Take the 2-minute tour ×
Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. It's 100% free, no registration required.

I'm reading some text (purchase request) that has the following line in it.

(-)-Norepinephrine

What does the minus sign mean in front that is in parenthesis? Is this some kind of standard way of describing charge of the molecule or something? Or is this someone's way of representing something else? Or does this mean nothing?

share|improve this question
add comment

1 Answer

up vote 2 down vote accepted

The minus sign in parentheses here indicates the optical rotation, (+) means the molecule rotates linear polarized light clockwise, (-) means it rotates counterclockwise. Typically you would also write exactly which stereoisomer is meant (R or S), which is generally the more useful information.

The following are all valid names for the natural stereoisomer of norepinephrine:

  • D-norepinephrine
  • D-(-)-norepinephrine
  • (R)-norepinephrine
  • (R)-(-)-norepinephrine

I'd recommend that you take a look at the concept of Chirality if you're not already familiar with it.

share|improve this answer
    
Sir, thank you very much. –  mj_ Jan 10 at 18:11
    
And they have the article dextrorotation and levorotation as well. –  Jeppe Stig Nielsen Jan 11 at 20:58
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.