HA protein

Biosorption is a rather complex process affected by several factors that include different binding mechanisms (Figure 10.4). Most of the functional groups responsible for metal binding are found in cell walls and include carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine, and imidazol moieties.4 90 The cell wall of plant biomass has proteins, lipids, carbohydrate polymers (cellulose, xylane, mannan, etc.), and inorganic ions of Ca(II), Mg(II), and so on. The carboxylic and phosphate groups in the cell wall are the main acidic functional groups that affect directly the adsorption capacity of the biomass.101... 

Only proteins that contain proline bind polyphenols. Asano et al. (1982) demonstrated that the haze-forming activity of a protein is roughly proportional to the mole percentage of proline it contains (see Fig. 2.3). DNA has codes for exactly 20 amino acids. If each of these were equally present in a protein, there would be 5 mol% of each one. In fact, most proteins have much less proline than this. There are a few exceptions. Casein has about 8 mol% proline and the grain prolamins (proline-rich, alcohol-soluble proteins) are even higher. Hordein, the barley prolamin, contains about 20 mol% proline. As a result, it readily forms haze with polyphenols and is the main beer haze-active (HA) protein. Hordein contains even more glutamine (Q) than proline (P), and often these amino acids are adjacent in the protein (see Fig. 2.4). In fact, the sequence P-Q-Q-P occurs... 

A response surface model of the effects of HA protein concentration (gliadin, the wheat prolamin), HA polyphenol concentration (tannic acid, TA), alcohol, and pH on the amount of haze formed was constructed using a buffer model system (Siebert et al., 1996a). Figure 2.12 shows the effects of protein and polyphenol on haze predicted by the model at fixed levels of pH and alcohol. The model indicates that as protein increases at fixed polyphenol levels, the haze rises to a point and then starts to decline. Similarly, when polyphenol increases at a fixed protein level, the haze increases to a maximum and then declines. 

A conceptual model that accounted for this behavior was proposed (see Fig. 2.13) (Siebert et al., 1996c). It is assumed that there are a fixed number of polyphenol-binding sites in an HA protein, presumably related to the proline content, and an FLA polyphenol molecule can attach to at the most two proteins (this is likely for steric reasons, even if a... 

FIGURE 2.12 Response surface model predictions of the effects of HA protein (gliadin) and HA polyphenol (TA) on the haze intensity in a model system at fixed levels of pH and alcohol. Reprinted with permission from Siebert et at. (1996a). Copyright 1996 American Chemical Society. 

In general, beer tends to be rich in HA protein and poor in HA polyphenol, while apple juice tends to have the opposite pattern (Siebert et al., 1996a). Grape juice is fairly low in HA protein and variable in HA polyphenol. 

White wines were uniformly low in HA protein, while red wines were quite variable (Siebert et al., 1996b). Vitis vinifera white wines had very low levels of HA polyphenols, while Vitis labrusca white wines had higher and vinifera-labrusca hybrids had intermediate levels (Siebert et al., 1996b). All red wines had high levels of HA polyphenols, and most had low levels of HA protein the two exceptions were both hybrids. 

A number of approaches have been used to determine the amount of HA protein in a sample. The most successful of these is based on adding a fixed amount of TA to a sample (Thompson and Forward, 1969) after incubation, the turbidity is measured and the increase in turbidity observed is presumed to be proportional to the amount of HA protein in the sample. This method has the advantage that only substances able to form haze with polyphenols respond. The saturated ammonium sulfate precipitation limit (SAPL) method has also been widely used, but is far inferior in providing useful information (Berg et al., 2007 Siebert et al., 2005). 

Adsorbents that remove proteins or polyphenols are used to treat a number of beverages to delay the onset of haze formation. Protein adsorbents include bentonite and silica. Bentonite removes protein nonspecifically (see Fig. 2.19) and so is unsuitable for stabilizing beverages where foam is desirable (beer and champagne). Silica, on the other hand, has remarkable specificity for HA proteins while virtually sparing foam-active proteins in beer (Siebert and Lynn, 1997b) (see Fig. 2.20). Silica removes approximately 80% of the HA protein from unstabilized beer, while leaving foam-active protein nearly untouched at commercial treatment levels. 

This was shown to occur because silica binds to the same features in polypeptides that polyphenols do (peptidically linked proline Siebert and Lynn, 1997b) (see the concept in Fig. 2.21). In contrast, in unstabilized apple juice, silica removes only on the order of 20% of the HA protein... 

FIGURE 2.19 The effects on foam active ( ) and HA ( ) protein of treating unstabilized beer with bentonite. Reprinted with permission from Siebert and Lynn (1997b). Copyright 1997 American Society of Brewing Chemists. 

As a result, it appears likely that PVPP binds to polyphenols in a similar manner to that of HA proteins. As with gliadin-TA binding,... 

S-pBlmrtovI (S-Acy11 tieterotrimeric G-proteins a-sjbunit), G-protein-coupled receptors, see chapter 5 Has proteins, see chapter 8 internal, no distinct consensus sequence... 

The ATM protein has been identified as an important member of a reaction chain that leads from detection of DNA damage to activation of the p53 protein. Mutations of the ATM protein are causally associated with the disease ataxia telangiectasia, thus the name ATM (ataxia telangiectasia mutated). The ATM protein has protein kinase activity and is counted as a member of the PI3-kinase family, due to sequence homologies (review Canman et al., 1998). The p53 protein is phosphorylated at Serl5 by ATM kinase (Canman et al., 1998) and it is assumed that this phosphorylation contributes to activation of the p53 protein. The ATM protein is preceded by other protein kinases that are directly or indirectly activated by DNA damage and pass this signal on to the p53 protein via the ATM protein. 

The influenza virus is surrounded by a membrane containing, among other proteins, many molecules of the hemagglutination (HA) protein (named for its abil-... 

FIGURE 11-24 Fusion induced by the hemagglutinin (FIA) protein during viral infection. HA protein is exposed on the membrane surface of the influenza virus. When the virus moves from the neutral pH of the interstitial fluid to the low-pH compartment (endosome) in the host cell, HA undergoes dramatic shape changes that mediate fusion of the viral and endosomal membranes, releasing the viral contents into the cytoplasm. 

Molecular structure must be implicated as odorants bind specifically with the sensory receptors called odorant receptors (ORs). The olfactory mucus has proteins called odorant binding proteins (OBPs) that dissolve the odorant molecule in the aqueous/lipid interface of the mucus. The OBPs act as binder molecules to assist the transfer of odorant to the receptor and increase its relative concentration in the mucus relative to inhaled air. They also function to remove used odorants for breakdown and free up the receptor to detect other molecules. 

Drosophila preproFMRFamide resembles many other neuropeptide precursors in that it contains many related neuropeptides, and also has protein regions not obviously coding for neuropeptides. It is expressed by a small subset of neurons within the CNS, but these neurons are not obviously related by their ancestries, their positions or their apparent functions. This chapter summarizes our recent results detailing the structure, expression, evolution and genetics of Drosophila FMRFamide,... 

The accessory proteins of the progenitor toxin serve to enhance the stability of the toxin to ensure uptake from the gut. The NTNH component of the multimeric type A toxin complex is encoded by a single gene upstream of the neurotoxin locus while three different HA proteins have been characterized in association with BoNTs. All C. botulinum serotypes have been shown to produce neurotoxin complexes with the NTNH and HA proteins. 

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