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1.
Nanosilver of 10-nm size was prepared by the NaBH4–sodium citrate procedure, and it was modified by a single-strand DNA (ssDNA) aptamer to fabricate an AgssDNA probe for melamine.
The probe was stabile at pH 7.0 Na2HPO4–NaH2PO4 buffer solutions and in the presence of 25.0 mmol/L NaCl. Upon the addition of melamine, it interacted with the probe to
aggregate big clusters, which led to the resonance scattering (RS) intensity at 470 nm increasing greatly. Under the selected
conditions, the increased RS intensity (ΔI
470 nm) is linear to melamine concentration in the range of 6.31–378.4 μg/L, with a regression equation of DI470 nm = 1.124c + 10.8 \Delta {I_{{47}0{\rm{ nm}}}} = {1}.{124}c + { 10}.{8} and a detection limit of 3.1 μg/L. The aptamer-modified nanosilver RS assay has been applied for the determination of melamine
in milk, with satisfactory results. 相似文献
2.
Nanogold of 10 nm was used to label carcinoembryonic antigen antibody (CEAAb) to prepare a probe (Au-CEAAb) for carcinoembryonic
antigen (CEA). In a Na2HPO4–NaH2PO4 buffer solution of pH 6.8, CEA reacted with Au-CEAAb to form a big Au-CEAAb–CEA immunocomplex that can be removed by centrifugation.
The unreacted Au-CEAAb in the centrifugal supernatant exhibited catalytic effect on the Cu2O particle reaction, and the Cu2O particles displayed a resonance scattering (RS) peak at 602 nm. When CEA increased, the RS intensity at 602 nm decreased,
and the decreased RS intensity (ΔI
602 nm) was linear to CEA concentration (C
CEA) in the range of 0.02–12 ng mL−1, with the regression equation of ΔI
602 nm = 27.1 C
CEA + 3.3, correlation coefficient of 0.9978 and detection limit of 3 pg mL−1 CEA. The proposed method was applied to detect CEA in real samples, with satisfactory results. 相似文献
3.
Zhiliang Jiang Yanyan Fan Aihui Liang Guiqing Wen Qingye Liu Tingsheng Li 《Plasmonics (Norwell, Mass.)》2010,5(4):375-381
The resonance scattering spectral probe for Pb2+ was obtained using aptamer-modified AuPd Nanoalloy. In the pH 7.0 Na2HPO4–NaH2PO4 buffer solution, the aptamer interacted with AuPd nanoalloy particles to form stable aptamer-AuPd nanoalloy probe for Pb2+ that is stable in high concentration of salt. The probe combined with Pb2+ ions to form a G-quadruplex and to release AuPd nanoalloy particles that aggregate to form big particles which led the resonance
scattering (RS) intensity enhancing. The reaction solution was filtered by 0.15 μm membrane to obtain the filtration containing
aptamer-AuPd nanoalloy probe that has strong catalytic effect on the electrodeless nickel particle plating reaction between
Ni(II) and PO23− that exhibited a strong RS peak at 508 nm. The RS intensity at 508 nm decreased when the Pb2+ concentration increased. The decreased intensity (ΔI
508nm) is linear to the concentration of 0.08–42 nM Pb2+, with regress equation of DI508nm = 16.3 c + 1.5 \Delta {I_{{5}0{\rm{8nm}}}} = {16}.{3}\,c + {1}.{5} , correlation coefficient of 0.9965, and detection limit of 0.04 nM Pb2+. The RS assay was applied to the analysis of Pb2+ in wastewater, with satisfactory results. 相似文献
4.
Huilin Tao Lili Wei Aihui Liang Jianfu Li Zhiliang Jiang Hesheng Jiang 《Plasmonics (Norwell, Mass.)》2010,5(2):189-198
Gold nanoparticle particles in size of 10 nm were used to label the thiol-modified single-stranded DNA aptamer (SH-ssDNA)
to obtain an aptamer-modified gold nanoparticle probe (AussDNA) for target DNA (tDNA). In pH 7.4 NaH2PO4–Na2HPO4 buffer solution, the hybridization reaction between AussDNA and tDNA took place to form larger aptamer-modified gold nanoparticle
cluster complex. The excess aptamer-modified gold nanoparticle probe in the supernatant solutions was obtained by centrifuging
and can be used as nanocatalyst for the 0.276 mmol/L CuSO4-65.4 mmol/L potassium-sodium tartrate-0.37 mmol/L glucose system at 70 °C. The cubic Cu2O particles generated by the nanocatalytic reducing exhibit a strong resonance scattering (RS) peak at 620 nm. In the selected
conditions, the RS intensity at 620 nm decreased with addition of tDNA, and the decreased intensity ΔI
620 nm is proportional to tDNA concentration (C
tDNA) from 0.12 to 72 pM, with regress equation of ΔI
620 nm = 1.29C
tDNA + 4.05, correlation coefficient of 0.9917, and detection limit of 0.084 pM tDNA. 相似文献
5.
