| 1. |
- Bilalov, Azat, et al.
(författare)
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DNA with amphiphilic counterions: tuning colloidal DNA with cyclodextrin
- 2012
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 8:18, s. 4988-4994
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Tidskriftsartikel (refereegranskat)abstract
- DNA compaction in vitro can be controlled by lipids. Cyclodextrins can disperse lipids in the form of water soluble inclusion complexes, thus tuning their self-assembly. To progress in the fundamental understanding of double-stranded (ds) DNA-lipid-cyclodextrin interactions, the aqueous phase behavior of a cationic surfactant (dodecyltrimethylammonium, DTA)-dsDNA compound in the presence of cyclodextrin (hydroxypropyl-beta-cyclodextrin, HPbCD, or beta-cyclodextrin, beta CD) was investigated. beta CD has a low water solubility due to the formation of stable crystals. The more hydrophobic HPbCD, on the other hand, is highly water soluble because the bulky HP substitution destabilizes the crystalline state. Both beta CD and HP beta CD form strong inclusion complexes with DTA, with an essentially infinite binding constant, and the DNA self-assembly behavior is controlled by the molar ratio R [DTA]/[CD], in addition to the DNA concentration. DTA-DNA can be solubilized in the isotropic liquid phase of water and HPbCD when R <= 1. This phase is micelle free and from the sharp phase boundary at R 1 it is concluded that HPbCD does not associate with DNA, only with DTA. Increasing the DTA-DNA concentration, keeping R < 1, leads to the formation of a liquid crystal with 2D hexagonally ordered DNA. With a further increase of the DTA-DNA and R > 1.5-2, a second, novel, anisotropic phase is formed that we identify as having a tetragonal lattice. In this phase, the DNA duplexes are still parallel but with a simple square rather than a hexagonal packing. The periodicity in the direction of the DNA duplexes is coupled to the DNA pitch length, 3.3 nm. With beta CD, the phase behavior is less rich because of the poor water solubility of the cyclodextrin. Here, only a very small hexagonal phase region is formed in the center of the ternary phase diagram, with R similar or equal to 1.
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| 2. |
- Carlstedt, Jonas, et al.
(författare)
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Aqueous phase behavior of polyelectrolytes with amphiphilic counterions modulated by cyclodextrin: the role of polyion flexibility.
- 2012
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Ingår i: Physical chemistry chemical physics : PCCP. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 14:27, s. 9574-9577
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Tidskriftsartikel (refereegranskat)abstract
- Polyelectrolytes with amphiphilic counterions, PEACs, are water insoluble because the amphiphiles self-assemble into highly charged micelles that strongly associate with the equally highly charged polyions. However, in the presence of water soluble cyclodextrins (CDs) that form inclusion complexes with the amphiphiles and prevent micellization, PEACs become soluble as the dispersed amphiphiles behave essentially as simple monovalent counterions. In this paper, we illustrate, by example, how strongly the ternary phase behavior of PEAC:CD:water depends on the polyion flexibility; for a highly flexible polyion (polyacrylate) the amphiphilic aggregates dictate the phase behavior, whereas a much stiffer polyion (DNA) itself dictates liquid crystalline ordering.
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| 3. |
- Carlstedt, Jonas, et al.
(författare)
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Condensation and decondensation of DNA by cationic surfactant, spermine, or cationic surfactant–cyclodextrin mixtures : macroscopic phase behavior, aggregate properties, and dissolution mechanisms
- 2012
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:21, s. 7976-7989
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Tidskriftsartikel (refereegranskat)abstract
- The macroscopic phase behavior and other physicochemical properties of dilute aqueous mixtures of DNA and the cationic surfactant hexadecyltrimethylammounium bromide (CTAB), DNA and the polyamine spermine, or DNA, CTAB, and (2-hydroxypropyl)-β-cyclodextrin (2HPβCD) were investigated. When DNA is mixed with CTAB we found, with increasing surfactant concentration, (1) free DNA coexisting with surfactant unimers, (2) free DNA coexisting with aggregates of condensed DNA and CTAB, (3) a miscibility gap where macroscopic phase separation is observed, and (4) positively overcharged aggregates of condensed DNA and CTAB. The presence of a clear solution beyond the miscibility gap cannot be ascribed to self-screening by the charges from the DNA and/or the surfactant; instead, hydrophobic interactions among the surfactants are instrumental for the observed behavior. It is difficult to judge whether the overcharged mixed aggregates represent an equilibrium situation or not. If the excess surfactant was not initially present, but added to a preformed precipitate, redissolution was, in consistency with previous reports, not observed; thus, kinetic effects have major influence on the behavior. Mixtures of DNA and spermine also displayed a miscibility gap; however, positively overcharged aggregates were not identified, and redissolution with excess spermine can be explained by electrostatics. When 2HPβCD was added to a DNA–CTAB precipitate, redissolution was observed, and when it was added to the overcharged aggregates, the behavior was essentially a reversal of that of the DNA–CTAB system. This is attributed to an effectively quantitative formation of 1:1 2HPβCD–surfactant inclusion complexes, which results in a gradual decrease in the concentration of effectively available surfactant with increasing 2HPβCD concentration.
