Is it possible to add classname to render array of node title using entity meta wrapper?

Question

I would like to know how to add a class name to node title by altering the render array. I examined the wrapper object

$wrapper = entity_metadata_wrapper('node', $nid)

by using

dpm($wrapper->getPropertyInfo())

and

debug($wrapper) 

but got not the smallest idea how to change the markup of the title, i.e. adding a class name.