A theoretical study on the hydrogen-bonding interactions between flavonoids and ethanol/water

Ethanol and water are the solvents most commonly used to extract flavonoids from propolis. Do hydrogen-bonding interactions exist between flavonoids and ethanol/water? In this work, this question was addressed by using density functional theory (DFT) to provide information on the hydrogen-bonding interactions between flavonoids and ethanol/water. Chrysin and Galangin were chosen as the representative flavonoids. The investigated complexes included chrysin–H₂O, chrysin–CH₃CH₂OH, galangin–H₂O and galangin–CH₃CH₂OH dyads. Molecular geometries, hydrogen-bond binding energies, charges of monomers and dyads, and topological analysis were studied at the B3LYP/M062X level of theory with the 6?31++G(d,p) basis set. The main conclusions were: (1) nine and ten optimized hydrogen-bond geometries were obtained for chrysin–H₂O/CH₃CH₂OH and galangin–H₂O/CH₃CH₂OH complexes, respectively. (2) The hydrogen atoms except aromatic H1 and H5 and all of the oxygen atoms can form hydrogen-bonds with H₂O and CH₃CH₂OH. Ethanol and water form strong hydrogen-bonds with the hydroxyl, carbonyl and ether groups in chrysin/galangin and form weak hydrogen-bonds with aromatic hydrogen atoms. Except in structures labeled A and B, chrysin and galangin interact more strongly with H₂O than CH₃CH₂OH. (3) When chrysin and galangin form hydrogen-bonds with H₂O and CH₃CH₂OH, charge transfers from the hydrogen-bond acceptor (H₂O and CH₃CH₂OH in structures A, B, G, H, I, J) to the hydrogen-bond donor (chrysin and galangin in structure A, B, G, H, I, J). The stronger hydrogen-bond makes the hydrogen-bond donor lose more charge (A> B> G> H> I> J). (4) Most of the hydrogen-bonds in chrysin/galangin?H₂O/CH₃CH₂OH complexes may be considered as electrostatic dominant, while C?O2···H in structures labeled E and C?O5···H in structures labeled J are hydrogen-bonds combined of electrostatic and covalent characters. H9, H7, and O4 are the preferred hydrogen-bonding sites.     

Reactions of methylcobalamin with tin and lead compounds

Reactions of CH₃[Co] with (CH₃)_nM^(4?n)+ (n = 2, 3; M = Sn, Pb) at concentrations high enough to detect (CH₃)₄M in the head space (yields 7.08×10^?5?2.06×10^?5%), indicate that dismutation is the major route of production. Similarly, kinetic reactions at lower concentrations show that no demethylation of CH₃[Co] by (CH₃)₃M⁺ (M = Sn, Pb) occurs after 60 days. From the methylation of SnCl₂ by CH₃[Co] at pD 1.0 and under aerobic conditions, the following hydrolysis species were observed in the 400 MHz ¹H NMR spectrum: CH₃- Sn(OH)Cl₂·2H₂O (63.6%), [CH₃Sn(OH)(H₂O)₄]²⁺ (17.6%) and CH₃Sn(OH)₂Cl·nH₂O (18.8%). No methylation products were observed from similar reactions with Pb(II) salts.     

Solubility and reactivity of caseins and β-lactoglobulin in protic solvents

The study of the solubility of unstructured proteins (α_S1-, β-, and κ-casein) and well-structured globulin (β-lactoglobulin) in low water binary solvent systems demonstrated the crucial importance of solvent polarity and neutralization of protein polar functions on the final outcome of solubility experiments. The solubilities up to 38, 56, and 96% in CHCl₃/CH₃OH (1/1, v/v) acidified with HCl and up to 5, 10, and 25% in CHCl₃/CH₃OH (1/1, v/v) in the presence of triethylamine (TEA) were obtained for κ-, α_S1-, and β-casein, respectively. The importance of protein charge neutralization was apparent when the solubilization was performed in basified CHCl₃/CH₃OH media, giving the optimal results when the studied proteins were brought before to their isoionic point. The maximum solubility of β-casein at its pI in 30–70% methanol in CHCl₃ was reaching 50–60% with triethylamine (TEA) added. β-lactoglobulin could be solubilized up to 70% in CHCl₃/CH₃OH (7/3, v/v) acidified with HCl and up to 40% in CHCl₃/CH₃OH (3/7, v/v) in the presence of TEA. The observed yield of reductive alkylation of β-lactoglobulin was much higher (98%) when performed in studied solvent system than in aqueous conditions (75%). Apparently, steric hindrance of the well-folded β-barrel (in aqueous conditions) structure masks the portion of ε-NH₂ groups. In the case of unstructured aqueous media β-casein, 90% alkylation yields were obained in organic and aqueous conditions.     

