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1.
Rajendra Prasad Roy Parimala Nacharaju Ronald L. Nagel A. Seetharama Acharya 《Journal of Protein Chemistry》1995,14(2):81-88
Interspecies hybrids of HbA and Hb from mouse C57BL/10 [
2
M
2
H
and
2
H
2
M
(H=human, M=mouse)], representing 19 and 27 sequence differences per dimers (as compared with human dimer) have been generatedin vitro. The efficiency of the assembly of the interspecies hybrids by the alloplex intermediate pathway is about twofold higher than the low-pH-mediated subunit approach. The interspecies hybrids exhibit a cooperative O2 binding. The intrinsic O2 affinity of mouse Hb is slightly lower than HbA, while the 2,3-diphosphoglycerate (DPG) effect is comparable. Interestingly, the interspecies hybrid
2
M
2
H
has high O2 affinity (compared to either human or mouse Hb), while the interspecies hybrid
2
H
2
M
exhibits a very low O2 affinity. These results suggest that the mouse chain generates a tetramer with very low oxygen affinity. However, the complementarity of the mouse and chains generates a set of unique interactions that compensate for the low-oxygen-affinity propensity of the mouse chain. DPG binds the tetramer in the central cavity formed by the two subunits, hence the DPG effects on the interspecies hybrids should be as in the parent molecule. However, the results of the present study demonstrate that the DPG binding pocket is influenced by the nature of the chain present in the tetramer. The mouse chain reduces considerably the DPG right shift of the O2 affinity of the human-chain containing hybrid. Sequence analysis suggest that perturbations of the
1
1 (not the
1
2) are communicated to the DPG binding pocket in the presence of the alien subunit, and are the primary determinant of the ligand binding properties. The results have implications for the design of Hb-based blood substitutes and understanding of the inhibitory potential of mouse chains in transgenic mouse expressing human
S chains. 相似文献
2.
The Ca2+ channel 1B subunit is a pore-forming component capable of generating N-type Ca2+ channel activity. Although N-type Ca2+ channel plays a role in a variety of neuronal functions, 1B-deficient mice exhibit normal life span without apparent abnormalities of behavior, histology or plasma norepinephrine level, presumably owing to compensation by some other Ca2+ channel 1 or subunit. In this study, we studied the levels of 1A, 1C, 1D, 1E, 1, 2, 3 and 4 mRNAs in adrenal gland of 1B-deficient mice. The 1A mRNA in homozygous mice was expressed at higher level than in wild or heterozygous mice, but no difference in the expression levels of 1C, 1D, 1E, 1, 2, 3 and 4 was found among wild, heterozygous and homozygous mice. The protein level of 1A in homozygous mice was also expressed at higher level than in wild or heterozygous mice. To examine whether increased expression is induced by cis-regulatory element within 5-upstream region of 1A gene, we examined lacZ expression in 1B-deficient × 1A6.3-lacZ mice (carrying a 6.3-kb 5-upstream fragment of 1A gene fused to E. coli lacZ reporter gene), which express lacZ in medullar chromaffin cells, but not in cortex. The levels of lacZ expression in homozygous 1B-deficient × 1A6.3-lacZ mice were higher than in wild or heterozygous mice. Therefore, a possible explanation of the normal behavior and plasma norepinephrine level of 1B-deficient mice is that compensation by 1A subunit occurs and that 6.3-kb 5-upstream region of 1A gene contains enhancer cis-element(s) for compensation in adrenal medulla chromaffin cells. (Mol Cell Biochem 271: 91–99, 2005) 相似文献
3.
