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1.
A series of crown ethers containing the azobenzene moiety incorporated into crowns of various sizes [Cr(O6), Cr(O7) and Cr(O8)] and their corresponding alkali metal cation (Li+, Na+, K+, Rb+) complexes have been studied theoretically. The density functional theory (DFT) method was employed to elucidate the stereochemical
structural natures and thermodynamic properties of all of the target molecules at the B3LYP/6-31 G(d) and LANL2DZ level for
the cation Rb+. The fully optimized geometries had real frequencies, thus indicating their minimum-energy status. In addition, the bond
lengths between the metal cation and oxygen atoms, atomic torsion angles and thermodynamic energies for complexes were studied.
Natural bond orbital (NBO) analysis was used to explore the origin of the internal forces and the intermolecular interactions
for the metal complexes. The calculated results show that the most significant interaction is that between the lone pair electrons
of electron-donating oxygens in the cis-forms of azobenzene crown ethers (cis-ACEs) and the LP* (1-center valence antibond lone pair) orbitals of the alkali-metal cations (Li+, Na+, K+ and Rb+). The electronic spectra for the cis-ACEs [cis-Cr(O6), cis-Cr(O7) and cis-Cr(O8)] are obtained by the time-dependent density functional theory (TDDFT) at the B3LYP/6-31 G(d) level. The spectra of the cis-isomers show broad π → π* (S0 → S2) absorption bands at 310–340 nm but weaker n → π* (S0 → S1) bands at 480–490 nm. The calculated results are in good agreement with the experimental results. 相似文献
2.
Theoretical studies of an unsymmetrical calix[4]-crown-5-N-azacrown-5 (1) in a fixed 1,3-alternate conformation and the complexes 1·K+(a), 1·K+(b), 1·K+(c) and 1·K+K+ were performed using density functional theory (DFT) at the B3LYP/6-31G* level. The fully optimized geometric structures
of the free macroligand and its 1:1 and 1:2 complexes, as obtained from DFT calculations, were used to perform natural bond
orbital (NBO) analysis. The two main types of driving force metal–ligand and cation–π interactions were investigated. NBO
analysis indicated that the stabilization interaction energies (E
2) for O…K+ and N…K+ are larger than the other intermolecular interactions in each complex. The significant increase in electron density in the
RY* or LP* orbitals of K+ results in strong host–guest interactions. In addition, the intermolecular interaction thermal energies (ΔE, ΔH, ΔG) were calculated by frequency analysis at the B3LYP/6-31G* level. For all structures, the most pronounced changes in the
geometric parameters upon interaction are observed in the calix[4]arene molecule. The results indicate that both the intermolecular
electrostatic interactions and the cation–π interactions between the metal ion and π orbitals of the two pairs that face the
inverted benzene rings play a significant role. 相似文献
3.
Daniela Josa Angeles Peña-Gallego Jesús Rodríguez-Otero Enrique M. Cabaleiro-Lago 《Journal of molecular modeling》2011,17(6):1267-1272
A comprehensive MP2/6-311 + G(d,p) and B3LYP/6-311 + G(d,p) study of the aromatic character of phospholes, P
n
(CH)4-n
PH with n = 0-4 was conducted. For this purpose, the structures for these compounds were optimized at both theoretical levels and different
magnetic properties (magnetic susceptibility anisotropy, χanis, and the nucleus-independent chemical shifts, NICS) were evaluated. For comparison, these magnetic properties were also calculated
in the optimized structures with planarity constraints. We have also applied the ACID (anisotropy of the current-induced density)
method in this analysis. The main conclusions are the aromatic character of these compounds, the relationship between aromaticity
and planarity and the importance of other factors in this aromaticity. 相似文献
4.
