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1.
The crystal and molecular structure of the complex of amylose with dimethyl sulfoxide has been studied by a combination of stereochemical analysis, potential energy, and X-ray diffraction methods. The complex crystallizes in a pseudotetragonal unit cell with a = b = 19.17 Å and c (fiber axis) = 24.39 Å, with two antiparallel chains per unit cell and space group P212121. The amylose chain is a left-handed 61(1.355) helix with three turns per crystallographic repeat. The O(6) rotational position is approximately gt. Dimethyl sulfoxide is located inside the helix with one DMSO molecule for every three glucose residues. An additional four DMSO molecules and eight water molecules each are located in the large interstices between chains, and it is the interaction of these molecules with the helix that results in the pseudotetragonal chain packing. The interstitial DMSO is the source of the previously reported additional layer lines, which are not consistent with the 8.13-Å amylose repeat distance. The final R factor for the layers with amylose contribution to the structure factors was 0.29, while the overall R factor was 0.35. The stereochemical packing analysis provided suitable phasing models for the subsequent X-ray refinement. 相似文献
2.
Similarities and differences in interaction of K+ and Na+ with condensed ordered DNA. A molecular dynamics computer simulation study
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Four 20 ns molecular dynamics simulations have been performed with two counterions, K+ or Na+, at two water contents, 15 or 20 H2O per nucleotide. A hexagonal simulation cell comprised of three identical DNA decamers [d(5′-ATGCAGTCAG) × d(5′-TGACTGCATC)] with periodic boundary condition along the DNA helix was used. The simulation setup mimics the DNA state in oriented DNA fibers or in crystals of DNA oligomers. Variation of counterion nature and water content do not alter averaged DNA structure. K+ and Na+ binding to DNA are different. K+ binds to the electronegative sites of DNA bases in the major and the minor grooves, while Na+ interacts preferentially with the phosphate groups. Increase of water causes a shift of both K+ and Na+ from the first hydration shell of O1P/O2P and of the DNA bases in the minor groove with lesser influence for the cation binding to the bases in the major groove. Mobility of both water and cations in the K–DNA systems is faster than in the Na–DNA systems: Na+ organizes and immobilizes water structure around itself and near DNA while for K+ water is less organized and more dynamic. 相似文献
3.
The crystal structure of potassium hydroxide complexed amylose, obtained by heterogeneous deacetylation of amylose triacetate, has been determined through a combined stereochemical structure-refinement and X-ray diffraction-analysis. The structure crystallizes in an orthorhombic unit-cell with parameters a 8.84, b 12.31, and c (fiber repeat) 22.41 Å, and with P212121 symmetry. The conformation of the amylose chain is a distorted, left-handed helix with 6 d-glucose residues per turn. Each three-residue asymmetric unit is complexed with one molecule of potassium hydroxide and three molecules of water. The K+ ion coordinates with four oxygen atoms of the amylose chain and with two other oxygen atoms, and this coordination is probably the cause for the more-extended amylose chain-conformation than would be predicted from a φ, ψ map. The distortions in the chain are primarily manifested by different O-6 rotations and by slightly different bridge and φ, ψ angles for the individual residues. The structure is extensively hydrogen bonded, although largely through water molecules, which accounts for its ready water solubility. The left-handed conformation of the chain in this structure is consistent with the conformations of amylose triacetate and V-amylose, both of which are left-handed. 相似文献
4.
Oriented amylose fibers in the V form were prepared and subjected to x-ray analysis. Unit cells and the probable space group of P212121 were determined for the V anhydrous and V hydrate forms of amylose; the analysis confirms previous predictions of these structures based on x-ray powder patterns. Chain folding in V amyloses is discussed in view of crystallographic evidence and folding experiments conducted with space-filling models. Reported also is evidence for amylose helices having diameters intermediate between 13.0 and 13.7 A. 相似文献
5.
