| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Bello, Gianluca, et al.
(författare)
-
Characterization of the aggregates formed by various bacterial lipopolysaccharides in solution and upon interaction with antimicrobial peptides
- 2015
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:2, s. 741-751
-
Tidskriftsartikel (refereegranskat)abstract
- The biophysical analysis of the aggregates formed by different chemotypes of bacterial lipopolysaccharides (LPS) before and after challenge by two different anti-endotoxic antimicrobial peptides (LL37 and bovine lactoferricin), was performed in order to determine their effect on the morphology of LPS aggregates. Small-angle neutron scattering (SANS) and cryogenic transmission electron microscopy (cryoTEM) were used to examine the structures formed by both smooth and rough LPS chemotypes and the effect of the peptides, by visualization of the aggregates and analysis of the scattering data by means of both mathematical approximations and defined models. The data showed that the structure of LPS determines the morphology of the aggregates and inuences the binding activity of both peptides. The morphologies of the worm-like micellar aggregates formed by the smooth LPS were relatively unaltered by the presence of the peptides due to their pre-existing high degree of positive curvature being little affected by their association with either peptide. On the other hand the aggregates formed by the rough LPS chemotypes, showed marked morphological changes from lamellar structures to ordered micellar networks, induced by the increase in positive curvature engendered upon association with the peptides. The combined use of cryoTEM and SANS proved to be a very useful tool for studying the aggregation properties of LPS in solution at biologically relevant concentrations.
|
|
| 7. |
- Berntsson, Oskar, et al.
(författare)
-
A setup for millisecond time-resolved X-ray solution scattering experiments at the CoSAXS beamline at the MAX IV Laboratory
- 2022
-
Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 29, s. 555-562
-
Tidskriftsartikel (refereegranskat)abstract
- The function of biomolecules is tightly linked to their structure, and changes therein. Time-resolved X-ray solution scattering has proven a powerful technique for interrogating structural changes and signal transduction in photoreceptor proteins. However, these only represent a small fraction of the biological macromolecules of interest. More recently, laser-induced temperature jumps have been introduced as a more general means of initiating structural changes in biomolecules. Here we present the development of a setup for millisecond time-resolved X-ray solution scattering experiments at the CoSAXS beamline, primarily using infrared laser light to trigger a temperature increase, and structural changes. We present results that highlight the characteristics of this setup along with data showing structural changes in lysozyme caused by a temperature jump. Further developments and applications of the setup are also discussed.
|
|
| 8. |
- Bogdanova, Ekaterina, et al.
(författare)
-
Lysozyme-Sucrose Interactions in the Solid State : Glass Transition, Denaturation, and the Effect of Residual Water
- 2023
-
Ingår i: Molecular Pharmaceutics. - : American Chemical Society. - 1543-8384 .- 1543-8392. ; 20:9, s. 4664-
-
Tidskriftsartikel (refereegranskat)abstract
- The freeze-drying of proteins, along with excipients, offers a solution for increasing the shelf-life of protein pharmaceuticals. Using differential scanning calorimetry, thermogravimetric analysis, sorption calorimetry, and synchrotron small-angle X-ray scattering (SAXS), we have characterized the properties at low (re)hydration levels of the protein lysozyme, which was freeze-dried together with the excipient sucrose. We observe that the residual moisture content in these samples increases with the addition of lysozyme. This results from an increase in equilibrium water content with lysozyme concentration at constant water activity. Furthermore, we also observed an increase in the glass transition temperature (Tg) of the mixtures with increasing lysozyme concentration. Analysis of the heat capacity step of the mixtures indicates that lysozyme does not participate in the glass transition of the sucrose matrix; as a result, the observed increase in the Tg of the mixtures is the consequence of the confinement of the amorphous sucrose domains in the interstitial space between the lysozyme molecules. Sorption calorimetry experiments demonstrate that the hydration behavior of this formulation is similar to that of the pure amorphous sucrose, while the presence of lysozyme only shifts the sucrose transitions. SAXS analysis of amorphous lysozyme-sucrose mixtures and unfolding of lysozyme in this environment show that prior to unfolding, the size and shape of lysozyme in a solid sucrose matrix are consistent with its native state in an aqueous solution. The results obtained from our study will provide a better understanding of the low hydration behavior of protein-excipient mixtures and support the improved formulation of biologics. © 2023 The Authors.
|
|
| 9. |
- Brownstein, Catherine A., et al.
