Synthesis and characterization of a new two photon excitable acid sphingomyelinase FRET probe

Recently, FRET probes for acid sphingomyelinase (ASM) have enabled the observation of enzyme activity in intact cells for the first time. Here we present an ASM FRET probe specifically optimized for 2-photon excitation. To facilitate probe characterization and comparison to the previous probe, we mixed the two intact probes with defined amounts of the probes' ceramide cleavage products and mounted them on lipid beads. Directly excited NBD FRET acceptor fluorescene proved to be a useful means of reference and showed that the new probe is brighter, albeit only moderately, than the previous one. The new probe was then used to detect inhibition by various ASM inhibitors microscopically for the first time. Also in cells, directly excited acceptor fluorescence proved to be a useful parameter in addition to FRET to visualize inhibition of ASM.

Colorimetric determination of cyclophosphamide and ifosphamide

A simple colorimetric method for the determination of cyclophosphamide and ifosphamide in pure and in dosage forms is suggested. It depends on the reaction of the secondary amino group in both, with nitrous acid, thus forming a nitroso derivative which can be measured at 325 nm for cyclophosphamide and 335 nm for ifosphamide. Beer's law is obeyed with concentrations from 20 to 90 micrograms ml-1 for cyclophosphamide and from 5 to 100 micrograms ml-1 for ifosphadmie, with repeatability of 99.83 +/- 0.256% and 99.72 +/- 0.649%, respectively. Application to different pharmaceutical preparations has shown no significant difference when compared with the B.P. 1988 method.