Pressure-induced unfolding and aggregation of the proteins in whey protein concentrate solutions     

Patel HA  Singh H  Havea P  Considine T  Creamer LK 《Journal of agricultural and food chemistry》2005,53(24):9590-9601

Whey protein concentrate solutions (12% w/v, pH 6.65 +/- 0.05) were pressure treated at 800 MPa for 20-120 min and then examined using size exclusion chromatography (SEC), small deformation rheology, transmission electron microscopy, and various types of one-dimensional (1D) and two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE). The pressure-treated samples showed a time-dependent loss of native whey proteins by SEC and 1D PAGE and a corresponding increase in non-native proteins and protein aggregates of different sizes. These aggregates altered the viscosity and opacity of the samples and were shown to be cross-linked by intermolecular disulfide bonds and by noncovalent interactions using 1D PAGE [alkaline (or native), sodium dodecyl sulfate (SDS), and SDS of reduced samples (SDS(R))] and 2D PAGE (native:SDS and SDS:SDS(R)). The sensitivity of the major whey proteins to pressure was in the order beta-lactoglobulin B (beta-LG B) > beta-LG A > bovine serum albumin (BSA) > alpha-lactalbumin (alpha-LA), and the large internal hydrophobic cavity of beta-LG may have been partially responsible for its sensitivity to high-pressure treatments. It seemed likely that, at 800 MPa, the formation of a beta-LG disulfide-bonded network preceded the formation of disulfide bonds between alpha-LA or BSA and beta-LG to form multiprotein aggregates, possibly because the disulfide bonds of alpha-LA and BSA are less exposed than those of beta-LG either during or after pressure treatment. It may be possible that intermolecular disulfide bond formation occurred at high pressure and that hydrophobic association became important after the high-pressure treatment.  相似文献   

Field parameterization of an empirical sheetwash transport equation     

Lawrence Band 《CATENA》1985,12(4):281-290

Specially designed instruments were used to sample surface water and sediment discharge on a set of small hillslopes. The data set produced is unique as it includes simultaneous observations of surface water and sediment discharge, local surface declivity and drainage area at several points over the slope surface, and the precipitation intensity taken a number of times through natural storm events. The data are used to parameterize an empirical sediment transport law, expressing sediment transport as a power function of the local declivity and surface water discharge. A good fit to the observed data is achieved, suggesting that these field techniques may be used to parameterize the equation for different soils. A dynamic catena effect involving surface grain size, local declivity and the form of the sediment transport equation is recognized that may have significant implications for the form of sediment transport and long-term hillslope development.  相似文献   

Identification of odorous gases originating from refuse waste     

Lawrence C. C. Koe  W. J. Ng 《Water, air, and soil pollution》1987,33(1-2):199-204

The complex mixture of gaseous compounds emitted from refuse wastes was scrubbed through an activated carbon column until odor breakthrough occurred. Refuse air samples were collected at the influent and effluent ports of the column for analysis on a gas chromatograph-mass spectrometer system. Sampling techniques involved the concentration of gaseous volatiles on Tenax GC adsorption tubes prior to thermal desorption onto a capillary fused-silica column for compound separation. Separated compounds were scanned by a quadrapole mass selective detector and compounds were matched against a library of mass spectra and available gas standards. Results indicated that the typical odorous gases emitted from refuse waste consisted mainly of carboxylic acids and some S compounds. Sensory tests revealed that a sweetish odor was associated with the carboxylic acids which eluted from the carbon column first.  相似文献   

Confirmation of some organonitrogen herbicides and fungicides by chemical derivatization and gas chromatography.   总被引：1，自引：0，他引：1  

J F Lawrence 《Journal of agricultural and food chemistry》1976,24(6):1236-1238

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Investigation of ovicell hyperplasia in bryozoans chronically exposed to natural oil seepage     

Dale Straughan  David M. Lawrence 《Water, air, and soil pollution》1975,5(1):39-45

Systemic collection and examination of bryozoans from surface, subsurface and benthic kelp fronds in an area chronically exposed to natural oil seepage revealed no instances of ovicell hyperplasia. Reasons are presented to explain the contrast between these findings and reported ovicell hyperplasia in other species exposed to creosote and petroleum hydrocarbons.  相似文献   

