杨小舟蛾雌蛾性信息素活性成分的鉴定

【目的】鉴定杨小舟蛾Micromelalopha sieversi雌蛾性信息素活性成分的结构信息。【方法】采用正己烷浸提的方法提取杨小舟蛾性成熟处女雌蛾性腺中的活性成分;利用气相色谱-触角电位联用(GC-EAD)技术对其活性成分进行定位;性腺提取物与4-甲基-1,2,4-三唑啉-3,5-二酮(MTAD)进行微量化学反应,获得衍生物;利用气相色谱-质谱联用(GC-MS)技术分别对性腺提取物及MTAD衍生物进行质谱特征离子分析。【结果】GC-EAD结果显示,杨小舟蛾雄蛾触角对雌蛾性信息素腺体提取物中的一种成分有较好的反应;GC-MS分析结果表明,能引起雄蛾触角电生理反应的成分为十八碳的不饱和醛;MTAD衍生物的GC-MS结果显示,该活性成分的两个双键分别位于碳链的13和15位。【结论】本研究鉴定出杨小舟蛾雌蛾性信息素活性成分的平面结构为13,15-十八碳二烯醛,但双键的立体构型有待合成标准化合物进一步鉴定。本研究为杨小舟蛾性信息素备选化合物的筛选提供了方向,为信息素的结构确证奠定了基础。     

松毛虫性信息素的固相微萃取及质谱和触角电位分析

松毛虫性信息素成分在腺体中含量很低。本研究利用固相微萃取（SPME）技术近距离长时间采集单头云南松毛虫Dendrolimus houi处女雌蛾释放的性信息素成分, 并进一步利用气相色谱-质谱（GC-MS）和气相色谱-触角电位联用（GC-EAD）技术分析SPME采集的性信息素成分。 结果显示: 在云南松毛虫处女雌蛾求偶召唤期间SPME聚乙二醇/二乙烯基苯（CAR/DVB）萃取头吸附了大量的反5, 顺7-十二碳二烯醇（E5, Z7-12:OH）和反5, 顺7-十二碳二烯乙酸酯（E5, Z7-12:OAc）成分及微量的反5, 顺7-十二碳二烯醛（E5, Z7-12:Ald）成分, 这3种腺体成分均能激起云南松毛虫雄虫触角电位反应。与溶剂浸提昆虫性信息素成分的方法比较, SPME活体采样技术和GC-MS及GC-EAD分析方法联用研究昆虫的信息素成分具有采集的样品代表性强、样品量能满足色谱分析需要和无溶剂干扰等方面的优点。最后还着重讨论了SPME技术的应用价值、效果及实际应用中应该注意的一些问题。      

不同冬季覆盖作物对稻田甲烷和氧化亚氮排放的影响

采用静态箱-气相色谱法对不同冬季覆盖作物处理［免耕直播黑麦草-双季稻(T₁)、免耕直播紫云英 双季稻(T₂)、翻耕移栽油菜-双季稻(T₃)、免耕直播油菜-双季稻(T₄)和冬闲-双季稻(CK)］下稻田甲烷（CH₄）和氧化亚氮（N₂O）排放进行观测,分析了不同冬季覆盖作物对稻田CH₄和N₂O排放的影响.结果表明：在冬季作物生长期,不同冬季覆盖作物稻田CH₄和N₂O总排放量与对照（CK）的差异均达到极显著水平（P<0.01）;T₃和T₁处理的稻田CH₄和N₂O排放量最高,其CH₄排放量分别为0.88 和0.60g·m^-2,N₂O排放量分别为0.23 和0.20 g·m^-2;冬季作物还田后,各处理早、晚稻田CH4排放量均明显高于对照.早稻田CH₄排放量最高的为T₁和T₂处理,分别达21.70和20.75 g·m^-2;晚稻田CH₄排放量最高的为T₃和T₄处理,分别为58.90和54.51 g·m^-2.各处理早、晚稻田N₂O总排放量均显著高于对照,T₁、T₂、T₃和T₄处理的早稻田N₂O总排放量分别比对照增加53.7%、12.2%、46.3%和29.3%,晚稻田分别比对照增加28.6%、3.8%、34.3%和27.6%.     

