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1.
This study describes the toxic effects of different prominent aquatic pollutants—heavy metals (Cd & Pb), pesticides (alphamethrin
and deltamethrin) and salt (NaCl)—on the intracellular proline content in the cyanobacterium, Westiellopsis prolifica–Janet strain–NCCU331. Despite a reduction in growth (measured as chlorophyll a content), the intracellular proline content increased in the presence of heavy metals, pesticides and high salt concentration.
The intracellular cyanobacterial proline accumulation was more pronounced under salt stress than in the presence of pesticides
and heavy metals. We have also compared whether or not anionic components influence heavy metal toxicity. It was found that
the chlorides of Cd and Pb were more toxic than the NO3 and the order of toxicity was CdCl2 > PbCl2 > Cd (NO3)2 > Pb (NO3)2. Among pyrethroids, deltamethrin was more toxic than alphamethrin.
Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines. 相似文献
2.
3.
Stephen E. Cabaniss Greg Madey Laura Leff Patricia A. Maurice Robert Wetzel 《Biogeochemistry》2007,86(3):269-286
A stochastic biogeochemical model has been developed to simulate the transformation and degradation of natural organic matter
(NOM) using an agent-based algorithm which treats each molecule as a separate and potentially unique entity. Molecules react
when a pseudo-random number is lower than the calculated reaction probability in a given time step; repeated time steps simulate
the transformation of precursor molecules into a complex NOM assemblage. The data for each molecule—elemental and functional
group composition—can be used to calculate many properties directly and exactly for each molecule in the assemblage, e.g.,
molecular weight (MW), fraction of aromatic C (Ar), and charge at pH 7 (Z). Empirical quantitative structure activity relationships
(QSARs) are developed which permit the estimation of thermodynamic quantities K
ow (the octanol–water partition coefficient) and pK
a (acidity) for each molecule. Root mean square errors for these QSARs are 0.39 log units for log K
ow and 0.45 log units for pK
a. Distributions of both exactly calculated (MW, Ar, Z) and estimated thermodynamic (K
ow, pK
a) properties are examined and compared with published experimental data. Molecular weight distributions from size exclusion
HPLC experiments on aquatic NOM are quantitatively similar to simulation results. pH titrations and polarity distributions
from reversed-phase HPLC are qualitatively similar to simulation results. This agreement suggests that the agent-based model
can be used to explore hypotheses regarding both compositional and thermodynamic properties of NOM.
Robert Wetzel—deceased. 相似文献
4.
G. Park F. H. Lu N. Ye M. W. Brechbiel S. V. Torti F. M. Torti R. P. Planalp 《Journal of biological inorganic chemistry》1998,3(5):449-457
The interaction of Fe(II) and Fe(III) with the novel Fe(II) chelator N,N′N″-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane (referred to as tachpyr) gives rise to six-coordinate, low-spin, cationic complexes of Fe(II).
Tachpyr also displays a cytotoxicity toward cultured bladder cancer cells that is believed to involve coordination of intracellular
iron. The anaerobic reaction of tachpyr with Fe(II) salts affords the Fe(II)-tachpyr2+ complex, but in presence of oxygen, oxidative dehydrogenation of one or two of the aminomethylene group(s) of the ligand
occurs, with formal loss of H2: R—N(H)—C(H)2—(2-py) → R—N=C(H)—(2-py)+H2. The resulting mono- and diimino Fe(II) complexes (denoted as [Fe(tachpyr-H2)]2+ and [Fe(tachpyr-2H2)]2+) are an inseparable mixture, but they may be fully oxidized by H2O2 to the known tris(imino) complex Fe(II)[cis,cis-1,3,5-tris(pyridine-2-carboxaldimino)cyclohexane]2+ (or [Fe(tachpyr-3H2)]2+). Cyclic voltammetry of the imino complex mixture reveals an irreversible anodic wave at +0.78 V vs. NHE. Tachpyr acts as
a reducing agent toward Fe(IIII) salts, affording the same two Fe(II) imino complexes as products. Tachpyr also reductively
removes Fe(III) from an Fe(III)(ATP)3 complex (which is a putative form of intracellular iron), producing the two Fe(II) imino complexes. Novel N-alkylated derivatives of tachpyr have been synthesized. N-Alkylation has two effects on tachpyr: lowering metal affinity through increased steric hindrance, and preventing Fe(III)
reduction because oxidative dehydrogenation of nitrogen is blocked. The N-methyl tachpyr derivative binds Fe(II) only weakly as a high-spin complex, and no complexation or reduction of Fe(III) is
observed. Corresponding to their inability to bind iron, the N-alkylated chelators are nontoxic to cultured bladder cancer cells. A tach-based chelator with three N-propyleneamino arms is also synthesized. Studies of the chemical and biochemical properties of this chelator further support
a relationship between intracellular iron chelation, iron reduction, and cytotoxicity.
