The Poisson–Boltzmann–Flory Approach to Charged Dendrimers: Effect of Generation and Spacer Length

Kłos, J. S.

doi:10.1021/acs.macromol.9b00446

Cited by 5 publications

(6 citation statements)

References 64 publications

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“…This function for both dendrimers has a maximum due to the positive charges of the dendrimers and a minimum due to the counterion shells around them. The charge distribution obtained in our simulations corresponds to the classical double layer structure, which has been observed for dendrimers in many studies [107,108]. It is interesting that the values in maximum are approximately the same in the case of Lys-2Lys and Lys-2Gly dendrimers.…”

Section: The Local Structuresupporting

confidence: 82%

Comparison of Structure and Local Dynamics of Two Peptide Dendrimers with the Same Backbone but with Different Side Groups in Their Spacers

et al. 2020

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In this paper, we perform computer simulation of two lysine-based dendrimers with Lys-2Lys and Lys-2Gly repeating units. These dendrimers were recently studied experimentally by NMR (Sci. Reports, 2018, 8, 8916) and tested as carriers for gene delivery (Bioorg. Chem., 2020, 95, 103504). Simulation was performed by molecular dynamics method in a wide range of temperatures. We have shown that the Lys-2Lys dendrimer has a larger size but smaller fluctuations as well as lower internal density in comparison with the Lys-2Gly dendrimer. The Lys-2Lys dendrimer has larger charge but counterions form more ion pairs with its NH 3 + groups and reduce the bare charge and zeta potential of the first dendrimer more strongly. It was demonstrated that these differences between dendrimers are due to the lower flexibility and the larger charge (+2) of each 2Lys spacers in comparison with 2Gly ones. The terminal CH 2 groups in both dendrimers move faster than the inner CH 2 groups. The calculated temperature dependencies of the spin-lattice relaxation times of these groups for both dendrimers are in a good agreement with the experimental results obtained by NMR.

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Section: The Local Structuresupporting

confidence: 82%

Comparison of Structure and Local Dynamics of Two Peptide Dendrimers with the Same Backbone but with Different Side Groups in Their Spacers

et al. 2020

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“…This numerical scheme was used in many works on both neutral and charged polymer systems (see, e.g., refs , − , , , − ). The SF-SCF method accurately takes into account the spatial distribution of segments and the corresponding conformational entropy of branches by averaging over the ensemble of possible conformations of the dendrimer, in contrast to, e.g., the numerical Poisson–Boltzmann–Flory approach, which represents the dendrimer as a uniformly charged sphere.…”

Section: Model and Methodsmentioning

confidence: 99%

SCF Theory of Uniformly Charged Dendrimers: Impact of Asymmetry of Branching, Generation Number, and Salt Concentration

et al. 2020

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Polyelectrolyte dendrimers attract large interest and find multiple applications in many fields. The majority of theoretical and simulation works consider dendrimers with symmetrical branching where all spacers have the same length. In the present work, we for the first time systematically studied the effect of asymmetry of branching in flexible uniformly charged dendrimers on their structural properties. Lysine dendrimers with lysine amino acid residues as branching units and with spacers consisting of uniformly charged linear lysine (or arginine) peptides of two different lengths are an example of such dendrimers. The Scheutjens−Fleer self-consistent field approach was used to study the dendrimers with different asymmetries of branching and different generation numbers in solution at different salt concentrations. Three regimesosmotic, salt-dominant, and quasi-neutralwere distinguished, and corresponding theoretical scaling dependencies have been verified. It was demonstrated that largescale conformational properties practically do not depend on asymmetry of branching, but in the osmotic regime, the gyration radius weakly depends on it. The asymmetry of branching is manifested, however, in the internal structure of dendrimers, such as the radial distributions of monomer units, branching points, and terminal segments. The asymmetry of branching significantly affects also electrostatic properties of the dendrimers in the low-salt regime. While dendrimers with symmetric branching behave as a uniformly charged sphere with the maximum of electrostatic field on its surface, dendrimers with asymmetric branches behave as a sphere with decaying local charge density. The effective radius of an equivalent charged sphere increases and the surface electrostatic potential (ζ-potential) decreases with an increase of asymmetry of branching.

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“…A similar transition is observed by changing dendrimer generation from low to high at fixed effective Coulomb interaction strength. 48,53 An increase in dendrimer generation leads to an exponential increase in the number of oppositely charged species, which promotes Coulomb attraction and results in the uptake effect. Moreover, as seen in Figure 4b, unlike the Bjerrum length, the influence of the ionic diameter on the overall amount of absorbed counterions is weak.…”

Section: IIImentioning

confidence: 99%

Charged Dendrimers with Finite-Size Counterions

Kłos

Paturej

2020

J. Phys. Chem. B

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We report on the structure of dendritic polyelectrolytes accompanied by counterions in a good, salt-free, implicit solvent using Langevin dynamics simulations and a Flory-type approach. Our focus is on the modification of charged dendrimer conformations via the strength of electrostatic interactions and the counterion excluded volume. We study the effects caused by charges by varying the reduced Bjerrum length, λB *, between the extremes of weak and strong electrostatic interactions. The counterion excluded volume was controlled by the size of ions. We investigate counterions ranging from conventional ones, with the size comparable to the monomer size, to bulky ions. Our results indicate that, as compared to neutral dendrimers, dendritic polyelectrolytes exist in swollen conformations, and the degree of swelling changes non-monotonically with increasing λB *. For weak electrostatic couplings, counterion density within dendrimers is minor and their radius of gyration subtly exceeds the size of neutral dendrimers. For intermediate electrostatic couplings, Coulomb attraction between opposite charges promotes absorption of ions into dendrimers’ pervaded volume and counterion condensation on charged monomers. As a result, counterion density inside dendrimers abruptly increases and the ionic size starts to play a crucial role. In this regime, we observe that swelling of dendrimers reaches its maximum and is more pronounced for bulky counterions. For strong electrostatic couplings, complete condensation of conventional counterions proceeds, whereas for bulky ions condensation remains partial. In this regime, dendrimers deswell. In particular, in the presence of conventional ions, dendrimers collapse into globules, while, for bulky counterions, deswelling is suppressed.

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The Poisson–Boltzmann–Flory Approach to Charged Dendrimers: Effect of Generation and Spacer Length

Cited by 5 publications

References 64 publications

Comparison of Structure and Local Dynamics of Two Peptide Dendrimers with the Same Backbone but with Different Side Groups in Their Spacers

Comparison of Structure and Local Dynamics of Two Peptide Dendrimers with the Same Backbone but with Different Side Groups in Their Spacers

SCF Theory of Uniformly Charged Dendrimers: Impact of Asymmetry of Branching, Generation Number, and Salt Concentration

Charged Dendrimers with Finite-Size Counterions

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