Формирование и развитие человеческого капитала в Республике Беларусь

Материалы XX Междунар. науч.-техн. конф. студентов, аспирантов и молодых ученых, Гомель, 23–24 апр. 2020 г

Conjugated Polyelectrolytes in Interactions with Biomolecules for Supramolecular assembly and Sensing

Conjugated polyelectrolytes (CP) show interesting electrical and optical properties for organic electronics as well as for life science applications. Their possibilities of supramolecular assembly with nanowire like misfolded proteins, amyloids, as well as synthetic polypeptides or DNA forming conducting or luminescent nano composites is highly interesting as being a truly bottom up approach for fabrication of OLEDs, photovoltaic’s as well as logic devices. The conformation and aggregation dependent luminescence properties from the special class of CPs, Luminescent conjugated polyelectrolytes (LCP), have been utilised and developed as sensors to follow and study biomolecular interactions, DNA hybridisation, protein-protein interactions and staining of living cell cultures and tissue slides. In this thesis we are bringing the evolution a few steps further by applying new types of experimental techniques, such as light scattering and fluorescence correlation spectroscopy, combined with standard techniques as soft lithography and different spectroscopy techniques, to gain better knowledge of the optical behaviour of LCPs and their interactions with biomolecules. We explore the optical properties and vibronic transitions of LCPs; their ability of resonance energy transfer with LCPs indicating super lightning behaviour; the opposite fluorescence shift when interacting with α-helical rich polypeptides compared to earlier reports of interactions upon staining of β-rich amyloids; and the possibility of LCPs to influence protein aggregation as well as the possibility of fabricating biochips based on LCPs and soft lithography. Here we also show fundamental limitations to patterning using macromolecular fluids, of general relevance to soft lithography and nanoimprint lithography with low viscosity polymers

Interactions between a luminescent conjugated polyelectrolyte and amyloid fibrils investigated with flow linear dichroism spectroscopy

Luminescent conjugated polyelectrolytes (LCPs) have emerged as novel stains to detect and distinguish between various amyloidogenic species, including prefibrillar aggregates and mature fibril deposits, both in vitro and in histological tissue samples, offering advantages over traditional amyloid stains. We here use linear dichroism (LD) spectroscopy under shear alignment to characterize interactions between the LCP poly(3-thiophene acetic acid) (PTAA) and amyloid fibrils. The positive signature in the LD spectrum of amyloid-bound PTAA suggests that it binds in the grooves between adjacent protein side-chains in the amyloid fibril core, parallel to the fibril axis, similar to thioflavin-T and congo red. Moreover, using LD we record the absorption spectrum of amylokl-bound PTAA in isolation from free dye showing a red-shift by ca 30 nm compared to in solution. This has important implications for the use of PTAA as an amyloid probe in situ and in vitro and we demonstrate how to obtain optimal amyloid-specific fluorescence read-outs using PTAA. We use the shift in maximum absorption to estimate the fraction of bound PTAA at a given concentration. PTAA binding reaches saturation when added in 36 times excess and at this concentration the PTAA density is 4-5 monomer units per insulin monomer in the fibril. Finally, we demonstrate that changes in LD intensity can be related to alterations in persistence length of amyloid fibrils resulting from changes in solution conditions, showing that this technique is useful to assess macroscopic properties of these biopolymers. (C) 2011 Elsevier Inc. All rights reserved

Dark states in ionic oligothiophene bioprobes-evidence from fluorescence correlation spectroscopy and dynamic light scattering

Luminescent conjugated polyelectrolytes (LCPs) can upon interaction with biological macromolecules change their luminescent properties, and thereby serve as conformation- and interaction-sensitive biomolecular probes. However, to exploit this in a more quantitative manner, there is a need to better understand the photophysical processes involved. We report studies of the conjugated pentameric oligothiophene, derivative p-FTAA, which changes optical properties with different p-FTAA concentrations in aqueous buffers, and in a pH and oxygen saturation dependent manner. Using dynamic light scattering, luminescence spectroscopy and fluorescence correlation spectroscopy, we find evidence for a monomer dimer equilibrium, for the formation of large clusters of p-FTAA in aqueous environment, and can couple aggregation to changed emission properties of oligothiophenes. In addition, we observe the presence of at least two dark transient states, one presumably being a triplet state. Oxygen was found to statically quench the p-FTAA fluorescence but also to promote molecular fluorescence by quenching dark transient states of the p-FTAA molecules. Taken together, this study provides knowledge of fluorescence and photophysical features essential for applying p-FTAA and other oligothiophene derivatives for diagnostic purposes, including detection and staining of amyloid aggregates.Updated from "Manuscript" to "Published article". QC 20140707</p

Interactions between a luminescent conjugated oligoelectrolyte and insulin during early phases of amyloid formation

