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1.
Biomacromolecules ; 20(10): 3641-3647, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31418550

RESUMO

Consensus motifs for sequences of both crystallizable and amorphous blocks in silks and natural structural analogues of silks vary widely. To design novel silklike polypeptides, an important question is therefore how the nature of either the crystallizable or the amorphous block affects the self-assembly and resulting physical properties of silklike polypeptides. We address herein the influence of the amorphous block on the self-assembly of a silklike polypeptide that was previously designed to encapsulate single DNA molecules into rod-shaped viruslike particles. The polypeptide has a triblock architecture, with a long N-terminal amorphous block, a crystallizable midblock, and a C-terminal DNA-binding block. We compare the self-assembly behavior of a triblock with a very hydrophilic collagen-like amorphous block (GXaaYaa)132 to that of a triblock with a less hydrophilic elastin-like amorphous block (GSGVP)80. The amorphous blocks have similar lengths and both adopt a random coil structure in solution. Nevertheless, atomic force microscopy revealed significant differences in the self-assembly behavior of the triblocks. If collagen-like amorphous blocks are used, there is a clear distinction between very short polypeptide-only fibrils and much longer fibrils with encapsulated DNA. If elastin-like amorphous blocks are used, DNA is still encapsulated, but the polypeptide-only fibrils are now much longer and their size distribution partially overlaps with that of the encapsulated DNA fibrils. We attribute the difference to the more hydrophilic nature of the collagen-like amorphous block, which more strongly opposes the growth of polypeptide-only fibrils than the elastin-like amorphous blocks. Our work illustrates that differences in the chemical nature of amorphous blocks can strongly influence the self-assembly and hence the functionality of engineered silklike polypeptides.

2.
Nano Lett ; 19(8): 5746-5753, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31368710

RESUMO

While the structure of a multitude of viral particles has been resolved to atomistic detail, their assembly pathways remain largely elusive. Key unresolved issues are particle nucleation, particle growth, and the mode of genome compaction. These issues are difficult to address in bulk approaches and are effectively only accessible by the real-time tracking of assembly dynamics of individual particles. This we do here by studying the assembly into rod-shaped viruslike particles (VLPs) of artificial capsid polypeptides. Using fluorescence optical tweezers, we establish that small oligomers perform one-dimensional diffusion along the DNA. Larger oligomers are immobile and nucleate VLP growth. A multiplexed acoustic force spectroscopy approach reveals that DNA is compacted in regular steps, suggesting packaging via helical wrapping into a nucleocapsid. By reporting how real-time assembly tracking elucidates viral nucleation and growth principles, our work opens the door to a fundamental understanding of the complex assembly pathways of both VLPs and naturally evolved viruses.

3.
Chemistry ; 25(47): 11058-11065, 2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31150560

RESUMO

The self-assembly of protein polymers is a promising route to prepare sophisticated functional nanostructures. However, the interplay between protein self-assembly by itself and its co-assembly with a template is not well understood. Silk-based protein polymers that co-assemble with DNA to form rod-like artificial viruses are herein developed and the effects of silk block length, concentration, and temperature in the self-assembly of the proteins alone are characterized by using a combination of bulk dynamic light scattering (DLS) and single-molecule atomic force microscopy (AFM). Protein nanorods were slowly formed (up to hours) through the interaction of the silk-like blocks. The proteins present a silk-length dependent critical elongation concentration, and above it the amount and size of nanorods rapidly increase. Temperature-dependent light scattering data was adequately fitted into a cooperative model of nucleation-elongation. These results are also important to understand the self-assembly of designed viral coat proteins with DNA templates to form artificial virus-like particles and help us to define general guidelines to design proteins with the ability to precisely organize matter at the nanoscale.


Assuntos
Proteínas do Capsídeo/química , Nanotubos/química , Sequência de Aminoácidos , Proteínas do Capsídeo/metabolismo , Difusão Dinâmica da Luz , Cinética , Microscopia de Força Atômica , Temperatura Ambiente
4.
PLoS One ; 14(1): e0211059, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30682112

