Influence of the Lipid Phase Removal on the Quantification of Cu, Fe and Zn Bound to Proteins from Golden Flaxseed (Linum usitatissimum L.)

The analysis of metals bound to proteins requires careful sample preparation. Experimental procedures involved in this area should be developed aiming to retain the metal species bound to the protein structure. Some pre-fractionation steps are commonly used and in many cases it is necessary to disrupt the lipid-protein interaction by performing lipid removal before protein extraction. This paper presents a systematic investigation on the influence of using hexane, chloroform and methanol neat or in sequence to remove the lipid fraction in golden flaxseed (Linum usitatissimum L.), before extracting the protein phase using Tris-HCl buffer solution for analysis of Cu, Fe and Zn bound to proteins. The results showed that the organic solvent used has a strong influence on the determination of these metals. With hexane, the total protein content and Cu, Fe and Zn concentrations in Tris-HCl phase were higher than those found using methanol:chloroform (1:2 v/v).