DM ha^?1. Similarly, standing litter differed significantly between land-use /plot ages. The results showed significant differences in quality between litter from forest and litter from cocoa plantations. Litterfall from forests had higher concentrations of nitrogen and lower concentration of soluble polyphenols and lignin compared to litter from cocoa systems. Monthly decomposition coefficients (k) estimated as $ k = {{\left( {{\text{A}} - \left( {{\text{L}}_1 - {\text{L}}_0 } \right)} \right)} \mathord{\left/ {\vphantom {{\left( {{\text{A}} - \left( {{\text{L}}_1 - {\text{L}}_0 } \right)} \right)} {\left( {{{\left( {{\text{L}}_1 + {\text{L}}_0 } \right)} \mathord{\left/ {\vphantom {{\left( {{\text{L}}_1 + {\text{L}}_0 } \right)} 2}} \right. } 2}} \right)}}} \right. } {\left( {{{\left( {{\text{L}}_1 + {\text{L}}_0 } \right)} \mathord{\left/ {\vphantom {{\left( {{\text{L}}_1 + {\text{L}}_0 } \right)} 2}} \right. } 2}} \right)}} $ , where A is litterfall production during the month, L₀ is the standing litterstock at the beginning of the month and L₁ is the standing litterstock at the end of the month. Annual decomposition coefficients (k _L ) were similar in cocoa systems (0.221–0.227) but higher under secondary forests (0.354). Correlations between litter quality parameters and the decomposition coefficient showed nitrogen and lignin concentrations as well as ratios that include nitrogen are the best predictors of decomposition for the litters studied. Our results confirm the hypothesis that decomposition decreases following forest conversion to shaded cocoa systems because of litter quality changes and that decomposition rates correlate to litter quality differences between forest and cocoa ecosystems. The study also showed that standing litter pools and litterfall production in recently converted cocoa plantations are low compared to secondary forests or mature cocoa systems. Management strategies involving the introduction of upper canopy species during plantation development with corresponding replacement of tree mortality with diverse fast growing species will provide high quality and quantity litter resources.     

Proton transfer reactions in aqueous solutions of pyridoxamine phosphate

UV-visible and ¹³C NMR measurements described in the literature and our ³¹P NMR measurements support the following mechanism of proton transfer reactions in aqueous solutions of pyridoxamine phosphate: Only the tautomeric equilibrium between neutral form, A _N, and zwitterion, A _Z, which is analogous to the tautomeric equilibrium of 3-hydroxypyridine in aqueous solution, is important, and that equilibrium does not change upon the dissociation of the second phosphate proton. With these simplifying assumption, we have simulated the relaxation spectrum of the proton transfer reactions of pyridoxamine phosphate in water using parameters from analogous reactions and compared it with our ultrasound and temperature jump measurements. We have found that the relaxation process measured by the temperature jump experiment is mainly caused by the overall reaction A _N=A _Z (or A _N ^- =A _Z ^- ) and the ultrasound absorption at the isoelectric point between pK₂ and pK₃ is mainly caused by the overall reaction .     

Hyperfine interactions and electron distribution in FeIIFeI and FeIFeI models for the active site of the [FeFe] hydrogenases: Mössbauer spectroscopy studies of low-spin FeI