(författare)
-
An international effort towards developing standards for best practices in analysis, interpretation and reporting of clinical genome sequencing results in the CLARITY Challenge
- 2014
-
Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 15:3, s. R53-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: There is tremendous potential for genome sequencing to improve clinical diagnosis and care once it becomes routinely accessible, but this will require formalizing research methods into clinical best practices in the areas of sequence data generation, analysis, interpretation and reporting. The CLARITY Challenge was designed to spur convergence in methods for diagnosing genetic disease starting from clinical case history and genome sequencing data. DNA samples were obtained from three families with heritable genetic disorders and genomic sequence data were donated by sequencing platform vendors. The challenge was to analyze and interpret these data with the goals of identifying disease-causing variants and reporting the findings in a clinically useful format. Participating contestant groups were solicited broadly, and an independent panel of judges evaluated their performance. Results: A total of 30 international groups were engaged. The entries reveal a general convergence of practices on most elements of the analysis and interpretation process. However, even given this commonality of approach, only two groups identified the consensus candidate variants in all disease cases, demonstrating a need for consistent fine-tuning of the generally accepted methods. There was greater diversity of the final clinical report content and in the patient consenting process, demonstrating that these areas require additional exploration and standardization. Conclusions: The CLARITY Challenge provides a comprehensive assessment of current practices for using genome sequencing to diagnose and report genetic diseases. There is remarkable convergence in bioinformatic techniques, but medical interpretation and reporting are areas that require further development by many groups.
|
|
| 10. |
- Caporaletti, Francesca, 1990-
(författare)
-
MYC and MexR interactions with DNA : a Small Angle Scattering perspective
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Protein-DNA complexes govern transcription, that is, the cellular mechanism that converts the information stored in the DNA into proteins. These complexes need to be highly dynamic to respond to external factors that regulate their functions in agreement with what the cells need at that time. Macromolecular X-ray crystallography is very useful for structural studies of large molecular assemblies, but its general application is limited by the difficulties in crystallising highly dynamic and transient complexes. Furthermore, crystal lattices constrain the macromolecular conformation and do not entirely reveal the conformational ensemble adopted by protein-DNA complexes in the solution.Small-Angle X-Ray Scattering (SAXS) and Small-Angle Neutron Scattering (SANS) are two complementary techniques known jointly as Small-angle Scattering (SAS). SAS is a powerful tool for analysing the shape and changes of molecules in solution in their native state. It is beneficial if the variability of conformation or disorder complements high-resolution methods such as NMR or crystallography. With SANS, we can explore non-crystallisable protein-DNA complexes in solution without restrictions of artificially symmetrised DNA and limitations of a protein sequence. Neutrons are well-suited probes for studying protein-DNA complexes for the capability of the neutrons to scatter common atoms in biomolecules differentially and can thereby distinguish between hydrogen and deuterium. Together with varying the solvent deuterium ratio, the contrast variation approach can reveal shapes of distinct components within a macromolecular complex.The goal of this thesis is to explore unchartered territories of regulatory protein-DNA interactions by studying such complexes by SAS, with a specific focus on the flexibility of the complexes. In my study of the MexR-DNA complex, I try to elucidate the molecular mechanism by which the MexR repressor regulates the expression of the MexAB-OPrM efflux pump through DNA binding. This pump is one of the multidrug-resistant tools of the pathogen Pseudomonas Aeruginosa (P. Aer.). It can