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161.
G. Niethammer H. E. Wolters Klaus Witt Frank Hampel Paul Ruthke Margrit Frantzen H. Dathe W. Grummt Johannes Kummer Claus König und Gerd Bohlken 《Journal of Ornithology》1964,105(2):197-202
Ohne Zusammenfassung 相似文献
162.
Carlos I?iguez–Armijos Adrián Leiva Hans–Georg Frede Henrietta Hampel Lutz Breuer 《PloS one》2014,9(8)
Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. This research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments. 相似文献
163.
Prager K Wang-Eckhardt L Fluhrer R Killick R Barth E Hampel H Haass C Walter J 《The Journal of biological chemistry》2007,282(19):14083-14093
164.
The reaction of the racemic chiral methyl complex (η5-C5H5)Re(NO)(PPh3)(CH3) (1) with CF3SO3H and then NH2CH2C6H5 gives [(η5-C5H5)Re(NO)(PPh3)(NH2CH2C6H5)]+ ([4a-H]+; 73%), and deprotonation with t-BuOK affords the amido complex (η5-C5H5)Re(NO)(PPh3)(NHCH2C6H5) (76%). Reactions of 1 with Ph3C+ X− and then primary or secondary amines give [(η5-C5H5)Re(NO)(PPh3)(CH2NHRR′)]+ X− ([6-H]+ X−; R/R′/X = a, H/NH2CH2C6H5/BF4; a′, H/NH2CH2C6H5/PF6; b, H/NH2CH2(CH2)2CH3/PF6; c, H/(S)-NH2CH(CH3)C6H5/BF4); d, CH2CH3/CH2CH3/PF6; e, CH2(CH2)2CH3/CH2(CH2)2CH3/PF6; f, CH2C6H5/CH2C6H5/PF6; g, -CH2(CH2)2CH2-/PF6; h, -CH2(CH2)3CH2-/PF6; i, CH3/CH2CH2OH/PF6 (62-99%). Deprotonations with t-BuOK afford the amines (η5-C5H5)Re(NO)(PPh3)(CH2NRR′) (6a-i; 99-40%), which are more stable and isolated in analytically pure form when R ≠ H. Enantiopure 1 is used to prepare (RReSC)-[6c-H]+, (RReSC)-6c, (S)-[6g-H]+, and (S)-6g. The crystal structures of [4a-H]+, a previously prepared NH2CH2Si(CH3)3 analog, [6a′,d,f,h-H]+, (RReSC)-6c, and 6f are determined and analyzed in detail, particularly with respect to cation/anion hydrogen bonding and conformation. In contrast to analogous rhenium containing phosphines, 6a-i show poor activities in reactions that are catalyzed by organic amines. 相似文献
165.
The Chinese hamster ovary (CHO) cell culture temperature-sensitive mutant ts025Cl with a defect in leucyl-tRNA synthetase (LeuRS) does not have an inherently more thermolabile LeuRS, but instead the mutation causes the complete loss of the LeuRS high molecular weight complexes which are present in normal wild-type cells. The mutant cell LeuRS has a single 8 S enzyme form which corresponds hydrodynamically to the 8 S free form of wild-type enzyme. Both 8 S forms have the same thermostability and the same K
m
for leucine, indicating that there is no inherent defect in the catalytic activity of the enzyme. The temperature-sensitive phenotype can be explained by the lack of thermostable high molecular weight forms of LeuRS.This work was supported by NIH Grant GM 19506 to A.E.H. and GM 20737 to D.E.O. 相似文献
166.
Arnold Hampel K.V. Prahlad S.T. Brei Bruce Ruefer Chris Mlot 《Developmental biology》1975,44(1):169-177
All amino acids and several nucleic acid precursors are taken up by Xenopus laevis embryos. The embryos are completely intact and not modified in any way. These precursors are directly incorporated into the macromolecules of Xenopus embryos and not prokaryotic contaminants as has been previously claimed. Radioactive leucine is incorporated into Xenopus laevis ribosomal proteins as characterized by sucrose gradient centrifugation. The uptake of the amino acids is cycloheximide sensitive and unaffected by chloramphenicol. Radioactive adenosine and orotic acid are taken up and incorporated into tRNA and rRNA at high levels as characterized by sucrose gradients and electrophoresis. These characterizations of labeled macromolecules unequivocally show that normal Xenopus laevis embryos will take up and incorporate labeled precursors to levels which are sufficient to study cellular biochemical events at such early stages of development. 相似文献
167.
