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

Química Nova (Impact Factor: 0.66). 01/1998; 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.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This research had as main objective to compare five spectrophotometric methods for protein determination in samples proceeding from sanitary effluent of treatment plant. Intention was to define a methodology that is of fast and easy and reliable application for this type of sample. The stabilization ponds, as systems of biological treatment, have as main constituent proteins, carbohydrates and lipids, but also they present many interfering composites, for example, phenolic urea, detergents and composites, that can harm the quantification of such parameters. The analyzed methods had been Lowry, Biuret, Bradford and Acid bicinconinic. The method of Lowry revealed more adequate to the characteristics of the sample, with good reproducibility, specific reagent, moderate cost and absence of interfering substance.
    Engenharia Sanitaria e Ambiental 06/2008; 13(2):236-242. · 0.18 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Fresh and aged coconut water (CW) samples were introduced directly into the electrospray ionisation (ESI) source, and were combined with the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) technique to characterise in situ chemical compounds produced during natural ageing (from 0 to 15 days) at room temperature (23 °C). The ESI-FT-ICR MS readings were acquired and the data were correlated to conventional methodologies: pH, total titratable acidity (TA), total soluble solids, microbial analyses, and ultraviolet visibility (UV–vis) spectroscopy analysis. In general, the pH and TA values changed after 3 days of storage making the CW unsuitable for consumption. The ESI(−)-FT-ICR data also showed a clear and evident change in the chemical profile of CW after 3 days of ageing in the m/z 150–250 and 350–450 regions. Initially, the relative intensity of the natural markers (the m/z 215 and 377 ions–sugar molecules) decreases as a function of ageing time, with the last marker disappearing after 3 days of ageing. New chemical species were then identified such as: citric (m/z 191), galacturonic (m/z 193), gluconic (m/z 195), and saccharic (m/z 209) acids. ESI(−)-FT-ICR MS is a powerful tool to predict the physicochemical properties of CW, such as the pH and TA, where species such as fructose, glucose, sucrose, and gluconic acid can be used as natural markers to monitor the quality of the fruits.
    Food Chemistry 11/2014; · 3.26 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This study evaluated the effects of microencapsulation process on different proteins. Insulin, albumin and casein were used as model proteins. Three methodologies to determine protein concentrations were compared: ë 280 nm, Lowry and Bradford colorimetric methods. Proteins were submitted to the first phase of double emulsion method, which is commonly used to produce polymeric delivery systems. Different excipient solutions were tested: NaCl, KSCN, MgCl 2 and NaH 2 PO 4 all at 50 mM, PBS and H 2 O were used as controls. Structural analysis of proteins was performed by SDS-PAGE and intrinsic fluorescence intensities. Results showed direct reading at 280 nm the most suitable for quantitative measures of the three proteins presenting linear coefficient (r 2) of 0.9849, 0.9992 and 0.9995 for insulin, albumin and casein, respectively. The excipient solution that allowed greater recovery of proteins was PBS, which recovered 45%, 44% and 90% of albumin, insulin and casein, respectively. For albumin, KSCN solution also enabled recovering 47% of processed protein. Electrophoretic pattern did not revealed fragmentation or aggregation of the three analyzed proteins. Structural analysis of proteins by measuring of intrinsic fluorescence has shown: PBS and NaH 2 PO 4 solutions effectively maintained the integrity of protein structures for albumin, KSCN and MgCl 2 solutions for insulin, and PBS solution for casein. Taken all these results together, it was possible to conclude that phosphate-based solutions are best excipients to protect proteins with higher molecular weights or size, and chaotropic salts, such as MgCl 2 , are the best one to low-molecular weight peptides as insulin.
    International Journal of Latest Research in Science and Technology. 08/2014; 3(4):2278-529931.

Full-text (2 Sources)

Available from
May 15, 2014