The detailed reaction mechanism for the water-assisted hydrolysis of isocyanic acid, HNCO + (n + 1) H2O → CO2 + NH3 + nH2O (n = 0−6), taking place in the gas phase, has been investigated. All structures were optimized and characterized at the
MP2/6-31 + G* level of theory, and then re-optimized at MP2/6-311++G**. The seven explicit water molecules participating in
the hydrolysis can be divided into two groups, one directly involved in the proton relay, and the other located in the vicinity
of the substrate playing the cooperative role by engaging in hydrogen-bonding to HN = C = O. Two possible reaction pathways,
the addition of water molecule across the C = N bond or across the C = O bond, are discussed, and the former is proved to
be more favorable energetically. Our calculations suggest that, in the most kinetically favorable pathway for the titled hydrolysis,
three water molecules are directly participating in the hydrogen transfer via an eight-membered cyclic transition state, while
the other four water molecules catalyze the hydrolysis of HN = C = O by forming three eight-membered cooperative loops near
the substrate. This strain-free hydrogen-bond network leads to the best estimated rate-determining activation energy of 24.9 kJ mol−1 at 600 K, in excellent agreement with the gas-phase kinetic experimental result, 25.8 kJ mol−1. 相似文献
5.
The anion–π interactions between Br? , Cl? , F? and H? anions and hexafluorobenzene (HFB), 1,2,4,5-tetracyanobenzene (TCB) and tetracyanopyrazine (TCP) have been studied by standard and counterpoise (CP) corrected methods at HF, B3LYP and MP2/6-31+ + G (d,p) levels of theory. The complexation energies were corrected for basis set superposition error (ΔE BSSE) and zero point energy (ΔE BSSE + ZPE). Also, the B3LYP results were corrected by single-point calculation at B3LYP/aug-cc-PVTZ level of theory. Although the CP-corrected method results in higher distances between anions and rings, the standard method gives lower complexation energies. TCP…X? series gives higher complexation energies in both CP-corrected and standard methods. Topological analysis of the charge density ρ(r) has been performed by the means of atoms in molecules method on the wave functions obtained at MP2/6-31+ + G (d,p) level of theory. The number and the nature of critical points depend on aromatic ring and anion. Natural bond orbital analysis indicates that nX → π*CC and nX → π*CN interactions are the most important interactions for TCB (and HFB)…X? and TCP…X? complexes, respectively. 相似文献
6.
Rong Pan Lixiang Cao Haiwei Huang Renduo Zhang Yu Mo 《Applied microbiology and biotechnology》2010,88(4):997-1005
In this study, dried and humid fruiting bodies of Tremella fuciformis and Auricularia polytricha were examined as cost-effective biosorbents in treatment of heavy metals (Cd2+, Cu2+, Pb2+, and Zn2+) in aqueous solution. The humid T. fuciformis showed the highest capacity to adsorb the four metals in the multi-metal solutions. The Pb2+ adsorption rates were 85.5%, 97.8%, 84.8%, and 91.0% by dried T. fuciformis, humid T. fuciformis, dried A. polytricha, and humid A. polytricha, respectively. The adsorption amount of Pb2+ by dried and humid T. fuciformis in Cd2+ + Pb2+, Cu2+ + Pb2+, Pb2+ + Zn2+, Cd2+ + Cu2+ + Pb2+, and Cd2+ + Zn2+ + Pb2+ solutions were not lower than that in Pb2+ solutions. The results suggested that in humid T. fuciformis, Cd2+, Cu2+, and Zn2+ promoted the Pb2+ adsorption by the biomass. In the multi-metal solutions of Cd2+ + Cu2+ + Pb2+ + Zn2+, the adsorption amount and rates of the metals by all the test biosorbents were in the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. Compared with the pseudo first-order model, the pseudo second-order model described the adsorption kinetics much better,
indicating a two-step biosorption process. The present study confirmed that fruiting bodies of the jelly fungi should be useful
for the treatment of wastewater containing Cd2+, Cu2+, Pb2+, and Zn2+. 相似文献
7.
