aU24 protein that had been isolated from various E.coli cell strains was reconstituted in 10 mM Tris·HCl, 10 mM NaCl, 10 mM SDS, pH 7.5 and far-UV CD was run (260-195 nm) in the presence and absence of tris(2-carboxyethyl)phosphine (TCEP) reducing agent.
bFractions of secondary structure were determined by combining the software analysis results of the CONTIN/LL, SELCON3 and CDSSTR programs  using the SMP56 reference data set. Structural classes are given as: αR, regular α-helix; αD, distorted α-helix; βR, regular β-strand; βD, distorted β-strand; T, turns; U, unordered.
cNormalized Root-Mean-Square Deviation. NRMSD is defined as Σ[(θexp - θcal)2/(θexp)2]1/2, summed over all wavelengths, and where θexp and θcal are, respectively, the experimental ellipticities and ellipticities of the back-calculated spectra for the derived structure [27, 35]. It has been suggested  that experimental and calculated spectra are in good agreement if NRMSD < 0.1, are similar if 0.1 < NMRSD < 0.2, and are in poor agreement if NRMSD > 0.2.