| 1. |
- Choi, Jaeyeong, et al.
(författare)
-
Separation and zeta-potential determination of proteins and their oligomers using electrical asymmetrical flow field-flow fractionation (EAF4)
- 2020
-
Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1633
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 2. |
- Fuentes, Catalina, et al.
(författare)
-
Application of asymmetric flow field-flow fractionation (AF4) and multiangle light scattering (MALS) for the evaluation of changes in the product molar mass during PVP-b-PAMPS synthesis
- 2018
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 410:16, s. 3757-3767
-
Tidskriftsartikel (refereegranskat)abstract
- The use of polymers for the delivery of drugs has increased dramatically in the last decade. To ensure the desired properties and functionality of such substances, adequate characterization in terms of the molar mass (M) and size is essential. The aim of this study was to evaluate the changes in the M and size of PVP-b-PAMPS when the amounts of the synthesis reactants in the two-step radical reaction were varied. The determination of the M and size distributions was performed by an asymmetric flow field-flow fractionation (AF4) system connected to multiangle light scattering (MALS) and differential refractive index (dRI) detectors. The results show that the M of the polymers varies depending on the relative amounts of the reactants and that AF4-MALS-dRI is a powerful characterization technique for analyzing polymers. Using AF4, it was possible to separate the product of the first radical reaction (PVP-CTA) into two populations. The first population had an elongated, rod-like or random coil conformation, and the second had a conformation corresponding to homogeneous spheres or a microgel structure. PVP-b-PAMPS had only one population, which had a rod-like conformation. The molar masses of PVP-CTA and PVP-b-PAMPS found in this study were higher than those reported in previous studies.
|
|
| 3. |
- Fuentes, Catalina, et al.
(författare)
-
Characterization of molecular properties of wheat starch from three different types of breads using asymmetric flow field-flow fractionation (AF4)
- 2019
-
Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146. ; 298
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, molecular properties of wheat starch from three different types of breads were analyzed using asymmetric flow field-flow (AF4) connected to multi-angle light scattering (MALS) and differential refractive index (dRI) detectors. This analysis allowed the determination of molecular properties, i.e. molar mass (M), root-mean-square radius (rrms), apparent density (ρapp) and conformation. Complementary analyses, such as resistant starch and amylose content, were also performed. The results show that wheat starch extracted from breads can have different properties reflected in changes in M, rrms and ρapp. In addition, the results suggest that some of the changes in molecular properties may be related to the presence of resistant starch.
|
|
| 4. |
- Fuentes, Catalina, et al.
(författare)
-
Characterization of non-solvent precipitated starch using asymmetrical flow field-flow fractionation coupled with multiple detectors
- 2019
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 206, s. 21-28
-
Tidskriftsartikel (refereegranskat)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).
|
|
| 5. |
- Fuentes, Catalina
(författare)
-
Characterization of Starch Using Flow Field-Flow Fractionation Techniques
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To improve the properties and functionality of starch, it is important to understand the physicochemical and structural characteristics as raw material, after being modified to increase its characteristics and/or during changes due to the processing conditions. For this reason, the objective of the present thesis is to improve the understanding of characteristics and molecular properties like molar mass (M), root-mean-square radius (rrms) and their relation to other physicochemical properties of starch extracted from different sources. Due to its complex structure, however, the analysis of starch can be challenging and few techniques are suitable. Nevertheless, some sub-techniques of the field-flow fractionation (FFF) family, especially asymmetric flow field-flow fractionation (AF4) have been shown to be appropriate for this task. Regarding the different FFF techniques, large-scale full-feed depletion mode of split flow thin cell fractionation (FFD-SF) was used as a preparative fractionation of corn and potato starch granules showing to be a useful technique for this task. In addition, the fractions obtained by large-scale FFD-SF were analyzed using optical microscopy (OM) and gravitational field-flow fractionation (GrFFF) which have been shown to be also suitable methods for determining the average size diameter (davg), with good agreement between these two techniques. Moreover, some slight improvements related to the analysis of starch as a polymer in solution using AF4 were made. First, with the use of a modified channel known as frit inlet (FI-AF4). It has been shown that almost double the amount of mass can be injected into the FI-AF4 channel in comparison with the conventional channel, without observing overloading effects. Second, the downturn phenomena that could be observed in the analysis of starch and/or other polymers, which is usually considered as an artifact that occurs during the analysis, was shown to be