51
|
Affiliation(s)
- SeongMin Jeong
- Asia Pacific Center for Theoretical Physics/Department of Physics; POSTECH Pohang Korea
| | - Xin Zhou
- School of Physics; University of Chinese Academy of Sciences; Beijing China)
| | - Ekaterina B. Zhulina
- Institute of Macromolecular Compounds of the Russian Academy of Sciences and ITMO-University; St. Petersburg Russia)
| | - YongSeok Jho
- Asia Pacific Center for Theoretical Physics/Department of Physics; POSTECH Pohang Korea
| |
Collapse
|
52
|
Kolesnikov AL, Budkov YA, Nogovitsyn EA. Coarse-Grained Model of Glycosaminoglycans in Aqueous Salt Solutions. A Field-Theoretical Approach. J Phys Chem B 2014; 118:13037-49. [DOI: 10.1021/jp503749a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrei L. Kolesnikov
- Institut
fur Nichtklassische Chemie e.V., Universität Leipzig, 04109 Leipzig, Germany
- Department
of Physics, Ivanovo State University, Ermaka 39, 153025 Ivanovo, Russia
| | - Yurij A. Budkov
- Institute
of Solution Chemistry, Russian Academy of Sciences 153045, Academicheskaya 1, Ivanovo, Russia
- National Research University Higher School of Economics, 101000 Moscow, Russia
| | | |
Collapse
|
53
|
Ingólfsson HI, Lopez CA, Uusitalo JJ, de Jong DH, Gopal SM, Periole X, Marrink SJ. The power of coarse graining in biomolecular simulations. WILEY INTERDISCIPLINARY REVIEWS. COMPUTATIONAL MOLECULAR SCIENCE 2014; 4:225-248. [PMID: 25309628 PMCID: PMC4171755 DOI: 10.1002/wcms.1169] [Citation(s) in RCA: 325] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Computational modeling of biological systems is challenging because of the multitude of spatial and temporal scales involved. Replacing atomistic detail with lower resolution, coarse grained (CG), beads has opened the way to simulate large-scale biomolecular processes on time scales inaccessible to all-atom models. We provide an overview of some of the more popular CG models used in biomolecular applications to date, focusing on models that retain chemical specificity. A few state-of-the-art examples of protein folding, membrane protein gating and self-assembly, DNA hybridization, and modeling of carbohydrate fibers are used to illustrate the power and diversity of current CG modeling.
Collapse
Affiliation(s)
- Helgi I Ingólfsson
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of GroningenGroningen, The Netherlands
| | - Cesar A Lopez
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of GroningenGroningen, The Netherlands
| | - Jaakko J Uusitalo
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of GroningenGroningen, The Netherlands
| | - Djurre H de Jong
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of GroningenGroningen, The Netherlands
| | - Srinivasa M Gopal
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of GroningenGroningen, The Netherlands
| | - Xavier Periole
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of GroningenGroningen, The Netherlands
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of GroningenGroningen, The Netherlands
| |
Collapse
|
54
|
Jiang L, Titmuss S, Klein J. Interactions of hyaluronan layers with similarly charged surfaces: the effect of divalent cations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:12194-12202. [PMID: 24011082 DOI: 10.1021/la401931y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We used colloidal probe atomic force microscopy to measure the normal forces between the surface of a silica colloidal particle and a sparse layer of hyaluronan (hyaluronic acid, HA, MW ≈ 10(6) Da) covalently attached to a planar silica surface, both across pure water and following the addition of 1 mM MgCl2. It was found that in the absence of salt the HA layer repelled the colloidal silica surface during both approach and retraction. The addition of the MgCl2, however, changes the net force between the negatively charged HA layer and the opposing negatively charged silica surface from repulsion to adhesion. This interaction reversal is attributed to the bridging effect of the added Mg(2+) ions. Our results provide first direct force data to support earlier simulation and predictions that such divalent cations could bridge between negative charges on opposing surfaces, leading to an overall reversal of force from repulsion to attraction.
Collapse
Affiliation(s)
- Lei Jiang
- State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, China University of Petroleum , 66 Changjiang West Road, Qingdao, Shandong 266580, P. R. China
| | | | | |
Collapse
|
55
|
Ko LS, Quinn TM. Matrix fixed charge density modulates exudate concentration during cartilage compression. Biophys J 2013; 104:943-50. [PMID: 23442973 DOI: 10.1016/j.bpj.2012.12.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 12/06/2012] [Accepted: 12/17/2012] [Indexed: 10/27/2022] Open
Abstract
Electrolyte filtration arises due to the presence of fixed charges in cartilage extracellular matrix glycosaminoglycans (GAGs). Commonly assumed negligible, it can be important for design and interpretation of streaming potential measurements and modeling assumptions. To quantify the scale of this phenomenon, chloride ion concentration in exudate of compressed cartilage was measured by Mohr's titration and explant GAG content was colorimetrically assayed. Pilot studies indicated that an appropriate strain rate for experiments was 8 × 10(-3) s(-1) to eliminate concerns of exudate evaporation and explant damage (at low and high strain rates, respectively). Exudate chloride concentration of explants equilibrated in 1× PBS was significantly (p < 0.05) lower than the bath chloride concentration at strains of 37.5, 50, and 62.5%, with clear dependence on strain magnitude. Exudate chloride concentration was also significantly lower than that of the bath when 50% strain was applied after equilibration in 0.5, 1, and 2× PBS, with a trend for an increase in this relative difference with decreasing bath concentration (p = 0.065 between 0.5 and 2× PBS). Decreasing exudate chloride concentration correlated negatively with increasing postcompression GAG concentration. No difference between exudate chloride concentration and bath chloride concentration was ever observed for compression of uncharged agarose gel controls. Findings show that exudate from compressed cartilage is dilute relative to the bath due to the presence of matrix fixed charges, and this difference can generate diffusion potentials external to the explant, which may affect streaming potential measurements particularly under conditions of low strain rates and high strains.