Mössbauer studies of [{μ-S(CH₂C(CH₃)₂CH₂S}(μ-CO)Fe^IIFe^I(PMe₃)₂(CO)₃]PF₆ (1 _OX ), a model complex for the oxidized state of the [FeFe] hydrogenases, and the parent Fe^IFe^I derivative are reported. The paramagnetic 1 _OX is part of a series featuring a dimethylpropanedithiolate bridge, introducing steric hindrance with profound impact on the electronic structure of the diiron complex. Well-resolved spectra of 1 _OX allow determination of the magnetic hyperfine couplings for the low-spin distal Fe^I ( $ {\text{Fe}}^{\text{I}} _{\text{ D}} $ Fe D I ) site, A _x,y,z  = [?24 (6), ?12 (2), 20 (2)] MHz, and the detection of significant internal fields (approximately 2.3 T) at the low-spin ferrous site, confirmed by density functional theory (DFT) calculations. Mössbauer spectra of 1 _OX show nonequivalent sites and no evidence of delocalization up to 200 K. Insight from the experimental hyperfine tensors of the Fe^I site is used in correlation with DFT to reveal the spatial distribution of metal orbitals. The Fe–Fe bond in [Fe₂{μ-S(CH₂C(CH₃)₂CH₂S}(PMe₃)₂(CO)₄] (1) involving two $ d_{{z^{2} }} $ d z 2 -type orbitals is crucial in keeping the structure intact in the presence of strain. On oxidation, the distal iron site is not restricted by the Fe–Fe bond, and thus the more stable isomer results from inversion of the square pyramid, rotating the $ d_{{z^{2} }} $ d z 2 orbital of $ {\text{Fe}}^{\text{I}} _{\text{ D}} $ Fe D I . DFT calculations imply that the Mössbauer properties can be traced to this $ d_{{z^{2} }} $ d z 2 orbital. The structure of the magnetic hyperfine coupling tensor, A, of the low-spin Fe^I in 1 _OX is discussed in the context of the known A tensors for the oxidized states of the [FeFe] hydrogenases.     

Adiabatic transformability hypothesis of human locomotion

It is hypothesized that metabolic and mechanical changes in human locomotion associated with changes in speed v are constrained by two attractive strategies: $Q_{{\text{metab}}} = 1{\text{ and }}\Delta Q_{{\text{metab}}} /\Delta v = {\text{a}}$ positive definite constant. $Q_{{\text{metab}}} = \Delta {\rm E}_{\text{k}} {\text{s}}^{{\text{ - 1}}} /{\text{ml O}}_{\text{2}} {\text{s}}^{{\text{ - 1}}} $ where ΔEs^?1 is the summed increments and decrements per unit time in the translational and rotational kinetic energies of the body's segments and ml O₂s^?1 is the rate at which chemical energy is dissipated. The expected constancy of ΔQ _metab/Δv _metab was derived from an extension of Ehrenfest's adiabatic hypothesis by which transformations (increases, decreases) in locomotion v can be considered as adiabatic, even though the biological conditions are nonconservative and non-rate-limited. The expected significance of Q _metab=1 was derived from stability considerations of the symmetry per stride of stored and dissipated energy. An experimental evaluation was provided by collecting metabolic and mechanical measures on walking (10 subjects) and running (9 subjects) at progressively greater treadmill speeds but within the aerobic limit. Results revealed that walking was restricted to ometab ? 1 with a nonlinear trajectory in v×Q _metab coordinates shaped by Q _metab=1 (primarily) and the constancy of ΔQ _metab/Δv. Running satisfied Q _metab > 1, with a linear trajectory in v×Q _metab coordinates conforming to ΔQ _metab/_Δv=a constant, with the constant predicted from invariants in the mechanical space v×ΔE _ks^?1. Results also suggested that the metabolic costs of running might be predictable from measures made in the v×ΔE _ks^?1 space.     

Release of non-exchangeable {}^{{{\text{15}}}}{\text{NH}}^{{\text{ + }}}_{{\text{4}}} from subgrade, decomposed granite substrates and uptake by non-mycorrhizal and mycorrhizal California native annual grass, Vulpia microstachys

