Addition/Correction pubs.acs.org/ac
Correction to Empirical Correction for Differences in Chemical Exchange Rates in Hydrogen Exchange-Mass Spectrometry Measurements Ronald T. Toth, IV, Brittney J. Mills, Sangeeta B. Joshi, Reza Esfandiary, Steven M. Bishop, C. Russell Middaugh, David B. Volkin,* and David D. Weis* Anal Chem. 2017, 89, 8931−8941. DOI: 10.1021/acs.analchem.7b01396 During the revision of the original manuscript, the meanings of subscripts a and b were interchanged to improve readability by making b the baseline condition. Regrettably, some of the text, tables, equations, and figures were not fully updated to match the exchange of subscripts. Although the results are not affected, the error led to a confusing presentation in the paper. A full list of the corrections is provided below. Equations 5 and 9 should both be teq,b = taχab
Table 1. Chemical Exchange Correction Factor (χab) Values Determined Using HX of YPI
as it appears as equation S11 in the derivation in the Supporting Information. In the paragraph on page 8935 of the original manuscript beginning “The value of χab is determined...” the statement about χ should read (corrections noted in underline): From standard reference data for chemical exchange in model peptides,13 the rate constants for HX by the single amide hydrogen in YPI are ka = 8.2 × 10−3 s−1 and kb = 4.6 × 10−3 s−1, yielding an anticipated χab value of k 1.8 (i.e., 10ΔpH = ka = 10 0.25 = 1.78.)
5 mM CP buffer + additive
pD 6.5 + NaCla
pD 7.4 + NaClb
pD 7.4b
citrate-phosphate (5 mM) arginine (0.3 M) guanidine (0.3 M) mannitol (0.8 M) methionine (0.2 M) polysorbate 20 (0.05%) sulfate (0.3 M) thiocyanate (0.3 M) trehalose (0.4 M)
1.00 1.00 1.00 0.90 0.95 1.03 0.95 0.93 0.95
1.00 1.11 1.30 1.02 0.91 0.99 1.18 1.16 0.98
1.00 1.45 1.45 0.95 1.14 1.09 1.15 1.67 1.06
a
Chemical exchange correction factors were determined using 5 mM citrate-phosphate as the baseline condition at 100 s of HX labeling time using the data shown in Figure 1. bChemical exchange correction factors were determined using 5 mM citrate-phosphate as the baseline condition at 60 s of HX labeling time using the data shown in Figure 1.
b
In the paragraph following eq 8 on page 8935 of the original manuscript, the third sentence should read (correction is underlined): Here, 177 s/100 s = 1.8, matching the expected value exactly. In the legends of Figures 2 and 3, the notation for the open circle (○) should be Δma (ta) and for the filled circle (●), the legend should be Δmb. The last sentence of the Figure 2 caption should read (correction is underlined): The ratio of teq,b to ta is used to establish χab (here, χab = 177 s/100 s = 1.8) to correct for differences in chemical exchange between the conditions as shown in Figure 3. In the Figure 3 caption, the χ value should be 1.8. In the Figure 4 and 5 captions and in the section entitled “Testing the Hypothesis of Uniform Effects on Chemical Exchange” on page 8937 of the original manuscript, following the correction to eq 5, χ = 0.47 for urea and teq,b = 0.47 × 100 s = 47 s. The values shown in Table 1 are the reciprocals of the correct values because of the exchange of subscripts. The correct values for Table 1 are presented here.
© 2017 American Chemical Society
A
DOI: 10.1021/acs.analchem.7b04690 Anal. Chem. XXXX, XXX, XXX−XXX
