Surfactant Structure-Dependent Interactions with Modified Starch Nanoparticles Probed by Fluorescence Spectroscopy

Zhang, Qian; Kim, Damin; Li, Lü; Patel, Sanjay; Duhamel, Jean

doi:10.1021/acs.langmuir.8b03794

Cited by 20 publications

(8 citation statements)

References 43 publications

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“…This observation suggested formation of Py-PLL aggregates in solution. Since the presence of Py-PLL aggregates in solution would affect the interpretation of the results obtained by pyrene excimer fluorescence/formation (PEF), their existence was investigated using Förster resonance energy transfer (FRET) with naphthalene and pyrene labels since they constitute a well-known pair of FRET donor and acceptor, − respectively. A PLL sample was labeled with 1-naphthaleneacetic acid to yield a Np-PLL sample with a molar fraction of naphthalene-labeled lysine ( x Np ) of 0.09.…”

Section: Resultsmentioning

confidence: 99%

Effect of Structure on Polypeptide Blobs: A Model Study Using Poly(l-lysine)

Casier

Duhamel

2020

Langmuir

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The conformation of a series of pyrene-labeled poly(l-lysine)s (Py-PLLs) in 60:40 and 90:10 (v/v) acetonitrile:water mixtures was determined by comparing the results obtained from the fluorescence blob model (FBM) analysis of their fluorescence decays with those obtained from molecular mechanics optimizations (MMOs). PLL aggregates formed in both solutions as demonstrated by FRET experiments between naphthalene- and pyrene-labeled PLLs. Addition of an excess of unlabeled PLL allowed the conformational study of isolated Py-PLL embedded in a matrix of unlabeled PLLs. By varying the acetonitrile (ACN) content of the solution from 60 to 90 vol % ACN, Py-PLL was found to undergo a conformational change from a random coil to an α-helix. The conformational change induced an increase in the maximum number of lysines (N blob) separating two pyrene-labeled lysines that could still form an excimer between an excited- and a ground-state pyrene. N blob obtained from the FBM analysis increased from 15.2 ± 2.1 to 25.2 ± 1.2 lysines as PLL changed its conformation from a random coil to an α-helix. AFM revealed that the α-helical PLLs organized themselves into structured bundles ∼22 nm in diameter. The FBM analysis of the decays acquired with a solution of aggregated Py-PLLs in a 90:10 ACN:water mixture yielded a larger N blob value of 36.6 ± 3.4. The increase in N blob indicated that the Py-PLL constructs could now interact with one another in the helical bundles. This increase in N blob was then used in conjunction with MMOs to determine an interhelical spacing of 2.9 ± 0.1 nm for Py-PLLs in a bundle. This interhelical spacing resulted in a local density of 0.25 ± 0.01 g·cm–3 for the bundles of PLL α-helices, which was a reasonable density for a protein in solution. This study describes an experimental means to probe the number of amino acids that interact with each other as the conformation of a polypeptide evolves from that of a random coil to that of an α-helix to finally that of a bundle of α-helices.

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Section: Resultsmentioning

confidence: 99%

Effect of Structure on Polypeptide Blobs: A Model Study Using Poly(l-lysine)

Casier

Duhamel

2020

Langmuir

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“…The synthesis of the pyrene-labeled amylopectin fragments (Py-NAFs) has been described in detail in an earlier publication. 16 The only difference with the preparation of the Py-Amylopectin samples was that the purified NAFs were dissolved directly in a 3:1 DMSO:DMF mixture at 60 °C for labeling with PyBA.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

A Pyrene Excimer Fluorescence (PEF) Study of the Interior of Amylopectin in Dilute Solution

