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1.
Changes in the conformation of spinach thylakoid membranes were monitored in 5-doxyl stearic acid (SAL)-treated thylakoid
membranes in the presence of various anions (Cl−, Br−, I−, NO2
−, SO4
2−, PO4
3−). The presence of anions made the thylakoid membrane more fluid. The extent of change in membrane fluidity differed with
different anion and was reversible. 相似文献
2.
Effects of Anions on the Capacity and Affinity of Copper Adsorption in Two Variable Charge Soils 总被引:2,自引:0,他引:2
Effects of nitrate,(NO3−) chloride (Cl−), sulfate (SO42-, and acetate (Ac−) on Cu2+ adsorption and affinity of the adsorbed Cu2+ were evaluated in two Fe and Al enriched variable charge soils from Southern China. The maximum adsorption of Cu2+ (M, a parameter from the Langmuir isotherm model) in the presence of different anions decreased in the order
Cl− > Ac− > NO3− > SO42- for both soils. The clayey loamy soil (mixed siliceous thermic Typic Dystrochrept, TTD), developed on the Arenaceous rock,
adsorbed less Cu2+ than the clayey soil (kaolinitic thermic Plinthudults, KTP), derived from the Quaternary red earths, regardless of anion
type present in the medium. The affinity of adsorbed Cu2+ to both soils could be characterized by the Kd (distribution coefficient) values and successive extraction of the adsorbed Cu2+ with 1-mol NH4Ac L−1. The log10Kd value was smaller for the TTD soil than for the KTP soil and decreased in the order of Cl− > NO3− > SO42- > Ac−
at low initial Cu2+ concentrations (≤40 mg Cu2+L−1), whereas at 80 mg Cu2+L−1, the log10Kd value was similar for NO3−, SO42-, and Ac−, but was slightly higher for Cl−. Complete extraction of Cu2+ adsorbed in the presence of Ac− was achieved. Influence of NO3− and SO42- on the affinity of adsorbed Cu2+ was similar, but the effects of Cl− depended on the initial Cu2+ concentrations. The extracted percentage of the adsorbed Cu2+ in the presence of NO3− or SO42- increased with increasing Cu2+ adsorption saturation. The presence of Cl−, NO3−, or SO42- markedly decreased the equilibrium solution pH for both soils with increasing initial Cu2+ concentrations, and the delta pH values at the highest Cu2+ level were 0.5, 0.63, and 0.55 U for the TTD soil and 0.79, 0.84, and 0.93 U for the KTP soil, respectively for the three
anions. The presence of Ac− had a minimal influence on the equilibrium solution pH because of the buffering nature of the NaAc/HAc medium which buffered
the released protons. The effects of anions on Cu2+ adsorption and affinity of the adsorbed Cu2+ were dependent on anion types and were apparently related to the altered surface properties caused by anion adsorption and/or
the formation of anion– Cu2+ complexes. 相似文献
3.
We investigated the properties of calcium-activated chloride channels in inside-out membrane patches from the dendritic knobs
of acutely dissociated rat olfactory receptor neurons. Patches typically contained large calcium-activated currents, with
total conductances in the range 30–75 nS. The dose response curve for calcium exhibited an EC50 of about 26 μm. In symmetrical NaCl solutions, the current-voltage relationship reversed at 0 mV and was linear between −80 and +70 mV.
When the intracellular NaCl concentration was progressively reduced from 150 to 25 mM, the reversal potential changed in a manner consistent with a chloride-selective conductance. Indeed, modeling these data
with the Goldman-Hodgkin-Katz equation revealed a PNa/PCl of 0.034. The halide permeability sequence was PCl > PF > PI > PBr indicating that permeation through the channel was dominated by ion binding sites with a high field strength. The channels
were also permeable to the large organic anions, SCN−, acetate−, and gluconate−, with the permeability sequence PCl > PSCN > Pacetate > Pgluconate. Significant permeation to gluconate ions suggested that the channel pore had a minimum diameter of at least 5.8 \A.
Received: 16 April 1997/Revised: 3 October 1997 相似文献
4.
