Zinc Metal Ion Affected the Structural Stability of Amyloid-Like Nanofibrils

Synthetic peptides that self-assemble into well-defined structures with a cross-β arrangement are called amyloid-like fibrils. Amyloids are associated with a list of disorders and neuro-degenerative diseases, such as Alzheimer's and Parkinson`s disease. We previously showed that amyloid-like nanofibrils with a repeating motif “IHIH” were functional fibrils. They were able to bind a metal ion through imidazole moieties and mimic the native carbonic anhydrase enzyme by hydrolysing the CO2 molecule. Thus, these synthetic amyloid fibrils were suggest-ed to be good candidates to moderate and update the modern enzymatic molecules. This study aims to shed a light on the stability of these amyloid nanofibrils over a study period of 25 days, in the presence/absence of a metal ion. The work continued for approximately 7 months in the Biochemistry department, School of Life Sciences at the University of Sussex in the United Kingdom. A set of designed peptides with a repeating motif “IHIH” were ex-plored, based on some structural studies. Short and long peptides with free ends as well as closed ends were investigated. Peptides allowed to self-assemble with and without a metal ion (zinc) were then examined using circular dichroism, fluorimetry and electron microscopy for structural biophysical analysis. Regardless of the metal ion contribution, peptides showed stable secondary structures with a -sheet conformation for the incubation time of 25 days. Their morphologies did not appear to change over time. However, the presence of a zinc ion has an effect on the secondary structure of the mature fibrils. Results indicated that fibrils grown with the zinc ion have a significantly higher propensity to form -sheets secondary structures during incubation time. The presence of a zinc ion also affected the dimensions of the amyloid-like fibrils by the end of the study course, at which point they significantly re-duced. This effect of zinc ion on synthetic amyloid fibrils has not been previously reported. The stabilities of the zinc-nanofibrils point to their potential for use in modifying or updating the enzyme-mimic analytical reactions. The effect of adding zinc on the fibrillation seems to be crucial. Although it apparently improved the -sheet assembly, it affected the width/length of the synthetic amyloids. This effect could be promising toward reducing the generation of amyloid fibrils and ultimately understanding the pathogenesis of Alzheimer disease

The diversity and utility of amyloid fibrils formed by short amyloidogenic peptides

Amyloidogenic peptides are well known for their involvement in diseases such as type 2 diabetes and Alzheimer's disease. However, more recently, amyloid fibrils have been shown to provide scaffolding and protection as functional materials in a range of organisms from bacteria to humans. These roles highlight the incredible tensile strength of the cross-β amyloid architecture. Many amino acid sequences are able to self-assemble to form amyloid with a cross-β core. Here we describe our recent advances in understanding how sequence contributes to amyloidogenicity and structure. For example, we describe penta- and hexapeptides that assemble to form different morphologies; a 12mer peptide that forms fibrous crystals; and an eight-residue peptide originating from α-synuclein that has the ability to form nanotubes. This work provides a wide range of peptides that may be exploited as fibrous bionanomaterials. These fibrils provide a scaffold upon which functional groups may be added, or templated assembly may be performed

Identifying the coiled-coil triple helix structure of β-peptide nanofibers at atomic resolution

Peptide self-assembly represents a powerful bottom-up approach to the fabrication of new nanomaterials. β3-peptides are non-natural peptides composed entirely of β-amino acids, which have an extra methylene in the backbone and we reported the first fibers derived from the self-assembly of β3-peptides that adopt unique 14-helical structures. β3-peptide assemblies represent a class of stable nanomaterials that can be used to generate bio- and magneto-responsive materials with proteolytic stability. However, the three-dimensional structure of many of these materials remains unknown. In order to develop structure-based criteria for the design of new β3-peptide-based biomaterials with tailored function, we investigated the structure of a tri-β3-peptide nanoassembly by molecular dynamics simulations and X-ray fiber diffraction analysis. Diffraction data was collected from aligned fibrils formed by Ac-β3[LIA] in water and used to inform and validate the model structure. Models with threefold radial symmetry resulted in stable fibers with a triple-helical coiled-coil motif and measurable helical pitch and periodicity. The fiber models revealed a hydrophobic core and twist along the fiber axis arising from a maximization of contacts between hydrophobic groups of adjacent tripeptides on the solvent-exposed fiber surface. These atomic structures of macro-scale fibers derived from β3-peptide-based materials provide valuable insight into the effects of the geometric placement of the side-chains and the influence of solvent on the core fiber structure which is perpetuated in the superstructure morphology