大型丝状藻类对城市河流甲烷排放的影响研究进展

温室气体排放导致的全球变暖受到广泛关注.近期研究发现,经由河流系统排放的二氧化碳（CO₂）和甲烷（CH₄）可部分抵消陆地生态系统的碳固定量,从而使人们开始重新思考河流对于全球碳平衡和温室气体排放清单的影响.作为城市河流系统中重要的初级生产者,大型丝状藻类通过改变水-沉积物界面物理、化学以及生物等环境因子,深刻影响着河流生态系统的碳循环过程.本文从3个方面阐述大型丝状藻类对于城市河流中CH₄排放的影响:城市化对河流生态系统及其CH₄排放通量的影响;大型丝状藻类对自然河流系统中CH₄产生与排放过程的影响;大型丝状藻类对城市河流系统初级生产力及CH₄产生过程的影响.最后对目前存在的问题和今后的研究方向进行了展望.     

春尺蠖性信息素活性成分的提取和GC-MS鉴定

为了寻求高效无污染的防治害虫春尺蠖Apocheima cinerarius Erschoff的方法, 本实验对春尺蠖雌蛾性信息素进行了初步研究。本研究采取正己烷溶剂浸提法提取春尺蠖处女雌蛾性信息素腺体中的性信息素,运用气相色谱-触角电位联用仪(gas chromatography-electroantennographic detection, GC-EAD) 测定春尺蠖雄蛾触角对雌蛾性信息素腺体提取物中性信息素成分的活性反应, 并运用气相色谱-质谱联用仪(gas chromatograph-mass spectrum, GC-MS）鉴定信息素成分。GC-EAD结果显示雄蛾触角对雌蛾性信息素腺体提取物中的一种成分有较好的反应。GC-MS分析结果表明能引起雄蛾触角电生理反应的成分为含有十四个碳原子直链结构的不饱和乙酸酯, 但其双键位置有待合成标准化合物进一步分析鉴定。该研究结果为春尺蠖雌蛾性信息素备选化合物的筛选提供了方向, 为其结构的确定奠定了基础。     

日本长期不同施肥稻田N2O和CH4排放特征及其环境影响

观测了75年长期连续不施肥、施硫酸铵、施熟制水稻秸秆与豆饼混合堆肥、施绿肥苜蓿4种处理下日本单季稻田温室气体N₂O和CH₄的排放特征及其环境影响.结果表明： 在水稻生长季节,不同处理间N₂O排放无显著差异,但CH₄排放差异显著;长期连续施用有机肥虽然没有增加N₂O排放却促进了CH₄排放.各系统排放N₂O和CH₄所产生的累积全球增温潜势（GWP）以绿肥处理最大（310.7 g CO₂e·m^-2）,熟制有机堆肥次之（151g CO₂e·m^-2）,硫酸铵处理最小（60.6 g CO₂e·m^-2）.稻田系统的GWP主要来自CH₄排放,控制和减少稻田系统CH₄排放是稻田温室气体减排的核心问题.长期连续施用熟制有机堆肥既能增加土壤有机质,改善地力,满足水稻高产,又能实现CH₄减排,是实践中值得推荐的水稻生产模式.     

