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Figure 2 | Arthritis Res Ther

Figure 2

From: Electrophoretic characterization of species of fibronectin bearing sequences from the N-terminal heparin-binding domain in synovial fluid samples from patients with osteoarthritis and rheumatoid arthritis

Figure 2

~170-kDa N-terminal species of fibronectin (FN) in samples of synovial fluid (SF) from patients with osteoarthritis (OA) or rheumatoid arthritis (RA) bind to gelatin less avidly than do larger species bearing sequences from the N-terminal heparin-binding domain. Samples of SF from patients with OA (samples 1–3, 5, and 7–9 in the upper panels) or RA (samples 10–19 in the lower panels) were mixed with gelatin Sepharose beads, flow-through fractions were collected, and the beads were washed and boiled in reduced sample buffer to elute bound FN species. SF starting material ('S'), flow-through fractions ('F'), and bead eluates ('E') were then subjected to reduced 4–15% SDS–PAGE followed by Western blot analysis using mAb 1936 specific for an epitope in the N-terminal heparin-binding domain, followed by iodinated secondary antibodies. With the exception of RA SF samples 16 and 19, for which staining was restricted mainly to an ~200+-kDa band, the starting samples included two major species of FN, migrating at ~200+ and ~170 kDa, respectively. Whereas the ~200+-kDa band was stained more intensely than the ~170-kDa band in most samples, the flow-through fractions typically contained greater quantities of ~170- than ~200+-kDa species. Equivalent quantities of flow-through fractions and starting material were subjected to electrophoresis, whereas the volume of gelatin eluate was equivalent to four times the volume of starting material. OA samples 4 and 6 also exhibited lower '200+:170' ratios in flow-through fractions than in the starting fractions (not shown). The positions of molecular weight standards are denoted to the left of each panel, whereas the positions of the two predominant species of SF FN ('200+' and '170') are denoted by arrows to the left of the far left upper and lower panels only. The figure represents a composite derived from one autoradiagram, which was exposed overnight.

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