Nafion/Au溶胶自组装微铂传感器的研究及其在心肌细胞中NO水平测定中的应用

制备了一种新型的Nafion/Au溶胶修饰微铂传感器(Au溶胶颗粒的直径为7～14nm),并将该传感器应用于心肌细胞中NO水平的研究.实验结果表明,自组装制备的Nafion/Au溶胶修饰微传感器对NO有较高的灵敏度和良好的选择性,在1.0×10^-7～4.0×10^-5mol/L浓度范围内,NO的催化氧化电流与其浓度呈良好线性关系,检测限为5.0×10^-8mol/L.探讨了该修饰微传感器对NO的催化机理,研究了在L-精氨酸和乙酰胆碱刺激下心肌细胞内的NO释放.     

蔗糖/精氨酸体系中碳酸钙结晶的仿生合成

该文以更加接近生物矿化的方法研究了蔗糖/精氨酸体系对碳酸钙晶体取向、形貌和晶型的控制作用.XRD 分析表明,在蔗糖/L-精氨酸混合体系中合成的晶体主要为碳酸钙的球霰石晶型及少量的方解石型,在单独的蔗糖或L-精氨酸溶液中基本是球霰石晶型.SEM分析表明,蔗糖和L-精氨酸均可诱导形成特殊形貌的碳酸钙.实验结果表明,蔗糖/精...     

聚L-精氨酸/纳米金修饰电极测定多巴胺

利用多电位脉冲沉积法制备纳米金修饰电极(AuNPs/GCE),再将L-精氨酸电聚合在AuNPs/GCE表面,制备出一种新型的聚L-精氨酸/AuNPs/GCE。采用原子力显微镜对上述电极进行了表征,并研究了多巴胺在其上的电化学行为。结果表明:在pH 5.7的磷酸盐缓冲溶液中,聚L-精氨酸/AuNPs/GCE对多巴胺的氧化有良好的电催化作用,多巴胺的氧化还原反应是受吸附控制的准可逆过程。多巴胺的浓度在8.0×10-7~1.0×10-4 mol·L-1范围内与其氧化峰电流呈线性关系,检出限(3S/N)为1.0×10-7 mol·L-1。加标回收率在96.5%~104%之间。对3.0×10-5 mol·L-1多巴胺溶液连续测定7次,峰电流的相对标准偏差为2.6%。     

罗丹明B聚合物修饰单壁碳纳米管薄膜电极的制备、表征及一氧化氮活体分析应用

以单壁碳纳米管作为电极材料,基于减压过滤和电聚合方法制备了一种薄膜型一氧化氮(NO)电化学传感器。扫描电镜、红外光谱和电化学交流阻抗表征表明,减压过滤可以制备出导电性好、电分析性能优良的薄膜电极,而罗丹明B能通过电聚合在其表面形成高比表面的纳米敏感结构。这种薄膜型电化学传感器对NO具有灵敏的电化学响应,其安培氧化电流与NO浓度在7.2×10-8~2.5×10-5mol/L范围内呈良好的线性关系,检出限(S/N=3)达3.6×10-8mol/L。将该传感器紧贴在麻醉豚鼠的肝脏表面,成功实现了肝组织细胞在L-精氨酸刺激下NO释放的实时监测。     

LC-APCI-MS法同时分离测定人体血浆中的精氨酸及二甲基精氨酸的含量

建立了简单、灵敏和快速分离测定人体血浆中L-精氨酸(ARG)、不对称二甲基精氨酸(ADMA)和对称二甲基精氨酸(SDMA)的等度高效液相色谱-质谱联用方法.采用选择性离子检测(SIM)和大气压化学电离离子化(APCI),L-高精氨酸作内标,整个方法测定时间在5min以内.ARG,ADMA和SDMA的分析限均为0.2μmol/L,日间和日内测定的精密度分别为2.9%～6.7%和2.1%～5.2%,标准加入回收率为94.0%～105.0%.采用上述方法测定人体血浆中的精氨酸及二甲基精氨酸的含量,结果令人满意.     