Collapse
Affiliation(s)
- Lok Shun Ko
- Department of Chemical Engineering, McGill University, Montreal, Quebec, Canada
| | | |
Collapse
|
56
|
Cheng X, Pinsky PM. Mechanisms of self-organization for the collagen fibril lattice in the human cornea. J R Soc Interface 2013; 10:20130512. [PMID: 23904589 DOI: 10.1098/rsif.2013.0512] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The transparency of the human cornea depends on the regular lattice arrangement of the collagen fibrils and on the maintenance of an optimal hydration--the achievement of both depends on the presence of stromal proteoglycans (PGs) and their linear sidechains of negatively charged glycosaminoglycans (GAGs). Although the GAGs produce osmotic pressure by the Donnan effect, the means by which they exert positional control of the lattice is less clear. In this study, a theoretical model based on equilibrium thermodynamics is used to describe restoring force mechanisms that may control and maintain the fibril lattice and underlie corneal transparency. Electrostatic-based restoring forces that result from local charge density changes induced by fibril motion, and entropic elastic restoring forces that arise from duplexed GAG structures that bridge neighbouring fibrils, are described. The model allows for the possibility that fibrils have a GAG-dense coating that adds an additional fibril force mechanism preventing fibril aggregation. Swelling pressure predictions are used to validate the model with results showing excellent agreement with experimental data over a range of hydration from 30 to 200% of normal. The model suggests that the electrostatic restoring force is dominant, with the entropic forces from GAG duplexes being an order or more smaller. The effect of a random GAG organization, as observed in recent imaging, is considered in a dynamic model of the lattice that incorporates randomness in both the spatial distribution of GAG charge and the topology of the GAG duplexes. A striking result is that the electrostatic restoring forces alone are able to reproduce the image-based lattice distribution function for the human cornea, and thus dynamically maintain the short-range order of the lattice.
Collapse
Affiliation(s)
- Xi Cheng
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | | |
Collapse
|
57
|
Sattelle BM, Shakeri J, Almond A. Does Microsecond Sugar Ring Flexing Encode 3D-Shape and Bioactivity in the Heparanome? Biomacromolecules 2013; 14:1149-59. [DOI: 10.1021/bm400067g] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Benedict M. Sattelle
- Faculty of Life Sciences, University of Manchester, Manchester
Institute of Biotechnology,
131 Princess Street, Manchester, M1 7DN, United Kingdom
| | - Javad Shakeri
- Faculty of Life Sciences, University of Manchester, Manchester
Institute of Biotechnology,
131 Princess Street, Manchester, M1 7DN, United Kingdom
| | - Andrew Almond
- Faculty of Life Sciences, University of Manchester, Manchester
Institute of Biotechnology,
131 Princess Street, Manchester, M1 7DN, United Kingdom
| |
Collapse
|
58
|
Ho YF, Shendruk TN, Slater GW, Hsiao PY. Structure of polyelectrolyte brushes subject to normal electric fields. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:2359-2370. [PMID: 23347275 DOI: 10.1021/la304267f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Molecular dynamic simulations of salt-free polyelectrolyte brushes subject to external fields applied normal to the grafting substrate reveal the three-dimensional monomer and counterion distributions. It is found that below a critical electric field, local electroneutrality holds for densely grafted brushes and the brush height remains independent of field intensity. Above this critical field (which scales as 1/3 with grafting density) brush height increases smoothly, and the fraction of condensed counterions decreases. The brush bifurcates into two subpopulations of stretched and collapsed chains when the grafting density is not low. At intermediate grafting densities, the majority of chains are stretched and the minority are nonstretched. At high grafting densities bifurcation and brush height growth occur consecutively. The majority of the chains are nonstretched at high grafting densities. Although not observed prior to overstretching of the chain model, it is predicted that the two subpopulations will re-merge to a single highly stretched phase when field intensity reaches a third critical value. The ability to control subpopulations of chains suggests that utilizing electric fields normal to polyelectrolyte brushes holds potential as controllable gates in microfluidic devices.
Collapse
Affiliation(s)
- Yu-Fan Ho
- Department of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan 300, ROC
| | | | | | | |
Collapse
|
59
|
Lee HY, Han L, Roughley PJ, Grodzinsky AJ, Ortiz C. Age-related nanostructural and nanomechanical changes of individual human cartilage aggrecan monomers and their glycosaminoglycan side chains. J Struct Biol 2012; 181:264-73. [PMID: 23270863 DOI: 10.1016/j.jsb.2012.12.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 12/10/2012] [Accepted: 12/11/2012] [Indexed: 11/15/2022]
Abstract
The nanostructure and nanomechanical properties of aggrecan monomers extracted and purified from human articular cartilage from donors of different ages (newborn, 29 and 38 year old) were directly visualized and quantified via atomic force microscopy (AFM)-based imaging and force spectroscopy. AFM imaging enabled direct comparison of full length monomers at different ages. The higher proportion of aggrecan fragments observed in adult versus newborn populations is consistent with the cumulative proteolysis of aggrecan known to occur in vivo. The decreased dimensions of adult full length aggrecan (including core protein and glycosaminoglycan (GAG) chain trace length, end-to-end distance and extension ratio) reflect altered aggrecan biosynthesis. The demonstrably shorter GAG chains observed in adult full length aggrecan monomers, compared to newborn monomers, also reflects markedly altered biosynthesis with age. Direct visualization of aggrecan subjected to chondroitinase and/or keratanase treatment revealed conformational properties of aggrecan monomers associated with chondroitin sulfate (CS) and keratan sulfate (KS) GAG chains. Furthermore, compressive stiffness of chemically end-attached layers of adult and newborn aggrecan was measured in various ionic strength aqueous solutions. Adult aggrecan was significantly weaker in compression than newborn aggrecan even at the same total GAG density and bath ionic strength, suggesting the importance of both electrostatic and non-electrostatic interactions in nanomechanical stiffness. These results provide molecular-level evidence of the effects of age on the conformational and nanomechanical properties of aggrecan, with direct implications for the effects of aggrecan nanostructure on the age-dependence of cartilage tissue biomechanical and osmotic properties.
