Protein concentration level

In general, microsomes/S9 and cofactor (NADPH or UDPG A) are the most costly components of an incubation, but substrate, especially for early discovery compounds, is sometimes scarce. Higher enzyme concentration will lead to higher volume productivity and less amount of the cofactor to maintain the same cofactor concentration. However, the relationship of reaction rate and enzyme concentration may not be linear, so a higher enzyme concentration may yield lower enzyme productivity (amount of product per milligram enzyme used). Therefore, different protein concentration levels should be screened to obtain a good balance between volume and enzyme productivities. 

Protein-Based Substitutes. Several plant and animal-based proteins have been used in processed meat products to increase yields, reduce reformulation costs, enhance specific functional properties, and decrease fat content. Examples of these protein additives are wheat flour, wheat gluten, soy flour, soy protein concentrate, soy protein isolate, textured soy protein, cottonseed flour, oat flour, com germ meal, nonfat dry milk, caseinates, whey proteins, surimi, blood plasma, and egg proteins. Most of these protein ingredients can be included in cooked sausages with a maximum level allowed up to 3.5% of the formulation, except soy protein isolate and caseinates are restricted to 2% (44). 

Isolated soy proteins have also been used in whipped toppings. Soy-protein-based toppings have a lower protein concentration than caseinate-based toppings. Formulations ate adjusted to protein levels, and higher protein levels can result in off-flavors. Typical formulations for a Hquid frozen, prewhipped product are given in Table 18. 

In some patients with IgA nephropathy (IgAN), intraglomerular coagulation plays a role in depositing fibrinogen (235,236). IgAN patients treated with urokinase show a marked improvement in urinary protein concentration, semm creatinine, and blood urea nitrogen levels (237). 

In a different study, it was determined that the concentration range of whey protein required for a fibrous texture suitable for meat extenders. Consumer evaluation showed that 48% whey protein was the optimal level, with no benefits obtained by raising the protein concentration. 

Allen et al. (2007) produced puffed snack foods with com starch and pregelatinized waxy starch, WPC and instantized WPC, and protein concentrations of 16%, 32%, and 40% and showed that the air cell size, extru-date expansion ratio, and water solubility index decreased proportionally as protein and com starch levels increased. Protein concentration significantly affected total soluble protein, water absorption index, and water-soluble carbohydrate. A covalent complex between amylase and protein formed in the presence of cornstarch, but protein-protein interactions appeared with the presence of low levels of pregelatinized waxy starch. 

Add the desired number of beads to a solution of carrier-free Na125I in iodination buffer at a concentration level of about 1 mCi per 100 pg of protein to be modified. The total reaction volume should be 100-1,000 pi per bead. 

Dissolve the amine-containing protein to be activated in 0.1 M sodium phosphate, pH 7.2 (coupling buffer). A protein concentration of l-10mg/ml in buffer will work well in this protocol. For more dilute protein solutions, greater quantities of the NHS-PEG,-maleimide compound may have to be added to obtain equivalent levels of modification. 

Add formaldehyde to a final concentration of 0.125-1 percent (w/w) (optimize to find the best concentration level for the particular protein being studied). 

Add the labeled bait protein to a sample containing the putative interacting prey proteins. The quantity of bait protein to be added to a given sample should be within the same concentration level as the amount of prey proteins present. The optimal level of addition may have to be determined by varying the amount of bait protein concentrations in a number of sample solutions to decide which concentration results in the best interaction complexes being formed. 

Adenosine and inosine can be transported across cell membranes in either direction, facilitated by a membrane-associated nucleoside transport protein. Concentrative transporters have also been identified. Messenger RNA for a pyrimidine-selective Na+-nucleoside cotransporter (rCNTl) and a purine-selective Na+-nucleoside cotransporter (rCNT2) are found throughout the rat brain. Most degradation of adenosine is intracellular, as evidenced by the fact that inhibitors of adenosine transport, such as dipyridamole, increase interstitial levels of adenosine. Dipyridamole is used clinically to elevate adenosine in coronary arteries and produce coronary vasodilation. In high doses, dipyridamole can accentuate adenosine-receptor-mediated actions in the CNS, resulting in sedation and sleep, anticonvulsant effects, decreased locomotor activity and decreased neuronal activity. 

