Spin‐Probe Investigations of Head Group Behavior in Aqueous Dispersions of a Nonionic Amphiphilic Compound

Nakagawa, Kouichi

doi:10.1007/s11745-007-3048-2

Cited by 9 publications

(11 citation statements)

References 18 publications

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“…Hyperfine coupling constants A xx , A yy of 2.3 G and A zz of 27 G and the values of the gyromagnetic tensor g x 2.008, g y 2.006, and g z 2.002 were determined by simulating the experimental spectrum with Bruker SIMFONIA in a third‐order perturbation theory approach (with an error of 10%). The values of the EPR parameters are similar to that described in the literature for lipid bilayers and indicate that the nitroxide spin probe is immobilized in the vesicles membrane on the timescale relevant for CW‐EPR. 5‐DSA encapsulated in PEG loaded vesicles produced a more complex signal that consisted of a superposition of an anisotropic EPR pattern associated with the entrapment in the membrane siloxane layer (see above), and an isotropic pattern similar to that observed in both 0.1 m NaOH and 60 mg mL −1 PEG solution.…”

Section: Resultssupporting

confidence: 81%

Investigation of Horseradish Peroxidase Kinetics in an “Organelle-Like” Environment

Baumann

Spulber

Fischer

et al. 2017

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In order to mimic cell organelles, artificial nanoreactors have been investigated based on polymeric vesicles with reconstituted channel proteins (outer membrane protein F) and coencapsulated enzymes horseradish peroxidase (HRP) along with a crowding agent (Ficoll or polyethylene glycol) inside the cavity. Importantly, the presence of macromolecules has a strong impact on the enzyme kinetics, but no influence on the integrity of vesicles up to certain concentrations. This particular design allows for the first time the determination of HRP kinetics inside nanoreactors with crowded milieu. The values of the Michaelis-Menten constant (K ) measured for HRP in a confined space (encapsulated in nanoreactors) in the absence of macromolecules are ≈50% lower than in free conditions, and the presence of a crowding agent results in a further pronounced decrease. These results clearly suggest that activities of enzymes in confined spaces can be tuned by varying the concentrations of crowding compounds. The present investigation represents an advance in nanoreactor design by considering the influence of environmental factors on enzymatic performance, and it demonstrates that both encapsulation and the presence of a crowding environment increase the enzyme-substrate affinity.

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Section: Resultssupporting

confidence: 81%

Investigation of Horseradish Peroxidase Kinetics in an “Organelle-Like” Environment

Baumann

Spulber

Fischer

et al. 2017

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“…In contrast, OmpF-S-S-NO gave a broad anisotropic EPR spectrum with no isotropic component, and is similar to that reported for 5-DSA in lipid bilayers or cholesterol aqueous solutions 48 . This EPR spectrum indicates hindered rotation of the nitroxide probe 49 after binding to the OmpF mutant (OmpF-S-S-NO), and demonstrates successful binding of the bis-(2,2,5,5-tetramethyl-3-imidazoline-1-oxyl-4-yl) disulphide to the modified OmpF mutant (Fig. 2a ).…”

Section: Resultsmentioning

confidence: 83%

Biomimetic artificial organelles with in vitro and in vivo activity triggered by reduction in microenvironment

et al. 2018

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Despite tremendous efforts to develop stimuli-responsive enzyme delivery systems, their efficacy has been mostly limited to in vitro applications. Here we introduce, by using an approach of combining biomolecules with artificial compartments, a biomimetic strategy to create artificial organelles (AOs) as cellular implants, with endogenous stimuli-triggered enzymatic activity. AOs are produced by inserting protein gates in the membrane of polymersomes containing horseradish peroxidase enzymes selected as a model for natures own enzymes involved in the redox homoeostasis. The inserted protein gates are engineered by attaching molecular caps to genetically modified channel porins in order to induce redox-responsive control of the molecular flow through the membrane. AOs preserve their structure and are activated by intracellular glutathione levels in vitro. Importantly, our biomimetic AOs are functional in vivo in zebrafish embryos, which demonstrates the feasibility of using AOs as cellular implants in living organisms. This opens new perspectives for patient-oriented protein therapy.

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“…The results can be due to different molecular motions of CHL having aromatic rings and its location in the membrane. It was also suggested that EPR and EPR simulation for the cholesterol derived probe remain preferentially in the liquid ordered region of the detergent-resistant membrane [18]. The experimental errors are presented in Fig.…”

Section: T 1e Of the Head Group Regionmentioning

confidence: 93%

“…7. The T 1e values obtained are listed in Table 1 together with the various values obtained by EPR slow-tumbling simulation [12,13,18]. The T 1e for CHL is slightly longer than one for 5-DSA.…”

Section: T 1e Of the Head Group Regionmentioning

confidence: 94%

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EPR Investigations of Spin‐Probe Dynamics in Aqueous Dispersions of a Nonionic Amphiphilic Compound

Nakagawa¹

2008

J Americ Oil Chem Soc

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Dynamics of various spin probes in aqueous dispersions of nonionic amphiphilic compound, [poly(oxyethylene) hydrogenated castor oil, HCO], were investigated by EPR (electron paramagnetic resonance) and saturation recovery (SR) spectroscopies. Partitioning, rotational correlation time (s R ), rotational diffusion coefficient, and electron spin-lattice relaxation time (T 1e ) in dispersions of the HCO membrane were obtained. The partitioning of water soluble spin probes, DTBN and TEMPO, in the aqueous and vesicle phases was determined by an EPR linewidth simulation as a function of temperature. The results suggest that DTBN and TEMPO have a similar partitioning in the vesicle phase throughout the temperatures studied. The longer s R and shorter T 1e (*0.33 ls) values of DTBN in the vesicle phase were obtained, and could be attributed to the probe environment in the membrane. The simulation results for fast tumbling probes were quite different from those of conventional intensity analysis (spectral parameter, f). Thus, the simulation and T 1e analyses have provided a quantitative understanding of the probe dynamics in both phases. Aliphatic spin probes, doxylstearic acids (DSAs) and 3b-doxyl-5a-cholestane (CHL), were used for monitor of various membrane motions. The EPR spectra were quantitatively analyzed by a slow tumbling simulation. The rotational diffusion coefficients and order parameter were obtained by the simulation. In addition, the direct observations of the behavior of the probes were measured by SR method. The results were consistent with T 1e obtained for spin probes. Thus, the quantitative results regarding EPR, SR method, various simulation analyses have provided detailed information regarding physicochemical properties of the various moieties of the probe region in the amphiphilic compound.

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Spin‐Probe Investigations of Head Group Behavior in Aqueous Dispersions of a Nonionic Amphiphilic Compound

Cited by 9 publications

References 18 publications

Investigation of Horseradish Peroxidase Kinetics in an “Organelle-Like” Environment

Investigation of Horseradish Peroxidase Kinetics in an “Organelle-Like” Environment

Biomimetic artificial organelles with in vitro and in vivo activity triggered by reduction in microenvironment

EPR Investigations of Spin‐Probe Dynamics in Aqueous Dispersions of a Nonionic Amphiphilic Compound

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