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Abstract
AbstractThe dynamics of proteins in solution includes a variety of processes, such as backbone and side-chain fluctuations, interdomain motions, as well as global rotational and translational (i.e. center of mass) diffusion. Since protein dynamics is related to protein function and essential transport processes, a detailed mechanistic understanding and monitoring of protein dynamics in solution is highly desirable. The hierarchical character of protein dynamics requires experimental tools addressing a broad range of time- and length scales. We discuss how different techniques contribute to a comprehensive picture of protein dynamics, and focus in particular on results from neutron spectroscopy. We outline the underlying principles and review available instrumentation as well as related analysis frameworks.
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2
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Membrane Flow Drives an Adhesion-Independent Amoeboid Cell Migration Mode. Dev Cell 2018; 46:9-22.e4. [PMID: 29937389 DOI: 10.1016/j.devcel.2018.05.029] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 03/28/2018] [Accepted: 05/23/2018] [Indexed: 12/30/2022]
Abstract
Cells migrate by applying rearward forces against extracellular media. It is unclear how this is achieved in amoeboid migration, which lacks adhesions typical of lamellipodia-driven mesenchymal migration. To address this question, we developed optogenetically controlled models of lamellipodia-driven and amoeboid migration. On a two-dimensional surface, migration speeds in both modes were similar. However, when suspended in liquid, only amoeboid cells exhibited rapid migration accompanied by rearward membrane flow. These cells exhibited increased endocytosis at the back and membrane trafficking from back to front. Genetic or pharmacological perturbation of this polarized trafficking inhibited migration. The ratio of cell migration and membrane flow speeds matched the predicted value from a model where viscous forces tangential to the cell-liquid interface propel the cell forward. Since this mechanism does not require specific molecular interactions with the surrounding medium, it can facilitate amoeboid migration observed in diverse microenvironments during immune function and cancer metastasis.
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3
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Gura Sadovsky R, Brielle S, Kaganovich D, England JL. Measurement of Rapid Protein Diffusion in the Cytoplasm by Photo-Converted Intensity Profile Expansion. Cell Rep 2017; 18:2795-2806. [PMID: 28297680 PMCID: PMC5368347 DOI: 10.1016/j.celrep.2017.02.063] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 12/05/2016] [Accepted: 02/17/2017] [Indexed: 11/27/2022] Open
Abstract
The fluorescence microscopy methods presently used to characterize protein motion in cells infer protein motion from indirect observables, rather than measuring protein motion directly. Operationalizing these methods requires expertise that can constitute a barrier to their broad utilization. Here, we have developed PIPE (photo-converted intensity profile expansion) to directly measure the motion of tagged proteins and quantify it using an effective diffusion coefficient. PIPE works by pulsing photo-convertible fluorescent proteins, generating a peaked fluorescence signal at the pulsed region, and analyzing the spatial expansion of the signal. We demonstrate PIPE's success in measuring accurate diffusion coefficients in silico and in vitro and compare effective diffusion coefficients of native cellular proteins and free fluorophores in vivo. We apply PIPE to measure diffusion anomality in the cell and use it to distinguish free fluorophores from native cellular proteins. PIPE's direct measurement and ease of use make it appealing for cell biologists.
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Affiliation(s)
- Rotem Gura Sadovsky
- Physics of Living Systems Group, Massachusetts Institute of Technology, Cambridge, MA 02138, USA; Computational and Systems Biology Graduate Program, Massachusetts Institute of Technology, Cambridge, MA 02138, USA
| | - Shlomi Brielle
- Department of Cell and Developmental Biology, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel; Alexander Grass Center for Bioengineering, Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Daniel Kaganovich
- Department of Cell and Developmental Biology, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | - Jeremy L England
- Physics of Living Systems Group, Massachusetts Institute of Technology, Cambridge, MA 02138, USA.
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4
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Khandai S, Jena SS. Transition from double to single diffusive behavior with increase in polymer concentration for oppositely charged guest - host systems of green fluorescent protein diffusing inside poly-l-lysine solutions. J Colloid Interface Sci 2017; 505:196-205. [PMID: 28578282 DOI: 10.1016/j.jcis.2017.05.085] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/21/2017] [Accepted: 05/24/2017] [Indexed: 11/19/2022]
Abstract
The effect of crowding, background and probe charges and chain flexibility on probe dynamics of Green Fluorescent Protein in polyelectrolyte solutions of poly-l-lysine was investigated using Fluorescence Recovery After Photobleaching (FRAP). An interesting double diffusive behavior in FRAP recovery curve was observed at low polymer concentration resulting in two relaxation modes, which disappears with rise in polymer concentration. The fast relaxation mode attributes to diffusion of free protein molecules alone, where as slow mode is credited to polymer adsorbed protein molecules. Absence of double diffusive behavior at higher polymer concentration is argued in terms of varying host chain conformation and the only relaxation mode present is due to movement of free probes alone rather than that of adsorbed proteins. We noticed only a marginal decrease in diffusion coefficient with rise in salt concentration and the trend is reversed when variation in sample viscosity with salt is taken into account. In addition a small but systematic decrease in diffusion coefficient is seen with increase in magnitude of probe charge. Comparison of results with ideal Stoke - Einstein relation brings out the importance of polyelectrolyte effect and indicates ∼200 - fold positive deviations from predicted value for both variation in ionic strength and solution pH.
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Affiliation(s)
- Santripti Khandai
- Department of Physics and Astronomy, National Institute of Technology Rourkela, Rourkela 769008, Odisha, India
| | - Sidhartha S Jena
- Department of Physics and Astronomy, National Institute of Technology Rourkela, Rourkela 769008, Odisha, India.
