| 1. |
- Kim, Ji Hye, et al.
(author)
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Study on the Dependence of Sun Protection Factor on Particle Size Distribution of Mica Using Gravitational Field-Flow Fractionation
- 2020
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In: Bulletin of the Korean Chemical Society. - : Wiley. - 0253-2964 .- 1229-5949. ; 41:1, s. 66-72
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Journal article (peer-reviewed)abstract
- Sunlight consists of beams of light of broad wavelength ranges, including infrared, visible, and ultraviolet (UV) radiation; X-rays; and γ-rays. Although the UV content of sunlight is relatively low, the human body, especially the human skin, is sensitive to UV rays. Mica is known to be effective in protecting the human skin from sunlight and reduces fine lines and pores on the skin. Mica is currently used as a coloring agent in various sunscreen products. Still, there is no detailed report on the effect of mica on the sun protection factor (SPF). In this study, effects of the particle size, particle size distribution, and the content of mica on SPF were studied. Gravitational field-flow fractionation (GrFFF) was employed to analyze the particle size and the particle size distribution of the mica particles. GrFFF provided size-based separation of the mica particles and was useful for determining the size distributions and average sizes of the mica particles. It was found that the mixing ratio (in wt %) of 3:3:4 of TiO2:octyl methoxycinnamate:mica yielded the highest SPF. Generally, the SPF tends to increase with increasing particle size of the mica.
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| 2. |
- Choi, Jaeyeong, et al.
(author)
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Characterization of binding between model protein GA-Z and human serum albumin using asymmetrical flow field-flow fractionation and small angle X-ray scattering.
- 2020
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:11
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Journal article (peer-reviewed)abstract
- Protein-based drugs often require targeted drug delivery for optimal therapy. A successful strategy to increase the circulation time of the protein in the blood is to link the therapeutic protein with an albumin-binding domain. In this work, we characterized such a protein-based drug, GA-Z. Using asymmetrical flow field-flow fractionation coupled with multi-angle light scattering (AF4-MALS) we investigated the GA-Z monomer-dimer equilibrium as well as the molar binding ratio of GA-Z to HSA. Using small angle X-ray scattering, we studied the structure of GA-Z as well as the complex between GA-Z and HSA. The results show that GA-Z is predominantly dimeric in solution at pH 7 and that it binds to monomeric as well as dimeric HSA. Furthermore, GA-Z binds to HSA both as a monomer and a dimer, and thus, it can be expected to stay bound also upon dilution following injection in the blood stream. The results from SAXS and binding studies indicate that the GA-Z dimer is formed between two target domains (Z-domains). The results also indicate that the binding of GA-Z to HSA does not affect the ratio between HSA dimers and monomers, and that no higher order oligomers of the complex are seen other than those containing dimers of GA-Z and dimers of HSA.
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| 3. |
- Choi, Jaeyeong, et al.
(author)
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Characterization of the molar mass distribution of macromolecules in beer for different mashing processes using asymmetric flow field-flow fractionation (AF4) coupled with multiple detectors
- 2017
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In: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 409:19, s. 4551-4558
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Journal article (peer-reviewed)abstract
- The macromolecular composition of beer is largely determined by the brewing and the mashing process. It is known that the physico-chemical properties of proteinaceous and polysaccharide molecules are closely related to the mechanism of foam stability. Three types of “American pale ale” style beer were prepared using different mashing protocols. The foam stability of the beers was assessed using the Derek Rudin standard method. Asymmetric flow field-flow fractionation (AF4) in combination with ultraviolet (UV), multiangle light scattering (MALS) and differential refractive index (dRI) detectors was used to separate the macromolecules present in the beers and the molar mass (M) and molar mass distributions (MD) were determined. Macromolecular components were identified by enzymatic treatments with β-glucanase and proteinase K. The MD of β-glucan ranged from 106 to 108 g/mol. In addition, correlation between the beer’s composition and foam stability was investigated (increased concentration of protein and β-glucan was associated with increased foam stability).
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| 4. |
- Choi, Jaeyeong, et al.
(author)
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Separation and zeta-potential determination of proteins and their oligomers using electrical asymmetrical flow field-flow fractionation (EAF4)
- 2020
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In: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1633
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Journal article (peer-reviewed)abstract
- Electrical asymmetrical flow field-flow fractionation (EAF4) is an interesting new analytical technique that separates proteins based on size or molecular weight and simultaneously determines the electrical characteristics of each population. However, until now, the research using EAF4 has not been published except for the proof-of-concept in the original publication by Johann et. al. in 2015 [1]. Hence the methods capabilities and optimized conditions need to be further investigated, such as composition of the carrier liquid, pH stability and effect of the electric field strength. The pH instability was observed in the initial method of EAF4 due to the electrolysis products when applied electric field. Therefore, we have investigated and provided a modified method for rapid pH stabilization through additional focusing step with the electric field. Then, the electrical properties such as the zeta-potential and effective net charge of the monomer and oligomers of three different proteins (GA-Z, BSA, and Ferritin) were determined based on their electrophoretic mobility from EAF4. The results showed that there were limitations to the applicability of separation by EAF4 to proteins. Nevertheless, this study shows that EAF4 is an interesting new technique that can examine the zeta-potential of individual proteins in mixtures (or monomers and oligomers) not accessible by other techniques.
