Native exchange NMR None log(P) >~ 5 EDPEVLFKNKGCVACHAIDTKMVGPAYKDVAAKFAGQAGAEAELAQRIKNGSQGVWGPIPMPPNAVSDDEAQTLAKWVLSQK

Hydrogen-exchange rates were measured by monitoring the change in the TOCSY or 1D amide proton peak intensity as a function of time after exchanging a lyophilized sample into D2O. To initiate hydrogen exchange, a sample of oxidized Pa cyt c551 (3.0 mM protein, 5 times molar excess K3[Fe(CN)6], 50 mM NaPi pH 6.0) was lyophilized and dissolved in D2O. The pH* (uncorrected pH value) was immediately adjusted to 6.0 and data acquisition began 8 min after commencement of exchange. 1D (8 scans) and 2D TOCSY (32 scans) spectra were collected without solvent suppression using a Varian INOVA 500 MHz spectrometer at 300 K. Each TOCSY spectrum (4,096 ·256 points, with a 1.1-s recycle time) took about 5 h to acquire. TOCSY data were collected at 8, 13, 18, 25, 32, 37, 42, 96, and 317 h after initiation of exchange.

Native exchange NMR None 4 < log(P) < 5 EDPEVLFKNKGCVACHAIDTKMVGPAYKDVAAKFAGQAGAEAELAQRIKNGSQGVWGPIPMPPNAVSDDEAQTLAKWVLSQK

Hydrogen-exchange rates were measured by monitoring the change in the TOCSY or 1D amide proton peak intensity as a function of time after exchanging a lyophilized sample into D2O. To initiate hydrogen exchange, a sample of oxidized Pa cyt c551 (3.0 mM protein, 5 times molar excess K3[Fe(CN)6], 50 mM NaPi pH 6.0) was lyophilized and dissolved in D2O. The pH* (uncorrected pH value) was immediately adjusted to 6.0 and data acquisition began 8 min after commencement of exchange. 1D (8 scans) and 2D TOCSY (32 scans) spectra were collected without solvent suppression using a Varian INOVA 500 MHz spectrometer at 300 K. Each TOCSY spectrum (4,096 ·256 points, with a 1.1-s recycle time) took about 5 h to acquire. TOCSY data were collected at 8, 13, 18, 25, 32, 37, 42, 96, and 317 h after initiation of exchange.