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Effect of Solvent and pH on the Structure of PAMAM Dendrimers

Maiti, Prabal K. and Çağin, Tahir and Lin, Shiang-Tai and Goddard, William A., III (2005) Effect of Solvent and pH on the Structure of PAMAM Dendrimers. Macromolecules, 38 (3). pp. 979-991. ISSN 0024-9297. doi:10.1021/ma049168l.

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We report various structural and conformational properties of generations 4, 5, and 6 PAMAM (polyamidoamine) dendrimer [EDA (ethylenediamine) core)] at various protonation levels through extensive molecular dynamics (MD) simulations in explicit solvent. The presence of solvent leads to swelling of the dendrimer (by 33% for G5 compared to the case of no solvent). We find that decreasing the solution from high pH (∼10, no protonation) to neutral (∼7, only primary amines protonated) to low pH (∼4, tertiary amines also protonated) changes the radius of gyration of G5 from 21 to 22 to 25 Å, respectively. We also report such other structural quantities as radial density, distribution of terminal groups, solvent accessible surface area and volume, shape, and structure factors (to compare with SAXS and SANS experiments) at various pH conditions. We find significant back-folding of the outer subgenerations in the interior of the molecules at all levels of pH, contrary to original expectations and some SANS experiments but in agreement with other SANS experiments. We find significant water penetration inside the dendrimer, with ∼3 water/tertiary amine for high pH and ∼6 water/tertiary amine for low pH (all for G5). This indicates that the interior of the dendrimer is quite open with internal cavities available for accommodating guest molecules, suggesting using PAMAM dendrimer for guest−host applications. This estimate of internal waters suggests that sufficient water is available to facilitate metal ion binding.

Item Type:Article
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URLURL TypeDescription
Maiti, Prabal K.0000-0002-9956-1136
Çağin, Tahir0000-0002-3665-0932
Lin, Shiang-Tai0000-0001-8513-8196
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2005 American Chemical Society. Received 28 April 2004. Published online 13 January 2005. Published in print 1 February 2005. We thank Dr. Mamadou Diallo for useful discussions. We thank an anonymous referee for bringing out the issue of calculating effective Debye length. This material is partly based upon work supported by, or in part by, the U.S. Army Research Laboratory and the U.S. Army Research Office under Grant DAAG55-97-1-0126 (Doug Kiserow) and completed with funding from NSF (NIRT CTS-0132002). The facilities of the MSC are also supported by grants from ARO (DURIP), ONR (DURIP), NSF, NIH, ChevronTexaco, General Motors, Seiko Epson, Asahi Kasei, and Beckman Institute.
Funding AgencyGrant Number
Army Research Office (ARO)DAAG55-97-1-0126
Office of Naval Research (ONR)UNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Issue or Number:3
Record Number:CaltechAUTHORS:20170724-070314201
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Official Citation:Effect of Solvent and pH on the Structure of PAMAM Dendrimers Prabal K. Maiti, Tahir Çaǧın, Shiang-Tai Lin, and William A. Goddard, III Macromolecules 2005 38 (3), 979-991 DOI: 10.1021/ma049168l
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79279
Deposited By: Ruth Sustaita
Deposited On:24 Jul 2017 16:29
Last Modified:15 Nov 2021 17:46

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