Tb3＋离子与植物辣根过氧化物酶的作用方式探讨

利用紫外可见吸收光谱、红外光谱、荧光光谱、原子吸收及酶分离方法, 首次研究了稀土离子Tb^3＋与植物辣根过氧化物酶(HRP)的相互作用方式. 结果表明, Tb^3＋与HRP作用方式包括: (1) Tb^3＋与肽链上的氨基酸残基作用, 影响酶活性中心的微结构; (2) Tb^3＋能部分取代酶中的Ca^2＋; (3) Tb^3＋能部分剪切肽链上的氨基酸残基, 改变酶的结构. 因此, Tb^3＋与HRP的相互作用可能以一种方式为主, 或几种作用方式同时存在.     

Eu3+对过氧化氢酶生物催化活性的影响1

为了了解稀土微肥使植物增产的化学机理,用紫外-可见(UV-Vis)吸收光谱、同步荧光光谱和电化学方法法研究了Eu3+与过氧化氢酶(CAT)的相互作用。结果表明,由于稀土离子易与O键合,因此,Eu3+主要与CAT肽链上的氨基酸残基中的羰基氧配位,引起肽链构象的变化,而构象的变化又会诱导CAT中的血红素结构的变化。当Eu3+浓度低时,Eu3+与CAT发生相互作用能使血红素的非平面性增加,转而使血红素中活性中心Fe(III)的暴露程度增加,因此,使CAT的电化学活性和对H2O2还原的电催化活性提高。但当Eu3+的浓度高时,Eu3+会使CAT中血红素的非平面性降低,使血红素中活性中心Fe(III)的暴露程度降低,因此,降低了CAT的电化学和生物电催化活性。这说明不同浓度的Eu3+对CAT的生物活性的影响不同,所以选择适当的浓度的Eu3+对植物的生长具有促进作用。     

含异丙醇基β1-受体阻断剂的合成

高血压已成为危害人类身体健康乃至生命的重要疾病之一,发病率呈逐年上升趋势.目前临床上治疗该疾病的药物有几种类型:其中,具有氨基酸残基的普利类药物,如目前已上市的卡托普利、马来酸依拉普利、雷米普利等血管紧张素酶(ACE)抑制剂[1,2];和异丙醇衍生物,如盐酸艾司洛尔、盐酸塞利洛尔、盐酸贝凡洛尔、盐酸吡布特曼和ONO-1101等[3,4].通过构效关系分析,异丙醇衍生物类药物与受体之间的相互作用部位主要有三个:(a)胺基在体内形成的正离子与受体带负电荷的氨基酸残基形成离子键;(b)异丙醇基部分的羟基与受体间形成氢键相互作用;(c)苯环与受体的平面区域的相互作用[5].基于药物与受体之间的这些相互作用,我们合成了五个系列共26个异丙醇衍生物,它们的结构经1H NMR,MS和IR确认,其生物活性正在测试中.     

乙酰胆碱酯酶AChE与1,7-二氮杂咔唑抑制剂的作用机理的分子动力学模拟

通过分子对接、分子动力学(MD)模拟以及成键自由能分析方法,从原子水平上模拟研究了3种1,7-二氮杂咔唑衍生物(分别记为M1、M2和M3)与ACh E的结合模式及相互作用机理,分析和讨论了研究体系的静电相互作用和范德华相互作用(vd W)。用MM-PBSA方法计算的3种抑制剂与ACh E之间的结合自由能与抑制剂的实验生物活性数据(IC50值)相对应。分析结果表明,残基S286与抑制剂之间形成的氢键作用有利于抑制剂与ACh E之间的结合。范德华相互作用,尤其是抑制剂与关键残基W279和Y334的作用,对抑制剂与ACh E之间的结合自由能有较大的贡献,在区分抑制剂M1(或M2)和M3的生物活性上发挥着重要的作用。     

肽链长度对La3＋与微过氧化物酶相互作用的影响

为了了解稀土元素与酶相互作用的化学机理, 用紫外-可见(UV-Vis)吸收光谱技术和电化学方法研究了La^3＋与过氧化物酶(POD)的模型化合物, 微过氧化物酶-8 (MP-8)或微过氧化物酶-11 (MP-11)的相互作用机理. La^3＋优先与MP-8或MP-11分子中血红素卟啉环上的2个丙酸基团的羰基氧发生键合作用, 使它们的聚集程度降低, 卟啉环的非平面性增加. 由于MP-8分子聚集的倾向要小于MP-11, La^3＋使MP-8聚集程度的降低和卟啉环非平面性增加的程度要大于MP-11. 由于MP-11的肽链较长而能形成螺旋状构象, 使肽链上的羰基基团被包埋在肽链的疏水基团中, 因此, La^3＋与MP-11中肽链上的羰基氧基本上不能发生键合作用. 而MP-8的肽链较短, 不能形成螺旋状结构, La^3＋也能与肽链上的羰基氧发生键合作用.     

