1,721,044 research outputs found
How the Dynamics of a Supramolecular Polymer Determines Its Dynamic Adaptivity and Stimuli-Responsiveness: Structure-Dynamics-Property Relationships from Coarse-Grained Simulations
No full textThe rational design of supramolecular polymers that can adapt or respond in time to specific stimuli in a controlled way is interesting for many applications, but this requires understanding the molecular factors that make the material faster or slower in responding to the stimulus. To this end, it is necessary to study the dynamic adaptive properties at submolecular resolution, which is difficult at an experimental level. Here we show coarse-grained molecular dynamics simulations (<5 Å resolution) demonstrating how the dynamic adaptivity and stimuli responsiveness of a supramolecular polymer is controlled by the intrinsic dynamics of the assembly, which is in turn determined by the structure of the monomers. As a representative case, we focus on a water-soluble 1,3,5-benzenetricarboxamide (BTA) supramolecular polymer incorporating (charged) receptor monomers, experimentally seen to undergo dynamic clustering following the superselective binding to a multivalent recruiter. Our simulations show that the dynamic reorganization of the supramolecular structure proceeds via monomer diffusion on the dynamic fiber surface (exchange within the fiber). Rationally changing the structure of the monomers to make the fiber surface more or less dynamic allows tuning the rate of response to the stimulus and of supramolecular reconfiguration. Simple in silico experiments draw a structure-dynamics-property relationship revealing the key factors underpinning the dynamic adaptivity and stimuli-responsiveness of these supramolecular polymers. We come out with clear evidence that to master the bioinspired properties of these fibers, it is necessary to control their intrinsic dynamics, while the high-resolution of our molecular models permits us to show how
Molecular modelling of supramolecular polymers
Full text linkNature uses self-assembly for building supramolecular materials possessing fascinating properties (self-healing, adaptive, reconfigurable and responsive) that are fundamental for many complex biological functions. Artificial supramolecular polymers, composed of monomers that self-assemble via non-covalent interactions, are attracting increasing interest as platforms for building innovative materials, as these possess similar bioinspired dynamic properties. However, their design still relies on an inefficient/expensive trial-and-error approach. A key question is how to design the monomers to control the properties of the supramolecular polymer. Most often, obtaining from the experiments molecular-level information on how to control these assemblies is prohibitively difficult. Molecular modelling is a fundamental support in this field, allowing investigation of the supramolecular polymer from a privileged point of view and at high-resolution. Such a ‘virtual microscope’ can provide information on the factors that control supramolecular polymer structure and dynamics, on the monomer–monomer interactions and their cooperativity that are precluded to the experiments, paving the way to structure–property relationships useful to advance the rational design of such materials. This review discusses the state of the art of molecular modelling and simulation of supramolecular polymers. The field is advancing quickly. But the detailed insight that can be reached and the continuous technical developments promise that this is only the beginning
Effect of Concentration on the Supramolecular Polymerization Mechanism via Implicit-Solvent Coarse-Grained Simulations of Water-Soluble 1,3,5-Benzenetricarboxamide
Full text linkWe report an implicit-solvent coarse-grained (CG) model for a water-soluble 1,3,5-benzenetricarboxamide (BTA) supramolecular polymer. The technical advances guaranteed by this CG model allow simulation of the self-assembly of 1000 BTA monomers and easy variation of the BTA concentration into the system down to experimental dilute conditions. In this way, we can monitor the mechanism of supramolecular polymerization as a function of the concentration at submolecular resolution exceeding the microsecond time scale. While increasing the concentration produces rapid formation of large disordered clusters that are then converted into BTA fibers, moving to very dilute concentrations favors early ordering of the oligomers in solution even at small sizes. Interestingly, we observe that below a certain concentration the oligomers that dynamically grow in solution during the self-assembly present the same level (and amplification) of order of prestacked equilibrated oligomers of the same size, meaning that concentration-dependent kinetic effects have disappeared from the polymerization mechanism
Into the Dynamics of a Supramolecular Polymer at Submolecular Resolution