基于挥发性脂肪酸化学计量模型体外预测山羊瘤胃甲烷产量的精度

利用挥发性脂肪酸（VFA）的化学计量模型\[CH₄=0.5Ace-0.25Pro+0.5But-0.25Val,模型1,式中,CH₄、Ace、Pro、But和Val分别表示甲烷、乙酸、丙酸、丁酸和戊酸的产量\]预测瘤胃甲烷产量的精度.选用常见的10种化学成分差异显著的饲料原料（包括4种精饲料和6种粗饲料）进行体外模拟反刍家畜瘤胃发酵试验,测定发酵72 h后的VFA组成和CH₄产量.利用模型精度分析方法比较CH₄产量预测值与实测值间的差异.结果表明： 模型1估算的CH₄生成量普遍高于实测值,其偏差、斜率和随机误差分别为62.6%、11.7%和25.7%,固定误差＞70%.考虑到VFA代谢生成氢的80%用于合成CH₄,VFA化学计量模型表达为模型2\[CH₄= 0.8(0.5Ace-0.25Pro+0.5But-0.25Val)\].与模型1相比（均方预测误差=0.60）,模型2的预测精度大大提升(均方预测误差=0.18),模型2的偏差、斜率和随机误差分别为2.1%、5.7%和92.3%,固定误差＜10%.模型1认为VFA生成过程所产生的氢全部被甲烷菌用于合成CH₄,没有考虑氢代谢的其他途径,这是导致预测值大于实测值的一个重要原因.     

日本长期不同施肥稻田N2O和CH4排放特征及其环境影响

观测了75年长期连续不施肥、施硫酸铵、施熟制水稻秸秆与豆饼混合堆肥、施绿肥苜蓿4种处理下日本单季稻田温室气体N₂O和CH₄的排放特征及其环境影响.结果表明： 在水稻生长季节,不同处理间N₂O排放无显著差异,但CH₄排放差异显著;长期连续施用有机肥虽然没有增加N₂O排放却促进了CH₄排放.各系统排放N₂O和CH₄所产生的累积全球增温潜势（GWP）以绿肥处理最大（310.7 g CO₂e·m^-2）,熟制有机堆肥次之（151g CO₂e·m^-2）,硫酸铵处理最小（60.6 g CO₂e·m^-2）.稻田系统的GWP主要来自CH₄排放,控制和减少稻田系统CH₄排放是稻田温室气体减排的核心问题.长期连续施用熟制有机堆肥既能增加土壤有机质,改善地力,满足水稻高产,又能实现CH₄减排,是实践中值得推荐的水稻生产模式.     

节水减氮和品种管理对双季稻CH4的减排效果

秸秆还田、高效肥料、节水减氮是我国农业绿色发展主推技术,高产低排放品种是减少稻田CH₄排放重要方向。为明确秸秆还田下氮肥减量及节水灌溉集成技术对不同品种水稻田CH₄排放的影响,本研究以双季稻为对象,采用随机区组的裂区试验设计,设置施用尿素+间歇灌溉(U)、尿素减量20%+秸秆还田+间歇灌溉(US+S)、控释尿素减量20%+秸秆还田+间歇灌溉(CRUS+S)、尿素减量20%+秸秆还田+节水灌溉(US+S+SWD)共4个主区因素,常规稻和杂交稻作为2个副区因素,利用静态箱-气相色谱法监测双季稻生育期内CH₄排放规律及减排效果。结果表明,碳投入、氮投入、灌溉量和分蘖数是影响双季稻CH₄排放的主要因素。秸秆还田可补充氮肥20%减量的养分,并显著促进常规稻和杂交稻CH₄的排放,其中常规稻增排60.0%～107.8%,杂交稻增排99.8%～107.8%,这主要归结于秸秆还田带来大量碳源。秸秆还田搭配控释尿素并不能减少CH₄排放,较US+S增排1.8%～9.7%(除常规...     

