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Determinação de proteínas totais via espectrofometria: vantagens e desvantagens dos métodos existentes

Química Nova (Impact Factor: 0.66). 11/1998; 21(6). DOI: 10.1590/S0100-40421998000600020
Source: DOAJ

ABSTRACT

Spectrophotometric determination of total protein is used in several areas such as clinical analysis, food science and technology, biochemistry, protein chemistry, physiology. Five spectrophotometric methods are mostly used: biuret, Lowry, Bradford, Smith and UV absorption. In this review a general overview of these methods is presented (interferences, applications); other methodologies are also discussed.

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Available from: Dimas Augusto Morozin Zaia, Jan 05, 2014
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    • "Such data can provide important information about physiological processes in cells, nutritional value of organisms, and exploitation of resources in biotechnological and commercial activities (Lourenço et al., 2004), among others. Many methods have already been developed over the years for the determination of protein, but in view of the diversity of materials/species and their composition of proteins, there is not a method universally used in a sucessfull form for all kinds of samples and organisms (Zaia et al., 1998). The extraction of the protein content is one of the main problems in protein analysis, since it presents varying degrees of efficiency, depending on the method used and the characteristics of the species studied (Barbarino & Lourenço, 2005). "
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    ABSTRACT: The chemical profiles of Desmapsamma anchorata, Hymeniacidon heliophila (Porifera), Bunodosoma caissarum, Renilla muelleri (Cnidaria), Aplysia brasiliana, Eledone massyae, Isognomon bicolor (Mollusca), Echinaster brasiliensis, Echinometra lucunter, Holothuria grisea, Lytechinus variegatus (Echinodermata), and Phallusia nigra (Chordata) were determined. Hydrosoluble protein was the most abundant class of substances for all species, except for the ascidian Phallusia nigra, in which the carbohydrate content was higher. The percentages of hydrosoluble protein (dry weight, dw) varied widely among the invertebrates, ranging from 5.88% (R. muelleri) to 47.6% (Eledone massyae) of the dw .The carbohydrate content fluctuated from 1.3% (R. muelleri) to 18.4% (Aplysia brasiliana) of the dw. For most of the species, lipid was the second most abundant class of substances, varying from 2.8% (R. muelleri) to 25.3% (Echinaster brasiliensis) of the dw. Wide variations were also found for the invertebrates nitrogen content, with the lowest value recorded in the cnidarian R. muelleri (2.02% of the dw) and the highest in the molluscan E. massyae (12.7% of the dw). The phosphorus content of the dw varyed from 0.24% (R. muelleri) to 1.16% (E. massyae). The amino acid composition varied largely among the species, but for most of the species glycine, arginine, glutamic acid, and aspartic acid were the most abundant amino acids, with histidine and tyrosine among the less abundant amino acids. The actual content of total protein in the samples was calculated by the sum of amino acid residues, establishing dw values that fluctuated from 11.1% (R. muelleri) to 66.7% (E. massyae). The proteinaceous nitrogen content was high in all species, with an average value of 97.3% of the total nitrogen. From data of total amino acid residues and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-to-protein conversion factors ranged from 5.10 to 6.15, with an overall average of 5.45. The use of the specific nitrogen-to-protein conversion factors established here is recommended, since it would yield more accurate determinations of total protein in the species tested in this study.
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    • "Protein concentration was 0.038 and 0.034 mg.ml -1 for T. viride and T. harzianum, respectively. Determining the extracellular protein concentration is not always a simple task, since various factors may interfere with the final result ‎ [1]; ‎ [75]. Such differences are also due to the fact that different enzyme isolates have different primary structures, besides different degrees of glycosilation. "
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    ABSTRACT: Two strain of Trichoderma (T. viride and T. harzianum) were isolated and used for β glucanase enzyme production. The succinoglycan was produced by fermentation of sucrose by Agrobacterium radiobacter and its chemical structural properties were investigated by TLC, FT-IR and 1H-NMR spectroscopy. The results showed that the biogum is composed of glucose and galactose units, carrying pyruvate, succinate and acetate groups and indicated the presence of succinoglycan. The highest β glucanase activity was observed in T. harzianum. The SDS-PAGE profiles have several enzyme bonds such as β(1,3), β(1,4) and β(1,6) glucanase. The T. harzianum and T. viride have both enzyme bonds of β(1,3) glucanase and β(1,6) glucanase. Cel6A (CBH II) only was observed in T. harzianum. The high values β-succinoglycanase activity in T. harzianum due to present of β(1,3), β(1,6) glucanse enzymes and synergism that occurs between of them. Succinoglycan is a good substrate for total β-glucanase activity assay.
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