肽链长度对La3＋与微过氧化物酶相互作用的影响

为了了解稀土元素与酶相互作用的化学机理, 用紫外-可见(UV-Vis)吸收光谱技术和电化学方法研究了La^3＋与过氧化物酶(POD)的模型化合物, 微过氧化物酶-8 (MP-8)或微过氧化物酶-11 (MP-11)的相互作用机理. La^3＋优先与MP-8或MP-11分子中血红素卟啉环上的2个丙酸基团的羰基氧发生键合作用, 使它们的聚集程度降低, 卟啉环的非平面性增加. 由于MP-8分子聚集的倾向要小于MP-11, La^3＋使MP-8聚集程度的降低和卟啉环非平面性增加的程度要大于MP-11. 由于MP-11的肽链较长而能形成螺旋状构象, 使肽链上的羰基基团被包埋在肽链的疏水基团中, 因此, La^3＋与MP-11中肽链上的羰基氧基本上不能发生键合作用. 而MP-8的肽链较短, 不能形成螺旋状结构, La^3＋也能与肽链上的羰基氧发生键合作用.     

典型蛋白质折叠中阳离子-π相互作用的特异性

蛋白质中的阳离子-π相互作用是带正电荷的氨基酸(Lys、Arg)和芳香族氨基酸(Phe、Tyr、Trp)之间的一种作用力.对α/β类蛋白中两种典型折叠类型(单绕和双绕)的研究表明:(1)单绕结构中阳离子-π相互作用的分布密度大约是双绕结构中的2.6倍;(2)在单绕结构中,样本所含氨基酸残基数量与样本中阳离子-π的数量有明显的相关性,在双绕结构中没有发现类似的相关性;(3)Lys、Arg与Tyr在单绕中比在双绕中更容易形成阳离子-π相互作用;(4)Arg-Tyr组合在单绕中出现的几率较大,Arg-Phe组合在双绕中出现的几率较大;(5)阳离子-π相互作用在65%的单绕样本中形成阵列或分布在结构的首尾间.     

5-硝基-1H-吲哚-2-羧酸与牛血红蛋白相互作用的分子模拟与光谱研究

运用密度泛函理论B3LYP/6-31G*方法对5-硝基-1H-吲哚-2-羧酸(NIA)的几何构型进行了全优化.在这基础上,用分子对接技术确定了NIA与牛血红蛋白(BHb)之间的作用位点、作用力类型及相互作用能.理论计算的结果表明NIA和BHb相互作用的静电能是-208.9 kcal*mol-1,范德华能为-180.5 kcal*mol-1,势能为-389.4 kcal*mol-1.NIA与BHb中A链上的Leu129、Ser133残基形成氢键,而NIA分子中的骨架苯环部分易与疏水氨基酸,包括产生荧光的Tyr残基等发生作用,这与 NIA能使BHb荧光淬灭的实验结果是一致的.     

L-乳酸脱氢酶抑制剂抑制成因的探讨

应用HF/3 21G研究了抑制剂H2N－CO－COO－对L 乳酸脱氢酶的抑制成因.结果表明,酶被抑制的主要原因有:(1)抑制剂与底物的稳定构象态在结构上极为相似,导致酶不能有效识别底物;(2)模型抑制剂各原子所带净电荷的优势使抑制剂更易与酶活性中心结合;(3)抑制剂通过对酶的诱导契合作用使酶活性中心的空间被缩小;(4)对活性中心有关结构的分析表明,底物的甲基分子片以及酶的氨基酸残基Gln 102,对催化反应能否顺利进行,影响极大.     

细胞色素b5 S64X突变体对蛋白结构及稳定性的影响

为了深入了解细胞色素b₅(Cyt b₅)64位氨基酸残基(Ser64)对血红素辅基微环境及蛋白性质的影响,我们分别对Cyt b₅ Ser64进行了保守性突变(S64T)以及非保守性突变(S64K、S64N和S64H),均为亲水性氨基酸残基。对野生型细胞色素b₅及其突变体蛋白S64X(X：T,K,N或H)的热、酸、盐酸胍变性的稳定性研究表明：4个突变体蛋白的稳定性相对于野生型都大大降低了;CD光谱表明,细胞色素b₅ S64X突变体中的α-螺旋明显减少,芳香性氨基酸残基所处的肽链结构受到了影响;盐酸胍变性荧光光谱表明,Trp22周围的蛋白肽链受到了影响,Trp22暴露于水溶液的程度加大。我们认为Ser64不仅对血红素辅基有稳定作用,同时还对维持蛋白Core 1中的第5个α-螺旋结构有重要的作用,在64位引入其他氨基酸残基影响了第5个α-螺旋的结构,并通过蛋白肽链的相互作用,使得Trp22所在的Core 2结构也受到了较为明显的扰动。     

