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1.
A scale of selectivity for the binding of calcium and some heavy metal ions by citrus and sugar-beet pectins was set up by pH-measurements. The same order of selectivity was found for the two pectins, decreasing as follows: Cu 2+ Pb 2+ Zn 2+ > Cd 2+ Ni 2+ ≥ Ca 2+. Binding isotherms for Ca 2+, Cu 2+, Ni 2+, Pb 2+ and Zn 2+ ions have shown a greater binding level when the ionic strength decreased and when the pectin concentration increased in the presence of 0.1 M NaNO 3. By comparing binding isotherms, the same order of selectivity was found as by pH-studies. Scatchard plots and Hill index evaluation showed for all ions and all pectins anticooperative interactions in water. In the presence of 0.1 M NaNO 3, citrus pectins displayed cooperative interactions for all metal ions. In contrast, for sugar-beet pectins, cooperative interactions only occured with Cu 2+ and Pb 2+. With Ca 2+, Ni 2+ and Zn 2+ sugar-beet pectins displayed Scatchard plots which could not be distinguished from an anticooperative binding. This difference of behaviour could be related to the presence of acetyl groups decreasing the affinity of Me 2+ for sugar-beet pectins. 相似文献
2.
The effect ot Cu 2+ and Ca 2+ ions, on the ultraviolet differential (UVD) spectra of single-stranded poly I was studied and the coordination (Δε b) and conformation (Δε c) conponents of the spectra calculated The comparison of Δε b and the UVD spectrum of protonated IMP leads to the conclusion that N(7) ot inosine-5'-monophosphate (IMP) is a coordinating site tor Ca 2+ and Cu 2+ ions on the polymer bases. The binding ot Ca 2+ and Cu 2+ ions causes differently directed displacements of the four absorption bands of poly I, which are observed in the wavenumber range (50-34) × 10 3 cm −1 The calculation of concentration dependencies tor the association constants ( K“) ot Ca 2+ and Cu 2+ ions binding to poly I bases shows that the binding is cooperative The K“ values for the poly I + Ca 2+ complex are two orders of magnitude lower than those for the poly 1 + Cu 2+ complex At low ion concentrations, binding to the poly I phosphates predominates and increases the degree of the polynucleotide helicity. At higher concentrations the spectra are mainly affected by the ion binding to bases, which results in melting of the helical parts of poly I At Ca 2+ concentrations exceeding 10 −3 M light-scattering aggregates are formed. The degree of monomer order in them is close to that observed in multistranded helices of poly I 相似文献
3.
A new functional macrocyclic ligand, 2,4-dinitrophenylcyclen (= 1-(2,4-dinitrophenyl)-1,4,7,10-tetraazacyclododecane), has been synthesized and isolated as its trihydrochloric acid salt (L·3HCl). The protonation constants (log Kn) for three secondary nitrogens of L were determined by potentiometric pH titration to be 10.10, 7.33 and <2 with I = 0.10 (NaNO 3) at 25°C. The 2,4-dinitrophenylaniline chromophore was proven to be a good reporter signaling proton- and metal-binding events in the macrocyclic cavity. The UV absorption band (λ max 370 nm, 8200) of the 2,4-dinitrophenylaniline moiety at pH ≥ 9 becomes quenched as pH is lowered (to pH 3.1, where the major species is L·2H +), due to the strong protonation effect extended to the aniline moiety within the macrocyclic cavity. This is in sharp contrast to the pH-independent UV absorption (λ max 390 nm, 14 000) of a reference compound, N,N-diethyl-2,4-dinitroaniline. The UV absorption band of L is shifted to lower wavelengths with Zn 2+ (λ max 320 nm), Cd 2+ (λ max 316 nm) and Pb 2+ (λ max 317 nm), while it almost disappears with Cu 2+ and Ni 2+. The 1:1 Zn 2+ and Cu 2+ complexes with L were isolated and characterized. The Zn 2+ complex recognizes 1-methylthymine anion (MT −) in aqueous solution at physiological pH to yield a stable ternary complex ZnL-MT −. The X-ray crystal structure of ZnL-MT − showed that Zn 2+ is four-coordinate with three secondary nitrogens of L and the deprotonated imide anion that is cofacial to the 2,4-dinitrophenyl ring. 相似文献
4.
