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Ayyub OB, Sekowski JW, Yang TI, Zhang X, Briber RM, Kofinas P. Color changing block copolymer films for chemical sensing of simple sugars. Biosens Bioelectron 2011; 28:349-54. [DOI: 10.1016/j.bios.2011.07.043] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Revised: 07/15/2011] [Accepted: 07/18/2011] [Indexed: 11/27/2022]
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27
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Zhang X, Metting CJ, Briber RM, Weilnboeck F, Shin SH, Jones BG, Oehrlein GS. Poly(2-vinylnaphthalene)-block-
poly(acrylic acid) Block Copolymer: Self-Assembled Pattern Formation, Alignment, and Transfer into Silicon via Plasma Etching. MACROMOL CHEM PHYS 2011. [DOI: 10.1002/macp.201100232] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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28
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Roh JH, Briber RM, Kilburn D, Behrouzi R, Guo L, Woodson SA. The Role of Electrostatic Relaxation on the Folding Kinetics of a Bacterial Ribozyme. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.1507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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29
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Behrouzi R, Roh JH, Kilburn D, Briber RM, Woodson SA. Tertiary Interactions Maintain the Balance of Stability, Folding Efficiency and Speed in a Large Catalytic Bacterial RNA. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.1505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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30
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Khodadadi S, Roh JH, Kisliuk A, Mamontov E, Tyagi M, Woodson SA, Briber RM, Sokolov AP. Dynamics of biological macromolecules: not a simple slaving by hydration water. Biophys J 2010; 98:1321-6. [PMID: 20371332 DOI: 10.1016/j.bpj.2009.12.4284] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Revised: 11/24/2009] [Accepted: 12/04/2009] [Indexed: 11/29/2022] Open
Abstract
We studied the dynamics of hydrated tRNA using neutron and dielectric spectroscopy techniques. A comparison of our results with earlier data reveals that the dynamics of hydrated tRNA is slower and varies more strongly with temperature than the dynamics of hydrated proteins. At the same time, tRNA appears to have faster dynamics than DNA. We demonstrate that a similar difference appears in the dynamics of hydration water for these biomolecules. The results and analysis contradict the traditional view of slaved dynamics, which assumes that the dynamics of biological macromolecules just follows the dynamics of hydration water. Our results demonstrate that the dynamics of biological macromolecules and their hydration water depends strongly on the chemical and three-dimensional structures of the biomolecules. We conclude that the whole concept of slaving dynamics should be reconsidered, and that the mutual influence of biomolecules and their hydration water must be taken into account.
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Kilburn D, Roh JH, Guo L, Briber RM, Woodson SA. Molecular crowding stabilizes folded RNA structure by the excluded volume effect. J Am Chem Soc 2010; 132:8690-6. [PMID: 20521820 DOI: 10.1021/ja101500g] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Crowder molecules in solution alter the equilibrium between folded and unfolded states of biological macromolecules. It is therefore critical to account for the influence of these other molecules when describing the folding of RNA inside the cell. Small angle X-ray scattering experiments are reported on a 64 kDa bacterial group I ribozyme in the presence of polyethylene-glycol 1000 (PEG-1000), a molecular crowder with an average molecular weight of 1000 Da. In agreement with expected excluded volume effects, PEG favors more compact RNA structures. First, the transition from the unfolded to the folded (more compact) state occurs at lower MgCl(2) concentrations in PEG. Second, the radius of gyration of the unfolded RNA decreases from 76 to 64 A as the PEG concentration increases from 0 to 20% wt/vol. Changes to water and ion activities were measured experimentally, and theoretical models were used to evaluate the excluded volume. We conclude that the dominant influence of the PEG crowder on the folding process is the excluded volume effect.
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Roh JH, Guo L, Kilburn JD, Briber RM, Irving T, Woodson SA. Multistage collapse of a bacterial ribozyme observed by time-resolved small-angle X-ray scattering. J Am Chem Soc 2010; 132:10148-54. [PMID: 20597502 PMCID: PMC2918669 DOI: 10.1021/ja103867p] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ribozymes must fold into compact, native structures to function properly in the cell. The first step in forming the RNA tertiary structure is the neutralization of the phosphate charge by cations, followed by collapse of the unfolded molecules into more compact structures. The specificity of the collapse transition determines the structures of the folding intermediates and the folding time to the native state. However, the forces that enable specific collapse in RNA are not understood. Using time-resolved SAXS, we report that upon addition of 5 mM Mg(2+) to the Azoarcus group I ribozyme up to 80% of chains form compact structures in less than 1 ms. In 1 mM Mg(2+), the collapse transition produces extended structures that slowly approach the folded state, while > or = 1.5 mM Mg(2+) leads to an ensemble of random coils that fold with multistage kinetics. Increased flexibility of molecules in the intermediate ensemble correlates with a Mg(2+)-dependent increase in the fast folding population and a previously unobserved crossover in the collapse kinetics. Partial denaturation of the unfolded RNA with urea also increases the fraction of chains following the fast-folding pathway. These results demonstrate that the preferred collapse mechanism depends on the extent of Mg(2+)-dependent charge neutralization and that non-native interactions within the unfolded ensemble contribute to the heterogeneity of the ribozyme folding pathways at the very earliest stages of tertiary structure formation.
