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71.
A. van?Reenen F. Gutiérrez-Mejía L.J. van?IJzendoorn M.W.J. Prins 《Biophysical journal》2013,104(5):1073-1080
We report a method to profile the torsional spring properties of proteins as a function of the angle of rotation. The torque is applied by superparamagnetic particles and has been calibrated while taking account of the magnetization dynamics of the particles. We record and compare the torsional profiles of single Protein G-Immunoglobulin G (IgG) and IgG-IgG complexes, sandwiched between a substrate and a superparamagnetic particle, for torques in the range between 0.5 × 103 and 5 × 103 pN·nm. Both molecular systems show torsional stiffening for increasing rotation angle, but the elastic and inelastic torsion stiffnesses are remarkably different. We interpret the results in terms of the structural properties of the molecules. The torsion profiling technique opens new dimensions for research on biomolecular characterization and for research on bio-nanomechanical structure-function relationships. 相似文献
72.
Rembrandt Dijkerman Jeroen Ledeboer Huub J.M. Op den Camp Rudolf A. Prins Chris van der Drift 《Current microbiology》1997,34(2):91-96
The anaerobic fungus Neocallimastix sp. strain L2,
isolated from the feces of a llama, was tested for growth on a range of
soluble and insoluble carbohydrate substrates. The fungus was able to ferment
glucose, cellobiose, fructose, lactose, maltose, sucrose, soluble starch,
inulin, filter paper cellulose, and Avicel. No growth was observed on
arabinose, galactose, mannose, ribose, xylose, sorbitol, pectin, xylan,
glycerol, citrate, soya, and wheat bran. The fermentation products after
growth were hydrogen, formate, acetate, ethanol, and lactate. The
fermentation pattern was dependent on the carbon source. In general, higher
hydrogen production resulted in decreased formation of lactate and ethanol.
Recovery of the fermented carbon in products at the end of growth ranged from
50% to 80%. (Hemi)cellulolytic enzyme activities were affected
by the carbon source. Highest activities were found in filtrates from
cultures grown on cellulose. Growing the fungus on inulin and lactose yielded
the lowest cellulolytic activities. Highest specific activities for
avicelase, endoglucanase, β-glucosidase, and xylanase were obtained with
Avicel as the substrate for growth (0.29, 5.9, 0.57, and 13
IU · mg−1 protein, respectively). Endoglucanase activity
banding patterns after SDS-PAGE were very similar for all substrates. Minor
differences indicated that enzyme activities may in part be the result of
secretion of different sets of isoenzymes.
Received: 10 July 1996 / Accepted: 22 July 1996 相似文献
73.
Interrelations between sulfate-reducing and methane-producing bacteria in bottom deposits of a fresh-water lake. III. Experiments with 14C-labeled substrates 总被引:31,自引:0,他引:31
An ecological substrate relationship between sulfate-reducing and methane-producing bacteria in mud of Lake Vechten has been studied in experiments using 14C-labeled acetate and lactate as substrates. Fluoroacetate strongly inhibited the formation of 14CO2 from [U-14C]-acetate and β-fluorolactate gave an inhibition of similar magnitude of the breakdown of [U-14C]-l-lactate to 14CO2 thus confirming earlier results on the specific action of these inhibitors. The turnover-rate constant of l-lactate was 2.37 hr-1 and the average l-lactate pool size was 12.2 μg per gram of wet mud, giving a turnover rate of 28.9 μg of lactate/gram of mud per hr. The turnover-rate constant of acetate was 0.35 hr-1 and the average pool size was 5.7 μg per gram of wet mud, giving a rate of disappearance of 1.99 μg of acetate/gram of mud per hr. Estimations of the acetate turnover rate based upon the formation of 14CO2 from [U-14C]-acetate or [1-14C]-acetate yielded figures of the same magnitude (range 0.45 to 1.74). These and other results suggest that only a portion of the lactate dissimilated is turned over through the acetate pool. The ratio of 14CO2/14CH4 produced from [U-14C]-acetate by mud was 1.32; indicating that 0.862 moles of CH4 and 1.138 moles of CO2 are formed per mole of acetate. From the rate of disappearance of acetate (0.027 μmoles/gram wet mud per hr) and the rate of methane production (0.034 μmoles/gram wet mud per hr), it may be concluded that acetate is an important precursor of methanogenesis in mud (approximately 70%). A substrate relationship between the two groups of bacteria is likely since 14CH4 was formed from [U-14C]-l-lactate. 相似文献
74.
Isolation, Culture, and Fermentation Characteristics of Selenomonas ruminantium var. bryanti var. n. from the Rumen of Sheep 下载免费PDF全文
R. A. Prins 《Journal of bacteriology》1971,105(3):820-825
Large forms of Selenomonas sp. were isolated from the sheep rumen on a rumen fluid-glucose-agar medium by using a differential centrifugation technique to purify the inoculum. The cells from the six isolated strains were curved, gram-negative, strictly anaerobic crescents, and rapidly motile by flagella attached to the concave side of the cell. One or more of the volatile fatty acids were essential for growth. None of the strains produced indole or reduced nitrate. All strains grew on fructose, glucose, mannose, cellobiose, maltose, sucrose, and salicin. Fermentation end products from glucose were mainly lactate, acetate, propionate, and formate. Small amounts of succinate were formed. The final pH in a glucose medium ranged between 4.3 and 4.5. On the basis of the sugar fermentation characteristics and the capacity to form hydrogen sulfide from cysteine, it is suggested that one of the strains is a large form of Selenomonas ruminantium. The other five strains are designated S. ruminantium var. bryanti, var. n. 相似文献
75.
76.