Wei-Wei Han Ying Wang Yi-Han Zhou Yuan Yao Ze-Sheng Li Yan Feng 《Journal of molecular modeling》2009,15(5):481-487
The 3D structure of the amidase from Rhodococcus erythropolis (EC 3.5.1.4) built by homology-based modeling is presented. Propionamide and acetamide are docked to the amidase. The reaction
models were used to characterize the explicit enzymatic reaction. The calculated free energy barrier at B3LYP/6-31G* level
of Model A (Ser194 + propionamide) is 19.72 kcal mol−1 in gas (6.47 kcal mol−1 in solution), and of Model B (Ser194 + Gly193 + propionamide) is 18.71 kcal mol−1 in gas (4.57 kcal mol−1 in solution). The docking results reveal that propionamide binds more strongly than acetamide due to the ethyl moiety of
propionamide, which makes the carboxyl oxygen center of the substrate slightly more negative, making formation of the positively
charged tetrahedral intermediate slightly easier. The quantum mechanics results demonstrate that Ser194 is essential for the
acyl-intermediate, and Gly193 plays a secondary role in stabilizing acyl-intermediate formation as the NH groups of Ser194
and Gly193 form hydrogen bonds with the carbonyl oxygen of propionamide. The new structural and mechanistic insights gained
from this computational study should be useful in elucidating the detailed structures and mechanisms of amidase and other
homologous members of the amidase signature family. 相似文献
8.
Koop JH Grieshaber MK 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):75-83
Fluctuating salinities at different sites on the German salt-polluted rivers Werra and Weser were compared with extracellular
ion levels of specimens of Gammarus tigrinus (Sexton; Amphipoda, Crustacea), collected at the same sites. G. tigrinus regulated haemolymph concentrations of inorganic anions (Cl−, SO2−
4, PO3−
4) and cations (Na+, K+, Mg2+, Ca2+) during fluctuations of salt pollution in the upper Weser. This capacity to regulate varying levels of salt pollution in
the upper Weser, correlated well with the distribution of the brackish amphipods in this river ecosystem. G. tigrinus tolerated periods of Na+ and Cl− stress (>380 mmol l−1) without compensating these maxima by regulating extracellular Na+ and Cl−. However, during such bursts of Na+ and Cl− stress in Werra and Weser, the ability to regulate extracellular [K+] at river water K+ stress of ≥6.0 mmol l−1 may explain why this brackish species has been more successful in these rivers than its competitors like Gammarus pulex. The present investigation demonstrates that the water salinity affects the [NO−
3] in the haemolymph of G. tigrinus. With increasing hypo-osmotic stress the animals accumulate increasing amounts of NO−
3. A simultaneous increase in stream water [NO−
3] causes an additional accumulation of NO−
3 in the haemolymph. The high extent of accumulation indicates that active ion transport systems may be involved. The accumulation
of NO−
3 in the haemolymph has low physiological consequences to G. tigrinus, but when hypo-osmotically stressed under anoxic conditions, nitrite formed by the reduction of nitrate may have an adverse
affect on the metabolism of G. tigrinus.
Accepted: 4 October 1999 相似文献
9.
Because of discrepancies in the available experimental data, an extensive theoretical investigation of the formation of the
Vilsmeier-Haack (VH) complex has been carried out. The barriers to complex formation calculated using eight different density
functional methods (BLYP, B2-PLYP, B3LYP, B3PW91, MPW1K, M06-2X, and PBE1PBE), MP2, and extrapolation techniques (CBS-QB3,
G3B3) with several basis sets (6 − 31 + G**, 6 − 311++G**, 6 − 311 + (3df,2p), aug-cc-pVDZ, and aug-cc-pVTZ) were compared
with experimental data. For the overall reaction, MP2/aug-cc-pVDZ and M06-2X/6−31 + G(d,p) perform best compared to the CBS
techniques. The results help clarify some open mechanistic questions. 相似文献
10.