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5
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Palit S, He L, Hamilton WA, Yethiraj A, Yethiraj A. The effect of crowder charge in a model polymer–colloid system for macromolecular crowding: Polymer structure and dynamics. J Chem Phys 2017; 147:114902. [DOI: 10.1063/1.4986353] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Swomitra Palit
- Department of Physics and Physical Oceanography, Memorial University, St. John’s, Newfoundland and Labrador A1B3X7, Canada
| | - Lilin He
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - William A. Hamilton
- Instrument and Source Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Arun Yethiraj
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Anand Yethiraj
- Department of Physics and Physical Oceanography, Memorial University, St. John’s, Newfoundland and Labrador A1B3X7, Canada
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6
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Feng X, Chen A, Wang J, Zhao N, Hou Z. Understanding Protein Diffusion in Polymer Solutions: A Hydration with Depletion Model. J Phys Chem B 2016; 120:10114-10123. [DOI: 10.1021/acs.jpcb.6b06248] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Xiaoqing Feng
- College
of Chemistry, Sichuan University, Chengdu 610064, China
| | - Anpu Chen
- College
of Chemistry, Sichuan University, Chengdu 610064, China
| | - Juan Wang
- College
of Chemistry, Sichuan University, Chengdu 610064, China
| | - Nanrong Zhao
- College
of Chemistry, Sichuan University, Chengdu 610064, China
| | - Zhonghuai Hou
- Hefei National Laboratory for Physical Sciences at the Microscale & Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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7
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Rothe M, Gruber T, Gröger S, Balbach J, Saalwächter K, Roos M. Transient binding accounts for apparent violation of the generalized Stokes-Einstein relation in crowded protein solutions. Phys Chem Chem Phys 2016; 18:18006-14. [PMID: 27326536 DOI: 10.1039/c6cp01056c] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The effect of high concentration, also referred to as crowding conditions, on Brownian motion is of central relevance for the understanding of the physical, chemical and biological properties of proteins in their native environment. Specifically, the simple inverse relationship between the translational diffusion coefficient and the macroscopic solution viscosity as predicted by the generalized Stokes-Einstein (GSE) relation has been the subject of many studies, yet a consensus on its applicability has not been reached. Here, we use isotope-filtered pulsed-field gradient NMR to separately assess the μm-scale diffusivity of two proteins, BSA and an SH3 domain, in mixtures as well as single-protein solutions, and demonstrate that transient binding can account for an apparent violation of the GSE relation. Whereas GSE behavior applies for the single-protein solutions, it does not hold for the protein mixtures. Transient binding behavior in the concentrated mixtures is evidenced by calorimetric experiments and by a significantly increased apparent activation energy of diffusion. In contrast, the temperature dependence of the viscosity, as well as of the diffusivity in single-component solutions, is always dominated by the flow activation energy of pure water. As a practically relevant second result, we further show that, for high protein concentrations, the diffusion of small molecules such as dioxane or water is not generally a suitable probe for the viscosity experienced by the diffusing proteins.
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Affiliation(s)
- M Rothe
- Martin-Luther-Universität Halle-Wittenberg, Institut für Physik, 06120 Halle (Saale), Germany.
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8
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Banks DS, Tressler C, Peters RD, Höfling F, Fradin C. Characterizing anomalous diffusion in crowded polymer solutions and gels over five decades in time with variable-lengthscale fluorescence correlation spectroscopy. SOFT MATTER 2016; 12:4190-4203. [PMID: 27050290 DOI: 10.1039/c5sm01213a] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The diffusion of macromolecules in cells and in complex fluids is often found to deviate from simple Fickian diffusion. One explanation offered for this behavior is that molecular crowding renders diffusion anomalous, where the mean-squared displacement of the particles scales as 〈r(2)〉∝t(α) with α < 1. Unfortunately, methods such as fluorescence correlation spectroscopy (FCS) or fluorescence recovery after photobleaching (FRAP) probe diffusion only over a narrow range of lengthscales and cannot directly test the dependence of the mean-squared displacement (MSD) on time. Here we show that variable-lengthscale FCS (VLS-FCS), where the volume of observation is varied over several orders of magnitude, combined with a numerical inversion procedure of the correlation data, allows retrieving the MSD for up to five decades in time, bridging the gap between diffusion experiments performed at different lengthscales. In addition, we show that VLS-FCS provides a way to assess whether the propagator associated with the diffusion is Gaussian or non-Gaussian. We used VLS-FCS to investigate two systems where anomalous diffusion had been previously reported. In the case of dense cross-linked agarose gels, the measured MSD confirmed that the diffusion of small beads was anomalous at short lengthscales, with a cross-over to simple diffusion around ≈1 μm, consistent with a caged diffusion process. On the other hand, for solutions crowded with marginally entangled dextran molecules, we uncovered an apparent discrepancy between the MSD, found to be linear, and the propagators at short lengthscales, found to be non-Gaussian. These contradicting features call to mind the "anomalous, yet Brownian" diffusion observed in several biological systems, and the recently proposed "diffusing diffusivity" model.
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Affiliation(s)
- Daniel S Banks
- Department of Physics and Astronomy, McMaster University, 1280 Main St. W, Hamilton, ON L8S 4M1, Canada.
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9
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Rashid R, Chee SML, Raghunath M, Wohland T. Macromolecular crowding gives rise to microviscosity, anomalous diffusion and accelerated actin polymerization. Phys Biol 2015; 12:034001. [DOI: 10.1088/1478-3975/12/3/034001] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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10
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Parry BR, Surovtsev IV, Cabeen MT, O'Hern CS, Dufresne ER, Jacobs-Wagner C. The bacterial cytoplasm has glass-like properties and is fluidized by metabolic activity. Cell 2013; 156:183-94. [PMID: 24361104 DOI: 10.1016/j.cell.2013.11.028] [Citation(s) in RCA: 478] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 07/31/2013] [Accepted: 11/05/2013] [Indexed: 11/17/2022]
Abstract
The physical nature of the bacterial cytoplasm is poorly understood even though it determines cytoplasmic dynamics and hence cellular physiology and behavior. Through single-particle tracking of protein filaments, plasmids, storage granules, and foreign particles of different sizes, we find that the bacterial cytoplasm displays properties that are characteristic of glass-forming liquids and changes from liquid-like to solid-like in a component size-dependent fashion. As a result, the motion of cytoplasmic components becomes disproportionally constrained with increasing size. Remarkably, cellular metabolism fluidizes the cytoplasm, allowing larger components to escape their local environment and explore larger regions of the cytoplasm. Consequently, cytoplasmic fluidity and dynamics dramatically change as cells shift between metabolically active and dormant states in response to fluctuating environments. Our findings provide insight into bacterial dormancy and have broad implications to our understanding of bacterial physiology, as the glassy behavior of the cytoplasm impacts all intracellular processes involving large components.