基于稀土离子介导石墨烯量子点荧光开关的凝血酶生物传感器

稀土离子(Er3+)可与荧光石墨烯量子点(GQDs)表面的含氧基团发生配位,在Er3+介导下形成高配位数的GQDs/Er3+配合物,引起GQDs聚集而使其荧光减弱.凝血酶(Tb)中的氮和氧等原子可与Er3+发生配位作用,从而与GQDs竞争结合Er3+,减弱了GQDs与Er3+的作用而使其荧光恢复.通过检测GQDs的荧光即可实现对Tb活性的高灵敏分析,构建了基于Er3+介导GQDs荧光开关的Tb传感方法,采用透射电镜、原子力显微镜、红外吸收光谱以及荧光光谱等对传感机理进行了研究.本方法对Tb的检出限低至0.049 nmol/L,其它蛋白质对Tb检测无明显干扰,实际样品中Tb加标回收率为98.0%~105.3%,相对标准偏差为0.6%~4.2%.     

Spectroscopic studies of interactions involving horseradish peroxidase and Tb3+

The spectroscopic properties of interactions involving horseradish peroxidase (HRP) and Tb(3+) in the simulated physiological solution was investigated with some electrochemical and spectroscopic methods, such as cyclic voltammetry (CV), circular dichroism (CD), X-ray photoelectron spectroscopy (XPS) and synchronous fluorescence (SF). It was found that Tb(3+) can coordinate with oxygen atoms in carbonyl groups in the peptide chain of HRP, form the complex of Tb(3+) and HRP (Tb-HRP), and then lead to the conformation change of HRP. The increase in the random coil content of HRP can disturb the microstructure of the heme active center of HRP, in which the planarity of the porphyrin cycle in the heme group is increased and then the exposure extent of the electrochemical active center is decreased. Thus Tb(3+) can inhibit the electrochemical reaction of HRP and its electrocatalytic activity for the reduction of H(2)O(2) at the Au/Cys/GC electrode. The changes in the microstructure of HRP obstructed the electron transfer of Fe(III) in the porphyrin cycle of the heme group, thus HRP catalytic activity is inhibited. The inhibition effect of Tb(3+) on HRP catalytic activity is increased with the increasing of Tb(3+) concentration. This study would provide some references for better understanding the rare earth elements and heavy metals on peroxidase toxicity in living organisms.     

Fluorescent studies on the binding-Ca2 + in fibrinolytic principle separated from snake venom

By using equilibrium dialysis, atomic absorption spectrometry, fluorescence titration and determination of fluorescence lifetime, it can be determined that each fibrinolytic principle (FP) molecule contains one Ca2+-binding site and one Ca2+ ion, which can be substituted by a Tb3+ ion completely. The intramolecular energy transfer between Tb3+ and the tryptophan (Trp) residue in FP has been investigated through fluorescence spectroscopy. In the FP molecule, the excited energy can transfer from the Trp residue as an energy donor to the Tb3+ ion substituted as an acceptor. The distance between Tb3+ and the Trp residue, approximately 0.38 nm, has been calculated with the experimental data and Forster theory.     

Photophysical properties of terbium molecular-based hybrids assembled with novel ureasil linkages

Three silica-based organic-inorganic hybrid systems composed of hydroxyl aromatic derivatives (2-acetylphenol [HAP], 2-hydroxy-3-methylbenzoic acid [HMBA], 3-hydroxy-meta-phthalic acid [HMPHTH] complexes) were prepared via a sol-gel process. The active hydroxyl groups of the three ligands grafted by 3-(triethoxysilyl)-propyl isocyanate (TESPIC) through hydrogen transfer addition reaction were used as multi-functional bridge components, which can coordinate to Tb3+ with carbonyl groups, strongly absorb ultraviolet light and effectively transfer energy to Tb3+ through their triplet excited state, as well as undergo polymerization or crosslinking reactions with tetraethoxysilane (TEOS), for anchoring terbium ions to silica backbone. NMR, FT-IR, UV-vis absorption, luminescence spectroscopy was used to investigate the obtained hybrid material. UV excitation in the organic component resulted in strong green emission from Tb3+ ions due to an efficient ligand-to-metal energy transfer mechanism.     