Ahlert Schmidt 《Archives of microbiology》1977,112(3):263-270
Crude extracts of Rhodospirillum rubrum catalyzed the formation of acid-volatile radioactivity from (35S) sulfate, (35S) adenosine-5-phosphosulfate, and (35S) 3-phosphoadenosine-5-phosphosulfate. An enzyme fraction similar to APS-sulfotransferases from plant sources was purified 228-fold from Rhodospirillum rubrum. It is suggested here that this enzyme is specific for adenosine-5-phosphosulfate, because the purified enzyme fraction metabolized adenosine-5-phosphosulfate, however, only at a rate of 1/10 of that with adenosine-5-phosphosulfate. Further, the reaction with 3-phosphoadenosine-5-phosphosulfate was inhibited with 3-phosphoadenosine-5-phosphate whereas this nucleotide had no effect on the reaction with adenosine-5-phosphosulfate. For this activity with adenosine-5-phosphosulfate the name APS-sulfotransferase is suggested. This APS-sulfotransferase needs thiols for activity; good rates were obtained with either dithioerythritol or reduced glutathione; other thiols like cysteine, 2-3-dimercaptopropanol or mercaptoethanol are less effective. The electron donor methylviologen did not catalyze this reaction. The pH-optimum was about 9.0; the apparent K
m for adenosine-5-phosphosulfate was determined to be 0.05 mM with this so far purified enzyme fraction. Enzyme activity was increased with K2SO4 and Na2SO4 and was inhibited by 5-AMP. These properties are similar to assimilatory APS-sulfotransferases from spinach and Chlorella.Abbreviations APS
adenosine-5-phosphosulfate
- PAPS
3-phosphoadenosine-5-phosphosulfate
- 5-AMP
adenosine-5-monophosphate
- 3-AMP
adenosine-3-monophosphate
- 3-5-ADP
3-phosphoadenosine-5-phosphate (PAP)
- DTE
dithiorythritol
- GSH
reduced glutathione
- BAL
2-3-dimercaptopropanol 相似文献
4.
The role of de novo synthesis in the regulation of adenosine 5-phosphosulfate sulfotransferase activity by H2S inLemna minor L. was investigate using density labeling with15N applied as15NO
3
–
in the culture medium. While adenosine 5-phosphosulfate sulfotransferase activity was rapidly reduced by H2S and rapidly recovered upon removal of H2S, O-acetyl-L-serine sulfhydrylase (EC 4.2.99.8) did not show changes in extractable activity in response to H2S and could therefore be used as an internal marker enzyme for density labeling. The incorporation of15N into adenosine 5-phosphosulfate sulfotransferase was strongly reduced upon transfer of plants into a H2S-containing atmosphere. Half-maximal labeling was reached only after 70–80 h compared to 40–50 h in the control. After removal of H2S, adenosine 5-phosphosulfate sulfotransferase activity increased to the initial level within 20 h, and the enzyme reached halfmaximal labeling after only 15 h. The time course of the density increase of O-acetyl-L-serine sulfhydrylase was not affected very significantly by H2S. These results provide evidence that de novo synthesis of enzyme protein is involved in the regulation of adenosine 5-phosphosulfate sulfotransferase activity by H2S.Abbreviations APS
adenosine 5-phosphosulfate
- APSSTase
adenosine 5-phosphosulfate sulfotransferase
- BSA
Bovine serum albumine
- DTE
dithioerythritol
- OAS
O-acetyl-L-serine
- OASSase
O-acetyl-L-serine sulfhydrylase
- POPOP
1,4-bis-(5-phenyl-2-oxazolyl)-benzene
- PPO
2,5-diphenyloxazole
This is no. 9 in the series Regulation of Sulfate Assimilation in Plants 相似文献
5.
Isopropylidenation of lactose with 2,2-dimethoxypropane in the presence ofp-toluenesulfonic acid gave two products, which were identified by1H- and13C-NMR as 2,35,63,4-tri-O-isopropylidenelactose dimethyl acetal (1) and its 6-O-(2-methoxy)-isopropyl derivative (2). These products were used for the synthesis of 2-O-methyllactose (7), 2,6-di-O-methyllactose (9) and 2-O-benzyllactose (13). 相似文献
6.
