TY - JOUR
T1 - Effect of pH on Eosin Y/PAMAM interactions studied from absorption spectroscopy and molecular dynamics simulations
AU - Barraza, Luis F.
AU - Zuñiga, Matías
AU - Alderete, Joel B.
AU - Arbeloa, Ernesto M.
AU - Jiménez, Verónica A.
N1 - Funding Information:
Authors thank FONDECYT Grant number 1160060 , Postdoctoral FONDECYT Grant 3160378 . MZ thanks CONICYT doctoral fellowship number 21140192 . Financial support from CONICET (PIP 2015-11220150100687CO ) and Universidad Nacional de Río Cuarto is gratefully acknowledged.
PY - 2018/7/1
Y1 - 2018/7/1
N2 - Absorption spectroscopy experiments were carried out to examine the 1:1 supramolecular interaction between Eosin Y (EOS) and low generation G0-G3 poly(amido amine) (PAMAM) dendrimers at neutral and basic media, aimed at gaining insight about the role of pH and dendrimer generation on EOS-PAMAM binding. Our results revealed that EOS complexation is favored under neutral pH conditions, and that the supramolecular interaction strengthens as the dendrimer generation increases. Further molecular-level information regarding EOS-PAMAM systems was obtained from Molecular Dynamics (MD) simulations, Non-Covalent Interaction (NCI) analysis and MM/PBSA binding free energy calculations, which were carried out to examine the role of the generation, charge, and protonation state of PAMAM on the structure, conformation, and preferable interactions with EOS at neutral and basic pH conditions. Theoretical predictions were in high agreement with experimental results, showing that neutral pH allows a faster, deeper, and more stable complexation of the dye within dendrimer cavities, and that higher generation dendrimers induce a larger affinity towards EOS. According to MD results, the binding mode of the dye favors the interaction of the xanthene moiety within internal dendrimer cavities through the establishment of attractive van der Waals contacts. On the other hand, the carboxylate moiety interacts with the outermost dendrimer branches and remains exposed towards the solvent in G0-G2 PAMAM. These results support the validity of using MD simulations as auxiliary tools to deal with supramolecular complexation phenomena involving PAMAM dendrimers as host molecules.
AB - Absorption spectroscopy experiments were carried out to examine the 1:1 supramolecular interaction between Eosin Y (EOS) and low generation G0-G3 poly(amido amine) (PAMAM) dendrimers at neutral and basic media, aimed at gaining insight about the role of pH and dendrimer generation on EOS-PAMAM binding. Our results revealed that EOS complexation is favored under neutral pH conditions, and that the supramolecular interaction strengthens as the dendrimer generation increases. Further molecular-level information regarding EOS-PAMAM systems was obtained from Molecular Dynamics (MD) simulations, Non-Covalent Interaction (NCI) analysis and MM/PBSA binding free energy calculations, which were carried out to examine the role of the generation, charge, and protonation state of PAMAM on the structure, conformation, and preferable interactions with EOS at neutral and basic pH conditions. Theoretical predictions were in high agreement with experimental results, showing that neutral pH allows a faster, deeper, and more stable complexation of the dye within dendrimer cavities, and that higher generation dendrimers induce a larger affinity towards EOS. According to MD results, the binding mode of the dye favors the interaction of the xanthene moiety within internal dendrimer cavities through the establishment of attractive van der Waals contacts. On the other hand, the carboxylate moiety interacts with the outermost dendrimer branches and remains exposed towards the solvent in G0-G2 PAMAM. These results support the validity of using MD simulations as auxiliary tools to deal with supramolecular complexation phenomena involving PAMAM dendrimers as host molecules.
KW - Dendrimers
KW - Eosin Y
KW - Host-guest chemistry
KW - Molecular dynamics
KW - PAMAM
UR - http://www.scopus.com/inward/record.url?scp=85044572643&partnerID=8YFLogxK
U2 - 10.1016/j.jlumin.2018.03.068
DO - 10.1016/j.jlumin.2018.03.068
M3 - Article
AN - SCOPUS:85044572643
SN - 0022-2313
VL - 199
SP - 258
EP - 265
JO - Journal of Luminescence
JF - Journal of Luminescence
ER -