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Affiliation(s)
- Bradley R Parry
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Ivan V Surovtsev
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA; Howard Hughes Medical Institute, Yale University, New Haven, CT 06520, USA
| | - Matthew T Cabeen
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Corey S O'Hern
- Department of Applied Physics, Yale University, New Haven, CT 06520, USA; Department of Physics, Yale University, New Haven, CT 06520, USA; Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520, USA
| | - Eric R Dufresne
- Department of Physics, Yale University, New Haven, CT 06520, USA; Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520, USA; Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06520, USA; Department of Cell Biology, Yale University, New Haven, CT 06520, USA
| | - Christine Jacobs-Wagner
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA; Howard Hughes Medical Institute, Yale University, New Haven, CT 06520, USA; Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06510, USA.
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11
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Salamon K, Aumiler D, Pabst G, Vuletić T. Probing the Mesh Formed by the Semirigid Polyelectrolytes. Macromolecules 2013. [DOI: 10.1021/ma3021486] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- K. Salamon
- Institut za fiziku, Bijenička 46, 10000 Zagreb, Croatia
| | - D. Aumiler
- Institut za fiziku, Bijenička 46, 10000 Zagreb, Croatia
| | - G. Pabst
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, Schmiedlstr. 6, 8042 Graz, Austria
| | - T. Vuletić
- Institut za fiziku, Bijenička 46, 10000 Zagreb, Croatia
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12
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Keum JW, Bermudez H. DNA-based delivery vehicles: pH-controlled disassembly and cargo release. Chem Commun (Camb) 2012; 48:12118-20. [PMID: 23143043 DOI: 10.1039/c2cc37471d] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Non-Watson-Crick base pairing provides an in situ approach for actuation of DNA nanostructures through responses to solution conditions. Here we demonstrate this concept by using physiologically-relevant changes in pH to regulate DNA pyramid assembly/disassembly and to control the release of protein cargo.
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Affiliation(s)
- Jung-Won Keum
- Department of Chemical Engineering, University of Massachusetts, Amherst, MA, USA
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13
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Song B, Song J, Zhang S, Anderson MA, Ao Y, Yang CY, Deming TJ, Sofroniew MV. Sustained local delivery of bioactive nerve growth factor in the central nervous system via tunable diblock copolypeptide hydrogel depots. Biomaterials 2012; 33:9105-16. [PMID: 22985994 DOI: 10.1016/j.biomaterials.2012.08.060] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 08/24/2012] [Indexed: 11/17/2022]
Abstract
Biomaterial vehicles that can provide sustained, site-specific molecular delivery in the central nervous system (CNS) have potential for therapeutic and investigative applications. Here, we present in vitro and in vivo proof of principle tests of diblock copolypeptide hydrogels (DCH) to serve as depots for sustained local release of protein effector molecules. We tested two DCH, K(180)L(20) and E(180)L(20), previously shown to self-assemble into biocompatible, biodegradable deposits that persist four to eight weeks after injection into mouse forebrain. In vitro tests demonstrated sustained release from dialysis cassettes of the representative protein, lysozyme, dissolved in K(180)L(20) or E(180)L(20) hydrogels. Release time in vitro varied in relation to DCH charge and mechanical properties, and ionic strength of the media. To evaluate bioactive protein delivery in vivo, we used nerve growth factor (NGF) and measured the size of mouse forebrain cholinergic neurons, which respond to NGF with cellular hypertrophy. For in vivo tests, the storage modulus of DCH depots was tuned to just below that of CNS tissue. In comparison with NGF injected in buffer, depots of NGF dissolved in either K(180)L(20) or E(180)L(20) provided significantly longer delivery of NGF bioactivity, maintaining hypertrophy of local forebrain cholinergic neurons for at least 4 weeks and inducing hypertrophy a further distance away (up to 5 mm) from injection sites. These findings show that depots of DCH injected into CNS can provide sustained delivery within the blood-brain barrier of a bioactive protein growth factor that exerts a predicted, quantifiable effect on local cells over a prolonged subacute time.
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Affiliation(s)
- Bingbing Song
- Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1763, USA
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14
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Donner JS, Thompson SA, Kreuzer MP, Baffou G, Quidant R. Mapping intracellular temperature using green fluorescent protein. NANO LETTERS 2012; 12:2107-11. [PMID: 22394124 DOI: 10.1021/nl300389y] [Citation(s) in RCA: 220] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Heat is of fundamental importance in many cellular processes such as cell metabolism, cell division and gene expression. (1-3) Accurate and noninvasive monitoring of temperature changes in individual cells could thus help clarify intricate cellular processes and develop new applications in biology and medicine. Here we report the use of green fluorescent proteins (GFP) as thermal nanoprobes suited for intracellular temperature mapping. Temperature probing is achieved by monitoring the fluorescence polarization anisotropy of GFP. The method is tested on GFP-transfected HeLa and U-87 MG cancer cell lines where we monitored the heat delivery by photothermal heating of gold nanorods surrounding the cells. A spatial resolution of 300 nm and a temperature accuracy of about 0.4 °C are achieved. Benefiting from its full compatibility with widely used GFP-transfected cells, this approach provides a noninvasive tool for fundamental and applied research in areas ranging from molecular biology to therapeutic and diagnostic studies.
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Affiliation(s)
- Jon S Donner
- ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain
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15
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Abstract
Animal cells migrating over a substratum crawl in amoeboid fashion; how the force against the substratum is achieved remains uncertain. We find that amoebae and neutrophils, cells traditionally used to study cell migration on a solid surface, move toward a chemotactic source while suspended in solution. They can swim and do so with speeds similar to those on a solid substrate. Based on the surprisingly rapidly changing shape of amoebae as they swim and earlier theoretical schemes for how suspended microorganisms can migrate (Purcell EM (1977) Life at low Reynolds number. Am J Phys 45:3-11), we suggest the general features these cells use to gain traction with the medium. This motion requires either the movement of the cell's surface from the cell's front toward its rear or protrusions that move down the length of the elongated cell. Our results indicate that a solid substratum is not a prerequisite for these cells to produce a forward thrust during movement and suggest that crawling and swimming are similar processes, a comparison we think is helpful in understanding how cells migrate.
