Cytophotometric determination of non-heme iron content in hepatocytes. I. Effect of cell separation techniques on iron content

To study conditions of the preservation of non-heme iron (3+) in hepatocytes, experiments were performed on rats fed with the diet supplemented with 2% carbonyl iron. The cells were isolated by a collagenase method (an enzymatic method) or by a treatment of the tissue with the phosphate buffer (a nonenzymatic method). When using the enzymatic method, the main steps of obtaining preparations-smears were analysed: perfusion of the organ, subsequent washing out of the cells from collagenase, mounting of the smear on the object glass. When using the non-enzymatic method, such steps were an incubation of the tissue pieces in the isolation solution and mounting of the smears. It has been found that the enzymatic isolation method results in practically no losses of iron from the cells if the perfusion lasts for 20 min. A slight loss (10-12%) of the Perls'-stained iron can occur during the initial 30 min of the washing out of the cells from collagenase. This step is not accompanied by any morphological changes of the cells; their viability, according to the trypan test, is 70-87%. The iron release from the cells rises with decrease in the viability of hepatocytes. It has been shown that the greatest losses of iron can occur at the mounting step when the cells are submitted to a substantial mechanical effect. When the nonenzymatic method is applied, the incubation of the cells in the phosphate buffer for up to 2 hr causes no marked morphological changes revealed in the light microscope; however, the cell viability is very low (about 1%). The preservation of iron in the cells is lower when using the nonenzymatic than the enzymatic method. Thus, for cytophotometric determinations of the iron content in hepatocytes, the collagenase method of isolation of cells is recommended.     

EPR determination of low molecular weight iron content applied to whole rat hepatocytes

Electron paramagnetic resonance (EPR) has been described as suitable for the evaluation of low molecular weight (LMW) iron in liver homogenates after chelation by desferrioxamine. LMW iron is a highly toxic iron species incriminated in free radical production. The first aim of the study was to evaluate the conditions of EPR application for LMW iron content determination in whole rat hepatocytes. For this purpose, LMW iron was simultaneously quantified by EPR and by atomic absorption spectrometry, EPR determination of LMW iron needed a preincubation of hepatocyte cultures with the iron chelator for at least on hr. Deferiprone as LMW iron chelator was revealed to be more suited than desferrioxamine. Secondly, we showed the applicability of this methods for evaluating the prooxidant status during an oxidative stress. As an example, oxidative stress induced by ethanol in hepatocytes was studied during inflammatory circumstances, well-known to lead to nitric oxide production. In hepatocyte cultures supplemented with ethanol, an evaluation of LMW iron content was observed in cells. But when nitric oxide donors or a supplementation constituted of lipopolysaccharide and gamma-interferon, able to induce nitric oxide synthase, were added, LMW iron content decreased. Thus EPR determination of LMW iron content in whole hepatocytes could give some insight about the mechanism of induction or inhibition of a oxidative stress.     

样品制备对褐铁矿总铁含量测定结果的影响

采用化学分析法对不同研磨时间的褐铁矿样品进行了总铁含量测定,同时采用热失重分析和X射线衍射分析方法对不同研磨时间得到不同粒度分布的褐铁矿样品进行了分析。结果表明:研磨2 min时总铁含量为57.87%,进一步间歇式研磨3~12 min总铁含量从58.00%提高到58.43%,即褐铁矿样品研磨时间越长,样品温度升的越高,样品中的化合水失去的越多,导致样品中总铁含量相对提高。所以规定当制备褐铁矿样品时,应采用研磨过程不产生过多热量而明显改变其化学成分的工艺,即研磨样品至-160μm为宜,不需研磨至-100μm,更不宜1次性连续研磨至-100μm。     