甜菜夜蛾触角结合蛋白Ⅱ的cDNA克隆、 组织分布及配体结合特性分析

触角结合蛋白（antennal binding proteins, ABPs）是气味结合蛋白（odorant binding proteins, OBPs）的一个亚类, 推测其在昆虫嗅觉中起作用。为了探讨这一问题, 本研究通过转录组数据分析并利用RACE技术, 克隆了甜菜夜蛾Spodoptera exigua触角结合蛋白Ⅱ基因（SexigABP2）的全长cDNA序列（GenBank登录号为HQ234486）。序列分析表明, 该基因开放阅读框长444 bp, 编码148个氨基酸, 具有OBPs典型的6个半胱氨酸位点; 其氨基酸序列和烟芽夜蛾Heliothis virescens的HvirABP2的一致性最高, 达72%。实时定量PCR分析显示, 该基因主要在触角中表达, 在喙、 足、 翅等组织中也有少量表达, 且在雌蛾触角及足中的表达量显著高于雄蛾。进一步对该基因进行原核表达和纯化, 利用荧光竞争结合实验测定了SexigABP2对35种气味物质的结合能力, 发现其对甜菜夜蛾性信息素组分(Z)-9-十四碳烯醇和植物挥发物法尼醇的结合能力较强, 结合常数分别为8.24 μmol/L和8.14 μmol/L。结合能力比较表明, SexigABP2对不饱和长碳链化合物较饱和短碳链化合物具有更强的结合能力; 在不饱和长碳链化合物中, 对醇类物质又较乙酸酯类物质具有更强的结合能力。结果提示SexigABP2可能参与了成虫对不饱和长碳链的植物挥发物的感受。     

Borane and monoiodoborane derivatives of some bis(diphenylphosphino)alkanes

A series of borane and monoiodoborane derivatives of bis(diphenylphosphino)alkanes. (C₆H₅)₂P--- (CH₂)_n---P(C₆H₅)₂ in which n has values of 2 through 4 has been synthesized. Only compounds with the formulae [(C₆H₅)₂P]₂(CH₂)_n · (BH₃)₂ and (C₆H₅)₂P]₂CH₂)_n · BH₂I were isolable, the latter being boronium iodides. The compounds were characterized by their melting points, elemental analyses, molar conductivities, infrared spectroscopy, and ¹H and ¹¹B nuclear magnetic resonance spectroscopy. The relationship between the length of the carbon chain and the ¹¹B NMR chemical shift is discussed.     

Phenylalkyl ketones as potent reversible inhibitors of interleukin-1β converting enzyme

Phenylalkyl ketones are potent reversible inhibitors of interleukin-1β converting enzyme (ICE). The extended alkyl chain ketones AcTyrValAlaAspCO(CH₂)_nPh display increased potency over the simple aryl ketone. In particular, the tetrapeptide AcTyrValAlaAspCOPh has a K_i of 10μM while AcTyrValAlaAspCO(CH₂)₅Ph has a K_i of 18.5nM.     

Binding of copper and zinc ions to polypeptides containing glutamic acid and tyrosine residues

The binding of Cu⁺⁺ and Zn⁺⁺ ions to three polypeptides containing Glu and Tyr residues, (Glu Tyr Glu)_n, (Glu-Glu-Tyr-Glu)_n and (Glu-Tyr-Tyr-Glu)_n has been investigated by absorption spectroscopy, fluorescence and circular dichroism. Difference absorption spectra show that Zn^+- slightly perturbs the absorption spectrum of the tyrosyl residue whereas Cu⁺⁺ binding is accompanied by the appearance of a strong absorption band around 245 nm. The fluorescence of the tyrosyl residue is enhanced by Zn⁺⁺ ions while it is quenched by Cu⁺⁺ ions. Cation binding induces a conformational change of the polypeptides from a random coil to an -helix, Mg⁺⁺ ions do not elicit any of these phenomena.     

