Host-defense peptides isolated from the skin secretions of the Northern red-legged frog Rana aurora aurora

Abstract Antimicrobial peptides in the skin secretions of anurans constitute a component of the innate immunity that protects the organism against invading pathogens. Four peptides with antimicrobial activity were isolated in high yield from norepinephrine-stimulated skin secretions of the Northern red-legged frog Rana aurora aurora and their primary structures determined. Ranatuerin-2AUa (GILSSFKGVAKGVAKNLAGKLLDELKCKITGC) showed potent growth-inhibitory activity against a range of Gram-positive and Gram-negative bacteria (minimum inhibitory concentrations , 20 mM) but low hemolytic activity against human erythrocytes (50% hemolysis at 290 mM). Brevinin-1AUa (FLPILAGLAAKLVPKVFCSITKKC) and brevinin-1AUb (FLPILAGLAANILPKVFCSITKKC) also showed potent antimicrobial activity but were strongly hemolytic (HC 50 , 10 mM). Temporin-1AUa (FLPIIGQLLSGLL.NH 2 ) atypically lacked a basic amino acid residue and showed very weak antimicrobial and hemolytic activity. Its biological function remains to be established. The primary structures of the antimicrobial peptides are consistent with a close phylogenetic relationship between R. aurora, Rana boylii and Rana luteiventris.

Retroactive causation and the temporal construction of news: contingency and necessity, content and form

This article affords particular attention to the relationship between memory, the narrativization of news and its linear construction, conceived as journalism’s ‘memory- work’. In elaborating upon this ‘work’, it is proposed that the Hegelian notion of retroactive causation (as used by Slavoj Žižek) can examine how analyses of news journalists ‘retroactively’ employ the past in the temporal construction of news. In fact, such retroactive (re)ordering directs attention to the ways in which journalists contingently select ‘a past’ to confer meaning on the present. With regard to current literature, it is noted that a retroactive analysis can highlight two important dialectics within the practice of news journalism: 1) the relation between contingency and necessity; and, 2) the relation between content and form. Indeed, it is argued that this theoretical account offers a novel approach to examining the significance of memory in news journalism as well as the inconsistencies which underscore journalism’s memory-work. It is in accordance with such inconsistency that broader reflections on time, temporality and our relations to the past can be made

Central Path Curvature and Iteration-Complexity for Redundant Klee—Minty Cubes

We consider a family of linear optimization problems over the n-dimensional Klee—Minty cube and show that the central path may visit all of its vertices in the same order as simplex methods do. This is achieved by carefully adding an exponential number of redundant constraints that forces the central path to take at least 2n − 2 sharp turns. This fact sug-gests that any feasible path-following interior-point method will take at least O(2n) iterations to solve this problem, whereas in practice typically only a few iterations (e.g., 50) suffices to obtain a high-quality solution. Thus, the construction potentially exhibits the worst-case iteration-complexity known to date which almost matches the theoretical iteration-complexity bound for this type of methods. In addition, this construction gives a counterexample to a conjecture that the total central path curvature is O(n)