Wheat leaf growth is known to be spatially affected by salinity. The altered spatial distribution of leaf growth under saline
conditions may be associated with spatial changes in tissue mineral elements. The objective of this study was to evaluate
the spatial distributions of mineral elements and their net deposition rates in the elongating and mature zones of leaf 4
of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in an illitic-chloritic silty
loam with 0 and 120 mM NaCl. Three days after emergence of leaf 4, sampling was begun at 3 and 13 h into the 16-h light period.
Spatial distributions of fresh weight (FW), dry weight (DW), and Na+, K+, Cl−, NO−
3, Ca2+, Mg2+, total P, and total N in the elongating and mature tissues were determined on a millimeter scale. The patterns of spatial
distribution of Na+, Cl−, K+, NO3
−, and Ca2+ in the growing leaves were affected by salinity, while those of Mg2+, total P, and total N were not. Sodium, K+, Cl−, Ca2+, Mg2+, and total N concentrations (mmol · kg−1 FW) were consistently higher at 120 mM NaCl than at 0 mM NaCl along the leaf axis from the leaf base, whereas NO3
− concentration was lower at 120 mM NaCl. Deposition rates of all nutrients were greatest in the elongation zone. The elongation
zone was the strongest sink for mineral elements in the leaf tissues. Local net deposition rates of Na+, Cl−, Ca2+, and Mg2+ (mmol · kg−1 FW · h−1) in the most actively elongating zone were enhanced by 120 mM NaCl, whereas for NO3
− this was depressed. The lower supply of NO−
3 to growing leaves may be responsible for the inhibition of growth under saline conditions. Higher tissue concentrations of
Na+ and Cl− may cause ion imbalance but probably did not result in ion toxicity in the growing leaves. Potassium, Ca2+, Mg2+, total P, and total N are less plausibly responsible for the reduction in leaf growth in this study. Higher tissue K+ and Ca2+ concentrations at 120 mM NaCl are probably due to the presence of high Ca2+ in the soil of this study.
Received: 13 March 1997 / Accepted: 9 June 1997 相似文献
11.
Methods of quantum chemistry have been applied to double-charged complexes involving the transition metals Ni2+, Cu2+ and Zn2+ with the aromatic amino acids (AAA) phenylalanine, tyrosine and tryptophan. The effect of hydration on the relative stability
and geometry of the individual species studied has been evaluated within the supermolecule approach. The interaction enthalpies,
entropies and Gibbs energies of nine complexes Phe•M, Tyr•M, Trp•M, (M = Ni2+, Cu2+ and Zn2+) were determined at the Becke3LYP density functional level of theory. Of the transition metals studied the bivalent copper
cation forms the strongest complexes with AAAs. For Ni2+and Cu2+ the most stable species are the NO coordinated cations in the AAA metal complexes, Zn2+cation prefers a binding to the aromatic part of the AAA (complex II). Some complexes energetically unfavored in the gas-phase are stabilized upon microsolvation. 相似文献
12.
Tezer N 《Journal of molecular modeling》2008,14(1):11-20
The protomeric tautomerizm and conformation of the 2-methyl-4-pyridin-2′-yl-1,5-benzodiazepine molecule were investigated,
and its three neutral tautomers (B1,B2,B3) and their rotamers (C1,C2,C3) were considered. Full geometry optimizations were carried out at the HF/6-31G* and B3LYP/6-31G* levels in gas phase and
in water. The tautomerization processes in water (ɛ = 78.54) were studied by using self-consistent reaction field theory.
The calculation showed that the boat conformation is dominant for the seven-membered diazepine ring in all of the structures,
even with different double bond positions. The calculated relative free energies (ΔG) showed that the tautomer C1 was the most stable structure, and its conformer B1 was the second most stable in the gas phase and in water.
Figure 2-Methyl-4-pyridin-2′-yl-1,5-benzodiazepine 相似文献
13.