开放式O3浓度增高对小麦籽粒蛋白的影响

于2006—2009年应用FACE研究平台,设计O₃浓度增高50%(E)和自然浓度(CK)两个处理,采用烟农19、扬麦16、扬麦15和扬辐麦2号4个品种,研究了O₃浓度增高对不同类型小麦品种籽粒蛋白质组分及其动态的影响.结果表明：随着O3浓度增高,籽粒蛋白质含量上升,3个年度上升幅度分别为7.55%～16.37%（2006—2007年度）、4.93%～22.63%（2007—2008年度）和2.29%～17.65%（2008—2009年度）,处理间、品种和年度间差异显著;但籽粒蛋白质产量显著或极显著下降,3个年度降幅分别为1.83%～11.64%（2006—2007年度）, -0.41%～24.22%（2007—2008年度）和-1.90%～15.81%（2008—2009年度）.籽粒蛋白质4种组分（清蛋白、球蛋白、醇溶蛋白和谷蛋白）含量均表现为O₃浓度增高处理高于自然浓度处理,品种间和年度间差异显著,且处理间醇溶蛋白和球蛋白含量差异显著,而清蛋白和谷蛋白含量差异不显著.     

Misdirected π-donor ligands: (η-C5H5)2Zr(Cl) (SR) with sterically more demanding R groups have lower rotational barriers

Rotational barriers about the M-S bonds of 16-electron bent metallocene monothiolates (η⁵-C₅H₅)₂Zr(Cl) (SR) (R = −CH₃, −CH₂CH₃, −CH(CH₃)₂, −C(CH₃)₃) (1a–d) have been measured by dynamic ¹H NMR methods: 32, 33, 35 and 26 kJ mol⁻¹, respectively. The ground-state orientation about the Zr-S bonds of 1 that maximizes Spπ → Mdπ bonding (Cl-Zr-S-R ≈ 90°) also maximizes CpR steric interaction, whereas the rotational transition-state orientation (Cl-Zr-S-R ≈ 0°) is one that minimizes Spπ → Mdπ bonding and maximizes ClR steric interaction. Deviation from a ground-state orientation that is ideal for Spπ → Mdπ bonding might be expected as the size of the R group and CpR steric interaction increases. Thus, the aberrant trend for the R = −C(CH₃)₃ derivative could be attributed to a ground-state steric effect where the sterically demanding −C(CH₃)₃ group forces an unfavorable (misdirected) orientation for Mdπ-Spπ bonding, but a favorable orientation with respect to CpR and ClR steric interactions. However, the solid-state structures of (η⁵-C₅H₅)₂Zr(SR)₂ (R = −CH₃, −CH₂CH₃, −CH(CH₃)₂, −C(CH₃)₃) (2a–d) exhibit regular variation of their metric parameters as evidenced by their Zr-S-C bond angles of 108, 109, 113, and 124° and S-Zr-S′ bond angles of 97, 99, 100 and 106°, respectively. Neither the S′-Zr-S-R torsion angles nor the dihedral angles that describe the relationship between the S/Zr/S′ and Cp(centroid)/Zr/Cp′ (centroid) planes (both indicators of the relative orientation of the Zr dπ acceptor orbital and the thiolate S pπ donor orbital) reflect the steric demand of the R group. Thus, the size of the R group imposes a measured effect on the geometry of 2 and the tert-butyl group is not extraordinary. Although the enthalpic and entropic effects could not be deconvoluted for rotation about the Zr-S bond of 1 in the present study, literature precedents suggest that both enthalpic and entropic effects may play a role in determining the irregular trend that is observed.     

