Inhibition of toxic IAPP amyloid by extracts of common fruits

The aggregation of the 37-amino acid polypeptide islet amyloid polypeptide (IAPP, amylin), as either insoluble amyloid or as small oligomers, appears to play a direct role in the death of pancreatic β-islet cells in type 2 diabetes. It is believed that inhibiting the aggregation of IAPP may slow down, if not prevent entirely, the progression of this disease. Extracts of 13 different common fruits were analyzed for their ability to prevent the aggregation of amyloidogenic IAPP. Thioflavin T binding, immuno-detection and circular dichroism assays were performed to test the in vitro inhibitory potential of each extract. Atomic force microscopy was used to visualize the formation of amyloid fibrils with and without each fruit extract. Finally, extracts were tested for their ability to protect living mammalian cells from the toxic effects of amyloid IAPP. Several fruits showed substantial ability to inhibit IAPP aggregation and protect living cells from toxic IAPP amyloid

Axiomes de rationalité en contexte d’incertitude

Le principe de la maximisation de l’utilité espérée s’est imposé comme le principal paradigme de la décision en contexte d’incertitude. Ce principe repose sur une axiomatique controversée. Les axiomes litigieux sont l’axiome de substitution de Marschak et l’axiome d’indépendance de Savage. Le but de cette communication est de faire ressortir, d’une part, le caractère non axiomatique des prescriptions de Marschak et de Savage et, d’autre part, de montrer par une démarche par l’absurde qu’il peut être coûteux de ne pas agir conformément à ces prescriptions. Finalement, je vais proposer de nouveaux axiomes qui, par un processus déductif, conduiront à un théorème de substitution dont on pourra également déduire le principe de maximisation de l’utilité espérée.The Maximum Expected Utility criterion has become the main paradigm of decision-making under uncertainty. This criterion is based on an axiomatic that is not unanimously accepted. The axioms under attack are Marschak's substitution axiom and Savage's independence axiom. The purpose of this paper is, on one hand, to bring into evidence the non-axiomatic nature of Marschak's and Savage's propositions and, on the other hand, to show that violations of these propositions lead to contradictions. New axioms will be proposed which by means of a deductive process lead to a theorem of substitution from which the Maximum Expected Utility criterion can be derived

Stably folded de novo proteins from a designed combinatorial library

Binary patterning of polar and nonpolar amino acids has been used as the key design feature for constructing large combinatorial libraries of de novo proteins. Each position in a binary patterned sequence is designed explicitly to be either polar or nonpolar; however, the precise identities of these amino acids are varied extensively. The combinatorial underpinnings of the binary code strategy preclude explicit design of particular side chains at specified positions. Therefore, packing interactions cannot be specified a priori. To assess whether the binary code strategy can nonetheless produce well-folded de novo proteins, we constructed a second-generation library based upon a new structural scaffold designed to fold into 102-residue four-helix bundles. Characterization of five proteins chosen arbitrarily from this new library revealed that (1) all are α-helical and quite stable; (2) four of the five contain an abundance of tertiary interactions indicative of well-ordered structures; and (3) one protein forms a well-folded structure with native-like features. The proteins from this new 102-residue library are substantially more stable and dramatically more native-like than those from an earlier binary patterned library of 74-residue sequences. These findings demonstrate that chain length is a crucial determinant of structural order in libraries of de novo four-helix bundles. Moreover, these results show that the binary code strategy - if applied to an appropriately designed structural scaffold - can generate large collections of stably folded and/or native-like proteins

Au collégial, l'engagement de l'étudiant dans son projet de formation : une responsabilité partagée avec les acteurs de son collège - Avis à la Ministre de l’éducation, du loisir et du sport

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