Folding of an amino acid polypeptide chain into its native three-dimensional protein is a delicate process. Misfolding may cause assembly of dysfunctional proteins leading to aggregated assemblies, in medicine denoted amyloids, causing Alzheimer’s, Parkinson and a number of other protein related diseases. Amyloids have also shown promising results as building blocks in organic electronic applications, associated to conjugated polymers. Luminescent conjugated oligo- and polythiophenes (LCPs) have been further developed for biosensor applications exhibiting good ability to discriminate and determine different types of amyloid enrichment in complex environments, such as in tissue sections. The nature of interaction between the amyloid assemblies and LCPs is still not fully understood. In this study we use steady-state fluorescence spectroscopy, dynamic light scattering, transmission electron microscopy and fluorescence correlation spectroscopy to follow the interplay between the anionic oligothiophene derivative 4',3'''-Bis-carboxymethyl-[2,2';5',2'';5'',2''';5''',2'''']quinque thiophene-5,5''''-dicarboxylic acid (p-FTAA), and prefibrillar protein assemblies present during the earlier stage of in vitro fibrillation of bovine insulin. Our findings confirm that p-FTAA interacts with pre-fibrillar species of insulin preceding the formation of mature insulin amyloid fibrils, and insights regarding the molecular interplay between p-FTAA and these species are provided.Funding Agencies|Swedish Science Council (VR)||Strategic Research Foundation (SSF) through the center for organic bioelectronics (OBOE)||Knut and Alice Wallenberg foundation|

Interactions between a luminescent conjugated oligoelectrolyte and insulin during early phases of amyloid formation

Folding of an amino acid polypeptide chain into its native three-dimensional protein is a delicate process. Misfolding may cause assembly of dysfunctional proteins leading to aggregated assemblies, in medicine denoted amyloids, causing Alzheimer’s, Parkinson and a number of other protein related diseases. Amyloids have also shown promising results as building blocks in organic electronic applications, associated to conjugated polymers. Luminescent conjugated oligo- and polythiophenes (LCPs) have been further developed for biosensor applications exhibiting good ability to discriminate and determine different types of amyloid enrichment in complex environments, such as in tissue sections. The nature of interaction between the amyloid assemblies and LCPs is still not fully understood. In this study we use steady-state fluorescence spectroscopy, dynamic light scattering, transmission electron microscopy and fluorescence correlation spectroscopy to follow the interplay between the anionic oligothiophene derivative 4',3'''-Bis-carboxymethyl-[2,2';5',2'';5'',2''';5''',2'''']quinque thiophene-5,5''''-dicarboxylic acid (p-FTAA), and prefibrillar protein assemblies present during the earlier stage of in vitro fibrillation of bovine insulin. Our findings confirm that p-FTAA interacts with pre-fibrillar species of insulin preceding the formation of mature insulin amyloid fibrils, and insights regarding the molecular interplay between p-FTAA and these species are provided.Funding Agencies|Swedish Science Council (VR)||Strategic Research Foundation (SSF) through the center for organic bioelectronics (OBOE)||Knut and Alice Wallenberg foundation|

Amyloid fibrils as dispersing agents for oligothiophenes: control of photophysical properties through nanoscale templating and flow induced fibril alignment

Herein we report that protein fibrils formed from aggregated proteins, so called amyloid fibrils, serve as an excellent dispersing agent for hydrophobic oligothiophenes such as alpha-sexithiophene (6T). Furthermore, the protein fibrils are capable of orienting 6T along the fibril long axis, as demonstrated by flow-aligned linear dichroism spectroscopy and polarized fluorescence microscopy. The materials are prepared by solid state mixing of 6T with a protein capable of self-assembly. This results in a water soluble composite material that upon heating in aqueous acid undergoes self-assembly into protein fibrils non-covalently functionalized with 6T, with a typical diameter of 5-10 nm and lengths in the micrometre range. The resulting aqueous fibril dispersions are a readily available source of oligothiophenes that can be processed from aqueous solvent, and we demonstrate the fabrication of macroscopic structures consisting of aligned 6T functionalized protein fibrils. Due to the fibril induced ordering of 6T these structures exhibit polarized light emission

Polypeptide-guided assembly of conducting polymer nanocomposites

A strategy for fabrication of electroactive nanocomposites with nanoscale organization, based on self-assembly, is reported. Gold nanoparticles are assembled by a polypeptide folding-dependent bridging. The polypeptides are further utilized to recruit and associate with a water soluble conducting polymer. The polymer is homogenously incorporated into the nanocomposite, forming conducting pathways which make the composite material highly conducting.Original Publication:Mahiar Hamedi, Jens Wigenius, Feng-i Tai, Per Björk and Daniel Aili, Polypeptide-guided assembly of conducting polymer nanocomposites, 2010, NANOSCALE, (2), 10, 2058-2061.http://dx.doi.org/10.1039/c0nr00299bCopyright: Royal Society of Chemistryhttp://www.rsc.org