EFFECTS OF KAINIC ACID ON ION DISTRIBUTION AND ATP LEVELS OF STRIATAL SLICES INCUBATED IN VITRO 总被引:10,自引:10,他引:0
Abstract— To determine the mechanism of neurotoxicity of kainic acid, striatal slices (350μ) were incubated in oxygenated Krebs buffer with kainic acid and other depolarizing agents; and the alterations in the uptake and retention of 22Na+, 86Rb+ (as a measure of K +), 3HzO and the levels of ATP were determined. The excitatory amino acid, L-glutamate (10 mM) increases striatal slice uptake and retention of Na+, K+ and H2O but decreases ATP levels whereas the neuroexcitant, A'-methyl aspartate, increases only Na+ and H2O. Veratridine (100μM), which opens electrogenic sodium channels, and ouabain (100μM), which inhibits Na+-K+ ATPase, both elevate striatal Na+ and H2O but considerably reduce K+ and ATP. The effects of these different depolarizing agents on the parameters examined are consistent with their mechanisms of actions and support the validity of this in vitro method. Although 10mM-kainate significantly depresses striatal K+ and ATP, lower concentrations of kainate (5mM-0.1μ) elevate striatal uptake of Na+ but do not markedly affect H2O, K+ or ATP. Kainate (10mM-lμM) does not exhibit additivity with 10 mM-glutamate with respect to Na+ permeability but does significantly potentiate glutamate's ATP depleting effects. Injection of 10 nmol of kainate into the striatum in vivo causes a reduction in striatal ATP 1 h afterward which is comparable to that occurring in vitro with 10mM-kainate alone or with lower concentrations of kainate (≥1/μM) with 10 mM-glutamate. These results suggest that kainate alone is directly neurotoxic at 10mM or neurotoxic at lower concentrations in combination with the high intrasynaptic levels of glutamate on neurons receiving glutamatergic innervation. 相似文献
6.
Thomas Zeuthen 《The Journal of membrane biology》1982,66(1):109-121
Summary The interactions between ion and water fluxes have an important bearing on osmoregulation and transepithelial water transport in epithelial cells. Some of these interactions were investigated using ion-selective microelectrodes in theNecturus gallbladder. The intracellular activities of K+ and Cl– in epithelial cells change when the epithelium is adapted to transport in solutions of a low osmolarity. In order to achieve new steady states at low osmolarities, cells lost K+, Cl– and some unidentified anions. Surprisingly, the apparent K+ concentration remained high: at an external osmolartity of 64 mOsm the intracellular K+ concentration averaged 95mm. This imbalance was sensitive to anoxia and ouabain. The effects of abrupt changes in the external osmolarities on the intracellular activities of Na+, K+ and Cl– were also investigated. The gradients were effectuated by mannitol. The initial relative rates of change of the intracellular activities of Na+ and Cl– were equal. The data were consistent with Na+ and Cl– ions initially remaining inside the cell and a cell membraneL
p
of 10–3 cm sec–1 osm–1, which is close to the values determine by Spring and co-workers (K.R. Spring, A. Hope & B.-E. Persson, 1981.In: Water Transport Across Epithelia. Alfred Benzon Symposium 15. pp. 190–200. Munskgaard, Copenhagen). The initial rate of change of the intracellular activity of K+ was only 0.1–0.2 times the change observed in Na+ and Cl– activities, and suggests that K+ ions leave the cell during the osmotically induced H2O efflux and enter with an induced H2O influx. The coupling is between 98 and 102 mmoles liter–1. Various explanations for the anomalous behavior of intracellular K+ ions are considered. A discussion of the apparent coupling between K+ and H2O, observed in nonsteady states, and its effects on the distribution of K+ and H2O across the cell membrane in the steady states, is presented. 相似文献
7.
8.
The efficacy and mechanism of -dendrotoxin (DTX) block of K+ channel currents in Vicia stomatal guard cells was examined. Currents carried by inward- and outward-rectifying K+ channels were determined under voltage clamp in intact guard cells, and block was characterized as a function of DTX and external K+ (K+) concentrations. Added to the bath, 0.1-30 nM DTX blocked the inward-rectifying K+ current (IK,in), but was ineffective in blocking current through the outward-rectifying K+ channels (IK,out) even at concentrations of 30 nM. DTX block was independent of clamp voltage and had no significant effect on the voltage-dependent kinetics for IK,in, neither altering its activation at voltages negative of –120 mV nor its deactivation at more positive voltages. No evidence was found for a use dependence to DTX action. Block of IK,in followed a simple titration function with an apparent K1/2 for block of 2.2 nM in 3 mm K
o
+
. However, DTX block was dependent on the external K+ concentration. Raising K+ from 3 to 30 mm slowed block and resulted in a 60–70% reduction in its efficacy (apparent K
i
= 10 mm in 10 nm DTX). The effect of K+ in protecting I
K,in
was competitive with DTX and specific for permeant cations. A joint analysis of IK,in block with DTX and K+ concentration was consistent with a single class of binding sites with a K
d
for DTX of 240 pm. A K
d
of 410 m for extracellular K+ was also indicated. These results complement previous studies implicating a binding site requiring extracellular K+ (K1/2 1 mm) for IK,in activation; they parallel features of K+ channel block by DTX and related peptide toxins in many animal cells, demonstrating the sensitivity of plant plasma membrane K+ channels to nanomolar toxin concentrations under physiological conditions; the data also highlight one main difference: in the guard cells, DTX action appears specific to the K+ inward rectifier.We thank J.O. Dolly (Imperial, London) and S.M. Jarvis (University of Kent, Canterbury) for several helpful discussions. This work was supported by SERC grant GR/H07696 and was aided by equipment grants from the Gatsby Foundation, the Royal Society and the University of London Central Research Fund. G.O. was supported by an Ausbildungsstipendium (OB 85/1-1) from the Deutsche Forschungsgemeinschaft. F.A. holds a Sainsbury Studentship. 相似文献
9.