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Vermonden T, Jena SS, Barriet D, Censi R, van der Gucht J, Hennink WE, Siegel RA. Macromolecular Diffusion in Self-Assembling Biodegradable Thermosensitive Hydrogels. Macromolecules 2010; 43:782-789. [PMID: 20885989 PMCID: PMC2946210 DOI: 10.1021/ma902186e] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hydrogel formation triggered by a change in temperature is an attractive mechanism for in situ gelling biomaterials for pharmaceutical applications such as the delivery of therapeutic proteins. In this study, hydrogels were prepared from ABA triblock polymers having thermosensitive poly(N-(2-hydroxypropyl) methacrylamide lactate) flanking A-blocks and hydrophilic poly(ethylene glycol) B-blocks. Polymers with fixed length A blocks (~22 kDA) but differing PEG-midblock lengths (2, 4 and 10 kDa) were synthesized and dissolved in water with dilute fluorescein isothiocyanate (FITC)-labeled dextrans (70 and 500 kDA). Hydrogels encapsulating the dextrans were formed by raising the temperature. Fluorescence recovery after photobleaching (FRAP) studies showed that diffusion coefficients and mobile fractions of the dextran dyes decreased upon elevating temperatures above 25 °C. Confocal laser scanning microscopy and cryo-SEM demonstrated that hydrogel structure depended on PEG block length. Phase separation into polymer-rich and water-rich domains occurred to a larger extent for polymers with small PEG blocks compared to polymers with a larger PEG block. By changing the PEG block length and thereby the hydrogel structure, mobility of FITC-dextran could be tailored. At physiological pH the hydrogels degraded over time by ester hydrolysis, resulting in increased mobility of the encapsulated dye. Since diffusion can be controlled according to polymer design and concentration, plus temperature, these biocompatible hydrogels are attractive as potential in situ gelling biodegradable materials for macromolecular drug delivery.
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Affiliation(s)
- Tina Vermonden
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, P.O. Box 80082, 3508 TB, Utrecht, The Netherlands
- Department of Pharmaceutics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Sidhartha S. Jena
- Department of Pharmaceutics, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Physics, National Institute of Technology, Rourkela, Rourkela 769008, Orissa, India
| | - David Barriet
- Department of Pharmaceutics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Roberta Censi
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, P.O. Box 80082, 3508 TB, Utrecht, The Netherlands
| | - Jasper van der Gucht
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands
| | - Wim E. Hennink
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, P.O. Box 80082, 3508 TB, Utrecht, The Netherlands
| | - Ronald A. Siegel
- Department of Pharmaceutics, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
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17
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Lorén N, Nydén M, Hermansson AM. Determination of local diffusion properties in heterogeneous biomaterials. Adv Colloid Interface Sci 2009; 150:5-15. [PMID: 19481193 DOI: 10.1016/j.cis.2009.05.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2009] [Revised: 05/11/2009] [Accepted: 05/12/2009] [Indexed: 11/25/2022]
Abstract
The coupling between structure and diffusion properties is essential for the functionality of heterogeneous biomaterials. Structural heterogeneity is defined and its implications for time-dependent diffusion are discussed in detail. The effect of structural heterogeneity in biomaterials on diffusion and the relevance of length scales are exemplified with regard to different biomaterials such as gels, emulsions, phase separated biopolymer mixtures and chocolate. Different diffusion measurement techniques for determination of diffusion properties at different length and time scales are presented. The interplay between local and global diffusion is discussed. New measurement techniques have emerged that enable simultaneous determination of both structure and local diffusion properties. Special emphasis is given to fluorescence recovery after photobleaching (FRAP). The possibilities of FRAP at a conceptual level is presented. The method of FRAP is briefly reviewed and its use in heterogeneous biomaterials, at barriers and during dynamic changes of the structure is discussed.
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18
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Jablonski AE, Humphries WH, Payne CK. Pyrenebutyrate-mediated delivery of quantum dots across the plasma membrane of living cells. J Phys Chem B 2009; 113:405-8. [PMID: 19099434 DOI: 10.1021/jp809956w] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Quantum dots have been delivered directly across the plasma membrane to the cytosol of living cells using a combination of a cationic peptide, polyarginine, and a hydrophobic counterion, pyrenebutyrate. Quantum dot delivery did not disrupt the plasma membrane and bypassed the barrier of endocytic vesicles. Cellular uptake was independent of temperature but highly dependent on the surface charge of the quantum dot and the membrane potential of the cell, suggesting a direct translocation across the membrane. This method of delivery can find immediate application for quantum dots and may be broadly applicable to other nanoparticles.
