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101.
Plant-mediated methane emission from an Indian mangrove 总被引:3,自引:0,他引:3
Ramachandran Purvaja Ramachandran Ramesh Peter Frenzel† 《Global Change Biology》2004,10(11):1825-1834
Mangroves have been considered for a long time to be a minor methane source, but recent reports have shown that polluted mangroves may emit substantial amounts of methane. In an unpolluted Indian mangrove, we measured annual methane emission rates of 10 g CH4 yr?1 from the stands of Avicennia marina. This rate is of the same order of magnitude as rates from Northern wetlands. Methane emission from a freshwater‐influenced area was higher, but was lower from a stunted mangrove growing on a hypersaline soil. Methane emission was mediated by the pneumatophores of Avicennia. This was consistent with the methane concentration in the aerenchyma, which decreased on average from 350 ppmv in the cable roots to 10 ppmv in the emergent part of the pneumatophores. However, the number of pneumatophores varied seasonally. The minimum number occurred during the monsoon season, which reduced methane emissions largely. Ebullition from unvegetated areas may also be important, at least during monsoon season when measured bubble fluxes were occasionally about five times as high as pneumatophore‐mediated emissions. 相似文献
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Hétu PO Ouellet M Falgueyret JP Ramachandran C Robichaud J Zamboni R Riendeau D 《Archives of biochemistry and biophysics》2008,477(1):155-162
We have characterized the structures of cyclooxygenase-2 (COX-2) and microsomal prostaglandin E2 synthase-1 (mPGES-1) in intact cells using bifunctional and photo-activatable crosslinking agents. A dimeric complex was detected for COX-2 by both crosslinking approaches, consistent with the crystal structure of the enzyme. For mPGES-1, treatment of A549 cells with disuccinimidyl suberate yielded immunoreactive protein bands corresponding to a dimer (33 kDa) and a trimer (45 kDa), as observed for the isolated enzyme. Photo-crosslinking with photoactivatable methionine in intact cells generated complexes with molecular weights corresponding to the dimer (33 kDa) and two putative trimer forms (50 and 55 kDa). Treatment with the selective mPGES-1 inhibitor MF63 prevented the formation of the 50 and 55 kDa crosslinked complexes, while an inactive structural analogue had no effect. Our data indicate that COX-2 forms a dimer in intact cells and that mPGES-1 has an oligomeric structure that can be disrupted by a selective inhibitor. 相似文献
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Theory of the non-planar peptide unit 总被引:2,自引:0,他引:2
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Achary A Hariharan KA Bandhyopadhyaya S Ramachandran R Jayaraman K 《Biotechnology and bioengineering》1997,55(1):148-154
D-Hydantoinases (E.C.3.5.2.2) are commercially valuable enzymes involved in the production of D-amino acids. However, commercial exploitation of the biological process is rare, mainly because sufficient details are not available on the efficient production of these enzymes by microorganisms. In the present study, Agrobacterium radiobacter was used as the source of D-hydantoinase and its production was optimized with inexpensive carbon and nitrogen sources. The four media components selected to study their effect on biomass and/or enzyme activities were molasses, ammonium nitrate, sodium di-hydrogen orthophosphate, and manganese chloride. With the use of an empirical modeling technique (response surface method), we have optimized both biomass and enzyme production in this organism, with a minimal number of batches. Experiments were performed with optimized media components to validate the model. The maximum level of enzyme and biomass obtained was 35 U/mL and 1.69 mg/mL, respectively. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 148-154, 1997. 相似文献