R. M. Kondratenko L. A. Baltina S. R. Mustafina E. V. Vasil'eva R. Pompei D. Deidda O. A. Plyasunova A. G. Pokrovskii G. A. Tolstikov 《Russian Journal of Bioorganic Chemistry》2004,30(3):275-282
Glycyrrhizic acid and its 30-methyl ester were conjugated with 2-amino-1,3,4,6-tetra-O-acetyl-2-deoxy--D-glucopyranose, 2,3,4,6-tetra-O-acetyl--D-glucopyranosyl amine, 2,3,4-tri-O-acetyl--L-arabinopyranosyl amine, 2-acetamido-2-deoxy--D-glucopyranosyl amine, and -D-galactopyranosyl amine using N,N-dicyclohexylcarbodiimide and its mixtures with N-hydroxybenzotriazole. Structures of the conjugates were confirmed by IR, UV, 1H, and 13C NMR spectroscopy. The glycoconjugate with the residues of 2-acetamido-2-deoxy--D-glucopyranosyl amine in the carbohydrate part of its molecule exhibited antiviral activity (ID50 4 g/ml) toward the herpes simplex type 1 virus (HSV-1) in the VERO cell culture. Two compounds demonstrated anti-HIV-1 activity (50–70% inhibition of p24) in a culture of MT-4 cells at concentrations of 0.5–20 g/ml. 相似文献
7.
Hans Mulder Harry Schachter Jerry R. Thomas Koen M. Halkes Johannis P. Kamerling Johannes F. G. Vliegenthart 《Glycoconjugate journal》1996,13(1):107-113
Connective tissue of the freshwater pulmonateLymnaea stagnalis was shown to contain fucosyltransferase activity capable of transferring fucose from GDP-Fuc in 1–2 linkage to terminal Gal of type 3 (Gal1–3GalNAc) acceptors, and in 1–3 linkage to GlcNAc of type 2 (Gal1–4GlcNAc) acceptors. The 1–2 fucosyltransferase was active with Gal1–3GalNAc1-OCH2CH=CH2 (K
m=12 mM,V
max=1.3 mU ml–1) and Gal1–3GalNAc (K
m=20 mM,V
max=2.1 mU ml–1), whereas the 1–3 fucosyltransferase was active with Gal1–4GlcNAc (K
m=23 mM,V
max=1.1 mU ml–1). The products formed from Gal1–3GalNAc1-OCH2CH=CH2 and Gal1–4GlcNAc were purified by high performance liquid chromatography, and identified by 500 MHz1H-NMR spectroscopy and methylation analysis to be Fuc1–2Gal1–3GalNAc1-OCH2CH=CH2 and Gal1–4(Fuc1–3)GlcNAc, respectively. Competition experiments suggest that the two fucosyltransferase activities are due to two distinct enzymes.Abbreviations 2Fuc-T
1–2 fucosyltransferase
- 3Fuc-T
1–3 fucosyltransferase
- MeO-3Man
3-O-methyl-D-mannose
- MeO-3Gal
3-O-methyl-D-galactose 相似文献
8.
Gijsbertus W. van Eijk Henri J. Roeijmans Hubertus A. van der Aa 《Antonie van Leeuwenhoek》1988,54(4):325-330
Clumps of white crystals present in 40-day-old malt agar cultures of Holwaya mucida were isolated as long white needles by crystallization from ethanol following short extraction with chloroform. The levorotary compound ([]
289
21
=-193.8°) was recognized as a -lactone (C17H20O5) by infrared and mass spectrometry. It was identified as 7-methoxy-3a, 10b-dimethyl-1, 2, 3, 3a, 5a, 7, 10b, 10c-octahydro-4H, 9H-furo[2, 3, 4 : 4, 5]naphtho[2, 1-c]pyran-4, 9-dione, a labdane-derived compound known as antibiotic LL-Z1271. Preparative thin-layer chromatography of the mother liquor afforded 2 minor metabolites. One was identified as LL-Z1271, the demethylated analogue of LL-Z1271. The other one named LL-Z1271, was recognized as a compound related to and : its structure could not be fully elucidated.