Collapse
Affiliation(s)
- Hsu-Yi Lee
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | | | | | | | | |
Collapse
|
60
|
Wehle M, Vilotijevic I, Lipowsky R, Seeberger PH, Varon Silva D, Santer M. Mechanical Compressibility of the Glycosylphosphatidylinositol (GPI) Anchor Backbone Governed by Independent Glycosidic Linkages. J Am Chem Soc 2012; 134:18964-72. [DOI: 10.1021/ja302803r] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marko Wehle
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
| | - Ivan Vilotijevic
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
| | - Reinhard Lipowsky
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
| | - Peter H. Seeberger
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
- Department of Chemistry and
Biochemistry, Free University of Berlin, Arnimallee 22, 14195 Berlin, Germany
| | | | - Mark Santer
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
| |
Collapse
|
61
|
Cranford SW, Buehler MJ. Variation of Weak Polyelectrolyte Persistence Length through an Electrostatic Contour Length. Macromolecules 2012. [DOI: 10.1021/ma3008465] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Steven W. Cranford
- Center for Materials Science
and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United
States
- Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 1-235A&B, Cambridge, Massachusetts 02139, United States
| | - Markus J. Buehler
- Center for Materials Science
and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United
States
- Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 1-235A&B, Cambridge, Massachusetts 02139, United States
| |
Collapse
|
62
|
Abdelkebir K, Morin-Grognet S, Gaudière F, Coquerel G, Labat B, Atmani H, Ladam G. Biomimetic layer-by-layer templates for calcium phosphate biomineralization. Acta Biomater 2012; 8:3419-28. [PMID: 22683877 DOI: 10.1016/j.actbio.2012.05.035] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 05/25/2012] [Accepted: 05/30/2012] [Indexed: 10/28/2022]
Abstract
Carboxylated, sulfated and/or phosphorylated surfaces are admitted as potential optimal templates for biomimetic deposition of calcium phosphate (CaP) coatings in view of improving implants' osseointegration. Layer-by-layer films were built up consisting of anionic chondroitin sulfate (ChS), a biological carboxylated and sulfated polysaccharide and cationic poly(l-lysine) (PLL). The films were used as soft matrices to immobilize a model phosphoprotein, phosvitin (PhV). The respective roles of ChS, PLL and PhV terminal layers on the heterogeneous nucleation kinetics and the structure of CaP deposits obtained from supersaturated solutions were inspected. Critical supersaturation ratios and induction times preceding heterogeneous nucleation were precisely determined and interpreted within the framework of classical nucleation theory in order to derive the effective interfacial energies of CaP crystals. It was found that the potency of terminal layers toward CaP nucleation increased in the order: PLL<ChS<PhV. Beyond a supersaturation threshold, PhV-terminated films exerted unique influence on the nucleation kinetics, maintaining the induction time at a constant value owing to conformational change of the PhV molecules upon calcium bridging. Promisingly, all films templated the deposition of thin (a few micrometer thick) uniform coatings of octacalcium phosphate and possibly hydroxyapatite, the two most relevant biological phases of CaP.
Collapse
|
63
|
Sulfated hyaluronan and chondroitin sulfate derivatives interact differently with human transforming growth factor-β1 (TGF-β1). Acta Biomater 2012; 8:2144-52. [PMID: 22426137 DOI: 10.1016/j.actbio.2012.03.021] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 02/07/2012] [Accepted: 03/08/2012] [Indexed: 11/22/2022]
Abstract
This study demonstrates that the modification of hyaluronan (hyaluronic acid; Hya) and chondroitin sulfate (CS) with sulfate groups leads to different binding affinities for recombinant human transforming growth factor-β1 (TGF-β1) for comparable average degrees of sulfation (DS). In general, Hya derivates showed higher binding strength than CS derivatives. In either case, a higher degree of sulfation leads to a stronger interaction. The high-sulfated hyaluronan sHya3 (average DS≈3) exhibited the tightest interaction with TGF-β1, as determined by surface plasmon resonance and enzyme-linked immunosorbent assay. The binding strength was significantly weakened by carboxymethylation. Unmodified Hya and low-sulfated, native CS showed weak or no binding affinity. The interaction characteristics of the different sulfated glycosaminoglycans are promising for incorporation into bioengineered coatings of biomaterials to modulate growth factor binding in medical applications.
Collapse
|
64
|
Horkay F, Basser PJ, Hecht AM, Geissler E. Chondroitin Sulfate in Solution: Effects of Mono- and Divalent Salts. Macromolecules 2012; 45:2882-2890. [PMID: 23814316 PMCID: PMC3694629 DOI: 10.1021/ma202693s] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Chondroitin sulphate (CS) is a linear sulfated polysaccharide found in cartilage and other tissues in the body. Small angle neutron scattering (SANS) and dynamic light scattering (DLS) measurements are made on semi-dilute CS solutions to determine ion induced changes in the local order of the CS chains and in their dynamic properties. In salt-free CS solutions SANS detects the correlation peak due to local ordering between adjacent chains in which the characteristic interchain distance is d ≈ 57 Å. In both monovalent and divalent salts (NaCl and CaCl2) aligned linear regions are distinguishable corresponding to distance scales ranging from the length of the monomer unit (8 Å) to about 1000 Å. With increasing calcium ion concentration, the scattering intensity increases. Even in the presence of 200 mM CaCl2, however, neither phase separation nor cross-linking occurs. DLS in the CS solutions reveals two characteristic relaxation modes, the fast mode corresponding to the thermal concentration fluctuations. The collective diffusion coefficient D decreases with increasing calcium ion concentration and exhibits a power law function of the single variable c/J, where c is the CS concentration and J is the ionic strength of the salt in the solution. This result implies that the effect of the sodium and calcium ions on the dynamic properties of CS solutions is fully accounted for by the ionic strength.
