How apply jQuery functions after postbacking the page

I have a radtextbox in usercontrol for search  the items.to search i restrict the user to enter specified charecters only.for that i wrote the j query function.for the first request it is working perfectly.by entering and clicking the button.i'm doing postback only not entirley page load.for the entire page load.it's working.but for the postback requets it is not working..please help me.