Amino Acid Content. Amino acid content of field pea products is related to protein level, method of processing, and fraction (starch or protein). The protein fraction contains fewer acidic (glu, asp) amino acids than the starch fraction and more basic (lys, his, arg) amino acids than the starch fraction. Also, there are more aromatic (tyr, phe) amino acids, leu, iso, ser, val, and pro in the protein fraction than in the starch fraction (5). An amino acid profile of pea protein concentrate shows relatively high lysine content (7.77 g aa/16 g N) but low sulfur amino acids (methionine and cystine) (1.08-2.4 g aa/16 g N). Therefore, it is recommended that air classification or ultrafiltration be used because acid precipitation results in a whey fraction which contains high levels of sulfur amino acids (12,23). Also, drum drying sodium proteinates decreases lysine content due to the Maillard reaction (33). 

In the study by Thompson, et al. (11), the ml of gel released per 100 g emulsion for the reference emuTsion without soy, with soy isolate (SIF), soy concentrate (SCF) or soy flour (SF) was 6.07, 5.83, 5.49 and 3.08, respectively, when the hydration ratios were 1 4 (flourrwater) for SIF, 1 3 for SCF and 1 2 for SF. The ml gel released per 100 g emulsion containing 10, 15, 20, and 25% soy protein was 6.70, 5.01, 3.94 and 3.57, respectively. When soy protein concentrate was incorporated into an emulsion at the 3.5% level, the processing yields, textural profile and sensory textural attributes of frankfurters were not different among the products with and without added soy concentrate (13). An objective measure of compression and shear modulus indicated that soy protein concentrate incorporated into frankfurters at the 3.5% level had no effect on batter strength or texture ( M). The addition of a cottonseed protein to frankfurters to replace 5, 10 or 15% of the meat resulted in higher pH, less cured color, less firmness of skin, softer texture and reduced desirability as judged by a sensory panel (J5J. 

Soy Protein Concentrates. Both non-functional (low or no solubility) and functional (good solubility, emulsification capacity, and dispersibility) soy protein concentrates (70% protein, dry basis) are commercially available for use in meat products (2-4, 6, j), 15) Normally, a highly functional product with no harsh or bitter flavors is desirable. When used to replace lean meat, non-hydrated concentrate can be used at levels up to 6-7% in finished nonspecific emulsion meats Higher replacement levels or formulas with specific cost/nutrition requirements may use soy protein concentrate with a judicious amount of textured soy protein (6). Excellent yields, cost savings, texture, flavor and nutrient profiles are possible. However, most soy protein concentrates lack sufficient solubility or sufficiently low viscosities to be used in brines for absorption or injection into whole muscle tissue. When legal standards for protein content exist (13), more concentrate must be used to achieve legal minimums. Brine viscosities increase and uniform distribution of brine components throughout the specific whole muscle piece is restricted. Finished product appearance and flavor are easily compromised. Thus, use of soy protein concentrates in whole muscle applications is limited. 

Characteristically, legume seeds are rich in protein and contain intermediate to high levels of lysine and threonine which are important in balancing the deficiencies of these essential amino acids in cereal diets. Certain legume proteins, such as soybean, also exhibit strong functional properties, especially water solubility, water and fat binding and emulsification. Thus soybean flours, protein concentrates and isolates have been used widely as nutritional supplements and functional ingredients in foods. 

The protein concentration in the field pea proteinate was only 87.7% due to the presence of significant quantities of ash, lipid and carbohydrate (Table I). Both refined starches were relatively pure, the protein levels being only 0.5%. The merits of producing protein and starch isolates as opposed to concentrates by the dry process would depend on their relative functional properties and the requirements of the end-user. 

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