Release rates of recently fixed $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ from non-exchangeable interlayer sites in 2:1 silicate minerals were determined for decomposed granite (DG) saprolites from three locations in California, USA. Recently-fixed $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ release from the DG substrate was quantified by extracting diffused $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ with H-resin, as well as a native, annual grass Vulpia microstachys. The $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ release data varied with via the method of extraction, which included H-resin pre-treatments (Na⁺ or H⁺) and V. microstachys uptake (mycorrhizal inoculated or uninoculated). After 6 weeks (1008 h), more $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ was recovered from fixed interlayer positions by the H-resins as compared to uptake by V. microstachys. The H⁺ treated H-resins recovered more released $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ (≈94 mg ${\text{NH}}^{{\text{ + }}}_{{\text{4}}} - {\text{N}}\;{\text{kg}}^{1} $ or (12%) of total fixed $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ ) in two of the three DG samples as compared to the Na⁺ treated resins, (which recovered ≈70–78 mg ${\text{NH}}^{{\text{ + }}}_{{\text{4}}} - {\text{N}}\;{\text{kg}}^{{{\text{ - 1}}}} $ (or 9–10%) of the total fixed $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ ). The V. microstachys assimilated 8–9% of the total fixed $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ with mycorrhizal inoculum as compared to only 2% without a mycorrhizal inoculum, over the same time period. The fixed $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ release kinetics from the H-resin experiments were most accurately described by first order and power function models, and can be characterized as biphasic using a heterogeneous diffusion model. Uptake of both the ¹⁵N and ambient, unlabelled N from the soils was closely related to plant biomass. There was no significant difference in percent of N per unit of biomass between the control and mycorrhizal treatments. The findings presented here indicate that observed, long-term $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ release rates from DG in studies utilizing resins, may overestimate the levels of fixed $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ made available to plants and microorganisms. Additionally, the study suggested that mycorrhizae facilitate the acquisition and plant uptake of fixed $ {\text{NH}}^{{\text{ + }}}_{{\text{4}}} $ , resulting in markedly increased plant biomass production.     

Performance and kinetics of ANAMMOX granular sludge with pH shock in a sequencing batch reactor

As an efficient and cost-effective nitrogen removal process, anaerobic ammonium oxidation (ANAMMOX) could be well operated at suitable pH condition. However, pH shock occurred in different kinds of wastewater and affected ANANNOX process greatly. The present research aimed at studying the performance and kinetics of ANAMMOX granular sludge with pH shock. When influent pH was below 7.5, effluent \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{2}^{ - }\)–N increased with decreasing pH. At Ph 6.0, effluent \({\text{NO}}_{2}^{ - }\)–N approached 100 mg/L, and the ratios of \(\Delta {\text{NO}}_{2}^{ - } - {\text{N}}:\Delta {\text{NH}}_{4}^{ + } - {\text{N and }}\Delta {\text{NO}}_{3}^{ - } - {\text{N}}:\Delta {\text{NH}}_{4}^{ + } - {\text{N}}\) approached 2.2 and 1.3, respectively. Both greatly deviated from theoretical values. When influent pH was above 7.5, effluent \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{2}^{ - }\)–N increased with increasing pH. At pH 9.0, ammonium removal rate (ARR) and nitrite removal rate (NRR) decreased to 0.011 ± 0.004 and 0.035 ± 0.004 kg/(m³·d), respectively. Besides, \(\Delta {\text{NO}}_{2}^{ - }\)–N:\(\Delta {\text{NH}}_{4}^{ + }\)–N deviated from theoretical value. Longer recovery time from pH 9.0 than from pH 6.0 indicated that alkaline surroundings inhibited anaerobic ammonium oxidizing bacteria (AAOB) greater. The sludge settling velocity was 2.15 cm/s at pH 7.5. However, it decreased to 2.02 cm/s when pH was 9.0. Acidic pH had little effect on sludge size, but disintegration of ANAMMOX granule was achieved with pH of 9.0. The Bell-shaped (A) model and the Ratkowsky model were more applicable to simulate the effect resulting from pH shock on ANAMMOX activity (R² > 0.95), and both could describe ANAMMOX activity well with pH shock. They indicated that q_max was 0.37 kg \(\Delta {\text{NH}}_{4}^{ + }\)–N/(kgMLSS·d) at the optimum pH value (7.47) in present study. The minimum pH during which ANAMMOX occurred was 5.68 while the maximum pH for ANAMMOX reaction was 9.26. Based on nitrogen removal performance with different pH, strongly acidic (pH ≤ 6.5) or alkaline (pH ≥ 8.5) inhibited ANAMMOX process. Besides, ANAMMOX appeared to be more susceptible to alkaline wastewater. Compared to extremely acidic condition (low pH), extremely alkaline condition (high pH) affected ANAMMOX granules much more.     