RESUMO

For polymer-particle composites, limited thermodynamic compatibility of polymers and particles often leads to poor dispersal and agglomeration of the particles in the matrix, which negatively impacts the mechanics of composites. To study the impact of particle compatibility in polymer matrices on the mechanical properties of composites, we here study composite silica- protein based hydrogels. The polymer used is a previously studied telechelic protein-based polymer with end groups that form triple helices, and the particles are silica nanoparticles that only weakly associate with the polymer matrix. At 1mM protein polymer, up to 7% of silica nanoparticles can be embedded in the hydrogel. At higher concentrations the system phase separates. Oscillatory rheology shows that at high frequencies the particles strengthen the gels by acting as short-lived multivalent cross-links, while at low frequencies, the particles reduce the gel strength, presumably by sequestering part of the protein polymers in such a way that they can no longer contribute to the network strength. As is generally observed for polymer/particle composites, shear-induced polymer desorption from the particles leads to a viscous dissipation that strongly increases with increasing particle concentration. While linear rheological properties as function of particle concentration provide no signals for an approaching phase separation, this is very different for the non-linear rheology, especially fracture. Strain-at-break decreases rapidly with increasing particle concentration and vanishes as the phase boundary is approached, suggesting that the interfaces between regions of high and low particle densities in composites close to phase separation provide easy fracture planes.


Assuntos
Hidrogéis/química , Nanopartículas/química , Proteínas/química , Dióxido de Silício/química , Reologia
5.
J Phys Chem Lett ; 10(3): 316-321, 2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30615463

RESUMO

Genetic profiling would benefit from linearization of ssDNA through the exposure of the unpaired bases to gene-targeting probes. This is compromised by ssDNA's high flexibility and tendency to form self-annealed structures. Here, we demonstrate that self-annealing can be avoided through controlled coating with a cationic-neutral diblock polypeptide copolymer. Coating does not preclude site-specific binding of fluorescence labeled oligonucleotides. Bottlebrush-coated ssDNA can be linearized by confinement inside a nanochannel or molecular combing. A stretch of 0.32 nm per nucleotide is achieved inside a channel with a cross-section of 100 nm and a 2-fold excess of polypeptide with respect to DNA charge. With combing, the complexes are stretched to a similar extent. Atomic force microscopy of dried complexes on silica revealed that the contour and persistence lengths are close to those of dsDNA in the B-form. Labeling is based on hybridization and not limited by restriction enzymes. Enzyme-free labeling offers new opportunities for the detection of specific sequences.


Assuntos
DNA de Cadeia Simples/química , Análise de Sequência de DNA , Benzoxazóis/química , DNA/química , DNA/metabolismo , Sondas de DNA/metabolismo , DNA de Cadeia Simples/metabolismo , Microscopia de Força Atômica , Desnaturação de Ácido Nucleico , Compostos de Quinolínio/química
6.
Macromol Rapid Commun ; : e1800284, 2018 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-30027644

RESUMO

Here, a means of controlling the assembly pathways of p-conjugated oligoelectrolytes into supramolecular fibers and microtubes is presented, and it is shown how the addition of small end-caps to well-defined and pH-responsive conjugated oligomers can alter the balance between repulsive and attractive supramolecular forces and enables control of the morphology of the hierarchical assembly process. The assembly stages from nuclei to protofibers are evidenced and a hypothesis on the mechanism of microtubes formation using a combination of analytical methods is provided, revealing different degrees of order at different scales along the structural hierarchy.

7.
Sci Rep ; 8(1): 11127, 2018 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-30042491

RESUMO

In order to study how acidic pro-peptides inhibit the antimicrobial activity of antimicrobial peptides, we introduce a simple model system, consisting of a 19 amino-acid long antimicrobial peptide, and an N-terminally attached, 10 amino-acid long acidic model pro-peptide. The antimicrobial peptide is a fragment of the crotalicidin peptide, a member of the cathelidin family, from rattlesnake venom. The model pro-peptide is a deca (glutamic acid). Attachment of the model pro-peptide only leads to a moderately large reduction in the binding to- and induced leakage of model liposomes, while the antimicrobial activity of the crotalicidin fragment is completely inhibited by attaching the model pro-peptide. Attaching the pro-peptide induces a conformational change to a more helical conformation, while there are no signs of intra- or intermolecular peptide complexation. We conclude that inhibition of antimicrobial activity by the model pro-peptide might be related to a conformational change induced by the pro-peptide domain, and that additional effects beyond induced changes in membrane activity must also be involved.

