Fig. 3.

Effect of Tween 80 on proteinogenic amino acid labeling. The bars from left to right represent isotope peaks of M0 unlabeled fraction, white bar; M1 singly labeled fraction, gray bar; M2 fraction with two labeled carbons, dark bar; M3 fraction with labeled three carbons, diagonal hash; M4 fraction with labeled four carbons, horizontal hash. (−) Indicates the culture without any detergent; (+) indicates the culture with Tween 80. The (M − 57)⁺ fragment was used for Asp, Ala, Ser, and Phe. The (M − 159)⁺ fragment was used for Leu due to its overlapping peak with (M − 57)⁺