extrude antibacterial drugs from the bacteria enabling them to survive in hostile environments. In the second project, I strive to explore the MYC:MAX:DNA complex. This heterodimer assembly functions as a central hub in cellular growth control by regulating many biological functions, including proliferation, apoptosis, differentiation and transformation. Overexpression or deregulation of MYC is observed in up to 70% of human aggressive cancer forms, including prostate and breast cancers. By combining SAS with biophysical methods, the work presented in this thesis reveals novel information on the shape and dynamics of biomolecular assemblies critical to health and disease.This thesis comprises five chapters, each dealing with a different aspect of the work in those years. The first chapter introduces the reader to the motivations of this research, and it will give the reader a brief state of the art of the two projects. In the second chapter, I will give you all the theoretical instruments to understand better all the methods used in this thesis, I write first to provide an overview regarding the proteins and their capability to bind other macromolecules. I then will exploit the basics of the small-angle technique, focusing on the neutron contrast variation: the fundamental technique used throughout this thesis and the ab-initio modelling.In the third chapter, Methods, I will discuss the SAS measurements and the requirements for the experiments themselves, the procedure for the data reduction and the data processing and analysis to obtain the structural information.The fourth chapter is a summary of the results of the submitted papers and my contributions:Small-angle X-ray and neutron scattering of MexR and its complex with DNA supports a conformational selection binding modelResolving the DNA interaction of the MexR antibiotic resistance regulatory proteinUpgraded D22 SEC-SANS set-up dedicated to the biology communitySAS studies on the regulation of MYC303:MAX:DNA and MAX:MAX:DNA binding in cancer.
|
|
| 11. |
- Choi, Jaeyeong, et al.
(författare)
-
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
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:11
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 12. |
- Correa, Yubexi, et al.
(författare)
-
Lipid exchange of apolipoprotein A-I amyloidogenic variants in reconstituted high-density lipoprotein with artificial membranes
- 2024
-
Ingår i: Protein Science. - : John Wiley & Sons. - 0961-8368 .- 1469-896X. ; 33:5
-
Tidskriftsartikel (refereegranskat)abstract
- High-density lipoproteins (HDLs) are responsible for removing cholesterol from arterial walls, through a process known as reverse cholesterol transport. The main protein in HDL, apolipoprotein A-I (ApoA-I), is essential to this process, and changes in its sequence significantly alter HDL structure and functions. ApoA-I amyloidogenic variants, associated with a particular hereditary degenerative disease, are particularly effective at facilitating cholesterol removal, thus protecting carriers from cardiovascular disease. Thus, it is conceivable that reconstituted HDL (rHDL) formulations containing ApoA-I proteins with functional/structural features similar to those of amyloidogenic variants hold potential as a promising therapeutic approach. Here we explored the effect of protein cargo and lipid composition on the function of rHDL containing one of the ApoA-I amyloidogenic variants G26R or L174S by Fourier transformed infrared spectroscopy and neutron reflectometry. Moreover, small-angle x-ray scattering uncovered the structural and functional differences between rHDL particles, which could help to comprehend higher cholesterol efflux activity and apparent lower phospholipid (PL) affinity. Our findings indicate distinct trends in lipid exchange (removal vs. deposition) capacities of various rHDL particles, with the rHDL containing the ApoA-I amyloidogenic variants showing a markedly lower ability to remove lipids from artificial membranes compared to the rHDL containing the native protein. This effect strongly depends on the level of PL unsaturation and on the particles' ultrastructure. The study highlights the importance of the protein cargo, along with lipid composition, in shaping rHDL structure, contributing to our understanding of lipid-protein interactions and their behavior.
|
|
| 13. |
- Correa, Yubexi, et al.