The molecular and electronic structures for 12- to 16-crown-4 (named 12C4, 13C4, 14C4, 15C4, 16C4, respectively) and 2,3,5,6,8,9-hexahydrobenzo[b][1,4,7,10]tetraoxacyclododecine
(B12C4) 3,5,6,7,9,10-hexahydro -2H-benzo[e][1,4,7,10]tetraoxacyclotridecine (B13C4) and their complexes with alkali metal
cations Li+ and Na+ have been explored using the density functional theory (DFT) with B3LYP/ 6–31G* method. The nucleophilicity of crown-4 ethers
has been investigated by the Fukui function. Their selectivity trend shows that of all the crown-4 ethers, 14C4 shows the
highest cation selectivity for Li+ over Na+, has been achieved on the basis of thermodynamic analysis. In addition, Li+/crown-4 series are more stable than Na+/crown-4 series in the gas phase. The calculated results are in good agreement with the experimental observation. 相似文献
14.
In the present paper we employ a series of dicationized (K+& C+; C = H, Li, Na, or K) hexapeptide (G6C+K+
x, x = 1, 2, … or 5) complexes in gas phase (GP) and aqueous phase (AP) as models to mimic the key characteristics of the real
biosystems. An interesting phenomenon is observed that the binding properties of K+
x to G6C+ species change in the two phases, i.e., those positive binding energies in the GP become negative ones in the AP. Then we
probe the origin of property change of the binding energies in the two different phases and associate these changes with some
biological phenomena. 相似文献
15.
Du S Wang Y Chen LZ Shi WJ Ren FD Li YX Wang JL Cao DL 《Journal of molecular modeling》2012,18(5):2105-2115
The explosive sensitivity upon the formation of molecule-cation interaction between the nitro group of 3,4-dinitropyrazole
(DNP) and H+, Li+, Na+, Be2+ or Mg2+ has been investigated using the B3LYP and MP2(full) methods with the 6-311++G** and 6-311++G(2df,2p) basis sets. The bond
dissociation energy (BDE) of the C3–N7 trigger bond has also been discussed for the DNP monomer and the corresponding complex. The interaction between
the oxygen atom of nitro group and H+ in DNP…H+ is partly covalent in nature. The molecule-cation interaction and bond dissociation energy of the C3–N7 trigger bond follow
the order of DNP…Be2+ > DNP…Mg2+ > DNP…Li+ > DNP…Na+. Except for DNP…H+, the increment of the trigger bond dissociation energy in comparison with the DNP monomer correlates well with the molecule-cation
interaction energy, natural charge of the nitro group, electron density ρ
BCP(C3–N7), delocalization energy E
(2) and NBO charge transfer. The analyses of atoms in molecules (AIM), natural bond orbital (NBO) and electron density shifts
have shown that the electron density of the nitro group shifts toward the C3–N7 trigger bond upon the formation of the molecule-cation
interaction. Thus, the trigger bond is strengthened and the sensitivity of DNP is reduced. 相似文献
16.
Anwen M. Krause-Heuer William S. Price Janice R. Aldrich-Wright 《Journal of chemical biology》2012,5(3):105-113
The interactions of three platinum(II)-based anticancer complexes [(5,6-dimethyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)platinum(II)]2+, [(5,6-dimethyl-1,10-phenanthroline)(1R,2R-diaminocyclohexane)platinum(II)]2+, and [(5,6-dimethyl-1,10-phenanthroline)(1,2-diaminoethane)platinum(II)]2+ (56MEEN) with BSA have been examined by circular dichroism (CD), fluorescence and 1H pulsed gradient spin–echo (PGSE) diffusion NMR spectroscopy. The number of association constants and sites differed depending upon the spectroscopic method. This may be because each technique monitors different types of interaction/s and/or as a consequence of the different concentration ranges required for each technique. The titration of BSA with the achiral 56MEEN as monitored by CD indicates a reduction in the α-helical nature of the albumin, with the association constant calculated to be ~5 × 106 M−1 for one site. Due to the chiral nature of the other two complexes, their association with albumin was not monitored using CD but was examined using fluorescence and PGSE diffusion NMR. Titration of BSA with any of the three metal complexes resulted in quenching of fluorescence, with the number of association sites calculated to be ~1.1, with an association constant of ~2 × 105 M−1. PGSE diffusion NMR provided insights into interactions occurring with the BSA in its entirety, rather than with individual regions. Metal complex binding sites were estimated (~10 equivalent) from the diffusion data, with the average association constant for all sites ~102–103M−1. These experiments highlight the information that can be elucidated from complementary spectroscopic techniques and demonstrate the usefulness of PGSE diffusion NMR in monitoring multiple weak binding sites, which is of great importance in studying drug-biomolecule interactions. 相似文献
17.
