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991.
Matthew Kennedy Lian Yu Maria João Lima Carla S. Ascenso Christopher Czaja Isabel Moura Jose J. G. Moura F. Rusnak 《Journal of biological inorganic chemistry》1998,3(6):643-649
Desulforedoxin and the N-terminus of desulfoferrodoxin share a 36 amino acid domain containing a (Cys-S)4 metal binding site. Recombinant forms of desulforedoxin, an N-terminal fragment of desulfoferrodoxin, and two desulforedoxin
mutant proteins were reconstituted with Fe3+, Cd2+, and Zn2+ and relative metal ion affinities assessed by proton titrations. Protons compete with metal for protein ligands, a process
that can be followed by monitoring the optical spectrum of the metal-protein complex as a function of pH. For all polypeptides,
Fe3+ bound with the highest affinity, whereas the affinity of Zn2+ was greater than Cd2+ in desulforedoxin and the N-terminal fragment of desulfoferrodoxin, but this order was reversed in desulforedoxin mutant
proteins. Metal binding in both mutants was significantly impaired. Furthermore, the Fe3+ complex of both mutants underwent a time-dependent bleaching process which coincided with increased reactivity of cysteine
residues to Ellman's reagent and concomitant metal dissociation. It is hypothesized that this results from an autoredox reaction
in which Fe3+ is reduced to Fe2+ with attendant oxidation of ligand thiols.
Received: 17 June 1998 / Accepted: 3 September 1998 相似文献
992.
Masaki Ishigai Shinichi Arai Yoshihiko Ishitani Kenji Kumaki 《The Journal of steroid biochemistry and molecular biology》1998,66(5-6):281-293
After intravenous administration of the vitamin D3 analog, 22-oxacalcitriol (OCT), to normal rats plasma metabolites were investigated by HPLC, GC-MS and LC-MS. Five side-chain oxidation metabolites, 24R(OH)OCT, 24S(OH)OCT, (25R)-26(OH)OCT, (25S)-26(OH)OCT and 24oxoOCT, were identified by comparison with the corresponding synthetic compounds. These side-chain oxidation metabolites were similar to those of calcitriol [1,25(OH)2 vitamin D3] described previously. Besides these five metabolites, two unique side-chain cleavage metabolites, 20S(OH)-hexanor-OCT and 17,20S(OH)2-hexanor-OCT, were identified as main metabolites in plasma by GC-MS and LC-MS using a specific chemical reaction. Our studies suggest that OCT is extensively metabolized and circulates in blood as a number of metabolites as well as unchanged OCT. This metabolism includes both unique pathways of C23-O22 cleavage and 17-hydroxylation, in addition to the side-chain oxidation metabolites similar to those of 1,25-(OH)2D3. 相似文献
993.
富勒烯的生物活性研究进展 总被引:6,自引:0,他引:6
90年代初以来,富勒烯类化合物的生物活性逐渐引起人们的注意,初步研究表明在抗艾滋病毒、酶活性抑制、切割DNA、光动力学治疗等方面具有独特的功效.此类化合物在生化、医学、药物学等领域有良好的应用前景. 相似文献
994.
对产业生态学的基本概念、研究方法和研究热点进行了总结与评述,认为产业生态学是研究人类产业活动与自然环境相互关系的一门综合性、垮学科的应用科学。它采用工业代谢、生命周期评价和区域生态建设的方法对产业活动全过程(包括原材料采掘、原材料生产、产品制造、产品使用、产品用后处理)进行定性描述和定量模拟。产业生态学着眼于人类和生态系统的长远利益,追求经济效益、生态效益和社会效益的统一。 相似文献
995.
996.
Marina Fischer-Kowalski 《Journal of Industrial Ecology》1998,2(1):61-78
In this article, we inquire into the intellectual history ofthe application of the biological concept of metabolism to social systems-not as a metaphor; but as a material and energetic process within the economy and society vis-A-vis various natural systems. The paper reviews several scientific traditions that may contribute to such a view, including biology and ecology, social theory, cultural anthropology, and social geography It assembles widely scattered approaches dating from the 1860s onward and shows how they prepare the ground for the pioneers of "industrial metabolism" in the late 1960s. In connection to varying political perspedives, metabolism gradually takes shape as a powerful interdisciplinary concept It will take another 25 years before this approach becomes one of the most important paradigms for the empirical analysis of the society-nature-interaction across various disciplines. This later period will be the subject of part II of this literature review 相似文献
997.
Jae Young Kim In Kook Park 《The international journal of biochemistry & cell biology》1998,30(12):1337-1344
The effects of 6-aminonicotinamide (6-AN) on the levels of soluble proteins and enzyme activities in various tissues of Japanese quail were investigated. SDS-polyacrylamide gel electrophoresis showed that the soluble proteins with molecular masses corresponding to 160.4 and 52.5 kDa were either missing or present at lower concentrations in the brain of the 6-AN treated group compared to those in the control group. The soluble liver proteins with molecular masses 200, 120 and 70.5 kDa were missing in the treated group compared to those in the control while those of a molecular mass 15.1 kDa were found to be present at higher concentrations. Similarly, treatment with 6-AN decreased the concentration of soluble proteins in pectoral muscle with molecular masses 92.3, 54.5, 43.5, 41.2, 34.5, 27.5, 20.1 and 17.5 kDa and increased those with molecular masses 96.5, 37.7, 25.0, 19.3, 16.6, 13.8 and 10.8 kDa. In the heart, soluble proteins with molecular mass 84.6 kDa were increased. There was a marked reduction in the treatment group in the concentration of NAD in pectoral muscle but not in other tissues. A similar observation was also made with total RNA levels. The specific activity of malic enzyme was markedly increased by 6-AN treatment in the kidney and pectoral muscle but reduced in the liver. 6-Phosphogluconate dehydrogenase and lactate dehydrogenase activities were markedly reduced in the liver. Glyceraldehyde-3-phosphate dehydrogenase activity was significantly decreased in liver and pectoral muscle. NAD glycohydrolase activity was markedly decreased in pectoral muscle. Acetylcholinesterase activity was markedly reduced in liver but was enhanced in pectoral muscle. The results suggest that the metabolic actions of 6-AN are specific for certain proteins in the liver and muscle with the effect being most pronounced in muscle. The effects are also quite distinct from those shown by its analogue 3-acetylpyridine. 相似文献
998.
