LDL的氧化修饰和氧化修饰LDL的组成和结构变化

与低密度脂蛋白(LDL)相比,氧化修饰LDL(O-LDL)的组成、结构和生物学特性发生了深刻的变化,而组成和结构的改变是生物学特性改变的基础.本文根据最近文献资料.结合我们实验室的工作.对LDL的氧化修饰、O-LDL的组成、结构改变,以及它们的机理作一简要综述.     

Intramolecular electron transfer in the oxidation of amines by methylamine oxidase from Arthrobacter P1

 The intramolecular electron-transfer rate constant for the Cu(II)–topa_NH2⇌ Cu(I)–topa_SQ equilibrium in methylamine oxidase has been measured by temperature-jump relaxation techniques. At pH 7.0 the estimated k_obs = 150±30 s^–1 for both methylamine and benzylamine; assuming the equilibrium constant is ≈0.7–1 at pH 7.0 and 296 K, this would correspond to a forward electron-transfer rate constant k_ET≈ 60–75 s^–1. Although substantially slower than the previously determined k_ET≈ 20 000 s^–1 for pea seedling amine oxidase [5] steady-state kinetics measurements established that k_ET > k_cat≈ 4–10 s^–1. Thus the Cu(I)-semiquinone state is a viable intermediate in methylamine oxidase turnover. Received: 16 August 1995 / Accepted: 21 December 1995     

The Superoxide Dismutase-Mimic Copper-Putrescine-Pyridine Suppresses Lipid Peroxidation in CHO Cells. Implications for its Prooxidative and Antioxidative Mechanisms of Action

Copper-Putrescine-Pyridine (Cu-PuPy) is a membrane-permeable complex which efficiently dismutates superoxide. In excess of 0.1 mM it is highly cytotoxic and oxidizes cellular GSH with concomitant production of H₂O₂. Here we show that treatment of CHO cells with 0.2 mM Cu-PuPy (0-200 min) leads to an accumulation of H₂O₂. Organic hydroperoxides which are also formed at low levels in the presence of Cu-PuPy, increase significantly after removal of the copper complex. We conclude that Cu-PuPy acts as an oxidant until cellular GSH is depleted. However, by interfering with radical chain propagation reactions, it suppresses lipid peroxidation and thus substitutes for consumed physiological antioxidants in a later stage of treatment. This consistently explains our previous, seemingly paradox, finding that longer Cu-PuPy treatments may be significantly less toxic than shorter ones.     

Iron and copper in plasma membranes of maize (Zea mays L.) roots investigated by proton induced X-ray emission

Summary Plasma membranes of maize (Zea mays L., cv. Sil Anjou 18) roots were isolated by aqueous two-phase partitioning. Multi elemental analysis by proton induced X-ray emission (PIXE) was used for the investigation of elemental composition of plasma membranes. Fe, Cu, and Zn as well as P, S, and Ca were identified. We did not find significant amounts of V, Mn, Se, Mo, or W.Abbreviations EDTA ethylenediaminetetraacetic acid - HCF III hexacyanoferrate III (ferricyanide, K₃[FeCN₆]) - Hepes 2-[4-(2-hydroxyethyl)-1-piperazine]-ethanesulfonic acid - PIXE proton induced X-ray emission (proton microprobe) - STA siliciotungstic acid - Tris tris (hydroxymethyl)aminomethane     

稀有鮈鲫──一种新的鱼类毒性试验材料

本文研究了稀有鲫（Ｇｏｂｉｏｃｙｐｒｉｓｒａｒｕｓ）作为毒性试验材料的可行性。采用换水式试验,在硬度为２００ｍｇ／Ｌ（以ＣａＣＯ３计）、ｐＨ７．８±０．２、温度２４－２５℃条件下研究了铬、铜、锌和五氯酚（ＰＣＰ）对稀有鲫的急性毒性。重铬酸钾对２日龄稀有鲫的２４ｈ和９６ｈ和ＬＣ５０控制范围分别２６３．６－３３４．７和１１５３－１７８．５ｍｇ／Ｌ（ｎ＝８）。铬、铜、锌和五氯酚对２日龄稀有鲫的急性毒性值（９６ｈＬＣ５０）范围,从铜的５２．２μｇ／Ｌ到铬的５２０００μｇ／Ｌ,毒性大小的顺序是铜＞五氯酚＞锌＞铬。研究结果表明,稀有鲫有可能发展成为一种较为理想的毒性试验材料。     