Resource partitioning between sympatric wild and domestic herbivores in the Tarangire region of Tanzania 总被引:6,自引:1,他引:5
The effect of the introduction of an exotic species (cattle) into a native African herbivore assemblage was investigated
by studying resource partitioning between zebu cattle, wildebeest and zebra. Resource partitioning was investigated by analysing
grass sward characteristics (such as sward height and percentage nitrogen in leaves) of feeding sites selected by the different
herbivore species. Linear discriminant analysis was used to determine whether a distinction could be made between feeding
sites selected by the different animal species or whether the animal species showed overlap in resource use by selecting similar
feeding sites. Wildebeest and zebra did not show overlap in resource use except in the wet season when resources were ample.
Cattle showed overlap in resource use with zebra in the early wet season and with wildebeest in the early dry season, seasons
when food limitation is likely. In the wet season, cattle showed overlap in resource use with both zebra and wildebeest.
Implications of these results for competitive relationships between livestock and wildlife are discussed. We suggest that
interpretation of overlap in resource use may be different for an assemblage of long-term coexisting native species as compared
to an assemblage of native and exotic species. Among native herbivores, overlap in resource use is not expected based on evolutionary
segregation. In a native assemblage to which an exotic species has been introduced, however, overlap in resource use can occur
under food-limited conditions and consequently implies competition.
Received: 1 September 1998 / Accepted: 20 April 1999 相似文献
77.
P S Dragovich S E Webber T J Prins R Zhou J T Marakovits J G Tikhe S A Fuhrman A K Patick D A Matthews C E Ford E L Brown S L Binford J W Meador R A Ferre S T Worland 《Bioorganic & medicinal chemistry letters》1999,9(15):2189-2194
Tripeptide-derived molecules incorporating N-methyl amino acid residues and C-terminal Michael acceptor moieties were evaluated as irreversible inhibitors of the cysteine-containing human rhinovirus 3C protease (3CP). Such compounds displayed good 3CP inhibition activity (k(obs)/[I] up to 610,000 M(-1) s(-1)) and potent in vitro antiviral properties (EC50 approaching 0.03 microM) when tested against HRV serotype-14. 相似文献
78.
Jelle G. Ferwerda Sipke E. van. Wieren Andrew K. Skidmore Herbert H. T. Prins 《Plant and Soil》2005,273(1-2):203-209
The effects of available soil N and P and the effect of simulated browsing (leave removal) on foliar condensed tannin (CT) concentration were tested on young Colophospermum mopane (J. Kirk ex Benth) J. Leonard (Mopane) plants. Although clear differences in growth occurred between different levels of soil N, no differences in foliar CT concentration were found. Changes in available soil P and physical damage did not affect the plant growth or chemical composition. The complete absence of response of CT concentration to physical damage and soil nutrients may be related to the age of the trees in this study. It is proposed that existing theories on the interaction between soil properties and carbon based defences in trees are expanded, to include the potential responses of young trees to different soil nutrient levels. 相似文献
79.
Moldenhauer J Pretorius ZA Moerschbacher BM Prins R Van Der Westhuizen AJ 《Molecular Plant Pathology》2008,9(2):137-145
Stripe rust, caused by Puccinia striiformis f. sp. tritici , is a serious disease of wheat. The spring wheat cultivar Kariega expresses complete adult plant resistance to stripe rust, whereas Avocet S is susceptible. In former studies, quantitative trait loci (QTL) analysis of doubled haploid lines derived from a Kariega × Avocet S cross revealed two major QTL ( QYr.sgi-7D and QYr.sgi-2B.1 ) and two minor QTL ( QYr.sgi-1A and QYr.sgi-4A.1 ) responsible for the adult resistance of Kariega in the field. Avocet S contains none of these QTL. In the present study, stripe rust development was compared, by means of fluorescence and confocal laser scanning microscopy, in flag leaves of Kariega, Avocet S and six doubled haploid (DH) lines, containing all four, none or one QTL. Depending on the QTL present, the infection types of the DH lines ranged from resistant to fully susceptible. No differences in fungal growth were observed during the first 5 days post inoculation (dpi), whereas the mean length of the fungal colonies started to differ at 6 dpi. Interestingly, MP 51 carrying QYr.sgi-7D responded with lignification to the fungal growth without restricting it, whereas MP 35 containing QYr.sgi-2B.1 did not show lignified host tissue, but fungal growth was restricted. RT PCR experiments with sequences of pathogenesis-related (PR) proteins resulted in a slightly stronger induction of PR 1, 2 and 5, known markers for the hypersensitive reaction, and peroxidases in MP 51, whereas a second band for chitinases was detected in MP 35 only. 相似文献
80.
Strategies for antiviral resistance in transgenic plants 总被引:3,自引:0,他引:3
Prins M Laimer M Noris E Schubert J Wassenegger M Tepfer M 《Molecular Plant Pathology》2008,9(1):73-83
Genetic engineering offers a means of incorporating new virus resistance traits into existing desirable plant cultivars. The initial attempts to create transgenes conferring virus resistance were based on the pathogen-derived resistance concept. The expression of the viral coat protein gene in transgenic plants was shown to induce protective effects similar to classical cross protection, and was therefore distinguished as 'coat-protein-mediated' protection. Since then, a large variety of viral sequences encoding structural and non-structural proteins were shown to confer resistance. Subsequently, non-coding viral RNA was shown to be a potential trigger for virus resistance in transgenic plants, which led to the discovery of a novel innate resistance in plants, RNA silencing. Apart from the majority of pathogen-derived resistance strategies, alternative strategies involving virus-specific antibodies have been successfully applied. In a separate section, efforts to combat viroids in transgenic plants are highlighted. In a final summarizing section, the potential risks involved in the introduction of transgenic crops and the specifics of the approaches used will be discussed. 相似文献