A reversible NO complex of Fe(TIM): an S = 1/2FeNO nitrosyl

[Fe(TIM)(CH₃CN)₂](PF₆)₂ (1) (TIM = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclodeca-1,3,8,10-tetraene) forms a complex with NO reversibly in CH₃CN (53±1% converted to the NO complex) or 60% CH₃OH/40% CH₃CN (81±1% conversion). Quantitative NO complexation occurs in H₂O or CH₃OH solvents. The EPR spectrum of [Fe(TIM)(solvent)NO]²⁺ in frozen 60/40 CH₃OH/CH₃CN at 77 K shows a three line feature at g=2.01, 1.99 and 1.97 of an S=1/2FeNO⁷ ground state. The middle line exhibits a three-line N-shf coupling of 24 G indicating a six-coordinate complex with either CH₃OH or CH₃CN as a ligand trans to NO. In H₂O [Fe(TIM)(H₂O)₂]²⁺ undergoes a slow decomposition, liberating 2,3-butanedione, as detected by ¹H NMR in D₂O, unless a π-acceptor axial ligand, L=CO, CH₃CN or NO is present. An equilibrium of 1 in water containing CH₃CN forms [Fe(TIM)(CH₃CN)(H₂O)]²⁺ which has a formation constant K_CH3CN=320 M⁻¹. In water K_NOK_CH3CN since NO completely displaces CH₃CN. [Fe(TIM)(CH₃CN)₂]²⁺ binds either CO or NO in CH₃CN with K_NO/K_CO=0.46, sigificantly lower than the ratio for [Fe^II(hemes)] of 1100 in various media. A steric influence due to bumping of β-CH₂ protons of the TIM macrocycle with a bent S=1/2 nitrosyl as opposed to much lessened steric factors for the linear Fe---CO unit is proposed to explain the lower K_NO/K_CO ratio for the [Fe(TIM)(CH₃CN)]²⁺ adducts of NO or CO. Estimates for formation constants with [Fe(TIM)]²⁺ in CH₃CN of K_NO=80.1 M⁻¹ and K_CO=173 M⁻ are much lower than to hemoglobin (where K_NO=2.5×10¹⁰ M⁻¹ and K_CO=2.3×10⁷) due to a reversal of steric factors and stronger π-backdonation from [Fe^II(heme)] than from [Fe^II(TIM)(CH₃CN)]²⁺.     

Ion trap MS/MS of intact testosterone and epitestosterone conjugates--adducts, fragile ions and the advantages of derivatisation

In ion trap mass spectrometry, fragile ions may fragment under the application of resonance ejection during precursor mass isolation, reducing MS/MS spectral intensity. In this study the steroidal epimers testosterone glucuronide (TG) and epitestosterone glucuronide (EG) have been chosen as a model for exploring whether compound structure is linked to ion trap fragility. Both compounds form multiple adducts by ESI-MS, namely protonation, ammonium and sodium, however, the mass spectrum of EG displays a more intense ammonium adduct peak than TG. [TG + NH₄]⁺, [EG + NH₄]⁺ and [EG + H]⁺ were found to be fragile ions. To explain the differences in adduct formation and fragility, molecular modelling was employed. Ammonium adduction was localised to the glucuronide ring oxygens and while EG has eight possible adduction sites, only seven were located for TG explaining the increased ammonium adduct abundance with EG. In EG the bond between the steroid and the glucuronide was slightly longer and the oxygen in this bond was more basic than TG. This shows that the EG bond is weaker which may contribute to the fact that [EG + H]⁺ but not [TG + H]⁺ is fragile. To investigate whether stability could be restored by chemical means, EG was derivatised with tris(trimethoxyphenyl)phosphonium chloride or methylated on the carboxylic acid and Girard P or methoxylamine on the 3-keto group. Derivatisation of the steroid rather than the glucuronide eliminated fragility and using a charged derivative eliminated adduct formation. This work demonstrates the importance of carefully considering the nature of the derivative and the site of derivatisation.     

Monovalent copper as a potential catalyst for formation of acetaldehyde via the migration of methyl radicals to the coordinated carbonyl in the complex (CO)Cu-CH3

