[MatthewP27!]

Hi,
I would like to ask you guys, why is disulfid cystein optically active? In my opinion it is meso-compound so it should be optically inactive, right?
Thx so much for help

[AWK]

Meso compound should show (R,S) configuration.
See:
https://en.wiki2.org/wiki/Tartaric_acid+Newton

[Babcock_Hall]

Of the 19 optically active, L-amino acids, 18 have the S configuration, but L-cysteine has the R configuration.  D-cysteine has the S configuration, and the drawing that was provided is labeled S and looks S in configuration to me.  Virtually all naturally occurring amino acids have the L-configuration, but a few D-amino acids are found in the bacterial cell wall, such as Ala and Glu.