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Affiliation(s)
- Amy E Jablonski
- School of Chemistry and Biochemistry and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332, USA
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19
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Krasnenko V, Tkaczyk AH, Tkaczyk ER, Mauring K. Physicochemical properties of blue fluorescent protein determined via molecular dynamics simulation. Biopolymers 2008; 89:1136-43. [DOI: 10.1002/bip.21065] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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20
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DeRouchey J, Schmidt C, Walker GF, Koch C, Plank C, Wagner E, Rädler JO. Monomolecular Assembly of siRNA and Poly(ethylene glycol)−Peptide Copolymers. Biomacromolecules 2008; 9:724-32. [DOI: 10.1021/bm7011482] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jason DeRouchey
- Department of Physics, Department of Chemistry and Pharmacy, and Center for NanoScience, Ludwig-Maximilians-Universität, 80539 Munich, Germany, Institute of Experimental Oncology, Technische Universität, 81675 Munich, Germany, and National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20692
| | - Claudia Schmidt
- Department of Physics, Department of Chemistry and Pharmacy, and Center for NanoScience, Ludwig-Maximilians-Universität, 80539 Munich, Germany, Institute of Experimental Oncology, Technische Universität, 81675 Munich, Germany, and National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20692
| | - Greg F. Walker
- Department of Physics, Department of Chemistry and Pharmacy, and Center for NanoScience, Ludwig-Maximilians-Universität, 80539 Munich, Germany, Institute of Experimental Oncology, Technische Universität, 81675 Munich, Germany, and National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20692
| | - Christian Koch
- Department of Physics, Department of Chemistry and Pharmacy, and Center for NanoScience, Ludwig-Maximilians-Universität, 80539 Munich, Germany, Institute of Experimental Oncology, Technische Universität, 81675 Munich, Germany, and National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20692
| | - Christian Plank
- Department of Physics, Department of Chemistry and Pharmacy, and Center for NanoScience, Ludwig-Maximilians-Universität, 80539 Munich, Germany, Institute of Experimental Oncology, Technische Universität, 81675 Munich, Germany, and National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20692
| | - Ernst Wagner
- Department of Physics, Department of Chemistry and Pharmacy, and Center for NanoScience, Ludwig-Maximilians-Universität, 80539 Munich, Germany, Institute of Experimental Oncology, Technische Universität, 81675 Munich, Germany, and National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20692
| | - Joachim O. Rädler
- Department of Physics, Department of Chemistry and Pharmacy, and Center for NanoScience, Ludwig-Maximilians-Universität, 80539 Munich, Germany, Institute of Experimental Oncology, Technische Universität, 81675 Munich, Germany, and National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20692
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21
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Kayitmazer AB, Bohidar HB, Mattison KW, Bose A, Sarkar J, Hashidzume A, Russo PS, Jaeger W, Dubin PL. Mesophase separation and probe dynamics in protein-polyelectrolyte coacervates. SOFT MATTER 2007; 3:1064-1076. [PMID: 32900056 DOI: 10.1039/b701334e] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Protein-polyelectrolyte coacervates are self-assembling macroscopically monophasic biomacromolecular fluids whose unique properties arise from transient heterogeneities. The structures of coacervates formed at different conditions of pH and ionic strength from poly(dimethyldiallylammonium chloride) and bovine serum albumin (BSA), were probed using fluorescence recovery after photobleaching. Measurements of self-diffusion in coacervates were carried out using fluorescein-tagged BSA, and similarly tagged Ficoll, a non-interacting branched polysaccharide with the same size as BSA. The results are best explained by temporal and spatial heterogeneities, also inferred from static light scattering and cryo-TEM, which indicate heterogeneous scattering centers of several hundred nm. Taken together with previous dynamic light scattering and rheology studies, the results are consistent with the presence of extensive dilute domains in which are embedded partially interconnected 50-700 nm dense domains. At short length scales, protein mobility is unobstructed by these clusters. At intermediate length scales, proteins are slowed down due to tortuosity effects within the blind alleys of the dense domains, and to adsorption at dense/dilute domain interfaces. Finally, at long length scales, obstructed diffusion is alleviated by the break-up of dense domains. These findings are discussed in terms of previously suggested models for protein-polyelectrolyte coacervates. Possible explanations for the origin of mesophase separation are offered.
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Affiliation(s)
- A Basak Kayitmazer
- Department of Chemistry, University of Massachusetts Amherst, 710 N. Pleasant St. LGRT 701 Amherst, MA 01003, USA.
| | | | - Kevin W Mattison
- Department of Chemistry, Indiana University-Purdue University, Indianapolis, IN, USA
| | - Arijit Bose
- Department of Chemical Engineering, University of Rhode Island, Kingston, RI, USA
| | - Jayashri Sarkar
- Department of Chemical Engineering, University of Rhode Island, Kingston, RI, USA
| | | | - Paul S Russo
- Department of Chemistry, Louisiana State University, USA
| | - Werner Jaeger
- Fraunhofer Institute of Applied Polymer Research, Germany
| | - Paul L Dubin
- Department of Chemistry, University of Massachusetts Amherst, 710 N. Pleasant St. LGRT 701 Amherst, MA 01003, USA.
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22
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Michelman-Ribeiro A, Horkay F, Nossal R, Boukari H. Probe Diffusion in Aqueous Poly(vinyl alcohol) Solutions Studied by Fluorescence Correlation Spectroscopy. Biomacromolecules 2007; 8:1595-600. [PMID: 17441767 DOI: 10.1021/bm061195r] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report fluorescence correlation spectroscopy measurements of the translational diffusion coefficient of various probe particles in dilute and semidilute aqueous poly(vinyl alcohol) solutions. The range of sizes of the particles (fluorescent molecules, proteins, and polymers) was chosen to explore various length scales of the polymer solutions as defined by the polymer-polymer correlation length. For particles larger than the correlation length, we find that the diffusion coefficient, D, decreases exponentially with the polymer concentration. This can be explained by an exponential increase in the solution viscosity, consistent with the Stokes-Einstein equation. For probes on the order of the correlation length, the decrease of the diffusion coefficient cannot be accounted for by the Stokes-Einstein equation, but can be fit by a stretched exponential, D approximately exp(-alphacn), where we find n = 0.73-0.84 and alpha is related to the probe size. These results are in accord with a diffusion model of Langevin and Rondelez (Polymer 1978, 19, 1875), where these values of n indicate a good solvent quality.
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Affiliation(s)
- Ariel Michelman-Ribeiro
- Laboratory of Integrative and Medical Biophysics, National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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23
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Mac Gabhann F, Demetriades AM, Deering T, Packer JD, Shah SM, Duh E, Campochiaro PA, Popel AS. Protein transport to choroid and retina following periocular injection: theoretical and experimental study. Ann Biomed Eng 2007; 35:615-30. [PMID: 17277991 DOI: 10.1007/s10439-006-9238-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Accepted: 11/16/2006] [Indexed: 11/30/2022]
Abstract
Ocular neovascularization is a major cause of blindness in several diseases including age-related macular degeneration (choroidal neovascularization) and diabetic retinopathy (retinal neovascularization). Antiangiogenic agents with clinically significant effects exist, but a key question remains: how to effectively deliver drugs to the site of neovascularization. Periocular delivery of drugs or proteins is less invasive and safer than intravitreous delivery, but little is known regarding how and to what extent agents access intraocular tissues after periocular injection. We present a computational model of drug or protein transport into the eye following periocular injection to quantify movement of macromolecules across the sclera of the mouse eye. We apply this model to the movement of green fluorescent protein (GFP) across the mouse eye and fit the results of in vivo experiments to find transport parameters. Using these parameters, the model gives the profile of interstitial GFP concentration across the sclera, choroid and retina. We compare this to predictions of transport following intravitreous injections. We then scale up the model to estimate the transport of GFP into the human choroid and retina; the thicker sclera decreases transscleral delivery. This is the first model of ocular drug delivery to explicitly account for transport properties of each eye layer.