Selectivity coefficients for binding of negative and positive ions to chitosans of different chemical composition have been determined by equilibrium dialysis. Chitosans with different fraction of acetylated units ( FA of 0.01 and 0.49) generally behaved similarly in their selectivity towards both negative and positive ions. No selectivity was found in the binding of chloride and nitrate ions, while chitosan showed a strong selectivity towards molybdate polyoxyanions, with selectivity coefficients around 100. Chitosan showed a strong selectivity towards copper (Cu 2+) compared to the metal ions zinc (Zn 2+), cadmium (Cd 2+) and nickel (Ni 2+), with selectivity coefficients from 10 to 1000, while little or no selectivity could be detected with the other metal ions. Ionic strength and pH did not influence the selectivity coefficients of the chitosans towards the metal ions. 相似文献
5.
The use of different chemically modified cassava waste biomass for the enhancement of the adsorption of three metal ions Cd, Cu and Zn from aqueous solution is reported in this paper. Treating with different concentrations of thioglycollic acid modified the cassava waste biomass. The sorption rates of the three metals were 0.2303 min−1 (Cd2+), 0.0051 min−1 (Cu2+), 0.0040 min−1 (Zn2+) and 0.109 min−1 (Cd2+), 0.0069 min−1 (Cu2+), 0.0367 min−1 (Zn2+) for 0.5 and 1.00 M chemically modified levels, respectively. The adsorption rates were quite rapid and within 20–30 min of mixing, about 60–80% of these ions were removed from the solutions by the biomass and that chemically modifying the binding groups in the biomass enhanced its adsorption capacity towards the three metals. The results further showed that increased concentration of modifying reagent led to increased incorporation, or availability of more binding groups, in the biomass matrix, resulting in improved adsorptivity of the cassava waste biomass. The binding capacity study showed that the cassava waste, which is a serious environmental nuisance, due to foul odour released during decomposition, has the ability to adsorb trace metals from solutions. 相似文献
6.
The antiviral drug, phosphonoacetic acid (PAA), forms stable complexes with Mg 2+, Ca 2+, Cu 2+ and Zn 2+. Stability constants of these complexes were determined in aqueous solution (0.15 M in KNO 3, 37°) by potentiometric titration. Mixed ligand complex formation of Cu 2+ and Zn 2+ with PAA and glycinate ion, and with PAA and histidinate ion, was studied. In a theoretical model for blood plasma, PAA affects the distribution of Mg 2+ and, to a lesser extent, Ca 2+. 相似文献
7.
Hydroxyl or peroxyl radicals and hypochlorous acid (HOCl) are known to cause the oxidation of lipoproteins. Here, we examined Cu 2+-binding property of paraoxonase 1 (PON1), and antioxidant actions of peptides, resembling His residue-containing sequences in PON1, against oxidations by Cu 2+, peroxyl radicals or HOCl. When Cu 2+-binding property of PON1 was examined spectrophotometrically, the maximal Cu 2+ binding was achieved at 1:1 molar ratio of PON1: Cu 2+. Additionally, Cu 2+-catalyzed oxidative inactivation of PON1 was prevented by Ca 2+-depleted PON1 at 1:1 ratio, but not diethylpyrocarbonate (DEPC)-modified PON1, suggesting the participation of His residue in Cu 2+-binding. When His-containing peptides were examined for antioxidant actions, those with either His residue at N-terminal position 2 or 3, or His-Pro sequence at C-terminal remarkably prevented Cu 2+-mediated low density lipoprotein (LDL) oxidation and PON1 inactivation. Especially, FHKALY, FHKY or NHP efficiently prevented Cu 2+-induced LDL oxidation (24 h), indicating a tight binding of Cu 2+ by peptides. In support of this, the peptide/Cu 2+ complexes exhibited a superoxide-scavenging activity. Separately, in oxidations by 2,2'-azobis-2-amidinopropane hydrochloride or HOCl, the presence of Tyrosine (Tyr) or Cysteine (Cys) residue markedly enhanced antioxidant action of His-containing peptides. These results indicate that His-containing peptides with Tys or Cys residues correspond to broad spectrum antioxidants in oxidation models employing Cu 2+, 2,2'-azobis-2-amidinopropane hydrochloride (AAPH) or HOCl. 相似文献
8.