Estimation of viscosity from passage time of liquids flowing through a microchannel array

Recently, a microchannel flow analyzer (MC-FAN) has been used to study the flow properties of blood. However, the correlation between blood passage time measured by use of the MC-FAN and hemorheology has not been clarified. In this study, a simple model is proposed for estimation of liquid viscosity from the passage time t _p of liquids. The t _p data for physiological saline were well represented by the model. According to the model, the viscosity of Newtonian fluids was estimated reasonably well from the t _p data. For blood samples, although the viscosity $ \eta_{\text{mc}} $ estimated from t _p was shown to be smaller than the viscosity $ \eta_{{450{\text{s}}^{ - 1} }} $ measured by use of a rotatory viscometer at a shear rate of 450 s^?1, $ \eta_{\text{mc}} $ was correlated with $ \eta_{{450{\text{s}}^{ - 1} }} $ . An empirical equation for estimation of $ \eta_{{450{\text{s}}^{ - 1} }} $ from $ \eta_{\text{mc}} $ of blood samples is proposed.     

Growth of Wolinella succinogenes with polysulphide as terminal acceptor of phosphorylative electron transport

Polysulphide was formed according to reaction (1), when tetrathionate was (1) $${\text{S}}_4 {\text{O}}_6^{2 - } + {\text{HS}}^ - \to 2{\text{S}}_2 {\text{O}}_3^{2 - } + {\text{S(O)}} + {\text{H}}^ + $$ added to an anaerobic buffer (pH 8.5) containing excess sulphide. S(O) denotes the zero oxidation state sulphur in the polysulphide mixture S _infn ^sup2- . The addition of formate to the polysulphide solution in the presence of Wolinella succinogenes caused the reduction of polysulphide according to reaction (2). The bacteria grew in a medium containing formate and sulphide, (2) $${\text{HCO}}_2^ - + {\text{S(O)}} + {\text{H}}2{\text{O}} \to {\text{HCO}}_3^ - + {\text{HS}}^ - + {\text{H}}^ + $$ when tetrathionate was continuously added. The cell density increased proportional to reaction (3) which represents the sum of reactions (1) and (3) $${\text{HCO}}_2^ - + {\text{S}}_{\text{4}} {\text{O}}_6^{2 - } + {\text{H}}2{\text{O}} \to {\text{HCO}}_3^ - + 2{\text{S}}_{\text{2}} {\text{O}}_3^{2 - } + 2{\text{H}}^ + $$ (2). The cell yield per mol formate was nearly the same as during growth on formate and elemental sulphur, while the velocity of growth was greater. The specific activities of polysulphide reduction by formate measured with bacteria grown with tetrathionate or with elemental sulphur were consistent with the growth parameters. The results suggest that W. succinogenes grow at the expense of formate oxidation by polysulphide and that polysulphide is an intermediate during growth on formate and elemental sulphur.     

Measurements of CO2 and CH4 evasion from UK peatland headwater streams

Peatland headwater streams are consistently supersaturated with respect to gaseous C and are known to degas CO₂ and CH₄ directly to the atmosphere. Using a combination of injection of a purposeful gas tracer (propane) and a soluble tracer (NaCl) we carried out 49 measurements of the gas transfer coefficient on 12 representative stream reaches to quantify the gas transfer rates of CO₂ and CH₄ in headwater (1st–3rd order) streams draining six UK peatlands. These were compared to measured stream reach physical variables, such as discharge and water travel time. Whilst we found that evasion rates were highly variable in space and time, $ {\text{K}}_{{{\text{CO}}_{2} }} $ (gas transfer coefficient of CO₂) was positively related to discharge. Individual study sites showed a high degree of variability in gas transfer rates; at all 49 sites median/mean values for $ {\text{K}}_{{{\text{CO}}_{2} }} $ were 0.087/0.157 and $ {\text{K}}_{{{\text{CH}}_{4} }} $ 0.092/0.176 min^?1. Median/mean instantaneous CO₂ and CH₄ evasion rates were 133/367 and 0.22/1.45 μg C m^?2 s^?1, respectively. Methane evasion rates were therefore more than two orders of magnitude lower than CO₂, with CH₄ invasion (rather than evasion) measured on 37 % of occasions. Our gas flux measurements from peatland headwater streams are higher than values previously used to estimate landscape scale fluxes and emphasise the importance of the evasion flux term in the overall carbon balance.     