8.
Phys Rev E ; 97(3-1): 032501, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29776063

RESUMO

A self-consistent field analysis for tunable contributions to the persistence length of isolated semiflexible polymer chains including electrostatically driven coassembled deoxyribonucleic acid (DNA) bottlebrushes is presented. When a chain is charged, i.e., for polyelectrolytes, there is, in addition to an intrinsic rigidity, an electrostatic stiffening effect, because the electric double layer resists bending. For molecular bottlebrushes, there is an induced contribution due to the grafts. We explore cases beyond the classical phantom main-chain approximation and elaborate molecularly more realistic models where the backbone has a finite volume, which is necessary for treating coassembled bottlebrushes. We find that the way in which the linear charge density or the grafting density is regulated is important. Typically, the stiffening effect is reduced when there is freedom for these quantities to adapt to the curvature stresses. Electrostatically driven coassembled bottlebrushes, however, are relatively stiff because the chains have a low tendency to escape from the compressed regions and the electrostatic binding force is largest in the convex part. For coassembled bottlebrushes, the induced persistence length is a nonmonotonic function of the polymer concentration: For low polymer concentrations, the stiffening grows quadratically with coverage; for semidilute polymer concentrations, the brush chains retract and regain their Gaussian size. When doing so, they lose their induced persistence length contribution. Our results correlate well with observed physical characteristics of electrostatically driven coassembled DNA-bioengineered protein-polymer bottlebrushes.


Assuntos
Fenômenos Mecânicos , Eletricidade Estática , Modelos Moleculares
9.
Macromolecules ; 51(1): 204-212, 2018 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-29339838

RESUMO

As a model system to study the elasticity of bottle-brush polymers, we here introduce self-assembled DNA bottle brushes, consisting of a DNA main chain that can be very long and still of precisely defined length, and precisely monodisperse polypeptide side chains that are physically bound to the DNA main chains. Polypeptide side chains have a diblock architecture, where one block is a small archaeal nucleoid protein Sso7d that strongly binds to DNA. The other block is a net neutral, hydrophilic random coil polypeptide with a length of exactly 798 amino acids. Light scattering shows that for saturated brushes the grafting density is one side chain per 5.6 nm of DNA main chain. According to small-angle X-ray scattering, the brush diameter is D = 17 nm. By analyzing configurations of adsorbed DNA bottle brushes using AFM, we find that the effective persistence of the saturated DNA bottle brushes is Peff = 95 nm, but from force-extension curves of single DNA bottle brushes measured using optical tweezers we find Peff = 15 nm. The latter is equal to the value expected for DNA coated by the Sso7d binding block alone. The apparent discrepancy between the two measurements is rationalized in terms of the scale dependence of the bottle-brush elasticity using theory previously developed to analyze the scale-dependent electrostatic stiffening of DNA at low ionic strengths.

11.
Anal Chem ; 89(23): 12812-12820, 2017 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-29111679

RESUMO

Fluorescent nanodiamonds are gaining increasing attention as fluorescent labels in biology in view of the fact that they are essentially nontoxic, do not bleach, and can be used as nanoscale sensors for various physical and chemical properties. To fully realize the nanosensing potential of nanodiamonds in biological applications, two problems need to be addressed: their limited colloidal stability, especially in the presence of salts, and their limited ability to be taken up by cells. We show that the physical adsorption of a suitably designed recombinant polypeptide can address both the colloidal stability problem and the problem of the limited uptake of nanodiamonds by cells in a very straightforward way, while preserving both their spectroscopic properties and their excellent biocompatibility.

12.
Nucleic Acid Ther ; 27(3): 159-167, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28437166

RESUMO

RNA has enormous potential as a therapeutic, yet, the successful application depends on efficient delivery strategies. In this study, we demonstrate that a designed artificial viral coat protein, which self-assembles with DNA to form rod-shaped virus-like particles (VLPs), also encapsulates and protects mRNA encoding enhanced green fluorescent protein (EGFP) and luciferase, and yields cellular expression of these proteins. The artificial viral coat protein consists of an oligolysine (K12) for binding to the oligonucleotide, a silk protein-like midblock S10 = (GAGAGAGQ)10 that self-assembles into stiff rods, and a long hydrophilic random coil block C that shields the nucleic acid cargo from its environment. With mRNA, the C-S10-K12 protein coassembles to form rod-shaped VLPs each encapsulating about one to five mRNA molecules. Inside the rod-shaped VLPs, the mRNAs are protected against degradation by RNAses, and VLPs also maintain their shape following incubation with serum. Despite the lack of cationic surface charge, the mRNA VLPs transfect cells with both EGFP and luciferase, although with a much lower efficiency than obtained by a lipoplex transfection reagent. The VLPs have a negligible toxicity and minimal hemolytic activity. Our results demonstrate that VLPs yield efficient packaging and shielding of mRNA and create the basis for implementation of additional virus-like functionalities to improve transfection and cell specificity, such as targeting functionalities.