A DFT study of the effect of K and SiO2 on syngas conversion to methane and methanol over an Mo6P3 cluster

Synthesis gas (CO+H₂) conversion to CH₄ and CH₃OH over an Mo₆P₃ cluster, an Mo₆P₃–Si₃O₉ and a K–Mo₆P₃–Si₃O₉ cluster has been studied using density functional theory (DFT). The study focused on the reaction between the intermediate species CH₂OH_ad+H_ad, comparing methanol formation to C–O bond scission that yields CH_2.ad+H₂O_ad species. The activation energies of both the reactions decreased on the Mo₆P₃–Si₃O₉ and the K–Mo₆P₃–Si₃O₉ clusters compared to the Mo₆P₃ cluster. However, on the K–Mo₆P₃–Si₃O₉ cluster, the activation energy for methanol formation (12.1 kcal/mol) was higher than the C–O bond-breaking activation energy (9.9 kcal/mol). Although the DFT study predicted preferential formation of CH₄ versus CH₃OH on all the Mo₆P₃ clusters, the study also predicted an increased formation of CH₃OH with the addition of K and experimental measurements are in agreement with this prediction.     

Investigation of the antioxidant properties of hyperjovinol A through its Cu(II) coordination ability

Hyperjovinol A (2-methyl-1-(2,4,6-trihydroxy-3-(3-hydroxy-3,7-dimethyloct-6-enyl)phen yl)propan-1-one) is an acylated phloroglucinol isolated from Hypericum Jovis and exhibiting antioxidant properties comparable with those of the most common antioxidant drugs. The study models the compound’s antioxidant ability through its ability to coordinate a Cu²⁺ ion and reduce it to Cu⁺. Complexes with a Cu²⁺ ion were calculated for all the low energy and for representative high energy conformers of hyperjovinol A, placing the ion in turn near each of the electron-rich binding sites. The most stable complexes are those in which Cu²⁺ binds simultaneously to the O of the OH in the geranyl-type chain (R′) and the C═C double bond at the end of R′, or to the O of a phenol OH and the O of the OH in R′. The most stable complexes in which Cu²⁺ binds only to one site are those in which it binds to the C═C double bond at the end of R′ or to the sp² O of the COCH(CH₃)₂ acyl group. Cu²⁺ is reduced to Cu⁺ in all complexes. Comparisons with corresponding complexes of other molecular structures in which one or more of the structural features of hyperjovinol A are modified attempt to elucidate the role, for the antioxidant ability, of relevant features of hyperjovinol A, like the presence and position of the OH or the C═C double bond in R′. Calculations at the DFT/B3LYP/6–31+G(d,p) level were performed for all the structures considered. Calculations utilizing the LANL2DZ pseudopotential for the Cu²⁺ ion were also performed for hyperjovinol A.

A theoretical study on the coordination behavior of some phosphoryl,carbonyl and sulfoxide derivatives in lanthanide complexation

The selectivity of phosphoryl P(O)R₃, sulfoxide S(O)R₂, and carbonyl C(O)R₂ (R?=?NH₂, CH₃, OH, and F) derivatives with lanthanide cations (La³⁺, Eu³⁺, Lu³⁺) was studied by density functional theory calculations. Theoretical approaches were also used to investigate energy and the nature of metal–ligand interaction in the model complexes. Atoms in molecules and natural bond orbital (NBO) analyses were accomplished to understand the electronic structure of ligands, L, and the related complexes, L–Ln³⁺. NBO analysis demonstrated that the negative charge on phosphoryl, carbonyl, and sulfoxide oxygen (O_P, O_C, and O_S) has maximum and minimum values when the connected –R groups are –NH₂ and –F. The metal–ligand distance declines as, –F?>?–OH?>?–CH₃?>?–NH₂. Charge density at the bond critical point and on the lanthanide cation in the L–Ln³⁺ complexes varies in the order –F?<?–OH?<?–CH₃?<?–NH₂, due to greater ligand to metal charge transfer, which is well explained by energy decomposition analysis. It was also illustrated that E⁽²⁾ values of Lp(N)?→?σ*(Y–N) vary in the order P=O ? S=O ? C=O and the related values of Lp(N)?→?σ*(Y=O) change as C=O ? S=O ? P=O in (NH₂)_nYO ligands (Y?=?P, C, and S). Trends in the L–Ln³⁺ CP–corrected bond energies are in good accordance with the optimized O_Y?Ln distances. It seems that, comparing the three types of ligands studied, NH₂–substituted are the better coordination ligands.