GC/MS-衍生化法分析无机阴离子

研究了应用电子轰击电离源气相色谱/质谱法测定水中无机阴离子NO3-和SCN-。采用五氟苄基溴首先将NO3-和SCN-衍生化生成可挥发性化合物,然后用GC/MS法进行测定,检出限为10mg·L-1。应用该方法对水中硝酸根和硫氰根离子进行测定,取得满意的结果。     

NMR研究水溶液中L-精氨酸与磷酸腺苷的相互作用及其构象变化

利用核磁共振(NMR)方法,研究了水溶液中L-精氨酸分别与一磷酸腺苷、三磷酸腺苷的相互作用及其构象变化.通过测定L-精氨酸分别与一磷酸腺苷、三磷酸腺苷混合后体系的1H、13C NMR,对混合前后L-精氨酸1H及13C化学位移变化情况进行了分析,发现L-精氨酸与一磷酸腺苷、三磷酸腺苷存在氢键和静电作用,并且这种相互作用会导致L-精氨酸构象产生变化,即由作用之前的伸展型转变为作用后的弯曲型.     

基于氧化锌纳米棒的乙酰胆碱酯酶生物传感器用于辛硫磷农药测定

以喷金的聚碳酸酯模板为工作电极,采用电沉积法从氯化锌和氯化钾溶液中制得氧化锌纳米棒.将沉积了氧化锌纳米棒的模板固定在打磨后的玻碳电极表面,并将模板溶解.再通过在氧化锌纳米棒修饰电极的表面直接固定乙酰胆碱酯酶,制备出乙酰胆碱酯酶生物传感器.自然晾干后,所得乙酰胆碱酯争氧化锌生物传感器用于辛硫磷农药的测定.试验结果表明:在含有0.5 mmol·L-1的巯基乙酰胆碱的PH 7.38磷酸盐缓冲溶液中,乙酰胆碱酯酶-氧化锌修饰电极的氧化峰电流显著提高,而再向其中加入酶抑制剂辛硫磷后,电流明显减小,在此基础上提出了一种高灵敏度的测定辛硫磷农药的方法.在优化的条件下,辛硫磷浓度在9.85 × 10-6～4.95×10-4mol·L-1之间,其浓度的对数与抑制率呈线性关系,检出限(3S/N)为5.99×10-6mol·L-1.     

无氧/低氧环境中zigzag型焦炭N的迁移转化特性

采用量子化学方法探究了还原区高浓度NO存在下zigzag结构焦炭氮中N的迁移转化规律，并通过构建含羟基焦炭N模型，从分子层面对氧存在下焦炭N的转化特性进行了系统的理论计算。结果表明，还原区NO的存在会与焦炭中的N结合为N₂释放；并且氧的存在增强了焦炭表面化学活性，进一步促进了焦炭中N的析出。还原区氧和NO的共存使得焦炭中N的释放与C的燃烧同时发生，表现为NO与焦炭中N结合为N₂的同时，伴随有氧将焦炭中C氧化成CO₂或CO。动力学计算C燃烧产物的限速步速率常数发现，低温低氧条件下C更容易氧化生成CO；随着温度的升高，CO₂生成速率明显增大，高温更利于CO₂的生成。     

化学-生物法制备D-精氨酸和L-瓜氨酸

在水溶液中以水杨醛为催化剂,L-精氨酸可以快速消旋为DL-精氨酸．后以DL-精氨酸为底物,利用粪链球菌（Streptococcus faecalis）精氨酸脱亚胺酶对L-精氨酸的专一脱亚胺作用,同时制备D精氨酸和L-瓜氨酸,分别以92．3％,94．2％的产率获得光学纯的D-精氨酸和L-瓜氨酸．     

Measurement of nitric oxide released in the rat heart with an amperometric microsensor

Nitric oxide (NO) plays an important role in various physiological processes, acting either as an intra- and intercellular messenger or as a toxic agent. The detection and quantification of NO have been accomplished by a variety of methodologies. In the present study, real-time production of NO in the rat heart was continuously measured by using a novel copper-platinum microparticle-modified NO electrochemical microsensor. The linearity range of the microsensor is between 8.0 x 10(-8) and 4.8 x 10(-6) mol L-1 and the detection limit is 3.0 x 10(-8) mol L-1. NO release from the rat heart stimulated by the agonists L-arginine and acetylcholine was observed, and the responses were decreased by the NO synthase inhibitor L-N omega-nitroarginine. In addition, the effect of sodium nitroprusside (SNP), a NO donor, was also studied. SNP increases the concentration of NO in the rat heart. The experiments showed that electrochemical detection is suitable for detecting and quantifying NO in biological systems.     

