We have studied Schizosaccharomyces pombe, Saccharomyces cerevisiae, Scheffersomyces (Pichia) stipites, and Kluyveromyces marxianus yeast using the modified IBAQ label-free method with the spiked universal protein standard (UPS2). Each species had been prepared in 3 culturing replicates, and the similarity of the replicates was assessed using the TMT relative quantification methodology.