Quasi-mirror image

Each diastereoisomer can be isolated in a pure optically active form. They display quasi mirror image circular dichroism curves which illustrates the enantiomeric relationship between the tantalum asymmetric centers. 

Under most operating conditions a RFR eventually converges to a symmetric single-period operation so that the concentrations and temperature profiles after one flow reversal are a mirror image of those after the previous flow reversal. However, a cooled RFR may attain, under certain conditions, states with more complex periodicity, that is, states with period w > 1, nonsymmetric states and even complex quasi-periodic and chaotic states. 

Many proteases (such as a-chymotrypsin and subtilisin) and pig liver esterase exhibit a stereochemical preference opposite to that of lipases. This is because the catalytic triad of lipases and proteases - where the X-ray stmcture is known -has been found to be arranged in a mirror-image orientation [360]. Thus, the stereochemical outcome of an asymmetric hydrolysis can often be directed by choosing a hydrolase from a different class [361-364]. Scheme 2.50 depicts the quasi-enantiomeric oxy-anion transition-state intermediates during hydrolysis of a sec-alcohol ester catalyzed by Candida rugosa lipase (PDB entry Icrl) and the protease subtilisin (PDB entry Isbn). While the nucleophilic Ser-residues approach from the back, both His are located at the inside, with the oxy-anions pointing outside. Both active sites have limited space for one of the large and... 

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