Reduced proteins, molecular weights

Fig. 1. SDS-PAGE minigel depicting purified IgG preparations derived from human scrum (lane 2), mouse ascitic fluid (lanes 3 and 4), rabbit serum (lane 5), and sheep serum (lane 6). Samples are electrophoresed under reducing conditions and stained with Coomassie blue. All IgGs consist predominantly of two bands comprising heavy (50,000 Mr) and light (22,000 Mr) chains with no major contaminating proteins. Molecular weight markers are shown in lanes 1 and 7 and their molecular weights given on the left.

A denitrifying nitrite reductase from Achromobacter cycloclastes1533 and Ps. denitrificans1534 is a copper protein, containing two moles copper per mole of protein (molecular weight 69 000). This reduces nitrite to nitrogen monoxide. 

The FI SNP (T243M) affects the tripeptide recognition sequence for the giycosylation of the a.sparaginc at position 241. Thus, the FI polymorphism may lead to the loss of one of the nine carbohydrate chains present in the normal enzyme molecule, thereby reducing the molecular weight of the protein and altering its function. 

The Mo enzyme consists of two components (1) the Fe protein (molecular weight 57,000 daltons), which contains iron and sulfur (4 atoms of each per protein) and (2) the MoFe protein (220,000 daltons, Uz subunits), which contains both metals (1 atom Mo, 32 atoms Fe). Each also contains S ions (ca. one per iron), which act as bridging ligands for the metals. The protein contains special Fe—S clusters called P clusters that have EPR resonances like those of no other Fe—S cluster. A soluble protein-fiee molybdenum and iron-containing cluster can be separated from the enzyme. This iron-molybdenum cofactor, or FeMo-co, was known to have approximately 1 Mo, 7-8 Fe, 4-6 S ", and one molecule of homocitrate ion. As for the P cluster, there was no agreement on the structure of FeMo-co for many years. In purified form FeMo-co does crystallize, and it can restore N2 reducing activity to samples of mutant N2ase that are inactive because they lack FeMo-co. On the other hand, no crystal structure of FeMo-co proved possible, and no synthetic model complex was found that could activate the mutant enzyme. 

Protein Molecular weight M) Pullulan reduced molecular weight 21 /nm... 

Hydrolyzed Vegetable Protein. To modify functional properties, vegetable proteins such as those derived from soybean and other oil seeds can be hydrolyzed by acids or enzymes to yield hydrolyzed vegetable proteins (HVP). Hydrolysis of peptide bonds by acids or proteolytic enzymes yields lower molecular weight products useful as food flavorings. However, the protein functionaHties of these hydrolysates may be reduced over those of untreated protein. 

Polyacrylamide gel electrophoresis is one of the most commonly used electrophoretic methods. AnalyMcal uses of this technique center around protein characterization, for example, purity, size, or molecular weight, and composition of a protein. Polyacrylamide gels can be used in both reduced and nonreduced systems as weU as in combination with discontinuous and ief systems (39). 

Assuming the effective molecular weight of the solvent is significantly less than that of the protein/peptides, then equation (17) can be reduced to... 

Three different types of columns packed with gels of different pore sizes are available. Columns should be selected that are suitable for the molecular weight range of specific samples, as each type has a different exclusion limit (Fig. 6.41, page 215). Bovine serum albumin (BSA), myoglobin, and lysozyme show good peak shapes using only 100 mM of sodium phosphate buffer as an eluent. There is no need to add any salt to the eluent to reduce the ionic interaction between protein and gel. 

In a subsequent study, the effect of reducing the ELP molecular weight on the expression and purification of a fusion protein was investigated. Two ELPs, ELP [V-20] and ELP[VsA2G3-90], both with a transition temperature at 40°C in phosphate-buffered saline (PBS) containing 1 M NaCl, were applied for the purification of thioredoxin. Similar yields were observed for both fusion proteins, resulting in a higher thioredoxin yield for the ELP[V-20] fusion, since the ELP fraction was smaller. However, a more complex phase transition behavior was observed for this ELP and therefore a selection of an appropriate combination of salt concentration and solution temperature was required [39]. 

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