Received: 23 March 1998 / Accepted: 1 June 1998 相似文献
5.
Relevance of Rheological Properties of Sodium Alginate in Solution to Calcium Alginate Gel Properties 总被引:2,自引:0,他引:2
Fu S Thacker A Sperger DM Boni RL Buckner IS Velankar S Munson EJ Block LH 《AAPS PharmSciTech》2011,12(2):453-460
The purpose of this study is to determine whether sodium alginate solutions’ rheological parameters are meaningful relative
to sodium alginate’s use in the formulation of calcium alginate gels. Calcium alginate gels were prepared from six different
grades of sodium alginate (FMC Biopolymer), one of which was available in ten batches. Cylindrical gel samples were prepared
from each of the gels and subjected to compression to fracture on an Instron Universal Testing Machine, equipped with a 1-kN
load cell, at a cross-head speed of 120 mm/min. Among the grades with similar % G, (grades 1, 3, and 4), there is a significant correlation between deformation work (L
E) and apparent viscosity (η
app). However, the results for the partial correlation analysis for all six grades of sodium alginate show that L
E is significantly correlated with % G, but not with the rheological properties of the sodium alginate solutions. Studies of the ten batches of one grade of sodium
alginate show that η
app of their solutions did not correlate with L
E while tan δ was significantly, but minimally, correlated to L
E. These results suggest that other factors—polydispersity and the randomness of guluronic acid sequencing—are likely to influence
the mechanical properties of the resultant gels. In summary, the rheological properties of solutions for different grades
of sodium alginate are not indicative of the resultant gel properties. Inter-batch differences in the rheological behavior
for one specific grade of sodium alginate were insufficient to predict the corresponding calcium alginate gel’s mechanical
properties. 相似文献
6.
P. I. P. Perera D. M. D. Yakandawala V. Hocher J-L. Verdeil L. K. Weerakoon 《Plant Cell, Tissue and Organ Culture》2009,96(2):171-180
The effect of growth regulators on induction of androgenesis in coconut was investigated using seven different growth regulators
at various concentrations and combinations. Three auxins (1-naphthalene acetic acid—NAA, indoleacetic acid—IAA, picloram)
and three cytokinins (2-isopentyl adenine-2-iP, kinetin, zeatin) were tested either alone or in combination with 2,4-dichlorophenoxyacetic
acid (2,4-D), using modified Eeuwens Y3 liquid medium as the basal medium. Among the tested auxins, 100 μM NAA in combination
with 100 μM 2,4-D enhanced the production of calli/embryos (123) whereas IAA and picloram showed negative and detrimental
effects, respectively, for androgenesis induction over 100 μM 2,4-D alone. Kinetin and 2-iP enhanced the production of calli/embryos
when 100 μM 2,4-D was present in the culture medium. Both cytokinins at 10 μM yielded the highest frequencies of embryos (113
and 93, respectively) whereas zeatin (1 or 2.5 μM) had no impact on microspore embryogenesis. When calli/embryos (produced
from different treatments in different experiments) were sub-cultured in somatic embryo induction medium (Y3 medium containing 66 μM 2,4-D), followed by maturation medium (Y3 medium without growth regulators) and germination medium (Y3 medium containing 5 μM-6-benzyladenine—BA and 0.35 μM gibberellic acid—GA3), plantlets were regenerated at low frequencies (in most treatments ranging from 0% to 7%). 相似文献
7.
8.