Summary. Patch-clamp whole-cell and single-channel recording techniques were used to investigate the regulation of outward K+ channels by external and internal protons in Brassica chinensis pollen protoplasts. Outward K+ currents and conductance were insensitive to external pH (pHo) except at pH 4.5. Maximal conductance (G
max) for the outward K+ currents was inhibited at acidic external pH. Half-activation voltage (E
1/2) for the outward K+ currents shifted to more positive voltages along with the decrease in pHo. E
1/2 can be described by a modified Henderson–Hasselbalch equation expected from a single titratable binding site. The activation
kinetics of the outward K+ channels was largely insensitive to pHo. An internal pH (pHi) of 4.5 significantly increased outward K+ currents and conductance. G
max for the outward K+ currents decreased with elevations in pHi. In contrast to the effect of pHo, E
1/2 was shifted to more positive voltages with elevations in pHi. The outward K+ currents, G
max and E
1/2 can be described by the modified Henderson–Hasselbalch equation. Furthermore, acidifying pHi accelerated the activation of the outward K+ currents significantly. The differences in electro-physiological properties among previously reported and currently described
plant outward K+ channels may reflect differences in the structure of these channels.
Received May 7, 2002; accepted July 9, 2002; published online November 29, 2002 相似文献
10.
Effects of ammonium on the photosynthetic recovery of Nostoc flagelliforme Berk. et M. A. Curtis were assayed when being rehydrated in low‐K+ or high‐K+ medium. Its photosynthetic recovery was K+ limited after 3 years of dry storage. The potassium absorption of N. flagelliforme reached the maximum after 3 h rehydration in low‐K+ medium but at 5 min in high‐K+ medium. The K+ content of N. flagelliforme rehydrated in high‐K+ medium was much higher than that in low‐K+ medium. The maximal PSII quantum yield (Fv/Fm) value of N. flagelliforme decreased significantly when samples were rehydrated in low‐K+ medium treated with 5 mM NH4Cl. However, the treatment of 20 mM NH4Cl had little effect on its Fv/Fm value in high‐K+ medium. The relative Fv/Fm 24 h EC50 (concentration at which 50% inhibition occurred) value of NH4+ in high‐K+ medium (64.35 mM) was much higher than that in low‐K+ medium (22.17 mM). This finding indicated that high K+ could alleviate the inhibitory action of NH4+ upon the photosynthetic recovery of N. flagelliforme during rehydration. In the presence of 10 mM tetraethylammonium chloride (TEACl), the relative Fv/Fm 24 h EC50 value of NH4+ was increased to 46.34 and 70.78 mM, respectively, in low‐K+ and high‐K+ media. This observation suggested that NH4+ entered into N. flagelliforme cells via the K+ channel. Furthermore, NH4+ could decrease K+ absorption in high‐K+ medium. 相似文献
11.
Kukita F 《The Journal of membrane biology》2011,242(3):119-135
In hypertonic solutions made by adding nonelectrolytes, K+ channels of squid giant axons opened at usual asymmetrical K+ concentrations in two different time courses; an initial instantaneous activation (I
IN) and a sigmoidal activation typical of a delayed rectifier K+ channel (I
D). The current–voltage relation curve for I
IN was fitted well with Goldman equation described with a periaxonal K+ concentration at the membrane potential above −10 mV. Using the activation–voltage curve obtained from tail currents, K+ channels for I
IN are confirmed to activate at the membrane potential that is lower by 50 mV than those for I
D. Both I
IN and I
D closed similarly at the holding potential below −100 mV. The logarithm of I
IN/I
D was linearly related with the osmolarity for various nonelectrolytes. Solute inaccessible volumes obtained from the slope
increased with the nonelectrolyte size from 15 to 85 water molecules. K+ channels representing I
D were blocked by open channel blocker tetra-butyl ammonium (TBA) more efficiently than in the absence of I
IN, which was explained by the mechanism that K+ channels for I
D were first converted to those for I
IN by the osmotic pressure and then blocked. So K+ channels for I
IN were suggested to be derived from the delayed rectifier K+ channels. Therefore, the osmotic pressure is suggested to exert delayed-rectifier K+ channels to open in shrinking rather hydrophilic flexible parts outside the pore than the pore itself, which is compatible
with the recent structure of open K+ channel pore. 相似文献
12.
