Samples
containing cells were cleaned by centrifugation at 12000 g for15 min and then 0.22 mm filtered prior to analysis. The HPLC
system used was an Agilent 1260 Infinity equipped with a G1311C
quat pump, G1329B autosampler, G1316A column compartment
and G1314C variable wavelength detector. The column was a
Phenomenex Jupiter 5u C18 300A with dimensions of 250 6
4.6 mm65 mm. For analysis of cell suspensions the mobile phase
was 75% acetonitrile: 25% 10 mM K2HPO, and for supernatants
the mobile phase was 80% acetonitrile: 20% 5 mM K2HPO4/
5 mM H2SO4. All samples were run isocratically with a flow rate
of 1 ml/min. The sample size was 5 mL and all measurements
were made at a wavelength of 210 nm, with degradation expressed
as a percentage of the control. All analysis was carried out in
duplicate and was conducted at least weekly for up to 63 days