Net ecosystem carbon exchange and the greenhouse gas balance of tidal marshes along an estuarine salinity gradient

Tidal wetlands are productive ecosystems with the capacity to sequester large amounts of carbon (C), but we know relatively little about the impact of climate change on wetland C cycling in lower salinity (oligohaline and tidal freshwater) coastal marshes. In this study we assessed plant production, C cycling and sequestration, and microbial organic matter mineralization at tidal freshwater, oligohaline, and salt marsh sites along the salinity gradient in the Delaware River Estuary over four years. We measured aboveground plant biomass, carbon dioxide (CO₂) and methane (CH₄) exchange between the marsh and atmosphere, microbial sulfate reduction and methanogenesis in marsh soils, soil biogeochemistry, and C sequestration with radiodating of soils. A simple model was constructed to estimate monthly and annually integrated rates of gross ecosystem production (GEP), ecosystem respiration (ER) to carbon dioxide ( \( {\text{ER}}_{{{\text{CO}}_{2} }} \) ) or methane ( \( {\text{ER}}_{{{\text{CH}}_{4} }} \) ), net ecosystem production (NEP), the contribution of sulfate reduction and methanogenesis to ER, and the greenhouse gas (GHG) source or sink status of the wetland for 2 years (2007 and 2008). All three marsh types were highly productive but evidenced different patterns of C sequestration and GHG source/sink status. The contribution of sulfate reduction to total ER increased along the salinity gradient from tidal freshwater to salt marsh. The Spartina alterniflora dominated salt marsh was a C sink as indicated by both NEP (~140 g C m^?2 year^?1) and ²¹⁰Pb radiodating (336 g C m^?2 year^?1), a minor sink for atmospheric CH₄, and a GHG sink (~620 g CO_2-eq m^?2 year^?1). The tidal freshwater marsh was a source of CH₄ to the atmosphere (~22 g C–CH₄ m^?2 year^?1). There were large interannual differences in plant production and therefore C and GHG source/sink status at the tidal freshwater marsh, though ²¹⁰Pb radiodating indicated modest C accretion (110 g C m^?2 year^?1). The oligohaline marsh site experienced seasonal saltwater intrusion in the late summer and fall (up to 10 mS cm^?1) and the Zizania aquatica monoculture at this site responded with sharp declines in biomass and GEP in late summer. Salinity intrusion was also linked to large effluxes of CH₄ at the oligohaline site (>80 g C–CH₄ m^?2 year^?1), making this site a significant GHG source (>2,000 g CO_2-eq m^?2 year^?1). The oligohaline site did not accumulate C over the 2 year study period, though ²¹⁰Pb dating indicated long term C accumulation (250 g C m^?2 year^?1), suggesting seasonal salt-water intrusion can significantly alter C cycling and GHG exchange dynamics in tidal marsh ecosystems.     

