Protein digestion studied

Experimentation showed that the protein was not glycosylated and that the sequence at the iV-amino acid terminus corresponded to that expected. The C-terminus sequence, however, did not correspond to that predicted and these data were interpreted in terms of the presence of a heterogeneous, truncated, protein. A study of the tryptic digest fragments from this protein with matrix-assisted laser desorption ionization (MALDI) with post-source decay enabled the authors to suggest the positions at which the parent protein had been truncated. 

Huber s group recently prepared poly(styrene-co-divinylbenzene) monolithic columns in the capillary format using tetrahydrofuran/decanol mixtures as poro-gen. These columns were tested for the HPLC separation of protein digests followed by ESI MS detection enabling protein identification [129]. This technique represents an important contribution to the currently emerging techniques for studying of proteomes as it is more convenient and accurate to use than the classical 2-D gel electrophoresis. 

A protein identification study might proceed in the following manner. Pirst, the protein is analyzed by mass spectrometry to determine its molecular mass to within 0.01%. Second, the protein is digested with an enzyme, commonly trypsin. The enzyme trypsin cleaves polypeptide chains at points following lysine and arginine residues. Using this proteolytic enzyme ensures that each... 

Komaki et al studied the protein digestibility of whole organisms of C. vulgaris in in vitro and in vivo experiments to evaluate the difference of... 

Investigations have focused on the content or polyphenolics. tannins, and related compounds in various foods and the influence on nutrient availability and protein digestibility. It has been established that naturally occurring concentrations ofpolyphcnoloxtda.se and polyphenols in products such as mushrooms can result in reduced iron bioavailability. Likewise, several studies have locused on decreased protein digestibility caused hy the tannins of common beans and rapeseed (canola). 

The advantages of an animal bioassay are that protein digestibility, amino acid bioavailability, and the presence of antinutritional factors can be ascertained. However, animal-based feeding studies can be difficult. First, these assays are expensive to conduct and time-consuming. Secondly, these assays require animals... 

Base Hydrolysis. Protein digestions in basic media have proven to be no panacea. Early studies employed 4.2N sodium hydroxide and saw success with pure proteins (68). Collaborative studies (69,70) have since shown optimized recoveries of 85% for NaOH hydrolyses in complex food samples. In general, for samples rich in fats and carbohydrate, attempts to use starch or ascorbic acid as protective agents have shown little improvement in recoveries. 

Palamidis and Markakis ( 1 2) conducted a thorough study to evaluate not only the PER of toasted products but also their net protein ratios (NPRs) and digestibilities. They reported that light toasting reduced the PER of bread to 0.40 (NPR 1.11) and dark toasting to 0.16 (NPR 0.95). The protein digestibility decreased as the intensity of toasting increased. 

Enzyme assays As shown previously the LMW fraction had a repressing effect on the protein digestion in the in vivo experi-ment. Accordingly, it was of interest to study in vitro the effect of this fraction on the kinetics of reactions catalyzed by proteases and peptidases present in the gastro-intestinal tract. 

Peptide mapping studies, generated by the cleavage of a protein into peptide fragments, must be highly reproducible and quantitative. Several electropherograms of protein digests have been obtained when chicken ovalbumin was cleaved by trypsin... 

Simonato, B., Pasini, G., Giannattasio, M., Peruffo, A.D., De Lazzari, F., and Curioni, A. 2001. Food allergy to wheat products The effect of bread baking and in vitro digestion on wheat allergenic proteins. A study with bread dough, crumb, and crust. JAgric Food Chem 49(11) 5668-5673. 

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