Results of chemical cross-linking, ultracentrifugation and gel filtration experiments of SSB proteins. A: The results of chemical cross-linking experiments using 0.5% (v/v) glutaraldehyde with the SSB proteins under study, for 15 min at 25°C (lanes 2) and non-cross-linked samples (lanes 1). The fractions were analyzed by SDS-PAGE. B: Sedimentation analysis of the psychrophilic SSB proteins, PhaSSB, EcoSSB and standard proteins. 50 μl of 300 μM SSBs and standard proteins were centrifuged in linear 15 to 30% (w/v) glycerol gradients, as described in the Methods section. Lane M: Unstained Protein Weight Marker (Fermentas, Lithuania), with the molecular mass of proteins marked. Lane 1–19: fraction number. The fractions with proteins were analyzed by SDS-PAGE. The fractions at which the maximal amount of protein appears are shown by arrows. The standard proteins used are CA, carbonic anhydrase (29 kDa); BSA, bovine serum albumin (66 kDa); AD, alcohol dehydrogenase (150 kDa), and BA, β-amylase (200 kDa). C: Analytical gel filtration of the psychrophilic SSB proteins under study. A standard linear regression curve is shown. It was generated by plotting the log of the molecular mass of the calibration proteins against their retention times [min]. The calibration proteins include β-amylase (200 kDa), alcohol dehydrogenase (150 kDa), bovine albumin (66 kDa) and carbonic anhydrase (29 kDa).
Nowak et al. BMC Microbiology 2014 14:91 doi:10.1186/1471-2180-14-91