Multiple collections withdifferent users and access?

Hi all - I'm hoping to be able to use Omeka for a particular set of needs:

I want to have a general website for my institution's multiple collections of items. Each collection would have its own separate description and access controls. For example, a user could be authorized to access Collection A, but not necessarily Collection B or Collection C, all of which are located within a single installation of Omeka.

Is this possible?