Plutonium(IV) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS15 and Shewanella oneidensis MR1

The bacterial reduction of actinides has been suggested as a possible remedial strategy for actinide-contaminated environments, and the bacterial reduction of Pu(VI/V) has the potential to produce highly insoluble Pu(IV) solid phases. However, the behavior of plutonium with regard to bacterial reduction is more complex than for other actinides because it is possible for Pu(IV) to be further reduced to Pu(III), which is relatively more soluble than Pu(IV). This work investigates the ability of the metal-reducing bacteria Geobacter metallireducens GS15 and Shewanella oneidensis MR1 to enzymatically reduce freshly precipitated amorphous Pu(IV) (OH)₄ [Pu(IV)(OH)_4(am)] and soluble Pu(IV)(EDTA). In cell suspensions without added complexing ligands, minor Pu(III) production was observed in cultures containing S. oneidensis, but little or no Pu(III) production was observed in cultures containing G. metallireducens. In the presence of EDTA, most of the Pu(IV)(OH)_4(am) present was reduced to Pu(III) and remained soluble in cell suspensions of both S. oneidensis and G. metallireducens. When soluble Pu(IV)(EDTA) was provided as the terminal electron acceptor, cell suspensions of both S. oneidensis and G. metallireducens rapidly reduced Pu(IV)(EDTA) to Pu(III)(EDTA) with nearly complete reduction within 20 to 40 min, depending on the initial concentration. Neither bacterium was able to use Pu(IV) (in any of the forms used) as a terminal electron acceptor to support growth. These results have significant implications for the potential remediation of plutonium and suggest that strongly reducing environments where complexing ligands are present may produce soluble forms of reduced Pu species.     

243,244Cm studies in C57BL/Do mice

Three groups of C57BL/Do mice were injected with different activities of 243,244Cm so that the long-term biological effects could be evaluated. The biological retention, R, of injected curium in the skeleton at t days after injection could be represented by the equations R = 0.245e-0.000379t and R = 0.208e-0.000494t for male and female mice, respectively. Effective skeletal retention equations were used to calculate the cumulative mean skeletal dose in rad at 140 days before death in each group of mice. The primary objective of this study was to determine the relative biological effectiveness (RBE) of 243,244Cm compared to 226Ra, using bone sarcoma induction as the end point. Combined data (bone sarcomas per 10(6) mouse-rad) for male and female mice permitted the RBE value +/- SD for 243,244Cm to be calculated as 4.4 +/- 1.8 compared to 1.0 for 226Ra. A comparison of RBE values form a previous study in this mouse strain and the value for 243,244Cm from this study suggests that the trivalent actinides 241Am, 243,244Cm, and 249Cf are about three times less effective for bone sarcoma induction than 239Pu.     

The Impact of Model Peptides on Structural and Dynamic Properties of Egg Yolk Lecithin Liposomes – Experimental and DFT Studies

Electron spin resonance (ESR), ¹H‐NMR, voltage and resistance experiments were performed to explore structural and dynamic changes of Egg Yolk Lecithin (EYL) bilayer upon addition of model peptides. Two of them are phenylalanine (Phe) derivatives, Ac‐Phe‐NHMe ( 1 ) and Ac‐Phe‐NMe₂ ( 2 ), and the third one, Ac‐(Z)‐ΔPhe‐NMe₂ ( 3 ), is a derivative of (Z)‐α,β‐dehydrophenylalanine. The ESR results revealed that all compounds reduced the fluidity of liposome's membrane, and the highest activity was observed for compound 2 with N‐methylated C‐terminal amide bond (Ac‐Phe‐NMe₂). This compound, being the most hydrophobic, penetrates easily through biological membranes. This was also observed in voltage and resistance studies. ¹H‐NMR studies provided a sound evidence on H‐bond interactions between the studied diamides and lecithin polar head. The most significant changes in H‐atom chemical shifts and spin‐lattice relaxation times T₁ were observed for compound 1 . Our experimental studies were supported by theoretical calculations. Complexes EYL? Ac‐Phe‐NMe₂ and EYL? Ac‐(Z)‐ΔPhe‐NMe₂, stabilized by NH???O or/and CH???O H‐bonds were created and optimized at M06‐2X/6‐31G(d) level of theory in vacuo and in H₂O environment. According to our molecular‐modeling studies, the most probable lecithin site of H‐bond interaction with studied diamides is the negatively charged O‐atom in phosphate group which acts as H‐atom acceptor. Moreover, the highest binding energy to hydrocarbon chains were observed in the case of Ac‐Phe‐NMe₂ ( 2 ).     