CuA is a binuclear copper center that functions as an electron transfer agent, cycling between a reduced Cu(I)Cu(I) state and
an oxidized mixed-valence Cu(+1.5)···Cu(+1.5) state. The copper ions are bridged by two cysteine thiolate ligands and form
a copper–copper bond, the first reported of its kind in Nature. Such a “diamond-core” Cu2S(Cys)2 structure allows an unpaired electron to be completely delocalized over the two copper ions and contributes to its highly
efficient electron transfer properties. This review provides accounts of how the CuA center was structurally characterized and highlights its salient spectroscopic properties. In the process, it introduces
the CuA center in four different systems—native protein systems, soluble protein truncates of native proteins, synthetic models using
organic molecules, and biosynthetic models using proteins as ligands—with a greater emphasis on biosynthetic models of CuA, especially on new, deeper insights gained from their studies. 相似文献
9.
Two-step concerted mechanism for alkane hydroxylation on the ferryl active site of methane monooxygenase 总被引:1,自引:0,他引:1
Kazunari Yoshizawa 《Journal of biological inorganic chemistry》1998,3(3):318-324
A two-step concerted mechanism for the conversion of methane to methanol catalyzed by soluble methane monooxygenase (sMMO)
is discussed. We propose that the enzymatic reaction mechanism is essentially the same as that of the gas-phase methane-methanol
conversion by the bare FeO+ complex. In the initial stage of our mechanism, the ferryl (Fe—O) "iron" active site of intermediate Q and substrate methane come into contact to form the initial Q (CH4) complex with an OFe—CH4 bond. The C—H bonds of methane are significantly weakened by the formation of a five-coordinate carbon species, through orbital
interactions between a C
3v
- or D
2d
-distorted methane and the Fe—O active site. The important transition state for an H atom abstraction exhibits a four-centered
structure. The generated intermediate involves an HO—Fe—CH3 moiety, and it is then converted into the final product complex including methanol as a ligand through a methyl migration
that occurs via a three-centered transition state. The two-step concerted mechanism is consistent with recent experiments
on regioselectivity of enzyme-catalyzed alkane hydroxylations.
Received: 15 September 1997 / Accepted: 20 December 1997 相似文献
10.
The main idea of S-curve diagram is to assign different angle values (from 0° to 180°) to different nucleotide acid residues
or to different protein amino acids, and then according to cos α
j
and sin α
j
, the values are accumulated to construct an S-curve diagram, which is in strict one-to-one correspondence with the biological
sequence. In addition, the S-curve diagram proves to be without the degeneracy phenomenon, so that both the degeneracy problem
represented by diagrams and the problem of visualization for biological sequence data are solved. Meanwhile, a new approach
to differentiate the similarity of biological sequences—the degree of similarity—is put forward on the basis of the S-curve
diagram. To put it in detail, the least square approach is first adopted to obtain a straight line equation according to the
S-curve diagram, then according to the distance formula of the point to the straight line, the average ratio of square sum
for the distance between the S-curve and the straight line is calculated, and finally, the similarity of the biological sequences
is presented by the new standard—the degree of similarity. As is shown by the experimental results, the S-curve diagram can
better represent biological sequences (such as protein’s) within Cartesian coordinate system, and the mutation point of biological
sequence. Thus, it turns out that the new standard—the degree of similarity is of obviously great advantage. 相似文献
11.
Ettema TJ Ahmed H Geerling AC van der Oost J Siebers B 《Extremophiles : life under extreme conditions》2008,12(1):75-88
Archaea utilize a branched modification of the classical Entner–Doudoroff (ED) pathway for sugar degradation. The semi-phosphorylative
branch merges at the level of glyceraldehyde 3-phosphate (GAP) with the lower common shunt of the Emden-Meyerhof-Parnas pathway.
