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Alzheimer’s disease ranks as the third leading cause of death amongst adults over the age of 60 behind heart disease and cancer. The accumulation of amyloid plaque and neurofibrillary tangles causes the irreversible degradation and destruction of neurons that drastically shrinks brain tissue. Amyloid plaques are due to the buildup of insoluble amyloid beta (Aβ) fibrils formed from self-assembled propagation of peptides. Studies have shown that Aβ can take shape as soluble oligomers or insoluble fibrils with different morphologies. Aβ fibrils attain numerous structures, called polymorphs, both in patients’ brains and in vitro. Prior observations reveal that in agitated solutions the twofold polymorph of Aβ40 fibrils dominates, whereas the threefold polymorph of Aβ40 fibrils preferentially forms in the quiescent solutions. Previous atomic force microscopy (AFM) studies have demonstrated that the twofold symmetric Aβ40 polymorph grows steadily at broad ranges of peptide solution concentrations. It was also established that the fibril growth rate is determined by an activated complex, comprised by a peptide chain partially bound to the fibril tip and folded in a conformation distinct form that in the fibril bulk; the rearrangement of the intermediate configuration of the incoming peptide to the structure in the bulk fibril constitutes the transition state for growth [1]. We employ time-resolved in situ AFM to monitor the growth of seeds nucleated in quiescent solutions that belong to the threefold polymorph. We find that at low peptide concentrations, the fibrils growth bifurcates between two regimes. Growth either completely stalls or it proceeds at a rate, which is reproducible for the chosen solutions concentration. Similar observations of “stop and go” kinetics with other fibril-forming proteins have been attributed to two conformations of the soluble protein chains, growth complement, which supports growth, and growth incompetent, which caps the fibril tips and prevent association of growth competent chains. The recorded consistently steady growth of the two-fold Aβ40 fibrils, however, challenges the presence of growth-incompetent conformations in Aβ40 solutions. We put forth that stalled growth of the three-fold Aβ40 fibrils is due to an activated complex in which the incoming peptide folds into a conformation that cannot transform into the bulk fibril structure. The lifetime of that conformation of the activated complex defines the length of the period of stalled growth of the fibril. Our finding illuminates the complex interplay between fibril structures and the associated transition states during the growth of amyloid β fibrils.

ACCGE-22/OMVPE-20

BIFURCATED TRANSITION STATE FOR THE GROWTH OF THE THREEFOLD POLYMORPH OF AMYLOID BETA FIBRILS

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MATERIALS FOR HUMANITY (MH 21)

MH 21 is arranged around 6 themes that focus attention on pressing needs that should be addressed to enhance the well-being of communities and provide a forum for presenting breakthrough discoveries.

technical paper

The recent years have seen a revolution in the science and practice of crystal growth. Novel mechanisms of nucleation and growth have decoded mysteries that have puzzled the community for ages. Elaborate processes and advanced techniques have birthed materials with unprecedented properties and exciting applications. Rationales developed within the crystal growth realm have illuminated longstanding conundrums in geology, biology, and medicine. 

These jointly-held conferences are the premier forums to discuss the huge modern advances in all aspects of crystal growth, both in the bulk and as epitaxial films. We will continue the tradition of numerous ACCGE and OMVPE meetings and bring together the topmost experts in the field from industry, academia, and government laboratories. Joining the two conferences affords an exceptional opportunity to present and discuss original results and provides a venue for newcomers to embrace the hot, new advances in science and technology. Our format is designed to maximize interaction among leading specialists and the wider crystal growth community, with oral and poster sessions as well as plenary and invited speakers to provide a broad picture of the up-to-date developments in the field.

Abstract book available to download [here.](https://drive.google.com/file/d/1TgUeguUw-f4cb_Pi14Fu_QjaOCObfsN-/view?usp=sharing) 

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ACCGE's mission is to unify the global community of professionals engaged in research and clinical care for children with cerebrovascular diseases and chart a path forward for multinational, multidisciplinary effort.


High quality (hetero-) epitaxy usually needs mono-crystalline substrates. The typical substrates, often from binary materials like GaAs, InP, InAs, GaSb or even Ge, cause severe constraints due to the limited choice of lattice constants, thermal misfit or simply because of cost. In this session, solutions to overcome these limitations by either engineered substrates or lattice mismatched (metamorphic) epitaxy shall be discussed. Ideally the epitaxy layer or device quality for growth on such engineered substrates or metamorphic buffers is presented.

Lattice-mismatched epitaxy and alternative epitaxial substrates

III-V Nitride semiconductors have found widespread application in optoelectronics, power electronics, for detectors, and others. In this symposium, the growth of single crystal substrates, epitaxial layers and devices is discussed. The focus includes all aspects of fundamental and applied research related to nitride semiconductors.

III-V Wide Bandgap Nitride Semiconductors and Devices I : Crystal Growth and Epitaxy

III-V Nitride semiconductors have found widespread application in optoelectronics, power electronics, for detectors, and others. In this symposium, the growth of single crystal substrates, epitaxial layers and devices is discussed. The focus includes all aspects of fundamental and applied research related to nitride semiconductors.

Recordings will become available after the conference concludes.

III-V Wide Bandgap Nitride Semiconductors and Devices II : III-Nitride Properties and Characterization

This last decade, microfluidics technology has proved its efficiency to study crystallization fundamentals in chemistry and biology. This symposium will give an opportunity to the crystal growth community to present and discuss about the latest advances in this field of research. Presentations and discussions will focus on experimental and theoretical aspect of phase separation and crystal growth studies.

Nucleation in Microfluidics I

Nucleation in Microfluidics II

Research on the synthesis and the applications of various low-dimensional materials (0D, 1D, and layered 2D materials) are the themes of this symposium. These materials' unique properties, differing or exceeding those of their bulk crystal counterparts, are of potential scientific and technological importance. Materials of central importance to this symposium include 2D layered materials such as graphene, boron nitride, transition metal dichalcogenides and oxides, topological insulators superconductors, Xenes, etc., as well as their 0D and 1D counterparts and various heterostructural combinations. Due to widespread interest, a Special Topic Session on 2D magnetism is organized. Magnetism plays pivotal roles for a wide range of significant technologies such as data storage and biomedical imaging and continues to exhibit new phenomena in emerging materials at reduced dimensions. Magnetic 2D layered materials, experimentally discovered in 2017, are ideal platforms where both crystalline structural order and long-range magnetic order coexist in the atomic-thin region. The integration of 2D magnets with disparate electronic and photonic 2D materials opens up remarkable opportunities for designer quantum heterostructures with previously inaccessible magnetoelectric and magneto-optical properties. This Special Topic Session will collect abstracts on 2D magnet physics and modeling, various synthesis and characterization of 2D magnets and related heterostructures, and quantum transport and tunneling properties of 2D materials-based spintronic devices. This symposium aims to explore, through the contributions of leading researchers, new methodologies and breakthroughs in low-dimensional materials and identify constraining issues to future development.

BIFURCATED TRANSITION STATE FOR THE GROWTH OF THE THREEFOLD POLYMORPH OF AMYLOID BETA FIBRILS

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