The kinetics of the release of chitinolytic activity (endochitinase EC 3.2.1.14, \-N-acetyglucosaminidase EC 3.2.1.30) by a yeast cell wall lytic Arthrobacter species was studied. The organism was cultivated on yeast cell wall, mycelium of Trichoderma reesei, colloidal chitin, N-acetylglucosamine, glucosamine and mixtures with acetate. With the exception of yeast cell wall, these substrates were used as the sole source of carbon and nitrogen. The growth on colloidal chitin (0.5%) proceeded at a maximum specific growth rate (umax) of 0.23 h–1 and yielded 2700 mU1–1 chitinase. Yeast cell wall and mycelium of T. reesei supported more rapid growth (max = 0.30 h–1 and 0.25 h–1 respectively) but yielded reduced chitinase activity (565 mUl–1 and 700 mUl–1). The growth rate on glucosamine (max = 0.24 h–1) was reduced when this was mixed with acetate (max = 0.12 h–1), whereas the enzyme yield was increased from 720 mUl–1 to 960 mUl–1. The same effect on growth rate was observed with glucose and equimolar mixtures of glucose and acetate, indicating a strong impact of the organic acid on carbohydrate transport or metabolism. The growth of adapted cells on N-acetylglucosamine was comparable to that observed on an equimolar mixture of glucosamine and acetate, indicating that N-acetylglucosamine is rapidly hydrolysed by adapted cells. 相似文献
168.
Bacterial cell surface layers (S-layers) which show a crystalline structure, defined pores, and a regular arrangement of functioal groups can be used for production of isoporous ultrafiltration membranes and as a matrix for immobilization of macromolecules. S-layer-carrying cell wall fragments from thermophilic Bacillaceae possess an extremely thin peptidoglycan-containing layer with pores larger than those in the S-layer lattice. Thus, they can directly be used for biotechnological applications, when an S-layer protein pool is stored in the rigid cell wall layer which is released during cell wall preparation, forming an inner S-layer. In the present study, a synthetic medium for Bacillus stearothermophilus PV 72 was developed by applying the pulse and shift technique with the aim to produce cell wall fragments with before-mentioned properties by varying the growth conditions in condtinuous culture. The organism was grown at 57 degrees C in a bioreactor with 1 L working volume equipped with exhaust gas analysis and connected to a PC-based process control system. Biomass concentration was 2.2 g/L out of 8 g/L glucose at a dilution rate of 0.3 h(-1), giving a biomass productivity of 0.66 g/L h. Although the organism was grown under different conditions, no change in peptidoglycan composition, extent of peptidoglycan crosslinking, and content of secondary cell wall polymers was observed. The amount of S-layer protein pool stored in the rigid cell wall layer and the autolytic activity depended mainly on the specific growth rate. Cell wall fragments with properties required for ultrafiltration membrane production could be produced by parameter settings in continuous culture. (c) 1995 John Wiley & Sons, Inc. 相似文献
169.
The kinetics of \-1,3-glucanase (EC 3.2.1.39; 1,3-\-d-glucan-glucano-hydrolase) formation by a yeast cell wall lytic Arthrobacter species was studied. Yeast glucan as a substrate yielded 360 units (U)/l, but it appeared to be unsuitable for fermentation purposes because of its insolubility and its residual content of glycogen. Growth on water-soluble \(1,3)-glucan [maximum specific growth rate (µmax)=0.19 h–1] was governed by different saccharides liberated by enzyme action on glucan. Enzyme formation was repressed by glucose and derepressed by its restricted availability during late exponential and stationary growth. At least 380 U/l of \(1,3)-glucanase were formed. Lactose and lactulose were detected as precursors of potent inducers for \(1,3)-glucanase, the first being a cheap and easily available substrate for large-scale cultivations. Growth rates were reduced (µmax=0.18 h–1 and µmax=0.13 h–1, respectively), enzyme synthesis occurred only during post-logarithmic growth. The \(1,3)-glucanase levels (260 U/l) formed were comparable to that attained with glucan as a substrate. In continuous culture no enzyme was formed under steady-state conditions but it occurred during transient states after shifting the dilution rate to lower values.
Correspondence to: W. Hampel 相似文献
170.
The kinetics of amylolytic enzyme formation by a yeast cell wall lytic Arthrobacter species were studied. Cultivation on autoclaved cells of baker's yeast showed that amylase formation was closely related to trehalose and glycogen dissimilation. Growth on yeast glycogen (0.5%) proceeded quite rapidly ( = 0.31 h–1) with extensive amylase formation during exponential cell multiplication and a further low increase in activity during the stationary phase. Beside amylolytic activity [450 units (U) l–1] the formation of a relatively high level of -glucosidase (90 U l–1) was detected, the latter almost exclusively bound to bacterial cells. Growth on 0.5% trehalose occurred at a reduced rate ( = 0.22 h–1) with post-logarithmic enzyme synthesis in the stationary phase. Amylase activity attained a level of 1200 U l–1, whereas -glucosidase was very low at 7.7 U l–1. Continuous culture experiments in the chemostat showed maximal volumetric productivity of amylase (105 U l–1 h–1) at a dilution rate of 0.15 h–1. Growth on various carbohydrates revealed low levels of amylolytic activity (<100 U l–1), which were increased by a -1,4-glucans and oligosaccharides such as starch, dextrin, maltotriose and maltose. On 0.5% maltose, growth-associated enzyme synthesis (230 U l–1) was detected at a reduced growth rate ( = 0.14 h–1). Amylolytic enzyme preparations from the culture fluid showed an unusual cleavage pattern; acting on starch, the polymer was almost completely hydrolysed to maltotriose and maltose in a molar ratio of 3:1.Correspondence to: W. A. Hampel 相似文献