Aihui Liang Jishun Li Caina Jiang Zhiliang Jiang 《Bioprocess and biosystems engineering》2010,33(9):1087-1094
The gold-rhenium (AuRe) composite nanoparticle was prepared by NaBH4 reduction procedure, and was modified by the aptamer to obtain an AuRe nanoprobe (AuRessDNA) for thrombin. In pH 7.0 Tris–HCl
buffer solution and in the presence of salt, the nanoprobe specifically combined with thrombin to form AuRe-aptamer-thrombin
cluster that resulted in the resonance scattering intensity (I
560 nm) increasing at 560 nm. The increased intensity ΔI
560 nm was linear to the thrombin concentration in the range of 0.115–6.93 nmol/L, with a regression equation of ΔI
560 nm = 53.0 C + 2.5, a correlation coefficient of 0.9989, and a detection limit of 13 pmol/L. This method was applied to detect thrombin
in human plasma samples, with satisfactory results. 相似文献
6.
In the medium of H2SO4 and in the presence of TiO2+, gold nanoparticles in size of 10 nm exhibited a weak surface plasmon resonance scattering (SPRS) peak at 775 nm. Upon addition
of trace H2O2, the yellow complex [TiO(H2O2)]2+ formed that cause the gold nanoparticles aggregations to form bigger gold nanoparticle clusters in size of about 900 nm,
and the SPRS intensity at 775 nm (I) enhanced greatly. The enhanced intensity ΔI was linear to the H2O2 concentration in the range of 0.025–48.7 μg/mL, with a detection limit of 0.014 μg/mL H2O2. This SPRS method was applied to determining H2O2 in water samples with satisfactory results. 相似文献
7.
Elevation of the external potassium concentration induced a two-phase inward current in freshly isolated pyramidal hippocampal
neurons. This current was voltage-dependent and demonstrated strong inward rectification. The current consisted of a leakage
current and a time-dependent current (τ=40–50 msec at 21°C); the latter was designated asI
ΔK. As was shown earlier, K+ is a major charge carrier in the development of slow potassium-activated current. The pharmacological properties ofI
ΔK were studied using a patch-clamp technique.I
ΔK was completely blocked by external 10 mM TEA or 5 mM Ba2+ (IC50=480±90mM) and exhibited low sensitivity to extracellular Cs+ (2 mM). This current was not affected by 1 mM 4-aminopyridine and was insensitive to a muscarinic agonist, carbachol (50
μM), and to 1 mM extracellular Cd2+. Elevation of external Ca2+ from 2.5 mM to 10 mM did not changeI
ΔK. Our data indicate that the pharmacological properties ofI
ΔK differ from those of other voltage-gated potassium currents, but more specific blockers must be used to make this evidence
conclusive. 相似文献
8.
By simultaneously analyzing the chlorophyll a fluorescence transient and light absorbance at 820 nm as well as chlorophyll fluorescence quenching, we investigated the
effects of different photon flux densities (0, 15, 200 μmol m−2 s−1) with or without 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) on the repair process of cucumber (Cucumis sativus L.) leaves after treatment with low temperature (6°C) combined with moderate photon flux density (200 μmol m−2 s−1) for 6 h. Both the maximal photochemical efficiency of Photosystem II (PSII) (F
v/F
m) and the content of active P700 (ΔI/I
o) significantly decreased after chilling treatment under 200 μmol m−2 s−1 light. After the leaves were transferred to 25°C, F
v/F
m recovered quickly under both 200 and 15 μmol m−2 s−1 light. ΔI/I
o recovered quickly under 15 μmol m−2 s−1 light, but the recovery rate of ΔI/I
o was slower than that of F
v/F
m. The cyclic electron transport was inhibited by chilling-light treatment obviously. The recovery of ΔI/I
o was severely suppressed by 200 μmol m−2 s−1 light, whereas a pretreatment with DCMU effectively relieved this suppression. The cyclic electron transport around PSI recovered
in a similar way as the active P700 content did, and the recovery of them was both accelerated by pretreatment with DCMU.
