The expression library was created from Φ24B::Kan DNA The rabbit

The expression library was created from Φ24B::Kan DNA. The rabbit antisera were depleted of antibodies reactive to E. coli proteins by a series of adsorptions to naïve MC1061 whole cells

and cellular lysate, and to BL21-AI + pET30c (empty vector) whole cells and cellular lysate. The depleted antisera were compared to undepleted antisera by western blot. Adsorptions were repeated until no bands were detectable by western blot probing of 6 μg of naïve MC1061 proteins. Peptide expression library construction Semi-confluent plaque assay plates [18] were overlaid with 3 ml SM buffer (100 mM NaCl, 8 mM MgSO4, 50 mM Tris-HCl, pH 7.5) and incubated at 4°C for 16 h, with gentle agitation. The SM buffer and top agar were transferred to separate 50 ml centrifuge tubes that were vortexed with 10% (v/v) fresh SM buffer and subjected selleck products to centrifugation at 10,000 g for 10 min. The supernatant selleck screening library was pooled and 30 μl of chloroform were added to each 10 ml of buffer. DNase (5 μg ml-1) and RNase (1 mg ml-1) were added, and the samples were incubated at 37°C for 1 h. PEG 8000 (33% [w/v]) was added, and the samples were incubated on ice for 30 min. Precipitated phage particles were harvested by centrifugation for 10 min at 10,000 g, and the

pellets were resuspended in 500 μl SM buffer per 30 ml starting volume. Samples were treated with DNase and RNase, as before. Phage DNA was purified by phenol:chloroform:isoamyl alcohol extraction and isopropanol precipitation [49] and resuspended in 100 μl ddH2O. The Φ24B DNA (15 μg ml-1 BCKDHA in TE) was fragmented using a HydroShear (GeneMachines, MI, USA), at speed code 6 for 30 cycles, followed by 30 cycles at speed code 2. DNA of the required size range (300-900 bp) was isolated by gel purification. pET30c plasmid (EMD Biosciences) DNA was digested with EcoR V and dephosphorylated with calf intestinal phosphatase (New England Biolabs) according to the selleckchem manufacturer’s recommendations. The size fractionated Φ24B DNA fragments were cloned into the prepared pET30c DNA (50 ng) vector in a molar ratio of 25:1 (insert to vector). Chemically competent BL21-AI

expression host cells (Invitrogen) were transformed with the plasmid DNA according to the manufacturer’s recommendations. Primary screening Transformed BL21-AI cells were plated onto LBKan plates and incubated at 37°C (11 h). Nitrocellulose membrane (0.2 μm pore size, BioTraceTM) was laid onto the top of each plate for approximately 1 min. The membranes were transferred colony-side up to LBKan agar plates supplemented with arabinose (0.2%) and IPTG (1 mM), and incubated at 37°C for 3 h. The master plates were incubated for a further 3 – 5 h at 37°C, until the colonies reached a diameter of 1-2 mm. The membranes were lifted from the agar plates and placed on chloroform-saturated filter paper, colony-side down, for 1 min, after which the chloroform was allowed to evaporate completely.

Comments are closed.