Protein, attributes

Proteins are one of the most important ingredients in food production for both animals and humans. Besides having nutritional properties, protein contributes to the functional and organoleptic properties of food. The nutritional value of a protein depends on the total essential amino acid content. However, the availability of amino acids is conditioned by some protein attributes, mainly digestibility. 

Knowledge of protein primary sequence, quantities, posttranslational modifications (PTMs), structures, protein-protein (P-P) interactions, cellular spatial relationships, and functions are seven important attributes (see Table 4.2) needed for comprehensive protein expression analysis. It is this multifold and complex nature of protein attributes that has spawned the development of so different many proteomic technologies. Some of these challenges in proteomic analysis include defining the identities and quantities of an entire proteome in a particular spatial location (i.e., serum, liver mitochondria, brain), the existence of multiple protein forms and complexes, the evolving structural and functional annotations of the human and rodent... 

Proteomic platforms combine separation and identification technologies that can be completed as an experiment in a timely fashion. Proteomic platforms strive to accomplish five critical objectives (1) a high level of information about one or more protein attributes (2) a large number of samples per analysis session (sample throughput) (3) quantitative and comparative protein expression among samples (4) timely analysis of raw and processed data and (5) use of a discovery-oriented or open platform system. 

The many attributes of proteins mentioned in Table 4.2 make complete global analysis of proteins from cells, tissues, organs, or organisms a formidable analytical challenge. A primary aim of proteomic analysis is to provide researchers with as much data as possible about one or more protein attributes. Flowever, to many researchers, proteomic analysis usually involves the three attributes of identification and quantitation of all proteins in a defined sample space. Only the highlights of each platform will be summarized here. A critical appraisal of capabilities, advantages, and drawbacks are summarized in Figure 4.13 (Section 4.5.6). 

These protein attributes are then submitted to a database search. This search identifies a protein by looking at the best match between experimental data and data obtained by in-silico processing and digestion of a protein sequence database. The identification and characterization procedures using bioinformatics tools will be the topic of Section 4.4. 

From 2-DE gel spots, protein identification can be performed using various methods, as described in Section 4.4. All of these approaches imply a serial process, starting from a single-step or multiple-step chemical processing of the entire proteins and followed by the measurement and the interpretation of the produced protein attributes, then by specific queries in protein sequence database. The outputs of such searches are interpreted and used, first, to annotate the 2-DE image with the identification results and, second, to focus on the biological relevance of the expression level of the interesting protein spots. 

Three decades elapsed between the first isolation of erythrocuprein and the discovery of a catalytic function for this protein. Attributable to the high interest in the biochemistry of reactive oxygen species, numerous enzymatic assays for superoxide dismutases were developed in the last years. Nevertheless, the original assay of McCord and Fridovich is still currently used for routine purposes The reactivity of super-... 

Protein attribute (MSorMSMS) Mowse Probabilistic models OWL http //srs.hgmp.mcr.ac.uk/ Pappin et at., 26... 

The advantages of resonance Raman spectroscopy have already been discussed in section BL2.2.3. For these reasons it is rapidly becoming the method of choice for studying large molecules in solution. Flere we will present one study that exemplifies its attributes. There are two complementary methods for studying proteins. 

The simplest nutritional role of fats in the diet is that of energy supply. There are differences between members of the same class of food materials, but the accepted convention attributes a value of 9 kcal (37.7 kJ) of energy per gram of fat, and 4 kcal (16.7 kJ) of energy per gram of all carbohydrates and proteins. This is a serious consideration in generating weight loss diets. 

Table 11 presents data on the protein quaUty of a variety of LPC products obtained from rat-feeding studies. Typical protein efficiency ratio (PER) values for LPCs derived from alfalfa range from 1.41 without supplementation to 2.57 with 0.4% methionine added casein can be adjusted to a PER of 2.50 (98,100). Biological values (BV) of mixtures of LPCs, such as barley and rye grass or soybean and alfalfa, maybe higher than either LPC alone. The effect has been attributed to the enhanced biological availabihty of lysine in these mixtures (99). 

Metabolic Functions. The functions of the thyroid hormones and thus of iodine are control of energy transductions (121). These hormones increase oxygen consumption and basal metaboHc rate by accelerating reactions in nearly all cells of the body. A part of this effect is attributed to increase in activity of many enzymes. Additionally, protein synthesis is affected by the thyroid hormones (121,122). 

Use of some oilseed proteins in foods is limited by flavor, color, and flatus effects. Raw soybeans, for example, taste grassy, beany, and bitter. Even after processing, residues of these flavors may limit the amounts of soybean proteins that can be added to a given food (87). The use of cottonseed and sunflower seed flours is restricted by the color imparted by gossypol and phenoHc acids, respectively. Flatus production by defatted soy flours has been attributed to raffinose and stachyose, which are removed by processing the flours into concentrates and isolates (88). 

Fmctose is a highly reactive molecule. When stored in solution at high temperatures, fmctose not only browns rapidly but also polymeri2es to dianhydrides [38837-99-9] [50692-21-2] [50692-22-3] [50692-23-4] [50692-24-5]. Fmctose also reacts rapidly with amines and proteins in the nonen2ymatic or MaiUard browning reaction (5). This is a valued attribute in baked food products where cmst color is important. An appreciation of these properties allows the judicious choice of conditions under which fmctose can be used successfully in food appHcations. 

Despite the intrinsically nonspecific nature of ion-exchange and reversed-phase/hydrophobic interactions, it is often found that chromatographic techniques based on these interactions can exhibit remarkable resolution this is attributed to the dynamics of multisite interactions being different for proteins having differing surface distributions of hydrophobic and/or ionizable groups. 

MVP, textured vegetable protein. Possibly attributable to fatty acids in the margerine used to make biscuits containing Arcon F. 

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