H. mucida (anamorph: Crinula calciiformis) has no taxonomic relationship with two other LL-Z1271 producing species viz. Acrostalagmus sp. (= Acremonium cf. atrogriseum) and Oidiodendron truncatum. 相似文献
9.
K. Kitamura C. S. Davies N. C. Nielsen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,68(3):253-257
Summary A cultivar lacking the glycinin subunit A5A4B3 (Raiden) was crossed with one lacking the -subunit of -conglycinin (Keburi). Analysis of F2 and F3 progeny indicated that the missing bands of the A5A4B3 and the -subunit were each controlled by a recessive allele of two independently segregating genes. Gene symbols Gy
4/gy
4 and Cgy
1/cgy
1 were proposed for the genes which confer the presence or absence of the glycinin and conglycinin subunits, respectively.Cooperative research of USDA-ARS and the Indiana Agric. Exp. Stn., Purdue Univ., West Lafayette, IN 47907, USA. Indiana Agric. Exp. Stn. Journal Article 9675. Financial support from the American Soybean Association Research Foundation is gratefully acknowledged 相似文献
10.
Lai-Xi Wang Nadejda V. Pavlova Su-Chen Li Yu-Teh Li Yuan C. Lee 《Glycoconjugate journal》1996,13(3):359-365
4-Methylumbelliferyl 6-O-benzyl--d-lactoside (6Bn-MU-Lac) and some related compounds were synthesizedvia different selective reactions including phase-transfer glycosylation. Their suitability as substrates for a fluorometric assay of ceramide glycanase (CGase) was evaluated. Among others, the 6Bn-MU-Lac, which is resistant to exogalactosidase, was found to be a suitable substrate for routine assay of the CGase activity. For American leech CGase, theK
m value is 0.232 mM at pH 5.
Abbreviations: CGase, ceramide glycanase; Gal, galactose; Glc, Glucose; Lac, lactose; MU, 4-methylumbelliferone; MU-Lac, 4-methylumbelliferyl -d-lactoside; bBn-Lac, 6-O-benzyl-lactose; 6Bn-MU-Lac, 4-methylumbelliferyl 6-Obenzyl--d-lactoside; 46Bd-MU-Lac, 4-methylumbelliferyl 4,6-O-benzylidene--d-lactoside; MU-Cel, 4-methylumbellifery -d-cellobioside; 46Bd-MU-Cel, 4-methylumbelliferyl 4,6-O-benzylidene--d-cellobioside; TLC, thin layer chromatography;1H-NMR, proton nuclear magnetic resonance; GSL, glycosphingolipids; CSA, 10-camphorsulfonic acid. See Scheme 1 for chemical structures. 相似文献
11.
Jacques Raymond Brahim Mimouni Jean-Louis Azanza 《Plant Systematics and Evolution》1994,193(1-4):69-79
The seed storage globulins from sixHelianthus and four hybrids were studied using mono and bidimensional gel SDS electrophoresis (+ 2 mercaptoethanol). The polypeptide composition of each subunit was determined. Different pairs are specifically expressed according to the species studied. Three typical patterns were discriminated. All the studied species exhibit five subunits: two of them are expressed in all the species (11 and 22). The subunit corresponding to the 11 pair is present inH. petiolaris and in the three populations ofH. annuus studied. The 2b2 pair is common toH. annuus andH. argophyllus. H. petiolaris presents two specific 2a2 and 44 pairs andH. annuus a specific 33 pair. InH. argophyllus 11 33 or 44 are never observed but are replaced by 13 and 31 pairs. Some globulins, poorly represented, are of forms but present chains of higher molecular weights (in the range 54–56 kDa). Expressing variations in the banding patterns between these species by the use of a similarity index reveals complete identity between the three populations ofH. annuus. Identity between the twoH. petiolaris studied is also observed.H. annuus andH. argophyllus appear to be closer to each other thanH. petiolaris concerning the seed storage globulins. 相似文献
12.