影响铁矿石中铁含量测定的因素分析和校正

在国际贸易中 ,铁矿石的总价常以铁的含量×固定费率来计算 ,低于规定的最低含量时则以双倍扣款 ,即 :2×固定费率× (规定的最低含量 -实测量 )。因此铁含量的高低是贸易双方争议的主要焦点。而在重铬酸钾滴定法测定铁含量时存在着温度、指示剂和空白溶液等影响 ,标准[1 ] 中仅对空白溶液进行了校正 ,而未涉及对温度和指示剂的校正。在氧化还原过程中 ,指示剂也参与了反应 ,当终点时并不能恢复到原来状态 ,实际上起了部分还原剂的作用 ;此外 ,检验过程中温度的变化 ,引起重铬酸钾溶液用量的变化 ,都对实验结果带来影响 ,存在较大的分析误差…     

铁矿石中磁性铁的测定方法研究

研究了应用WFC-3型磁选仪测定铁矿石中磁性铁的分析条件。利用超声波粉碎办法进行试样预处理,用本法和人工磁选法分别测定铁矿石标样中磁性铁,本法测定结果高于人工磁选法并接近于标准值,RSD小于0.5%,回收率为99.1%~100.1%。方法快速准确,操作简便,已用于铁矿石中磁性铁的日常检测,获得了满意结果。     

铁矿石中砷含量的测定国际标准研制

以铁矿石中测定砷含量的国内外技术现状、发展趋势为技术背景,介绍了我国开展铁矿石中砷含量的测定国际标准研制的情况。     

锌铁合金钢板镀层中铁含量的检测方法探讨

采用标准化学法和两种X射线荧光法对锌铁合金钢板镀层中的铁含量进行了测定研究.试验结果表明,对于锌铁合金样板镀层中铁含量的测定,标准化学法是准确性最佳的方法,但是该方法检测效率低,不适用于生产质控检测.X射线荧光法中的基本参数法和经验系数法均可用于锌铁合金钢板镀层中铁含量的生产质控检测,检测重复性分别可达0.2％和0.4％,均优于原子吸收法的0.6％.但是,这两种X射线荧光法均有各自的使用限制,对于不同机组生产的锌铁合金钢板的检测准确性较标准化学法差,需谨慎限制使用.     

Study on determination method of iron content in galvanized coating of zinc-iron alloy

The iron content in the galvanized coating of zinc-iron alloy was determined by atomic absorption spectrometry and two kinds of X-ray fluorescence(XRF) methods.Results show that the chemical method exhibits the highest accuracy.However, this method presents low detection efficiency and is thus unsuitable for production quality control.Fundamental parameter and empirical coefficient methods in XRF can be used for the quality control of iron content in the galvanized coating of zinc-iron alloys.Th...     

The 2-His-1-carboxylate facial triad--an emerging structural motif in mononuclear non-heme iron(II) enzymes

PURPOSE: To determine in-line pressures generated in small-bore central venous catheters during power injection of computed tomographic (CT) contrast media. MATERIALS AND METHODS: Five 3.0-7.0-F central venous catheters for pediatric patients were tested at full and half lengths in vitro. In-line pressures were measured during power injection of three contrast media. Rates of injection were increased in steps from 0.1 to 5.0 mL/sec or until a peak pressure of 100 psi (700 kPa) was achieved. The maximum tolerated flow rate was determined with reference to the manufacturer's suggested operating pressure limit for each catheter. RESULTS: At full length, the maximum tolerated flow rates were as follows: 2-3 mL/sec for the large lumen and 1-1.4 mL/sec for the small lumen of the 7.0-F double-lumen catheter; 0.2-0.4 and 0.8-1.2 mL/sec for the 3.0- and 4.0-F peripherally inserted central catheters, respectively; 0.7-1.2 mL/sec for the 6.6-F catheter; and only 0.2 mL/sec for the 4.2-F catheter, which ruptured during testing at higher flow rates. CONCLUSION: Flow rates were documented at which certain small-bore central venous catheters should tolerate power injection of CT contrast media with peak pressures remaining below the manufacturer's recommended operating pressure limits. These data may serve as a guide for clinical use.     

