Figure 5: Negative image of an ethidium bromide-stained perpendicular DGGE separation pattern of PCR-amplified [NiFe] hydrogenase gene fragments from D. vulgaris BCMPS82obtained with primer pair Hyd1FHyd5R without GC clamp and with GC clamp. The fragment without GC clamp shows no stable melting behavior; it falls apart in two single-stranded molecules at high denaturant concentrations.