Collapse
Affiliation(s)
- Ferenc Horkay
- Section on Tissue Biophysics and Biomimetics, Program in Pediatric Imaging and Tissue Science, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 13 South Drive, Bethesda, MD 20892, USA
| | - Peter J. Basser
- Section on Tissue Biophysics and Biomimetics, Program in Pediatric Imaging and Tissue Science, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 13 South Drive, Bethesda, MD 20892, USA
| | - Anne-Marie Hecht
- Laboratoire Interdisciplinaire de Physique CNRS UMR 5588, Université J. Fourier de Grenoble, B.P.87, 38402 St Martin d'Hères cedex, France
| | - Erik Geissler
- Laboratoire Interdisciplinaire de Physique CNRS UMR 5588, Université J. Fourier de Grenoble, B.P.87, 38402 St Martin d'Hères cedex, France
| |
Collapse
|
65
|
Ruberti JW, Sokoloff JB. Theory of the short time mechanical relaxation in articular cartilage. J Biomech Eng 2012; 133:104504. [PMID: 22070338 DOI: 10.1115/1.4005174] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Articular cartilage is comprised of macromolecules, proteoglycans, with (charged) chondroitin sulfate side-chains attached to them. The proteoglycans are attached to longer hyaluronic acid chains, trapped within a network of type II collagen fibrils. As a consequence of their relatively long persistence lengths, the number of persistence lengths along the chondroitin sulfate and proteoglycan chains is relatively small, and consequently, the retraction times for these side chains are also quite short. We argue that, as a consequence of this, they will not significantly inhibit the reptation of the hyaluronic acid chains. Scaling arguments applied to this model allow us to show that the shortest of the mechanical relaxation times of cartilage, that have been determined by Fyhrie and Barone to be due to reptation of the hyaluronic acid polymers, should have a dependence on the load, i.e., force per unit interface area P, carried by the cartilage, proportional to P(3/2).
Collapse
Affiliation(s)
- J W Ruberti
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA
| | | |
Collapse
|
66
|
Chandran PL, Horkay F. Aggrecan, an unusual polyelectrolyte: review of solution behavior and physiological implications. Acta Biomater 2012; 8:3-12. [PMID: 21884828 DOI: 10.1016/j.actbio.2011.08.011] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 08/03/2011] [Accepted: 08/11/2011] [Indexed: 10/17/2022]
Abstract
Aggrecan is a high-molecular-weight, bottlebrush-shaped, negatively charged biopolymer that forms supermolecular complexes with hyaluronic acid. In the extracellular matrix of cartilage, aggrecan-hyaluronic acid complexes are interspersed in a collagen meshwork and provide the osmotic properties required to resist deswelling under compressive load. In this review we compile aggrecan solution behavior from different experimental techniques, and discuss them in the context of concentration regimes that were identified in osmotic pressure experiments. At low concentrations, aggrecan exhibits microgel-like behavior. With increasing concentration, the bottlebrushes self-assemble into large complexes. In the physiological concentration range (2<c(aggrecan)<8% w/w), the physical properties of the solution are dominated by repulsive electrostatic interactions between aggrecan complexes. We discuss the consequences of the bottlebrush architecture on the polyelectrolyte characteristics of the aggrecan molecule, and its implications for cartilage properties and function.
Collapse
|
67
|
Abdelkebir K, Gaudière F, Morin-Grognet S, Coquerel G, Atmani H, Labat B, Ladam G. Protein-triggered instant disassembly of biomimetic Layer-by-Layer films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:14370-14379. [PMID: 22007998 DOI: 10.1021/la2033109] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Layer-by-Layer (LbL) coatings are promising tools for the biofunctionalization of biomaterials, as they allow stress-free immobilization of proteins. Here, we explore the possibility to immobilize phosvitin, a highly phosphorylated protein viewed as a model of bone phosphoproteins and, as such, a potential promotive agent of surface-directed biomineralization, into biomimetic LbL architectures. Two immobilization protocols are attempted, first, using phosvitin as the polyanionic component of phosvitin/poly-(L-lysine) films and, second, adsorbing it onto preformed chondroitin sulfate/poly-(L-lysine) films. Surprisingly, it is neither possible to embed phosvitin as the constitutive polyanion of the LbL architectures nor to adsorb it atop preformed films. Instead, phosvitin triggers instant massive film disassembly. This unexpected, incidentally detected behavior constitutes the first example of destructive interactions between LbL films and a third polyelectrolyte, a fortiori a protein, which might open a route toward new stimuli-responsive films for biosensing or drug delivery applications. Interestingly, additional preliminary results still indicate a promotive effect of phosvitin-containing remnant films on calcium phosphate deposition.
