Lysine reactive, measurement method

In Figure 1 it is clear that all five procedures showed at least some measure of sensitivity to lysine damage in all heated samples and that generally with increased severity of heat treatment a corresponding decrease in reactive lysine was detected. The SA and DAN methods and to a smaller degree the DB method were more sensitive than the FDNB method, particularly for the most severely damaged samples. The total lysine method was least sensitive. 

A prevalidation study carried out by Cosmetics Europe on this optimized protocol showed that the SkinEthic HCE method consistently discriminated UN GHS classified from non-classified test substances within and between laboratories [47]. A combination of the two exposure times in a testing strategy that allocates test substances to the short or long exposure time depending on their intrinsic chemical reactivity increased the overall accuracy under GHS. The chemical reactivity, i.e., electrophilic potential to react with cysteine- or lysine-containing peptides, was measured by the direct peptide reactivity assay (DPRA) [48]. Reactive substances (peptide depletion is >5.95 % relative to the control) were allocated to the short exposure time, whereas non-reactive substances (depletion <5.95 %) are allocated to the long exposure time. 

The gross protein value is probably the most commonly used biological method for evaluating proteins. Gross protein values measure the ability of proteins to supplement diets consisting largely of cereals and they correlate well with FDNB-reactive lysine figures. 

These have been used widely for estimating protein in such foods as cereals and milk. The methods are rapid and give reproducible results, and attempts have been made to use them for measuring total basic amino acids and reactive lysine. The... 

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