Previous measurements with CsF pipette solutions using whole-cell patch-clamp techniques in dissociated rat olfactory receptor
neurons (ORNs) indicated that the sodium currents had very negative inactivation characteristics with the implication that
the cell resting potential must also normally have a very negative value. This study supports the conclusions that such an
effect was real and not dependent on either the nature of the pipette anions or the recording situation previously used. For
all pipette solutions, sodium currents showed a threshold activation ≈−80 mV and half-maximal activation voltages ≈−55 with
half-inactivation potential ≤−100 mV, without being significantly affected by the replacement of F− by other pipette anions (H2PO−
4 and acetate−) or the addition of nucleotides and glutathione (which did cause a very slight positive shift). F−, followed by H2PO−
4 and to a much lesser extent by acetate−, was the most favorable pipette anion for obtaining good seals and whole-cell sodium currents in these extremely small ORNs.
These results implied that resting potentials, for viable responsive cells, should be more negative than about −90 mV, as
supported by the observation that action potentials could only be evoked from holding potentials more negative than −90 mV.
Received: 23 December 1999/Revised: 2 March 2000 相似文献
5.
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
6.
Single anion channels reconstituted from cardiac mitoplasts 总被引:4,自引:0,他引:4
Ion channels from sheep cardiac mitoplast (inverted inner mitochondrial membrane vesicle) preparations were incorporated into
voltage-clamped planar lipid bilayers. The appearance of anion rather than cation channels could be promoted by exposing the
bilayers to osmotic gradients formed by Cl− salts of large, relatively imperment, cations at a pH of 8.8. Two distinct activities were identified. These comprised a
multisubstate anion channel of intermediate conductance (∼60 pS in 300vs. 50mm choline Cl, ∼100 pS in symmetric 150mm KCl), and a lower-conductance anion channel (∼25 or ∼50 pS in similar conditions), which only displayed two well-defined
substates, at ∼25 and ∼50% of the fully open state. The larger channels were not simple multiples of the lower-conductance
channels, but both discriminated poorly, and to a similar extent, between anions and cations (PCl
−/Pcholine
+ ∼12, PCl
−/PK
+∼8). The lower-conductance channel was only minimally selective between different anions (PNO
3
−
(1.0)=PCl
−>PBr
−>PI
−>PSCN
−(0.8)), and its conductance failed to saturate even in high (>1.0 M) activities of KCl. The channels were not obviously voltage
dependent, and they were unaffected by 0.5 mM SITS, H2O2, propranolol, quinine or amitriptyline, or by 2 mM ATP, or by variations in pH (5.5–8.8). Ca2+ and Mg2+ did not alter single channel activity, but did modify single current amplitudes in the lower-conductance channel. This effect,
together with voltage-dependent substate behavior, is described in the following paper. 相似文献
7.
GABA-activated Cl− current was expressed in Xenopus oocytes after injecting cRNA that had been transcribed in vitro from complementary DNA (cDNA) coding for a single GABA ρi-subunit cloned from human retina. The expressed current was insensitive to 100 μm bicuculline, but was activated by the GABA analogue trans-4-aminocrontonic acid (TACA). Anion-selective permeability of the
expressed ρ1-subunit was determined by isotonically replacing the extracellular Cl− with different anions. The anion permeability was very similar to the native GABAA receptor/channel following a sequence of SCN− > I− > NO3
− > Br−≥ Cl−. Halogenated fatty acids, such as chlorotrifluoroethylene (CTFE) and perfluorinated oligomer acids inhibited the GABA-induced
current in oocytes expressing the human retinal GABA ρ1-subunit or rat brain GABAA receptor α1,β2,γ2 subunits. The inhibitory effect of halogenated fatty acids demonstrated a carbon chain length-dependent manner of: C10 > C8 > C6 > C4. Perfluorinated C8-oligomer acid (PFOA) was less effective at blocking this channel than the C8-CTFE oligomer acid. Radiolabeled GABA binding assay indicated that CTFE oligomer acids do not interfere at the GABA binding
site of the receptor. Furthermore, the C8-CTFE oligomer fatty acid did not compete with picrotoxin for binding sites within the pore of the channel. These studies
demonstrated that the heterologous expression system is useful for studying the molecular interaction between potential neurotoxic
agents and neuroreceptors. Our results provide detailed information that should contribute to our understanding of the structure
and function of retinal GABA receptors.
