1,720,965 research outputs found
Thresholds, long delays and stability from generalized allosteric effect in protein networks
No full textEgg-matrix for large-scale single-step affinity purification of plant lectins with different carbohydrate specificities
No full textHen eggs represent an easily available and inexpensive source of glycoproteins expressing a variety of sugars. Egg glycoproteins
might therefore be exploited to purify by affinity chromatography carbohydrate-binding proteins (lectins) with different specificities.
A method to generate an affinity matrix from hen eggs is described. The matrix was assayed for its ability to purify in a single step
biologically active phytohemagglutinin, wheat germ agglutinin, lentil lectin, and peanut agglutinin. Milligrams of purified lectins per
gram of matrix was obtained, with the only exception of peanut agglutinin that was not efficiently retained into the affinity column.
Hen egg chromatography is a relatively simple, fast, and reproducible method to purify high amount of plant lectins
Temperature-dependent decay of wheat germ agglutinin activity and its implications for food processing and analysis
No full textA recently-described immunoenzymatic (ELISA) method for the quantitative determination of biologically-active wheat germ
agglutinin (WGA) in unknown samples has been applied to measure the concentration of active WGA in raw and cooked wheatderived
foodstuffs. The method exploits the binding specificity of WGA to ovalbumin as a first step followed by identification of
bound lectin with polyclonal antibodies. Purified WGA was used to obtain calibration curves. Detectable amounts of WGA were
found in raw foodstuffs and wheat flours, whilst variable amounts of agglutinin were found in wholemeal pasta probably as a
consequence of thermal inactivation during food processing. The thermal gradient gel electrophoresis (TGGE) technique was
therefore applied to analyse the thermal stability of WGA. The biological activity of WGA decreased as a function of heating
temperatures and time of exposure to thermal treatment in an S-shaped fashion with an inflection point around 65 C. As a
consequence, WGA might represent a biochemical ‘‘indicator’’ allowing one to determine the thermal treatment undergone by
wheat-derived foods during processing
Ab initio phenomenological simulation of the growth of large tumor cell population.
No full textIn a previous paper we have introduced a phenomenological model of cell metabolism and of the cell cycle to simulate the behavior of large tumor cell populations (Chignola and Milotti 2005 Phys. Biol. 2 8). Here we describe a refined and extended version of the model that includes some of the complex interactions between cells and their surrounding environment. The present version takes into consideration several additional energy-consuming biochemical pathways such as protein and DNA synthesis, the tuning of extracellular pH and of the cell membrane potential. The control of the cell cycle, which was previously modeled by means of ad hoc thresholds, has been directly addressed here by considering checkpoints from proteins that act as targets for phosphorylation on multiple sites. As simulated cells grow, they can now modify the chemical composition of the surrounding environment which in turn acts as a feedback mechanism to tune cell metabolism and hence cell proliferation: in this w
Development of a new procedure for protein recovery and quantification in wine
No full textIn order to develop a procedure for protein recovery and quantification in wines, known amounts of bovine serum albumin (BSA) were added to samples of protein-free wine. Dialysis followed by lyophilization, precipitations with ethanol, acetone, trichloroacetic acid, and by a new method that precipitates proteins as protein- potassium dodecyl sulfate complexes (KDS method) were used to recover BSA from protein-free wine. Recovered BSA was then quantified by three colorimetric assays: Bradford, Lowry, and Smith. The KDS method followed by the Smith assay obtained the best match between actual and measured BSA quantities. When this procedure was used for quantification of wine proteins, the results were in accordance to those determined by densitometric quantification of the protein bands separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), indicating that the proposed method allows a reliable determination of the protein content of wine
Studies on the joint cytotoxicity of Wheat Germ Agglutinin and monensin
No full textWheat Germ Agglutinin (WGA) cytotoxicity has been studied using two human leukemia cell lines, Molt3 and K562, and human
peripheral blood mononuclear cells (PBMC). In spite of similar binding at the cell surface, WGA was found to promote cell death to
a different extent in Molt3, K562 and PBMC and to induce different death events leading to apoptosis in Molt3 and either apoptosis
and necrosis in K562 cells and PBMC. In Molt3 but not in K562 cells, WGA cytotoxicity could be potentiated 66–200 fold by 50 nM
monensin, a carboxylic ionophore that perturbs the intracellular trafficking of endocytosed molecules. Synergism between the
cytotoxic activities of WGA and monensin was demonstrated in Molt3 cells by comparing non toxic, or slightly toxic, doses of
WGA and monensin alone or in combination.
These results show that the cytotoxic effect of WGA is dependent on internalisation events which may differ among the cell lines
used. WGA and monensin can enter the human diet being a component of wheat germ and an antibiotic used for zootechnic reasons
in the bioindustry, respectively. These data reveal the synergistic effect between two dietary molecules, otherwise per se toxic at much
higher concentrations, with possible implications for human and animal health
Isolation and Identification of Two Lipid Transfer Proteins in Pomegranate (Punica granatum)
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