The results indicate that limiting electron transport from PSII to PSI protected PSI from further photoinhibition, accelerating
the recovery of PSI. Under a given photon flux density, faster recovery of PSII compared to PSI was detrimental to the recovery
of PSI or even to the whole photosystem. 相似文献
9.
The responses of freshly isolated hippocampal pyramidal neurons to rapid, elevations of the external potassium concentration
([K+]
out
) were investigated using the whole-cell variation of a patch-clamp technique. An elevation of [K+]
out
induced a two-phase inward current at the membrane potentials more negative than the reversal potential for K ions. This
current consisted of a leakage, current and a time-dependent current (τ=40–50 msec at 21°C), the latter designated below asI
ΔK. It displayed first-order activation kinetics that showed neither voltage, nor concentration dependence. The amplitude of
this current was determined by the external K+ concentration and increased with hyperpolarization. Voltage dependence ofI
ΔK measured within the range from −20 to −120 mV was similar to that for inward rectifier. Activation ofI
ΔK was utterly dependent on Na+; substitution of extracellular Na+ with choline chloride almost completely depressedI
ΔK.I
ΔK was absent in the cells freshly dissociated from the nodosal and dorsal root ganglia. This suggests that this earlier unrecognized
current is instrumental in preserving densely packed hippocampal pyramidal neurons from sudden increases in [K+]
out
and following spontaneous over-excitation. It prevents the neurons from responding to K+-induced depolarizations by slowing down potassium influx. 相似文献
10.
Renata Matraszek 《Acta Physiologiae Plantarum》2008,30(3):361-370
The author studied the effect of different nickel concentrations (0, 0.4, 40 and 80 μM Ni) on the nitrate reductase (NR) activity
of New Zealand spinach (Tetragonia expansa Murr.) and lettuce (Lactuca sativa L. cv. Justyna) plants supplied with different nitrogen forms (NO3
−–N, NH4
+–N, NH4NO3). A low concentration of Ni (0.4 μM) did not cause statistically significant changes of the nitrate reductase activity in
lettuce plants supplied with nitrate nitrogen (NO3
−–N) or mixed (NH4NO3) nitrogen form, but in New Zealand spinach leaves the enzyme activity decreased and increased, respectively. The introduction
of 0.4 μM Ni in the medium containing ammonium ions as a sole source of nitrogen resulted in significantly increased NR activity
in lettuce roots, and did not cause statistically significant changes of the enzyme activity in New Zealand spinach plants.
At a high nickel level (Ni 40 or 80 μM), a significant decrease in the NR activity was observed in New Zealand spinach plants
treated with nitrate or mixed nitrogen form, but it was much more marked in leaves than in roots. An exception was lack of
significant changes of the enzyme activity in spinach leaves when plants were treated with 40 μM Ni and supplied with mixed
nitrogen form, which resulted in the stronger reduction of the enzyme activity in roots than in leaves. The statistically
significant drop in the NR activity was recorded in the aboveground parts of nickel-stressed lettuce plants supplied with
NO3
−–N or NH4NO3. At the same time, there were no statistically significant changes recorded in lettuce roots, except for the drop of the
enzyme activity in the roots of NO3
−-fed plants grown in the nutrient solution containing 80 μM Ni. An addition of high nickel doses to the nutrient solution
contained ammonium nitrogen (NH4
+–N) did not affect the NR activity in New Zealand spinach plants and caused a high increase of this enzyme in lettuce organs,
especially in roots. It should be stressed that, independently of nickel dose in New Zealand spinach plants supplied with
ammonium form, NR activity in roots was dramatically higher than that in leaves. Moreover, in New Zealand spinach plants treated
with NH4
+–N the enzyme activity in roots was even higher than in those supplied with NO3
−–N. 相似文献
11.
