FIG 5.

(a) MS spectrum at 2.54 min. The flow rate was maintained at 0.2 ml/min, and the mobile phase comprised water (A) and ACN (B) as follows: 0 min, 50% B; 0 to 10 min, 0% B; 10 to 20 min, 0% B; and 20 to 25 min, 50% B. The detecting wavelength was 225 nm, and the sample volume injected was 2 μl. The ESI source parameters were set as follows: positive ion mode, 3-kV spray voltage, 350°C capillary temperature, and nitrogen serving as both the sheath gas (35 U) and the auxiliary gas (10 U). (b) Proposed characteristic fragment ions of pyoverdines in P. chlororaphis YL-1. The matched b and y ions are indicated, as well as the corresponding mass error.