Collapse
Affiliation(s)
- Khalil Abdelkebir
- Laboratoire de Biophysique et Biomatériaux (La2B), SMS EA 3233, IMR FED 4114, Université de Rouen, Centre Universitaire d'Evreux, 1 rue du 7ème Chasseurs, BP 281, 27002 Evreux Cedex, France
| | | | | | | | | | | | | |
Collapse
|
68
|
Seror J, Merkher Y, Kampf N, Collinson L, Day AJ, Maroudas A, Klein J. Articular Cartilage Proteoglycans As Boundary Lubricants: Structure and Frictional Interaction of Surface-Attached Hyaluronan and Hyaluronan–Aggrecan Complexes. Biomacromolecules 2011; 12:3432-43. [DOI: 10.1021/bm2004912] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jasmine Seror
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Yulia Merkher
- Department of Biomedical Engineering, Technion Institute of Technology, Haifa 32000, Israel
| | - Nir Kampf
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Lisa Collinson
- Wellcome Trust Center for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Anthony J. Day
- Wellcome Trust Center for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Alice Maroudas
- Department of Biomedical Engineering, Technion Institute of Technology, Haifa 32000, Israel
| | - Jacob Klein
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, 76100, Israel
| |
Collapse
|
69
|
Han L, Grodzinsky AJ, Ortiz C. Nanomechanics of the Cartilage Extracellular Matrix. ANNUAL REVIEW OF MATERIALS RESEARCH 2011; 41:133-168. [PMID: 22792042 PMCID: PMC3392687 DOI: 10.1146/annurev-matsci-062910-100431] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Cartilage is a hydrated biomacromolecular fiber composite located at the ends of long bones that enables proper joint lubrication, articulation, loading, and energy dissipation. Degradation of extracellular matrix molecular components and changes in their nanoscale structure greatly influence the macroscale behavior of the tissue and result in dysfunction with age, injury, and diseases such as osteoarthritis. Here, the application of the field of nanomechanics to cartilage is reviewed. Nanomechanics involves the measurement and prediction of nanoscale forces and displacements, intra- and intermolecular interactions, spatially varying mechanical properties, and other mechanical phenomena existing at small length scales. Experimental nanomechanics and theoretical nanomechanics have been applied to cartilage at varying levels of material complexity, e.g., nanoscale properties of intact tissue, the matrix associated with single cells, biomimetic molecular assemblies, and individual extracellular matrix biomolecules (such as aggrecan, collagen, and hyaluronan). These studies have contributed to establishing a fundamental mechanism-based understanding of native and engineered cartilage tissue function, quality, and pathology.
Collapse
Affiliation(s)
- Lin Han
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Alan J. Grodzinsky
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Christine Ortiz
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| |
Collapse
|
70
|
Boddohi S, Kipper MJ. Engineering nanoassemblies of polysaccharides. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:2998-3016. [PMID: 20593437 DOI: 10.1002/adma.200903790] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Polysaccharides offer a wealth of biochemical and biomechanical functionality that can be used to develop new biomaterials. In mammalian tissues, polysaccharides often exhibit a hierarchy of structure, which includes assembly at the nanometer length scale. Furthermore, their biochemical function is determined by their nanoscale organization. These biological nanostructures provide the inspiration for developing techniques to tune the assembly of polysaccharides at the nanoscale. These new polysaccharide nanostructures are being used for the stabilization and delivery of drugs, proteins, and genes, the engineering of cells and tissues, and as new platforms on which to study biochemistry. In biological systems polysaccharide nanostructures are assembled via bottom-up processes. Many biologically derived polysaccharides behave as polyelectrolytes, and their polyelectrolyte nature can be used to tune their bottom-up assembly. New techniques designed to tune the structure and composition of polysaccharides at the nanoscale are enabling researchers to study in detail the emergent biological properties that arise from the nanoassembly of these important biological macromolecules.
Collapse
Affiliation(s)
- Soheil Boddohi
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO, USA
| | | |
Collapse
|
71
|
Less is more when simulating unsulfated glycosaminoglycan 3D-structure: Comparison of GLYCAM06/TIP3P, PM3-CARB1/TIP3P, and SCC-DFTB-D/TIP3P predictions with experiment. J Comput Chem 2010; 31:2932-47. [DOI: 10.1002/jcc.21589] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
72
|
Leermakers FAM, Zhulina EB. How the projection domains of NF-L and alpha-internexin determine the conformations of NF-M and NF-H in neurofilaments. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2010; 39:1323-34. [PMID: 20213320 DOI: 10.1007/s00249-010-0585-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 01/25/2010] [Accepted: 02/08/2010] [Indexed: 02/06/2023]
Abstract
Making use of a numerical self-consistent field method and polymer brush concepts, we model the solvated corona of neurofilaments (NF) composed of projection domains (unstructured tails) of constituent proteins. Projections are modeled with amino acid resolution. We focus on the importance of the two shortest ones (alpha-internexin and NF-L) in regulating the conformations of the two longer ones (NF-M and NF-H) in an isolated NF. We take the wild-type NF with no alpha-internexin as the reference, for which the phosphorylation-induced translocation of M- and H-tails has been examined previously. We demonstrate that a subbrush of L-tails creates an electrostatic potential profile with an approximately parabolic shape. An experimentally relevant (2:1) ratio of L- to alpha-projections reduces the charge density of the L subbrush and shifts the translocation transition of the H-tails to slightly higher degrees of phosphorylation. Replacing all L-tails by alpha-projections destroys the substructure of the NF corona and this alters the NF response to the phosphorylation of long tails.
Collapse
|
73
|
Hart FX. Cytoskeletal forces produced by extremely low-frequency electric fields acting on extracellular glycoproteins. Bioelectromagnetics 2010; 31:77-84. [PMID: 19593781 DOI: 10.1002/bem.20525] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The physical mechanism by which cells transduce an applied electric field is not well understood. This article establishes for the first time a direct, quantitative model that links the field to cytoskeletal forces. In a previous article, applied electric fields of physiological strength were shown to produce significant mechanical torques at the cellular level. In this article, the corresponding forces exerted on the cytoskeleton are computed and found to be comparable in magnitude to mechanical forces known to produce physiological effects. In addition to the electrical force, the viscous drag force exerted by the surrounding medium and the restoring force exerted by the neighboring structures are considered in the analysis. For an applied electric field of 10 V/m, the force transmitted to the CD44 receptor of a hyaluronan chain in cartilage is about 1 pN at 10 Hz and 7 pN at 1 Hz. For an applied electric field of 100 V/m, the force transmitted to the cytoskeleton at one focus of the glycocalyx is about 0.5 pN at 10 Hz and 1.3 pN at 1 Hz. Mechanical forces of similar magnitude have been observed to produce physiological effects. Hence, this electromechanical transduction process is a plausible mechanism for the production of physiological effects by such electric fields.