Binding of some divalent cations (Ca 2+, Cd 2+, Cu 2+, Ni 2+, Pb 2+ and Zn 2+) in aqueous solution by saponified and cross-linked sugar-beet pulp was investigated. Saponification doubled the cation-exchange capacity, while cross-linking decreased specific surface area and hydration properties to low and stable values independent of pH and ionic strength conditions. The sorption isotherms indicated a high metal-binding capacity which increased with sorbent concentration, and followed a clear order of selectivity: Cu 2+˜Pb 2+ Zn 2+˜Cd 2+ > Ni 2+ > Ca 2+. The sorption data were better represented by the Langmuir isotherm than by the Freundlich one, suggesting that the monolayer sorption, mainly due to ion-exchange, would not be disturbed by lateral interactions between cations sorbed with similar sorption energies. The same order of selectivity could be drawn from the Langmuir parameters, sorption equilibrium constants ( KL) and maximum binding capacities (Me Amax). Whatever the cation, KL decreased with increasing sorbent concentration, while Me bmax increased. Higher quantities of Cu 2+ and Pb 2+ than predicted by the one divalent cation to two carboxyl functions ratio were bound. This was attributed to the partial contribution to the sorption phenomenon of hydroxyl functions close to ionic sites, explaining the higher affinity of such cations for substrates. Cross-linked pulp exhibited higher metalbinding capacity per volume unit than the raw pulp. 相似文献
9.
以拟南芥(Arabidopsis thaliana)和谷子(Setaria italic)为研究材料,利用锌特异性探针HL1,使用荧光分光光度仪、等温滴定热量测定仪(ITC200)和倒置荧光显微镜等仪器探究了该化学探针的特性以及植物细胞外游离Zn~(2+)的分布。结果表明,当HL1与不同元素溶液混合时,只与Zn~(2+)特异性结合,在紫外光(UV)激发下,发射出波长为500 nm的蓝色荧光;生成物的平衡解离常数KD=7.02×10–4 mol·L–1,具有很好的稳定性。拟南芥叶片中的Zn~(2+)分布于细胞间隙及叶表皮毛的外周和表层,且叶表皮毛的荧光强度具有明显的浓度依赖性;谷子叶片中的Zn~(2+)分布在细胞间隙以及维管组织。拟南芥根中的Zn~(2+)分布于根的伸长区,且荧光强度也明显地表现出与浓度相关。由此推断,根伸长区与Zn~(2+)运输有关,叶的维管组织是植物细胞外运输Zn~(2+)的主要途径,细胞间隙和叶表皮毛是植物储存Zn~(2+)的主要区域。HL1适用于检测细胞外Zn~(2+)的分布。 相似文献
10.
Pb 2+ and Zn 2+ inhibition of photosystem II (PSII) activity was reported to be mediated via displacement of native inorganic cofactors (Cl −, Ca 2+ and Mn 2+) from the oxygen evolving complex, OEC [Rashid and Popovic (1990) FEBS Lett. 271, 181–184; Rashid et al. (1991) Photosynth. Res. 30, 123–130]. Since the binding sites of these cofactors are protected by a shield of three extrinsic polypeptides (17, 23 and 33 kDa), we investigated whether these metal ions affect the extrinsic polypeptide shield of OEC. By immunoblotting with antibodies recognizing the 23 and 33 kDa polypeptides, we showed that both the metal ions significantly dissociated the 23 kDa (+17 kDa) polypeptide, and partially dissociated the 33 kDa. Ca 2+, one of the important inorganic cofactors of oxygen evolution, strongly prevented the dissociating action of Pb 2+ but did not prevent the action of Zn 2+. The probable molecular mechanism of action of Pb 2+ and Zn 2+ on PSII OEC is discussed. 相似文献
11.
