Probing the Location of the Terminal Groups of Dendrimers in Dilute Solution

Topp, Andreas; Bauer, Barry J.; Klimash, June W.; Spindler, R.; Tomalia, Donald A.; Amis, Eric J.

doi:10.1021/ma990125s

Cited by 106 publications

(128 citation statements)

References 23 publications

(47 reference statements)

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“…Interestingly, the ͗R g 2 ͘ term exceeds the radius of gyration of the dendrimer at all Bjerrum lengths. For neutral dendrimers this finding is in agreement with experimental data 42 and with Brownian dynamics simulations. 43 As demonstrated in Ref.…”

Section: B Dendrimer Size and Counterion Condensationsupporting

confidence: 89%

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 Condensationsupporting

confidence: 89%

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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“…The same conclusion was obtained from the results of small-angle neutron scattering experiments on poly(amido amine) dendrimers using deuterium labelling and scattering contrast variation [21,60,61], and also by Brownian dynamics simulation [62]. Now let us compare the value of [g] with the volumes calculated on the basis of the translational friction coefficients.…”

Section: Discussionsupporting

confidence: 60%

Molecular characteristics of poly(propylene imine) dendrimers as studied with translational diffusion and viscometry

Корнеева

Meijer

2002

Colloid & Polymer Science

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“…Most computer simulations seem to agree that the endgroups of a dendrimer are distributed throughout the molecule 2,3,[7][8][9] and are not located predominantly on the outside of the dendrimer, as was postulated by the theory of de Gennes and Hervet. 10 Topp et al 11 however, concluded from SANS experiments on partially labeled dendrimers and the fact that the radius of gyration of the terminal groups R g,T was larger than R g of the entire gϭ7 dendrimer that the endgroups were concentrated near the periphery of the dendrimer. Lyulin et al 12,13 later showed that the radius of gyration is not a safe measure of the location of terminal units, since distribution functions with R g,T уR g can be constructed where most of the endgroups are located within the interior of the dendrimer.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of star-burst dendrimers in solution in relation to their structural properties

Rathgeber

Monkenbusch

Kreitschmann³

et al. 2002

The Journal of Chemical Physics

134

160

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We have measured both the static and dynamic structure factors of a single dendrimer with small-angle x-ray scattering ͑SAXS͒ and neutron spin-echo spectroscopy under good solvent conditions with the aim of finding a consistent correlation between the structural properties of dendrimers and their dynamic behavior. The samples under investigation were star-burst polyamidoamine dendrimers with generations gϭ0 to 8 in dilute methanol solutions. A model independent approach employing inverse Fourier transformation and square root deconvolution methods has been used to analyze the SAXS data to obtain the pair distance distribution function p(r) and the radial excess electron density profile ⌬ (r). In addition, we formulated a model that takes both the colloidal ͑globular, compact shape with form polydispersity or fuzzy surface͒ as well as the loose, polymeric ͑self-avoiding random walk͒ character of dendrimers into account. With this model we were able to describe the spectra of all dendrimer generations consistently. Parameters discussed as a function of the dendrimer generation are, among others, the correlation length of the density fluctuations ͑blob radius͒ , the radius of gyration R g , the sphere radius R s , the form polydispersity s or analogously, the width of the fuzzy surface region 2 f . Both the model-independent approach and the model fits reveal that at least down to the third generation the dendrimers exhibit a rather compact, globular shape. These findings are in agreement with the dynamic results obtained by NSE spectroscopy which probes length scales both larger and much smaller than the dimension of a single dendrimer. The method reveals that the dynamics throughout is dominated by the center-of-mass diffusion-the internal dynamics is suppressed. The diffusion coefficients obtained are close to the values calculated from the Stokes-Einstein relation using the sphere radius R s determined from the SAXS spectra. Dynamically, the dendrimers behave like ''hard'', solid spheres.

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Probing the Location of the Terminal Groups of Dendrimers in Dilute Solution

Cited by 106 publications

References 23 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

Molecular characteristics of poly(propylene imine) dendrimers as studied with translational diffusion and viscometry

Dynamics of star-burst dendrimers in solution in relation to their structural properties

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