The objective have been to establish if those ions which are known to change the stability of the structure of proteins, have any influence on the properties of ionizable polypeptides. Potentiometric titrations and complementary optical rotation data are presented for aqueous solutions of poly-L -lysine (PLL) in the presence of KSCN, KCl, and KF, and for poly(L -glutamic acid) (PLGA) in the presence of KSCN, KCl, and LiCl. The following measured quantities which are affected by salt concentration were obtained: intrinsic pK (pK0), slope of pKapp versus degree of ionization (α) curves, the degree of ionization at which the helix to coil transition occurs, and the free energy of this transition for the uncharged molecule (δG°hel). The effects of nonspecific salts (KCl and LiCl for PLL and KSCN and KCl for PLGA) are small, and about, as expected from general electrostatic considerations. In line with the observations made with isoelectric and cat ionic collagen, specific, effects were noted with KSCN–PLL and with LiCl–PLGA. In the presence of KSCN, the poly-L -lysine helix becomes stabilized at much lower degree of ionization than in the presence of KCl, and the slope of the pKapp versus α plots is greatly reduced. However, ΔG°hel (for the uncharged molecule) is not affected, and pK0 is only slightly higher. We interpret these data in terms of binding of SCN? primarily to the side-chain amino groups (both to R? NH3+ and to R? NH2) solutions. (L -glutamic acid) in LiCl solution has its transition at the same α value as in KCl solution. However, both the slopes of the pKapp versus α plots and the absolute values of ΔG°hel are lower than in KCl solution. We interpret these results in terms of binding of Li+ to side chains as well as to the peptide bond. 相似文献
13.
SYLVIA LINDBERG 《Physiologia plantarum》1980,48(1):65-70
A microsomal (Na++ K++ Mg2+)ATPase preparation from sugar beet roots was used. The activation by simultaneous addition of Na+ and K+ at different levels was examined in terms of steady state kinetics. The observed data can be summarized in the following way: 1. The apparent affinity between the enzyme and the substrate MgATP depends on the ratio between Na+ and K+. At low Na+ concentration (below 5 mM), the apparent Km decreases with increasing concentrations of K+ (1–20 mM). At 5 mM Na+, the K+ level does not change the apparent Km, while at Na+ levels above 10 mM, the apparent Km between enzyme and substrate increases with increasing concentration of K+. 2. When the MgATP concentration is kept constant, homotropic cooperativity (concerning one type of ligand) and heterotropic cooperativity (concerning different types of ligands) exist in the activation by Na+ and K+. The Na+ binding is cooperative with different Km values and Hill coefficients (n) in the presence of low and high concentration of K+. At low Na+ level (< 5 mM). a negative cooperativity exists for Na+ (nNa < 1) which is more pronounced in the presence of high [K+]. When the concentration of Na+ is raised the negative cooperativity disappears and turns into a positive one (nNa > 1). Only K+ binding in the presence of low [Na+] shows cooperativity with a Hill coefficient that reflects changes from negative to positive homotropic cooperativity with increasing concentrations of K+ (nK < 1 → nK > 1). In the presence of [Na+] > 10 mM, the changes in nk are insignificant. 3. A model is proposed in which one or two different K sites and one or two Na sites control the catalytic activity, with multiple interactions between Na+, K+ and MgATP. 4. In the presence of Na+ (< 10 mM), K+ is probably bound to two K sites, one of which translocates K+ through the membrane by an antiport Na+/K+ mechanism. This could be connected with an elevated K+ uptake in the presence of Na+ and could therefore explain some field properties of sugar beets. 相似文献
14.
