Adsorption of amino acids by fullerenes and fullerene nanowhiskers

Abstract

We have investigated the adsorption of some amino acids and an oligopeptide by fullerene (C₆₀) and fullerene nanowhiskers (FNWs). C₆₀ and FNWs hardly adsorbed amino acids. Most of the amino acids used have a hydrophobic side chain. Ala and Val, with an alkyl chain, were not adsorbed by the C₆₀ or FNWs. Trp, Phe and Pro, with a cyclic structure, were not adsorbed by them either. The aromatic group of C₆₀ did not interact with the side chain. The carboxyl or amino group, with the frame structure of an amino acid, has a positive or negative charge in solution. It is likely that the C₆₀ and FNWs would not prefer the charged carboxyl or amino group. Tri-Ala was adsorbed slightly by the C₆₀ and FNWs. The carboxyl or amino group is not close to the center of the methyl group of Tri-Ala. One of the methyl groups in Tri-Ala would interact with the aromatic structure of the C₆₀ and FNWs. We compared our results with the theoretical interaction of 20 bio-amino acids with C₆₀. The theoretical simulations showed the bonding distance between C₆₀ and an amino acid and the dissociation energy. The dissociation energy was shown to increase in the order, Val < Phe < Pro < Asp < Ala < Trp < Tyr < Arg < Leu. However, the simulation was not consistent with our experimental results. The adsorption of albumin (a protein) by C₆₀ showed the effect on the side chains of Try and Trp. The structure of albumin was changed a little by C₆₀. In our study Try and Tyr were hardly adsorbed by C₆₀ and FNWs. These amino acids did not show a different adsorption behavior compared with other amino acids. The adsorptive behavior of mono-amino acids might be different from that of polypeptides.     

Noncovalent interactions of amino acids with fullerene C60: A dispersion-corrected DFT study

By using the general gradient approximation functional PBE with Grimme's empirical dispersion correction in conjunction with the double numerical basis set DNP, we studied the noncovalent interaction of twenty proteinogenic l-amino acids (AAs) with fullerene C₆₀. The calculations were performed both under vacuum conditions and in aqueous medium. We analyzed the calculated geometries and binding energies for AA+C₆₀ complexes, the shape of HOMO and LUMO orbitals and the corresponding gap energies. Generally, we found a poor correlation between binding energies calculated for AA+C₆₀ complexes in aqueous medium and hydrophobicity scales proposed by other other authors. Despite of C₆₀ cage can be envisioned as a typical hydrophobic surface, the AA adsorption apparently takes place according to a mechanism different from classical hydrophobic interactions, or due to a combination of several types of interactions with a limited contribution of hydrophobic mechanism.     

氨基酸磁性分子印迹微球的制备及吸附性能研究

采用分子印迹技术,以Ala和Phe为模板分子,苯乙烯和甲基丙烯酸为共聚单体,二乙烯苯为交联剂,Fe3O4为磁性载体,制备了对两种氨基酸有特异性识别的磁性分子印迹聚合物Ala-MMIPs和Phe-MMIPs。研究了两种印迹聚合物的吸附特性,并探讨了吸附机理。结果表明,Phe在其印迹聚合物上的最大吸附量和吸附平衡常数分别为231.62μmol/g和0.21L/mmol;而Ala在它的印迹微球上的最大吸附量和吸附平衡常数分别为179.16μmol/g和0.12L/mmol。说明Phe与Phe-MMIPs有3个作用位点,Ala与Ala-MMIPs之间有2个作用位点,因此吸附能力前者大于后者。     

乳状液膜法分离氨基酸的动力学

探讨了含载体P2 0 4 (磷酸二异辛酯 )的液膜体系用于苯丙氨酸促进运输的动力学行为 .采用液滴法装置 ,控制实验条件 ,测定了内相氢离子浓度随时间的变化 ,适用于有机相界面的化学反应对溶质传递的影响 ,并将计算的结果同实验相比较 ,建立了水相 -有机相界面化学反应对溶质传质具有决定作用时的传质模型     

Molecular dynamics simulations of the adsorption of amino acids on the hydroxyapatite {100}-water interface

The understanding of interfaces and interaction of organic molecules and inorganic materials are the important issues in biomineralization. Experimentally, it has been found that amino acids (AA) can regulate the morphology of hydroxyapatite (HAP) crystals significantly. In this study, molecular dynamics simulation is employed to investigate the detailed adsorption behavior of polar, ionic, and hydrophobic AA on the {100} face of HAP at the atomic level. The results indicate that various AA are adsorbed on the HAP crystal surface mainly by amino and carboxylate groups at the specific sites. Multiple interaction points are found for polar and ionic AA. The adsorbed AA molecules occupy the Ca and P sites of the HAP surfaces which may inhibit and regulate the HAP growth. The adsorbed amino acid layer can also change the interfacial hydration layer and influence the transportation of ions in and out of HAP, which may be another strategy of biological control in biomineralization.     

