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. 2012 Jun 29;7(6):e40027. doi: 10.1371/journal.pone.0040027

Table 1. SAXS analysis of eAPP fragments and their complexes.

Protein Peptide Dmax (Å) Rg (Å) MWcalc/MWseq
TRX-eAPP290–624 -na- 150 41 2.0
TRX-eAPP290–624 Aβ11-17 130 38 1.2
TRX-eAPP290–624 Aβ 1-28 140 42 1.5
TRX-eAPP290–624 APP319-335 140 41 1.3
TRX-eAPP290–624 7-kDa Aβ1-40 160 40 1.1
TRX-eAPP290–624 20-kDa Aβ1-42 160 43 2.5
eAPP230–624 -na- 150 44 2.0
eAPP230–624 RERMS 130 39 1.8
eAPP230–624 Aβ 1-28 170 46 0.9
eAPP230–624 7-kDa Aβ1-40 180 49 1.2
eAPP230–624 20-kDa Aβ1-42 170 46 2.6
MBP-eAPP230–624 -na- 190 55 2.0
MBP-eAPP230–624 2% DMSO 180 54 2.0
MBP-eAPP230–624 1,8-ANS 190 63 1.9
MBP-eAPP230–624 Sulfiram 170 53 1.7
MBP-eAPP230–624 Disulfiram 160 51 1.5
MBP-eAPP230–624 Aβ10-20 160 51 1.3
MBP-eAPP230–624 Aβ5-14 180 54 1.6
MBP-eAPP230–624 Aβ12-24 180 54 1.8
MBP-eAPP230–624 Aβ1-28 180 54 1.2
MBP-eAPP230–624 7-kDa Aβ1-40 210 63 1.1
MBP-eAPP230–624 20-kDa Aβ1-42 210 58 2.2
The maximum estimated error in the radius of gyration (R g) is ±2 Å. The maximum estimated error in maximum dimension (Dmax) is ±10 Å. Both values were calculated with the program GNOM [31]. The relative mass was calculated as the ratio of the apparent mass of the protein (MWcalc) to the expected mass derived from the protein sequence (MWseq). The molecular weight derived from the protein sequence is 52-kDa for TRX-eAPP290–624, 45-kDa for eAPP230–624, and 90-kDa for MBP-eAPP230–624. For globular, non-interacting proteins, the apparent mass can be estimated by comparing the extrapolated scattering of the sample at zero scattering angle (I(0)) to that of the reference protein albumin and the eAPP fragment dimer
graphic file with name pone.0040027.e004.jpg
where subscripts un and ref refer to the sample and the reference protein [56]. The error is the calculated mass is primarily due to the uncertainty in the estimation of the concentrations. The maximum error was determined experimentally by replicates of within a much larger set of experiments [18] to be ±0.2, where the maximum error determines the range of values for which p<0.05. Monomeric proteins with 20–30% of their residues in random coil conformation, as expected for monomeric APP, have relative mass estimates around 1.351.