Biosorption of radionuclides by Rhizopus arrhizus

The sorption of various radionuclides viz. 233U, 239Pu, 241Am, 144Ce, 147Pm, 152+154Eu and 95Zr from aqueous nitrate medium has been studied using biomass Rhizopus arrhizus. The biosorption of 233U and 239Pu was found to be maximum at pH 6-7 whereas for other trivalent actinides and fission products viz. 241Am, 144Ce, 147Pm, 152+154Eu and tetravalent 95Zr, it was more effective at pH 2. This biomass is a promising sorbant for the treatment of radioactive effluents from nuclear industry. © Rapid Science Ltd. 1998     

Force constants and fundamental frequencies of the fare earth trihalide molecules

The effective nuclear charge model has been applied to the rare earth trihalides. A set of the effective nuclear charge values of the rare earth atoms has been evaluated from the bond stretch force constants obtained by normal coordinate analysis of the infrared spectra of the lanthanide trifluorides.The force constants and the fundamental frequencies of all the lanthanide trihalides have been calculated by means of the effective nuclear charge model. The calculated results are in agreement with the experimental data. The results show that the most probable configuration of the lanthanide trihalides is pyramidal with C_3ν symmetry, although the geometry of the lanthanide trifluoride molecules is very close to planar. It is also found that the frequency ν₂ (symmetric deformation) and the frequency ν₄ (antisymmetric deformation) will vary with the bond angle (XLnX).     

Actinide and metal toxicity to prospective bioremediation bacteria

Bacteria may be beneficial for alleviating actinide contaminant migration through processes such as bioaccumulation or metal reduction. However, sites with radioactive contamination often contain multiple additional contaminants, including metals and organic chelators. Bacteria-based bioremediation requires that the microorganism functions in the presence of the target contaminant, as well as other contaminants. Here, we evaluate the toxicity of actinides, metals and chelators to two different bacteria proposed for use in radionuclide bioremediation, Deinococcus radiodurans and Pseudomonas putida, and the toxicity of Pu(VI) to Shewanella putrefaciens. Growth of D. radiodurans was inhibited at metal concentrations ranging from 1.8 microM Cd(II) to 32 mM Fe(III). Growth of P. putida was inhibited at metal concentrations ranging from 50 microM Ni(II) to 240 mM Fe(III). Actinides inhibited growth at mM concentrations: chelated Pu(IV), U(VI) and Np(V) inhibit D. radiodurans growth at 5.2, 2.5 and 2.1 mM respectively. Chelated U(VI) inhibits P. putida growth at 1.7 mM, while 3.6 mM chelated Pu(IV) inhibits growth only slightly. Pu(VI) inhibits S. putrefaciens growth at 6 mM. These results indicate that actinide toxicity is primarily chemical (not radiological), and that radiation resistance does not ensure radionuclide tolerance. This study also shows that Pu is less toxic than U and that actinides are less toxic than other types of metals, which suggests that actinide toxicity will not impede bioremediation using naturally occurring bacteria.     

Synthesis of symmetric dithiophosphinic acids for “minor actinide” extraction

New aromatic dithiophosphinic acid (R₂PS₂H; DPAH) derivatives were isolated using a synthetic pathway based on nucleophilic addition at phosphorus, which leads to regiospecific aromatic substituents on phosphorus. The synthesis improves DPAH designs that can provide insight into the differences in binding/chelation between DPAH and trivalent actinides/lanthanides. The synthesis gives good yields via isolation of the DPAH as the ammonium salt. Multinuclear NMR spectroscopy and X-ray structure determination are used for the identification of both the ammonium salt and free acid of the dithiophosphinic derivatives. The DPAH products are stable when exposed to the ambient atmospheric conditions for long periods. For instance, the bis(o-trifluoromethylphenyl) DPAH derivative showed very little degradation when contacted with water and nitric acid for prolonged periods. Furthermore, this derivative selectively extracts a trivalent actinide from a lanthanide with separation factors of ∼100 000 at low pH. Overall, these DPAH derivatives are exciting new compounds for potential application in actinide and lanthanide separations technologies.     