Elongation of subapical segments of maize (Zea mays) roots was greatly inhibited by 2H2O in the incubation medium. Short-term exposure (30 min) to 2H2O slightly reduced O2 uptake and significantly increased ATP levels. 2H2O inhibited H+ extrusion in the presence of both low (0.05 mm) and high (5 mm) external concentrations of K+ (about 30 and 53%, respectively at 50% [v/v] 2H2O). Experiments on plasma membrane vesicles showed that H+-pumping and ATPase activities were greatly inhibited by 2H2O (about 35% at 50% [v/v] 2H2O); NADH-ferricyanide reductase and 1,3-β-glucan synthase activities were inhibited to a lesser extent (less than 15%). ATPase activities present in both the tonoplast-enriched and submitochondrial particle preparations were not affected by 2H2O. Therefore, the effect of short incubation time and low concentration of 2H2O is not due to a general action on overall cell metabolism but involves a specific inhibition of the plasma membrane H+ -ATPase. K+ uptake was inhibited by 2H2O only when K+ was present at a low (0.05 mm) external concentration where absorption is against its electrochemical potential. The transmembrane electric potential difference (Em) was slightly hyperpolarized by 2H2O at low K+, but was not affected at the higher K+ concentrations. These results suggest a relationship between H+ extrusion and K+ uptake at low K+ external concentration. 相似文献
15.
Horst Helbig Christoph Korbmacher Michael Wiederholt 《The Journal of membrane biology》1987,99(3):173-186
Summary Using intracellular microelectrode technique, we investigated the changes in membrane voltage (V) of cultured bovine pigmented ciliary epithelial cells induced by different extracellular solutions. (1)V in 213 cells under steady-state conditions averaged –46.1±0.6 mV (sem). (2) Increasing extracellular K+ concentration ([K+]
o
) depolarizedV. Addition of Ba2+ could diminish this response. (3) Depolarization on doubling [K+]
o
was increased at higher [K+]
o
(or low voltage). (4) Removing extracellular Ca2+ decreasedV and reduced theV amplitude on increasing [K+]
o
. (5)V was pH sensitive. Extra-and intracellular acidification depolarizedV; alkalinization induced a hyperpolarization.V responses to high [K+]
o
were reduced at acidic extracellular pH. (6) Removing K
o
+
depolarized, K
o
+
readdition after K+ depletion transiently hyperpolarizedV. These responses were insensitive to Ba2+ but were abolished in the presence of ouabain or in Na+-free medium. (7) Na+ readdition after Na+ depletion transiently hyperpolarizedV. This reaction was markedly reduced in the presence of ouabain or in K+-free solution but unchanged by Ba2+. It is concluded that in cultured bovine pigmented ciliary epithelial cells K+ conductance depends on Ca2+, pH and [K+]
o
(or voltage). An electrogenic Na+/K+-transport is present, which is stimulated during recovery from K+ or Na+ depletion. This transport is inhibited by ouabain and in K+-or Na+-free medium. 相似文献
16.
Yasuyuki Tezuka 《Biopolymers》1994,34(11):1477-1482
Nuclear Overhauser effect spectroscopy measurements on cellulose triacetate and on amylose triacetate with a mixing time of 500 ms, on the order of T1, of acetyl protons, were performed to detect the specific through-space interaction between acetyl groups arising from their helix structures in solution. For cellulose triacetate, cross peaks were detected in CDCl3 between acetyl proton signals at 3 and 6 positions on an anhydroglucose unit. In DMSO-d6, on the other hand, correlation peaks were observed not only between the 3 and 6 positions but also the 2 and 6 positions. For amylose triacetate, cross peaks were detected in CDCl3 between the acetyl proton signals at the 2 and 6 positions. The through-space interaction of acetyl groups in cellulose triacetate and in amylose triacetate in solution was then interpreted based on their three-dimensional structures in solid state determined by x-ray crystallography. © 1994 John Wiley & Sons, Inc. 相似文献
17.
18.