Characteristics of the fission fragments induced by the 129Xe + natSn reactions at E = 8–15A MeV

The study of nuclear multifragmentation is important for understanding the reaction mechanisms in heavy-ion collisions. In the present work, we study the nuclear reaction 129Xe + natSn in the energy range E = 8 to 15 AMeV. This experiment was performed at GANIL with the multidetector INDRA. We study the charge distributions produced in this reaction, which are broad and cover a large atomic number range. By using the data of this experiment, we identify four channels differing by the number of fragments: 1, 2, 3 and 4 fragments. In this contribution we will show a method to reconstruct the average size and excitation energy of the primary fission fragments, before their decay. The method employed is based on the fragment-light charged particles relative velocity correlation functions. Preliminary results will be presented

Chemically and thermally stable silica nanowires with a β-sheet peptide core for bionanotechnology

Background: A series of amyloidogenic peptides based on the sequence KFFEAAAKKFFE template the silica precursor, tetraethyl orthosilicate to form silica-nanowires containing a cross-β peptide core. Results: Investigation of the stability of these fibres reveals that the silica layers protect the silica-nanowires allowing them to maintain their shape and physical and chemical properties after incubation with organic solvents such as 2-propanol, ethanol, and acetonitrile, as well as in a strong acidic solution at pH 1.5. Furthermore, these nanowires were thermally stable in an aqueous solution when heated up to 70 °C, and upon autoclaving. They also preserved their conformation following incubation up to 4 weeks under these harsh conditions, and showed exceptionally high physical stability up to 1000 °C after ageing for 12 months. We show that they maintain their β-sheet peptide core even after harsh treatment by confirming the β-sheet content using Fourier transform infrared spectra. The silica nanowires show significantly higher chemical and thermal stability compared to the unsiliconised fibrils. Conclusions: The notable chemical and thermal stability of these silica nanowires points to their potential for use in microelectromechanics processes or fabrication for nanotechnological devices

Transition of nano-architectures through self-assembly of lipidated β3-tripeptide foldamers

β3-peptides consisting exclusively of β3-amino acids adopt a variety of non-natural helical structures and can self-assemble into well-defined hierarchical structures by axial head-to-tail self-assembly resulting in fibrous materials of varying sizes and shapes. To allow control of fiber morphology, a lipid moiety was introduced within a tri-β3-peptide sequence at each of the three amino acid positions and the N-terminus to gain finer control over the lateral assembly of fibers. Depending on the position of the lipid, the self-assembled structures formed either twisted ribbon-like fibers or distinctive multilaminar nanobelts. The nanobelt structures were comprised of multiple layers of peptide fibrils as revealed by puncturing the surface of the nanobelts with an AFM probe. This stacking phenomenon was completely inhibited through changes in pH, indicating that the layer stacking was mediated by electrostatic interactions. Thus, the present study is the first to show controlled self-assembly of these fibrous structures, which is governed by the location of the acyl chain in combination with the 3-point H-bonding motif. Overall, the results demonstrate that the nanostructures formed by the β3-tripeptide foldamers can be tuned via sequential lipidation of N-acetyl β3-tripeptides which control the lateral interactions between peptide fibrils and provide defined structures with a greater homogeneous population

The ASY-EOS experiment at GSI: investigating the symmetry energy at supra-saturation densities