生物降解氨基酸衍生聚合物的研究进展

氨基酸衍生聚合物具有良好的生物相容性和生物活性,且降解产物无毒,是一种非常理想的生物材料,可在不同的生物医用领域发挥作用.本文介绍了可降解生物材料的发展历程,比较了各类材料的优劣,详细介绍了拟聚氨基酸生物材料的合成、性质以及国内外研究现状.     

乳状液膜提取氨基酸的工艺状况

比较详细地介绍了国外乳状液膜提取氨基酸的工艺状态,其种类包括苯丙氨酸、色氨酸、赖氨酸、亮氨酸、缬氨酸等,并提出了有关该项工艺的几点看法．     

The influence of pH,contact time,ionic strength,temperature, and fullerene on the adsorption of Cu(II) onto magnetic multi-walled carbon nanotubes

The influences of pH, contact time, absorbent dose, temperature and C₆₀(C(COOH)₂)_n on Cu(II) adsorption onto the magnetic multi-walled carbon nanotubes (MMWCNTs) were studied by batch technique. The dynamic process showed that the adsorption of Cu(II) onto MMWCNTs matched well with the pseudo-second-order kinetics model. The adsorption of Cu(II) onto MMWCNTs was dependent on pH values significantly, the adsorption percentage increased observably at pH 5.0–7.0, and then maintained a steady state with pH increased. Through simulating the adsorption isotherms by Langmuir, Freundlich and Dubini-Radushkevich models, respectively, it could be seen that the adsorption pattern of Cu(II) onto MMWCNTs was mainly surface complexation. The presence of C₆₀(C(COOH)₂)_n could enhance the adsorption content of Cu(II) onto MMWCNTs at low pH, but restrained that at higher pH.     

Fabrication of capped gold nanoparticles by using various amino acids

The production of gold nanoparticles (GNPs) by amino acid is one of the most attractive and interesting subjects in nanobiotechnology. In this study, amino acids have been utilised as a reducing agent and also an agent for capping GNPs. The GNPs were prepared using a reduction solution containing gold cations with optimum concentration of gold salt (5?mM), and also functionalised by glutamic acid, phenylalanine and tryptophan with optimum concentration of amino acids (25?mM). The optimum condition of gold solution and amino acids were achieved by ultraviolet–visible spectroscopy. The size of nanoparticles was obtained 5–20, 10–20 and 20–30?nm, respectively, by transmission electron microscopy and dynamic light scattering techniques. The results obtained from experimental and quantum calculations confirm that amino acids have strong bond while they have anion binding. Moreover, the free carboxylic groups of capped GNPs are one of the suitable and capable beads for binding biological agents. As a result, the medical applications of amino acids and proteins can be used as a practical method due to the strong interaction of peripheral amine groups with nanoparticles.     

液相色谱串联质谱法测定烟草中的游离氨基酸

建立液相色谱串联质谱法测定烟草中20种游离氨基酸的方法。烟草样品经0.1%的盐酸溶液超声萃取并离心后,直接进样测定。色谱柱采用XTerra MS C18(50mm×2.1mm×2.5μm),0.1%甲酸溶液和乙腈为流动相。结果表明:20种氨基酸的检出限为0.001～0.011μg/mL,标准曲线的拟合度均大于0.999,回收率在86.4%～105.9%之间。该方法操作简单,灵敏度高,适用于烟草中游离氨基酸的检测。     

Synthesis of bipyramidal gold nanoparticle-[C60]fullerene nanowhisker composites and catalytic reduction of 4-nitrophenol