(författare)
-
Lipid exchange of apolipoprotein A-I amyloidogenic variants in reconstituted high-density lipoprotein with artificial membranes
- 2024
-
Ingår i: Protein Science. - : John Wiley & Sons. - 0961-8368 .- 1469-896X. ; 33:5
-
Tidskriftsartikel (refereegranskat)abstract
- High-density lipoproteins (HDLs) are responsible for removing cholesterol from arterial walls, through a process known as reverse cholesterol transport. The main protein in HDL, apolipoprotein A-I (ApoA-I), is essential to this process, and changes in its sequence significantly alter HDL structure and functions. ApoA-I amyloidogenic variants, associated with a particular hereditary degenerative disease, are particularly effective at facilitating cholesterol removal, thus protecting carriers from cardiovascular disease. Thus, it is conceivable that reconstituted HDL (rHDL) formulations containing ApoA-I proteins with functional/structural features similar to those of amyloidogenic variants hold potential as a promising therapeutic approach. Here we explored the effect of protein cargo and lipid composition on the function of rHDL containing one of the ApoA-I amyloidogenic variants G26R or L174S by Fourier transformed infrared spectroscopy and neutron reflectometry. Moreover, small-angle x-ray scattering uncovered the structural and functional differences between rHDL particles, which could help to comprehend higher cholesterol efflux activity and apparent lower phospholipid (PL) affinity. Our findings indicate distinct trends in lipid exchange (removal vs. deposition) capacities of various rHDL particles, with the rHDL containing the ApoA-I amyloidogenic variants showing a markedly lower ability to remove lipids from artificial membranes compared to the rHDL containing the native protein. This effect strongly depends on the level of PL unsaturation and on the particles' ultrastructure. The study highlights the importance of the protein cargo, along with lipid composition, in shaping rHDL structure, contributing to our understanding of lipid–protein interactions and their behavior.
|
|
| 14. |
- Dubackic, Marija, et al.
(författare)
-
On the Cluster Formation of α-Synuclein Fibrils
- 2021
-
Ingår i: Frontiers in Molecular Biosciences. - : Frontiers Media SA. - 2296-889X. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- The dense accumulation of α-Synuclein fibrils in neurons is considered to be strongly associated with Parkinson’s disease. These intracellular inclusions, called Lewy bodies, also contain significant amounts of lipids. To better understand such accumulations, it should be important to study α-Synuclein fibril formation under conditions where the fibrils lump together, mimicking what is observed in Lewy bodies. In the present study, we have therefore investigated the overall structural arrangements of α-synuclein fibrils, formed under mildly acidic conditions, pH = 5.5, in pure buffer or in the presence of various model membrane systems, by means of small-angle neutron scattering (SANS). At this pH, α-synuclein fibrils are colloidally unstable and aggregate further into dense clusters. SANS intensities show a power law dependence on the scattering vector, q, indicating that the clusters can be described as mass fractal aggregates. The experimentally observed fractal dimension was d = 2.6 ± 0.3. We further show that this fractal dimension can be reproduced using a simple model of rigid-rod clusters. The effect of dominatingly attractive fibril-fibril interactions is discussed within the context of fibril clustering in Lewy body formation.
|
|
| 15. |
- Eves, Ben J., et al.
(författare)
-
Elongation rate and average length of amyloid fibrils in solution using isotope-labelled small-angle neutron scattering
- 2021
-
Ingår i: RSC Chemical Biology. - : Royal Society of Chemistry (RSC). - 2633-0679. ; 2:4, s. 1232-1238
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a solution method that allows both elongation rate and average fibril length of assembling amyloid fibrils to be estimated. The approach involves acquisition of real-time neutron scattering data during the initial stages of seeded growth, using contrast matched buffer to make the seeds effectively invisible to neutrons. As deuterated monomers add on to the seeds, the labelled growing ends give rise to scattering patterns that we model as cylinders whose increase in length with time gives an elongation rate. In addition, the absolute intensity of the signal can be used to determine the number of growing ends per unit volume, which in turn provides an estimate of seed length. The number of ends did not change significantly during elongation, demonstrating that any spontaneous or secondary nucleation was not significant compared with growth on the ends of pre-existing fibrils, and in addition providing a method of internal validation for the technique. Our experiments on initial growth of alpha synuclein fibrils using 1.2 mg ml-1 seeds in 2.5 mg ml-1 deuterated monomer at room temperature gave an elongation rate of 6.3 ± 0.5 Å min-1, and an average seed length estimate of 4.2 ± 1.3 μm. This journal is
|
|
| 16. |
- Fornell, Anna, et al.