Collapse
Affiliation(s)
- Francis X Hart
- Department of Physics, The University of the South, Sewanee, Tennessee 37383, USA.
| |
Collapse
|
74
|
López CA, Rzepiela AJ, de Vries AH, Dijkhuizen L, Hünenberger PH, Marrink SJ. Martini Coarse-Grained Force Field: Extension to Carbohydrates. J Chem Theory Comput 2009; 5:3195-210. [DOI: 10.1021/ct900313w] [Citation(s) in RCA: 307] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Cesar A. López
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), Centre for Carbohydrate Bioprocessing, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands, and Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Andrzej J. Rzepiela
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), Centre for Carbohydrate Bioprocessing, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands, and Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Alex H. de Vries
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), Centre for Carbohydrate Bioprocessing, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands, and Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Lubbert Dijkhuizen
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), Centre for Carbohydrate Bioprocessing, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands, and Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Philippe H. Hünenberger
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), Centre for Carbohydrate Bioprocessing, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands, and Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Siewert J. Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), Centre for Carbohydrate Bioprocessing, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands, and Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
| |
Collapse
|
75
|
Saenz J, Toner M, Risco R. Comparison between ideal and nonideal solution models for single-cell cryopreservation protocols. J Phys Chem B 2009; 113:4853-64. [PMID: 19338369 DOI: 10.1021/jp807274z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Models for cell dehydration during a cryopreservation protocol are usually based on the hypothesis of ideal dilute solution. The strong electrolyte character of NaCl makes us revisit these models. The case of nonideal solution is analyzed by computing the dehydration curves without this additional hypothesis. The conclusion is that, in general, while the application of the ideal dilute solution hypothesis is convenient in many cases, for some specific cooling rates there exist important differences in the degree of dehydration predicted by these two models in the studied cases of mouse sperm and hepatocyte. It is shown how this finding has relevant implications for the design and optimization of cryopreservation protocols.
Collapse
Affiliation(s)
- Jaime Saenz
- Escuela Superior de Ingenieros, Universidad de Sevilla, 41092 Sevilla, Spain
| | | | | |
Collapse
|
76
|
Allen EC, Rutledge GC. Evaluating the transferability of coarse-grained, density-dependent implicit solvent models to mixtures and chains. J Chem Phys 2009; 130:034904. [PMID: 19173540 DOI: 10.1063/1.3055594] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Previously, we described a coarse-graining method for creating local density-dependent implicit solvent (DDIS) potentials that reproduce the radial distribution function (RDF) and solute excess chemical potential across a range of particle concentrations [E. C. Allen and G. C. Rutledge, J. Chem. Phys. 128, 154115 (2008)]. In this work, we test the transferability of these potentials, derived from simulations of monomeric solute in monomeric solvent, to mixtures of solutes and to solute chains in the same monomeric solvent. For this purpose, "transferability" refers to the predictive capability of the potentials without additional optimization. We find that RDF transferability to mixtures is very good, while RDF errors in systems of chains increase linearly with chain length. Excess chemical potential transferability is good for mixtures at low solute concentration, chains, and chains of mixed composition; at higher solute concentrations in mixtures, chemical potential transferability fails due to the nature of the DDIS potentials, in which particle insertion directly affects the interaction potential. With these results, we demonstrate that DDIS potentials derived for pure solutes can be used effectively in the study of many important systems including those involving mixtures, chains, and chains of mixed composition in monomeric solvent.
Collapse
Affiliation(s)
- Erik C Allen
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 USA
| | | |
Collapse
|
77
|
Baeurle S, Kiselev M, Makarova E, Nogovitsin E. Effect of the counterion behavior on the frictional–compressive properties of chondroitin sulfate solutions. POLYMER 2009. [DOI: 10.1016/j.polymer.2009.01.066] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
78
|
Wilson CG, Sisco PN, Goldsmith EC, Murphy CJ. Glycosaminoglycan-functionalized gold nanorods: interactions with cardiac cells and type I collagen. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b902760b] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
79
|
Nap RJ, Szleifer I. Structure and interactions of aggrecans: statistical thermodynamic approach. Biophys J 2008; 95:4570-83. [PMID: 18689463 PMCID: PMC2576360 DOI: 10.1529/biophysj.108.133801] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Accepted: 07/29/2008] [Indexed: 11/18/2022] Open
Abstract
Weak polyelectrolytes tethered to cylindrical surfaces are investigated using a molecular theory. These polymers form a model system to describe the properties of aggrecan molecules, which is one of the main components of cartilage. We have studied the structural and thermodynamical properties of two interacting aggrecans with a molecular density functional theory that incorporates the acid-base equilibrium as well as the molecular properties: including conformations, size, shape, and charge distribution of all molecular species. The effect of acidity and salt concentration on the behavior is explored in detail. The repulsive interactions between two cylindrical-shaped aggrecans are strongly influenced by both the salt concentration and the pH. With increasing acidity, the polyelectrolytes of the aggrecan acquire charge and with decreasing salt concentration those charges become less screened. Consequently the interactions increase in size and range with increasing acidity and decreasing salt concentration. The size and range of the forces offers a possible explanation to the aggregation behavior of aggrecans and for their ability to resist compressive forces in cartilage. Likewise, the interdigitation of two aggrecan molecules is strongly affected by the salt concentration as well as the pH. With increasing pH, the number of charges increases, causing the repulsions between the polymers to increase, leading to a lower interdigitation of the two cylindrical polymer layers of the aggrecan molecules. The low interdigitation in charged polyelectrolytes layers provides an explanation for the good lubrication properties of polyelectrolyte layers in general and cartilage in particular.
