Controlled Assembly of Macromolecular β-Sheet Fibrils

Construction of functional molecular devices by directed assembly processes is one of the main challenges in the field of nanotechnology. Many approaches to this challenge use biological assembly as a source of inspiration for the build up of new materials with controlled organization at the nanoscale. In particular, the self-assembly properties of β-sheet peptides have been used in the design of supramolecular materials, such as tapes, nanotubes, and fibrils

Recent developments in genetics and medically assisted reproduction : from research to clinical applications

Two leading European professional societies, the European Society of Human Genetics and the European Society for Human Reproduction and Embryology, have worked together since 2004 to evaluate the impact of fast research advances at the interface of assisted reproduction and genetics, including their application into clinical practice. In September 2016, the expert panel met for the third time. The topics discussed highlighted important issues covering the impacts of expanded carrier screening, direct-to-consumer genetic testing, voiding of the presumed anonymity of gamete donors by advanced genetic testing, advances in the research of genetic causes underlying male and female infertility, utilisation of massively parallel sequencing in preimplantation genetic testing and non-invasive prenatal screening, mitochondrial replacement in human oocytes, and additionally, issues related to cross-generational epigenetic inheritance following IVF and germline genome editing. The resulting paper represents a consensus of both professional societies involved.Peer reviewe

Fibril formation by triblock copolymers of silklike beta-sheet polypeptides and poly(ethylene glycol)”, Macromolecules 2006

ABSTRACT: A series of ABA triblock copolymers consisting of a central -sheet polypeptide block and poly-(ethylene glycol) (PEG) end blocks were constructed in order to investigate the effect of PEG chain length on assembly behavior. The polypeptide block, consisting of tandem repeats of -(AG) 3 EG-(A ) alanine, G ) glycine, and E ) glutamic acid), was prepared by E. coli expression and subsequently conjugated via two flanking cysteine residues to maleimide-functionalized PEGs of various chain length. Infrared spectroscopy showed that no major effect of PEG chain length on polypeptide folding occurred. With atomic force microscopy a fibrillar microstructure was observed for all conjugates, with fibrillar heights of ∼2 nm. Only at the highest molecular weight of PEG (5000 g/mol) could an influence on assembly be noticed by the appearance of shorter fibers when compared to the hybrid block copolymers containing the lower molecular weight PEG chains. It can be concluded that this class of peptide-based materials is well capable of fibril formation in the -sheet stacking direction, whereas the PEG chains prevent their further side-to-side aggregation without interfering strongly with the desired -sheet interactions

Influence of π-π Stacking on the self-assembly and coiling of multi-chromophoric polymers based on perylenebis(dicarboximides): an AFM study

The assembly behavior at surfaces of very stiff polyisocyanopeptides (PICs) functionalized with semiconducting perylenebis(dicarboximide) (PDI) side chains has been investigated by atomic force microscopy. These multi-chromophoric arrays are unique as they combine an ultra-stiff central polymer main-chain scaffold upon which the PDI chromophores can self-organize through π-π stacking, making them interesting and versatile building blocks for nanoelectronics. In this paper we compare three PIC derivatives featuring different side groups: M1 - no chromophores, M2 - chromophores capable of π-π stacking, and M3 - chromophores where the stacking is hindered by the presence of bulky substituents in the bay area of the PDI. The effect of the different side functionalizations on the macromolecule assembly at surfaces was compared by studying the morphology and aggregation tendency of all three polymers when adsorbed on silicon, mica and graphite substrates. Making use of nano-manipulation of these functional rods with the AFM tip gave insight into the polymer structure and its coiling behaviour

High Shape Persistence in Single Polymer Chains Rigidified with Lateral Hydrogen Bonded Networks

Exploiting tapping mode-scanning force microscopy (TM-SFM), we characterized single polymeric chains of poly(isocyanodipeptides) (PICs) equilibrated in quasi two-dimensions on the basal plane of mica surfaces. While the average contour length L of an acid-catalyzed PIC bearing L-alanine- D-alanine methyl ester groups was as high as 5.3 m, the corresponding Ni-catalyzed product exhibited an L of 70 nm. With a newly devised method based on the statistical analysis of the curvature of polymeric chains on a length scale up to about 100 nm from SFM images, we determined their persistence length l p . The measured value of l p ) 76 ( 6 nm for both products, independent of the contour length, indicates that the single polymer molecules are very rigid, i.e., even more rigid than the double-stranded DNA. Thi

Improved Performance of Perylene-Based Photovoltaic Cells Using Polyisocyanopeptide Arrays

Photovoltaic devices incorporating perylene-substituted polyisocyanide materials have been demonstrated, using blend systems with polythiophene- and polyfluorene-based conjugated polymers. Prototypical structures with nominal (1:1) blend weight ratios of the polyisocyanide with poly(3-hexylthiophene) (P3HT) and poly(9,9'-dioctylfluorene-co-bis(N,N'-(4-butylphenyl))-bis(N,N'- phenyl)-1,4-phenyldiamine) (PFB) readily showed an order of magnitude improvement in power conversion efficiency, as compared to analogous blend architectures using a perylene (PDI) monomer, whereas the performance of strongly phase-separated F8BT (poly(9,9- dioctylfluorene-co-benzothidiazole) blend devices showed no such improvement. We propose that the use of polyisocyanide chains as a molecular template offers a method by which the morphology and connectivity of photovoltaic blends can be modified and enhanced