Long-Term Modeling of Plutonium Solubility at a Desert Disposal Site,Including CO2 Diffusion,Cellulose Decay,and Chelation

The solubility of plutonium was estimated for waste buried at the Greater Confinement Disposal site in Nevada. The EQ3/6 thermochemical database was modified to include recent data on Pu complex formation, and the solubilities of two critical phases (probertite (CaNaB₅O₉·5H₂O), added as a backfill material; and Ca sac-charate) were determined by experiment. Reaction path runs were used to model effects of cellulose degradation, including complexation of actinides by organic acids and carbonate, decay of the complexing agents, and the buildup and diffusive loss of CO₂ through the permeable alluvium. For most waste interaction scenarios, long-term (≈10³ years) concentrations of Pu in pore waters are ≤10^?7 molal and are dominated by carbonate complexes, although organic complexes could dominate in the first ≈10³ years. In unusual circumstances, carbonation of buried lithium could produce very high Pu solubilities; however, even in such a system, a slight lowering of the effective redox potential dramatically lowers Pu solubility. A sensitivity analysis suggests that the “base case” calculations are conservative, tending to overestimate long-term solubility, with the system redox and the identity of the organic acids the major sources of uncertainty.     

Plutonium(V/VI) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1

We examined the ability of the metal-reducing bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1 to reduce Pu(VI) and Pu(V). Cell suspensions of both bacteria reduced oxidized Pu [a mixture of Pu(VI) and Pu(V)] to Pu(IV). The rate of plutonium reduction was similar to the rate of U(VI) reduction obtained under similar conditions for each bacteria. The rates of Pu(VI) and U(VI) reduction by cell suspensions of S. oneidensis were slightly higher than the rates observed with G. metallireducens. The reduced form of Pu was characterized as aggregates of nanoparticulates of Pu(IV). Transmission electron microscopy images of the solids obtained from the cultures after the reduction of Pu(VI) and Pu(V) by S. oneidensis show that the Pu precipitates have a crystalline structure. The nanoparticulates of Pu(IV) were precipitated on the surface of or within the cell walls of the bacteria. The production of Pu(III) was not observed, which indicates that Pu(IV) was the stable form of reduced Pu under these experimental conditions. Experiments examining the ability of these bacteria to use Pu(VI) as a terminal electron acceptor for growth were inconclusive. A slight increase in cell density was observed for both G. metallireducens and S. oneidensis when Pu(VI) was provided as the sole electron acceptor; however, Pu(VI) concentrations decreased similarly in both the experimental and control cultures.Effective bioremediation and waste management strategies at nuclear sites require an understanding of the fundamental biogeochemical processes that control the mobility of actinides. Microorganisms can influence the chemical speciation, valence state, and distribution of actinides in subsurface environments (2, 8, 12, 14). Dissimilatory metal-reducing bacteria (DMRB), which derive energy by respiring oxidized metals (Fe and Mn in nature), may play a particularly important role in the mobility of actinides, since the oxidized forms of many radionuclides are more mobile than their reduced forms. Remedial strategies have been proposed to biomineralize radionuclides via direct reduction by DMRB or indirectly by DMRB by-products (9-11). Several DMRB have been shown to conserve energy for anaerobic growth via the reduction of U(VI) (9-11, 14).Plutonium redox chemistry is more complex than that of most other actinides. Under environmental conditions, plutonium can exist in the III, IV, V, and VI oxidation states, and multiple oxidation states can coexist simultaneously (4, 5). The oxidized species of plutonium [Pu(V) and Pu(VI)] generally are much more soluble than the reduced species (4). Predicting the influence DMRB have on plutonium biogeochemistry is complicated by the fact that both Pu(III) and Pu(IV) are possible products of biological reduction. Also, the presence of chelating ligands can greatly influence the oxidation state formed