R. Thomas James Wayne S. Gardner Mark J. McCarthy Stephen A. Carini 《Hydrobiologia》2011,669(1):199-212
Total nitrogen (TN) in Lake Okeechobee, a large, shallow, turbid lake in south Florida, has averaged between 90 and 150 μM
on an annual basis since 1983. No TN trends are evident, despite major storm events, droughts, and nutrient management changes
in the watershed. To understand the relative stability of TN, this study evaluates nitrogen (N) dynamics at three temporal/spatial
levels: (1) annual whole lake N budgets, (2) monthly in-lake water quality measurements in offshore and nearshore areas, and
(3) isotope addition experiments lasting 3 days and using 15N-ammonium (15NH4
+) and 15N-nitrate (15NO3
−) at two offshore locations. Budgets indicate that the lake is a net sink for N. TN concentrations were less variable than
net N loads, suggesting that in-lake processes moderate these net loads. Monthly NO3
− concentrations were higher in the offshore area and higher in winter for both offshore and nearshore areas. Negative relationships
between the percentage of samples classified as algal blooms (defined as chlorophyll a > 40 μg l−1) and inorganic N concentrations suggest N-limitation. Continuous-flow experiments over intact sediment cores measured net
fluxes (μmol N m−2 h−1) between 0 and 25 released from sediments for NH4
+, 0–60 removed by sediments for NO3
−, and 63–68 transformed by denitrification. Uptake rates in the water column (μmol N m−2 h−1) determined by isotope dilution experiments and normalized for water depth were 1,090–1,970 for NH4
+ and 59–119 for NO3
−. These fluxes are similar to previously reported results. Our work suggests that external N inputs are balanced in Lake Okeechobee
by denitrification. 相似文献
12.
Rodney J. Fuller John G. Carman J. Richard Hess 《Plant Cell, Tissue and Organ Culture》2009,99(2):183-192
In vitro zygotic and somatic embryogenesis protocols rely on nutrient and hormone levels from media to satisfy the physiological
and developmental requirements of embryony. To better understand these requirements for cotton, we quantified levels of major
and minor elements, carbohydrates, NH4
+, free amino acids and six hormones in whole cotton ovules (with fibers removed), nucelli (ovules with integuments removed),
or ovule fluid (extracted from the endosperm region). Samples were collected from field-grown cotton at 1–18 days-past-anthesis
(DPA) during each of three growing seasons. Replication across 2 years was obtained for carbohydrates, NH4
+, free amino acids and hormones from nucellus samples. The year effect was large primarily for hormones only. The most abundant
minerals across tissue types and years were K, P, Mg and S. Potassium was the most abundant at 260, 600 and 1,660 mmol kg−1 dry mass (DM) in nucelli, whole ovules and ovule fluid, respectively. Magnesium, Ca, Zn and Mn levels were 2–8-fold higher
in ovule fluid compared to whole ovules or nucelli. In the free amino acid plus NH4
+ category, NH4
+, alanine, serine, glycine, asparagine (plus aspartic acid), glutamine (plus glutamic acid), leucine, threonine and arginine
predominated in nucelli and ovule fluid, and levels tended to be higher in the older samples across years and tissue types.
Fructose and glucose levels also increased with age with very high levels being found in late DPA ovule fluid. Arabinose,
inositol and melibiose were also prominent sugars. Indole-3-acetic acid levels were similar between nucelli and ovule fluid
and ranged from 10 to 80 μmol kg−1 DM. An abscisic acid spike, from 15 to 400 μmol kg−1 DM, occurred in nucelli and whole ovules from 2 to 8 DPA. Thereafter, abscisic acid levels remained between 5 and 10 μmol kg−1 DM. Zeatin and zeatin riboside were the most abundant cytokinins, and levels of these hormones fluctuated between 1 and 4 μmol kg−1 DM in both nucelli and ovule fluid. 相似文献
13.
