[KLUG Members] Problem with launching applications

[greenproc]

My problem is launching gui applications from a 'sudo su' root shell.

Synaptic fails with:

(synaptic:22507): Gtk-WARNING **: cannot open display:
debaser:/home/user# synaptic

(synaptic:22508): Gtk-WARNING **: cannot open display:
debaser:/home/user# synaptic

(synaptic:22509): Gtk-WARNING **: cannot open display:
debaser:/home/user# synaptic

K3b fails with:

debaser:/home/user# k3b
k3b: cannot connect to X server

How would one begin troubleshooting this type of problem?  I am able to
launch both synaptic and k3b by using the gnome gui -- they prompt me
for my root password and everything works fine.  But not from within a
'sudo su' root shell.

Thank you in advance for helping someone that isn't sure where to start
here <g>