(författare)
-
A microfluidic platform for SAXS measurements of liquid samples
- 2022
-
Konferensbidrag (refereegranskat)abstract
- Small-angle X-ray scattering (SAXS) is a technique that can measure the size and shape of small particles such as proteins and nanoparticles using X-rays. At MAX IV, we are developing a microfluidic sample delivery platform to measure liquid samples containing proteins under flow using SAXS. One of the main advantages of using microfluidics is that the sample is continuously flowing, thus minimizing the risk of radiation damage as the sample is continuously refreshed. Other advantages include low sample volume and the possibility to study dynamic processes, e.g. mixing. To obtain good SAXS signals, the X-ray properties of the chip material are essential. The microfluidic chip must have low attenuation of X-rays, low background scattering, and high resistance to X-ray-induced damage, and preferably be low cost and easy to fabricate. In this work, we have evaluated the performance of two different polymer microfluidic chips for SAXS measurements.
|
|
| 17. |
- Fornell, Anna, et al.
(författare)
-
A Microfluidic Platform for Synchrotron X-ray Studies of Proteins
- 2021
-
Konferensbidrag (refereegranskat)abstract
- New tools are needed to allow for complex protein dynamics studies, especially to study proteins in their native states. In the AdaptoCell project a microfluidic platform for academic and industrial users at MAX IV Laboratory is being developed. MAX IV is a Swedish national laboratory providing brilliant synchrotron X-rays for research. Due to the high photon flux, sensitive samples such as proteins are prone to rapid radiation damage; thus, it is advantageous to have the liquid sample underflow to refresh the sample continuously. This, in combination with small volumes, makes microfluidics a highly suitable sample environment for protein studies at MAX IV. The AdaptoCell platform is being integrated at three beamlines:Balder (X-ray absorption/emission spectroscopy), CoSAXS (small angle x-ray scattering) and Micromax (serial synchrotron crystallography). Currently, the platform is fully available atBalder, under commissioning at CoSAXS and being developed for MicroMAX.
|
|
| 18. |
- Fornell, Anna, et al.
(författare)
-
AdaptoCell : Microfluidics at MAX IV Laboratory
- 2022
-
Ingår i: 25th Swedish Conference on Macromolecular Structure and Function.
-
Konferensbidrag (refereegranskat)abstract
- The AdaptoCell project at MAX IV has developed a microfluidic sample delivery platform for academic and industrial users to enable studies of protein samples in solution and in microcrystals underflow. The platform is compatible with various X-ray techniques and has so far been integrated onto two beamlines at MAX IV: the CoSAXS beamline for small angle X-ray scattering studies and the Balder beamline for X-ray absorption spectroscopy studies. Initial implementation of the platform for serial crystallography sample delivery is ongoing and will be integrated onto the BioMAX and MicroMAX beamlines once commissioned. With this platform, we aim to meet the demand from our user community for studying proteins at physiologically relevant temperatures and give the ability to follow dynamical processes in situ as well as decreasing sample volumes and radiation damage.To determine the optimized flow rates and components for mixing etc. using different microfluidic chips, a dedicated off(beam)line test station with a microscope has been established at the Biolab. The Biolab also provides a number of characterization techniques, such as Dynamic Light Scattering, UV-Vis spectrophotometry, for quality control of the samples; as well as an anaerobic chamber for preparation and characterization of metalloproteins. The microfluidic flows are controlled via syringe pumps or a pressure-driven system. Channel design varies, depending on the needs of the experiment, from straight channel, cross-junction to herringbone micromixers etc. On-chip mixing of buffers with different viscosity, pH, ion strength and protein concentrations has been demonstrated successful and will be presented.
|
|
| 19. |
- Fornell, Anna, et al.