Candida antarctica B lipase-catalysed alcoholysis of 2, 3, 5-tri-O-hexanoyluridine (1a), 2, 3, 5-tri-O-dodecanoyluridine (1b), 2, 3, 5-tri-O-hexanoylinosine (1c) and 2, 3, 5-tri-O-dodecanoylinosine (1d) proceeded regioselectively to produce the corresponding 2, 3-di-O-acylribonucleosides 2a–d, providing a simple and efficient access to these new lipophilic compounds. Contrasting to the alcoholysis, enzymatic hydrolysis of 1a–d using different enzymes and experimental conditions did not proceed regioselectively. 相似文献
13.
S. Hayashi K. Matsuzaki Y. Takasaki H. Ueno K. Imada 《World journal of microbiology & biotechnology》1992,8(3):276-279
-Fructofuranosidase fromAspergillus japonicus, which produces 1-kestose (O--d-fructofuranosyl-(21)--d-fructofuranosyl -d-glucopyranoside) and nystose (O--d-fructofuranosyl-(21)--d-fructofuranosyl-(21)--d-fructofuranosyl -d-glucopyranoside) from sucrose, was purified to homogeneity by fractionation with calcium acetate and ammonium sulphate and chromatography with DEAE-Cellulofine and Sephadex G-200. Its molecular size was estimated to be about 304,000 Da by gel filtration. The enzyme was a glycoprotein which contained about 20% (w/w) carbohydrate. Optimum pH for the enzymatic reaction was 5.5 to 6. The enzyme was stable over a wide pH range, from pH 4 to 9. Optimum reaction temperature for the enzyme was 60 to 65°C and it was stable below 60°C. The Km value for sucrose was 0.21m. The enzyme was inhibited by metal ions, such as those of silver, lead and iron, and also byp-chloromercuribenzoate. 相似文献
14.
The white rot basidiomycete Phanerochaete chrysosporium metabolized 4-ethoxy-3-methoxyphenyl-glycerol--guaiacyl ether (V) in low nitrogen, stationary cultures under which conditions the ligninolytic enzyme system is expressed. 4-Ethoxy-3-methoxyphenylglycerol XIII, guaicol and 4-ethoxy-3-methoxybenzyl alcohol (II) were isolated as metabolic products. Exogenously added XIII was rapidly converted to 4-ethoxy-3-methoxybenzyl alcohol indicating that it is an intermediate in the metabolism of V. P. chrysosporium also metabolized 1-(4-ethoxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-3-hydroxypropane VI. The degradation pathway for this dimer also included initial -ether cleavage and -hydroxylation of the diol product 1-(4-ethoxy-3-methoxyphenyl) 2,3 dihydroxypropane (XI) to yield the triol XIII which was cleaved at the , bond to yield 4-ethoxy-3-methoxybenzyl alcohol. Finally P. chrysosporium also cleaved the dimer 1-(4-ethoxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-hydroxypropane (VIII) at the -ether linkage yielding 1-(4-ethoxy-3-methoxyphenyl) 1,2 dihydroxypropane (IX) which was subsequently cleaved at the , bond to yield II. All of the results indicate that oxidative -ether cleavage is an important initial reaction in the metabolism of -aryl ether lignin substructure dimeric compounds. Metabolities were identified after comparison with chemically synthesized standards by gas liquid chromatography-mass spectrometry.Abbreviations GLC
Gas liquid chromatography
- TMSi
trimethylsilyl
- TLC
thin layer chromatography 相似文献
15.
