Determination of T. thermophilus HB27 NP oligomeric state by analytical ultracentrifugation. (A) TtPNPI, 0.35 mg/ml in 50 mM sodium phosphate (pH 7.0) at 20°C, 50,000 × g. (B) TtPNPII, 0.22 mg/ml in 50 mM sodium phosphate (pH 7.0) at 20°C, 50,000 × g. (C) TtPyNP, 0.53 mg/ml in 50 mM sodium phosphate (pH 7.0) at 20°C, 50,000 × g.