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Zhao Y, Xie J. Numerical analysis of blood flow through stenosed microvessels using a multi-phase model. Heliyon 2024; 10:e29843. [PMID: 38694061 PMCID: PMC11058301 DOI: 10.1016/j.heliyon.2024.e29843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 04/15/2024] [Accepted: 04/16/2024] [Indexed: 05/03/2024] Open
Abstract
Blood flow in arterioles have attracted considerable research attention due to their clinical implications. However, the fluid structure interaction between red blood cells and plasma in the blood poses formidable difficulty to the computational efforts. In this contribution, we seek to represent the red blood cells in the blood as a continuous non-Newtonian phase and construct a multi-phase model for the blood flow in microvessels. The methods are presented and validated using a channel with sudden expansion. And the resulting blood flow inside a stenosed microvessel is investigated at different inlet velocity amplitudes and hematocrits. It is show that the increase of both inlet velocity amplitude and inlet hematocrit leads to longer and thicker cell-rich layer downstream the stenosis. Besides, it is found that the maximum values of wall shear stress scales up with inlet velocity amplitudes and hematocrits. These results show the validity of the proposed computational model and provide helpful insights into blood flow behaviors inside stenosed vessels.
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Affiliation(s)
- Yuhong Zhao
- Department of Blood Transfusion, The Frist Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310003, Zhejiang, China
| | - Jue Xie
- Department of Blood Transfusion, The Frist Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310003, Zhejiang, China
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2
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Andersson A, Linse S, Sparr E, Fornasier M, Jönsson P. The density of anionic lipids modulates the adsorption of α-Synuclein onto lipid membranes. Biophys Chem 2024; 305:107143. [PMID: 38100855 DOI: 10.1016/j.bpc.2023.107143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 11/20/2023] [Accepted: 11/28/2023] [Indexed: 12/17/2023]
Abstract
α-Synuclein is an intrinsically disordered presynaptic protein associated with Parkinson's disease. The physiological role of α-Synuclein is not fully understood, but the protein is known to interact with lipid membranes. We here study how membrane charge affects the adsorption of α-Synuclein to (i) supported lipid bilayers and (ii) small unilamellar vesicles with varying amounts of anionic lipids. The results showed that α-Synuclein adsorbs onto membranes containing ≥5% anionic phosphatidylserine (DOPS) lipids, but not to membranes containing ≤1% DOPS. The density of adsorbed α-Synuclein increased steadily with the DOPS content up to 20% DOPS, after which it leveled off. The vesicles were saturated with α-Synuclein at a 3-5 times higher protein density compared to the supported bilayers, which suggests that a more deformable membrane binds more α-Synuclein. Altogether, the results show that both membrane charge density and flexibility influence the association of α-Synuclein to lipid membranes.
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Affiliation(s)
| | - Sara Linse
- Department of Chemistry, Lund University, Lund, Sweden
| | - Emma Sparr
- Department of Chemistry, Lund University, Lund, Sweden
| | | | - Peter Jönsson
- Department of Chemistry, Lund University, Lund, Sweden.
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3
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Lehman SE, Benkstein KD, Cleveland TE, Anderson KW, Carrier MJ, Vreeland WN. Particle Metrology Approach to Understanding How Storage Conditions Affect Long-Term Liposome Stability. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:12313-12323. [PMID: 37603854 PMCID: PMC10484209 DOI: 10.1021/acs.langmuir.3c01270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 07/28/2023] [Indexed: 08/23/2023]
Abstract
Lipid nanoparticles are a generic type of nanomaterial with broad applicability in medicine as drug delivery vehicles. Liposomes are a subtype of lipid nanoparticles and, as a therapeutic platform, can be loaded with a genetic material or pharmaceutical agents for use as drug treatments. An open question for these types of lipid nanoparticles is what factor(s) affect the long-term stability of the particles. The stability of the particle is of great interest to understand and predict the effective shelf-life and storage requirements. In this report, we detail a one-year study of liposome stability as a function of lipid composition, buffer composition/pH, and storage temperature. This was done in aqueous solution without freezing. The effect of lipid composition is shown to be a critical factor when evaluating stability of the measured particle size and number concentration. Other factors (i.e., storage temperature and buffer pH/composition) were shown to be less critical but still have some effect. The stability of these particles informs formulation and optimal storage requirements and assists with future developmental planning of a NIST liposome-based reference material. This work also highlights the complex nature of long-term soft particle storage in biopharmaceutical applications.