A. Saha N. Saha L.-n. Ji Jing Zhao Fridrich Gregáň S. Ali A. Sajadi B. Song H. Sigel 《Journal of biological inorganic chemistry》1996,1(3):231-238
The acidity constants of methyl phosphoric acid, CH3OPO(OH)2, and orthophosphoric acid, HOPO(OH)2, and the stability constants of the 1 : 1 complexes formed between Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, or Cd2+ and methyl phosphate, CH3OPO3
2–, or hydrogen phosphate, HOPO3
2–, were determined by potentiometric pH titration in aqueous solution (25 °C;I = 0.1 M, NaNO3). On the basis of previously established log K versus pK
a straight-line plots for the complexes of simple phosphate monoesters and phosphonate derivatives, R-PO3
2–, where R is a noncoordinating residue, it is shown that the stability of the M(CH3OPO3) complexes is solely determined (as one might expect) by the basicity of the –PO3
2– residue. It is emphasized that the mentioned reference lines may also be used to reveal increased complex stabilities, for
example, for certain complexes formed with 8-quinolyl phosphate the occurrence of 7-membered chelates can be proven in this
way; the same procedure is also applicable to complexes of nucleotides, etc. The M(HOPO3) complexes are slightly more stable (on average by 0.08 log unit) than it is expected from the basicity of HPO4
2–; this observation is attributed to a more effective solvation, including hydrogen bonding, than is possible with CH3OPO3
2– species.
Received: 9 November 1995 / Accepted: 5 February 1996 相似文献
18.
Characteristics of non-specific permeability and H+-ATPase inhibition induced in the plasma membrane of Nitella flexilis by excessive Cu2+ 总被引:1,自引:0,他引:1
Effects of Cu2+ on a non-specific conductance and H+-ATPase activity in the plasma membrane of the freshwater alga Nitella flexilis L. Agardh was studied using a conventional microelectrode voltage-clamp technique. We show that a Cu2+-induced increase in the non-specific conductance is related to the formation of pores in the plasma membrane. Pore formation
is the result of unidentified chemical reactions, since the Q10 for the rate of increase of conductance over time was about 3. Various oxidants and antioxidants (10 mmol/l H2O2, 10 mmol/l ascorbate, 100 μg/ml superoxide dismutase, and 100 μg/ml catalase) did not alter Cu2+-induced changes in the plasma membrane conductance, suggesting that the effect of Cu2+ was unrelated to peroxidation of plasma-membrane lipids. In contrast, organic and inorganic Ca2+-channel antagonists (nifedipine, Zn2+, Cd2+, Fe2+, Ni2+) inhibited the Cu2+-induced non-specific conductance increase. This suggests that changes in Ca2+ influx underlie this effect of Cu2+. Decreasing the pH or the ionic strength of external solutions also inhibited the Cu2+-induced plasma-membrane conductance increase. Copper was also found to inhibit plasma-membrane H+-ATPase activity with half-maximal inhibition occurring at about 5–20 μmol/l and full inhibition at about 100–300 μmol/l.
The Hill coefficient of Cu2+ inhibition of the H+-ATPase was close to two.
Received: 8 December 1999 / Accepted: 16 August 2000 相似文献
19.