Collapse
Affiliation(s)
- Rikkert J Nap
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, USA
| | | |
Collapse
|
80
|
Abstract
Here it is reported that aggrecan, the highly negatively charged macromolecule in the cartilage extracellular matrix, undergoes Ca(2+)-mediated self-adhesion after static compression even in the presence of strong electrostatic repulsion in physiological-like solution conditions. Aggrecan was chemically end-attached onto gold-coated planar silicon substrates and gold-coated microspherical atomic force microscope probe tips (end radius R approximately 2.5 mum) at a density ( approximately 40 mg/mL) that simulates physiological conditions in the tissue ( approximately 20-80 mg/mL). Colloidal force spectroscopy was employed to measure the adhesion between opposing aggrecan monolayers in NaCl (0.001-1.0 M) and NaCl + CaCl(2) ([Cl(-)] = 0.15 M, [Ca(2+)] = 0 - 75 mM) aqueous electrolyte solutions. Aggrecan self-adhesion was found to increase with increasing surface equilibration time upon compression (0-30 s). Hydrogen bonding and physical entanglements between the chondroitin sulfate-glycosaminoglycan side chains are proposed as important factors contributing to aggrecan self-adhesion. Self-adhesion was found to significantly increase with decreasing bath ionic strength (and hence, electrostatic double-layer repulsion), as well as increasing Ca(2+) concentration due to the additional ion-bridging effects. It is hypothesized that aggrecan self-adhesion, and the macromolecular energy dissipation that results from this self-adhesion, could be important factors contributing to the self-assembled architecture and integrity of the cartilage extracellular matrix in vivo.
Collapse
|
81
|
Allen EC, Rutledge GC. A novel algorithm for creating coarse-grained, density dependent implicit solvent models. J Chem Phys 2008; 128:154115. [PMID: 18433198 DOI: 10.1063/1.2899729] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Implicit solvent simulations are those in which solvent molecules are not explicitly simulated, and the solute-solute interaction potential is modified to compensate for the implicit solvent effect. Implicit solvation is well known in Brownian dynamics of dilute solutions but offers promise to speed up many other types of molecular simulations as well, including studies of proteins and colloids where the local density can vary considerably. This work examines implicit solvent potentials within a more general coarse-graining framework. While a pairwise potential between solute sites is relatively simple and ubiquitous, an additional parametrization based on the local solute concentration has the possibility to increase the accuracy of the simulations with only a marginal increase in computational cost. We describe here a method in which the radial distribution function and excess chemical potential of solute insertion for a system of Lennard-Jones particles are first measured in a fully explicit, all-particle simulation, and then reproduced across a range of solute particle densities in an implicit solvent simulation.
Collapse
Affiliation(s)
- Erik C Allen
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | |
Collapse
|
82
|
Ding SY, Xu Q, Crowley M, Zeng Y, Nimlos M, Lamed R, Bayer EA, Himmel ME. A biophysical perspective on the cellulosome: new opportunities for biomass conversion. Curr Opin Biotechnol 2008; 19:218-27. [PMID: 18513939 DOI: 10.1016/j.copbio.2008.04.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 04/28/2008] [Accepted: 04/29/2008] [Indexed: 11/28/2022]
Abstract
The cellulosome is a multiprotein complex, produced primarily by anaerobic microorganisms, which functions to degrade lignocellulosic materials. An important topic of current debate is whether cellulosomal systems display greater ability to deconstruct complex biomass materials (e.g. plant cell walls) than nonaggregated enzymes, and in so doing would be appropriate for improved, commercial bioconversion processes. To sufficiently understand the complex macromolecular processes between plant cell wall polymers, cellulolytic microbes, and their secreted enzymes, a highly concerted research approach is required. Adaptation of existing biophysical techniques and development of new science tools must be applied to this system. This review focuses on strategies likely to permit improved understanding of the bacterial cellulosome using biophysical approaches, with emphasis on advanced imaging and computational techniques.
Collapse
Affiliation(s)
- Shi-You Ding
- Chemical and Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA.
| | | | | | | | | | | | | | | |
Collapse
|
83
|
Affiliation(s)
- Barbara Mulloy
- National Institute for Biological Standards and Control, Herts. EN6 3QG, United Kingdom
| |
Collapse
|
84
|
MINAMISAWA T, SUZUKI K, MAEDA H, SHIMOKATA S, SUGIURA N, KIMATA K, HIRABAYASHI J. Characterization of Isomeric Unsulfated Glycosaminoglycan Oligosaccharides by Mass Spectrometry/Mass Spectrometry. ACTA ACUST UNITED AC 2007. [DOI: 10.5702/massspec.55.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
85
|
Sasisekharan R, Raman R, Prabhakar V. GLYCOMICS APPROACH TO STRUCTURE-FUNCTION RELATIONSHIPS OF GLYCOSAMINOGLYCANS. Annu Rev Biomed Eng 2006; 8:181-231. [PMID: 16834555 DOI: 10.1146/annurev.bioeng.8.061505.095745] [Citation(s) in RCA: 230] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Extracellular modulation of phenotype is an emerging paradigm in this current postgenomics age of molecular and cell biology. Glycosaminoglycans (GAGs) are primary components of the cell surface and the cell-extracellular matrix (ECM) interface. Advances in the technology to analyze GAGs and in whole-organism genetics have led to a dramatic increase in the known important biological role of these complex polysaccharides. Owing to their ubiquitous distribution at the cell-ECM interface, GAGs interact with numerous proteins and modulate their activity, thus impinging on fundamental biological processes such as cell growth and development. Many recent reviews have captured important aspects of GAG structure and biosynthesis, GAG-protein interactions, and GAG biology. GAG research is currently at a stage where there is a need for an integrated systems or glycomics approach, which involves an integration of all of the above concepts to define their structure-function relationships. Focusing on heparin/heparan (HSGAGs) and chondroitin/dermatan sulfate (CSGAGs), this review highlights the important aspects of GAGs and summarizes these aspects in the context of taking a glycomics approach that integrates the different technologies to define structure-function relationships of GAGs.