Received: 12 June 1995/Revised: 21 September 1995 相似文献
8.
The objective of this study is to describe the biogeochemical characteristics in the waters of Mongolian lakes, particularly
those related to parameters limiting phytoplankton growth and the trophic state. Investigations into the distribution of chemical
and biological parameters were carried out in the following 18 lakes: Har Us, Har, Hovsgol, Achit, Dalai, Bayan, Tolbo, Holboo,
Bust, Sangiyn Dalai, Tunamal, Dorgon, Uureg, Telmen, Hyargas, Uvs, Erkhel and Oygon, all of which showed a wide range of salinity
between 0.16 and 24.9 g l−1. Lake water was classified into four types: six fresh (less than 0.5 g l−1 salinity), three subsaline (0.5–3 g l−1), seven hyposaline (3–20 g l−1) and two mesosaline (20–50 g l−1) lakes. Predominant cations and anions in the order of dominance were Ca, Mg > Na > K and HCO3 > SO4, Cl in freshwater lakes, Na > Mg > Ca, K and HCO3, Cl > SO4 in subsaline lakes, and Na > Mg > K, Ca and Cl, SO4 > HCO3 in hyposaline and mesosaline lakes. Nitrogenous and phosphorus nutrients in the waters were low, seemingly caused by the
low loads from their watersheds, where the ground was free of vegetation with an extremely low level of human activity. The
present investigations revealed some 234 taxa of phytoplankton and 38 of zooplankton. The PC:PN:PP stoichiometric ratio by
weight was (22–202):(3–27):1. Phosphorus was assessed as the potential limiting parameter in eight lakes, nitrogen in six
and both nutrients in four others. Twelve lakes showed an oligotrophic character, while six were mesotrophic type. The six
oligotrophic lakes seemed to be subject to phosphorus limiting phytoplankton growth, four to nitrogen and two to both limitations.
In the mesotrophic lakes, on the other hand, phosphorus limitation was verified in two lakes, nitrogen in two others and both
in two lakes. 相似文献
9.
Relationship between river water quality and land use in a small river basin running through the urbanizing area of Central Japan 总被引:9,自引:0,他引:9
In this study, the relationship between water quality (as represented by major inorganic ion concentrations) and land use
characteristics is examined for a small river basin which runs through the urbanizing area of central Japan. Water samples
were taken from 24 sites at base flow and analyzed, and the proportions of the various land uses associated with the respective
drainage basins were calculated using a digital land-use map (scale: 1:25000). The electrical conductivity (EC) of the water
ranged from 84.5 to 600 μS cm−1. Ca2+ and Na+ were the major cations, accounting for 77% of all cations. Among the anions, HCO3
− was dominant (56%), followed by Cl− (24%), SO4
2− (13%) and NO3
− (7%). Applying principal component analysis to land use in the drainage basin yielded three principal components. The first
principal component expressed the degree of occupation by residential areas, the second indicated the degree of urban developing
area (i.e., fast-developing and industrial areas), and the third showed the degree of coverage with farmland and green space.
The residential area showed significant positive correlations with K+, Mg2+, Ca2+, NO3
−, HCO3
−, EC and TMI (total major ions). Urban developing area showed significant positive correlations with Ca2+, Cl−, HCO3
−, EC and TMI as well as weak negative correlations with NO3
− and SO4
2−. Industrial area showed weak positive correlations with Na+ and Cl− and a moderate negative correlation with NO3
−. Farmland showed significant positive correlations with NO3
− and SO4
2−; these ions are present due to fertilizers and the biological activity of plants. Forest area is inversely related to almost
all ions, indicating the need for this form of land use in order to maintain river water quality. 相似文献
10.
