Amino Acid Stereochemistry
||Chapter 27: Amino Acids, Peptides and Proteins
Fischer projections are commonly used to represent amino acids.
that Fischer projections are typically drawn with the longest chain oriented
and with the more
oxidised C at the top.
Stereochemistry was introduced in Chapter
7 and most recently revisited for carbohydrates
Here we will look at Fischer projections,
the D-, L- notation of amino acids
It's a good idea to review the basics of these topics if you do remember
them before continuing.
For the 20 α-amino acids that occur naturally
in proteins, if we focus on the α-center, a
chirality center, and draw the Fischer projection putting the -CO2H
group up, then the ammonium group, NH3+, will be on the left,
making it like L-glyceraldehyde where the -OH is on the left (review
Hence, we have the L-amino acids. You can check this out
using the 3D-JMOL images given below:
NOTE : Although only the L-amino acid series are incorporated into
natural proteins, the D-amino acids also occur naturally.
Which of the common amino acids is achiral ? ANSWER
R- and S- nomenclature is also used to
define configuration at chirality centers. Are the L-amino acids
R- or S- ? ANSWER