The seed solution was prepared by dissolving hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), trisodium citrate dihydrate (C₆H₅Na₃O₇·2H₂O), and sodium borohydride (NaBH₄) in distilled water. The resulting reddish-purple seed solution was stirred for 3 h at room temperature. The growth solution was prepared by mixing hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), cetyltrimethylammonium bromide (CTAB, (C₁₆H₃₃)N(CH₃)₃Br), silver nitrate (AgNO₃), hydrochloric acid (HCl), and ascorbic acid (C₆H₈O₆) in distilled water. Subsequently, 100 μL of this seed solution was transferred into 10 mL of the growth solution. The mixed solution was maintained at 30 °C for 3 h to obtain a solution of bipyramidal gold nanoparticles. The bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were synthesized by applying the liquid-liquid interfacial precipitation (LLIP) method to a saturated solution of C₆₀ in toluene, the solution of bipyramidal gold nanoparticles, and isopropyl alcohol. The prepared bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of these composites was confirmed in the reduction of 4-nitrophenol by UV-Vis spectroscopy.     

磷酸三丁酯修饰Ti纳米晶须应用于吸附铀酰离子

采用纳米金红石型TiO₂为Ti源, 水热法合成了Ti纳米晶须, 将其表面负载磷酸三丁酯(TBP)制备出修饰Ti纳米晶须。用SEM、 TEM及傅里叶红外光谱仪对Ti纳米晶须及修饰Ti纳米晶须的形貌和结构进行表征, 分别研究了两种材料对铀离子的吸附性能, 考察了修饰Ti纳米晶须吸附铀的动力学及等温吸附模型。电镜表征结果表明, 水热温度为160 ℃成功合成出Ti纳米晶须, 其粒径范围为80~100 nm。吸附铀研究结果表明, 在3 mol/L NO-₃介质中修饰Ti纳米晶须表现出较高的吸附性能, 修饰Ti纳米晶须对铀的吸附动力学模型符合准二级动力学, 吸附等温线符合Langmuir和Freundlich等温吸附模型。将修饰Ti纳米晶须用于自来水中低浓度铀的回收, 结果较好。      

Catalytic activity of hybrid platinum nanoparticle-[C60]fullerene nanowhisker composites for 4-nitrophenol reduction

Abstract

Composites comprising platinum nanoparticles loaded on [C₆₀]fullerene nanowhiskers were prepared by a liquid-liquid interfacial precipitation method. The synthesized platinum nanoparticle-[C₆₀]fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of the platinum nanoparticle-[C₆₀]fullerene nanowhisker composites was confirmed for the reduction of 4-nitrophenol by UV–vis spectroscopy. The reduction of 4-nitrophenol catalyzed by the platinum nanoparticle-[C₆₀]fullerene nanowhisker composites followed the pseudo-first-order reaction rate law.     

酸改性活性炭对EDTA废水的吸附

采用盐酸和硝酸对活性炭进行改性处理获得酸改性活性炭,并将其用于处理EDTA废水。考察改性条件(如酸的种类、改性时间和酸的浓度)、振荡速度和酸改性活性炭投加量等因素对吸附效果的影响,同时采用吸附等温模型和吸附动力学模型进行拟合分析。结果表明,采用1.0mol/L盐酸改性12h所获得的改性活性炭吸附效果最好。在EDTA初始浓度为300mg/L、溶液体积为50mL、温度为20℃、振荡速度为200r/min,改性活性炭投加量为0.2g时,48h后吸附量为47.1 mg/g,吸附率为62.8%;而当改性活性炭投加量增加到2.0g时,吸附率达到93.8%。改性活性炭对EDTA的吸附很好地符合Langmuir吸附等温模型(0.9963),其吸附动力学行为可用Bangham动力学方程和准二级动力学方程来描述。     

烟草制丝过程中游离氨基酸的变化研究

超声波水解提取烟叶中的游离氨基酸、AccQ-2A氨基酸衍生化试剂衍生化、反相高效液相色谱法测定卷烟制丝过程中松片回潮、润叶加料、烘丝三个工序前后烟丝中的游离氨基酸。结果表明:制丝加工制丝过程中A、B两个不同牌号的16种游离氨基酸总量增加,幅度分别达32.5%和22.1%。     

Mg/Al水滑石对腐殖酸的去除性能研究

采用共沉淀法制备了 Mg/Al 水滑石,并在不同温度下煅烧。探究了煅烧温度、材料投加量、pH 值、腐殖酸初始浓度对水滑石去除腐殖酸的影响。结果表明,当金属物质的量比为3的 Mg/Al 水滑石投加量为0.5 g/L, pH 值为8.5,温度为25℃时,水滑石对10 mg/L 的腐殖酸的去除率能达到96.64%,此时,水滑石的饱和吸附量为19.33 mg/g。Mg/Al 水滑石经3次再生后,对腐殖酸的去除率仍然高达95%以上,表明 Mg/Al 水滑石的可重用性好。     