Stress fermentation strategies for the production of hyperthermostable superoxide dismutase from Thermus thermophilus HB27: effects of ions

In this study, we explored how ammonium and metal ion stresses affected the production of recombinant hyperthermostable manganese superoxide dismutase (Mn-SOD). To improve Mn-SOD production, fed-batch culture in shake flasks and bioreactor fermentation were undertaken to examine the effects of $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺ feeding. Under the optimized feeding time and concentrations of $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺, the maximal SOD activity obtained from bioreactor fermentation reached some 480 U/ml, over 4 times higher than that in batch cultivation (113 U/ml), indicating a major enhancement of the concentration of Mn-SOD in the scale-up of hyperthermostable Mn-SOD production. In contrast, when the fed-batch culture with appropriate $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺ feeding was carried out in the same 5-L stirred tank bioreactor, a maximal SOD concentration of some 450 U/ml was obtained, again indicating substantial increase in SOD activity as a result of $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺ feeding. The isoelectric point (pI) of the sample was found to be 6.2. It was highly stable at 90 °C and circular dichroism measurements indicated a high α-helical content of 70 % as well, consistent with known SOD properties. This study indicates that $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺ play important roles in Mn-SOD expression. Stress fermentation strategies established in this study are useful for large-scale efficient production of hyperthermostable Mn-SOD and may also be valuable for the scale-up of other extremozymes.     

The effect of micro-aerobic conditions on continuous ethanol production by Saccharomyces cerevisiae

Summary The effect of trace amounts of oxygen on the degree of ethanol inhibition in a continuous anaerobic culture of Saccharomyces cerevisiae was studied at the 100 gl ^–1 feed glucose concentration level. Results showed that the use of micro-aerobic conditions (0,5% of saturation) enhanced the utilisation of substrate by increasing the ethanol tolerance of the yeast without any significant decrease in the ethanol yield per unit substrate consumed. When the results were fitted to an equation of the form % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqcLbyacaqG8o% GaaeypaiqabY7agaqcaiaab6cadaWcaaGcbaqcLbyacaqGdbWaaSba% aSqaaKqzagGaae4CaaWcbeaaaOqaaKqzagGaae4qamaaBaaaleaaju% gGbiaabohaaSqabaqcLbyacqGHRaWkcaqGlbWaaSbaaSqaaKqzagGa% ae4CaaWcbeaaaaqcLbyacaGGUaWaaSaaaOqaaKqzagGaae4samaaBa% aaleaajugGbiaabchaaSqabaaakeaajugGbiaabUeadaWgaaWcbaqc% LbyacaqGWbaaleqaaKqzagGaey4kaSIaaeywamaaBaaaleaajugGbi% aabchacaqGZbaaleqaaKqzagGaaiOlaiaacIcacaqGdbWaaSbaaSqa% aKqzagGaae4CaiaabAgaaSqabaqcLbyacqGHsislcaqGdbWaaSbaaS% qaaKqzagGaae4CaaWcbeaajugGbiaacMcaaaaaaa!6301!\[{\text{\mu = \hat \mu }}{\text{.}}\frac{{{\text{C}}_{\text{s}} }}{{{\text{C}}_{\text{s}} + {\text{K}}_{\text{s}} }}.\frac{{{\text{K}}_{\text{p}} }}{{{\text{K}}_{\text{p}} + {\text{Y}}_{{\text{ps}}} .({\text{C}}_{{\text{sf}}} - {\text{C}}_{\text{s}} )}}\]it was found that the values for % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabeiVdyaaja% aaaa!373F!\[{\text{\hat \mu }}\], K_s and Y_ps were the same as for the non-aerobic case while the ethanol inhibition constant, K_p , had increased from 5,2 to 14,0 gl ^–1.Notation C_sf feed substrate concentration - gl ^–1 - C_s substrate concentration gl ^–1 - C_p product concentration - gl ^–1 - C_x cell concentration - gl ^–1 - D dilution rate - h^-1 - K_s substrate saturation constant - gl ^–1 - K_p product inhibition constant - gl ^–1 - m maintenance coefficient - h^–1 - Y_ps product yield coefficient - g EtOH/g glucose - Y_xs cell yield coefficient - g cells/g glucose - specific growth rate - h^–1 - % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabeiVdyaaja% aaaa!373F!\[{\text{\hat \mu }}\] maximum specific growth rate - h^–1     

Minor stable carbon isotope fractionation between respired carbon dioxide and bulk soil organic matter during laboratory incubation of topsoil