Exogenous donors of nitric oxide (a chemical aspect)

The review considers problems related to the formation, in the living organism, of nitric oxide, a versatile and vitally important regulator of cell metabolism. The pathways of formation of endogenous nitric oxide from L-arginine are discussed and the main approaches to increasing the NO concentration by introducing various types of exogenous nitric oxide donors into the organism and chemical and biological characteristics of these donors are considered. Primary attention is devoted to the known drugs that were shown to release NO under hydrolytic, oxidative, or reductive conditions. The solution of problems related to the elucidation of the mechanisms of drug action requires that the formation of nitric oxide be taken into account.     

Changes of plasma L-arginine levels in spontaneously hypertensive rats under induced hypotension

Nicardipine, a dihydropyridine type calcium channel blocker, was infused at two flow-rates into spontaneously hypertensive (SH) and control normotensive Wistar-Kyoto (WKY) rats (young, 6-week-old and adult, 23-week-old, n = 5) under pentobarbital anesthesia, to cause hypotension. Mean arterial blood pressure and the concentrations of plasma amino acids and norepinephrine (NE) were measured before infusion and at each step of the infusion. The reduction in blood pressure caused by nicardipine induced a decrease in plasma L-arginine concentration in both young and adult SH rats, this effect being larger in adult rats. There was no significant change in plasma levels of L-arginine in age-matched WKY rats. The concentration of other amino acids did not change in both rat strains. On the contrary, there was an increase in plasma NE concentration in both SH and WKY rats after infusion with nicardipine. Plasma L-arginine concentration showed a good inverse correlation with the logarithm of plasma NE concentration in SH and WKY rats and the correlation was expressed as Y = -alpha log(X) + m (Y, plasma L-arginine concentration (nmol/mL); X, plasma NE concentration (pmol/mL); alpha, a slope; and m, an intercept). alpha, 43.0 and 4.35 for 23-week-old SH and WKY rats, respectively, and 17.0 and 4.0 for 6-week-old SH and WKY rats, respectively. The present data together with previous data suggest a direct noradrenergic stimulation of the synthesis of nitric oxide (NO) from L-arginine. The findings also indicate an impairment of the L-arginine metabolism or pools in SH rats compared with WKY rats. The deficiency of L-arginine increases with the age of SH rats and could be related to the development and maintenance of hypertension due to inefficient production of NO.     

Nitric oxide modulates tumor cell death induced by photodynamic therapy through a cGMP-dependent mechanism

Photodynamic therapy (PDT) of cancer is a very promising technique based on the formation of singlet oxygen induced by a sensitizer after irradiation with visible light. The stimulation of tumor growth by nitric oxide (NO) was reported recently, and NO was shown to have a protective effect against PDT-induced tumor death. We investigated a putative direct effect of NO on tumor cell death induced by PDT, using the human lymphoblastoid CCRF-CEM cells and bisulfonated aluminum phthalocyanine (AlPcS2) as a sensitizer. Cells were incubated with AlPcS2 in the presence or absence of NO donors ((Z)-1-[(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate, hydroxylamine and S-nitroso-N-acetylpenicillamine) or L-arginine. Under these conditions, in the absence of NO donors or L-arginine the cells died rapidly by apoptosis upon photosensitization. In the presence of NO donors or L-arginine, apoptotic cell death after photosensitization was significantly decreased. Modulation of cell death by NO was not due to S-nitrosylation of caspases and occurred at the level or upstream of caspase-9 processing. The protective effect of NO was reversed by incubating the cells with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of guanylyl cyclase, or with KT5823, an inhibitor of protein kinase G (PKG). Incubation with 8-bromo-cyclic guanosine monophosphate, a membrane permeable cyclic guanosine monophosphate analog, also decreased cell death induced by PDT. Although the protective effect of NO against apoptotic cell death in several models has been attributed to an increase in the expression of heme oxygenase-1, heat shock protein 70 or Bcl-2, this was not the case under our experimental conditions. These results show that NO decreases the extent of apoptotic cell death after PDT treatment through a PKG-dependent mechanism, upstream or at the level of caspase activation.     

