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Exploring the Folding and Aggregation Mechanisms of Amyloid-Forming Peptides by Computer Simulations
Published in Gilles Grateau, Robert A. Kyle, Martha Skinner, Amyloid and Amyloidosis, 2004
Sébastien. Santini, Guang-Hong Wei, Normand Mousseau, Philippe Derreumaux
Analysis of the lowest-energy structures generated by all ART simulations shows several interesting features. Firstly, although the antiparallel beta-sheet arrangement is the most stable structure for the dimer and the trimer, in agreement with the NMR solid state of the fibril Aβ16-22 at neutral pH (4), several hydrogen-bond patterns with similar free energies exist (see the results on the dimer in Figure 1). This indicates that full structural order in the fibrils requires larger aggregates. Secondly, a parallel beta-sheet structure with low free energy is possible for the dimer, and mixed antiparallel-parallel organizations are also possible for the trimer. This result is significant because it helps clarify the dependency of beta-sheet registries on pH conditions (8). Thirdly, the folding pathways do not require obligatory α-helical intermediates. This finding indicates that destabilization of α-helical inter-mediates is unlikely to abolish oligomerization of full-length Aβ peptides. Finally, our simulations also emphasize the crucial role of the reptation move of one strand of the beta-sheet with respect to the others during the assembly process. Again, this is consistent with recent isotope-edited infrared spectroscopy analysis on the prion peptide spanning residues 109-122 (9).
Elements of Polymer Science
Published in E. Desmond Goddard, James V. Gruber, Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
E. Desmond Goddard, James V. Gruber
the chain is assumed to be contained in a hypothetical tube placed in the network. The “knots” in the network are seen as obstacles around which the chain must “wriggle” during translation. Two types of motions can be envisaged: (1) conformational changes within the confines of the tube; and (2) reptation, a snake-like motion that translates the chain within the tube until it finally escapes at the tube end (Fig. 8). The theory of reptation has been applied with large success to develop theories describing the dynamics and viscoelastic properties of entangled polymers.
Microencapsulation of reactive isocyanates for application in self-healing materials: a review
Published in Journal of Microencapsulation, 2021
Amanda N. B. Santos, Demetrio J. dos Santos, Danilo J. Carastan
Healing process could be trigged by damage propagation or different external stimuli such as electromagnetic radiation, heat, environmental changes and presence of atmospheric CO2 and H2O (Yang et al.2015). Important factors for microcapsule rupture are rigidity of shell and matrix, good adhesion between components, microcapsule size and concentration, rate and degree of polymerisation presented by released substance, shell thickness and core content (Yuan et al.2008). Self-healing process is understood by a sequence of five distinct events (Yang and Urban 2013, Yang et al.2015):Segmental surface rearrangements: damages will occur in a random way creating a complex damage morphology;Surface approach: for an elastic or diffusion recovery this step is critical to fill the voids;Wetting: formation of polymer-polymer or polymer-liquid interface;Diffusion: explained by the reptation model and the transition of a non-equilibrium to an equilibrium state;Randomisation: a sequence of reactions with reactive groups, such as –COOH, –NH2, –OH, –SH, present in the matrix.
Surgical applications of intracorporal tissue adhesive agents: current evidence and future development
Published in Expert Review of Medical Devices, 2020
Nicholas Gillman, David Lloyd, Randy Bindra, Rui Ruan, Minghao Zheng
Chain entanglement refers to a polymers ability to tangle with other polymer chains. The force of adhesion/cohesion between polymers is highly determined by the length of the polymer chain, known as the reptation model [24]. Position-dependent chain motion toward the chain ends also influences the confinement of the polymers [25]. Increasing the flexibility of a polymer chain allows for greater interpenetration and entanglement [26].