Proteins digestion and

The previous chapters have dealt mainly with LC/MS analysis involving short run times, many samples, and relatively small numbers of compounds in samples. What about samples containing very complex compound mixtures, for example, natural products, samples from biomarker discovery, protein digests, and QA/QC method development or metabolite identification samples requiring detection of every component Such workflows often require several analysis steps with different columns and different mobile phases and pH values to increase the separation probability by changing the selectivities of individual runs. 

A3. Albanese, A. A., Davis, V. I., Smetak, E. M., Lein, M., and Fisher, M., Amino acid analysis of the nondiffusible fraction of enzymatic protein digests and human urine. Arch. Biochem. Biophys. 20, 47-54 (1949). 

Table III. Effect of In Vitro Pancreatic Digestion pH on Carbohydrate and Protein Digestion and Calcium Solubility...

PS/DVB Reversed phase PepSwift Dionex Corporation 50x0.1 mm 50x 0.2 mm 50x0.5mm Nano and cap-HPLC of peptides, protein digest and intact proteins... 

However, since the PER is an in vivo test, protein digestibility and amino acid bioavailability are encompassed to some extent within the assay. Despite these advantages, it is difficult to determine the individual contribution of digestibility and bioavailability of individual amino acids, or of individual proteins in a complex mixture, on overall protein quality. There are indications that the assay can be shortened from 4 weeks to 2 weeks with little loss in accuracy (Hackler, 1977). 

PDCAAS (%) is calculated as the product of the true protein digestibility and the amino acid score (or lowest amino acid ratio) relative to reference protein. Amino acid composition of protein is determined by hydrolyzing the protein into its component amino acids and then separating the amino acids chromatographically as described below. True protein digestibility is determined according to Alternate Protocol 2. 

Since one of the functions of protein synthesis is to manufacture digestive enzymes, unchewed food causes a drop in protein digestion and ultimately.... retardation of growth. 

There are some reports on possible mechanisms behind these effects of severe heat treatment. Adrian (1) has shown that water-soluble premelanoidins from a glucose-glycine reaction mixture reduce the protein digestibility and affect the utilization of... 

Excess heat applied during feed processing can also result in reduced protein digestibility and utilization, due to reaction of AAs with soluble sugars. 

On-line protein digestion has been achieved by trypsin adsorbed in a porous PVDF (poly [vinylidene fluoride]) membrane (0.45-pm pore) coupled in a PDMS chip. In this way, on-chip protein digestion and subsequent MS analysis have been carried out for horse heart cytochrome c [817]. 

Figure 2. Effect of Alkylation of Casein By Chlorogenoquinone on in vitro Protein Digestibility and Relative Growth of larval Spodoptera exigua. 1.0% casein was treated CHA concentrations shown and with 0.100 change in OD yQ/min/gm diet PPO. Larval growth and protein digestibility reported as percent control where control equals 100%.

Proteins react with polyphenols such as phenolic acids, flavonoids, and tannins, which occur widely in plant products. These reactions may result in the lowering of available lysine, protein digestibility, and biological value (Hurrell 1984). 

Traditional methods to map posttranslational modification sites, like those of phosphorylation, have been anchored by protein digest and mass spectroscopic (MS) approaches (for a review on the classic evaluation and for MS analyses of O-glycans, see Reference (56)). Unfortunately, like many posttranslational modifications, O-GlcNAcylation occurs routinely on a protein population with substoichiometric frequency, which results in a very small detectable population of a O-GlcNAc-modified product. Also, much like O-phosphate additions, the protein-O-GlcNAc bond is labile and is detached by collision-induced dissociation (CID) during MS analysis. Often, the bond is lost before it can be detected on the peptides analyzed (57, 58). Phosphate modifications, however, can overcome this limitation by emiching the peptide mixtures... 

The process of digestion and the activity of carbonic anhydrase are major ev cryday concerns in the medical profession. A clearer understanding of the concepts of protein digestion and carbonic anhydrase acti ity is provid by simplified descriptions of the relevant biochemical mechanisms. Protein digestion involves the addition of water to a peptide bond. Carbonic anhydrase activity involves the addition of water to COj. A related process, the phosphorolysis of glycogen, is also described. 

Elevated levels of the hormone homocysteine, a by-product of protein digestion and metabolism, have been linked to age-related diseases such as heart disease and Alzheimer s. Research shows that by reducing our consumption of acidic protein foods, such as meat, we may be able to reduce and control our homocysteine levels. Studies have also shown that the B vitamins B6, Bi2, niacin, and folate can help lower levels of homocysteine in the blood.2... 

Eggum, B.O. 1992. The influence of dietary fiber on protein digestion and utilisation, in Dietary Fiber—A Component of Food, Nutritional Function in Health and Disease, eds., T.F. Schweizer and C.A. Edwards, New York Springer-Verlag. 

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