(författare)
-
AdaptoCell – Microfluidic Platforms at MAX IV Laboratory
- 2021
-
Konferensbidrag (refereegranskat)abstract
- In the AdaptoCell project, we are developing microfluidic platforms for X-ray studies of liquid samples. Microfluidics is a suitable technology for samples that are prone to radiation damage, such as proteins. By having the sample underflow, the sample is continuously refreshed, and the risk of radiation damage is reduced. The technology is also suitable for investigating dynamic events such as in situ mixing. The microfluidic platforms are being integrated at three beamlines at MAX IV Laboratory: Balder (X-ray absorption/emission spectroscopy), CoSAXS (small angle x-ray scattering) and MicroMAX (serial synchrotron crystallography). Currently, the platforms are available for users at Balder and CoSAXS, which is under development at MicroMAX. In addition, we also provide a microfluidic offline test station where users can test their samples and optimise their devices before the beam time. The main components of the microfluidic setup are the pressure-driven flow controller and the microfluidic chip. We mainly use commercially available polymer microfluidic chips made of COC (cyclic olefin copolymer). COC is used as a chip material as it has high X-ray transmission and high resistance to radiation damage. There are several different chip designs available such as straight channel chips, droplet generator chips and mixing chips. We believe the AdaptoCell platforms will be useful and versatile sample environments for academic and industrial users at MAX IV Laboratory who want to perform experiments with liquid samples under flow.
|
|
| 20. |
|
|
| 21. |
- Ghai, Viney, 1989, et al.
(författare)
-
Achieving Long-Range Arbitrary Uniform Alignment of Nanostructures in Magnetic Fields
- 2024
-
Ingår i: Advanced Functional Materials. - 1616-3028 .- 1616-301X. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- For magnetic field orientation of nonstructures to become a viable method to create high performance multifunctional nanocomposites, it is of paramount importance to develop a method that is easy to implement and that can induce long-range uniform nanostructural alignment. To overcome this challenge, inspired by low field nuclear magnetic resonance (NMR) technology, a highly uniform, high field strength, and compact magnetic-field nanostructure orientation methodology is presented for polymeric nanocomposites using a Halbach array, for the first time. Potential new advances are showcased for applications of graphene polymer composites by considering their electro-thermal and antibacterial properties in highly oriented orthogonal morphologies. The high level of anisotropy induced in the graphene nanocomposites studied stands out through: 1) up to four decades higher electrical conductivities recorded in comparison to their randomly oriented counterparts, at concentrations where the latter show minimal improvements compared to the unfilled polymer; 2) over 1200% improvement in thermal conductivity, 3) antibacterial surfaces at field benchmark levels with lower filler content and with the added versatility of arbitrary orientation of the nanofillers. Overall, the new method and variations thereof can open up new horizons for tailoring nanostructure and performance for virtually all major nanocomposite applications based on graphene and other types of fillers.
|
|
| 22. |
- Ghanbari, Reza, 1984, et al.
(författare)
-
Painting Taylor vortices with cellulose nanocrystals: supercritical spectral dynamics
- 2023
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We study the flow stability and spatio-temporal spectral dynamics of cellulose nanocrystal (CNC) suspensions in a custom Taylor-Couette flow cell using the intrinsic shear induced birefringence and liquid crystalline properties of CNC suspensions for flow visualizations for the first time. The analysis is performed at constant ramped speed inputs of the independently rotating cylinders for several cases ranging from only inner or outer rotating cylinders to three counter-rotation cases. All CNC suspensions have measurable elastic and shear thinning, both increasing with CNC concentration. We show that the flow patterns recorded are essentially Newtonian-like, with non-Newtonian effects ranging from a decrease in wavenumbers to altering the critical parameters for the onset of instability modes. Outer cylinder rotation flow cases are stable for all concentrations whereas inner cylinder rotation flow cases transition to axisymmetric and azimuthally periodic secondary flows. However, unstable counter-rotation cases become unstable to asymmetric spiral modes. With increasing CNC concentration a counter-rotation case was found where azimuthally periodic wavy patterns transition to asymmetric spiral modes. In contrast to polymeric solutions of similar low to moderate elasticity and shear thinning, the shear-thinning region of CNC suspensions is expected to lead to the breakdown of the chiral nematic phase, whose elastic constants constitute the dominant structural elasticity mechanism. Thus, we interpret the Taylor-Couette stability of the CNC suspensions as dominated by their shear-thinning character due to the expected loss of elasticity in nonlinear flow conditions.