during reduction as well as the reduction rate. The reduction of oxidized Pu species to Pu(IV) is desired, because it is highly insoluble and not very mobile. However, in the presence of complexing ligands and under reducing conditions the production of Pu(III) is favored, and Pu(III) complexes can be quite soluble (2). The conditions leading to the reduction of Pu(V) and Pu(VI) need to be understood and controlled so that they do not lead to the production of Pu(III), if the biological reduction of Pu(V) or Pu(VI) is to be used as an effective remediation strategy.There is little information available concerning the influence DMRB have on plutonium biogeochemistry. Few previous studies have reported the biological reduction of Pu(IV) to Pu(III) (2, 7, 16). During the earlier experiments (16), the solubilization of PuO₂ increased approximately ∼40% in solutions with DMRB. In solutions with DMRB and nitrilotriacetic acid (NTA), approximately 90% of the available Pu was solubilized, but the production of Pu(III) was not observed in any of the cultures, either with or without NTA added (16). The enhanced solubility of Pu was attributed to Pu(IV) reduction, the solubilization of resultant Pu(III), and the reoxidation of Pu(III) to Pu(IV) with the NTA complexation of Pu(III). Since Pu(III) was not observed, the biological reduction of Pu(IV) was inferred from the data (16). The biological reduction of Pu(IV) to Pu(III) was first conclusively documented with the production of Pu(III) in monocultures of G. metallireducens GS-15 and S. oneidensis MR-1 both with and without the addition of a chelating agent (EDTA) (2). In experiments without EDTA, the aqueous concentration of Pu(III) in DMRB cultures was very low (<0.05 mM Pu) (2). The aqueous concentration of Pu(III) increased to approximately 60 to 80% (0.3 to 0.4 mM Pu) of the total Pu(IV) when EDTA was added to the cultures (2). To our knowledge, there are no published studies documenting the biological reduction of Pu(V) or Pu(VI) to either Pu(IV) or Pu(III). However, based on thermodynamics calculations, the reduction of Pu(V) and Pu(VI) by DMRB should be possible and yield greater energy for the bacteria than Pu(IV) reduction (2).The study presented here was designed first to assess the ability of G. metallireducens GS-15 and S. oneidensis MR-1 to reduce Pu(V) and Pu(VI) in monocultures under cell resting and growth conditions. Second, the aqueous and solid phases produced during the experiments were analyzed to determine the extent of biological reduction [i.e., to Pu(IV) or Pu(III)].     

Combined DFT and NBO study on the electronic basis of Si···N-β-donor bond

Two groups of isoelectronic molecules with different SiXN (X=C, N, O ) units are analyzed by a combined DFT and NBO study to investigate the electronic basis of Si···N-β-donor bond. The influence of various energy components on the formation of Si···N-β-donor bond is explored. The importance of the electron delocalization from the lone pair of nitrogen atom into the acceptor-orbitals connected with Si atom is elicited by our calculations. The electron delocalization from the lone pair of nitrogen atom into the antibonding orbital of Si-X bond is quite different among the isoelectronic molecules with various types of SiXN units.     

Interactions of the Mont Terri Opalinus Clay Isolate Sporomusa sp. MT-2.99 with Curium(III) and Europium(III)

Bacterial cell walls have great potential to influence the speciation and mobility of actinides and lanthanides in the environment. In this study we explored the unknown interaction between Cm(III)/Eu(III) and cell-suspensions of Sporomusa sp. MT-2.99, a novel isolate recovered from Opalinus Clay (Mont Terri, Switzerland). The Cm(III)/Eu(III) binding by the cell surface functional groups was studied by potentiometry combined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). This article provides stability constants of Cm(III)/Eu(III) complexed by cell surface functional groups. We could show that as a function of pH Cm(III)/Eu(III) binding occurred to hydrogen phosphoryl, carboxyl and deprotonated phosphoryl sites. Both metals showed a similar interaction process consisting of surface complexation (major) with high thermodynamic stability and an irreversible binding within the cell envelope (minor).     