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Graphical Abstract Density functional theory (B3LYP) calculations were used to compare structural, electronic and energy aspects of lanthanide (La, Eu, Lu) complexes of phosphine derivatives with those of carbonyls and sulfoxides in which the R– groups connected to the P=O, C=O and S=O are –NH₂, –CH₃, –OH and –F.

     

New synthetic route of polyoxometalate-based hybrids in choline chloride/urea eutectic media

The deep eutectic solvents synthetic method was initially explored as a facile synthesis route to prepare new polyoxometalate (POM)-based hybrids. Such a method can not only avoid poor solubility, lower yields and the potential explosion, but also act as a new type of noxious, convenient and environmental friendly organic reagents. Using the choline chloride/urea eutectic mixture as the deep eutectic solvents, two new compounds, [(CH₃)₃N(CH₂)₂OH]₄[β-Mo₈O₂₆] (1) and {(N₂H₅CO)[(CH₃)₃N(CH₂)₂OH]₂}[CrMo₆O₂₄H₆]·4H₂O (2), were successfully obtained at room temperature. Both compounds were fully characterized by elemental analyses, IR, UV-Vis, TG analyses, cyclic voltammetry and single-crystal X-ray diffraction. The crystal structures of both compounds exhibit 3-D supramolecular assembly based on the extensive hydrogen bonding interactions between organic cations and polyoxoanions. Compounds 1 and 2 represent the first POM-based hybrids prepared by the deep eutectic solvents synthetic method.     

Conformational evaluation of labeled C3′‐O‐P‐13CH2‐O‐C4″ phosphonate internucleotide linkage,a phosphodiester isostere

Modified internucleotide linkage featuring the C3′‐O‐P‐CH₂‐O‐C4″ phosphonate grouping as an isosteric alternative to the phosphodiester C3′‐O‐P‐O‐CH₂‐C4″ bond was studied in order to learn more on its stereochemical arrangement, which we showed earlier to be of prime importance for the properties of the respective oligonucleotide analogues. Two approaches were pursued: First, the attempt to prepare the model dinucleoside phosphonate with ¹³C‐labeled CH₂ group present in the modified internucleotide linkage that would allow for a more detailed evaluation of the linkage conformation by NMR spectroscopy. Second, the use of ab initio calculations along with molecular dynamics (MD) simulations in order to observe the most populated conformations and specify main structural elements governing the conformational preferences. To deal with the former aim, a novel synthesis of key labeled reagent (CH₃O)₂P(O)¹³CH₂OH for dimer preparation had to be elaborated using aqueous ¹³C‐formaldehyde. The results from both approaches were compared and found consistent. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 514–529, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Benefits and trade‐offs of replacing synthetic fertilizers by animal manures in crop production in China: A meta‐analysis

