[organicconversationpiece]

Im in general chemistry 1, and im trying to solve a chemistry problem that isn't related to my coursework. at first i tried solving it by using the Louis dot formal charge method, but this molecule is far more complicated then any molecule ive worked on in class.

im trying to understand whether or not Arginine has formed a salt bridge with an oxygen (the oxygen seems to be connected to a carbon that is connected to a oxygen and hydrogen). i cant figure out how to upload pictures on this site, it would be much easier to describe if i could show you the image.

so basically, could you tell me a method for determining if somethings formed a salt bridge. i know that it involves two charged molecules coming together, but it also has to do with where they are bonded. The best way i can think to solve this problem is looking at the formal charge of each atom in the molecule, but i dont even know the overall charge of arginine.

-i thank you for your imput

[Yggdrasil]

Are you talking about something like this, a salt bridge between the guanidinium group of argenine and a carboxylate (COO^-) group?

http://commons.wikimedia.org/wiki/File:Arginine_Aspartic_Acid_salt_bridge.png

The main requirement for a salt bridge is one positively charged species (in this case the arginine side chain) and one negatively charged species.  If the arginine is interacting with a negatively charged group, this should count as a salt bridge.  If it is interacting with a group that is not negatively charged, it would not count as a salt bridge, though other interactions (for example, hydrogen bonding interactions) could still be occurring.