Conformational preference and cis–trans isomerization of 4‐methylproline residues

Conformational preferences and prolyl cis?trans isomerizations of the (2S,4S)‐4‐methylproline (4S‐MePro) and (2S,4R)‐4‐methylproline (4R‐MePro) residues are explored at the M06‐2X/cc‐pVTZ//M06‐2X/6‐31+G(d) level of theory in the gas phase and in water, where solvation free energies were calculated using the implicit SMD model. In the gas phase, the down‐puckered γ‐turn structure with the trans prolyl peptide bond is most preferred for both Ac‐4S‐MePro‐NHMe and Ac‐4R‐MePro‐NHMe, in which the C₇ hydrogen bond between two terminal groups seems to play a role, as found for Ac‐Pro‐NHMe. Because of the C₇ hydrogen bonds weakened by the favorable direct interactions between the backbone C?O and H? N groups and water molecules, the 4S‐MePro residue has a strong preference of the up‐puckered polyproline II (PP_II) structure over the down‐puckered PP_II structure in water, whereas the latter somewhat prevails over the former for the 4R‐MePro residue. However, these two structures are nearly equally populated for Ac‐Pro‐NHMe. The calculated populations for the backbone structures of Ac‐4S‐MePro‐NHMe and Ac‐4R‐MePro‐NHMe in water are reasonably consistent with CD and NMR experiments. In particular, our calculated results on the puckering preference of the 4S‐MePro and 4R‐MePro residues with the PP_II structures are in accord with the observed results for the stability of the (X‐Y‐Gly)₇ triple helix with X = 4R‐MePro or Pro and Y = 4S‐MePro or Pro. The calculated rotational barriers indicate that the cis?trans isomerization may in common proceed through the anticlockwise rotation for Ac‐4S‐MePro‐NHMe, Ac‐4R‐MePro‐NHMe, and Ac‐Pro‐NHMe in water. The lowest rotational barriers become higher by 0.24?1.43 kcal/mol for Ac‐4S‐MePro‐NHMe and Ac‐4R‐MePro‐NHMe than those for Ac‐Pro‐NHMe in water. © 2010 Wiley Periodicals, Inc. Biopolymers 95: 51–61, 2011.     

Theoretical characterization of SOME amides and esters DERIVATIVES of valproic acid

The equilibrium structures, the planarity of the C(=O)X linkage and the nature of the chemical bond in the Y−C(=O)−XR₁R₂ [where: Y= −CH−(CH₂−CH₂−CH₃)₂, X=N,O and R₁, R₂= H; alkyl and aryl groups and lone pair electrons (lp)] molecular fragment of derivates of Valproic acid (Vpa) with antiepileptic activity were studied systematically by means of B3LYP calculations and topological analysis of the electron localization function (ELF). The covariance parameter cov[Ω_i, Ω_j] reveals a dominating delocalization effect between the lone pair V(O₁), V(X) and the electron density of the H−C and H−X₁ bonds resulting from the existence of not only non-conventional intramolecular hydrogen bonding patterns as C−H...O/N but also a weak closed-shell stabilizing interaction type arising from a dihydrogen bonding as C−H...H−N, where H...H contacts at a significantly shorter distance than twice the hydrogen atom van der Waals radius. The analyzed data derived from ELF domains were found to be in agreement with the known features and properties of the hydrogen bonding interactions discussed in this work.     

αvβ3-Integrin-targeting lanthanide complex: synthesis and evaluation as a tumor-homing luminescent probe

The application of lanthanide complexes in the time-resolved fluorescence imaging of living cells has emerged in the last few decades, providing high-contrast images of cells through detection of the delayed emission. In the present study, we synthesized novel trivalent lanthanide complexes containing the cyclic peptide c(RGDfK) to visualize the α_vβ₃-integrin-expressing tumor cells. Conjugation of c(RGDfK) with the macrocyclic bipyridine ligand had little effect on the fluorescence properties of the complex, indicating that the coordinated lanthanide ion was well isolated from the peptide. Bright luminescence images of α_vβ₃-integrin-expressing U87-MG cells were successfully obtained by employing the probes.     