Recycling of livestock manure to agricultural land may reduce the use of synthetic fertilizer and thereby enhance the sustainability of food production. However, the effects of substitution of fertilizer by manure on crop yield, nitrogen use efficiency (NUE), and emissions of ammonia (NH₃), nitrous oxide (N₂O) and methane (CH₄) as function of soil and manure properties, experimental duration and application strategies have not been quantified systematically and convincingly yet. Here, we present a meta‐analysis of these effects using results of 143 published studies in China. Results indicate that the partial substitution of synthetic fertilizers by manure significantly increased the yield by 6.6% and 3.3% for upland crop and paddy rice, respectively, but full substitution significantly decreased yields (by 9.6% and 4.1%). The response of crop yields to manure substitution varied with soil pH and experimental durations, with relatively large positive responses in acidic soils and long‐term experiments. NUE increased significantly at a moderate ratio (<40%) of substitution. NH₃ emissions were significantly lower with full substitution (62%–77%), but not with partial substitution. Emissions of CH₄ from paddy rice significantly increased with substitution ratio (SR), and varied by application rates and manure types, but N₂O emissions decreased. The SR did not significantly influence N₂O emissions from upland soils, and a relative scarcity of data on certain manure characteristic was found to hamper identification of the mechanisms. We derived overall mean N₂O emission factors (EF) of 0.56% and 0.17%, as well as NH₃ EFs of 11.1% and 6.5% for the manure N applied to upland and paddy soils, respectively. Our study shows that partial substitution of fertilizer by manure can increase crop yields, and decrease emissions of NH₃ and N₂O, but depending on site‐specific conditions. Manure addition to paddy rice soils is recommended only if abatement strategies for CH₄ emissions are also implemented.     

Synthesis and characterization of a series of N3O-ligated mononuclear Mn(II) halide complexes

Treatment of a N₃O-donor chelate ligand (mpppa = N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine; bpppa = N-benzyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylmethyl)amine) with equimolar amounts of Mn(ClO₄)₂ · 6H₂O and Me₄NX (X = Cl, Br, I) in methanol resulted in the production of a series of mononuclear Mn(II) halide complexes of the formula [(L)Mn-X(CH₃OH)]ClO₄ (L = mpppa or bpppa). X-ray crystallographic studies of [(mpppa)Mn-Cl(CH₃OH)]ClO₄ · CH₃OH (2 · CH₃OH), [(mpppa)Mn-Br(CH₃OH)]ClO₄ · CH₃OH (4 · CH₃OH), [(mpppa)Mn-I(CH₃OH)]ClO₄ · CH₃OH (6 · CH₃OH), and [(bpppa)Mn-I(CH₃OH)]ClO₄ · O₂(CH₂CH₃)₂ (7 · O(CH₂CH₃)₂) revealed for each a mononuclear Mn(II) center having tetradentate coordination of the chelate ligand, one coordinated halide anion, and one molecule of coordinated methanol. An increase in the Mn-X distance through the halide series (Cl, Br, I) correlates linearly with the increase in the radius of the anion. The magnetic moment of each halide complex, measured via Evans method in methanol, is consistent with the presence of a high-spin distorted octahedral Mn(II) center. The EPR features of the halide complexes in methanol do not change as a function of the nature of the halide coordinated to the Mn(II) center.     

Highly efficient photoactivation of Mn-depleted photosystem II by imidazole-liganded manganese complexes

The oxygen-evolving complex (OEC) of Mn-depleted photosystem II (PSII) can be reconstituted in the presence of exogenous Mn or a Mn complex under weak illumination, a process called photoactivation. Synthetic Mn complexes could provide a powerful system to analyze the assembly of the OEC. In this work, four mononuclear Mn complexes, [(terpy)₂Mn^II(OOCH₃)]·2H₂O (where terpy is 2,2′:6′,2″-terpyridine), Mn^II(bzimpy)₂, Mn^II(bp)₂(CH₃CH₂OH)₂ [where bzimpy is 2,6-bis(2-benzimidazol-2-yl)pyridine] and [Mn^III(HL)(L)(py)(CH₃OH)]CH₃OH (where py is pyridine) were used in photoactivation experiments. Measurements of the photoreduction of 2,6-dichorophenolindophenol and oxygen evolution demonstrate that photoactivation is more efficient when Mn complexes are used instead of MnCl₂ in reconstructed PSII preparations. The most efficient recoveries of oxygen evolution and electron transport activities are obtained from a complex, [Mn^III(HL)(L)(py)(CH₃OH)]CH₃OH, that contains both imidazole and phenol groups. Its recovery of the rate of oxygen evolution is as high as 79% even in the absence of the 33-kDa peptide. The imidazole ligands of the Mn complex probably accelerate P ₆₈₀ ^•+ reduction and consequently facilitate the process of photoactivation. Also, the strong intermolecular hydrogen bond probably facilitates interaction with the Mn-depleted PSII via reorganization of the hydrogen-bonding network, and therefore promotes the recovery of oxygen evolution and electron transport activities.     