Full text linkTo rationally design supramolecular polymers capable of self-healing or reconfiguring their structure in a dynamically controlled way, it is imperative to gain access into the intrinsic dynamics of the supramolecular polymer (dynamic exchange of monomers) while maintaining a high-resolution description of the monomer structure. But this is prohibitively difficult at experimental level. Here we show atomistic, coarse-grained modelling combined with advanced simulation approaches to characterize the molecular mechanisms and relative kinetics of monomer exchange in structural variants of a synthetic supramolecular polymer in different conditions. We can capture differences in supramolecular dynamics consistent with the experimental observations, revealing that monomer exchange in and out the fibres originates from the defects present in their supramolecular structure. At the same time, the submolecular resolution of this approach offers a molecular-level insight into the dynamics of these bioinspired materials, and a flexible tool to obtain structure-dynamics relationships for a variety of polymeric assemblies
Effect of dietary intake of LCPUFA n-3 on CLA amount of milk | Modificazioni indotte dall'apporto dietetico di LCPUFA n-3 sul contenuto di CLA nel latte
No full textCLA has been reported to possess several benefic effects, likewise the metabolic positive activities of LC PUFA are known. So it is interesting to investigate the presence of the compounds in foods, the opportunities of increasing their dietary inteke and the reciprocal correlations. We have studied the effect of diets supplemented with free or protected LC PUFA n-3, given to dairy cows, on CLA amount in milk. We found an increase of CLA percentage in the milk of cows receiving LC PUFA n-3 supplementation, independently of the administration method, and a constant ratio between CLA and trans vaccenic acid in all experimental conditions
Modificazioni indotte dall'apporto dietetico di LCPUFA n-3 sul contenuto di CLA nel Latte
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The Membrane Bending Modulus in Experiments and Simulations
No full textThe bending modulus is one of the most important material properties of lipid membranes, playing an important role in a number of biological processes including exo- and endocytosis, vesicle fusion, and the regulation of membrane protein activity. Different experimental techniques have been developed to estimate the bending modulus of simple lipid membranes, but unfortunately they provide different results for the same lipid membranes in very similar conditions. Similar issues have been found in simulations, where different methods (and different energetic models) provide different results. In this review, we collect results from both experiments and simulations, and discuss possible reasons for the discrepancies among different techniques
Amphiphilic Gold Nanoparticles: A Biomimetic Tool to Gain Mechanistic Insights into Peptide-Lipid Interactions
No full textFunctional peptides are now widely used in a myriad of biomedical and clinical contexts, from cancer therapy and tumor targeting to the treatment of bacterial and viral infections. Underlying this diverse range of applications are the non-specific interactions that can occur between peptides and cell membranes, which, in many contexts, result in spontaneous internalization of the peptide within cells by avoiding energy-driven endocytosis. For this to occur, the amphipathicity and surface structural flexibility of the peptides play a crucial role and can be regulated by the presence of specific molecular residues that give rise to precise molecular events. Nevertheless, most of the mechanistic details regulating the encounter between peptides and the membranes of bacterial or animal cells are still poorly understood, thus greatly limiting the biomimetic potential of these therapeutic molecules. In this arena, finely engineered nanomaterials—such as small amphiphilic gold nanoparticles (AuNPs) protected by a mixed thiol monolayer—can provide a powerful tool for mimicking and investigating the physicochemical processes underlying peptide-lipid interactions. Within this perspective, we present here a critical review of membrane effects induced by both amphiphilic AuNPs and well-known amphiphilic peptide families, such as cell-penetrating peptides and antimicrobial peptides. Our discussion is focused particularly on the effects provoked on widely studied model cell membranes, such as supported lipid bilayers and lipid vesicles. Remarkable similarities in the peptide or nanoparticle membrane behavior are critically analyzed. Overall, our work provides an overview of the use of amphiphilic AuNPs as a highly promising tailor-made model to decipher the molecular events behind non-specific peptide-lipid interactions and highlights the main affinities observed both theoretically and experimentally. The knowledge resulting from this biomimetic approach could pave the way for the design of synthetic peptides with tailored functionalities for next-generation biomedical applications, such as highly efficient intracellular delivery systems
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