Synthesis and properties of Re(I) tricarbonyl complexes of 6,6′-disubstituted-4,4′-bipyrimidines with high energy excited states suitable for incorporation into polynuclear arrays

A series of complexes [(N-N)Re(CO)₃X]ⁿ (N-N = 6,6′-diaryl-4,4′-bipyrimidine, axial ligand X = Cl, MeCN, 4-phenyl-pyridine, or t-Bu-pyridine) have been synthesized and characterized. The substituent aryl on the bipyrimidine, as well as the axial ligand X, has important effects on the properties of these complexes. The co-planarity of the 4,4′-bipyrimidine core and its substituents contributes to the extent of π-electron delocalization and, hence, to the redox and spectroscopic properties of the complexes. The complexes exhibit Re-to-bpm metal-to-ligand charge transfer absorptions in the range of 379-464 nm, which are red-shifted with the increase in the delocalization in the substituted bpm ligand and the increase in the donor character of the axial ligand. The electrochemical data support metal-based oxidations (from +1.07 to +1.40 V) and ligand-based reductions (from −0.62 to −0.75 V) and correlate well with those obtained by UV-Vis spectroscopy. The X-ray crystal structures of two of the complexes have also been investigated.     

Electrochemical behaviour of acyclic and macrocyclic complexes of nickel(II), copper(II) and uranyl(VI)

The electrochemical behaviour of a series of mono-nuclear, homo- and hetero-dinuclear complexes of dioxouranium(VI), nickel(II) and copper(II) ions with acyclic and cyclic compartmental ligands, derived from the condensation of 2,6-diformyl-4-chlorophenol and polyamines of the type NH₂(CH₂)₂X(CH₂)₂NH₂ (XNH, S), is reported. The kinetic and thermodynamic aspects governing the electrode mechanism are also discussed with respect to the different ligand designs and their differences in the donor atom sets.     

Syntheses, structures and luminescence properties of five lanthanide-isonicotinate coordination polymers

Five isostructural compounds of lanthanide with isonicotinate ligand, formula as [Ln(IN)₂(H₂O)₄](NO₃) (Ln = La, Nd, Eu, Tb and Er, 1−5, IN = isonicotinate), were synthesized under hydrothermal conditions by tuning the pH level and the ratio of lanthanide with isonicotinic acid. These compounds were characterized by single-crystal X-ray structure analysis, elemental analysis, IR and TG-DTA. In five compounds, the adjacent eight-coordination lanthanide centers were linked together through the bidentate bridging carboxylate groups of isonicotinate ligands to generate infinite chain structures which were further interconnected to form 3D supramolecular networks via the OW-H···N (nitrogen atom came from isonicotinate ligands) and OW-H···O (oxygen atom came from nitrate) hydrogen bonds. Compounds 3 and 4 show strong red and green emission, corresponds to ⁵D₀→⁷F₂ transition of Eu³⁺ ions and ⁵D₄→⁷F₅ transition of Tb³⁺ ions, respectively.     

Amide derivatives of Gallic acid: Design,synthesis and evaluation of inhibitory activities against in vitro α-synuclein aggregation

Gallic acid (GA), a natural phenolic acid, has received numerous attention because of its anti-oxidative, anti-inflammatory, and anti-cancer activity. More importantly, GA can act as an efficient inhibitor of α-Synuclein (α-Syn) aggregation at early stages. Nevertheless, some evidences suggest that GA is unlikely to cross the blood–brain barrier because of its high hydrophilicity. Hence, GA may not be considered as a promising candidate or entering brain and directly affecting the central nervous system. Accordingly, we have designed and synthesized a series of amide derivatives of GA, some of which possess appropriate lipophilicity and hydrophilicity with LogP (2.09–2.79). Meanwhile, these sheet-like conjugated compounds have good π-electron delocalization and high ability of hydrogen-bond formation. Some compounds have shown better in vitro anti-aggregation activities than GA towards α-Syn, with IC₅₀ down to 0.98 μM. The valid modification strategy of GA is considered an efficient way to discover novel inhibitors of α-Syn aggregation.     