Unprecedented rhodium-mediated catalytic transfer hydrogenation of a phosphonate functionalized olefin in ecofriendly media

RhCl₃ · xH₂O catalyst-mediated hydrogenation reactions of vinyl phosphonic diethyl ester H₂CCH-P(O)(OEt)₂ (1) have been investigated. Results demonstrate that the hydrogenation of H₂CCH-P(O)(OEt)₂ (1) to CH₃CH₂-P(O)(OEt)(OH) (2) proceeds in the presence of RhCl₃ · xH₂O catalyst, without any external hydrogen source and ancillary ligands, to near qualitative yields in ethanol and water media. ³¹P, ¹³C and ¹H NMR and deuterium-labeling experiments provide evidence for the non-concerted mechanistic pathway associated with the hydrogenation of 1 to 2.     

1,1′-Bis(3-hydroxypropyl)ferrocene: Preparation and substitution with polyfluoroalkyl groups

SiMe₃CH₂CH₂ was demonstrated as a robust and convenient OH protecting group in the preparation of 1,1′-bis(3-hydroxypropyl)ferrocene (1). The OH groups were used to introduce polyfluorinated alkyl chains by acylation of 1 with (C₂F₅CO)₂O and alkylation with CF₃(CF₂)₆CH₂OH under Mitsunobu reaction conditions. This demonstrates a new method for introduction of an ω-hydroxyalkyl group to the Cp unit as a synthetic handle for modification of molecular properties.     

Coordinated 2-halo-1,3,2-dioxaphosphorinane ligands. II. Syntheses and 13C, 31P and 95Mo NMR and IR spectroscopic characterization of some Cr and Mo pentacarbonyl complexes of 2-substituted-4-methyl-1,3,2-dioxaphosphorinanes

A study of the reactions of M(CO)₅(P(OCH₂CH₂CH(Me)O)Cl) (M=Cr, Mo) with a variety of nucleophiles of the type HER (E=NH, O, S; R=H, alkyl, aryl) is reported. The ¹³C, ³¹P and ⁹⁵Mo NMR and IR spectral data for the M(CO)₅(P(OCH₂CH₂CH(Me)O)ER) complexes is presented and compared to that previously reported for some Mo(CO)₅(P(OCH₂CMe₂CH₂O)ER) complexes. This comparison provides insight into the manner in which variations in the metal and in the substitution on the 1,3,2-dioxaphosphorinane ring affect the electron density distribution within these complexes.The results from a study of the rates of chloride substitution by n-propylamine in the M(CO)_s(P(OCH₂CH₂CH(Me)O)Cl) complexes are also presented. These rates are compared with those previously reported for chloride substitution by n-propylamine in the Mo(CO)₅(P(OCH₂CMe₂CH₂O)Cl) and Mo(CO)₅(Ph₂PCl) complexes. These comparisons, in conjunction with the NMR and IR studies, suggest that both the position of the Me groups on the phosphorinane ring and the amount of electron density on the P have significant effects upon the rate of chloride substitution in these complexes.     

Tandem crystallization strategies for resolution of 3,3,3‐trifluorolactic acid [CF3CH(OH)COOH] by chiral benzylamines

Resolution of rac‐3,3,3‐trifluorolactic acid by diastereomeric salt formation was reinvestigated. The use of (S)‐1‐phenylethylamine gives coprecipitation of two diastereomeric phases, 1 (S)‐[NH₃CH(CH₃)Ph](S)‐[CF₃CH(OH)COO] and 2 (S)‐[NH₃CH(CH₃)Ph](R)‐[CF₃CH(OH)COO]·H₂O. Pure phase 1 may be obtained using molecular sieves as desiccants. Resolution by (S,S)‐2‐amino‐1‐phenylpropan‐1,3‐diol gives monoclinic (S,S)‐[NH₃CH(CH₂OH)CHOHPh] (R)‐[CF₃CH(OH)‐COO] 3 with minor (S)‐3,3,3‐trifluorolactate contamination, which is precluded in the recrystallized orthorhombic form 4 . A new resolution using inexpensive phenylglycinol gives pure phase 5 (S)‐[NH₃CH(CH₂OH)Ph] (S)‐[CF₃CH(OH)COO] in 76% yield, 94% ee in a single step, in preference to its (S)‐(R) diastereomer 6 . Overall efficient resolution for both enantiomers of the trifluorolactic acid (each ca. 70% yield, 99% ee) may be achieved by various two‐step “tandem” crystallizations, involving direct addition of either water or a second base to the filtrate from the initial reaction.     