Marsh SA Pat BK Gobe GC Coombes JS 《Apoptosis : an international journal on programmed cell death》2005,10(3):657-665
Endothelial cell apoptosis contributes to atherosclerosis and may be exacerbated by oxidative stress. Results from clinical trials using antioxidant supplementation are equivocal and could be enhanced by antioxidants with additional non-antioxidant properties such as -lipoic acid and -tocopherol. The aim of this study was to investigate the effects of these antioxidants on cytoprotective pathways and endothelial apoptosis. Endothelial cells were incubated with -lipoic acid and -tocopherol, alone or in combination, prior to incubation with H2O2 or staurosporine. -lipoic acid pre-treatment alone increased caspase-3 activity in a dose-dependent manner. Both H2O2 and staurosporine increased DNA fragmentation and caspase-3 activity and pre-treatment of cells with -lipoic acid and/or -tocopherol failed to prevent stress-induced apoptosis. Neither antioxidant treatments nor apoptotic inducers alone altered expressions of Bcl-2, Bax, HSP70 or pERK1/2 or pJNK. -lipoic decreased pERK2 in staurosporine-treated cells in a dose-dependent manner. These findings indicate that pre-incubation with -lipoic acid and -tocopherol, alone or in combination, does not protect against oxidative- or non-oxidative-induced apoptosis in endothelial cells. Moreover, we have demonstrated a non-antioxidant, dose-dependent role of -lipoic acid in caspase-3 and ERK2 activation. These data provide an insight and indicate caution in the use of high doses of -lipoic acid as an antioxidant. 相似文献
16.
Anna Marina Liberati Michael Horisberger Monica Schippa Francesco Di Clemente Marco Fizzotti Stefano Filippo Maria Grazia Proietti Sergio Arzano Paolo Berruto Lucia Palmisano Saverio Cinieri 《Cancer immunology, immunotherapy : CII》1991,34(2):115-122
Summary Ten hairy-cell leukemia patients were treated with interferon (IFN-) at a dose rate of 2 × 106 IU/m2 × 5 days for 4 weeks (induction therapy) and, thereafter, at the same dose three times a week for 11 months (maintenance therapy). The effect of this treatment on serum neopterin, 2-microglobulin, (2–5)oligoadenylate [(2–5)A
n
] levels, intracellular (2–5)A
n
values and human Mx protein synthesis was analysed. There were significant rises in serum neopterin and (2–5)A
n
levels during both induction and maintenance, whereas 2-microglobulin levels rose only during induction. Rises in intracellular (2–5)A
n
were documented mainly during induction, but they were not significantly higher than pretherapy values. IFN provoked an increase in human Mx protein synthesis over the entire induction — maintenance period, but was only significantly higher than baseline during induction. All markers proved useful for monitoring the effects of IFN dose schedules, but were not predictive of clinical outcome. Natural killer activity and IFN production, which were initially defective, followed a different trend from that of the other factors studied, in that increases were documented only late in the course of therapy when the disease was already in remission. 相似文献
17.
Shkumatov V. M. Usova E. V. Radyuk V. G. Kashkan Zh. N. Kovganko N. V. Juretzek T. Mauersberger S. 《Russian Journal of Bioorganic Chemistry》2003,29(6):581-587
Progesterone biotransformation with recombinant yeasts Yarrowia lipolytica E129A15 and Saccharomyces cerevisiae GRF18/YEp5117 expressing bovine adrenocortical cytochrome P-45017 yielded 17-hydroxyprogesterone and two diols, 17,20- and 17,20-dihydroxypregn-4-en-3-ones. The oxidation of mixtures of the three steroids with chromic acid resulted in the cleavage of 17–20 bonds in the diols with the formation of androst-4-ene-3,17-dione. The biotransformation of pregn-4-ene-20-ol-3-one by means of Y. lipolytica E129A15 was accompanied by the following reactions: the primary oxidation of these compounds to progesterone and the subsequent successive reactions of 17-hydroxylation and 20- and 20-reduction. The results widen the possibilities of enzymatic and chemical modifications of steroids. 相似文献
18.