In Sulfolobus solfataricus two different GAP converting enzymes—classical phosphorylating GAP dehydrogenase (GAPDH) and the non-phosphorylating GAPDH
(GAPN)—were identified. In Sulfolobales the GAPN encoding gene is found adjacent to the ED gene cluster suggesting a function
in the regulation of the semi-phosphorylative ED branch. The biochemical characterization of the recombinant GAPN of S. solfataricus revealed that—like the well-characterized GAPN from Thermoproteus tenax—the enzyme of S. solfataricus exhibits allosteric properties. However, both enzymes show some unexpected differences in co-substrate specificity as well
as regulatory fine-tuning, which seem to reflect an adaptation to the different lifestyles of both organisms. Phylogenetic
analyses and database searches in Archaea indicated a preferred distribution of GAPN (and/or GAP oxidoreductase) in hyperthermophilic
Archaea supporting the previously suggested role of GAPN in metabolic thermoadaptation. This work suggests an important role
of GAPN in the regulation of carbon degradation via modifications of the EMP and the branched ED pathway in hyperthermophilic
Archaea.
Thijs J. G. Ettema and Hatim Ahmed have contributed equally to this work. 相似文献
12.
Mauro Angeletti Giulio Lupidi Anna Maria Eleuteri Rosalia Tacconi Evandro Fioretti M. Coletta 《Journal of biological inorganic chemistry》1997,2(3):320-326
The effect of aluminum ions on the binding properties of α-chymotrypsin has been studied. The results show that aluminum
does not affect the catalytic rate constant k
cat, but it acts as an enzyme activator favoring the binding of the substrate to the catalytic site (i.e. decreasing K
m). Furthermore, aluminum binding to α-chymotrypsin displays about a threefold decrease in its affinity for the macromolecular
inhibitor bovine pancreatic trypsin inhibitor (BPTI). Altogether, the different effect of aluminum on the binding of synthetic
substrates (e.g. N-α-benzoyl-l-tyrosine ethyl ester, BTEE) and macromolecular inhibitors (e.g. BPTI) to α-chymotrypsin suggests the occurrence of an aluminum-linked
conformational change in the enzyme molecule which brings about a marked structural change at the primary and secondary recognition
sites for substrates and inhibitors. The modulative effect exerted by aluminum on the enzyme hydrolytic activity has been
investigated also as a function of pH. The ion-linked effect appears to be dependent on the pH in a complex fashion, which
suggests that aluminum binding is controlled by the protonation of at least two classes of residues on the enzyme molecule.
Received: 5 December 1996 / Accepted: 11 March 1997 相似文献
13.
The main objective of this study was to analyze the differences in profiles of RNase activities from triticale embryos (Triticosecale, cv. Ugo) between dormant and non-dormant caryopses and to determine the influence of exogenous abscisic acid (ABA) on the
activities of these enzymes. The major RNase from the examined tissue was detected following SDS-PAGE, with substrate-based
gel assay, described by Yen and Green (Plant Physiol 97:1487–1493, 1991). The activities of enzymes were characterized according to their pH optima, ion dependence, EDTA sensitivity and DNase activity.
In embryos with arrested growth (in a natural way by dormancy or artificially by ABA treatment), the activity of two enzymes—24
and 27 kDa—belonging to class I RNases was completely inhibited, whereas that of two other RNases of this family—23 and 25 kDa—was
detectable. However, the activity of the class I ribonucleases (enzymes responsible for cellular Pi release) was very low. Moreover, in contrast with non-dormant caryopses, imbibing embryos of dormant or ABA-treated seeds
contained 13- and 14-kDa enzymes. These enzymes have not been classified so far, and their specific properties are different
from the generally accepted properties of ribonucleolytic enzymes. In addition to the above results, the Pi content in the analyzed samples was determined by the Ames (Methods Enzymol 8:115–118, 1966) method. The results suggest a very low and constant level of inorganic phosphate in dormant samples as well as an evidently
decreasing Pi content in embryos under the influence of ABA treatment. The inhibition of the class I RNases activity induced by abscisic
acid implies that one of the roles of ABA in seed dormancy may consist in arresting the catabolic release of Pi, which results in retarding the embryo’s growth. 相似文献
14.