Coordination modes of polydentate ligands. 4. The crystal and molecular structure of an oxo-bridged iron(III) complex containing a pentadentate imino-alkoxy ligand

In the presence of Fe³⁺, template condensation of the fluorinated keto-alcohol CH₃C(O)CH₂C- (CF₃)₂OH with the triamine CH₃C(CH₂NH₂)₃ leads to two products: a fully condensed, imino-alkoxy, iron(III) complex, Fe{CH₃C[CH₂NC(CH₃)CH₂C(CF₃)₂O]₃}, and a partially condensed iron(III) complex, O{FeCH₃C[CH₂NC(CH₃)CH₂C(CF₃)₂O]₂(CH₂NH₂)}₂, in which two six-coordinate iron(III) centers are linked by an oxide ion. A complete crystal and molecular structure determination of the latter has been made.Crystals are monoclinic, space group C2/c, a= 13.886(4); b=23.206(5); c=15.241(4) Å; β= 106.55(2)°; V=4708 ų; Z=4. Least-squares refinement on F of 322 variables using 2627 observations converged at a conventional agreement factor of 3.8%. The Fe to bridging oxide distance is 1.811(1) Å, the FeFe distance 3.468 Å, and the FeOFe angle 146.6(2)°. A comparison is made between this structure and those of natural hemerythrin systems.     

Structure characterization of a methylated ester biosurfactant produced by a newly isolated <Emphasis Type="Italic">Dietzia cinnamea</Emphasis> KA1

Biosurfactans are amphiphilic compounds synthesized by a wide group of microorganisms and tend to interact with surfaces of different polarities. In the present study we purified and characterized a biosurfactant produced by Dietzia cinnamea KA-1 when cultured by n-hexadecane as sole carbon source. The crude biosurfactant was extracted with ethyl acetate and purified by freezing at–20°C and then silica Gel column chromatography. The purified biosurfactant applied for more characterization using Elemental analysis (CHNS), Fourier Transform Infrared Spectroscopy (FTIR), Mass Spectroscopy (MS) and Nuclear Magnetic Resonance (¹H and ¹³C-NMR) analysis. CHNS analysis showed the presence of C (74.92%) and H (11.63%) but not N or S. Functional groups of OH, CH₂, CH₃, C=O and aliphatic C?O revealed by FTIR analysis. The presence and position of these groups were confirmed by NMR analysis, and molecular mass of biosurfactant calculated using MS analysis. Finally, the product characterized as a methylated ester compound with molecular formula of C₂₁H₄₂O₄. This is the first report of biosurfactant of species D. cinnamea identified as ester, furthermore the ester was found to be in the methylated form.     

Reducing greenhouse gas emissions,water use,and grain arsenic levels in rice systems

Agriculture is faced with the challenge of providing healthy food for a growing population at minimal environmental cost. Rice (Oryza sativa), the staple crop for the largest number of people on earth, is grown under flooded soil conditions and uses more water and has higher greenhouse gas (GHG) emissions than most crops. The objective of this study was to test the hypothesis that alternate wetting and drying (AWD – flooding the soil and then allowing to dry down before being reflooded) water management practices will maintain grain yields and concurrently reduce water use, greenhouse gas emissions and arsenic (As) levels in rice. Various treatments ranging in frequency and duration of AWD practices were evaluated at three locations over 2 years. Relative to the flooded control treatment and depending on the AWD treatment, yields were reduced by <1–13%; water‐use efficiency was improved by 18–63%, global warming potential (GWP of CH₄ and N₂O emissions) reduced by 45–90%, and grain As concentrations reduced by up to 64%. In general, as the severity of AWD increased by allowing the soil to dry out more between flood events, yields declined while the other benefits increased. The reduction in GWP was mostly attributed to a reduction in CH₄ emissions as changes in N₂O emissions were minimal among treatments. When AWD was practiced early in the growing season followed by flooding for remainder of season, similar yields as the flooded control were obtained but reduced water use (18%), GWP (45%) and yield‐scaled GWP (45%); although grain As concentrations were similar or higher. This highlights that multiple environmental benefits can be realized without sacrificing yield but there may be trade‐offs to consider. Importantly, adoption of these practices will require that they are economically attractive and can be adapted to field scales.     