The stability constants of the 1:1 complexes formed between Mg 2+, Ca 2+, Sr 2+, Ba 2+, Mn 2+, Co 2+, Ni 2+, Cu 2+, Zn 2+ or Cd 2+ (M 2+) and the simple, sterically unhindered imidazole-type ligands, imidazole, 1-methylimidazole, 5-chloro-1-methylimidazole, N-(2,3,5,6-tetrafluorophenyl)imidazole or 4′-(imidazol-1-yl)acetophenone (L), were determined by potentiometric pH titrations in aqueous solution (25°C; I = 0.5 M, NaNO 3). The construction of log KMLM versus p KHLH plots results in straight lines; the equations for the least-squares lines are calculated and listed. These data allow calculation of the expected stability constant for a complex of any imidazole-type ligand, provided its p KHLH value (in the p Ka range 4–8) is known. For the stabilities of Fe 2+ complexes with imidazole-type ligands an estimation procedure is provided. It is shown further that the complex formation between 1-methylbenzimidazole (MBI) and Mn 2+, Ni 2+, Cu 2+ or Zn 2+ is s sterically hindered, i.e. the data points for these M(MBI) 2+ complexes do not fall on the straight lines defined by the imidazole-type ligands. 相似文献
12.
Silica gel bead coated with macroporous chitosan layer (CTS-SiO 2) was prepared, and the metal immobilized affinity chromatographic (IMAC) adsorbents could be obtained by chelating Cu 2+, Zn 2+, Ni 2+ ions, respectively on CTS-SiO 2, and trypsin could be adsorbed on the IMAC adsorbent through metal–protein interaction forces. Batch adsorption experiments show that adsorption capacity for trypsin on these IMAC adsorbent variated with change of pH. The maximal adsorption reached when the solution was in near neutral pH in all three IMAC adsorbents. Adsorption isothermal curve indicated that maximal adsorption capacity could be found in the Cu 2+-CTS-SiO 2 with the value of 4980 ± 125 IU g −1 of the adsorbent, while the maximal adsorption capacity for trypsin on Zn 2+ and Ni 2+ loaded adsorbent was 3762 ± 68 IU g −1 and 2636 ± 53 IU g −1, respectively. Trypsin immobilized on the IMAC beads could not be desorbed by water, buffer and salt solution if the pH was kept in the range of 5–10, and could be easily desorbed from the IMAC beads by acidic solution and metal chelating species such as EDTA and imidazole. The effect of chelated metal ions species on CTS-SiO 2 beads on the activity and stability of immobilized trypsin was also evaluated and discussed. Trypsin adsorbed on Zn-IMAC beads retained highest amount of activity, about 78% of total activity could be retained. Although the Cu-IMAC showed highest affinity for trypsin, only 25.4% of the calculated activity was found on the beads, while the activity recovery found on Ni-IMAC beads was about 37.1%. A remarkable difference on stability of trypsin immobilized on three kinds of metal ion chelated beads during storage period was also found. Activity of trypsin on Cu-IMAC decreased to 24% of its initial activity after 1-week storage at 4 °C, while about 80% activity was retained on both Ni-IMAC and Zn-IMAC beads. Trypsin immobilized on Zn-CTS-SiO 2 could effectively digest BSA revealed by HPLC peptide mapping. 相似文献
13.
The influence of Cu 2+ ions on the physical properties of resealed human erythrocyte membranes was studied by fluorescence spectroscopy. A net ordering effect was observed at the hydrophobic–hydrophilic interface both in the bulk as well as in the lipid–protein boundary. The explanation for this result was found by X-ray diffraction performed in multilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. Cu 2+ did not significatively affect the structure of DMPE; however, DMPC polar head and hydrocarbon chain arrangements were perturbed at low but reordered at high Cu 2+ concentrations. These effects were respectively explained in terms of a limited and extended interaction between Cu 2+ ions and DMPC PO 4− groups. Thus, the ordering effect in the erythrocyte membrane could be based on the interaction of this cation with phosphatidylcholine phosphate groups located in its outer leaflet. This binding, besides producing a decrease of membrane fluidity, might also induce a change in its electric field. These two effects should affect the activity of membrane proteins, particularly of ion channels. In fact, it was found that increasing concentrations of Cu 2+ ions applied to either the mucosal or serosal surface of the isolated toad skin elicited a dose-dependent decrease of the short-circuit current (SCC) and of the potential difference (PD). These results lead to the conclusion that Cu 2+ ions inhibited Na + transport across the epithelial cell membranes. 相似文献
14.
