25 to 0.5 M imidazole in a buffer containing 8 M urea, 20 mM triethanolamine, pH8, 500 mM NaCl. Fractions containing the recombinant protein in large quantities without contaminants were pooled and dialyzed against an ion exchange buffer (6 M urea, 20 mM triethanolamine, pH8) overnight using a nitrocellulose dialysis membrane (Spectra/Por®membrane

kit, http://​www.​spectrumlabs.​com) before loading onto a HiTrap ion exchange Q column (GE Healthcare). The proteins were eluted by applying selleck chemicals a gradient of 0 to 1 M NaCl in ion exchange buffer. The fractions containing the recombinant proteins with a high degree of purity were pooled and dialyzed against a storage buffer (6 M urea, 20 mM triethanolamine, pH8, 300 mM NaCl, 5 mM EDTA).

The protein concentration was determined by the Lowry method [43]. The fractions were separated by 12.5% SDS-PAGE and the purity of purified recombinant proteins was estimated by densitometry (Quantity one software, GS 800 densitometer, Bio-Rad). The purified CBL-0137 cell line proteins were see more instantaneously used for ELISA analysis, the proteins were then conserved no longer than one month in storage buffer. ELISAs with purified recombinant proteins rAtpD, rP1-C and commercial Ani Labsystems kit Serum samples collected from children and adult patients with M. pneumoniae RTIs and from healthy blood donors were screened for anti-M. pneumoniae IgM, IgA and IgG antibodies by in-house ELISAs with the rP1-C and rAtpD proteins. Preadsorption of IgG rheumatoid factor was performed before each IgM ELISA test. The purified proteins were diluted by successive steps in PBS to avoid potentially damaging crystallisation of the urea in our ELISA washer automates. No precipitation of proteins was observed. Control ELISA tests were performed at different D-malate dehydrogenase urea concentrations ranging from 8 M to 0.1 M. The reactivity of the two recombinant proteins was not affected by stepwise dilution as the variation of the ELISA values with control serum samples was insignificant. The 96-well Maxisorp microtitre EIA plates (Nunc) were coated in triplicate with

50 ng per well of rP1-C or rAtpD in PBS. The plates were incubated overnight at 4°C and blocked in 250 μl blocking buffer (4% bovine serum albumin in PBS with 5 mM EDTA) at 37°C for 1 h. After washing three times with PBS containing 0.05% Tween 20, the antigen-coated wells were incubated sequentially for 30 min at 37°C with 1:100-diluted test sera, along with 1:50,000 dilution of peroxidase-labelled goat anti-human IgM, or IgA, or a 1:200,000 dilution of peroxidase-labelled goat anti-human IgG (Pierce). Plates were washed three times with PBS containing 0.05% Tween 20 between incubations. The enzyme reaction was developed with 100 μl of TMB (tetramethylbenzidine) substrate (Medac) for 30 min at 37°C. The reaction was stopped by adding 100 μl of 2 M H2SO4. The plates were read by photometric reading at 450 nm using an Opsys MR microplate reader (Dynex).