Carbon Dioxide Variation in a Hardwood Forest Stream: An Integrative Measure of Whole Catchment Soil Respiration 总被引:8,自引:3,他引:5
The concentration of CO2 in stream water is a product of not only instream metabolism but also upland, riparian, and groundwater processes and as
such can provide an integrative measure of whole catchment soil respiration. Using a 5-year dataset of pH, alkalinity, Ca2+, and Mg2+ in surface water of the West Fork of Walker Branch in eastern Tennessee in conjunction with a hydrological flowpath chemistry
model, we investigated how CO2 concentrations and respiration rates in stream, bedrock, and soil environments vary seasonally and interannually. Dissolved
inorganic carbon concentration was highest in summer and autumn (P < 0.05) although the proportion as free CO2 (pCO2) did not vary seasonally (P > 0.05). Over the 5 years, pCO2 was always supersaturated with respect to the atmosphere ranging from 374 to 3626 ppmv (1.0- to 10.1-fold greater than atmospheric
equilibrium), and CO2 evasion from the stream to the atmosphere ranged from 146 to 353 mmol m−2 d−1. Whereas pCO2 in surface water exhibited little intra-annual or interannual variation, distinct seasonal patterns in soil and bedrock pCO2 were revealed by the catchment CO2 model. Seasonally, soil pCO2 increased from a winter low of 8167 ppmv to a summer high of 27,068 ppmv. Driven by the seasonal variation in gas levels,
evasion of CO2 from soils to the atmosphere ranged from 83 mmol m−2 d−1 in winter to 287 mmol m−2 d−1 in summer. The seasonal variation in soil CO2 tracked soil temperature (r
2= 0.46, P < 0.001) and model-derived estimates of CO2 evasion rate from soils agreed with previously reported fluxes measured using chambers (Pearson correlation coefficient =
0.62, P < 0.05) supporting the model assumptions. Although rates of CO2 evasion were similar between the stream and soils, the overall rate of evasion from the channel was only 0.4% of the 70,752
mol/d that evaded from soils due to the vastly different areas of the two subsystems. Our model provides a means to assess
whole catchment CO2 dynamics from easily collected and measured stream-water samples and an approach to study catchment scale variation in soil
ecosystem respiration.
Received 24 July 1997; accepted 14 November 1997. 相似文献
999.
在温室条件下研究了水分亏缺对银合欢根瘤的水分关系、固氮酶活性(乙炔还原活性)、呼吸活性以及蔗糖代谢有关酶活性的影响。随着土壤含水量的下降,根瘤水势也相继下降。土壤干旱不但显著地抑制了根瘤乙炔还原的活性,而且对根瘤的呼吸活性、ATP的产生以及催化蔗糖降解的碱性转化酶和蔗糖合成酶的活性也具强烈的抑制作用。然而,根瘤可溶性总糖含量则不受土壤干旱的影响。用呼吸抑制剂DNP处理根瘤后,其固氮酶活性、呼吸活性及ATPI含量都受到极显著的抑制。这都表明,水分胁迫对根瘤呼吸活性及ATP产生的抑制可解释干旱条件下固氮酶活性的下降。 相似文献
1000.
Lactate, an important metabolic substrate for peripheral tissues and the liver, is released in significant amounts from adipose tissue. Using a perifusion system, we measured lactate production from glucose and response to insulin in isolated mesenteric and epididymal adipocytes removed from fed or fasted male Wistar rats at two stages of growth and development: (a) lean rats (7 weeks to 9 weeks old, weighing ~250 g), and (b) fatter rats (6 months to 8 months old, weighing ~550 g). The results show that lactate production in perifused adipocytes is regulated by the prior nutritional state of the animals, by the adipose tissue region, and by the presence of insulin in the perifusate. In fat cells from lean rats, basal lactate production was significantly higher (p<0.05) in mesenteric cells when compared with epididymal cells, both in the fed state (7.8 nmol/107 fat cells per minute vs. 2.9 nmol/107 fat cells per minute) and after 2 days of fasting (13.6 nmol vs. 3.5 nmol). When the response to 1 mU/mL insulin was studied, however, the relative increase in lactate production produced by insulin was greater in the epididymal cells than in the mesenteric cells, in both the fed (194% vs. 91% over basal, respectively) and fasted (360% vs. 55% over basal, p<0.05) state. When larger epididymal adipocytes from fatter rats were compared with an equal number of smaller epididymal cells from leaner rats, the larger cells produced 4.99 nmol of lactate/107 fat cells per minute, whereas the smaller cells produced 2.93 nmol (p=0.08). Large fat cells showed a small and nonsignificant response to insulin in either type of cell (epididymal vs. mesenteric) or nutritional state (fed vs. fasted). This study indicates that distinct regional differences exist in lactate production and response to insulin. Mesenteric adipose tissue, which drains directly into the portal vein and provides substrates to the liver, may be an important source of lactate for the hepatic processes of gluconeogenesis and glycogenesis. 相似文献