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Kilburn JD, Roh JH, Guo L, Briber RM, Woodson SA. Folding of Bacterial Group I Ribozyme in Crowded Solutions. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.2570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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34
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Roh JH, Guo L, Kilburn D, Behrouzi R, Briber RM, Irving T, Woodson SA. Time-Resolved Multiphase Folding of Bacterial Group I Ribozyme. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.2569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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35
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Roh JH, Briber RM, Damjanovic A, Thirumalai D, Woodson SA, Sokolov AP. Dynamics of tRNA at different levels of hydration. Biophys J 2009; 96:2755-62. [PMID: 19348758 DOI: 10.1016/j.bpj.2008.12.3895] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Revised: 11/11/2008] [Accepted: 12/01/2008] [Indexed: 01/02/2023] Open
Abstract
The influence of hydration on the nanosecond timescale dynamics of tRNA is investigated using neutron scattering spectroscopy. Unlike protein dynamics, the dynamics of tRNA is not affected by methyl group rotation. This allows for a simpler analysis of the influence of hydration on the conformational motions in RNA. We find that hydration affects the dynamics of tRNA significantly more than that of lysozyme. Both the characteristic length scale and the timescale of the conformational motions in tRNA depend strongly on hydration. Even the characteristic temperature of the so-called "dynamical transition" appears to be hydration-dependent in tRNA. The amplitude of the conformational motions in fully hydrated tRNA is almost twice as large as in hydrated lysozyme. We ascribe these differences to a more open and flexible structure of hydrated RNA, and to a larger fraction and different nature of hydrophilic sites. The latter leads to a higher density of water that makes the biomolecule more flexible. All-atom molecular-dynamics simulations are used to show that the extent of hydration is greater in tRNA than in lysozyme. We propose that water acts as a "lubricant" in facilitating enhanced motion in solvated RNA molecules.
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Yun SI, Lai KC, Briber RM, Teertstra SJ, Gauthier M, Bauer BJ. Conformation of Arborescent Polymers in Solution by Small-Angle Neutron Scattering: Segment Density and Core−Shell Morphology. Macromolecules 2007. [DOI: 10.1021/ma7021106] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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37
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Briber RM, Thomas EL. Investigation of two crystal forms in MDI/BDO-based polyurethanes. J MACROMOL SCI B 2006. [DOI: 10.1080/00222348308224773] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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38
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Akcora P, Briber RM, Kofinas P. TEM characterization of diblock copolymer templated iron oxide nanoparticles: Bulk solution and thin film surface doping approach. POLYMER 2006. [DOI: 10.1016/j.polymer.2006.01.064] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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39
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Gao J, Walsh GC, Bigio D, Briber RM, Wetzel MD. Residence-time distribution model for twin-screw extruders. AIChE J 2006. [DOI: 10.1002/aic.690451210] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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40
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Caliskan G, Hyeon C, Perez-Salas U, Briber RM, Woodson SA, Thirumalai D. Persistence length changes dramatically as RNA folds. PHYSICAL REVIEW LETTERS 2005; 95:268303. [PMID: 16486414 DOI: 10.1103/physrevlett.95.268303] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2005] [Indexed: 05/06/2023]
Abstract
We determine the persistence length l(p) for a bacterial group I ribozyme as a function of concentration of monovalent and divalent cations by fitting the distance distribution functions P(r) obtained from small angle x-ray scattering intensity data to the asymptotic form of the calculated P(WLC)(r) for a wormlike chain. The l(p) values change dramatically over a narrow range of Mg(2+) concentration from approximately 21 Angstroms in the unfolded state (U) to approximately 10 Angstroms in the compact (I(C)) and native states. Variations in l(p) with increasing Na(+) concentration are more gradual. In accord with the predictions of polyelectrolyte theory we find l(p) alpha 1/kappa(2) where kappa is the inverse Debye-screening length.
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41
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Caliskan G, Briber RM, Thirumalai D, Garcia-Sakai V, Woodson SA, Sokolov AP. Dynamic Transition in tRNA is Solvent Induced. J Am Chem Soc 2005; 128:32-3. [PMID: 16390107 DOI: 10.1021/ja056444i] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dynamics of tRNA was studied using neutron scattering spectroscopy. Despite vast differences in the architecture and backbone structure of proteins and RNA, hydrated tRNA undergoes the dynamic transition at the same temperature as hydrated lysozyme. The similarity of the dynamic transition in RNA and proteins supports the idea that it is solvent induced. Because tRNA essentially has no methyl groups, the results also suggest that methyl groups are not the main contributor of the dynamic transition in biological macromolecules. However, they may explain strong differences in the dynamics of tRNA and lysozyme observed at low temperatures.