Impact of coal combustion waste on the microbiology of a model aquifer     

J. S. Brunning  D. E. Caldwell  J. R. Lawrence  R. D. Robarts 《Water, air, and soil pollution》1994,74(1-2):103-120

The effects of water infiltration into an alkaline coal combustion waste burial site on the chemical and microbiological aspects of a meso-scale (2.44 m diameter × 4.6 m, height, 65 tonne) model aquifer were analyzed. The spatial and temporal effects of the alkaline leachate on microbial activity, numbers and diversity were examined in the model and compared with uncontaminated control materials. Within the saturated zone below the waste there was a pH gradient from 12.4 at the water table, immediately below the waste, to 6.0 at 3.5 meters from the waste, and elevated levels of arsenic and strontium in the pore waters. Microtox testing of the contaminated pore waters indicated high toxicity (a gamma value of 1 at dilutions of 45 to 110 fold). The leachate contamination was associated with a reduction in bacterial [³H] leucine incorporation from a high of 267 fmol g^?1 h^?1 in sediments below the contaminant plume to undetectable in the contaminated zone. In comparison, leucine incorporation rates in control column sediments were 899 fmol g^?1 h^?1. Similar toxic effects were evident in reduced total direct and culturable counts of bacteria. Observations also indicated a reduction in microbial diversity and development of alkaline-tolerant microbial communities. These results indicated that any failure of confinement technologies at disposal sites would adversely affect both the chemistry and microbiology of the underlying saturated zone.  相似文献   

Response of two western Canadian conifers to simulated acidic precipitation     

Zoheir M. Abouguendia  Lawrence A. Baschak 《Water, air, and soil pollution》1987,33(1-2):15-22

Ready-to-plant nursery stock of jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) were subjected to simulated acid rains of pH 5.6 (control), 4.6, 3.6, and 2.6 under controlled growth room conditions to determine the threshold for damage. The two species exhibited contrasting response patterns to simulated acid rain treatments. Growth and chlorophyll content of jack pine were not adversely affected at any of the levels applied. Furthermore, no macroscopic foliar injury symptoms were evident and foliar nutrient levels remained unaffected. White spruce showed no statistically significant reduction in growth rate at any of the treatments. Needle chlorophyll a content of white spruce was not affected by any of the treatments, while chlorophyll b level was significantly reduced at pH 2.6. Symptoms of visible injury were observed to increase with rain acidity. No statistically significant change in the levels of foliar nutrients of white spruce were found, with the exception of the elevated S concentration at pH 2.6.  相似文献   

Patterns of diversity in fatty acid composition in the Australian groundnut germplasm collection     

B. D. Harch  K. E. Basford  I. H. DeLacy  P. K. Lawrence  A. Cruickshank 《Genetic Resources and Crop Evolution》1995,42(3):243-256

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THE USE OF OUTLINE MAPS ON HERBARIUM LABELS     

Abbe EC  Lawrence DB 《Science (New York, N.Y.)》1940,92(2382):181-182

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Ceramide triggers budding of exosome vesicles into multivesicular endosomes   总被引：5，自引：0，他引：5  

Trajkovic K  Hsu C  Chiantia S  Rajendran L  Wenzel D  Wieland F  Schwille P  Brügger B  Simons M 《Science (New York, N.Y.)》2008,319(5867):1244-1247

Intraluminal vesicles of multivesicular endosomes are either sorted for cargo degradation into lysosomes or secreted as exosomes into the extracellular milieu. The mechanisms underlying the sorting of membrane into the different populations of intraluminal vesicles are unknown. Here, we find that cargo is segregated into distinct subdomains on the endosomal membrane and that the transfer of exosome-associated domains into the lumen of the endosome did not depend on the function of the ESCRT (endosomal sorting complex required for transport) machinery, but required the sphingolipid ceramide. Purified exosomes were enriched in ceramide, and the release of exosomes was reduced after the inhibition of neutral sphingomyelinases. These results establish a pathway in intraendosomal membrane transport and exosome formation.  相似文献