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Affiliation(s)
- Feilim Mac Gabhann
- Department of Biomedical Engineering, The Wilmer Eye Institute, Johns Hopkins University School of Medicine, 720 Rutland Ave, #613 Traylor, Baltimore, MD 21205, USA.
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24
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Du F, Zhou Z, Mo ZY, Shi JZ, Chen J, Liang Y. Mixed Macromolecular Crowding Accelerates the Refolding of Rabbit Muscle Creatine Kinase: Implications for Protein Folding in Physiological Environments. J Mol Biol 2006; 364:469-82. [PMID: 17027032 DOI: 10.1016/j.jmb.2006.09.018] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 08/28/2006] [Accepted: 09/03/2006] [Indexed: 11/21/2022]
Abstract
The effects of four single macromolecular crowding agents, Ficoll 70, dextran 70, polyethylene glycol (PEG) 2000, and calf thymus DNA (CT DNA), and three mixed crowding agents containing both CT DNA and polysaccharide (or PEG 2000) on the refolding of guanidine hydrochloride-denatured rabbit muscle creatine kinase (MM-CK) have been examined by activity assay. When the total concentration of the mixed crowding agent is 100 g/l, in which the weight ratio of CT DNA to Ficoll 70 is 1:9, the refolding yield of MM-CK after refolding for 3 h under these conditions increases 23% compared with that in the presence of 10 g/l CT DNA, 18% compared with 100 g/l Ficoll 70, and 19% compared with that in the absence of crowding agents. A remarkable increase in the refolding yield of MM-CK by a mixed crowding agent containing CT DNA and dextran 70 (or PEG 2000) is also observed. Further folding kinetics analyses show that these three mixed crowding agents remarkably accelerate the refolding of MM-CK, compared with single crowding agents. Aggregation of MM-CK in the presence of any of the three mixed crowding agents is less serious than that in the presence of a single crowding agent at the same concentration but more serious than that in the absence of crowding agents. Both the refolding yield and the refolding rate of MM-CK in mixtures of these agents are increased relative to the individual agents by themselves, indicating that mixed macromolecular crowding agents are more favorable to MM-CK folding and can be used to reflect the physiological environment more accurately than single crowding agents.
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Affiliation(s)
- Fen Du
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
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25
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Zhang Y, Amsden BG. Application of an Obstruction-Scaling Model To Diffusion of Vitamin B12 and Proteins in Semidilute Alginate Solutions. Macromolecules 2005. [DOI: 10.1021/ma0522357] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yu Zhang
- Department of Chemical Engineering, Queen's University, Kingston ON, Canada K7L 3N6
| | - Brian G. Amsden
- Department of Chemical Engineering, Queen's University, Kingston ON, Canada K7L 3N6
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26
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Jena SS, Bloomfield VA. Probe Diffusion in Concentrated Polyelectrolyte Solutions: Effect of Background Interactions on Competition between Electrostatic and Viscous Forces. Macromolecules 2005. [DOI: 10.1021/ma0521304] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sidhartha S. Jena
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, Minnesota 55455
| | - Victor A. Bloomfield
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, Minnesota 55455
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27
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Jena SS, Bloomfield VA. Probe Diffusion in Concentrated Polyelectrolyte Solutions: Effect of Probe Charge on Large Deviations from Stokes−Einstein Behavior. Macromolecules 2005. [DOI: 10.1021/ma052131w] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sidhartha S. Jena
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, Minnesota 55455
| | - Victor A. Bloomfield
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, Minnesota 55455
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28
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Banks DS, Fradin C. Anomalous diffusion of proteins due to molecular crowding. Biophys J 2005; 89:2960-71. [PMID: 16113107 PMCID: PMC1366794 DOI: 10.1529/biophysj.104.051078] [Citation(s) in RCA: 470] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2004] [Accepted: 08/03/2005] [Indexed: 11/18/2022] Open
Abstract
We have studied the diffusion of tracer proteins in highly concentrated random-coil polymer and globular protein solutions imitating the crowded conditions encountered in cellular environments. Using fluorescence correlation spectroscopy, we measured the anomalous diffusion exponent alpha characterizing the dependence of the mean-square displacement of the tracer proteins on time, r(2)(t) approximately t(alpha). We observed that the diffusion of proteins in dextran solutions with concentrations up to 400 g/l is subdiffusive (alpha < 1) even at low obstacle concentration. The anomalous diffusion exponent alpha decreases continuously with increasing obstacle concentration and molecular weight, but does not depend on buffer ionic strength, and neither does it depend strongly on solution temperature. At very high random-coil polymer concentrations, alpha reaches a limit value of alpha(l) approximately 3/4, which we take to be the signature of a coupling between the motions of the tracer proteins and the segments of the dextran chains. A similar, although less pronounced, subdiffusive behavior is observed for the diffusion of streptavidin in concentrated globular protein solutions. These observations indicate that protein diffusion in the cell cytoplasm and nucleus should be anomalous as well, with consequences for measurements of solute diffusion coefficients in cells and for the modeling of cellular processes relying on diffusion.
