Fig. 1
From: Pushing the mass limit for intact launch and photoionization of large neutral biopolymers
Iterative design of high mass oligopeptides for molecular beam experiments. Gramicidin A1, as shown here (1) is the principal component of commercial gramicidin D. Decatryptophan (2) has the highest tryptophan-to-mass ratio of all peptides in our study. Alternating Trp with Lys as in (3) provides better solubility and synthetic scalability. The molecular mass and the volatility can be enhanced by capping the NH2 groups with CO(CH2)2(CF2)7CF3 groups as in (4)–(6). (5) extends (4) to n = 14, with a total of 29 amino acids. (6) extends (5) to n = 25, i.e., it contains 50 amino acids. It is functionalized to increase its molecular weight to 20,201 amu and to expose copious amounts of tryptophan to the vacuum