Novel findings on the copper catalysed oxidation of cysteine

Summary The oxidation of cysteine (RSH) has been studied by using O₂, ferricytochrome c (Cyt c) and nitro blue tetrazolium (NBT) as electron acceptors. The addition of 200M Cu^II to a solution of 2mM cysteine, pH 7.4, produces an absorbance with a peak at 260 nm and a shoulder at 300 nm. Generation of a cuprous bis-cysteine complex (RS-Cu^I-SR) is responsible for this absorbance. In the absence of O₂ the absorbance is stable for long time while in the presence of air it vanishes slowly only when the cysteine excess is consumed. The neocuproine assay and the EPR analysis show that the metal remains reduced in the course of the oxidation of cysteine returning to the oxidised form at the end of reaction when all RSH has been oxidised to RSSR. Addition of Cu^II enhances the reduction rate of Cyt c and of NBT by cysteine also under anaerobiosis indicating the occurrence of a direct reduction of the acceptor by the complex. It is concluded that the cuprous bis-cysteine complex (RS-Cu^I-SR) is the catalytic species involved in the oxidation of cysteine. The novel finding of the stability of the complex together with the metal remaining in the reduced form during the oxidation suggest sulfur as the electron donor in the place of the metal ion.Abbreviations RSH cysteine - RS^– cysteine in the thiolate form - RS^· thiyl radical of cysteine - RSSR cystine - Cyt c cytochrome c - SOD superoxide dismutase - NBT nitro blue tetrazolium - NBF nitro blue formazan - DTNB 5,5-dithiobis-2-nitrobenzoic acid - DTPA diethylenetriaminepentaacetic acid Dedicated to prof. A. Ballio ob the occasion of his 75th birthday.     

A spin-labeled derivative of Procion brilliant blue MX-R. Synthesis and interaction with pig heart nucleoside diphosphate kinase

The ¹H-NMR spectrum of cucumber basic blue protein (CBP) has been recorded. Examination of the spectrum of the reduced protein suggests that one or more sidechains exist in conformations which interconvert slowly at ambient temperatures. His 39, His 84 and Met 89 are identified as copper ligands by redox titration and by amino acid sequence homology with plastocyanin and azurin. The importance of a Phe sidechain close to the Met ligand in the potential blue copper site is confirmed. Broadening of His ligand resonances at elevated temperatures reveals an exchange process at the reduced copper centre.     

The possible role of metallothioneins in copper tolerance of Silene cucubalus

Growth and copper-binding of a copper-tolerant and a copper-sensitive population of Silene cucubalus (L.) Wib. have been studied. The copper-tolerant plants showed a much lower uptake and a proportionally higher transport of copper from root to shoot. A copper-binding protein with an apparent M_r of 8500 resembling metallothionein has been isolated from the roots of copper-treated plants of the tolerant population. After 20 d, the protein was observed to be inducible upon copper supply in the copper-tolerant plants, but not yet in the sensitive ones. This could be an indication of a difference in metalregulated synthesis of the protein. Ion-exchange chromatography of the 8500 protein yielded a major copper-containing fraction eluting at high ionic strength. Other characteristics such as UV absorption and amino-acid composition resembled strongly those of metallothioneins. The involvement of metallothioneins in the detoxification of copper within Cu-tolerant plants is discussed in relation to other mechanisms.Abbreviation DEAE diethyloaminoethyl     

Chemical activity and biological effect of sludge-borne heavy metals and inorganic metal salts added to soils

Summary A greenhouse experiment was conducted in order to evaluate the chemical activity and the uptake by Italian ryegrass (Lolium perenne cv. S24) of Zn, Cu, Cd and Ni added to a sandy and a heavy clay soil in two different forms: as inorganic salts and sludge-borne.The chemical activity of heavy metals as evaluated with different extractants was higher for the inorganic salt treatment and for the sandy soil, indicating that the chemical form of the metal and soil characteristics largely affect their extractability.The different chemical activity was also reflected in plant uptake. For all metals the degree of plant accumulation decreased in the following order: sandy soil-salt sandy soil-sludge> clay soil-salt>clay soil-sludge.These findings indicate that caution must be used when using results of inorganic salt treatments and different soil types to evaluate plant uptake of heavy metals from sludge amended soils.     

Relationships of bio-climatic zones and lithology with various characteristics of forest soils in Greece

Summary Soils derived from a number of different parent materials (lithologies) and developed along a climatic gradient, manifested by the altitudinal succession of natural vegetation zones (Mediterranean, sub-Mediterranean, Mountainous and Pseudoalpine), were sampled throughout mainland Greece.In soils derived from siliceous parent materials low in clay, acidity increase and percent base saturation decreases from the Mediterranean to the Pseudoalpine vegetation zones. Clay illuviation is found mainly in soils developed in the Mediterranean and the sub-Mediterranean zones. No such changes are apparent in clayey soils rich in bases.Organic matter content of the mineral portion of the soil profile increases by a factor of 2 with a decrease in mean annual air temperature of about 10°C. The pattern of change in clay and soil organic matter content with climate is in relatively good agreement with soil development trends in the area, when soil profiles are named according to the FAO-Unesco soil map of the world.Concentrations of Ca and Mg decrease and those of total N, total and extractable P, K, Fe, Mn and Zn increase from the Mediterranean to the Mountainous zone. Within the same zone, however, concentrations of N, Ca, K, Fe, Mn and Zn decrease, but those of Mg, total and extractable P increase with soil depth. The concentrations of most macro- and micronutrients in the humic horizon are several times higher than those in the mineral portion of the soil profile due to biological enrichment.