Measurement of GTPase activity of Ras following modification with PAM and photoirradiation
The isomerization of PAM-Ras modified with PAM as stated above "Modification of the cysteine residue in the core nucleotidebinding motif by using PAM" was performed at 0°C in modification buffer using UV light irradiation (Black-ray lamp, 366 nm, 16 W, UVP Inc., San Gabriel, CA, USA) for induction of the cis state for 3 min and using Vis light irradiation (Fluorescent lamp 27 W, FML27EX-N, Mitsubishi Inc., JP) of the trans state for 10 min and then repeated. The GTPase activity of PAM-Ras was measured at 25°C in modification buffer as stated above "GTPase activity of Ras".
Measurement of nucleotide exchange of Ras induced by GEF
The GDP dissociation rate was estimated using the fluorescently labeled GDP analog NBD-GDP. To the complex of 1 μM PAM-

Ras/NBD-GDP or PAM-Ras/NBD-GDP/GEF (SOS-505) in 120 mM
Tris-HCl (pH 7.5) with 2 mM MgCl 2 , 100 μM GTP was added, and the decrease in fluorescence was monitored at 25°C with an F-2500 spectrofluorometer (Hitachi, Tokyo, Japan). The data were fitted to a single exponential curve by using GraphPad Prism (GraphPad Software, La Jolla, CA, USA), which was used to comprehensive curve fitting the scientific data, from which the rate constants were calculated.

### Language ###
English

### Assessment ###
The text contains technical parameters about light exposure, specifically the duration of UV light irradiation.

### Query ###
Tell me how long UV exposure lasts when studying Ras proteins with PAM.
Tell me how long UV exposure lasts when studying Ras proteins with PAM.