Klaus Martin Meiners S. Papadimitriou D. N. Thomas L. Norman G. S. Dieckmann 《Polar Biology》2009,32(7):1055-1065
Physical, biogeochemical and photosynthetic parameters were measured in sea ice brine and ice core bottom samples in the north-western
Weddell Sea during early spring 2006. Sea ice brines collected from sackholes were characterised by cold temperatures (range
−7.4 to −3.8°C), high salinities (range 61.4–118.0), and partly elevated dissolved oxygen concentrations (range 159–413 μmol kg−1) when compared to surface seawater. Nitrate (range 0.5–76.3 μmol kg−1), dissolved inorganic phosphate (range 0.2–7.0 μmol kg−1) and silicic acid (range 74–285 μmol kg−1) concentrations in sea ice brines were depleted when compared to surface seawater. In contrast, NH4
+ (range 0.3–23.0 μmol kg−1) and dissolved organic carbon (range 140–707 μmol kg−1) were enriched in the sea ice brines. Ice core bottom samples exhibited moderate temperatures and brine salinities, but high
algal biomass (4.9–435.5 μg Chl a l−1 brine) and silicic acid depletion. Pulse amplitude modulated fluorometry was used for the determination of the photosynthetic
parameters F
v/F
m, α, rETRmax and E
k. The maximum quantum yield of photosystem II, F
v/F
m, ranged from 0.101 to 0.500 (average 0.284 ± 0.132) and 0.235 to 0.595 (average 0.368 ± 0.127) in the sea ice internal and
bottom communities, respectively. The fluorometric measurements indicated medium ice algal photosynthetic activity both in
the internal and bottom communities of the sea ice. An observed lack of correlation between biogeochemical and photosynthetic
parameters was most likely due to temporally and spatially decoupled physical and biological processes in the sea ice brine
channel system, and was also influenced by the temporal and spatial resolution of applied sampling techniques. 相似文献
14.
Dalila Serpa Manuela Falcão Pedro Duarte Luís Cancela da Fonseca Carlos Vale 《Biogeochemistry》2007,82(3):291-304
During an annual cycle, overlying water and sediment cores were collected simultaneously at three sites (Tavira, Culatra and
Ramalhete) of Ria Formosa’s intertidal muddy and subtidal sandy sediments to determine ammonium, nitrates plus nitrites and
phosphate. Organic carbon, nitrogen and phosphorus were also determined in superficial sediments. Ammonium and phosphate dissolved
in porewater were positively correlated with temperature (P < 0.01) in muddy and sandy sediments, while the nitrogen-oxidized forms had a negative correlation (P < 0.02) in muddy sediments probably because mineralization and nitrification/denitrification processes vary seasonally. Porewater
ammonium profiles evidenced a peak in the top-most muddy sediment (380 μM) suggesting higher mineralization rate when oxygen
is more available, while maximum phosphate concentration (113 μM) occurred in the sub-oxic layer probably due to phosphorus
desorption under reduced conditions. In organically poor subtidal sandy sediments, nutrient porewater concentrations were
always lower than in intertidal muddy sediments, ranging annually from 20 μM to 100 μM for ammonium and from 0.05 μM to 16 μM
for phosphate. Nutrient diffusive fluxes predicted by a mathematical model were higher during summer, in both muddy (104 nmol cm−2 d−1––NH4+; 8 nmol cm−2 d−1––HPO4−2) and sandy sediments (26 nmol cm−2 d−1––NH4+; 1 nmol cm−2 d−1––HPO4−2), while during lower temperature periods these fluxes were 3–4 times lower. Based on simulated nutrient effluxes, the estimated
annual amount of ammonium and phosphate exported from intertidal areas was three times higher than that released from subtidal
areas (22 ton year−1––NH4+; 2 ton year−1––HPO4−2), emphasizing the importance of tidal flats to maintain the high productivity of the lagoon. Global warming scenarios simulated
with the model, revealed that an increase in lagoon water temperature only produces significant variations (P < 0.05) for NH4+ in porewater and consequent diffusive fluxes, what will probably affect the system productivity due to a N/P ratio unbalance. 相似文献
15.
Responses to excessive ammonium (NH4
+) were compared between two Arabidopsis ecotypes (Col-0, JA22) with respect to different photoperiods in hydroponics. In this study, we showed that external extra
NH4
+ led to severe growth suppression, accumulations of free NH4
+ and amino acids and increased the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in shoots of
the two Arabidopsis ecotypes. However, the levels of free NH4
+ and total amino acids increased, whereas the activities of GS, NADH-dependent glutamate synthase and GDH decreased under
the continuous light when compared with the light (16 h)–dark (8 h) cycle photoperiod. Statistical analyses suggested that
strong correlations exist among the growth reduction, accumulations of free NH4
+, total amino acids and levels of GS activity in shoots under the high NH4
+ stress regardless of the photoperiod regimes. Interestingly, under the continuous light, Col-0 showed more resistant to such
growth reduction and maintained about onefold higher capability of converting excess free NH4
+ into amino acids, with onefold higher GS activity induced by the external NH4
+ when compared with JA22. In contrast, these differences were abolished between Col-0 and JA22 under the light–dark cycle
condition. Taken together, our results conclude that the sensitivity to NH4
+ of Col-0 and JA22 is changed between the continuous light and the light–dark cycle photoperiod, which is correlative to the
alteration of the GS activity in shoots. 相似文献
16.