Zimmermann D Kiesel M Terpitz U Zhou A Reuss R Kraus J Schenk WA Bamberg E Sukhorukov VL 《The Journal of membrane biology》2008,221(2):107-121
Interactions of structurally dissimilar anionic compounds with the plasma membrane of HEK293 cells were analyzed by patch
clamp and electrorotation. The combined approach provides complementary information on the lipophilicity, preferential affinity
of the anions to the inner/outer membrane leaflet, adsorption depth and transmembrane mobility. The anionic species studied
here included the well-known lipophilic anions dipicrylamine (DPA−), tetraphenylborate (TPB−) and [W2(CO)10(S2CH)]−, the putative lipophilic anion
and three new heterocyclic W(CO)5 derivatives. All tested anions partitioned strongly into the cell membrane, as indicated by the capacitance increase in patch-clamped
cells. The capacitance increment exhibited a bell-shaped dependence on membrane voltage. The midpoint potentials of the maximum
capacitance increment were negative, indicating the exclusion of lipophilic anions from the outer membrane leaflet. The adsorption
depth of the large organic anions DPA−, TPB− and increased and that of W(CO)5 derivatives decreased with increasing concentration of mobile charges. In agreement with the patch-clamp data, electrorotation
of cells treated with DPA− and W(CO)5 derivatives revealed a large dispersion of membrane capacitance in the kilohertz to megahertz range due to the translocation
of mobile charges. In contrast, in the presence of TPB− and no mobile charges could be detected by electrorotation, despite their strong membrane adsorption. Our data suggest that the
presence of oxygen atoms in the outer molecular shell is an important factor for the fast translocation ability of lipophilic
anions. 相似文献
11.
Torres ML Ortega F Cuaranta I González J Sanchez-Armass S 《Neurochemical research》2008,33(8):1574-1581
The Na+/H+ exchanger has been the only unequivocally demonstrated H+-transport mechanism in the synaptosomal preparation. We had previously suggested that a Cl−–H+ symporter (in its acidifying mode) is involved in cytosolic pH regulation in the synaptosomal preparation. Supporting this
suggestion, we now show that: (1) when synaptosomes are transferred from PSS to either gluconate or sulfate solutions, the
Fura-2 ratio remains stable instead of increasing as it does in 50 mM K solution. This indicates that these anions do not
promote a plasma membrane depolarization. (2) Based in the recovery rate from the cytosolic alkalinization, the anionic selectivity
of the Cl−–H+ symporter is NO3− > Br− > Cl− >> I− = isethionate = sulfate = methanesulfonate = gluconate. (3) PCMB 10 μM inhibits the gluconate-dependent alkalinization by
30 ± 6%. (4) Neither Niflumic acid, 9AC, Bumetanide nor CCCP inhibits the recovery from the cytosolic alkalinization.
Special issue article in honor of Dr. Ricardo Tapia. 相似文献
12.
The impacts of various nitrogen sources, i.e. NO−
3, NH4
+ or NH4NO3 in combination with gaseous NH3, on nitrogen-, carbon- and water-use efficiency and 13C discrimination (δ13C) by plants of the C3 species Triticum aestivum L. (wheat) and the C4 species Zea mays L. (maize) were studied. Triticum aestivum and Z. mays were hydroponically grown with 2 mol · m−3 of N supplied as NO−
3, NH4
+ or NH4NO3 for 21 and 18 d, respectively, and thereafter exposed to gaseous NH3 at 320 μg · m−3 or to ambient air for 7 d. In T. aestivum and Z. mays over a 7-d growth period, nitrogen-use efficiency (NUE) values were influenced by N-sources in the decreasing order NH4NO3-N > NO−
3-N > NH4
+-N and NO−
3-N > NH4NO3-N > NH4
+-N, respectively. Fumigation with NH3 decreased the NUE values of plants grown with any of the N-forms. During 28- and 7-d growth periods, N-sources affected water-use
efficiency (WUE) values in the decreasing order of NH4
+-N > NO−
3-N≈NH4NO3-N in non-fumigated T. aestivum, while fumigation with NH3 increased the WUE of NO−
3-grown plants. There were insignificant effects of N-sources on WUE values of Z. mays over 25- and 7-d growth periods. Furthermore, δ13C values in plant tissues (leaves, stubble and roots) were higher (less negative) in NH4
+-grown plants of T. aestivum and Z. mays than in those supplied with NH4NO3 or NO−
3. Regardless of the N-form supplied to the roots of the plant species, exposure to NH3 caused more-positive δ13C values in the plant tissues. These results indicate that the variations in N-source were associated with small but significant
variations in δ13C values in plants of T. aestivum and Z. mays. These differences in δ13C values are in the direction expected from differences in WUE values over long or short growth periods and with differences
in the extent of non-Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase, EC 4.1.1.39) carboxylate contribution to net
C acquisition, as a function of N-source.