Amperometric sensor for hydrogen peroxide based on electric wire composed of horseradish peroxidase and toluidine blue-multiwalled carbon nanotubes nanocomposite

A kind of nanocomposites with good dispersion in water was prepared through noncovalent adsorption of toluidine blue (Tb) on multiwalled carbon nanotubes (MWCNT) for electric communication between horseradish peroxidase (HRP) and electrode. The nanocomposites could be conveniently cast on electrode surface. With the aid of chitosan, HRP was then immobilized on the nanostructure to form a reagentless amperometric sensor for hydrogen peroxide. UV-vis spectroscopy and electrochemical impedance spectroscopy were used to characterize the adsorption of Tb on MWCNT. The presence of both Tb as mediator of electron transfer and MWCNT as conductor enhanced greatly the enzymatic response to the reduction of hydrogen peroxide. The novel biosensor exhibited fast response towards hydrogen peroxide with a detection limit of 1.7x10(-6)M and the linear range extended up to 4x10(-4)M without the interference of ascorbic acid and uric acid. The Michaelis-Menten constant (K'(m)) of the immobilized HRP was evaluated to be 0.16mM.     

Laser spectroscopic studies of Tb3+-doped oxyfluoroborate glass

Tb3+-doped oxyfluoroborate glasses have been prepared for different concentrations of Tb. The absorption, fluorescence and photoacoustic spectra of these have been recorded and studied. It is marked that the fluorescence intensity of different fluorescence transitions decreases with the increase of Tb ion concentration in the glass. This quenching at higher concentration is due to the energy transfer among the excited and nearest neighbor unexcited Tb ions in the glass. The lifetime measurement confirms it, as the lifetime of a particular state was found to decrease with the increase of Tb ion concentration in the glass. The mechanism of the energy transfer process was determined to involve quadrupole quadrupole interaction. We have also studied the energy transfer from Tb3+-->Pr3+ when both the rare earths are doped together in the glass. A decrease in the lifetime of the 5D4 level of Tb3+ with the increase of Pr3+ concentration confirms this.     

Cu2+对不同相形态中聚3-己基噻吩光学性质的影响

用紫外-可见吸收光谱和荧光光谱方法研究了Cu2+分别与稀溶液、分散液和薄膜三种体系中的聚3-己基噻吩(P3HT)的相互作用. 结果表明, P3HT的相形态对其相互作用有重要影响. 在四氢呋喃的稀溶液中, P3HT与Cu2+的溶剂化程度都很高, 它们之间几乎不存在化学作用; 在分散液中, P3HT形成聚集的颗粒, Cu2+的加入产生较弱的氧化掺杂, Cu2+部分进入到分散颗粒中; 在P3HT的薄膜中, Cu2+使链的共轭长度变短, 引起光吸收蓝移.     

Light Emitting Diodes Prepared from Terbium‐Immobilized Polyurea Chelates

Abstract

This article describes the synthesis and application of poly(1,4‐phenylene‐2,6‐pyridylurea) (MCPU) as a charge transporting and rare earth metal chelating host matrix for organic light emitting diodes (OLEDs). The chelation between MCPU and Terbium (Tb³⁺) (the rare earth metal used in this study), is facile in nature and persists in thin films obtained by spin coating onto various substrates. Multiple polymer chelating moieties at each Tb ion site may derive from MCPU repeat units from a single polymer chain or two polymer chains, and their respective structures are proposed. The emissive properties of these films in the presence and absence of Terbium (Tb³⁺) were characterized by steady state UV‐VIS absorption spectroscopy and photoluminescence (PL) spectroscopy. The PL emission from Tb(MCPU) films indicate contribution from both the host MCPU and the Tb ions. The incorporation of these films in OLEDs employing different device architectures yields electroluminescence spectra, which show the characteristic emission of the Tb ions but no emission from the host polymer matrix. Although these devices are not optimized, they exhibit an order of magnitude higher external quantum efficiency as compared to that of conventional aluminum tris 8‐hydroxyquinoline (Alq₃) based OLEDs, at low current densities.     

Tb3+离子4f75d组态能级的电子云扩大效应

研究了电子云扩大效应对Tb3+离子5d能级的影响. 利用光谱理论, 将电子云扩大效应比率β同Tb3+离子4f75d组态的自旋允许和禁阻跃迁能级的能级差联系起来, 通过复杂晶体化学键理论确定了化学键的共价性、 相应键体积极化率以及配体离子的有效电荷与β的线性关系, 同时得到了对β有影响并与Tb3+离子自身相关的因子.