Cry1Fa对Cry1Ac抗性棉铃虫的毒力评价

为了防治多种鳞翅目害虫, 表达Cry1Fa的转基因玉米和棉花已在美国商业化种植。明确棉铃虫Helicoverpa armigera对Cry1Fa与Cry1Ac的交互抗性及这两种杀虫蛋白之间的协同作用, 可以为表达 Cry1Fa+Cry1Ac的转双价抗虫棉花的合理应用提供依据。本实验测定了Cry1Fa对棉铃虫敏感品系（96S）及用Cry1Ac筛选的抗性品系（BtR, 抗性倍数2 194.15倍）的毒力, 发现Cry1Fa对敏感棉铃虫的毒力远低于Cry1Ac, LC₅₀值是Cry1Ac的504.80倍; 而且抗性品系BtR对Cry1Fa存在19.98倍的交互抗性。Cry1Fa与Cry1Ac混用可以提高Cry1Fa毒杀敏感棉铃虫的效果, 尤其是Cry1Fa浓度较低时, 加入Cry1Ac, 可以显著增加Cry1Fa的毒力; 但只有加入较高浓度的Cry1Fa时才能增加Cry1Ac的毒力。由于BtR品系已经对Cry1Ac产生抗性, Cry1Ac对抗性棉铃虫的毒力明显降低; 在较高浓度的Cry1Ac中加入Cry1Fa可以显著增加棉铃虫的死亡率（P=0.0015, F=6.88, df=6）, 但最高死亡率仅为58.33%。D-饱和最优试验的结果证实, Cry1Ac对于敏感棉铃虫的死亡率的影响达到显著水平（t₁=13.76﹥t_0.05）, Cry1Ac与Cry1Fa的交互作用对毒力的影响也达到显著水平（t₂₂=2.42﹥t_0.05; t₁₁=6.95﹥t_0.05; t₁₂=3.43﹥t_0.05）。Cry1Ac和Cry1Fa对抗性棉铃虫死亡率的影响都达到显著水平（t₁=3.03﹥t_0.05;t₂=2.59﹥t_0.05）, 但Cry1Ac是决定抗、 感棉铃虫死亡率的关键因素; Cry1Ac与Cry1Fa最佳浓度配比范围都是1.41~2.10 μg/cm2; 在抗性品系中, Cry1Ac和Cry1Fa的交互作用不显著。所以, 尽管Cry1F+Cry1A作物扩大了杀虫谱, 但棉铃虫对这两种蛋白存在交互抗性, 而且这两种蛋白混用对治理抗Cry1Ac棉铃虫的效果不理想, 因此不建议在中国种植表达Cry1F+Cry1A的棉花。关     

Lanthanide ion catalysis of the trans-cis isomerization of trans-bis(oxalato)-diaquochromate(III) and trans-bis(malonato)diaquochromate(III) [1]

The lanthanide ion catalyzed trans-cis isomerizations of trans-bis(oxalato)diaquochromate(II) and trans-bis(malonato)diaquochromate(III) have been studied. A linear free energy relationship was found correlating the catalytic rate constants for the oxalate reaction with the corresponding formation constants of complexes formed between simple monocarboxylic acids and the light (LaGd) members of the lanthanide series. The results indicates that for this portion of the series, the reaction mechanism is related to the formation of monocarboxylate complex intermediates. When the ionic radius of the lanthanide ion decreases below a particular value (as in the latter half of the series), the metal ion remains coordinated to both carboxylates of the oxalate ion rather than simply binding to only one carboxylate. In either situation, isomerization to the cis product eventually occurs, and the lanthanide ion is released.The reaction rates associated with the trans-bis(malonato)diaquochromate(III) reaction were found to be significantly slower than those of the corresponding oxalate system. However, in the malonate system, no linear free energy relationship was found relating the catalytic rate constants with the corresponding formation constants of monocarboxylic acids. One does find a linear relationship between the catalytic rate constants for the malonate reaction and the log K₁ values for the corresponding lanthanide/malonate complexes. During the course of the trans-cis isomerization, the lanthanide ion chelates the dissociated malonate group of a pentavalent Cr(III) intermediate. In the mechanism the lanthanide ion does not aid in ring opening, and neither does it singly bond to the intermediate