Trehalose is a simple head-to-head dimer of glucose:
Like a lot of sugars, it holds onto water like crazy; some plants use it as a protectant in dry conditions.
Molecular biologists also use it in PCR; apparently, it stabilizes the enzyme, while destabilizing the dsDNA produced by the reaction.

Molecules: You'd better learn to live with them.
Comments
I think you should check your stereochemistry. The ring on the right looks like L-glucose to me... looks like its wrong on Wikipedia too if thats where you got the structure.
Posted by: Handles | June 6, 2007 3:02 AM
Looks OK to me on 2nd glance. Remember, they're both alpha-, so one will look a little wonky...
Posted by: Molecule of the Day | June 6, 2007 6:10 PM
Try building a molecular model of one ring and superimposing it on the other. They should match; they dont.
Posted by: Handles | June 6, 2007 6:44 PM
My mistake, thanks for being insistent about it. Fixed.
Posted by: Molecule of the Day | June 6, 2007 7:15 PM
Carbohydrates are tricksy. I recently spotted 3 or 4 similar errors in the online catalog of a fairly major chemical supplier (all fixed now). Buyer beware.
Posted by: Handles | June 6, 2007 9:01 PM
What's the origin of the name of this carbohydrate? Trehalose, sounds like three halos, but there are really only two ;-) I have to assume it's not related to psicose although all these sugars are going to my head
db
Posted by: David Bradley | June 7, 2007 3:52 AM