Assuntos
Proteínas do Capsídeo/química , RNA Mensageiro/administração & dosagem , RNA Mensageiro/química , Transfecção , Vacinas de Partículas Semelhantes a Vírus/química , Proteínas do Capsídeo/ultraestrutura , Sobrevivência Celular , Coloides , DNA/química , Corantes Fluorescentes/análise , Corantes Fluorescentes/química , Corantes Fluorescentes/metabolismo , Proteínas de Fluorescência Verde/análise , Proteínas de Fluorescência Verde/química , Proteínas de Fluorescência Verde/metabolismo , Células HEK293 , Células HeLa , Hemólise , Humanos , Luciferases/análise , Luciferases/química , Luciferases/metabolismo , Microscopia de Força Atômica , Nanomedicina/tendências , Estabilidade de RNA , Vacinas de Partículas Semelhantes a Vírus/ultraestrutura
13.
J Am Chem Soc ; 139(13): 4962-4968, 2017 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-28326772

RESUMO

The coassembly of well-defined biological nanostructures relies on a delicate balance between attractive and repulsive interactions between biomolecular building blocks. Viral capsids are a prototypical example, where coat proteins exhibit not only self-interactions but also interact with the cargo they encapsulate. In nature, the balance between antagonistic and synergistic interactions has evolved to avoid kinetic trapping and polymorphism. To date, it has remained a major challenge to experimentally disentangle the complex kinetic reaction pathways that underlie successful coassembly of biomolecular building blocks in a noninvasive approach with high temporal resolution. Here we show how macromolecular force sensors, acting as a genome proxy, allow us to probe the pathways through which a viromimetic protein forms capsids. We uncover the complex multistage process of capsid assembly, which involves recruitment and complexation, followed by allosteric growth of the proteinaceous coat. Under certain conditions, the single-genome particles condense into capsids containing multiple copies of the template. Finally, we derive a theoretical model that quantitatively describes the kinetics of recruitment and growth. These results shed new light on the origins of the pathway complexity in biomolecular coassembly.

14.
Colloids Surf B Biointerfaces ; 153: 199-207, 2017 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-28242373

RESUMO

Although multilayered emulsions have been related to reduced lipolysis, the involved interfacial phenomena have never been studied directly. In this work, we systematically built multilayers of whey protein and pectin, which we further subjected to digestive conditions, using two different techniques: droplet volume tensiometry to investigate interfacial rheology, and reflectometry to determine the amount of adsorbed material. Interfacial tension and dilatational rheology were linked to adsorption/desorption kinetics measured under static in vitro conditions. The interfacial tension and rheology of the multilayers was rather similar to those found for single whey protein layers, as well as their resistance to duodenal conditions and lipolytic components, which is explained by the rapid destabilisation of multilayers at neutral pH. Sequential adsorption of bile extract or lipase to pre-adsorbed films rapidly lowered the interfacial tension via co-adsorption and displacement, forming a viscoelastic film with low mechanical strength, and highly dynamic adsorption/desorption. When both were present, bile salts dominated the initial adsorption, followed by lipase co-adsorption and formation of lipolysis products that further lowered the interfacial tension, forming a complex interface (including biopolymers, bile salts, lipase, and lipolysis products), independent of pre-adsorbed biopolymer layers. Our study shows that the combination of drop volume tensiometry and reflectometry can be used to study complex interfacial behaviours under digestive conditions, which can lead to smart design of interfacial structures for controlled lipolysis in food emulsions.


