This paper reports the synthesis of perfectly sequence defined, monodisperse diblock copolypeptides of a hydrophilic elastin-like polypeptide block and a hydrophobic resilin- like polypeptide block ...and characterization of their self-assembly as a function of structural parameters by light scattering, cryo-TEM, and small-angle neutron scattering. A subset of these diblock copolypeptides exhibit LCST and UCST phase behavior and self-assemble into spherical or cylindrical micelles. Their morphology is dictated by their chain length, degree of hydrophilicity and hydrophilic weight fraction of the ELP block. We find that: (1) independent of the length of the corona forming ELP block there is a minimum threshold in the length of the RLP block below which self-assembly does not occur, but that once that threshold is crossed, (2) the RLP block length is a unique molecular parameter to independently tune self-assembly; and (3) increasing the hydrophobicity of the corona-forming ELP drives a transition from spherical to cylindrical morphology. Unlike the self-assembly of purely ELP based block copolymers, the self-assembly of RLP-ELPs can be understood by simple principles of polymer physics relating hydrophilic weight fraction, polymer-polymer and polymer-solvent interactions to micellar morphology, which is important as it provides a route for the de novo design of desired nanoscale morphologies from first principles.
Understanding the pathogenicity of amyloid-beta (Aβ) peptides constitutes a major goal in research on Alzheimer’s disease (AD). One hypothesis entails that Aβ peptides induce uncontrolled, neurotoxic ...ion flux through cellular membranes. The exact biophysical mechanism of this ion flux is, however, a subject of an ongoing controversy which has attenuated progress toward understanding the importance of Aβ-induced ion flux in AD. The work presented here addresses two prevalent controversies regarding the nature of transmembrane ion flux induced by Αβ peptides. First, the results clarify that Αβ can induce stepwise ion flux across planar lipid bilayers as opposed to a gradual increase in transmembrane current; they show that the previously reported gradual thinning of membranes with concomitant increase in transmembrane current arises from residues of the solvent hexafluoroisopropanol, which is commonly used for the preparation of amyloid samples. Second, the results provide additional evidence suggesting that Aβ peptides can induce ion channel-like ion flux in cellular membranes that is independent from the postulated ability of Αβ to modulate intrinsic cellular ion channels or transporter proteins.
Robust high-throughput synthesis methods are needed to expand the repertoire of repetitive protein-polymers for different applications. To address this need, we developed a new method, overlap ...extension rolling circle amplification (OERCA), for the highly parallel synthesis of genes encoding repetitive protein-polymers. OERCA involves a single PCR-type reaction for the rolling circle amplification of a circular DNA template and simultaneous overlap extension by thermal cycling. We characterized the variables that control OERCA and demonstrated its superiority over existing methods, its robustness, high-throughput and versatility by synthesizing variants of elastin-like polypeptides (ELPs) and protease-responsive polymers of glucagon-like peptide-1 analogues. Despite the GC-rich, highly repetitive sequences of ELPs, we synthesized remarkably large genes without recursive ligation. OERCA also enabled us to discover 'smart' biopolymers that exhibit fully reversible thermally responsive behaviour. This powerful strategy generates libraries of repetitive genes over a wide and tunable range of molecular weights in a 'one-pot' parallel format.
Robust high-throughput synthesis methods are needed to expand the repertoire of repetitive protein-polymers for different applications. To address this need, we developed a new method, ...overlap-extension rolling circle amplification (OERCA), for the highly parallel synthesis of genes encoding repetitive protein-polymers. OERCA involves a single PCR-type reaction for the rolling circle amplification of a circular DNA template and simultaneous overlap extension by thermal cycling. We characterized the variables that control OERCA and demonstrated its superiority over existing methods, its robustness, throughput and versatility by synthesizing variants of elastin-like polypeptides (ELPs) and protease-responsive polymers of a glucagon-like peptide-1 analog. Despite the GC-rich, highly repetitive sequences of ELPs, we synthesized remarkably large genes without recursive ligation. OERCA also enabled us to discover “smart” biopolymers that exhibit fully reversible thermally responsive behavior. This powerful strategy generates libraries of repetitive genes over a wide and tunable range of molecular weights in a “one-pot” parallel format.
La medicina regenerativa busca desarrollar estrategias para promover la regeneración de tejidos dañados. El auge de esta área de investigación biomédica y su potencial para el tratamiento de una gran ...variedad de enfermedades-como las neurodegenerativas, hepáticas y cardiacas, o quemaduras de piel y otros traumas-, demanda un análisis continuo sobre el estado de las investigaciones actuales, su impacto, lo que se espera en los próximos años y los debates éticos asociados. Para responder éstas y otras preguntas, revisamos algunos de los avances más importantes ocurridos en año 2011 y consultamos la opinión de un experto en medicina regenerativa, el profesor Felipe Prósper Cardoso de la Universidad de Navarra en España. Si bien los avances han sido muy significativos en el laboratorio, especialmente en la derivación de células autólogas (diferenciadas o pluripotentes) y el desarrollo de biomateriales que facilitan y promueven la regeneración, la traslación clínica de las terapias de medicina regenerativa aún es incipiente y constituye un gran reto para investigadores en esta área.
PDF