Collapse
Affiliation(s)
- Ram Sasisekharan
- Biological Engineering Division, Center for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
| | | | | |
Collapse
|
86
|
Abstract
Endothelial cells (ECs) line all blood vessel walls and are exposed to the mechanical forces of blood flow which modulate their function and play a role in vascular regulation, remodelling and disease. The principal mechanical forces sensed by ECs are the shear stress of flowing blood on their apical surface, and the circumferential stress resisting blood pressure, which induces stretch in the cell body. 'Mechanotransduction' refers to the mechanisms by which these forces are transduced into biomolecular responses of the cells. Given the importance of endothelial mechanotransduction in cardiovascular physiology and pathology, numerous research efforts have been dedicated to identifying the mechanosensory component(s) of ECs. This review focuses on mechanotransduction of shear stress by ECs and considers the evidence in support of the surface glycocalyx acting as a mechanotransducer.
Collapse
Affiliation(s)
- J M Tarbell
- Biomedical Engineering Department, The City College of New York, CUNY, New York, NY 10031, USA.
| | | |
Collapse
|
87
|
Dean D, Han L, Grodzinsky AJ, Ortiz C. Compressive nanomechanics of opposing aggrecan macromolecules. J Biomech 2005; 39:2555-65. [PMID: 16289077 DOI: 10.1016/j.jbiomech.2005.09.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Accepted: 09/05/2005] [Indexed: 11/28/2022]
Abstract
In this study, we have measured the nanoscale compressive interactions between opposing aggrecan macromolecules in near-physiological conditions, in order to elucidate the molecular origins of tissue-level cartilage biomechanical behavior. Aggrecan molecules from fetal bovine epiphyseal cartilage were chemically end-grafted to planar substrates, standard nanosized atomic force microscopy (AFM) probe tips (R(tip) approximately 50 nm), and larger colloidal probe tips (R(tip) approximately 2.5 microm). To assess normal nanomechanical interaction forces between opposing aggrecan layers, substrates with microcontact printed aggrecan were imaged using contact mode AFM, and aggrecan layer height (and hence deformation) was measured as a function of solution ionic strength (IS) and applied normal load. Then, using high-resolution force spectroscopy, nanoscale compressive forces between opposing aggrecan on the tip and substrate were measured versus tip-substrate separation distance in 0.001-1M NaCl. Nanosized tips enabled measurement of the molecular stiffness of 2-4 aggrecan while colloidal tips probed the nanomechanical properties of larger assemblies (approximately 10(4) molecules). The compressive stiffness of aggrecan was much higher when using a densely packed colloidal tip than the stiffness measured for using the nanosized tip with a few aggrecan, demonstrating the importance of lateral interactions to the normal nanomechanical properties. The measured stress at 0.1M NaCl (near-physiological ionic strength) increased sharply at aggrecan densities under the tip of approximately 40 mg/ml (physiological densities are approximately 20-80 mg/ml), corresponding to an average inter-GAG spacing of 4-5 Debye lengths (4-5 nm); this characteristic spacing is consistent with the onset of significant electrostatic interactions between GAG chains of opposing aggrecan molecules. Comparison of nanomechanical data to the predictions of Poisson-Boltzmann-based models further elucidated the regimes over which electrostatic and nonelectrostatic interactions affect aggrecan stiffness in compression. The most important aspects of this study include: the incorporation of experiments at two different length scales, the use of microcontact printing to enable quantification of aggrecan deformation and the corresponding nanoscale compressive stress vs. strain curve, the use of tips of differing functionality to provide insights into the molecular mechanisms of deformation, and the comparison of experimental data to the predictions of three increasingly refined Poisson-Boltzmann (P-B)-based theoretical models for the electrostatic double layer component of the interaction.
Collapse
Affiliation(s)
- Delphine Dean
- Department of Electrical Engineering and Computer Science, 77 Massachusetts Avenue, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | | | | |
Collapse
|
88
|
Bathe M, Rutledge GC, Grodzinsky AJ, Tidor B. Osmotic pressure of aqueous chondroitin sulfate solution: a molecular modeling investigation. Biophys J 2005; 89:2357-71. [PMID: 16055525 PMCID: PMC1366736 DOI: 10.1529/biophysj.105.067918] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The osmotic pressure of chondroitin sulfate (CS) solution in contact with an aqueous 1:1 salt reservoir of fixed ionic strength is studied using a recently developed coarse-grained molecular model. The effects of sulfation type (4- vs. 6-sulfation), sulfation pattern (statistical distribution of sulfate groups along a chain), ionic strength, CS intrinsic stiffness, and steric interactions on CS osmotic pressure are investigated. At physiological ionic strength (0.15 M NaCl), the sulfation type and pattern, as measured by a standard statistical description of copolymerization, are found to have a negligible influence on CS osmotic pressure, which depends principally on the mean volumetric fixed charge density. The intrinsic backbone stiffness characteristic of polysaccharides such as CS, however, is demonstrated to contribute significantly to its osmotic pressure behavior, which is similar to that of a solution of charged rods for the 20-disaccharide chains considered. Steric excluded volume is found to play a negligible role in determining CS osmotic pressure at physiological ionic strength due to the dominance of repulsive intermolecular electrostatic interactions that maintain chains maximally spaced in that regime, whereas at high ionic-strength steric interactions become dominant due to electrostatic screening. Osmotic pressure predictions are compared to experimental data and to well-established theoretical models including the Donnan theory and the Poisson-Boltzmann cylindrical cell model.
Collapse
Affiliation(s)
- Mark Bathe
- Department of Mechanical Engineering, the Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | | | | |
Collapse
|