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Affiliation(s)
- Daniel S Banks
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
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29
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Liedl T, Keller S, Simmel FC, Rädler JO, Parak WJ. Fluorescent nanocrystals as colloidal probes in complex fluids measured by fluorescence correlation spectroscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2005; 1:997-1003. [PMID: 17193385 DOI: 10.1002/smll.200500108] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The diffusion properties of fluorescent colloidal CdSe and CdSe/ZnS nanocrystals (QDs) with different hydrophilic coatings were characterized in complex fluids such as actin solutions using fluorescence correlation spectroscopy (FCS). The hydrodynamic radii of the QDs were determined both in organic solvents and water. Attention was given to the potential artifacts arising from the fluorescence properties of the QDs. With increasing excitation intensities, the apparent particle concentration and diffusion times are overestimated if using a simple diffusion model. This can be explained by a numerical simulation. The diffusion behavior of QDs in actin networks of different concentrations was determined to demonstrate the potential use of nanocrystals as probes in soft biological matter. The decreasing diffusion coefficient of the nanocrystals with increasing actin concentration results in an intrinsic polymer viscosity of 0.12+/-0.02 ml mg(-1), in accordance with literature values.
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Affiliation(s)
- Tim Liedl
- LMU München, Department für Physik, Amalienstrasse 54, 80799 München, Germany
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30
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Terefe NS, Delele MA, Van Loey A, Hendrickx M. Effects of cryostabilizers, low temperature, and freezing on the kinetics of the pectin methylesterase-catalyzed de-esterification of pectin. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2005; 53:2282-2288. [PMID: 15769169 DOI: 10.1021/jf048813k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The kinetics of the pectin methylesterase (PME)-catalyzed de-esterification of pectin was studied at 25 degrees C in the presence of sucrose, fructose, maltodextrin (DE = 16.5-19.5), and carboxymethylcellulose at different concentrations and in the presence of maltodextrin and sucrose at different concentrations in a temperature range between +25 and -4 degrees C in subcooled and frozen states. The objective was to determine whether the reaction is diffusion-controlled, to gain insight about the factors determining the diffusion of the reactants, and to determine the effect of the carbohydrates, low temperature, and freezing on the structural conformation of the enzyme. The results indicate that the PME-catalyzed de-esterification of pectin is diffusion-controlled. Nevertheless, the diffusion is not controlled by the macroviscosity of the reaction medium, but rather by the microviscosity experienced by the diffusants. Low temperature in the temperature range studied does not affect the structural conformation of the enzyme, while freezing seems to have some effect.
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Affiliation(s)
- Netsanet Shiferaw Terefe
- Laboratory of Food Technology, Department of Food and Microbial Technology, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
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31
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Minton AP. Models for excluded volume interaction between an unfolded protein and rigid macromolecular cosolutes: macromolecular crowding and protein stability revisited. Biophys J 2004; 88:971-85. [PMID: 15596487 PMCID: PMC1305169 DOI: 10.1529/biophysj.104.050351] [Citation(s) in RCA: 275] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Statistical-thermodynamic models for the excluded volume interaction between an unfolded polypeptide chain and a hard sphere or hard rod cosolute are presented, permitting estimation of the free energy of transfer of a polypeptide chain with fixed radius of gyration from a dilute (ideal) solution to a solution containing volume fraction of either cosolute. Also presented is a general thermodynamic description of the equilibrium between a unique native state and a manifold of unfolded or partially unfolded states of a protein distinguished by their respective radii of gyration. Together with results of a Monte Carlo calculation of the distribution of radii of gyration of four different unfolded proteins published by Goldenberg in 2003, these models are used to estimate the effect of intermolecular excluded volume upon an experimentally measurable apparent two-state constant for equilibrium between native and nonnative conformations of each of the four proteins, and upon the experimentally measurable root mean-square radius of gyration of the unfolded protein. Model calculations predict that addition of inert cosolutes at volume fractions exceeding 0.1 stabilizes the native state relative to unfolded states by an amount that increases strongly with and with the size of the native protein relative to the size of inert cosolute, and results in significant compaction of the manifold of unfolded states. Predicted effects are in qualitative and/or semiquantitative accord with the results of several published experimental studies.
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Affiliation(s)
- Allen P Minton
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, United States Department of Health and Human Services, Bethesda, MD 20892-0830, USA.
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32
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Thorne RG, Hrabetová S, Nicholson C. Diffusion of epidermal growth factor in rat brain extracellular space measured by integrative optical imaging. J Neurophysiol 2004; 92:3471-81. [PMID: 15269225 DOI: 10.1152/jn.00352.2004] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Epidermal growth factor (EGF) stimulates proliferation, process outgrowth, and survival in the CNS. Understanding the actions of EGF necessitates characterizing its distribution in brain tissue following drug delivery or release from cellular sources. We used the integrative optical imaging (IOI) method to measure diffusion of fluorescently labeled EGF (6,600 Mr; 4 microg/ml) in the presence of excess unlabeled EGF (90 microg/ml) to compete off specific receptor binding and reveal the "true" EGF diffusion coefficient following injection in rat brain slices (400 microm). The effective diffusion coefficient was 5.18 +/- 0.16 x 10(-7) (SE) cm2/s (n = 22) in rat somatosensory cortex and the free diffusion coefficient, determined in dilute agarose gel, was 16.6 +/- 0.12 x 10(-7) cm2/s (n = 27). Tortuosity (lambda), a parameter representing the hindrance imposed on EGF by the convoluted brain extracellular space (ECS), was 1.8, the lowest yet measured by IOI for a protein in brain. Control experiments with fluorescent dextran of similar molecular weight and tetramethylammonium confirmed EGF did not affect local ECS structure. We conclude that transport of smaller growth factors such as EGF through brain ECS is less hindered than that of larger proteins (>10,000 Mr, e.g., nerve growth factor) where typically lambda > 2.1. Modeling was used to predict that low lambda will allow EGF sources in the brain to be further from target cells and still elicit a biological response. High lambda values for larger growth factors imply more constrained local biological effects than with smaller proteins such as EGF.
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Affiliation(s)
- Robert G Thorne
- Department of Physiology and Neuroscience, New York University School of Medicine, New York, New York 10016, USA.
