Protein digestion chemical methods

A simplified method to estimate nutritive value based on amino acid content corrected for protein digestibility chemical PER) will be mentioned. The role of animal bioassay procedures to measure in-vivo nutrient availability will be emphasised. 

Traditional methods of C-terminal end determination55 were hydrazine degradation, carboxypeptidase digestion, and tritium labeling. Unfortunately, no chemical methods analyzing amino acid sequence sequentially from the C-terminal end is available with reliability similar to that of Edman degradation. Carboxypeptidase digests a protein and... 

CPA is often used for sequencing protein samples. Whereas there is an effective way to sequence from the amino terminus, such as with Edman degradation with phenyl isothiocyanate, there are few such methods for sequencing from the carboxyl terminus (hyclrazinolysis is one such chemical method). Hence, digestion with CPA is a choice whe e one needs to know the amino acid sequence from the C-terminus. The time course of amino acid release is monitored on the amino acid analyzer. This way to use CPA seems to be made even more effective by immobilizing it on a solid support. Bovine enzyine was... 

In order to develop a PLS calibration model for moisture, oil, protein, and linolenic acid in soybeans, a total of 207 calibration and 50 validation samples were used to build and validate the calibration model described in this chapter. While this may seem like a lot of work, 64 coaveraged scans were collected using a Thermo Scientific Antaris IIFTNIR instrument in 30 s with a resolution of 8 cm"k No processing or grinding of the raw soybeans was required, and once the method is validated, no additional calibration is required. The wet chemical methods to measure these four parameters would require grinding, digestion, extraction, and multiple analytical techniques. 

Proteins have different biological availabilities in the human body and a number of methods have been introduced to evaluate and measure protein utilisation and retention. Two types of measurements are used to estimate protein quality biological assays and chemical analysis. The most common measures of protein quality included Biological Value (BV), Protein Efficiency Ratio (PER), Net Protein Utilisation (NPU), Amino Acid Score (AAS also known as chemical score, CS), Essential Amino Acid Index (EAAl) and Protein Digestibility Corrected Amino Acids Score (PDCAAS), amongst other procedures and modifications. 

Chemical Methods. The most common chemical method for digesting proteins uses cyanogen bromide (CNBr) to cleave at methionine residues. CNBr cleaves the amide bond on the C-terminal side of methionine ... 

This method, proposed by Satterlee represents a modification of the chemical score technique. Amino acid analysis is used to determine the essential amino acid profile and an in-vitro proteolytic enzyme step estimates the overall digestibility of the test protein. The in-vitro protein digestibility data, together with the essential amino acid profile, are then used to predict the PER (c-PER). The results obtained so far indicate a good correspondence between the calculated PERs and the actual PERs in the rat assay. The c-PER value is thus an estimate of nutritive value, with correction of the chemical score for digestibility, but it is not a measure of amino acid availability. 

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