a result of co-elution of species with similar M but different conformation.Otherwise, physicochemical properties such as granule size, crystallinity, pasting properties among others as well as structural properties such as rrms, weight-average molar mass (Mw) and apparent density (ρapp) were analyzed in five different starches from Andean crops (three grains and two roots). To evaluate the relation between all these properties a statistical analysis was performed and a model was proposed that relates pasting properties i.e. peak viscosity and final viscosity with ρapp, gelatinization enthalpy, granule size and amylose content. Additionally, thermal properties were examined in relation to the granule size. For this, potato starch and its fractions (obtained using large-scale FFD-SF), as well as Andean roots, chosen for their similarity in botanical origin, were analyzed showing a correlation between enthalpy and granule size. Another factor affecting the thermal properties seems to be the amylose content.In the analysis of starch nanocomponents, it seems that the procedure used for obtaining non-solvent precipitated starch (non-SPS) resulted in new materials with amorphous structures that do not show particle characteristics when in solution, which suggests that designating these as nanoparticles might not be appropriate. Finally, in the analysis of starch extracted from different types of breads, the results show that M and size are affected by the baking process. In the case of breads, α-amylase enzyme was added. M and size decreased while the degree of branching (DB) and the number of reducing ends H-1(β-r) and H-1(α-r) increased. Furthermore, in starches extracted from Bolivian breads, it seems that the content of water during the preparation of the dough could affect the production of resistant starch.
|
|
| 6. |
- Fuentes, Catalina, et al.
(författare)
-
Charge and zeta-potential distribution in starch modified with octenyl succinic anhydride (OSA) determined using electrical asymmetrical flow field-flow fractionation (EAF4)
- 2023
-
Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 657
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 7. |
- Fuentes, Catalina, et al.
(författare)
-
Comparison between conventional and frit-inlet channels in separation of biopolymers by asymmetric flow field-flow fractionation
- 2019
-
Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654. ; 144:15, s. 4559-4568
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 8. |
- Fuentes, Catalina, et al.
(författare)
-
Fractionation and characterization of starch granules using field-flow fractionation (FFF) and differential scanning calorimetry (DSC)
- 2019
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 411:16, s. 3665-3674
-
Tidskriftsartikel (refereegranskat)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).
|
|
| 9. |
- Fuentes, Catalina, et al.
(författare)
-
Physicochemical and structural properties of starch from five Andean crops grown in Bolivia
- 2019
-
Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130. ; 125, s. 829-838
-
Tidskriftsartikel (refereegranskat)abstract
- Three Andean grains - amaranth (Amaranthus caudatus), quinoa (Chenopodium quinoa), canihua (Chenopodium pallidicaulle) - and two Andean roots starches - achira (Canna indica), maca (Lepidium meyenii) - were studied. Physicochemical properties such as granule size, crystallinity, pasting properties among other as well as structural properties such as root-mean-square radius (rrms), weight-average molar mass (Mw) and apparent density (ρapp) were analyzed in order to evaluate the relation between them. Grains were similar in most of their characteristics as roots in their i.e. granule size, shape, type of crystallinity, Mw and rrms varied according to botanical source. The starch granules from grains were in a narrow diameter range (0.5 to 2 μm) and displayed A-type X-ray diffraction pattern (XRD). Roots starch had a wide granule diameter range (1 to 100 μm) and displayed a B-type XRD. The amylose content varied between 0 and 48% where amaranth had the lowest value and achira had the highest. Furthermore, quinoa and canihua starches had very low breakdown in pasting properties, indicating high stability during cooking. A model is proposed that relates pasting properties i.e. peak viscosity and final viscosity with ρapp, gelatinization enthalpy, granule size and amylose content.
|
|
| 10. |
- Fuentes, Catalina, et al.
(författare)
-
The effect of baking and enzymatic treatment on the structural properties of wheat starch
- 2016
-
Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146. ; 213, s. 768-774
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, bread was baked with and without the addition of α-amylase. Starch was extracted from the baked bread and its molecular properties were characterized using 1H NMR and asymmetric flow field-flow fractionation (AF4) connected to multi-angle light scattering (MALS) and other detectors. The approach allows determination of molar mass, root- mean-square radius and apparent density as well as the average degree of branching of amylopectin. The results show that starch size and structure is affected as a result of the baking process. The effect is larger when α-amylase is added. The changes include both a decrease molar mass and size as well as an increase in apparent density. Moreover, an increase in average degree of branching and the number of reducing ends H-1(β-r) and H-1(α-r) can be observed.
|
|