A common assumption in paleoenvironmental reconstructions using soils is that the carbon isotope composition of soil-respired CO₂ is equivalent to the carbon isotope composition of bulk soil organic matter (SOM). However, the occurrence of a non-zero per mil carbon isotope enrichment factor between CO₂ and SOM (\(\varepsilon_{{{\text{CO}}_{ 2} - {\text{SOM}}}}\)) during soil respiration is the most widely accepted explanation for the down-profile increase in SOM δ¹³C values commonly observed in well-drained soils. In order to shed light on this apparent discrepancy, we incubated soil samples collected from the top 2 cm of soils with pure C₃ vegetation and compared the δ¹³C values of soil-respired CO₂ to the δ¹³C values of bulk SOM. Our results show near-zero \(\varepsilon_{{{\text{CO}}_{ 2} - {\text{SOM}}}}\) values (?0.3 to 0.4 ‰), supporting the use of paleosol organic matter as a proxy for paleo soil-respired CO₂. Significantly more negative \(\varepsilon_{{{\text{CO}}_{ 2} - {\text{SOM}}}}\) values are required to explain the typical δ¹³C profiles of SOM in well-drained soils. Therefore our results also suggest that typical SOM δ¹³C profiles result from either (1) a process other than carbon isotope fractionation between CO₂ and SOM during soil respiration or (2) \(\varepsilon_{{{\text{CO}}_{ 2} - {\text{SOM}}}}\) values that become increasingly negative as SOM matures.     

The Equilibria of Lipid–K<Superscript>+</Superscript> Ions in Monolayer at the Air/Water Interface

The effect of K⁺ ion interaction with monolayers of phosphatidylcholine (lecithin, PC) or cholesterol (Ch) was investigated at the air/water interface. We present surface tension measurements of lipid monolayers obtained using a Langmuir method as a function of K⁺ ion concentration. Measurements were carried out at 22°C using a Teflon trough and a Nima 9000 tensiometer. Interactions between lecithin and K⁺ ions or Ch and K⁺ ions result in significant deviations from the additivity rule. An equilibrium theory to describe the behavior of monolayer components at the air/water interface was developed in order to obtain the stability constants and area occupied by one molecule of lipid–K⁺ ion complex (LK⁺). The stability constants for lecithin–K⁺ ion (PCK⁺) complex, \( K_{{{\text{PCK}}^{ + } }} = { 3}. 2 6\times 10^{ 2} {\text{dm}}^{ 3} \,{\text{mol}}^{ - 1} \), and for cholesterol–K⁺ ion (ChK⁺) complex, \( K_{{{\text{ChK}}^{ + } }} = { 1}.00 \times 10^{ 3} {\text{dm}}^{ 3} \,{\text{mol}}^{ - 1} \), were calculated by inserting the experimental data. The value of area occupied by one PCK⁺ complex is 60 Å² molecule^?1, while the area occupied by one ChK⁺ complex is 40.9 Å² molecule^?1. The complex formation energy (Gibbs free energy) values for the PCK⁺ and ChK⁺ complexes are ?14.18 ± 0.71 and ?16.92 ± 0.85 kJ mol^?1, respectively.     

(H)NCAHA and (H)CANNH experiments for the determination of vicinal coupling constants related to the ϕ-torsion angle

Summary A set of three-dimensional triple-resonance experiments is described which provide , , and coupling constants. The pulse sequences generate E.COSY-like multiplet patterns and comprise a magnetization transfer from the amide proton to the α-proton or vice versa via the directly bound heteronuclei. For residues with the ¹H^α spin resonating close to the H₂O signal, a modified HNCA experiment can be employed to measure the vicinal ¹H^N,¹H^α couplings. Ambiguities associated with the conversion of values into ϕ-angle constraints for protein structure determination can be resolved with the knowledge of the heteronuclear ³J-couplings. In favourable cases, stereospecific assignments of glycine α-protons can be obtained by employing the experiments described here in combination with NOE data. The methods are applied to flavodoxin from Desulfovibrio vulgaris.