Synthesis, Characterization, and Double Layer Capacitance Charging of Nanoclusters Protected by 6-Mercaptopurine

Viudez, Alfonso J.; Madueño, Rafael; Blázquez, Manuel; Pineda, Teresa

doi:10.1021/jp810720t

Cited by 19 publications

(40 citation statements)

References 68 publications

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“…For alkanethiols with polar end groups, however, e.g., 6-mercaptopurine (6MP) on small, Au 459 (6MP) 62 , nanoparticles in water, a footprint of 29 Å 2 is obtained. 53 Hence, the 21.3 Å 2 value obtained for 11-MU is consistent with both the polar nature of this alkanethiolate ligand and the size and less acute surface curvature of the 13.8 nm Au NPs used in the present work.…”

Section: Resultssupporting

confidence: 85%

Nucleation and Island Growth of Alkanethiolate Ligand Domains on Gold Nanoparticles

et al. 2011

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The metal oxide cluster α-AlW(11)O(39)(9-) (1), readily imaged by cryogenic transmission electron microscopy (cryo-TEM), is used as a diagnostic protecting anion to investigate the self-assembly of alkanethiolate monolayers on electrostatically stabilized gold nanoparticles in water. Monolayers of 1 on 13.8 ± 0.9 nm diameter gold nanoparticles are displaced from the gold surface by mercaptoundecacarboxylate, HS(CH(2))(10)CO(2)(-) (11-MU). During this process, no aggregation is observed by UV-vis spectroscopy, and the intermediate ligand-shell organizations of 1 in cryo-TEM images indicate the presence of growing hydrophobic domains, or "islands", of alkanethiolates. UV-vis spectroscopic "titrations", based on changes in the surface plasmon resonance upon exchange of 1 by thiol, reveal that the 330 ± 30 molecules of 1 initially present on each gold nanoparticle are eventually replaced by 2800 ± 30 molecules of 11-MU. UV-vis kinetic data for 11-MU-monolayer formation reveal a slow phase, followed by rapid self-assembly. The Johnson, Mehl, Avrami, and Kolmogorov model gives an Avrami parameter of 2.9, indicating continuous nucleation and two-dimensional island growth. During nucleation, incoming 11-MU ligands irreversibly displace 1 from the Au-NP surface via an associative mechanism, with k(nucleation) = (6.1 ± 0.4) × 10(2) M(-1) s(-1), and 19 ± 8 nuclei, each comprised of ca. 8 alkanethiolates, appear on the gold-nanoparticle surface before rapid growth becomes kinetically dominant. Island growth is also first-order in [11-MU], and its larger rate constant, k(growth), (2.3 ± 0.2) × 10(4) M(-1) s(-1), is consistent with destabilization of molecules of 1 at the boundaries between the hydrophobic (alkanethiolate) and the electrostatically stabilized (inorganic) domains.

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Section: Resultssupporting

confidence: 85%

Nucleation and Island Growth of Alkanethiolate Ligand Domains on Gold Nanoparticles

et al. 2011

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“…In order to further check if the instability of the LYZ–AuNP bioconjugates depends on the binding characteristics of the protein on the nanoparticle surface, AuNPs protected by organic monolayers of different chemical nature have been used. The 6MP-AuNPs have been shown to be stable in alkaline media due to the negative charges of the 6MP molecules that show a dissociation p K a at pH around 6. , These molecules are covalently bound to the nanoparticle surface, and consequently, they are not displaced by the proteins upon bioconjugation. The pH–titration results of 6MP-AuNPs in the presence of 200 nM LYZ are shown in Figure b.…”

Section: Resultsmentioning

confidence: 99%

Influence of the Global Charge of the Protein on the Stability of Lysozyme–AuNP Bioconjugates

et al. 2014

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The relevant biological information to take into account the design of bionanoconjugates is the structural organization of the proteins that interact with a metallic nanoparticle and form a protein corona. We have studied the interaction of the protein lysozyme (LYZ) with gold nanoparticles (AuNPs) protected by citrate, 6-mercaptopurine, and ω-mercaptoundecanoic acid monolayers in aqueous solution in a wide pH range. The bioconjugates are stable at pH higher than the isoelectric point (pI) of LYZ. At lower pH, flocculation occurs possibly by interactions between the exposed positive charges of the protein. The modification of the Lys residues of the protein by either succinylation or phosphopyridoxylation brings about important changes in the bioconjugates' flocculation behavior. By considering the location of the modified residues in the three-dimensional structure of the protein, a different orientation upon binding in comparison to that of the native protein is proposed. Finally, the high fluorescence quenching observed in the titration experiments of the bioconjugates is discussed in terms of an amplification of the quenching efficiency by energy transfer on the self-assembled protein film and a severe effect of fluorofore interactions of the proteins attached to the nanoparticle surface.

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“…3,10 6-Mercaptopurine (6MP) has interest from the point of view of its applications in leukemia treatment 11 and therefore has been immobilized on gold nanoparticles with drug delivery purposes. [12][13][14][15] A few groups have studied 6MP SAMs on Au(111), [16][17][18][19][20] on Ag 21,22 and Hg 18,19 surfaces. In all cases, it has been reported that the molecule adsorbs through the S atom.…”

Section: Introductionmentioning

confidence: 99%

Thiol with an Unusual Adsorption−Desorption Behavior: 6-Mercaptopurine on Au(111)

et al. 2010

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A multitechnique study of 6-mercaptopurine (6MP) adsorption on Au(111) is presented. The molecule adsorbs on Au(111), originating short-range ordered domains and irregular nanosized aggregates with a total surface coverage by chemisorbed species smaller than those found for alkanethiol SAMs, as derived from scanning tunneling microscopy (STM) and electrochemical results. X-ray photoelectron spectroscopy (XPS) results show the presence of a thiolate bond, whereas density functional theory (DFT) data indicate strong chemisorption via a S-Au bond and additional binding to the surface via a N-Au bond. From DFT data, the positive charge on the Au topmost surface atoms is markedly smaller than that found for Au atoms in alkanethiolate SAMs. The adsorption of 6MP originates Au atom removal from step edges but no vacancy island formation at (111) terraces. The small coverage of Au islands after 6MP desorption strongly suggests the presence of only a small population of Au adatom-thiolate complexes. We propose that the absence of the Au-S interface reconstruction results from the lack of significant repulsive forces acting at the Au surface atoms.

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Synthesis, Characterization, and Double Layer Capacitance Charging of Nanoclusters Protected by 6-Mercaptopurine

Cited by 19 publications

References 68 publications

Nucleation and Island Growth of Alkanethiolate Ligand Domains on Gold Nanoparticles

Nucleation and Island Growth of Alkanethiolate Ligand Domains on Gold Nanoparticles

Influence of the Global Charge of the Protein on the Stability of Lysozyme–AuNP Bioconjugates

Thiol with an Unusual Adsorption−Desorption Behavior: 6-Mercaptopurine on Au(111)

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