Presocratic discourse in poetry and prose: The case of Empedocles and Anaxagoras

This paper explores the differences between poetry and prose in philosophical writing by examining two Pre-Socratic fragments, one in verse and one in prose, that express a very similar thought: Empedocles 59 B 17 Diels/Kranz and Anaxagoras 31 B 8 D./K. Although at first it might seem as though there is a simple division between Empedocles’ opaque and allusive hexameters and Anaxagoras’ sober prose, when we look in detail at the language used by the two authors, a close reading of the passages reveals a more complex picture. Both authors place rhetorical emphasis on their own role as innovator; Anaxagoras’ prose shows a careful attention to style and word choice no less than Empedocles’ poetry, and Empedocles’ poetry itself reflects the range of stylistic registers and types of material that hexameter could be used for in antiquity. There is no simple antithesis between prose style and hexametric poetry, and the words and stylistic devices an author chooses are constitutive of the thought he expresses.     

Kemp elimination catalysts by computational enzyme design

The design of new enzymes for reactions not catalysed by naturally occurring biocatalysts is a challenge for protein engineering and is a critical test of our understanding of enzyme catalysis. Here we describe the computational design of eight enzymes that use two different catalytic motifs to catalyse the Kemp elimination-a model reaction for proton transfer from carbon-with measured rate enhancements of up to 10(5) and multiple turnovers. Mutational analysis confirms that catalysis depends on the computationally designed active sites, and a high-resolution crystal structure suggests that the designs have close to atomic accuracy. Application of in vitro evolution to enhance the computational designs produced a >200-fold increase in k(cat)/K(m) (k(cat)/K(m) of 2,600 M(-1)s(-1) and k(cat)/k(uncat) of >10(6)). These results demonstrate the power of combining computational protein design with directed evolution for creating new enzymes, and we anticipate the creation of a wide range of useful new catalysts in the future.     

Activation and specificity of alkaline phosphatase of a mineralizing collagen-rich system

Alkaline phosphatase from tibia tendon of Meleagris gallopavo L. was highly purified. The enzyme activation by different ions was measured. Mg2+ showed a high activation with a broader spectrum of phosphomonoester hydrolization. The in vivo Mg2+ concentration was an optimum for in vitro activation.     

Activation and specificity of alkaline phosphatase of a mineralizing collagen-rich system

Summary Alkaline phosphatase from tibia tendon ofMeleagris gallopavo L. was highly purified. The enzyme activation by different ions was measured. Mg²⁺ showed a high activation with a broader spectrum of phosphomonoester hydrolization. The in vivo Mg²⁺ concentration was an optimum for in vitro activation.Dedicated to Prof. Dr. G. Pfefferkorn on the occasion of his 65^th birthday.We thank Deutsche Forschungsgemeinschaft for support.     

Enrichment of CO2 and magnesium in early stages of biomineralization

Summary Simultaneous topochemical analyses of calcium, magnesium, carbonate (as CO₂) and phosphorus in a mineralizing collagen rich system (turkey tibia tendon) showed a strong enrichment of Mg and CO₂ in the prestages of biomineralization.We thank the Deutsche Forschungsgemeinschaft for support and Mr E. Kalthoff for assistance.