Crystalline protein, solubility

The roles of the extensions in /3-crystallin subunit structure and function are matters of debate. It would seem, however, that they are involved in regulating interactions between the /3-crystallin subunits and their interactions with the Gland 7-crystallin subunits. As the concentration of proteins within the lens is very high, these interactions are of great importance in ensuring crystallin protein solubility and hence the maintenance of lens transparency. However, the specifics of which /3-crystallin subunits interact with each other, and the role of the extensions in this process, are not known, and extensive NMR analysis is required to elucidate the hierarchy of subunit interactions. Furthermore, the extensions in the /3-crystallin subunits undergo extensive post-translational modification, especially proteolysis, and these age-related changes alter the electrostatic interactions between the subunits. 

The bacterial culture converts a portion of the supplied nutrient into vegetative cells, spores, crystalline protein toxin, soluble toxins, exoenzymes, and metabolic excretion products by the time of complete sporulation of the population. Although synchronous growth is not necessary, nearly simultaneous sporulation of the entire population is desired in order to obtain a uniform product. Depending on the manner of recovery of active material for the product, it will contain the insolubles including bacterial spores, crystals, cellular debris, and residual medium ingredients plus any soluble materials which may be carried with the fluid constituents. Diluents, vehicles, stickers, and chemical protectants, as the individual formulation procedure may dictate, are then added to the harvested fermentation products. The materials are used experimentally and commercially as dusts, wettable powders, and sprayable liquid formulations. Thus, a... 

Materials produced by crystalliferous bacilli which elicit a toxic response in susceptible insects may be separated into two types. The first type, the true toxins, include the crystalline protein inclusion body the parasporal body of Hannay (14)], a heat-stable, water-soluble exotoxin active against flies, a heat-stable, dialyzable water-soluble exotoxin, toxic to Lepidoptera on injection (23), and a heat-labile, water-soluble, filterable exotoxin, toxic toward larch sawfly larvae (Hymenoptera) which was reported by Smirnoff (31). 

Carbodiimides are, in general, useful compounds for effecting certain dehydrative condensations, e.g., in the formation of amides, esters, and anhydrides. These two crystalline water-soluble carbodiimides are especially useful in the synthesis of peptides and in the modification of proteins. The excess of reagent and the co-product (the corresponding urea) are easily separated from products with limited solubility in water. The hydrochloride is best employed in nonaqueous solvents (methylene chloride, acetonitrile, dimethylformamide). The methiodide is relatively stable in neutral aqueous systems, and thus is recommended for those media. 

Both methods are also limited in accuracy of secondary structure determinations because spectral peaks must be deconvolved estimates are made of the overlapping contributions of different structural regions. These estimates may introduce error based on the reference spectra used and because deconvolution methods equate crystallographic secondary structure with the secondary structure of the protein in solution (Pelton and McLean, 2000). As amyloid fibrils are neither crystalline nor soluble, there may be even greater error in estimates of secondary structure. To compound the problem, estimates of /f-sheet content are less reliable than those of a-helix, because of the flexibility and variable twist of / -structure (Pelton and McLean, 2000). In addition, / -sheet and turn bands overlap in FTIR spectroscopy (Jackson and Mantsch, 1995 Pelton and McLean, 2000). Side chains also contribute to spectral peaks in both methods, and they can skew estimates of secondary structure if not properly accounted for. In FTIR spectra, up to 10-15% of the amide I band may arise from side chain contributions (Jackson and Mantsch, 1995). 

Figure 1. Solubility behavior of a pure crystalline protein...

Interfacial films of protein coagulate under certain conditions, the properties of the coagulated protein being quite different from those of the original crystalline protein. F or example, solubility is lost. 

Properties Crystalline protein. Mw approximately 33,300. Almost insoluble in water soluble in dilute acids and acidified methanol and ethanol. 

Since solubility is the concentration of protein in solution at equilibrium with the solid phase, the state of protein in the solid phase affects the solubility in the solution phase. Theoretical treatment of the protein solubility problem has often ignored solid phase interactions of the protein due to its complexity. A crystalline solid phase is expected to render a lower solubility than the amorphous solid phase. However the complexity and the heterogeneity of the protein in the solid state (e.g. amorphous, gel, or crystalline, or precipitates of native or denatured forms) makes it difficult to directly assess solid state effects. 