Kim

Zhai

et al. 2020

Macromolecules

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The large size of amylopectin represents an experimental challenge for standard analytical techniques to characterize its structure at the molecular level in dilute solution. We introduce a methodology that combines pyrene excimer fluorescence (PEF), the fluorescence blob model (FBM), molecular mechanics optimizations (MMOs), and intrinsic viscosity ([η]) to probe the interior of complex macromolecules with a heterogeneous interior like amylopectin. The combination of PEF, FBM, and MMOs yields the density (ρ fluo ) of nanosized subvolumes of the macromolecule, called blobs within the framework of the FBM, while [η] yields the density (ρ) probed over the length scale of the entire macromolecule. Comparison of ρ and ρ fluo indicates whether matter is either homogeneously (ρ = ρ fluo ) or heterogeneously (ρ < ρ fluo ) distributed inside the macromolecule. The main advantage of the methodology is to shift the focus of the study from the entire polydisperse macromolecule to that of monodisperse blobs where a blob represents the volume probed by a given pyrene derivative. This methodology is thus ideally suited to probe polydisperse heterogeneous macromolecules in solution. It is applied to amylopectin. The finding that ρ was much smaller than ρ fluo for amylopectin in dilute solution led to the conclusion that the side chains of amylopectin are heterogeneously distributed inside the amylopectin interior. The ρ fluo value agreed with the notion that the helical side chains of amylopectin form clusters where the side chains are ∼2.7 nm apart. When ρ and ρ fluo were determined for nanosized amylopectin fragments (NAFs) produced through extrusion, ρ fluo took the same value as for amylopectin while ρ increased with decreasing NAF size, approaching ρ fluo for the smallest NAF. This observation led to the conclusion that the clusters of helical oligosaccharide side chains were loosely connected to each other via linear oligosaccharide segments. These features were captured by the solution-cluster (Sol-CL) model which seems to rationalize many of the experimental observations made about amylopectin.

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“…The apparent lack of pyrene aggregation experienced by the PyEG 5 −PEG n MA samples was further supported by using Tables 4 and S1 to compare their excimer fluorescence decays to those obtained earlier for four Py−WSPs in water and in an organic solvent. These Py−WSPs were a pyrene-labeled poly(N,N-dimethylacrylamide) (Py(5.2)-PDMA), 58 poly(Lglutamic acid) (Py(7.0)-PGA), 59 a nanosized amylopectin fragment (Py(2.3)-NAF), 60 and a hydrophobically modified alkali swellable emulsion polymer (Py(2.1)-HASE), where the number in parentheses represents the molar percentage of structural units labeled with pyrene. 61 The chemical structure of these polymers is presented in Table 3.…”

Section: × [ ]mentioning

confidence: 99%

Location of a Hydrophobic Load in Poly(oligo(ethylene glycol) methyl ether methacrylate)s (PEGMAs) Dissolved in Water and Probed by Fluorescence

Thoma,

Little,

Duhamel

2024

Langmuir

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Two series of pyrene-labeled poly(oligo(ethylene glycol) methyl ether methacrylate)s referred to as PyEG 5 −PEG n MA and PyC 4 −PEG n MA were prepared to probe the region surrounding the polymethacrylate backbone by using the fluorescence of the dye pyrene. PyEG 5 −PEG n MA and PyC 4 −PEG n MA were prepared by copolymerizing the EG n MA methacrylate monomers with penta(ethylene glycol) 1-pyrenemethyl ether methacrylate or 1-pyrenebutyl methacrylate, respectively. In organic solvents, the much longer 18 non-hydrogen atom linker connecting the pyrene moieties to the polymethacrylate backbone in the PyEG 5 −PEG n MA samples enabled the deployment of the pyrenyl labels into the solution. In water, however, an excited pyrene for PyEG 5 −PEG n MA was found to probe a same volume as for the PyC 4 −PEG n MA samples where a much shorter 6 nonhydrogen atom spacer connected pyrene to the backbone. Another surprising observation, considering that the hydrophobicity of pyrene induces strong pyrene aggregation for many pyrene-labeled water-soluble polymers (Py−WSPs) in water, was the little pyrene aggregation found for the PyEG 5 −PEG n MA and PyC 4 −PEG n MA samples in water. These effects could be related to the organic-like domain (OLD) generated by the oligo(ethylene glycol) side chains densely arranged around the polymethacrylate backbone of the polymeric bottlebrush (PBB). Additional fluorescence experiments conducted with the penta(ethylene glycol) 1pyrenemethyl ether derivative indicated that the cylindrical OLD surrounding the polymethacrylate backbone had a chemical composition similar to that of ethylene glycol. Binding of hydrophobic pyrene molecules to unlabeled PEG n MA bottlebrushes in water further supported the existence of the OLD. The demonstration, that PEG n MA samples form an OLD in water, which can host and protect hydrophobic cargoes like pyrene, should lead to the development of improved PEG n MA-based drug delivery systems.

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Surfactant Structure-Dependent Interactions with Modified Starch Nanoparticles Probed by Fluorescence Spectroscopy

Cited by 20 publications

References 43 publications

Effect of Structure on Polypeptide Blobs: A Model Study Using Poly(l-lysine)

Effect of Structure on Polypeptide Blobs: A Model Study Using Poly(l-lysine)

A Pyrene Excimer Fluorescence (PEF) Study of the Interior of Amylopectin in Dilute Solution

Location of a Hydrophobic Load in Poly(oligo(ethylene glycol) methyl ether methacrylate)s (PEGMAs) Dissolved in Water and Probed by Fluorescence

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