Probing heme coordination states of inducible nitric oxide synthase with a ReI(imidazole-alkyl-nitroarginine) sensitizer-wire

Mammalian inducible nitric oxide synthase (iNOS) catalyzes the production of l-citrulline and nitric oxide (NO) from L-arginine and O2. The Soret peak in the spectrum of the iNOS heme domain (iNOSoxy) shifts from 423 to 390 nm upon addition of a sensitizer-wire, [ReI-imidazole-(CH2)8-nitroarginine]+, or [ReC8argNO2]+, owing to partial displacement of the water ligand in the active site. From analysis of competitive binding experiments with imidazole, the dissociation constant (Kd) for [ReC8argNO2]+-iNOSoxy was determined to be 3.0+/-0.1 microM, confirming that the sensitizer-wire binds with higher affinity than both L-arginine (Kd=22+/-5 microM) and imidazole (Kd=14+/-3 microM). Laser excitation (355 nm) of [ReC8argNO2]+-iNOSoxy triggers electron transfer to the active site of the enzyme, producing a ferroheme in less than approximately 1 micros.     

富氧条件下Co/MOR 催化剂上甲烷选择催化还原NO

采用浸渍法制备了一系列用于甲烷选择催化还原(CH₄-SCR)氮氧化物的Co/MOR催化剂。采用XRD、BET、TG-MS、H₂-TPR、NH₃-TPD和NO-TPD等手段对催化剂进行表征,并对其在甲烷选择催化还原氮氧化物反应中的活性进行评价。结果表明,钴物种以Co₃O₄尖晶石形态存在于Co/MOR催化剂中;与MOR载体相比,引入钴物种后,催化剂的酸性、氧化还原能力和对NO的吸脱附能力均发生了变化。在甲烷选择催化还原氮氧化物反应中,Co/MOR的催化活性与其氧化还原性能和对NO的吸脱附性能直接相关;其中,Co负载量为10%的Co(10)/MOR催化剂的CH₄-SCR脱硝活性最好,在330℃下NO的转化率达54.2%。     

Amperometric determination of nitric oxide derived from pulmonary artery endothelial cells immobilized in a microchip channel

A simple method for immobilizing a confluent layer of bovine pulmonary artery endothelial cells (bPAECs) in microchip-based channels is described. The microchips are prepared from poly(dimethylsiloxane) and have channel dimensions that approximate resistance vessels in vivo. The reversibly sealed channels were coated with fibronectin (100 microg ml(-1)) by aspiration. The bPAECs, which were introduced in the same manner, became attached to the fibronectin coating in about 2 h. The microchip could then be resealed over a micromolded carbon ink electrode (24 microm width x 6 microm height). Coating the carbon microelectrode with a 0.05% Nafion solution selectively blocked nitrite (10 microM) from being transported to the electrode surface while nitric oxide (NO, 10 microM) was amperometrically measured. Upon stimulation with adenosine triphosphate (ATP, 100 microM) the immobilized bPAECs produced and released micromolar amounts of NO. This NO production was effectively inhibited when the immobilized cells were incubated with L-nitro-arginine methyl ester (L-NAME), a competitive inhibitor for nitric oxide synthase. Moreover, once the immobilized bPAECs were no longer able to produce NO, incubation with L-arginine allowed for further ATP-stimulated NO production.     

Amperometric Nitric Oxide Sensor Based on Poly(Thionine)/Nafion‐Modified Electrode and Its Application in Monitoring Nitric Oxide Release from Rat Kidney

Abstract

A novel amperometric nitric oxide (NO) sensor based on a glassy carbon electrode modified with thionine and Nafion films has been developed. The oxidation peak current of NO increased significantly at the poly(thionine)/Nafion‐modified glassy carbon electrode (GCE), which can be used for the detection of NO. The oxidation peak current was linear with the concentration of nitric oxide over the range from 3.6×10^?7 to 6.8×10^?5 mol · L^?1, and the detection limit was 7.2×10^?8 mol · L^?1. This nitric oxide sensor showed high selectivity to nitric oxide determination, and some potential interference could be eliminated effectively. The nitric oxide sensor has been applied to monitor NO release from rat kidney stimulated by L‐arginine. The results indicated the applicability of the NO sensor to biomedical samples.