Fourier-transform infrared spectroscopy of Pediastrum duplex: characterization of a micro-population isolated from a eutrophic lake

Fourier-transform infrared (FTIR) spectroscopy was carried out on single colonies of Pediastrum duplex present in air-dried preparations of mixed phytoplankton samples isolated from a eutrophic freshwater lake. FTIR absorption spectra had 12 distinct bands over the wavenumber range 3300–900?cm^?1 which were tentatively assigned to a range of chemical groups, including –OH (residual water, wavenumber 3299?cm^?1), –CH2 (lipid, 2924), –C=O (cellulose, 1739), amide (protein, 1650 and 1542), >P=O (nucleic acid, 1077) and –C–O (starch, 1151 and 1077). Measurement of band areas identified residual water, protein and starch as the major detectable constituents. Areas of single bands and combined bands of –CH₂, –C–O and >P=O species normalized to protein (to correct for differences in specimen hydration and thickness) showed wide variation between colonies, indicating environmental heterogeneity. Correlation analysis demonstrated close statistical associations between different molecular species. Particularly high levels of correlation between bands 3/4 (CH₂), 6/7 (amide) and 8/9 (–CH₃) was consistent with their joint origin from the same molecular species. The isolation of bands 11 and 12 in the correlation pattern was confirmed by factor analysis, suggesting that variation in the level of starch is statistically unrelated to other macromolecules being monitored. The use of FTIR spectroscopy to characterize an algal micro-population within mixed phytoplankton has potential for future studies on biodiversity and environmental interactions at the species level.     

Soil-atmosphere exchange of nitrous oxide and methane in New Zealand terrestrial ecosystems and their mitigation options: a review

The two non-CO₂ greenhouse gases (GHGs) nitrous oxide (N₂O) and methane (CH₄) comprise 54.8% of total New Zealand emissions. Nitrous oxide is mainly generated from mineral N originating from animal dung and urine, applied fertiliser N, biologically fixed N₂, and mineralisation of soil organic N. Even though about 96% of the anthropogenic CH₄ emitted in New Zealand is from ruminant animals (methanogenesis), methane uptake by aerobic soils (methanotrophy) can significantly contribute to the removal of CH₄ from the atmpsphere, as the global estimates confirm. Both the net uptake of CH₄ by soils and N₂O emissions from soils are strongly influenced by changes in land use and land management. Quantitative information on the fluxes of these two non-CO₂ GHGs is required for a range of land-use and land-management ecosystems to determine their contribution to the national emissions inventory, and for assessing the potential of mitigation options. Here we report soil N₂O fluxes and CH₄ uptake for a range of land-use and land-management systems collated from published and unpublished New Zealand studies. Nitrous oxide emissions are highest in dairy-grazed pastures (10–12 kg N₂O–N ha^?1 year^{? 1}), intermediate in sheep-grazed pastures, (4–6 kg N₂O–N ha^?1 year^?1), and lowest in forest, shrubland and ungrazed pasture soils (1–2 kg N₂O–N ha^?1 year^?1). N deposited in the form of animal urine and dung, and N applied as fertiliser, are the principal sources of N₂O production. Generally, N₂O emissions from grazed pasture soils are high when the soil water-filled pore-space is above field capacity, and net CH₄ uptake is low or absent. Although nitrification inhibitors have shown some promise in reducing N₂O emissions from grazed pasture systems, their efficacy as an integral part of farm management has yet to be tested. Methane uptake was highest for a New Zealand Beech forest soil (10–11 kg CH₄ ha^?1 year^?1), intermediate in some pine forest soils (4–6 kg CH₄ ha^?1 year^?1), and lowest in most pasture (<1 kg CH₄ ha^?1 year^?1) and cropped soils (1.5 kg CH₄ ha^?1 year^?1). Afforestation /reforestation of pastures results in increases in soil CH₄ uptake, largely as a result of increases in soil aeration status and changes in the population and activities of methanotrophs. Soil CH₄ uptake is also seasonally dependent, being about two to three times higher in a dry summer and autumn than in a wet winter. There are no practical ways yet available to reduce CH₄ emissions from agricultural systems. The mitigation options to reduce gaseous emissions are discussed and future research needs identified.