Bicarbonate binding to the non-heme iron of photosystem II investigated by Fourier transform infrared difference spectroscopy and 13C-labeled bicarbonate

The binding site of the non-heme iron of photosystem II (PS II) is investigated by light-induced Fourier tranform infrared (FTIR) difference spectroscopy on Tris-washed membranes. The non-heme iron is oxidized (Fe3+) in the dark with ferricyanide and reduced (Fe2+) after light-induced charge separation by electron transfer from the semiquinone anion QA-. EPR experiments and IR modes of ferri- and ferrocyanide show that the electron donor side of PS II is reduced in less than 2 s after a flash and that ferricyanide reoxidizes the non-heme iron with a half-time of approximately 20 s. Recording FTIR spectra before and 2 s after flash illumination thus results in the Fe2+/Fe3+ difference spectrum. This spectrum shows band shifts and intensity changes of IR modes from ligands and neighboring residues of the non-heme iron. The IR modes of bicarbonate are revealed by comparison of Fe2+/Fe3+ spectra obtained on PS II membranes with 12C or 13C isotope labeled bicarbonate in H2O and in 2H2O. The nu as(CO) and nu s(CO) modes of bicarbonate in the Fe2+ state are assigned at 1530 +/- 10 and 1338 cm-1, respectively. The low frequency of the nu as(CO) mode is taken as experimental evidence that bicarbonate is a ligand of the non-heme iron. Furthermore, the small frequency difference (192 cm-1) between the nu as(CO) and nu s(CO) modes as compared to even hydrogen-bonded ionic bicarbonate strongly indicates that bicarbonate is a bidentate ligand of the non-heme iron in PS II. Upon iron oxidation, the bicarbonate modes are largely affected. The nu s(CO) mode is assigned at 1228 cm-1, while the nu as(CO) mode is tentatively assigned at 1658 +/- 20 cm-1. The strong up- and downshifts of the nu as and nu s(CO) modes of bicarbonate upon iron oxidation results in a frequency difference of 430 +/- 20 cm-1 that is not only explained by the increased charge on the iron but indicates that bicarbonate is a monodentate ligand of the oxidized iron. The sensitivity of the nu s(CO) mode of bicarbonate to 1H/2H exchange in both the Fe2+ and Fe3+ states and the presence in the Fe2+ state of a delta (COH) mode at 1258 cm-1 confirm that bicarbonate and not carbonate is the iron ligand and further exhibits hydrogen bond(s) with the protein. The 13C isotope-sensitive modes of bicarbonate are not affected by 15N labeling of the PS II membranes. 15N sensitive signals at 1111/1102 and 1094 cm-1 are assigned to side chain modes from histidine ligands of the iron. The latter signal is proposed to account for a histidine ligand that deprotonates upon iron oxidation. The involvement of protein peptide groups and side chains in the hydrogen-bond network around the iron is also discussed.     

高频燃烧红外吸收法测定铁矿石中硫

由于在采用ASTME1915-01<采用燃烧红外吸收光谱法分析金属矿石及相关原料的标准试验方法>标准[1]对铁矿石进行分析时,发现样品颜色不同硫的分析结果相差很大,为此我们进行了专门研究,发现红色与黑色的铁矿粉其结构上有所不同,所以熔样效果上就出现差异,一般的助熔剂,不能完全适应,有时会造成板流偏低,硫释放不完全,使测定结果不稳定而且偏低.     

铁水w（Si）对高炉碳排放量的影响

高炉炼铁排放CO2是钢铁行业温室气体排放的主要来源,CO2的产生与高炉内众多条件相关。应用物料平衡计算与热平衡计算,根据国内某高炉原料条件与冶炼参数,主要计算分析铁水w（Si）对焦比、碳排放量的影响,得出了定性定量的关系：在本文的计算条件下,铁水w（Si）每升高0.1%,焦比吨铁增加4.54 kg,碳排放量吨铁增加7....     