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| 5. |
- Choi, Jaeyeong, et al.
(author)
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Study on oligomerization of glutamate decarboxylase from Lactobacillus brevis using asymmetrical flow field-flow fractionation (AF4) with light scattering techniques
- 2018
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In: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 410:2, s. 451-458
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Journal article (peer-reviewed)abstract
- In this work, asymmetrical flow field-flow fractionation (AF4) coupled with UV/Vis, multi-angle light scattering (MALS), and differential refractive index (dRI) detectors (AF4-UV-MALS-dRI) was employed for analysis of glutamate decarboxylase (LbGadB) from Lactobacillus brevis (L. brevis). AF4 provided molecular weight (MW) (or size)-based separation of dimer, hexamer, and aggregates of LbGadB. The effect of pH on oligomerization of LbGadB was investigated, and then AF4 results were compared to those from molecular modeling. The MWs measured by AF4-UV-MALS-dRI for dimeric and hexameric forms of LbGadB were 110 and 350 kDa, respectively, which are in good agreements with those theoretically calculated (110 and 330 kDa). The molecular sizes determined by AF4-UV-MALS-dRI were also in good agreement with those obtained from molecular modeling (6 and 10 nm, respectively, for dimeric and hexameric from AF4-UV-MALS-dRI and 6.4 × 7.6 and 7.6 × 13.1 nm from molecular modeling). The effects of temperature, salt type, and salt concentration on oligomerization of LbGadB were also investigated using dynamic light scattering (DLS). It was found that the hexameric form of LbGadB was most stable at pH 6 and in presence of NaCl or KCl. The results indicate that AF4, in combination of various online detectors mentioned above, provides an effective tool for monitoring of oligomerization of LbGadB under different conditions, such as temperature, pH, type of salts, and salt concentrations.
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| 6. |
- Dou, Haiyang, et al.
(author)
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Study on aggregation behavior of low density lipoprotein in hen egg yolk plasma by asymmetrical flow field-flow fractionation coupled with multiple detectors.
- 2016
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In: Food Chemistry. - : Elsevier BV. - 1873-7072 .- 0308-8146. ; 192, s. 228-234
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Journal article (peer-reviewed)abstract
- In this study, asymmetrical flow field-flow fractionation (AF4) coupled online with UV, multiangle light scattering (MALS), and fluorescence (FS) detectors (AF4-UV-MALS-FS) was employed for separation and characterization of egg yolk plasma. AF4 provided separation of three major components of the egg yolk plasma i.e. soluble proteins, low density lipoproteins (LDL) and their aggregates, based on their respective hydrodynamic sizes. Identification of LDL was confirmed by staining the sample with a fluorescent dye, Nile Red. The effect of carrier liquids on aggregation of LDL was investigated. Collected fractions of soluble proteins were characterized using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). Moreover, the effect of heat and enzymatic treatment on egg yolk plasma was investigated. The results suggest that enzymatic treatment with phospholipase A2 (PLA2) significantly enhances the heat stability of LDL. The results show that AF4-UV-MALS-FS is a powerful tool for the fractionation and characterization of egg yolk plasma components.
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| 7. |
- Fuentes, Catalina, et al.
(author)
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Characterization of non-solvent precipitated starch using asymmetrical flow field-flow fractionation coupled with multiple detectors
- 2019
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In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 206, s. 21-28
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Journal article (peer-reviewed)abstract
- Non-solvent precipitated starch (non-SPS) is a novel component for starch-based emulsions. Herein, three non-SPS materials were prepared using ethanol as a precipitant of waxy maize starch granules (WMs). The WMs were either untreated (SP) or pre-treated via acid-hydrolysis (AHSP). In addition, SP was modified using n-octenyl succinic anhydride (OSA), yielding OSASP. This study aimed to investigate the influence of the non-SPS preparation method on the size, molar mass (M), and apparent density (ρapp) of the materials when subjected to different dissolution/dispersion procedures using asymmetrical flow field-flow fractionation (AF4). The results showed that the molar mass, size, and apparent density depended on the type of non-SPS with a decrease in Mw (1.8–9.4 g/mol) and rrms (60–148 nm) upon re-dispersion in different media in the order: SP > OSASP > AHSP. Moreover, different types of non-SPS materials displayed different conformational properties and were stable in aqueous solution at room temperature in the investigated time (24 h).