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33
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Kozer N, Schreiber G. Effect of Crowding on Protein–Protein Association Rates: Fundamental Differences between Low and High Mass Crowding Agents. J Mol Biol 2004; 336:763-74. [PMID: 15095986 DOI: 10.1016/j.jmb.2003.12.008] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2003] [Revised: 11/28/2003] [Accepted: 12/03/2003] [Indexed: 11/16/2022]
Abstract
Physiological media constitutes a crowded environment that serves as the field of action for protein-protein interaction in vivo. Measuring protein-protein interaction in crowded solutions can mimic this environment. In this work we follow the process of protein-protein association and its rate constants (k(on)) of the beta-lactamase (TEM)-beta-lactamase inhibitor protein (BLIP) complex in crowded solution using both low and high molecular mass crowding agents. In all crowded solutions (0-40% (w/w) of ethylene glycol (EG), poly(ethylene glycol) (PEG) 200, 1000, 3350, 8000 Da Ficoll-70 and Haemaccel the measured absolute k(on), but not k(off) values, were found to be slower as compared to buffer. However, there is a fundamental difference between low and high mass crowding agents. In the presence of low mass crowding agents and Haemaccel k(on) depends inversely on the solution viscosity. In high mass polymer solutions k(on) changes only slightly, even at viscosities 12-fold higher than water. The border between low and high molecular mass polymers is sharp and is dictated by the ratio between the polymer length (L) and its persistence length (Lp). Polymers that are long enough to form a flexible coil (L/Lp > 2) behave as high molecular mass polymers and those who are unable to do so (L/Lp < 2) behave as low molecular mass polymers. We concluded that although polymers solution are crowded, this property is not uniform; i.e. there are areas in the solution that contain bulk water, and in these areas proteins can diffuse and associate almost as if they were in diluted environment. This porous medium may be taken as mimicking some aspects of the cellular environment, where many of the macromolecules are organized along membranes and the cytoskeleton. To determine the contribution of electrostatic attraction between proteins in crowded milieu, we followed k(on) of wt-TEM and three BLIP analogs with up to 100-fold increased values of k(on) due to electrostatic steering. Faster associating BLIP variants keep their relative advantage in all crowded solutions, including Haemaccel. This result suggests that faster associating protein complexes keep their advantage also in complex environment.
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Affiliation(s)
- Noga Kozer
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100 Israel
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34
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Mangenot S, Keller S, Rädler J. Transport of nucleosome core particles in semidilute DNA solutions. Biophys J 2003; 85:1817-25. [PMID: 12944295 PMCID: PMC1303354 DOI: 10.1016/s0006-3495(03)74610-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2002] [Accepted: 05/19/2003] [Indexed: 11/19/2022] Open
Abstract
We studied the diffusion of native and trypsinized nucleosome core particles (NCPs), in aqueous solution and in concentrated DNA solutions (0.25-100 mg/ml) using fluorescence correlation spectroscopy (FCS). The highest DNA concentrations studied mimic the DNA density inside the cell nucleus. The diffusion coefficient of freely diffusing NCPs depends on the presence or absence of histone tails and is affected by the salt concentration due to the relaxation effect of counterions. NCPs placed in a network of long DNA molecules (30-50 kbp) reveal anomalous diffusion. We demonstrate that NCPs diffusion is in agreement with known particle transport in entangled macromolecular solutions as long as the histone tails are folded onto the particles. In contrast, when these tails are unfolded, the reversible adsorption of NCPs onto the DNA network has to be taken into account. This is confirmed by the fact that removal of the tails leads to reduction of the interaction between NCPs and the DNA network. The findings suggest that histone tail bridging plays an important role in chromatin dynamics.
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Affiliation(s)
- Stéphanie Mangenot
- Ludwig-Maximilians-Universität, Sektion Physik, Geschwister-Scholl-Platz 1, D-80539 Munich, Germany
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35
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Thorne RG, Frey WH. Delivery of neurotrophic factors to the central nervous system: pharmacokinetic considerations. Clin Pharmacokinet 2002; 40:907-46. [PMID: 11735609 DOI: 10.2165/00003088-200140120-00003] [Citation(s) in RCA: 364] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Neurotrophic factors are proteins with considerable potential in the treatment of central nervous system (CNS) diseases and traumatic injuries. However, a significant challenge to their clinical use is the difficulty associated with delivering these proteins to the CNS. Neurotrophic factors are hydrophilic, typically basic, monomeric or dimeric proteins, mostly in the size range of 5 to 30 kDa. Neurotrophic factors potently support the development, growth and survival of neurons, eliciting biological effects at concentrations in the nanomolar to femtomolar range. They are not orally bioavailable and the blood-brain and blood-cerebrospinal fluid barriers severely limit their ability to enter into and act on sites in the CNS following parenteral systemic routes of administration. Most neurotrophic factors have short in vivo half-lives and poor pharmacokinetic profiles. Their access to the CNS is restricted by rapid enzymatic inactivation, multiple clearance processes, potential immunogenicity and sequestration by binding proteins and other components of the blood and peripheral tissues. The development of targeted drug delivery strategies for neurotrophic factors will probably determine their clinical effectiveness for CNS conditions. Achieving significant CNS target site concentrations while limiting systemic exposure and distribution to peripheral sites of action will lessen unwanted pleiotropic effects and toxicity. Local introduction of neurotrophic factors into the CNS intraparenchymally by direct injection/infusion or by implantation of delivery vectors such as polymer matrices or genetically modified cells yields the highest degree of targeting, but is limited by diffusion restrictions and invasiveness. Delivery of neurotrophic factors into the cerebrospinal fluid (CSF) following intracerebroventricular or intrathecal administration is less invasive and allows access to a much wider area of the CNS through CSF circulation pathways. However, diffusional and cellular barriers to penetration into surrounding CNS tissue and significant clearance of CSF into the venous and lymphatic circulation are also limiting. Unconventional delivery strategies such as intranasal administration may offer some degree of CNS targeting with minimal invasiveness. This review presents a summary of the neurotrophic factors and their indications for CNS disorders, their physicochemical characteristics and the different approaches that have been attempted or suggested for their delivery to the CNS. Future directions for further research such as the potential for CNS disease treatment utilising combinations of neurotrophic factors, displacement strategies, small molecule mimetics, chimaeric molecules and gene therapy are also discussed.
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Affiliation(s)
- R G Thorne
- Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota, USA
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