Various techniques for statistical analysis of the structure of fitness landscapes have been proposed. An important feature of these techniques is that they study the ruggedness of landscapes by measuring their correlation characteristics. This paper proposes a new information analysis of fitness landscapes. The underlying idea is to consider a fitness landscape as an ensemble of objects that are related to the fitness of neighboring points. Three information characteristics of the ensemble are defined and studied. They are termed: information content, partial information content, and information stability. The information characteristics of a range of landscapes with known correlation features are analyzed in an attempt to reveal the advantages of the information analysis. We show that the proposed analysis is an appropriate tool for investigating the structure of fitness landscapes.

To exploit the enzymatic method for the synthesis of β-hydroxy-α-amino acids, the genes coding for the Escherichia coli l-threonine aldolase (LTA; EC 2.1.2.1) and Xanthomonus oryzae d-threonine aldolase (DTA) were cloned and overexpressed in E. coli through primer-directed polymerase chain reactions. The purified recombinant enzymes were studied with respect to kinetics, specificity, stability, additive requirement, temperature profile, and pH dependency. DTA requires magnesium ion as a cofactor, while LTA needs no metal ions. These enzymes work well in the presence of DMSO with concentration up to 40%, and DMSO-induced rate acceleration of LTA-catalyzed reaction was observed. Both enzymes use pyridoxal phosphate coenzyme to activate glycine to react with a wide range of aldehydes. LTA gave erythro-β-hydroxy-α-l-amino acids with aliphatic aldehydes and the threo isomer with aromatic aldehydes as kinetically controlled products. On the other hand, DTA formed threo-β-hydroxy-α-d-amino acids as kinetically controlled products with aliphatic and aromatic aldehydes but the diastereoselectivity was lower than that of LTA. Under optimal conditions, several β-hydroxy-α-amino acid derivatives (3-hydroxyleucines, γ-benzyloxythreonines, γ-benzyloxymethylthreonines, and polyoxamic acids) have been stereoselectively synthesized on preparative scales using these enzymes. Also, the tandem use of DTA and phosphatases has made possible the synthesis and separation of d-allo-threonine phosphate and d-threonine.

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