Este trabalho foi conduzido para estudar a distribuição de Cu, Fe, Mn e Zn nas frações proteicas de amostras de trigo submetidas a um procedimento de extração sequencial. Maiores concentrações dos elementos foram determinadas na fração extraída com tampão Tris-HCl contendo 1% de dodecil sulfato de sódio (SDS). As frações da amostra de trigo obtidas após o procedimento de extração foram analisadas por eletroforese em gel de poliacrilamida unidimensional (1D SDS-PAGE) e as bandas de proteínas foram tratadas para quantificar os metais por espectrometria de absorção atômica em forno de grafite (GF AAS). Desta forma, foi possível associar os metais Cu, Fe, Mn e Zn às bandas proteicas de peso molecular específico. As frações proteicas da amostra de trigo foram analisadas por espectrometria de massas por tempo de vôo acoplada à ionização dessortiva de matriz por laser (MALDI-TOF-MS), após procedimento de digestão proteica, identificando-se as proteínas lipid transfer e grain softness, sendo esta última possivelmente associada ao metal manganês.

This work was initially conducted to study the distribution of Cu, Fe, Mn and Zn in the protein fractions of wheat sample subjected to sequential extraction procedure. The highest metal concentrations were determined in the fraction extracted with Tris-HCl buffer containing 1% sodium dodecyl sulfate (SDS). The fractions of wheat sample obtained after the extraction procedure were analyzed by one-dimensional polyacrylamide gel electrophoresis (1D SDS-PAGE) and protein bands were treated to quantify Cu, Fe, Mn, and Zn by graphite furnace atomic absorption spectrometry (GF AAS). Metals were associated to protein bands of specific molecular weight, determined using a standard protein. The protein fractions were also analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) after a typical protein digestion protocol, identifying lipid transfer protein and grain softness, the latter being possibly associated to Mn.

A sequential extraction procedure was applied to wheat and soybean seed samples. The total protein content (determined by two distinct methods: Bradford and bicinchoninic acid-BCA) and distribution of Cu, Fe, Mn and Zn in each fraction was determined. The sequential extraction employed four different solutions: water, 0.5 mol L-1 NaCl, ethanol/water (70:30 v v-1) and 0.5 mol L-1 NaOH. For both samples, the highest concentration of metals was observed in those extracts associated with globulin-type proteins using NaCl solution. Regarding protein content, higher levels were obtained using the BCA method.