T1P and TPO) display a different trend, with a greater increase in hydrogen bond formation to the proton of N self upon deprotonation of the phosphate group (i.e., when T1P becomes TPO) and a non-negligible increase in the hydrogen bond formation propensity for the proton of N cap . For these residues, ff99SB yields a slight increase in hydrogen bonding to N self upon deprotonation of the phosphate group, but a decrease in hydrogen bonding to N cap . FB18, however, is able to recapitulate the experimental trend, with a large increase in hydrogen bond formation to the proton of N self and a modest increase in hydrogen bond formation to the proton of N cap . In this case it appears that FB18 is able to more faithfully reproduce the hydrogen bonding trends than ff99SB. -0.10 ± 0.01 0.034 ± 0.005 ↑ Note: The "Expt. Trend" column represents a qualitative interpretation of chemical shift data given in Lee et al.