Received: 12 September 1997 / Accepted: 13 January 1998 相似文献
13.
Fereydoon Malekzadeh Saeid Ghorbanzadeh Mashkani Hossein Ghafourian Mohammad Reza Soudi 《World journal of microbiology & biotechnology》2007,23(7):905-910
An attempt was made to isolate bacterial strains capable of biologically removing tungstate (WO42−). Thirty-eight water samples were collected from various areas of Anzali lagoon, Iran. Initial screening of a total of 100
bacterial isolates at pH 5, resulted in the selection of one isolate with maximum adsorption capacity of 65.4 mg tungstate/g
dry weight. It was tentatively identified as Bacillus sp. according to morphological and biochemical properties and named strain MGG-83. Tungsten concentration was measured spectrophotometrically
using the dithiol method. Higher adsorption capacity was observed in the acidic pH ranging from 1 to 3. At pH 2, the strain
removed 274.4 mg tungstate/g dry weight within 5 min from the solution with 300 mg WO42−/l initial concentration and thereafter adsorption rate decreased remarkably. The applicability of the Freundlich isotherm
for representation of the experimental data was investigated. Using 1 mM sodium azide and 10 mM 2,4−dinitrophenol, it was
shown that only 20% reduction occurred in adsorption and steam sterilization of the bacterial cells resulted in 11% decrease
in tungstate uptake. Temperature variations (20–40°C) had no significant effect on tungstate uptake. Pretreatment with the
cations had no effect in uptake but pretreatment with anions decreased the tungstate uptake as indicated: sulfate > chromate > nitrate > molybdate > selenate > rhenate.
Tungstate was removed from metal-laden biomass after desorption treatments by addition of different desorbing solutions with
the results sodium acetate > EDTA > NaCl > KOH > H2SO4. 相似文献
14.
The thermodynamical stability and remained activity of mushroom tyrosinase (MT) fromAgaricus bisporus in 10 mM phosphate buffer, pH 6.8, stored at two temperatures of 4 and 40°C were investigated in the presence of three different
amino acids (His, Phe and Asp) and also trehalose as osmolytes, for comparing with the results obtained in the absence of
any additive. Kinetics of inactivation obeye the first order law. Inactivation rate constant (kinact) value is the best parameter describing effect of osmolytes on kinetic stability of the enzyme. Trehalose and His have the
smallest value of kinact(0.7×10−4s−1) in comparison with their absence (2.5×10−4s−1). Moreover, to obtain effect of these four osmolytes on thermodynamical stability of the enzyme, protein denaturation by
dodecyl trimethylammonium bromide (DTAB) and thermal scanning was investigated. Sigmoidal denaturation curves were analysed
according to the two states model of Pace theory to find the Gibbs free energy change of denaturation process in aqueous solution
at room temperature, as a very good thermodynamic criterion indicating stability of the protein. Although His, Phe and Asp
induced constriction of MT tertiary structure, its secondary structure had not any change and the result was a chemical and
thermal stabilization of MT. The enzyme shows a proper coincidence of thermodyanamic and structural changes with the presence
of trehalose. Thus, among the four osmolytes, trehalose is an exceptional protein stabilizer. 相似文献
15.
