The purity of Xcn1 was determined according to the
method of Huang (Huang et al.
2005
). The pH of the cell-
free supernatant was adjusted to 3.0 with oxalic acid, and
then adjusted to 6.0 with NaOH. After removing sediment,
the supernatant was loaded onto a X-5 macroporous resin
column (100 cm
9
8 cm, Nankai University Chemical
Factory) at a flow rate of 2.0 mL/min and eluted with 30%
acetone containing 0.01 NH
4
Cl.
Eluate was concentrated
with a vacuum rotary evaporator and subsequently loaded
onto a 110 cation exchange chromatography column and
eluted with 0.2 M NH
4
Cl. Further purification was carried
out on a CM-Sephadex-C-25 weak acid cation exchange
resin (Pharmacia), and the bound fraction was eluted with
0.1 M NH
4
Cl. Active fractions containing Xcn1 were col-
lected and the purity was determined using HPLC on a
reversed-phase C
18
column (Waters 2695 system). Five
microliters of sample were injected into a column (2.1
9
150 mm), eluted with acetonitrile-0.1% TFA (10:90) at a
flow rate of 0.3 mL/min, and monitored at 312 nm