The modelling of ion uptake by plants requires the measurement of kinetic and growth parameters under specific conditions.
The objective of this study was to evaluate the effect of nine NH
inf4
sup+
:NO
inf3
sup−
ratios on onions (Allium cepa L.). Twenty-eight to 84 day-old onion plants were treated with NH
inf4
sup+
:NOf3/sup− ratios ranging from 0 to 100% of each ionic species in one mM solutions in a growth chamber. Maximum N influx (Imax) was assessed using the N depletion method. Except at an early stage, ionic species did not influence significantly Imax, the Michaelis constant (Km) and the minimum concentration for net uptake (Cmin). Imax for ammonium decreased from 101 to 59 pmole cm-2 s-1 while Imax for nitrate increased from 26 to 54 pmole cm-2 s-1 as the plant matured. On average, Km and Cmin values were 14.29 μM, and 5.06 μM for ammonium, and 11.90 μM and 4.54 μM for nitrate, respectively. In general, the effect of NH4
+:NO3
- ratios on root weight, shoot weight and total weight depended on plant age. At an early stage, maximum plant growth and N
uptake were obtained with ammonium as the sole source of N. At later stages, maximum plant growth and N uptake were obtained
as the proportion of nitrate increased in the nutrient solution. The was no apparent nutrient deficiency whatever NH4
+:NO3
- ratio was applied, although ammonium reduced the uptake of cations and increased the uptake of phosphorus.
The research was supported by the Natural Sciences and Engineering Research Council of Canada. 相似文献
17.
Solntseva EI Bukanova JV Marchenko EV Rossokhin AV Skrebitsky VG 《Cellular and molecular neurobiology》2009,29(2):219-224
Earlier, we have shown a strong inhibitory effect of donepezil on K+-current of molluscan neurons (Solntseva et al., Comp Biochem Physiol 144, 319–326, 2007). In the present work, a possible
interaction of donepezil with the external mouth of the channel was examined using, as a tool, tetraethylammonium (TEA), a
classical antagonist of potassium channels. Experiments were conducted in isolated neurons of snail Helix aspersa using the
two-microelectrode voltage-clamp technique. A high-threshold slow-inactivating K+-current involving Ca2+-dependent (I
C) and Ca2+-independent (I
K) components was recorded. The I
C was estimated at 30 mV, and I
K at 100 mV. The IC50 values for blocking effect of donepezil on I
C varied from 5.0 to 8.9 μM in different cells. Corresponding values for I
K varied from 4.9 to 9.9 μM. The IC50 values for blocking effect of TEA on I
C lied in the range of 200 to 910 μM, and on I
K lied in the range of 100 to 990 μM. The comparison of the effects of donepezil and TEA on the same cells revealed significant
correlation between IC50 values of these effects. The value of Spearman coefficient of correlation (r) was 0.77 for I
C (P < 0.05), and 0.82 for I
K (P < 0.05). In the presence of TEA, the effect of donepezil, both on I
C and I
K, appears significantly weaker than in control solution. Dose–response curves of donepezil effect both on I
C and I
K were shifted right along horizontal axis when donepezil was applied in combination with TEA. Results suggest that TEA interferes
with donepezil and precludes the occupation by donepezil of its own site. We suppose that the site for donepezil is situated
near the TEA site with possible overlap. 相似文献
18.