Depletion of adenosine triphosphate inDesulfovibrio by oxyanions of group VI elements 总被引:1,自引:0,他引:1
Oxyanions of elements from group VI of the periodic table, i.e., analogs of SO4
2−, destroyed adenosine 5′-triphosphate (ATP) in cells of sulfate-respiring bacteria (Desulfovibrio spp.), probably via the ATP sulfurylase reaction. The approximate order of effectiveness was CrO4
2−> MoO4
2−=WO4
2−>SeO4
2−. Cultures of aerobically grown or nitrate-respiring bacteria were less susceptible and with fermentatively grownEscherichia coli the oxyanions even appeared to stimulate ATP levels. The selective depletion of ATP in sulfate-respiring bacteria might provide
the basis for a rapid and simple assay of their biomass in mixed cultures or environmental samples. 相似文献
16.
Simultaneous nutrients and carbon removal during pretreated swine slurry degradation in a tubular biofilm photobioreactor 总被引:1,自引:0,他引:1
Ignacio de Godos Cristina González Eloy Becares Pedro A. García-Encina Raúl Muñoz 《Applied microbiology and biotechnology》2009,82(1):187-194
The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated
(centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen,
and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from
94% to 100% and 70–90%, respectively. Maximum total organic carbon (TOC), NH4
+, and PO4
3− removal rates of 80 ± 5 g C mr
−3 day−1, 89 ± 5 g N mr
−3 day−1, and 13 ± 3 g P mr
−3 day−1, respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 ± 62 mg L−1, N–NH4
+ of 656 ± 37 mg L−1, P–PO4
3+ of 117 ± 19 mg L−1, and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic
biofilm (photosynthetic O2 and TOC/NH4
+ diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification
process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated
by the combination of high pH and high NH3 concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass
generated during the pretreated swine slurry biodegradation). 相似文献
17.
Yang Lifeng Yu Lin Liu Yan Chen Yong Hu Liming Zhao Yufen 《International journal of peptide research and therapeutics》2003,10(2):89-92
Summary Positive ion mode of electrospray ionization mass spectrometry (ESI-MS) has been used for the detection and study of protein
interaction. From the measurement of molecular mass of the intact complex and individual binding partners, the binding stoichiometry
can be derived. In our work, one basic protein, hen egg white lysozyme (HEWL) as an anion receptor shows high sensitivity
and selectivity responses to most oxoanions detected by ESI-MS. But neutral protein, such as insulin, does not response to
anions. It was found that HSO
4
−
, IO
4
−
, ClO
4
−
, H2PO
4
−
, HCO
3
−
and AcO− have strong affinity to interact with HEWL under present condition, but HSO
3
−
, NO
3
−
, Cl− and F− could not be trapped by HEWL. ESI-MS condition and concentration of anions are considered. This is an important evidence
obtained by mass spectrometry for the distribution of anion recognition with a native protein. 相似文献
18.
Human β-mannosidase (MANB) was purified to homogeneity directly from lysosomes by using mannosamine conjugated magnetic (Fe3O4) nanoparticles, DE-52 cellulose, and sephadex G-200 chromatography. Fe3O4 nanoparticles were synthesized and utilized ammonia to attach the amino group on the nanoparticles. The particles were covalently
attached with D-mannosamine by cross linker glutaraldehyde and confirmed by FTIR spectroscopy. In FTIR analysis, the peaks
appeared at 2,356.6 cm−1 for −N = CH linkage and at 3,378.4 cm−1, 3,664.9 cm−1 for −OH groups confirmed the conjugation of D-mannosamine with Fe3O4 nanoparticles. Results showed a single band of 97 kDa of purified MANB in SDS-PAGE. The isoelectric point was 4.5 and the
Km and Vmax values were 2.51 mM and 0.315 μM/min/mg, respectively. The purification fold was 329 with 68% yield. The optimal activity
was at pH 5.0 and 75% activity was stable in 20% glycerol at 4°C. The enzyme activity was inhibited by Ni2+, Zn2+, Cd2+, Cu2+, Mo2+, Ag+1, iodoacetate, SDS, DMF, DMSO, ethanol, and acetone; slightly reduced by Pb2+, Co2+, EDTA, DTT, and β-mercaptoethanol. The activity was not affected by Mg2+, Mn2+, Sn2+, Ca2+, Fe3+, PMSF, Triton X-100, D-mannosamine, D-mannose, D-mannitol, D-glucose, and D-fructose. The homogeneity of MANB enzyme was
further confirmed by 2D-PAGE and immunoblot. This is the first novel report of conjugation of D-mannosamine with Fe3O4 nanoparticles for purification of human MANB enzyme. 相似文献
19.