Assuntos
Ácidos e Sais Biliares/metabolismo , Biopolímeros/metabolismo , Digestão , Lipase/metabolismo , Adsorção , Biopolímeros/química , Humanos , Concentração de Íons de Hidrogênio , Técnicas In Vitro , Cinética , Lipólise , Tamanho da Partícula , Reologia , Propriedades de Superfície
15.
ACS Nano ; 11(1): 831-842, 2017 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-28048935

RESUMO

Programmed molecular recognition is being developed for the bionanofabrication of mixed organic/inorganic supramolecular assemblies for applications in electronics, photonics, and medicine. For example, DNA-based nanotechnology seeks to exploit the easily programmed complementary base-pairing of DNA to direct assembly of complex, designed nanostructures. Optimal solution conditions for bionanofabrication, mimicking those of biological systems, may involve high concentrations of biomacromolecules (proteins, nucleic acids, etc.) and significant concentrations of various ions (Mg2+, Na+, Cl-, etc.). Given a desire to assemble diverse inorganic components (metallic nanoparticles, quantum dots, carbon nanostructures, etc.), it will be increasingly difficult to find solution conditions simultaneously compatible with all components. Frequently, the use of chemical surfactants is undesirable, leaving a need for the development of alternative strategies. Herein, we discuss the use of artificial, diblock polypeptides in the role of solution compatibilizing agents for molecular assembly. We describe the use of two distinct diblock polypeptides with affinity for DNA in the stabilization of DNA origami and DNA-functionalized gold nanoparticles (spheres and rods) in solution, protection of DNA from enzymatic degradation, as well as two 3D tetrahedral DNA origamis. We present initial data showing that the diblock polypeptides promote the formation in the solution of desired organic/inorganic assemblies.

16.
Crit Rev Food Sci Nutr ; 57(10): 2218-2244, 2017 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-26252442

RESUMO

The increasing prevalence of overweight and obesity requires new, effective prevention and treatment strategies. One approach to reduce energy intake is by developing novel foods with increased satiating properties, which may be accomplished by slowing down lipolysis to deliver substrates to the ileum, thereby enhancing natural gut-brain signaling pathways of satiety that are normally induced by meal intake. To develop slow release food additives, their processing in the gastrointestinal tract has to be understood; therefore, we start from a general description of the digestive system and relate that to in vitro modeling, satiety, and lipolytic mechanisms. The effects of physicochemical lipid composition, encapsulation matrix, and interfacial structure on lipolysis are emphasized. We give an overview of techniques and materials used, and discuss partitioning, which may be a key factor for encapsulation performance. Targeted release capsules that delay lipolysis form a real challenge because of the high efficiency of the digestive system; hardly any proof was found that intact orally ingested lipids can be released in the ileum and thereby induce satiety. We expect that this challenge could be tackled with structured o/w-emulsion-based systems that have some protection against lipase, e.g., by hindering bile salt adsorption and/or delaying lipase diffusion.


Assuntos
Gorduras na Dieta/administração & dosagem , Digestão , Regulação para Baixo , Alimentos Especializados , Lipólise , Modelos Biológicos , Sobrepeso/dietoterapia , Animais , Depressores do Apetite/administração & dosagem , Depressores do Apetite/metabolismo , Depressores do Apetite/uso terapêutico , Gorduras na Dieta/metabolismo , Gorduras na Dieta/uso terapêutico , Emulsões , Ingestão de Energia , Aditivos Alimentares/metabolismo , Aditivos Alimentares/uso terapêutico , Tecnologia de Alimentos/tendências , Humanos , Absorção Intestinal , Sobrepeso/metabolismo , Resposta de Saciedade
17.
ACS Nano ; 11(1): 144-152, 2017 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-27936577

RESUMO

Emerging DNA-based nanotechnologies would benefit from the ability to modulate the properties (e.g., solubility, melting temperature, chemical stability) of diverse DNA templates (single molecules or origami nanostructures) through controlled, self-assembling coatings. We here introduce a DNA coating agent, called C8-BSso7d, which binds to and coats with high specificity and affinity, individual DNA molecules as well as folded origami nanostructures. C8-BSso7d coats and protects without condensing, collapsing or destroying the spatial structure of the underlying DNA template. C8-BSso7d combines the specific nonelectrostatic DNA binding affinity of an archeal-derived DNA binding domain (Sso7d, 7 kDa) with a long hydrophilic random coil polypeptide (C8, 73 kDa), which provides colloidal stability (solubility) through formation of polymer brushes around the DNA templates. C8-BSso7d is produced recombinantly in yeast and has a precise (but engineerable) amino acid sequence of precise length. Using electrophoresis, AFM, and fluorescence microscopy we demonstrate protein coat formation with stiffening of one-dimensional templates (linear dsDNA, supercoiled dsDNA and circular ssDNA), as well as coat formation without any structural distortion or disruption of two-dimensional DNA origami template. Combining the programmability of DNA with the nonperturbing precise coating capability of the engineered protein C8-BSso7d holds promise for future applications such as the creation of DNA-protein hybrid networks, or the efficient transfection of individual DNA nanostructures into cells.