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| 8. |
- Fuentes, Catalina, et al.
(author)
-
Charge and zeta-potential distribution in starch modified with octenyl succinic anhydride (OSA) determined using electrical asymmetrical flow field-flow fractionation (EAF4)
- 2023
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In: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 657
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Journal article (peer-reviewed)abstract
- Starch modified with octenyl succinic anhydride (OSA) is extensively used due to its emulsifying capacity. Modification with OSA renders the starch surface active but also anionic at intermediate pH. The amount of OSA that is grafted to the starch polymer backbone will influence the functionality. Likewise, it can be expected that the distribution of the substituents over the molar mass distribution will play an important role for the behavior and functionality. Electrical asymmetrical flow field-flow fractionation (EAF4) could provide charge-size dependent separation of samples with different charges. A major advantage is that zeta-potential and size/molar mass distribution can be simultaneously determined. The present study investigates if EAF4 can be used to determine the charge properties over molar mass (or size) distribution of barley starch modified with OSA. The results show that zeta potential and net charge could be estimated over the larger part of the OSA-starch molar mass distribution. Furthermore, the OSA substituents do not appear to be evenly distributed at or close to the “surface” of the polymers, which may have implications for the adsorption behavior and functionality of OSA-starch in emulsions. To the best of our knowledge, this is the first report on applying EAF4 for the characterization of biopolymers and the first time that zeta potential can be determined over the molar mass distribution.
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| 9. |
- Fuentes, Catalina, et al.
(author)
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Comparison between conventional and frit-inlet channels in separation of biopolymers by asymmetric flow field-flow fractionation
- 2019
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In: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654. ; 144:15, s. 4559-4568
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Journal article (peer-reviewed)abstract
- Asymmetric flow field-flow fractionation (AF4) is a separation technique in which a focusing/relaxation step is used after the sample is injected onto the separation channel. During the focusing/relaxation step, the sample is focused by two counter-directed flows. This allows sample components to establish a diffusion-dependent equilibrium concentration profile. The focusing step may, in some cases, cause a loss of sample due to adsorption into the accumulation wall (i.e. the membrane) or due to aggregation of the sample. In addition, the increase in sample concentration during the focusing step may prevent complete relaxation and cause overloading effects. In this study, a modified AF4 channel equipped with a frit inlet (FI-AF4) is utilized, where the sample is relaxed hydrodynamically as it enters to the channel through the frit. The main advantage of the FI-AF4 channel is to omit the focusing step. The FI-AF4 channel could also allow higher injection mass than in a conventional channel while still avoiding overloading. The purpose of the present study is to compare two channels (conventional and FI-AF4 channels) in terms of the plate height (H), resolution (Rs) and the mass recovery for analysis of a mixture of glycogen and pullulan. In addition, waxy maize (WM) starch was used to compare the mass overloading of the two channels. The results show that the type of relaxation method (i.e. focusing or hydrodynamic relaxation) had no significant effect on mass recovery. The resolution (Rs), was higher in the conventional AF4 channel than in the FI-AF4 channel for the separation of glycogen and pullulan. The results also show that it was possible to inject a higher mass of WM starch (i.e. twice the mass) onto the FI-AF4 channel, compared to a conventional AF4 channel, without observing an overloading effect.
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| 10. |
- Fuentes, Catalina, et al.
(author)
-
Fractionation and characterization of starch granules using field-flow fractionation (FFF) and differential scanning calorimetry (DSC)
- 2019
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In: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 411:16, s. 3665-3674
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Journal article (peer-reviewed)abstract
- Starch is one of the main carbohydrates in food; it is formed by two polysaccharides: amylose and amylopectin. The granule size of starch varies with different botanical origins and ranges from less than 1 μm to more than 100 μm. Some physicochemical and functional properties vary with the size of the granule, which makes it of great interest to find an efficient and accurate size-based separation method. In this study, the full-feed depletion mode of split-flow thin cell fractionation (FFD-SF) was employed for a size-based fractionation of two types of starch granules (corn and potato) on a large scale. The fractionation efficiency (FE) of fraction-a for corn and potato granules was 98.4 and 99.4%, respectively. The FFD-SF fractions were analyzed using optical microscopy (OM) and gravitational field-flow fractionation (GrFFF). The respective size distribution results were in close agreement for the corn starch fractions, while they were slightly different for the potato starch fractions. The thermal properties of FFD-SF fractions were analyzed, and the results for the potato starch showed that the peak temperature of gelatinization (T p ) slightly decreases as the size of the granules increases. Additionally, the enthalpy of gelatinization (ΔH) increases when the granule size increases and shows negative correlation with the gelatinization range (ΔT).
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