分离纯化刺芹侧耳 Pleurotus eryngii芳基醇氧化酶,并探究其酶学性质。通过硫酸铵盐沉、DEAE-Sepharose Fast Flow弱阴离子交换层析、Sephacryl S-200 High Resolution凝胶过滤层析和Source 15Q强阴离子交换层析,得到纯化的单一酶。经肽指纹图谱鉴定,确定其为芳基醇氧化酶,酶活回收率25.5%,纯化倍数38.2。结合SDS-PAGE和IEF-PAGE分析,确定其分子量和等电点分别为70kDa和4.2。以藜芦醇为底物,该酶最适反应pH为6.0,最适反应温度为70℃,金属离子Zn 2+、Fe 2+和Cu 2+对芳基醇氧化酶的活性抑制作用明显, Km和 Vmax分别为0.921mmol/L和80U/mg。 相似文献
15.
In our search to establish a reference ·OH production system with respect to which the reactivity of copper(II) complexes could then be tested, the influence of free Cu 2+ ions on the Cu +/H 2O 2 reaction has been investigated.
This influence depends on the C Cu2+/C Cu+ ratio. At low Cu 2+ concentrations, ·OH damage to various detector molecules decreases with increasing Cu 2+ concentrations until C Cu2+/C Cu+ reaches unity. Above this value, ·OH damage increases sharply until C Cu2+/C Cu+ becomes equal to 5 with salicylate and 2 with deoxyribose, ratios for which the protective effect of Cu 2+ cancels. Finally, at higher concentrations, Cu 2+ ions logically add their own ·OH production to that normally expected from Cu + ions. The possible origin of this unprecedented alternate effect has been discussed. The possible influence of Cu + ions on the generation of ·OH radicals by water gamma radiolysis has also been tested and, as already established for Cu 2+ in a previous work, shown to be nonexistent. This definitely confirms that either form of ionised copper cannot scavenge ·OH radicals in the absence of a Iigand. 相似文献
16.
The influence of co-cations (cadmium, copper, cobalt and nickel) on lead and zinc biosorption by Streptoverticillium cinnamoneum and Penicillium chrysogenum in binary and multimetal systems was evaluated. The metal sorption capacity of S. cinnamoneum was higher than P. chrysogenum for all the metals tested. Both the biomasses exhibited preferential uptake of lead in a multimetal situation. Even though mutual inhibition was seen for all binary systems containing zinc, systems containing lead exhibited unequal inhibition. The extent of metal sorption was dependent on metal chemistry, affinity for binding sites and the type of metal binding. In multimetal systems, S. cinnamoneum and P. chrysogenum exhibited preferential sorption orders: Pb 2+ > Zn 2+=Cu 2+ > Cd 2+ > Ni 2+ > Co 2+ and Pb 2+ > Cu 2+ > Zn 2+ > Cd 2+ > Ni 2+ > Co 2+. The order of metal biosorption in a multimetal system could be predicted well on the basis of Langmuir parameters evaluated in binary metal systems. 相似文献
17.
Interactions of calf thymus DNA with sequential polypeptides were studied using c.d. spectroscopy in aqueous solutions. It was found that DNA structural alterations induced by sequential polypeptides (
-Arg-X-Gly) n (where
) are modulated by the nature of the X residue. Thus, the polypeptide (
-Arg-
-Nva-Gly) n induced the 10.2B-DNA form, whereas the polypeptides (
-Arg-
-Ile-Gly) n having one methyl group less on the X residue side chain, did not provide any significant modification to the structure of DNA. The effect of ionic strength from 0.14
NaCl (physiological value) to zero was also analysed on the basis of the observed c.d. changes and the degree of complexation in the DNA-polypeptides was estimated. 相似文献
18.