Moldogazieva NT Shaitan KV Antonov MY Vinogradova IK Terentiev AA 《Biochemistry. Biokhimii?a》2011,76(12):1321-1336
Conformational and dynamic properties of proteins and peptides play an important role in their functioning. However, mechanisms
that underlie this influence have not been fully elucidated. In the present work we computationally constructed analogs of
heptapeptide AFP14–20 (LDSYQCT) — one of the biologically active sites of human α-fetoprotein (AFP) — to study their conformational and dynamic
properties using molecular dynamics simulation. Analogs were obtained by point substitutions of amino acid residues taking
into account differences in their physicochemical properties and also on the basis of analysis of amino acid substitutions
in the AFP14–20-like motifs revealed in different physiologically active proteins. It is shown that changes in conformational mobility of
amino acid residues of analogs are due to disruption or arising of intramolecular interactions that, in turn, determine existence
of steric restrictions during rotation around covalent bonds of the peptide backbone. Substitution of an amino acid by another
one with significant difference in physicochemical properties may not lead to remarkable changes in conformational and dynamic
properties of the peptide if intramolecular interactions remain unchanged. 相似文献
15.
Different pH control agents (NaOH/H2SO4—SodSulp, NaOH/CH3COOH—SodAcet, NH4OH/CH3COOH—AmmoAcet and NH4OH/H2SO4—AmmoSulp) were used to investigate their effects on growth, enzyme production (alkaline protease and amylase), and entomotoxicity
of Bacillus thuringiensis var. kurstaki HD-1 (Btk) against eastern spruce budworm larvae (Choristoneura fumiferana) using starch industry wastewater (SIW) as a raw material in a 15-l fermentor. AmmoSulp and SodSulp were found to be the
best pH control agents for alkaline protease and amylase production, respectively; whereas, the fermented broth obtained by
using SodAcet as pH control agents recorded the highest delta-endotoxin production of 1043.0 mg/l and entomotoxicity value
18.4 × 109 SBU/l. Entomotoxicity of re-suspended centrifuged pellet in one-tenth of original volume in case of SodAcet as pH control
agents was 26.7 × 109 SBU/l and was the highest value compared to three other pH control agents. 相似文献
16.
Andrzej Ka mierczak 《Acta Physiologiae Plantarum》2005,27(4):447-454
One of the prime precursor for ethylene synthesis — L-methionine and the inhibitor of 1-aminocyclopropane-1-carboxylic acid
oxidase (ACO) — Co2+-were tested for their effects on sex expression and development of Anemia phyllitidis fern gametophytes. Five concentrations of both chemicals (0, 10, 25, 50, 100 μM) were analysed with reference to antheridia
and archegonia formation, number and size of cells as well as thalli length using the three-zone model of gametophyte structure.
Both substances, however at different concentrations, enhanced the number of GA3-induced antheridia and similarly stimulated the cell number and inhibited thalli length. Both of them at 100 μM concentrations
without GA3 induced meristematic area formation while methionine also induced archegonia in the apical parts of gametophytes. These findings
correspond with the previous observations concerning the important role of ethylene synthesis precursor (ACC) in controlling
gibberellic acid-induced male sex expression in ferns and broaden the knowledge about the mechanisms of fern gametophyte development. 相似文献
17.
D. I. Bashmakov N. A. Pynenkova K. A. Sazanova A. S. Lukatkin 《Russian Journal of Plant Physiology》2012,59(1):59-64
We studied the influence of a synthetic cytokinin-like growth regulator (Cytodef) and heavy metal ions—Pb2+, Sr2+, Zn2+, and Ni2+—on generation of superoxide anion (O2⊙−), lipid peroxidation, and carotenoids content in leaves of 7-day-old cucumber plants (Cucumis sativus L., cv. Izyashchnyi). In some instances Cytodef reduced the toxicity of heavy metals: it mitigated the negative effect of
metals on oxidative processes and elevated the concentration of antioxidants (carotenoids). 相似文献
18.
M. A. Zenkova N. L. Chumakova A. V. Vlassov N. I. Komarova A. G. Venyaminova V. V. Vlassov V. N. Silnikov 《Molecular Biology》2000,34(3):390-394
The mechanism of hydrolysis of RNA substrates—diribonucleoside monophosphate CpA and decaribonucleotide UUCAUGUAAA—by chemical
constructs functionally mimicking ribonuclease A was studied. It is shown that RNA cleavage by chemical RNases 2L2 and 2D3
proceeds similar to the RNase A-induced RNA hydrolysis through 2′,3′-cyclophosphate as an intermediate product. A comparison
of hydrolyses of CpA in water and D2O revealed an isotope effect (K
H/K
D=2.28), which implies acid-base catalysis at the limiting stage of the reaction. Two feasible mechanisms of RNA hydrolysis
by chemical RNases (linear and adjacent) are discussed. 相似文献
19.
