Table 1.

Summary of molecular masses observed for Aβ (1–40) peptide under the indicated conditions

Sample	Number of runs	Observed molecular mass, Da*	Mass increase from protonated Aβ Da*	Mass increase after side-chain correction, Da*†
Protonated Aβ monomer or fibrils with protonated processing solvent	6	4,329.4  ± 0.1
Deuterated Aβ monomer with deuterated processing solvent	10	4,395.1  ± 0.2	65.8  ± 0.2	38.8  ± 0.2
Deuterated Aβ monomer with protonated processing solvent	41	4,361.7  ± 1.1	32.3  ± 1.1	27.3  ± 1.1
Deuterated Aβ fibrils with protonated processing solvent‡ (incubation time ∼15 h for deuteration)	34	4,345.7  ± 0.7	16.3  ± 0.7	11.3  ± 0.7
Deuterated Aβ fibrils with protonated processing solvent (incubation time ∼384 h for deuteration)	4	4,348.0  ± 0.2	18.6  ± 0.2	13.6  ± 0.2

^*Uncertainties represent the standard deviations of the mean of the indicated number of replicate runs. Data in this table may differ marginally from some data shown in the figures and text, which show individual, representative runs. 

^† Corrected for rapid back-exchange of labile protons (see text). 

^‡ Multiple deuterated samples prepared from four different fibril preparations were run multiple times.