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| 4. |
- Carlstedt, Jonas, et al.
(författare)
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Cyclodextrin-Surfactant Coassembly Depends on the Cyclodextrin Ability To Crystallize.
- 2012
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:5, s. 2387-2394
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Tidskriftsartikel (refereegranskat)abstract
- Full equilibrium phase diagrams are presented for two ternary systems composed of the cationic surfactant dodecyltrimethylammonium bromide (DTAB), water (D(2)O), and a cyclodextrin, either β-cyclodextrin (β-CD) or (2-hydroypropyl)-β-cyclodextrin (2HPβCD). (2)H NMR, SAXS, WAXS, and visual examination were used to determine the phase boundaries and characterize the nature of the phases formed. Additionally, diffusion (1)H NMR was used to investigate parts of the diagrams. The water solubility of 2HPβCD is 80% (w/w), whereas it is only 1.85% (w/w) for β-CD. Solubility increases for both species upon complexation with DTAB; while the increase is minute for 2HPβCD, it is dramatic for β-CD. Both systems displayed an isotropic liquid solution (L(1)) one-phase region, the extension of which differs extensively between the two systems. Additionally, the DTAB:2HPβCD:water system also comprised a normal hexagonal (H(1)) area, which was not found for the DTAB:β-CD:water system. In the DTAB:β-CD:water system, on the other hand, we found cocrystallization of DTAB and β-CD. From this work we conclude that DTAB and CD molecules form 1:1 inclusion complexes with high affinities. Moreover, we observed indications of an association of 2HPβCD to DTAB micelles in the isotropic solution phase, which was not the case for β-CD and DTAB micelles. This is, to our knowledge, the first complete phase diagrams of surfactant-CD mixtures; as a novel feature it includes the observation of cocrystallization at high concentrations.
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| 5. |
- Carlstedt, Jonas, et al.
(författare)
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Hydration and the phase diagram of acid hydrolyzed potato starch
- 2014
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 112, s. 569-577
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Tidskriftsartikel (refereegranskat)abstract
- We investigated hydration of acid hydrolyzed potato starch (maltodextrin) employing a multi-method approach. In particular, synchrotron radiation X-ray scattering and differential scanning calorimetry were used, and, for the first time, the material was investigated with sorption calorimetry and a newly developed quartz crystal microbalance with humidity scanning. The dry starch was found to be in an amorphous state. During hydration it exhibits a glass transition in both bulk and thin film samples, followed by an exothermic event where the starch crystallized. Recrystallized bulk samples displayed neither a pronounced glass transition nor crystallization upon hydration whereas both events occurred in thin film samples. The hydration-driven crystallization resulted in an X-ray pattern consistent with the coexistence of A and B type crystallites; however, at higher water concentrations only the B form occurred. The results were used to construct the first ever acid hydrolyzed starch–water phase diagram.
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| 6. |
- Carlstedt, Jonas, et al.
(författare)
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Release of DNA from surfactant complexes induced by 2-hydroxypropyl-beta-cyclodextrin.
- 2010
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 1879-0003 .- 0141-8130. ; 46:2, s. 153-158
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Tidskriftsartikel (refereegranskat)abstract
- Decompaction of DNA-CTA self-assembled complexes by 2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD) was studied and the results were compared with beta-CD. Different degrees of 2-HP substitution (0.6, 0.8 and 1.0, respectively) were used and the decompaction was successful with all degrees of substitution. Fluorescence microscopy, steady state fluorescence spectroscopy, density and sound velocity measurements, thermal melting and circular dichroism were used. Compared to previous work using alpha- and beta-CD, the fluorescence spectroscopy results showed that the 2-HP-substituted CDs more efficiently released DNA into solution. Furthermore, dissociation of macroscopically phase separated DNA-CTA complexes was achieved upon addition of 2-HP-beta-CD and the results gave strong indications on the non-equilibrium nature of the system. The globule-to-coil transition was not found to proceed through a coexistence region, which seems to be a general phenomenon in DNA decompaction using CDs.