C60-like boron carbide and carbon nitride fullerenes: Stability and electronic properties obtained by DFT methods

The structural stability, electronic and magnetic properties of novel boron carbide and carbon nitride fullerenes, of chemical compositions: C₃₆B₂₄ and C₂₄B₃₆ (CBF) and C₃₆N₂₄ and C₂₄N₃₆ (CNF), rich in carbon, boron and nitrogen atoms, were determined by means of density functional theory based-methods. Calculations were done using a exchange–correlation functional developed by Heyd-Scuseria-Ernzerhof, within the generalized gradient approximation (HSEh1PBE-GGA) in concert with 6–311G(d,p) basis sets. The DFT simulation results for the neutrals, cations and anions reveal structural stability for the four chosen compositions. Several spin multiplicities were determined for each system. Although distorted, the located low-lying states preserve the basic fullerene features. In the addressed compositions, the lowest energy structures occur for the anions, which behave as semi-metallic and magnetic nanomaterials. Indeed, they have HOMO-LUMO gaps of 0.55, 0.66, 0.34 and 2.17 eV and 3.0, 5.0, 1.0 and 3.0 magneton bohrs, respectively. These CB and CN hybrid fullerenes show high polarity and low-chemical reactivity. Additionally, they have low-work functions, which is crucial for the design of electronic devices.     

氨基酸/羟基磷灰石复合材料的制备与表征及其在酸蚀牛牙釉质体外再矿化中的应用

在不同浓度丝氨酸(Ser),天冬氨酸(Asp)和谷氨酸(Glu)的组合下制备氨基酸/羟基磷灰石(AA/HAP)复合材料。通过红外光谱仪、X射线衍射仪和透射电镜对复合材料进行表征,评估复合材料对酸蚀牛牙釉质体外再矿化的效果。结果表明:氨基酸(AA)会干扰羟基磷灰石(HAP)晶面的生长,使HAP的溶解度增加和晶体结构有序性降低。X射线衍射图及透射电镜图的结果显示,AA对HAP的[100]晶向具有显著的抑制作用,且与不含AA的HAP相比,AA修饰的HAP复合材料具有细化的晶粒尺寸。通过CCK-8法评估了材料的细胞毒性,结果表明AA/HAP复合材料的相对细胞活性优于HAP。场发射扫描电镜图表明不含AA的HAP材料和两组不同浓度AA改性HAP材料均可修复酸蚀牛牙釉质的表面龋损。而在Ser,Asp和Glu均为10 mmol·L-1条件下制备的AA/HAP可在牛牙釉质的深层再矿化中生成厚度约为22μm的致密再矿化层,并获得了最佳的表面显微硬度恢复效果。     

Reactions of microcrystalline fullerene C60 with amino and aza macrocyclic ligands under solvent-free conditions

We evaluated the reactivity under solvent-free conditions of 2-aminomethyl-15-crown-5 (AM15C5), 2-aminomethyl-18-crown-6 (AM18C6), 1,4,8,12-tetraazacyclopentadecane (TACPD) and rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (tet b) with microcrystalline fullerene C₆₀. The reactions of nucleophilic addition were carried out at temperatures of about 160°C for 5 h in the case of crown ethers and TACPD, and at 180–190°C for 24 h in the case of tet b. Characterization of the products obtained was performed by using Fourier-transform infrared (FTIR) and Raman spectroscopy, laser desorption/ionization time-of-flight (LDI-TOF) mass spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). To provide an additional insight into the reactivity of macrocyclic compounds with C₆₀ molecules, we employed theoretical calculations in the frame of density functional theory (DFT). According to the results of SEM imaging, macrocyclic reagents are generally unable to deeply penetrate into the bulk of fullerene microcrystals (with a possible exception of TACPD). According to TGA measurements, the reaction efficiency is very low for tet b, whereas the average content of organic fraction in C₆₀-AM15C5 and C₆₀-AM18C6 reaches about 29%, and in C₆₀-TACPD, almost 40%. According to LDI-TOF mass spectral analysis, the products of TACPD, tet b and AM15C5 reactions with fullerene have oligomeric or polymeric structure. By using DFT theoretical calculations, the latter observation was explained by enhanced reactivity of secondary amino groups toward nucleophilic addition onto fullerene cage.