Kethika Kulleperuma Susan M.E. Smith Deri Morgan Boris Musset John Holyoake Nilmadhab Chakrabarti Vladimir V. Cherny Thomas E. DeCoursey Régis Pomès 《The Journal of general physiology》2013,141(4):445-465
The topological similarity of voltage-gated proton channels (HV1s) to the voltage-sensing domain (VSD) of other voltage-gated ion channels raises the central question of whether HV1s have a similar structure. We present the construction and validation of a homology model of the human HV1 (hHV1). Multiple structural alignment was used to construct structural models of the open (proton-conducting) state of hHV1 by exploiting the homology of hHV1 with VSDs of K+ and Na+ channels of known three-dimensional structure. The comparative assessment of structural stability of the homology models and their VSD templates was performed using massively repeated molecular dynamics simulations in which the proteins were allowed to relax from their initial conformation in an explicit membrane mimetic. The analysis of structural deviations from the initial conformation based on up to 125 repeats of 100-ns simulations for each system reveals structural features consistently retained in the homology models and leads to a consensus structural model for hHV1 in which well-defined external and internal salt-bridge networks stabilize the open state. The structural and electrostatic properties of this open-state model are compatible with proton translocation and offer an explanation for the reversal of charge selectivity in neutral mutants of Asp112. Furthermore, these structural properties are consistent with experimental accessibility data, providing a valuable basis for further structural and functional studies of hHV1. Each Arg residue in the S4 helix of hHV1 was replaced by His to test accessibility using Zn2+ as a probe. The two outermost Arg residues in S4 were accessible to external solution, whereas the innermost one was accessible only to the internal solution. Both modeling and experimental data indicate that in the open state, Arg211, the third Arg residue in the S4 helix in hHV1, remains accessible to the internal solution and is located near the charge transfer center, Phe150. 相似文献
19.
Jochen Duhm 《The Journal of membrane biology》1987,98(1):15-32
Summary The effect of extracellular and intracellular Na+ (Na
o
+
, Na
i
+
) on ouabain-resistant, furosemide-sensitive (FS) Rb+ transport was studied in human erythrocytes under varying experimental conditions. The results obtained are consistent with the view that a (1 Na++1 K++2 Cl–) cotransport system operates in two different modes: modei) promoting bidirectional 11 (Na+–K+) cotransport, and modeii) a Na
o
+
-independent 11 K
o
+
/K
i
+
exchange requiring Na
i
+
which, however, is not extruded. The activities of the two modes of operation vary strictly in parallel to each other among erythrocytes of different donors and in cell fractions of individual donors separated according to density. Rb+ uptake through Rb
o
+
/K
i
+
exchange contributes about 25% to total Rb+ uptake in 145mm NaCl media containing 5mm RbCl at normal Na
i
+
(pH 7.4). Na+–K+ cotransport into the cells occurs largely additive to K+/K+ exchange. Inward Na+–Rb+ cotransport exhibits a substrate inhibition at high Rb
o
+
. With increasing pH, the maximum rate of cotransport is accelerated at the expense of K+/K+ exchange (apparent pK close to pH 7.4). The apparentK
m
Rb
o
+
of Na+–K+ cotransport is low (2mm) and almost independent of pH, and high for K+/K+ exchange (10 to 15mm), the affinity increasing with pH. The two modes are discussed in terms of a partial reaction scheme of (1 Na++1 K++2 Cl–) cotransport with ordered binding and debinding, exhibiting a glide symmetry (first on outside = first off inside) as proposed by McManus for duck erythrocytes (McManus, T.J., 1987,Fed. Proc., in press). N-ethylmaleimide (NEM) chemically induces a Cl–-dependent K+ transport pathway that is independent of both Na
o
+
and Na
i
+
. This pathway differs in many properties from the basal, Na
o
+
-independent K+/K+ exchange active in untreated human erythrocytes at normal cell volume. Cell swelling accelerates a Na
o
+
-independent FS K+ transport pathway which most probably is not identical to basal K+/K+ exchange. K
o
+
o
+
o
+
o
2+
reduce furosemide-resistant Rb+ inward leakage relative to choline
o
+
. 相似文献
20.
Azadirachtin (Az), as a botanical insecticide, is relatively safe and biodegradable. It affects a wide vaariety of biological
processes, including the reduction of feeding, suspension of molting, death of larvae and pupae, and sterility of emerged
adults in a dose-dependent manner. However, the mode of action of this toxin remains obscure. By using ion chromatography,
we analyzed changes in six inorganic cation (Li+, Na+, NH4
+, K+, Mg2+, and Ca2+) distributions of the whole body and hemolymph in Ostrinia furnacalis (G.) after exposure to sublethal doses of Az. The results showed that Az dramatically interfered with Na+, NH4
+, K+, Mg2+, and Ca2+ distributions in hemolymph of O. furnacalis (G.) and concentrations of these five cations dramatically increased. However, in the whole body, the levels of K+, Mg2+, and Ca2+ significantly, decreased after exposure to Az, except that Na+ and NH4
+ remained constant. Li+ was undetected in both the control and treated groups in the whole body and hemolymph. It is suggested that Az exerts its
insecticidal effects on O. furnacalis (G.) by interfering with the inorganic cation distributions related to ion channels. 相似文献