|
|
| 23. |
- Ghanbari, Reza, 1984, et al.
(författare)
-
Painting Taylor vortices with cellulose nanocrystals: Suspension flow supercritical spectral dynamics
- 2024
-
Ingår i: Physics of Fluids. - 1089-7666 .- 1070-6631. ; 36:4
-
Tidskriftsartikel (refereegranskat)abstract
- We study the flow stability and spatiotemporal spectral dynamics of cellulose nanocrystal (CNC) suspensions in a custom Taylor-Couette flow cell using the intrinsic shear induced birefringence and liquid crystalline properties of CNC suspensions for flow visualizations, for the first time. The analysis is performed at constant ramped speed inputs of the independently rotating cylinders for several cases ranging from only inner or outer rotating cylinders to three counter-rotation cases. All CNC suspensions have measurable elasticity and shear thinning, both increasing with CNC concentration. We show that the flow patterns recorded are essentially Newtonian-like, with non-Newtonian effects ranging from a decrease in wavenumbers to altering the critical parameters for the onset of instability modes. Outer cylinder rotation flow cases are stable for all concentrations whereas inner cylinder rotation flow cases transition to axisymmetric and azimuthally periodic secondary flows. However, counter-rotation cases become unstable to asymmetric spiral modes. With increasing CNC concentration, a counter-rotation case was found where azimuthally periodic wavy patterns transition to asymmetric spiral modes. Based on rheo-SAXS measurements, the shear-thinning region of CNC suspensions is expected to lead to the breakdown of the chiral nematic phase, whose elastic constants constitute the dominant structural elasticity mechanism. Thus, we interpret the Taylor-Couette stability of the CNC suspensions as dominated by their shear-thinning character due to the expected loss of elasticity in nonlinear flow conditions.
|
|
| 24. |
- Gilbert, Jennifer, et al.
(författare)
-
Evolution of the structure of lipid nanoparticles for nucleic acid delivery : From in situ studies of formulation to colloidal stability
- 2024
-
Ingår i: Journal of Colloid and Interface Science. - 0021-9797. ; 660, s. 66-76
-
Tidskriftsartikel (refereegranskat)abstract
- The development of lipid nanoparticle (LNP) based therapeutics for delivery of RNA has triggered the advance of new strategies for formulation, such as high throughput microfluidics for precise mixing of components into well-defined particles. In this study, we have characterised the structure of LNPs throughout the formulation process using in situ small angle x-ray scattering in the microfluidic chip, then by sampling in the subsequent dialysis process. The final formulation was investigated with small angle x-ray (SAXS) and neutron (SANS) scattering, dynamic light scattering (DLS) and cryo-TEM. The effect on structure was investigated for LNPs with a benchmark lipid composition and containing different cargos: calf thymus DNA (DNA) and two model mRNAs, polyadenylic acid (polyA) and polyuridylic acid (polyU). The LNP structure evolved during mixing in the microfluidic channel, however was only fully developed during the dialysis. The colloidal stability of the final formulation was affected by the type of incorporated nucleic acids (NAs) and decreased with the degree of base-pairing, as polyU induced extensive particle aggregation. The main NA LNP peak in the SAXS data for the final formulation were similar, with the repeat distance increasing from polyU
|
|
| 25. |
|
|