The elliptic-flow ratio of neutrons with respect to protons in reactions of neutron rich heavy-ions systems at intermediate energies has been proposed as an observable sensitive to the strength of the symmetry term in the nuclear Equation Of State (EOS) at supra-saturation densities. The recent results obtained from the existing FOPI/LAND data for $^{197}$Au+$^{197}$Au collisions at 400 MeV/nucleon in comparison with the UrQMD model allowed a first estimate of the symmetry term of the EOS but suffer from a considerable statistical uncertainty. In order to obtain an improved data set for Au+Au collisions and to extend the study to other systems, a new experiment was carried out at the GSI laboratory by the ASY-EOS collaboration in May 2011.Comment: Talk given by P. Russotto at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS

eHealth and mHealth initiatives in Bangladesh: A scoping study

BACKGROUND: The health system of Bangladesh is haunted by challenges of accessibility and affordability. Despite impressive gains in many health indicators, recent evidence has raised concerns regarding the utilization, quality and equity of healthcare. In the context of new and unfamiliar public health challenges including high population density and rapid urbanization, eHealth and mHealth are being promoted as a route to cost-effective, equitable and quality healthcare in Bangladesh. The aim of this paper is to highlight such initiatives and understand their true potential. METHODS: This scoping study applies a combination of research tools to explore 26 eHealth and mHealth initiatives in Bangladesh. A screening matrix was developed by modifying the framework of Arksey & O’Malley, further complemented by case study and SWOT analysis to identify common traits among the selected interventions. The WHO health system building blocks approach was then used for thematic analysis of these traits. RESULTS: Findings suggest that most eHealth and mHealth initiatives have proliferated within the private sector, using mobile phones. The most common initiatives include tele-consultation, prescription and referral. While a minority of projects have a monitoring and evaluation framework, less than a quarter have undertaken evaluation. Most of the initiatives use a health management information system (HMIS) to monitor implementation. However, these do not provide for effective sharing of information and interconnectedness among the various actors. There are extremely few individuals with eHealth training in Bangladesh and there is a strong demand for capacity building and experience sharing, especially for implementation and policy making. There is also a lack of research evidence on how to design interventions to meet the needs of the population and on potential benefits. CONCLUSION: This study concludes that Bangladesh needs considerable preparation and planning to sustain eHealth and mHealth initiatives successfully. Additional formative and operational research is essential to explore the true potential of the technology. Frameworks for regulation in regards to eHealth governance should be the aim of future research on the integration of eHealth and mHealth into the Bangladesh health system.DFI

The metabolomics of asthma control: a promising link between genetics and disease

Short-acting β agonists (e.g., albuterol) are the most commonly used medications for asthma, a disease that affects over 300 million people in the world. Metabolomic profiling of asthmatics taking β agonists presents a new and promising resource for identifying the molecular determinants of asthma control. The objective is to identify novel genetic and biochemical predictors of asthma control using an integrative “omics” approach. We generated lipidomic data by liquid chromatography tandem mass spectrometry (LC-MS), ­ using plasma samples from 20 individuals with asthma. The outcome of interest was a binary indicator of asthma control defined by the use of albuterol inhalers in the preceding week. We integrated metabolomic data with genome-wide genotype, gene expression, and methylation data of this cohort to identify genomic and molecular indicators of asthma control. A Conditional Gaussian Bayesian Network (CGBN) was generated using the strongest predictors from each of these analyses. Integrative and metabolic pathway over-representation analyses (ORA) identified enrichment of known biological pathways within the strongest molecular determinants. Of the 64 metabolites measured, 32 had known identities. The CGBN model based on four SNPs (rs9522789, rs7147228, rs2701423, rs759582) and two metabolites—monoHETE_0863 and sphingosine-1-phosphate (S1P) could predict asthma control with an AUC of 95%. Integrative ORA identified 17 significantly enriched pathways related to cellular immune response, interferon signaling, and cytokine-related signaling, for which arachidonic acid, PGE2 and S1P, in addition to six genes (CHN1, PRKCE, GNA12, OASL, OAS1, and IFIT3) appeared to drive the pathway results. Of these predictors, S1P, GNA12, and PRKCE were enriched in the results from integrative and metabolic ORAs. Through an integrative analysis of metabolomic, genomic, and methylation data from a small cohort of asthmatics, we implicate altered metabolic pathways, related to sphingolipid metabolism, in asthma control. These results provide insight into the pathophysiology of asthma control