Analytical Sciences

Abstract − Analytical Sciences, 30(5), 551 (2014).

Quantification of Proteins by Measuring the Sulfur Content of Their Constituent Peptides by Means of Nano HPLC-ICPMS
Yoshinari SUZUKI, Ayumi NOBUSAWA, and Naoki FURUTA
Faculty of Science and Engineering, Department of Applied Chemistry, Chuo University, 1-13-27 Kasuga, Bunkyo, Tokyo 112-8551, Japan
The sulfur (S) concentrations of three peptides were determined by using nano HPLC-ICPMS under a flow of O2 in an octapole reaction cell, and the determined values showed a good agreement with theoretical values. This method was then applied to trypsin-digested peptides from human albumin for protein quantification. Assigning of the number of S atoms in each peptide/peak and the tryptic digestion efficiency were important for protein quantification. The number of S atoms in each peptide/peak was assigned by using verification scores that gave the lowest standard deviation of the peptide S concentration and the highest S recovery. The peptide concentrations were calculated as the ratio of the S concentration/the number of S atoms in the peptide/peak. The tryptic digestion efficiency was calculated as the sum of the S concentration in the mono-peptides divided by the total S concentration in a native polyacrylamide gel electrophoresis (PAGE) band before tryptic digestion. Our result indicates that a protein can be quantified through peptide quantification, after taking into account the tryptic digestion efficiency, via S quantification using ICPMS.