Cu_aq⁺ forms stable complexes with carbon monoxide in aqueous solutions. Furthermore it reacts very fast with aliphatic radicals. The reaction of Cu(CO)_maq⁺ with methyl radicals, ^•CH₃ was studied using the pulse-radiolysis technique. The results point out that methyl radicals react with Cu(CO)_aq⁺ to form an unstable intermediate with a Cu^II-C σ bond identified as (CO)Cu^II-CH₃⁺, k = (1.1±0.2) × 10⁹ M⁻¹ s⁻¹. This intermediate has a strong LMCT charge transfer band (λ_max = 385 nm, _max = 2500 M⁻¹ cm⁻¹) which is similar to the absorption bands of other transient complexes with Cu^II-alkyl σ bonds. The coordinated carbon monoxide in (CO)Cu^II-CH₃⁺ inserts into the copper—carbon bond (or rather the coordinated methyl migrates to the coordinated carbon monoxide ligand) at a rate of (3.0±0.8) × 10² s⁻¹ to form the copperacetyl complex (CO)_mCu^II-C(CH₃)=O⁺ (λ_max = 480 nm, _max = 2100 M⁻¹ cm⁻¹). The rate of formation of (CO)Cu^II-CH₃⁺ and of the insertion reaction are pH independent. The complex (CO)_mCu^II-C(CH₃)=O⁺ is also unstable and decomposes heterolytically to yield acetaldehyde and Cu_aq²⁺ as the final stable products. This reaction is slightly pH dependent. The same reactivity pattern has been observed for the Cu(CO_naq⁺ complexes (n = 2 or 3). The results clearly point out that CO remains coordinated to transient complexes of the type Cu^II-alkyl.     

Solvent Effects in the Spin Trapping Of Lipid Oxyl Radicals

Studies documenting spin trapping of lipid radicals in defined model systems have shown some surprising solvent effects with the spin trap DMPO. In aqueous reactions comparing the reduction of H₂O₂ and methyl linoleate hydroperoxide (MLOOH) by Fe^z+, hydroxyl (HO·) and lipid alkoxyl (LO·) radicals produce identical four-line spectra with line intensities 1:2:2:1. Both types of radicals react with commonly-used HO· scavengers, e.g. with ethanol to produce ·C(CH₃)HOH and with dirnethylsulfoxide (DMSO)togive ·CH₃. However, DMSO radicals (either ·CH₃or ·OOCH₃) react further with lipids, and when radicals are trapped in these MLOOH systems, multiple adducts are evident. When acetonitrile is added to the aqueous reaction systems in increasing concentrations, ·CH₂CN radicals resulting from HO· attack on acetonitrile are evident, even with trace quantities of that solvent. In contrast, little, if any, reaction of LO· with acetonitrile occurs, even in 100% acetonitrile. A single four-line signal persists in the lipid systems as long as any water is present, although the relative intensity of the two center lines decreases as solvent-induced changes gradually dissociate the nitrogen and β-hydrogen splitting constants. Extraction of the aqueous-phase adducts into ethyl acetate shows clearly that the identical four-line spectra in the H₂0₂ and MLOOH systems arise from different radical species in this study, but the lack of stability of the adducts to phase transfer may limit the use of this technique for routine adduct identification in more complex systems. These results indicate that the four-line 1:2:2:1. a_N = a_H = 14.9G spectrum from DMPO cannot automatically be assigned to the HO· adduct in reaction systems where lipid is present, even when the expected spin adducts from ethanol or DMSO appear confirmatory for HO-. Conclusive distinction between HO· and LO· ultimately will require use of ¹³C-labelled DMPO or HPLC-MS separation and specific identification of adducts when DMPO is used as the spin trap.     

基于[Ru(phen)2(bpip)] 2+-DNA相互作用的共振光散射增强建立纳克级DNA的测定方法

通过研究钌多吡啶类配合物［Ru(phen)2(bpip)］2+与DNA相互作用的共振光散射等光谱,我们发现［Ru(phen)2(bpip)］²⁺与DNA相互作用的方式包括插入作用和静电作用模式.同时基于［Ru(phen)2(bpip)］²⁺ DNA体系增强的共振光散射现象,建立了一种简单、快速的测定纳克级核酸的新方法.实验结果表明体系在373 nm处共振光散射强度的增强与DNA的浓度呈线性关系.线性范围为0.025～1.250 mg/L,线性公式为△I_RLS=283.14C+2.26 (mg/L),相关系数为0.9983,DNA的检出限为5.7 ng/mL. 应用到实际样品的分析中,结果令人满意.