Check out the search on
enzyme
Shows new feature that I have never seen before. Look like the Question and Answer or Define, but different looking.

Screenshot? More description?

For [enzyme] I get a segment of results from [enzymes] too. Which is a feature Google has had in place a while.

Screen dumb, look here:
http://www.flickr.com/photos/erikhoy/162406952/
First, a box with two results that look like Q&A
Second, a box with two results on enzymes
Third the ordinary result list

Yes, this is a bit older, it's a kind of results clustering/ alternative results suggestion happening for some searches...