Thomas Deforet Pierre Marmonier Dominique Rieffel Nadia Crini Patrick Giraudoux Daniel Gilbert 《Hydrobiologia》2009,623(1):235-250
The changes in both physical and chemical properties of interstitial water were investigated within a large gravel bar to
determine if the parafluvial zone was a hotspot for nutrient transformations in a lowland eutrophic river, the Doubs (Eastern
France). Interstitial water was sampled in 30 piezometers along five transects across the gravel bar, surface water was sampled
in main and chute channels. Five campaigns of sampling were performed among summer and winter. In both interstitial and surface
samples, water chemistry (electrical conductivity, pH, chloride, dissolved oxygen concentrations—DO) and nutrient concentrations
(nitrate—NO3
−, ammonium—NH4
+, soluble reactive phosphorus—SRP, dissolved organic carbon—DOC) were measured. Moreover, temperature, water level, sediment
grain size distribution and total bacterial abundance were assessed along a flowpath through a lateral gravel bar of the Doubs
River. Measurements of water table elevation in the bar, main and chute channels indicated that the parafluvial flowpath was
perpendicular to the main channel. Very low changes in chloride concentration and electrical conductivity showed minor groundwater
input along the flowpath. The parafluvial zone was 0.9 m thick under the mean piezometric level, hydraulic gradients along
the flowpath were 0.3%, and the discharge of interstitial water through the bar calculated at low flow was 40.6 m3 day−1. Most changes in interstitial nutrients occurred during the warm season, suggesting that biotic mechanisms occurred. Along
the flowpath, DO, DOC, and bacterial abundance declined, while phosphate increased. Temporal trends of nitrate were less clear,
exhibiting a slight increase during spring (organic matter biodegradation) and a decrease during summer (denitrification).
Using the parafluvial discharge and nutrient concentrations of water infiltrating into and seeping from the gravel bar, the
retention capacity of the bar was 171 gC day−1 for DOC and 48.3 gN day−1 for nitrate. Phosphate production ranged from 0.65 to 2.3 gP day−1. These values were low compared to the nutrient fluxes in the river Doubs, suggesting a minimal local impact of the parafluvial
zone in regulating of river pollution.
Handling editor: J. Padisak 相似文献
20.
Serotonergic Agonists Inhibit Calcium-Activated Potassium and Voltage-Dependent Sodium Currents in Rat Taste Receptor Cells 总被引:3,自引:0,他引:3
Recently we reported that rat taste receptor cells respond to the neurotransmitter serotonin with an inhibition of a calcium-activated
potassium current [17]. In the present study, this observation is confirmed and extended by studying the effects of an array
of serotonergic agonists on membrane properties, calcium-activated potassium current, and voltage-dependent sodium current
in taste receptor cells using the patch-clamp recording technique in the whole-cell configuration. Serotonergic inhibition
of calcium-activated potassium current was mimicked by the agonists N-(3-trifluoromethylphenyl)piperazine and by (±)-2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydronaphthalene.
Both produced reversible inhibition of K
Ca
as well as significantly increasing the input resistance of the cell. The agonists 1-(1-naphthyl)piperazine and buspirone
(both serotonin receptor 1A agonists) were similarly effective in reducing K
Ca
. Outward current was unaffected by application of phenylbiguanide, a serotonin receptor 3 agonist, though current was affected
by subsequent application of (±)-2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydronaphthalene. Two agonists—N-(3-trifluoromethylphenyl)piperazine
and (±)-2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydronaphthalene—were also tested on voltage-dependent sodium currents; both
were effective and reversible in reducing its magnitude at a variety of applied potentials. These data are consistent with
the notion that serotonin effects in rat taste receptor cells are mediated by serotonin 1A receptors, though other receptor
subtypes may be additionally expressed. Serotonin may affect the taste cell electrical properties during active stimulation
in a paracrine fashion.
Received: 10 May 1999/Revised: 27 September 1999 相似文献