18.
Chemistry ; 23(2): 239-243, 2017 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-27727480

RESUMO

We investigate a new case of a self-assembly-stimulated self-assembly in which a triblock polypeptide is combined with a anionic coordination polymer of a dipicolinic acid bis-ligand, and d- or f- block metal ions like ZnII or EuIII . The polypeptide not only has a silk-like domain that can fold and stack, but also a C-terminal cationic sequence by which it can interact with the supramolecular (coordination) polyanion. In the presence of all three ingredients (polypeptide, bis-ligand, and metal ions), we observe the initiation and slow growth of well-defined metal-containing nanorods of up to 150 nm in length, proving that self-assembly of the polypeptide is triggered by the self-assembly of the coordination polyelectrolyte and vice versa. The particles, which have a striking resemblance to rod-like viruses, are stable up to 1.2 m NaCl, and can be made fluorescent when lanthanides like EuIII are used, showing the potential to exploit functional properties and applications of virus-like supramolecular structures.


Assuntos
Complexos de Coordenação/química , Európio/química , Nanotubos/química , Peptídeos/química , Polímeros/química , Zinco/química , Corantes Fluorescentes/química , Nanotubos/ultraestrutura , Vírus/química
19.
Biomacromolecules ; 17(12): 3893-3901, 2016 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-27768271

RESUMO

Previously, we developed triblock protein polymers that form fibrillar hydrogels at low protein polymer concentrations (denoted C2-SH48-C2). We here demonstrate that the structure of these hydrogels can be tuned via heterodimeric coiled coils that cross-link and bundle the self-assembled protein polymer fibrils. We fused well-characterized, 47 amino acids-long heterodimeric coiled coil "linkers" (DA or DB) to the C-terminus of the triblock polymer. The resulting C2-SH48-C2-DA and C2-SH48-C2-DB polymers, were successfully produced as secreted proteins in Pichia pastoris, with titers of purified protein in the order of g L-1 of clarified broth. Atomic force microscopy showed that fibrils formed by either C2-SH48-C2-DA or C2-SH48-C2-DB alone already displayed extensive bundling, apparently as a result of homotypic (DA/DA and DB/DB) interactions. For fibrils prepared from protein polymers having no linkers, plus a small fraction of polymers containing either DA or DB linkers, no cross-linking and bundling was observed. At these same low concentrations of linkers, fibrils containing both the DA and the DB linkers did show cross-linking and bundling as a consequence of heterodimer formation. This work shows that we can control the extent of bundling and cross-linking of supramolecular fibrils by varying the density of heterodimerizing coiled coils in the fibrils, which is promising for the further development of materials that mimic the extracellular matrix.


Assuntos
Reagentes para Ligações Cruzadas/química , Hidrogéis/química , Fragmentos de Peptídeos/química , Pichia/metabolismo , Polímeros/química , Proteínas/química , Proteínas Recombinantes/química , Fragmentos de Peptídeos/metabolismo , Pichia/crescimento & desenvolvimento , Polímeros/metabolismo , Engenharia de Proteínas , Estrutura Secundária de Proteína , Proteínas/metabolismo , Proteínas Recombinantes/metabolismo
20.
Soft Matter ; 12(38): 8004-14, 2016 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-27604959

RESUMO

A recently introduced DNA-bottlebrush system, which is formed by the co-assembly of DNA with a genetically engineered cationic polymer-like protein, is subjected to osmotic stress conditions. We measured the inter-DNA distances by X-ray scattering. Our co-assembled DNA-bottlebrush system is one of the few bottlebrushes known to date that shows liquid crystalline behaviour. The alignment of the DNA bottlebrushes was expected to increase with imposed pressure, but interestingly this did not always happen. Molecularly detailed self-consistent field calculations targeted to complement the experiments, focused on the role of molecular crowding on the induced persistence length lp due to the side chains and the cross-sectional width D of the molecular bottlebrushes. Both the thickness as well as the backbone persistence length drop with increasing protein-polymer bulk concentrations and dramatic effects are found above the overlap threshold. The flexibilisation is more significant and therefore the bottlebrush aspect ratio, lp/D, decreases with protein-polymer concentration. This loss in aspect ratio is yet another argument why molecular bottlebrushes rarely order in anisotropic phases and may explain why bottlebrushes are excellent lubricants.

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