We tested radioactive methylammonium (14CH3NH
inf3
sup+
) as a tracer for ammonium (NH4
+) in root uptake measurements from soil. Tomato (Lycopersicon esculentum Moll. cv T5) in 3 L pots filled with loamy sand soil received 40, 200, or 600 μmol 14CH3NH3
+ or 15NH4
+. During a 4 h period, the plants absorbed 14CH3NH3
+ at slower rates than 15NH4
+. Estimates of NH4
+ absorption based on 15NH4
+ absorption were 0.9–7.9 μmol NH4
+ g−1 plant dry weight h−1, whereas those based on 14CH3NH3
+ absorption were 0.2–1.0 μmol NH4
+ g−1 plant dry weight h−1. After 4 h, approximately one-half of the applied 15N was not recovered in the plants or soil KCl extracts; apparently, this 15N was either immobilized or nitrified and denitrified by soil biota. By contrast, almost all the 14CH3NH3
+ remained in the soil solution after 4 h, but after a 10 d incubation, approximately 20% had been released as 14CO2. These differences in plant absorption rates and movement through soil pools indicate that CH3NH3
+ cannot be used reliably as an NH4
+ analog in soil. 相似文献
19.
Sergey M. Korotkov 《Journal of bioenergetics and biomembranes》2009,41(3):277-287
It is known that permeability of the inner mitochondrial membrane is low to most univalent cations (K+, Na+, H+) but high to Tl+. Swelling, state 4, state 3, and 2,4-dinitrophenol (DNP)-stimulated respiration as well as the membrane potential (ΔΨmito) of rat liver mitochondria were studied in media containing 0–75 mM TlNO3 either with 250 mM sucrose or with 125 mM nitrate salts of other monovalent cations (KNO3, or NaNO3, or NH4NO3). Tl+ increased permeability of the inner mitochondrial membrane to K+, Na+, and H+, that was manifested as stimulation of the swelling of nonenergized and energized mitochondria as well as via an increase
of state 4 and dissipation of ΔΨmito. These effects of Tl+ increased in the order of sucrose <K+ <Na+ ≤ NH4+. They were stimulated by inorganic phosphate and decreased by ADP, Mg2+, and cyclosporine A. Contraction of energized mitochondria, swollen in the nitrate media, was markedly inhibited by quinine.
It suggests participation of the mitochondrial K+/H+ exchanger in extruding of Tl+-induced excess of univalent cations from the mitochondrial matrix. It is discussed that Tl+ (like Cd2+ and other heavy metals) increases the ion permeability of the inner membrane of mitochondria regardless of their energization
and stimulates the mitochondrial permeability transition pore in low conductance state. The observed decrease of state 3 and
DNP-stimulated respiration in the nitrate media resulted from the mitochondrial swelling rather than from an inhibition of
respiratory enzymes as is the case with the bivalent heavy metals. 相似文献
20.
Wei Cai Aihui Liang Qingye Liu Xianjiu Liao Zhiliang Jiang Guangyi Shang 《Luminescence》2011,26(5):305-312
ReAu nanoparticles with a molar ratio of 2:8 Re and Te nanoparticles were prepared by NaBH4 reduction. In HCl medium at 65°C, ultratrace Re, Te and ReAu bimetallic nanoparticles strongly catalyzed the slow reaction between Sn(II) and Te(VI) to form Te particles, which exhibited the strongest resonance scattering (RS) peak at 782 nm. As the amount of nanocatalyst increased, the RS intensity at 782 nm (I782 nm) increased linearly, and the increase in intensity ΔI782 nm was linear to the ReAu, Re and Te concentrations in the ranges 0.07–9.0, 0.01–4.5 and 30–1200 nm , respectively. As a model, a ReAu immunonanoprobe catalytic Te–particle resonance scattering spectral (RSS) method was established for detection of CA125, using ReAu nanoparticle labeling CA125 antibody (CA125Ab) to obtain an immunonanoprobe (ReAuCA125Ab) for CA125. In pH 7.6 citric acid–Na2HPO4 buffer solution, ReAuCA125Ab aggregated nonspecifically. Upon addition of CA125, the immunonanoprobe reacted with it to form ReAuCA125Ab–CA125 dispersive immunocomplex in the solution. After the centrifugation, the supernatant containing the immunocomplex was used to catalyze the reaction of Te(VI)–Sn(II) to produce the Te particles that resulted in the I782 nm increasing. The ΔI782 nm was linear to CA125 concentration (CCA125) in the range 0.1–240 mU/mL. The regression equation, correlation coefficient and detection limit were ΔI782 nm = 1.61 CCA125 + 1.5, 0.9978 and 0.02 mU/mL, respectively. The proposed method was applied to detect CA125 in serum samples, with satisfactory results. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献