R. Lohrmann 《Journal of molecular evolution》1977,10(2):137-154
Summary Adenosine 5-phosphoramidates form when solutions containing adenosine 5-polyphosphates pnA (n 3) or P1, P2-diadenosine 5-diphosphate and amines are allowed to dry out. Mg ions catalyze these reactions. We have studied systems containing ammonia, imidazole, glycine, ethylenediamine and histamine. The yields of adenosine 5-phosphoramidates range from 10–50 % based on the nucleotide. The prebiotic significance of the reactions is discussed.Abbreviations Im
imidazole
- hist
histamine
- gly
glycine
- en
ethylenediamine
- CDI
1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride
- EDTA
ethylenediaminetetraacetic acid
- A
adenosine
- Pn (n = 1, 2 )
linear polyphosphate containing n phosphate residues
- pnA
adenosine 5-polyphosphate containing n phosphate residues
- ADP
adenosine 5-diphosphate
- ATP
adenosine 5-triphosphate
- AppA
P1, P2-diadenosine 5-diphosphate
- gly-pA
adenylyl-(5N)-glycine
- ImpA
adenosine 5-phosphorimidazolide
- NH2-pA
adenosine 5-phosphoramidate
- en-pA
adenylyl-(5N)-ethylenediamine
- hist (NH) - pA
adenosine 5-phospho-[2-(4-imidazolyl)-ethylamide]
- hist(Im)-pA
adenosine 5-phospho-[4-(2-aminoethyl)-imidazolide]
- enP1,2
phosphoramidates of ethylenediamine derived from H3PO4 and H4P2O7 相似文献
19.
Addition of ammonium to N2 fixing cultures of Azotobacter vinelandii, Klebsiella pneumoniae and Clostridium pasteurianum rapidly reduced the intracellular levels of guanosine 5-diphosphate 3-diphosphate (ppGpp) by 70–90%. This change might reflect a regulatory role of ppGpp in nitrogen metabolism.Abbreviations ppGpp
guanosine 5-diphosphate 3-diphosphate 相似文献
20.
Sources of nitrate in rivers draining sixteen watersheds in the northeastern U.S.: Isotopic constraints 总被引:3,自引:4,他引:3
Mayer Bernhard Boyer Elizabeth W. Goodale Christine Jaworski Norbert A. van Breemen Nico Howarth Robert W. Seitzinger Sybil Billen Gilles Lajtha Kate Nadelhoffer Knute Van Dam Douwe Hetling Leo J. Nosal Miloslav Paustian Keith 《Biogeochemistry》2002,(1):171-197
The feasibility of using nitrogen and oxygenisotope ratios of nitrate (NO3
–) forelucidating sources and transformations ofriverine nitrate was evaluated in a comparativestudy of 16 watersheds in the northeastern U.S.A. Stream water was sampled repeatedly at theoutlets of the watersheds between January andDecember 1999 for determining concentrations,15N values, and 18Ovalues of riverine nitrate.In conjunction with information about land useand nitrogen fluxes,15Nnitrate and18Onitrate values providedmainly information about sources of riverinenitrate. In predominantly forested watersheds,riverine nitrate had mean concentrations ofless than 0.4 mg NO3
–-N L–1,15Nnitrate values of lessthan +5, and 18Onitratevalues between +12 and +19. This indicatesthat riverine nitrate was almost exclusivelyderived from soil nitrification processes withpotentially minor nitrate contributions fromatmospheric deposition in some catchments. Inwatersheds with significant agricultural andurban land use, concentrations of riverinenitrate were as high as 2.6 mg NO3
–-NL–1 with 15Nnitratevalues between +5 and +8 and18Onitrate values generallybelow +15. Correlations between nitrateconcentrations, 15Nnitratevalues, and N fluxes suggest that nitrate inwaste water constituted a major, and nitrate inmanure a minor additional source of riverinenitrate. Atmospheric nitrate deposition ornitrate-containing fertilizers were not asignificant source of riverine nitrate inwatersheds with significant agricultural andurban land use. Although complementary studiesindicate that in-stream denitrification wassignificant in all rivers, the isotopiccomposition of riverine nitrate sampled at theoutlet of the 16 watersheds did not provideevidence for denitrification in the form ofelevated 15Nnitrate and18Onitrate values. Relativelylow isotopic enrichment factors for nitrogenand oxygen during in-stream denitrification andcontinuous admixture of nitrate from theabove-described sources are thought to beresponsible for this finding. 相似文献