Rongwei Shi Jingling Shao Cheng Wang Xiaolei Zhu Xiaohua Lu 《Journal of molecular modeling》2011,17(5):1007-1016
We have systematically explored and investigated the geometrical structures, stability, growth pattern, bonding character,
and potential energy surface (PES) of the possible isomers of each cluster for planar BnP (n = 1 ∼ 7) at the CCSD(T)/6-311+;G(d)//B3LYP/6-311+G(d) level. A large number of planar structures for the possible isomers
of BnP (n = 1 ∼ 7) and transition states are located. Isomers 1a ∼ 7a of BnP are the lowest-energy structures and 2a, 4a, as well as 6a are more stable than their neighbors. For the lowest-energy structures (1a ∼ 7a) of BnP, P atom lies at the apex and tends to form two B-P bonds with boron atoms. They exhibit planar zigzag growth feature or
approximately spherical-like growth pattern. Results from molecular orbital analysis demonstrate that the formation of the
delocalized π MOs and the σ-radial and σ-tangential MOs plays a critical role in stabilizing the structures of lowest-energy
isomers (2a ∼ 7a) of BnP. Importantly, isomers 3a, 3c, 3d, 4a, 4b, 5b, and 5c of BnP are stable both thermodynamically and kinetically at the CCSD(T)/6-311+G(d)// B3LYP/6-311+G(d) level and detectable in laboratory,
which is valuable for further experimental studies of BnP. 相似文献
20.
Liapi C Zarros A Theocharis S Voumvourakis K Anifantaki F Gkrouzman E Mellios Z Skandali N Al-Humadi H Tsakiris S 《Biological trace element research》2011,143(3):1673-1681
Nickel (Ni) is an environmental pollutant towards which human exposure can be both occupational (mainly through inhalation)
and dietary (through water and food chain-induced bioaccumulation). The aim of this study was to investigate the effects of
short-term Ni-administration (as NiCl2, 13 mg/kg) on the adult rat whole brain total antioxidant status (TAS) and the activities of acetylcholinesterase (AChE),
Na+,K+-ATPase, and Mg2+-ATPase; in addition, the potential effect of the co-administration of the antioxidant L-cysteine (Cys, 7 mg/kg) on the above
parameters was studied. Twenty-eight male Wistar rats were divided into four groups: A (saline-treated control), B (Ni), C
(Cys), and D (Ni and Cys). All rats were treated once daily with intraperitoneal injections of the tested compounds, for 1-week.
Rats were sacrificed by decapitation and the above-mentioned parameters were measured spectrophotometrically. Rats treated
with Ni exhibited a significant reduction in brain TAS (-47%, p < 0.001, BvsA) that was efficiently limited by the co-administration of Cys (-4%, p > 0.05, DvsA; +83%, p < 0.001, DvsB), while Cys (group C) had no effect on TAS. The rat brain AChE activity was found significantly increased by
both Ni (+30%, p < 0.001, BvsA) and Cys (+62%, p < 0.001, CvsA), while it tended to adjust to control levels by the co-administration of Ni and Cys (+13%, p < 0.001, DvsA; −13%, p < 0.001, DvsB). The activity of rat brain Na+,K+-ATPase was significantly decreased by Ni-administration (−49%, p < 0.001, BvsA), while Cys supplementation could not reverse this decrease (-44%, p < 0.001, DvsA). The activity of Mg2+-ATPase was not affected by Ni-administration (−3%, p > 0.05, BvsA), but was significantly reduced when combined with Cys administration (−17%, p < 0.001, DvsA). The above findings suggest that Ni short-term in vivo administration causes a statistically significant decrease
in the rat brain TAS and an increase in AChE activity. Both effects can be, partially or totally, reversed to control levels
by Cys co-administration; Cys could thus be considered (for future applications) as a potential neuroprotective agent against
chronic exposure to Ni. The activity of Na+,K+-ATPase that was inhibited by Ni, could not be reversed by Cys co-administration. The matter requires further investigation
in order to fully elucidate the spectrum of the neurotoxic effects of Ni. 相似文献