Residual soluble proteins

It should be noted that not all the rubber proteins and non-rubbers can be removed by one centrifugation under the operating conditions employed at the latex concentrate plants. Residual soluble proteins and those associated with the latex particles are still present in HA latex concentrate (Table 4.3). Hence latex-dipped products such as medical gloves made from this latex would still contain water-extractable rubber proteins. The same applies to the latex obtained from purification by creaming (see Section 4.5.3). NR latex with very low water-extractable rubber proteins can be produced by further treatment to dislodge the proteins associated with latex particles. These are known as low protein or deproteinized NR latex and will be discussed further later. The concern over rubber proteins is that they can cause allergic reactions in certain individuals who are sensitized to them (see Section 4.5.6). 

FIGURE 9.31 The known proteoglycans include a variety of structures. The carbohydrate groups of proteoglycans are predominantly glycosaminoglycans O-linked to serine residues. Proteoglycans include both soluble proteins and integral transmembrane proteins. 

The conformation of bovine myelin basic protein (MBP) in AOT/isooctane/water reversed micellar systems was studied by Waks et al. 67). This MBP is an extrinsic water soluble protein which attains an extended conformation in aqueous solution 68 but is more density packed at the membrane surface. The solubilization of MBP in the AOT reversed micelles depends on the water/AOT-ratio w0 68). The maximum of solubilization was observed at a w0-value as low as 5.56. The same value was obtained for another major protein component of myelin, the Folch-Pi proteolipid 69). According to fluorescence emission spectra of MBP, accessibility of the single tryptophane residue seems to be decreased in AOT reversed micelles. From CD-spectra one can conclude that there is a higher conformational rigidity in reversed micelles and a more ordered aqueous environment. 

The number of sugar residues linked to the aglycone-pottion (1 1) or the hydroxylation of the aglycone markedly influences water and lipid solubility, protein... 

Water soluble protein with a relative molecular mass of ca. 32600, which particularly contains copper and zinc bound like chelate (ca. 4 gram atoms) and has superoxide-dismutase-activity. It is isolated from bovine liver or from hemolyzed, plasma free erythrocytes obtained from bovine blood. Purification by manyfold fractionated precipitation and solvolyse methods and definitive separation of the residual foreign proteins by denaturizing heating of the orgotein concentrate in buffer solution to ca. 65-70 C and gel filtration and/or dialysis. 

The yield and the composition of the fractions from soy bean meal obtmned with isolating WUS is shown in Table 1. The removal of cold water solubles, proteins and starch from soy meal was successful. The larger part of the material appeared in CWS, 59.1%. UFF contained mainly oligosaccharides and some water soluble proteins and UFR contained mainly water soluble proteins. The solution of SDSS and DTT extracted the residual proteins from the soy meal and the extract consisted for over 80% of proteins. Since the yield of the HWS fraction is only 0.4%, the composition is not discussed here. The remaining WUS contained 90% of NSP and the yield was 15.7%, which indicates that from the polysaccharides present in soy meal 92% was recovered in the WUS. By isolating WUS a fraction is obtained in which almost all cell wall polysaccharides are recovered and which contained only little other components. 

A bacterial phosphatidylinositol specific phospholipase C (PI-PLC) had been available for many years before it was demonstrated to strip a number of membrane-bound proteins from eukaryotic cell surfaces [1], Such proteins are anchored by a PI moiety in which the 6 position of inositol is glycosidically linked to glucosamine, which in turn is bonded to a polymannan backbone (Fig. 3-10). The polysaccharide chain is joined to the carboxyl terminal of the anchored protein via amide linkage to ethanolamine phosphate. The presence of a free NH2 group in the glucosamine residue makes the structure labile to nitrous acid. Bacterial PI-PLC hydrolyzes the bond between DAG and phosphati-dylinositols, releasing the water-soluble protein polysac charide-inositol phosphate moiety. These proteins are tethered by glycosylphosphatidylinositol (GPI) anchors. 

Analyses of soluble proteins from complete genomes of 20 thermophilic or mesophilic microorganisms revealed that higher amounts of Glu and Asp residues and lower amounts of Gin and Asn residues are present in proteins of thermophiles compared to proteins of mesophiles. " This result suggests that Gin and Asn residues destabilize protein structure at high temperature, possibly through their deamidation. 

A hydrophobic amino acid will most likely be found in the hydrophobic core—a hydrophilic residue will (at least for water soluble proteins) most likely be located on the surface. 

Extraction of nitrofuran antibacterials from edible animal products should render the bound residues soluble, remove most if not all of tire proteins, and provide high yields for ah analytes. Sample extraction/deproteinization is usually accomplished with organic solvents capable to free the noncovalently bound residues from the endogenous macromolecules. Organic solvents including acetoni-... 

Extraction of sulfonamides and diaminopyrimidine potentiators from edible animal products should render the bound residues soluble, remove most or all of the proteins, and provide high yields for all analytes. Sample extraction/deprotei-nization is traditionally accomplished with polar solvents including acidic aqueous solutions (211,214-222), acetonitrile (56,223-232), chloroform (233-240), ethyl acetate (29,241-244), dichloromethane (204,242,245-247), acetone (194, 248, 249), or various combinations of them. Use of dichloromethane at pH 10 in the presence of an ion-pairing reagent (tetrabutylammonium) has also been reported to work extremely well in the extraction of sulfadimethoxine and ormeto-prim residues from catfish muscle (250) and animal tissues (251). Anhydrous sodium sulfate may be added to dehydrate tissue samples to permit better exposure of the matrix to tire solvent. 

A variation on the basic theme of receptor Tyr kinases is seen in receptors that have no intrinsic protein kinase activity but, when occupied by their ligand, bind a soluble Tyr kinase. One example is the system that regulates the formation of erythrocytes in mammals. The cytokine (developmental signal) for this system is erythropoietin (EPO), a 165 amino acid protein produced in the kidneys. When EPO binds to its plasma membrane receptor (Fig. 12-9), the receptor dimerizes and can now bind the soluble protein kinase JAK (Janus kinase). This binding activates JAK, which phosphory-lates several Tyr residues in the cytoplasmic domain of the EPO receptor. A family of transcription factors, collectively called STATs (signal transducers and activators of transcription), are also targets of the JAK kinase activity. An SH2 domain in STATS binds (P)-Tyr residues in the EPO receptor, positioning it for this phosphorylation by JAK. When STATS is phosphorylated in re-... 

In some cases, the domain-binding partner is internal. Phosphorylation of some protein kinases inhibits their activity by favoring the interaction of an SH2 domain with a (P)-Tyr in another domain of the same enzyme. For example, the soluble protein Tyr kinase Src, when phosphorylated on a critical Tyr residue, is rendered inactive as an SH2 domain needed to bind to the substrate protein instead binds to an internal (P)-Tyr... 

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