The embryo of oviparous species is confronted by a highly oxidative stress generating as it grows and must rely on effective antioxidant system for protection. Proteins of avian egg albumin have been suggested to play the major redox-modulatory role during embryo development. Recently, we found that ovotransferrin (OTf) undergoes distinct thiol-linked self-cleavage in a redox-dependent process. In this study, we explore that OTf is SOD mimic protein with a potent superoxide anion (O 2−) scavenging activity. The O 2− scavenging activity was investigated using the natural xanthine/xanthine oxidase (X/XOD) coupling system. OTf exhibited O 2− scavenging activity in a dose-dependent manner and showed remarkably higher scavenging activity than the known antioxidants, ascorbate or serum albumin. The isolated half-molecules of OTf exhibited higher scavenging activity than the intact molecule, whereas the N-lobe showed much greater activity. OTf dramatically quenched the O 2− flux but had no effect on the urate production in the X/XOD system, indicating its unique specificity to scavenge O 2− but not oxidase inhibition. Strikingly, metal-bound OTf exhibited greater O 2− dismutation capacity than the apo-protein, ranging from moderate (Zn 2+-OTf and Fe 2+-OTf) to high (Mn 2+-OTf and Cu 2+-OTf) activity with the Cu 2+-OTf being the most potent scavenger. In a highly sensitive fluorogenic assay, the metal-bound OTf exhibited significant increase in the rate of H 2O 2 production in the X/XOD reaction than the apo-OTf, providing evidence that Zn 2+-, Mn 2+- and Cu 2+-OTf possess SOD mimic activity. This finding is the first to describe that OTf is an O 2− scavenging molecule, providing insight into its novel SOD-like biological function, and heralding a fascinating opportunity for its potential candidacy as antioxidant drug. 相似文献
19.
采用水培方法,研究高浓度镉(0.1 mmol·L -1 Cd 2+)、锌(0.15 mmol·L -1 Zn 2+)及其复合作用(0.1 mmol·L -1 Cd 2++0.15 mmol·L -1Zn 2+)对烟草种子的萌发率、幼苗叶片活性氧(ROS)水平、抗氧化物浓度、抗氧化酶活性及膜脂过氧化程度的影响.结果表明: 单因子条件下,与对照相比,高浓度镉、锌处理烟草种子萌发率降低;叶片超氧自由基(O 2-· )产生速率与过氧化氢(H 2O 2)含量升高;过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、脱氢抗化血酸还原酶(DHAR)、单脱氢抗坏血酸还原酶(MDAR)和谷胱甘肽还原酶(GR)活性升高;谷胱甘肽(GSH)含量及其与氧化型谷胱甘肽比值(GSH/GSSG)下降;丙二醛(MDA)含量升高.与镉、锌单因子处理相比,镉、锌复合处理的烟草种子萌发率显著升高;O 2-· 产生速率、H 2O 2和MDA含量降低;CAT、APX、MDAR活性在处理末期升高.镉、锌胁迫对烟草可造成生理水平上的损伤,且毒性效应随着处理时间的延长而增强.镉、锌复合作用可缓解镉、锌单因子胁迫对烟草幼苗的毒害. 相似文献
20.
The authors previously reported that Fe 2+ is capable of increasing the binding of dopamine and of serotonin to “serotonin binding proteins” which are present in soluble extracts from calf brain. In this study, it is shown that Mn 2+ and Cu 2+ are also capable of increasing the binding, but for dopamine only. As for Fe 2+, Mn 2+ and Cu 2+ are likely to promote the binding by virtue of their ability to enhance the oxidation of dopamine into dopamine-O-quinone, a derivative which is known to undergo covalent association with sulfhydryl groups of proteins. Data such as the irreversible nature of the majority of the binding, the inhibitory action of reducing agents (sodium ascorbate) and of reagents which contain, or modify sulfhydryl groups (reduced glutathione) are compatible with such a mechanism. The three metal ions are also capable of inactivating part of the binding sites on SBP directly; this effect is more pronounced for Cu 2+ than for Fe 2+ and it is only weak for Mn 2+. The Fe 2+-mediated binding of dopamine is inhibited by the superoxide dismutase enzyme, and it was therefore suggested that Fe 2+ enhances the oxidation of dopamine by virtue of its ability to produce superoxide radicals out of dissolved molecular oxygen. Such a mechanism does not appear to take place in the case of Mn 2+ and Cu 2+. Instead, it is likely that Cu 2+ and dopamine form a complex which is highly susceptible towards oxidation by dissolved molecular oxygen. Mn 2+, on the other hand, can easily be oxidized into Mn 3+, which is capable to oxidize dopamine by itself. Chronic manganese intoxication (from exposure to manganese) and Wilson's disease (related to inadequate elimination of copper) go along with neurological symptoms which are very similar to those encountered in Parkinson's disease. Our data indicate that manganese and copper ions accelerate the oxidation of catecholamines to produce toxic quinones. These quinones could, at least in part, account for the degeneration of dopamininergic neurons in such pathologies. 相似文献
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