酸溶重铬酸钾容量法测定铁含量的分析与探讨

目前,铁含量的测定方法主要采用的是:酸溶或者碱熔分解试样,然后采用二氯化锡和三氯化钛作为还原剂,利用重铬酸钾作为标准溶液滴定测定铁含量的经典方法。本文在传统的重铬酸钾容量法基础之上,加以改进,经过反复多次实验,确定最佳实验反应条件,并对实验结果进行验证分析,确定改进方法的适用范围。     

Effect of phase transformation in higher iron silicide on the electrical conductivity of the multiphase system iron silicide-glass. II. Effect of structural transformation in lebeauite on the temperature dependence for composite resistivity

Annealing at the eutectoid decomposition temperature for higher iron suicide -phase is studied for its effect on the temperature dependence for resistance (T) of a composite based on cermet containing iron suicide and barium borosilicate glass. An attempt is made to distinguish the contribution of -FeSi₂ to the (T) dependence of the system on a background of the conductivity of the other phase components.Translated from Poroshkovaya Metallurgiya, No. 10, pp. 20–24, October, 1992.     

炉腹煤气中氢含量对铁矿石滴落过程的影响

利用高温熔滴炉对喷吹富氢煤气后高炉炉料的熔滴性能进行实验研究,XRD检测技术对喷吹富氢煤气后炉料的还原情况进行分析,并利用相图原理分析了不同富氢量对滴落带的影响。结果表明:喷吹富氢煤气后,矿石在进入滴落带之前,铁的氧化物已经大量被还原,滴落温度升高,滴落区间变窄。初渣渣量减少使得高炉透气性改善,最大压差与总特性值逐渐变小。结合滴落物与坩埚内剩余物的物相检测,得出富氢煤气对高炉熔滴性能的影响规律和最佳富氢量。     

偶氮氯膦Ⅰ光度法测定铁矿石中低含量氧化钙和氧化镁

铁矿石中低含量氧化钙、氧化镁的测定采用原子吸收光度法测定,受仪器设备限制且造价较高,而湿法分析采用ＥＤＴＡ容量法联合测定,由于含量低,终点不易观察,且误差较大。现采用偶氮氯膦Ｉ光度法测定。方法要点如下：将酸溶试样蒸干,铜试剂分离铁、铝、锰等干扰元素,取分离后的滤液,在ｐＨ１０．５的缓冲溶液中,加入三乙醇胺掩蔽分离后残留的铁、铝、锰,在最大吸收波长５９０nｍ处钙、镁有相同的摩尔吸光度,测定其吸光度Ａ１~［１］,然后加入　３．０ｍＬＥＧＴＡ—Ｐｂ溶液（１十１．１）使钙络合物颜色消褪,摇匀后再测吸光度Ａ…     

硫酸亚铁铵滴定法测定铁矿石中钒含量国家标准研究

通过对硫酸亚铁铵滴定法测定铁矿石中钒含量方法的研究,对原国家标准GB／T6730．32—1986进行修订,新国标增加了碳酸钠一硼酸混合熔剂熔融分解试样,优化了指示剂校正和空白测定及铬干扰的消除方法,同时进行了精密度试验,用精密度（重复性限和再现性限）代替了原标准的允许差。     

重铬酸钾滴定法测定铁矿石中铁含量不确定度的评估和计算

对重铬酸钾滴定法测定铁矿中铁含量的不确定度的产生原因进行了分析 ,并对一个铁矿样品中铁含量测定结果的不确定度进行了评定     

分光光度法测定钢铁中砷含量国际标准的制定

介绍了制定分光光度法测定砷含量国际标准的立项、草案的确立。根据ISO5 72 5 -1,ISO5 72 5 -2 ,ISO5 72 5 -3 ,对利用草案进行国际共同试验的结果进行统计分析 ,说明了本方法的可靠性