Glycosylation of the lens crystallin proteins (All, C8, C9, H6a, M5, M31, P4, S45) is of considerable interest because of the long-lived nature of the a, P, and 7 crystallins, the molecular aggregation and decreased solubility of the glycosylated products, the possibility of further reactions leading to browning effects (M28, M29), and their relevance to cataract formation and other complications in diabetes and aging. 

For example, lysozyme is documented to undergo a crystalline phase transition from tetragonal (low temperature form) to orthorhombic (high temperature form) at approximately 25 °C (Pusey and Gernert 1988). Protein solubility can increase, decrease or remain constant as the temperature of the system increases. All three effects have been observed on real protein systems. 

Leaves and subterranean plant organs are additional sources of protein materials. Potato proteins are largely available as a by-product of the starch extraction. A promising source of soluble proteins is represented by the leaves of many species leaves contain about 80-90% water and 10-20% organic material, a small part of this (10-30%) is made of proteins. About 50% of the proteins are water soluble and can be extracted and purified as a crystalline protein fraction with a molecular weight in the range 10-60 kDa, suitable for food and cosmetic purposes (leaf protein concentrate) (18). 

The major structural protein components of the lens are the crystallins whose function is to maintain transparency and refractive power. They constitute about 90% of the soluble proteins in the lens and consist of two superfamilies a and (/3H/3L and y) with molecular masses of between 900 and 21 kD (Table 9.1). 

Poly(HASCL) depolymerases are able to bind to poly(3HB)-granules. This ability is specific because poly(3HB) depolymerases do not bind to chitin or to (crystalline) cellulose [56,57]. The poly(3HB)-binding ability is lost in truncated proteins which lack the C-terminal domain of about 60 amino acids, and these modified enzymes do not hydrolyze poly(3HB). However, the catalytic domain is unaffected since the activity with water-soluble oligomers of 3-hy-droxybutyrate or with artificial water-soluble substrates such as p-nitrophenyl-esters is unaffected [55, 56, 58, 59]. Obviously, the C-terminal domain of poly(3HB) depolymerases is responsible and sufficient for poly(3HB)-binding [poly(3HB)-binding domain]. These results are in agreement ... 

Rapid-acting dermally hazardous cytotoxin that inhibits protein synthesis and affects clotting factors in the blood. It is capable of producing incapacitating or lethal effects. T2 is obtained from various molds and fungi (Fusarium sp.). It is a colorless crystalline solid of white powder that melts at 304°F. Impure samples may be a colorless to slightly yellow oil. It is slightly soluble in water, but soluble in ethyl acetate, acetone, ethanol, chloroform, methylene chloride, diethyl ether, and dimethyl sulfoxide (DMSO). It is heat stable and can be stored at room temperature for years. 

Silk proteins (spidroins in spiders and fibroins in Lepidoptera insects) are assembled into well-defined nanofibrillar architectures (Craig and Riekel, 2002 Eby et al., 1999 Inoue et al., 2000b, 2001 Li et al., 1994 Putthanarat et al, 2000 Vollrath et al., 1996). Spidroins and fibroins are largely constructed from two chemically distinct repetitive motifs or blocks (Table I), an insoluble crystalline block and a soluble less-crystalline block (Craig, 2003 Fedic et al., 2002 Hayashi and Lewis, 2000 Hayashi et al., 1999). The crystalline blocks are composed of short side-chained amino acids in highly repetitive sequences that give rise to /1-sheet structures. 

According to Flory (10), the concept that proteins and carbohydrates are polymeric goes back to at least the work of Hlasiwetz and Habermann (11). In 1871 they proposed that these substances were made up of a number of species differing from one another with respect to the degree of molecular condensation. Flory also noted that Hlasiwetz and Habermann differentiate "soluble and unorganized" members of these substances, for example dextrin and albumin, from "insoluble organized" members, such as cellulose or keratin. This distinction is the precursor of the present day differentiation between non-crystalline and crystalline polymers. 

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