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Chauhan S, Caliskan G, Briber RM, Perez-Salas U, Rangan P, Thirumalai D, Woodson SA. RNA tertiary interactions mediate native collapse of a bacterial group I ribozyme. J Mol Biol 2005; 353:1199-209. [PMID: 16214167 DOI: 10.1016/j.jmb.2005.09.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2005] [Revised: 08/31/2005] [Accepted: 09/09/2005] [Indexed: 10/25/2022]
Abstract
Large RNAs collapse into compact intermediates in the presence of counterions before folding to the native state. We previously found that collapse of a bacterial group I ribozyme correlates with the formation of helices within the ribozyme core, but occurs at Mg2+ concentrations too low to support stable tertiary structure and catalytic activity. Here, using small-angle X-ray scattering, we show that Mg2+-induced collapse is a cooperative folding transition that can be fit by a two-state model. The Mg2+ dependence of collapse is similar to the Mg2+ dependence of helix assembly measured by partial ribonuclease T1 digestion and of an unfolding transition measured by UV hypochromicity. The correspondence between multiple probes of RNA structure further supports a two-state model. A mutation that disrupts tertiary contacts between the L9 tetraloop and its helical receptor destabilized the compact state by 0.8 kcal/mol, while mutations in the central triplex were less destabilizing. These results show that native tertiary interactions stabilize the compact folding intermediates under conditions in which the RNA backbone remains accessible to solvent.
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43
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Jones RL, Indrakanti A, Briber RM, Müller M, Kumar SK. Phase Behavior of Ultrathin Polymer Mixtures. Macromolecules 2004. [DOI: 10.1021/ma049108f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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44
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Perez-Salas UA, Rangan P, Krueger S, Briber RM, Thirumalai D, Woodson SA. Compaction of a bacterial group I ribozyme coincides with the assembly of core helices. Biochemistry 2004; 43:1746-53. [PMID: 14769052 DOI: 10.1021/bi035642o] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Counterions are critical to the self-assembly of RNA tertiary structure because they neutralize the large electrostatic forces which oppose the folding process. Changes in the size and shape of the Azoarcus group I ribozyme as a function of Mg(2+) and Na(+) concentration were followed by small angle neutron scattering. In low salt buffer, the RNA was expanded, with an average radius of gyration (R(g)) of 53 +/- 1 A. A highly cooperative transition to a compact form (R(g) = 31.5 +/- 0.5 A) was observed between 1.6 and 1.7 mM MgCl(2). The collapse transition, which is unusually sharp in Mg(2+), has the characteristics of a first-order phase transition. Partial digestion with ribonuclease T1 under identical conditions showed that this transition correlated with the assembly of double helices in the ribozyme core. Fivefold higher Mg(2+) concentrations were required for self-splicing, indicating that compaction occurs before native tertiary interactions are fully stabilized. No further decrease in R(g) was observed between 1.7 and 20 mM MgCl(2), indicating that the intermediates have the same dimensions as the native ribozyme, within the uncertainty of the data (+/-1 A). A more gradual transition to a final R(g) of approximately 33.5 A was observed between 0.45 and 2 M NaCl. This confirms the expectation that monovalent ions not only are less efficient in charge neutralization but also contract the RNA less efficiently than multivalent ions.
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45
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Gao J, Walsh GC, Bigio D, Briber RM, Wetzel MD. Mean residence time analysis for twin screw extruders. POLYM ENG SCI 2004. [DOI: 10.1002/pen.11155] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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46
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McDermott MK, Schroeder LW, Balsis SL, Paradiso NA, Byrne ML, Briber RM. Mechanical properties of polyurethane film exposed to solutions of nonoxynol-9 surfactant and poly(ethylene glycol). J Appl Polym Sci 2003. [DOI: 10.1002/app.13285] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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47
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Nieh MP, Sanat K. Kumar*, Ho DL, Briber RM. Neutron Scattering Study of Chain Conformations in the Energetically Neutral Pores of Vycor Glass. Macromolecules 2002. [DOI: 10.1021/ma012046y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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48
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VanderHart DL, Campbell GC, Briber RM. Phase separation behavior in blends of poly(benzimidazole) and poly(ether imide). Macromolecules 2002. [DOI: 10.1021/ma00044a040] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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49
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50
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Bauer BJ, Briber RM, Han CC. Small-angle neutron scattering studies of compatible blends of linear poly(vinyl methyl ether) and cross-linked deuterated polystyrene. Macromolecules 2002. [DOI: 10.1021/ma00192a068] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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