Location of Terminal Groups of Dendrimers:  Brownian Dynamics Simulation

Lyulin, Alexey V.; Davies, G. R.; Adolf, David B.

doi:10.1021/ma0003811

Cited by 64 publications

(95 citation statements)

References 8 publications

(15 reference statements)

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“…For neutral dendrimers this finding is in agreement with experimental data 42 and with Brownian dynamics simulations. 43 As demonstrated in Ref. 43, and as we proceed to show, the fact that ͗R g 2 ͘ term Ͼ ͗R g 2 ͘ dend does not mean that beads of the terminal generation shell are localized near the dendrimer's periphery.…”

Section: B Dendrimer Size and Counterion Condensationmentioning

confidence: 59%

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Molecular dynamics study of charged dendrimers in salt-free solution: Effect of counterions

Gurtovenko

Lyulin

Karttunen

et al. 2006

The Journal of Chemical Physics

135

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Polyamidoamine (PAMAM) dendrimers, being protonated under physiological conditions, represent a promising class of nonviral, nano-sized vectors for drug and gene delivery. We performed extensive molecular dynamics simulations of a generic model dendrimer in a salt-free solution with dendrimer's terminal beads positively charged. Solvent molecules as well as counterions were explicitly included as interacting beads. We find that the size of the charged dendrimer depends non-monotonically on the strength of electrostatic interactions demonstrating a maximum when the Bjerrum length equals the diameter of a bead. Many other structural and dynamic characteristics of charged dendrimers are also found to follow this pattern. We address such a behavior to the interplay between repulsive interactions of the charged terminal beads and their attractive interactions with oppositely charged counterions. The former favors swelling at small Bjerrum lengths and the latter promotes counterion condensation. Thus, counterions can have a dramatic effect on the structure and dynamics of charged dendrimers and, under certain conditions, cannot be treated implicitly.

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Section: B Dendrimer Size and Counterion Condensationmentioning

confidence: 59%

“…43 As demonstrated in Ref. 43, and as we proceed to show, the fact that ͗R g 2 ͘ term Ͼ ͗R g 2 ͘ dend does not mean that beads of the terminal generation shell are localized near the dendrimer's periphery.…”

Section: B Dendrimer Size and Counterion Condensationmentioning

confidence: 59%

Molecular dynamics study of charged dendrimers in salt-free solution: Effect of counterions

Gurtovenko

Lyulin

Karttunen

et al. 2006

The Journal of Chemical Physics

135

View full text Add to dashboard Cite

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“…Then, for increasing r, g c.m. m drops down sharply to a local minimum and subsequently increases to a broad, local maximum [12,14,36,[39][40][41][42][43][44] that is flatter for the higher generation g = 6. The dotted lines in the figure show that due to swelling, the concentration of monomers tends to shift down inside the dendrimer, whereas for temperatures at which the molecules are more shrunken the monomers are packed in a denser way.…”

Section: Resultsmentioning

confidence: 98%

The Structure of Dendrimers with Charged Terminal Groups: Monte Carlo Simulations

Majtyka

Kłos

2006

Acta Phys. Pol. A

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Taking into account the full Coulomb potential and the excluded volume interactions, properties of dendrimers with generations g = 5, 6 with charged terminal groups and counterions in an athermal solvent are examined by lattice Monte Carlo simulations. The study treats counterions explicitly and focuses on the local structure of the systems inspected by pair correlation functions g ab that provide information on distributions of monomers, terminal groups and ions in space at various temperatures T * . Special emphasis is placed on counterions and their role they play in causing conformational changes of the molecules. The simulations show that counterions penetrate the interior of the dendrimers, and there is a major increase in their concentration there as T * decreases. Some of them condense onto the terminal groups and a reduction in the mean effective charge Q of the dendrimers appears. Within the range of temperatures where the condensation (as a function of T * ) is sharp the molecules weakly swell up when compared to their size at the other temperatures. This kind of behaviour is also reflected by the distributions of monomers and terminal groups.

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“…Thus the first precise experimental data about the gross size came from size exclusion chromatography (SEC), which is now being complemented with Small Angle Neutron Scattering (SANS) and Small Angle X-ray Scattering (SAXS) to determine gross size and some structural details of dendrimers. [14][15][16] In recent years, computational and theoretical techniques [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] proved to be very effective elucidating the structural properties of the dendrimer both in good and bad solvent 18,19 . Many of these theoretical results agree very well with the available experimental data 36-37, 15, 16 on such systems.…”

Section: Introductionmentioning

confidence: 99%

Structure of poly(propyl ether imine) dendrimer from fully atomistic molecular dynamics simulation and by small angle x-ray scattering

Jana

Jayamurugan

Ganapathy

et al. 2006

The Journal of Chemical Physics

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Abstract:We study the structure of carboxylic acid terminated neutral poly (propyl ether imine) (PETIM) dendrimer from generation 1 through 6 (G1-G6) in a good solvent (water) by fully atomistic molecular dynamics (MD) simulations. We determine as a function of generation such structural properties as: radius of gyration, shape tensor, asphericity, fractal dimension, monomer density distribution, and end-group distribution functions. The sizes obtained from the MD simulations have been validated by Small Angle X-Ray Scattering (SAXS) experiment on dendrimer of generation 2 to 4 (G2 -G4). A good agreement between the experimental and theoretical value of radius of gyration has been observed. We find a linear increase in radius of gyration with the generation. In contrast, R g scales as ~x N with the number of monomers. We find two distinct exponents depending on the generations: x = 0.47 for G1-G3 and x = 0.28 for G3-G6 which reveals their non-space filling nature. In comparison with the amine terminated PAMAM dendrimer, we find R g of G-th generation PETIM dendrimer is nearly equal to that of (G+1)-th generation of PAMAM dendrimer as observed by Maiti et. al. [Macromolecules, 38, 979 2005]. We find substantial back folding of the outer sub generations into the interior of the dendrimer. Due to their highly flexible nature of the repeating branch units, the shape of the PETIM dendrimer deviates significantly from the spherical shape and the molecules become more and more spherical as the generation increases. The interior of the dendrimer is quite open with internal cavities available for accommodating guest molecules suggesting using PETIM * For correspondence: maiti@physics.iisc.ernet.in (PKM) or jayaraman@orgchem.iisc.ernet.in (NJ)or asood@physics.iisc.ernet.in (AKS) 2 dendrimer for guest-host applications. We also give a quantitative measure of the number of water molecules present inside the dendrimer.3

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Location of Terminal Groups of Dendrimers: Brownian Dynamics Simulation

Cited by 64 publications

References 8 publications

Molecular dynamics study of charged dendrimers in salt-free solution: Effect of counterions

Molecular dynamics study of charged dendrimers in salt-free solution: Effect of counterions

The Structure of Dendrimers with Charged Terminal Groups: Monte Carlo Simulations

Structure of poly(propyl ether imine) dendrimer from fully atomistic molecular dynamics simulation and by small angle x-ray scattering

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