Using the whole-cell patch-clamp technique, we examined Cl−-selective currents manifested by strial marginal cells isolated from the inner ear of gerbils. A large Cl−-selective conductance of ∼18 nS/pF was found from nonswollen cells in isotonic buffer containing 150 mm Cl−. Under a quasi-symmetrical Cl− condition, the `instantaneous' current-voltage relation was close to linear, while the current-voltage relation obtained
at the end of command pulses of duration 400 msec showed weak outward rectification. The permeability sequence for anionic
currents was as SCN− > Br−≅ Cl− > F− > NO−
3≅ I− > gluconate−, corresponding to Eisenmann's sequence V. When whole-cell voltage clamped in isotonic bathing solutions, the cells exhibited
volume changes that were accounted for by the Cl− currents driven by the imposed electrochemical potential gradients. The volume change was elicited by lowered extracellular
Cl− concentration, anion substitution and altered holding potentials. The Cl− conductance varied in parallel with cell volume when challenged by bath anisotonicity. The whole-cell Cl− current was only partially blocked by both 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB, 0.5 mm) and diphenylamine-2-carboxylic acid (DPC, 1.0 mm), but 4-acetamido-4′-isothiocyanato-stilbene-2,2′-disulfonic acid (SITS, 0.5 mm) was without effect. The properties of the present whole-cell Cl− current resembled those of the single Cl− channel previously found in the basolateral membrane of the marginal cell (Takeuchi et al., Hearing Res.
83:89–100, 1995), suggesting that the volume-correlated Cl− conductance could be ascribed predominantly to the basolateral membrane. This Cl− conductance may function not only in cell volume regulation but also for the transport of Cl− and the setting of membrane potential in marginal cells under physiological conditions.
Received: 15 August 1995/Revised: 3 November 1995 相似文献
20.
Spatial variability of soil total nitrogen (N), available N (KCl extractable NH4+ and NO3−), and spatial patterns of N mineralization and nitrification at a stand scale were characterized with geostatistical and
univariate analysis. Two extensive soil spatial samplings were conducted in an evergreen broadleaf forest in Sichuan province,
southwestern China in June and August 2000. In a study area of 90 × 105 m2, three soil samples were collected from each 5 × 5 m2 plot (n = 378) in June and August, and were analyzed for total N and available N contents. Net N mineralization and nitrification
were measured by in situ core incubation and the rates were estimated based on the difference of NH4+ and NO3− contents between the two sampling dates. Total N, NH4+, and NO3− were all spatially structured with different semivariogram ranges (from high to low: NH4+, NO3−, and total N). The semivariograms of mineralization and nitrification were not as spatially structured as available N. NH4+ was the dominant soil inorganic N form in the system. Both NH4+ and NO3− affected spatial patterns of soil available N, but their relative importance switched in August, probably due to high nitrification
as indicated by greatly increased soil NO3− content. High spatial auto-correlations (>0.7) were found between available N and NH4+, available N and NO3− on both sampling dates, as well as total N measurements between both sampling dates. Although significant, the spatial auto-correlation
between NH4+ and NO3− were generally low. Topography had significant but low correlations with mineralization (r = −0.16) and nitrification (r = −0.14), while soil moisture did not. The large nugget values of the calculated semivariograms and high-semivariance values,
particularly for mineralization and nitrification, indicate that some fine scale (<5 m) variability may lie below the threshold
for detection in this study. 相似文献