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| 7. |
- Carlstedt, Jonas, et al.
(författare)
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Understanding Starch Gelatinization : the Phase Diagram Approach
- 2015
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 129, s. 62-69
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Tidskriftsartikel (refereegranskat)abstract
- By constructing a detailed phase diagram for the potato starch–water system based on data from optical microscopy, synchrotron X-ray scattering and differential scanning calorimetry, we show that gelatinization can be interpreted in analogy with a eutectic transition. The phase rule explains why the temperature of the gelatinization transition (G) is independent on water content. Furthermore, the melting (M1) endotherm observed in DSC represents a liquidus line; the temperature for this event increases with increasing starch concentration. Both the lamellar spacing and the inter-helix distance were observed to decrease with increasing starch content for starch concentrations between approximately 65 wt% and 75 wt%, while the inter-helix distance continued decreasing upon further dehydration. Understanding starch gelatinization has been a longstanding challenge. The novel approach presented here shows interpretation of this phenomenon from a phase equilibria perspective.
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| 8. |
- Gonzalez Perez, Alfredo, et al.
(författare)
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Cyclodextrins in DNA decompaction.
- 2010
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Ingår i: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 1873-4367 .- 0927-7765. ; 76:1, s. 20-27
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Tidskriftsartikel (refereegranskat)abstract
- Individual T4DNA molecules, previously compacted by using a cationic surfactant (cetyltrimethylammonium bromide, CTAB), were successfully decompacted by the addition of an appropriate concentration of either alpha-cyclodextrin or beta-cyclodextrin (alpha-CD and beta-CD, respectively) due to the formation of inclusion complexes with the surfactant. The process was shown to be a non first-order transition from globules to coils. Density and sound velocity measurements as well as steady state fluorescence spectroscopy have confirmed the approximate CD concentration at which the globule-to-coil transition occurs. Phase maps of the DNA-CTA-CD systems were produced and the CTAB concentration range at which decompaction can be achieved was determined. Evidences for DNA-CD interaction were found, however, its nature and influence on the decompaction process was not yet determined.
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| 9. |
- Spégel, Peter, et al.
(författare)
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Continuous full filling capillary electrochromatography: Nanoparticle synthesis and evaluation
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1154:1-2, s. 379-385
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Tidskriftsartikel (refereegranskat)abstract
- Reversed phase continuous full filling capillary electrochromatography with electrospray ionisation mass spectrometric detection was performed with highly sulphated poly [styrene-co-(lauryl methacrylate)-co-(divinylbenzene)] nanoparticles. The nanoparticles that contained a hydrophobic core and a hydrophilic surface were prepared in a one step synthesis using soap free emulsion polymerisation. By changing the concentration of monomers, the polymerisation temperature, and the polarity of the dispersive phase, the size of the nanoparticles could be controlled. With the optimised conditions, nanoparticles with an average size of 157 nm were obtained. These nanoparticles were dispersed in the background electrolyte and used for reversed phase continuous full filling. An orthogonal electrospray ionisation interface was used to separate the eluting nanoparticles from the eluting analytes prior to mass spectrometry detection. Compared to previous studies on reversed phase continuous full filling, the retention, the separation efficiency, and the resolution of a homologous series of dialkyl phthalates were greatly improved.
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| 10. |
- Viberg, Peter, et al.
(författare)
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Continuous full filling capillary electrochromatography: Chromatographic performance and reproducibility
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1154:1-2, s. 386-389
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Tidskriftsartikel (refereegranskat)abstract
- Continuous full filling capillary electrochromatography with nanoparticles as pseudostationary phase interfaced with electrospray ionisation mass spectrometric detection was used for reversed phase separations with very high separation efficiency. Several batches of nanoparticles were synthesised and their electrochromatographic performance were evaluated. Different parameters, such as repeatability, reproducibility, limit of detection, and peak asymmetry, were investigated yielding excellent results. The stability of the system over wide pH ranges and over time was found to be excellent. Very high separation efficiencies with over 1.1 million theoretical plates per metre were obtained. The limit of detection for the investigated dialkyl phthalates was approximately 1.0 mu mol L-1, corresponding to 3-5 fmol injected. After preparation, nanoparticle suspensions could be used without further treatment for at least an entire working day with maintained chromatographic qualities. (c) 2007 Elsevier B.V. All rights reserved.
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