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Affiliation(s)
- Sean E. Lehman
- Bioprocess
Measurements Group, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Kurt D. Benkstein
- Bioprocess
Measurements Group, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Thomas E. Cleveland
- Biomolecular
Structure and Function Group, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- Institute
for Bioscience and Biotechnology Research, Rockville, Maryland 20850, United States
| | - Kyle W. Anderson
- Bioprocess
Measurements Group, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- Institute
for Bioscience and Biotechnology Research, Rockville, Maryland 20850, United States
| | - Michael J. Carrier
- Bioprocess
Measurements Group, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Wyatt N. Vreeland
- Bioprocess
Measurements Group, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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Fitzgerald JE, Venable RM, Pastor RW, Lyman ER. Surface viscosities of lipid bilayers determined from equilibrium molecular dynamics simulations. Biophys J 2023; 122:1094-1104. [PMID: 36739477 PMCID: PMC10111272 DOI: 10.1016/j.bpj.2023.01.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 01/20/2023] [Accepted: 01/27/2023] [Indexed: 02/05/2023] Open
Abstract
Lipid membrane viscosity is critical to biological function. Bacterial cells grown in different environments alter their lipid composition in order to maintain a specific viscosity, and membrane viscosity has been linked to the rate of cellular respiration. To understand the factors that determine the viscosity of a membrane, we ran equilibrium all-atom simulations of single component lipid bilayers and calculated their viscosities. The viscosity was calculated via a Green-Kubo relation, with the stress-tensor autocorrelation function modeled by a stretched exponential function. By simulating a series of lipids at different temperatures, we establish the dependence of viscosity on several aspects of lipid chemistry, including hydrocarbon chain length, unsaturation, and backbone structure. Sphingomyelin is found to have a remarkably high viscosity, roughly 20 times that of DPPC. Furthermore, we find that inclusion of the entire range of the dispersion interaction increases viscosity by up to 140%. The simulated viscosities are similar to experimental values obtained from the rotational dynamics of small chromophores and from the diffusion of integral membrane proteins but significantly lower than recent measurements based on the deformation of giant vesicles.
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Affiliation(s)
- James E Fitzgerald
- Department of Physics & Astronomy, University of Delaware, Newark, Delaware
| | - Richard M Venable
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Edward R Lyman
- Department of Physics & Astronomy, University of Delaware, Newark, Delaware; Department of Chemistry & Biochemistry, University of Delaware, Newark, Delaware.
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5
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Schoch RL, Haran G, Brown FLH. Dynamic correlations in lipid bilayer membranes over finite time intervals. J Chem Phys 2023; 158:044112. [PMID: 36725516 DOI: 10.1063/5.0129130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Recent single-molecule measurements [Schoch et al., Proc. Natl. Acad. Sci. U. S. A. 118, e2113202118 (2021)] have observed dynamic lipid-lipid correlations in membranes with submicrometer spatial resolution and submillisecond temporal resolution. While short from an instrumentation standpoint, these length and time scales remain long compared to microscopic molecular motions. Theoretical expressions are derived to infer experimentally measurable correlations from the two-body diffusion matrix appropriate for membrane-bound bodies coupled by hydrodynamic interactions. The temporal (and associated spatial) averaging resulting from finite acquisition times has the effect of washing out correlations as compared to naive predictions (i.e., the bare elements of the diffusion matrix), which would be expected to hold for instantaneous measurements. The theoretical predictions are shown to be in excellent agreement with Brownian dynamics simulations of experimental measurements. Numerical results suggest that the experimental measurement of membrane protein diffusion, in complement to lipid diffusion measurements, might help to resolve the experimental ambiguities encountered for certain black lipid membranes.
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Affiliation(s)
- Rafael L Schoch
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Gilad Haran
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Frank L H Brown
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA
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Structural Analyses of the Glycolipids in Lipid Rafts. Methods Mol Biol 2023; 2613:145-152. [PMID: 36587077 DOI: 10.1007/978-1-0716-2910-9_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Lipid rafts are usually isolated from cells or tissues using sucrose gradient ultracentrifugation in the presence of detergents such as Triton X-100 at 4 °C. Although detergents should be removed for further structural characterization following fractionation, these compounds are often difficult to completely remove, especially from the glycolipids. In this chapter, we describe a novel method for the fast and convenient removal of detergents from lipid raft glycolipids following fraction and describe the application of this method.
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