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Gorecki J, Krause S. Numerical investigation of a graphene-on-semiconductor device for optical monitoring of cell electrophysiology. iScience 2024; 27:108554. [PMID: 38188511 PMCID: PMC10770480 DOI: 10.1016/j.isci.2023.108554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 09/19/2023] [Accepted: 11/20/2023] [Indexed: 01/09/2024] Open
Abstract
Spatially resolved sensing devices for electrostatic potentials are extremely useful for characterization of living cells, however, many current techniques lack the speed necessary to capture spatially resolved, functional information of cells in real-time. Here, an optical sensing technique is proposed based on graphene on a semiconductor stack operating in the near-infrared spectrum. By modeling coherent interference of multiply reflected beam paths within the semiconductor stack, we demonstrate how the device produces a continuous reflectivity change in response to graphene Fermi energy which is ideal for sensing changes in local electrostatic fields produced by action potentials of living cells. By coupling the device with a high-speed camera, we propose this platform will allow for high-speed imaging of action potentials over a large sensing area with micron scale resolution.
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Affiliation(s)
- Jon Gorecki
- Department of Bioengineering, Imperial College London, Exhibition Road, London SW7 2BX, UK
| | - Steffi Krause
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK
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2
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Abbruzzetti S, Spyrakis F, Bidon-Chanal A, Luque FJ, Viappiani C. Ligand migration through hemeprotein cavities: insights from laser flash photolysis and molecular dynamics simulations. Phys Chem Chem Phys 2013; 15:10686-701. [PMID: 23733145 DOI: 10.1039/c3cp51149a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The presence of cavities and tunnels in the interior of proteins, in conjunction with the structural plasticity arising from the coupling to the thermal fluctuations of the protein scaffold, has profound consequences on the pathways followed by ligands moving through the protein matrix. In this perspective we discuss how quantitative analysis of experimental rebinding kinetics from laser flash photolysis, trapping of unstable conformational states by embedding proteins within the nanopores of silica gels, and molecular simulations can synergistically converge to gain insight into the migration mechanism of ligands. We show how the evaluation of the free energy landscape for ligand diffusion based on the outcome of computational techniques can assist the definition of sound reaction schemes, leading to a comprehensive understanding of the broad range of chemical events and time scales that encompass the transport of small ligands in hemeproteins.
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Affiliation(s)
- Stefania Abbruzzetti
- Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, viale delle Scienze 7A, 43124, Parma, Italy
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3
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Deep Raman spectroscopy for the non-invasive standoff detection of concealed chemical threat agents. Talanta 2012; 94:342-7. [DOI: 10.1016/j.talanta.2012.03.053] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 03/12/2012] [Accepted: 03/20/2012] [Indexed: 11/20/2022]
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4
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Serrano AL, Waegele MM, Gai F. Spectroscopic studies of protein folding: linear and nonlinear methods. Protein Sci 2012; 21:157-70. [PMID: 22109973 PMCID: PMC3324760 DOI: 10.1002/pro.2006] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 11/15/2011] [Indexed: 01/08/2023]
Abstract
Although protein folding is a simple outcome of the underlying thermodynamics, arriving at a quantitative and predictive understanding of how proteins fold nevertheless poses huge challenges. Therefore, both advanced experimental and computational methods are continuously being developed and refined to probe and reveal the atomistic details of protein folding dynamics and mechanisms. Herein, we provide a concise review of recent developments in spectroscopic studies of protein folding, with a focus on new triggering and probing methods. In particular, we describe several laser-based techniques for triggering protein folding/unfolding on the picosecond and/or nanosecond timescales and various linear and nonlinear spectroscopic techniques for interrogating protein conformations, conformational transitions, and dynamics.
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Affiliation(s)
- Arnaldo L Serrano
- Department of Chemistry, University of PennsylvaniaPhiladelphia, Pennsylvania 19104
| | - Matthias M Waegele
- Department of Chemistry, University of PennsylvaniaPhiladelphia, Pennsylvania 19104
| | - Feng Gai
- Department of Chemistry, University of PennsylvaniaPhiladelphia, Pennsylvania 19104
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5
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Zanetti Polzi L, Daidone I, Anselmi M, Carchini G, Di Nola A, Amadei A. Analysis of Infrared Spectra of β-Hairpin Peptides As Derived from Molecular Dynamics Simulations. J Phys Chem B 2011; 115:11872-8. [DOI: 10.1021/jp202332z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
| | - Isabella Daidone
- Dipartimento di Chimica Ingegneria Chimica e Materiali, University of L′Aquila, Coppito (AQ), Italy
| | | | - Giuliano Carchini
- Dipartimento di Chimica, University of Rome “La Sapienza”, Rome, Italy
| | - Alfredo Di Nola
- Dipartimento di Chimica, University of Rome “La Sapienza”, Rome, Italy
| | - Andrea Amadei
- Dipartimento di Scienze e Tecnologie Chimiche, University of Rome “Tor Vergata”, Rome, Italy
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6
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Ritschdorff ET, Plenert ML, Shear JB. Microsecond analysis of transient molecules using bi-directional capillary electrophoresis. Anal Chem 2009; 81:8790-6. [PMID: 19874052 DOI: 10.1021/ac901283y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We demonstrate the feasibility for minimizing electrophoretic analysis times of transient chemical species by inducing nascent, oppositely charged photochemical products to migrate in opposite directions from their point of creation. In this approach, separate probe sites are positioned within an electrophoretic channel both upfield and downfield from a photoreaction site formed by high-numerical-aperture optics, with positively charged (and in some cases neutral) components migrating toward one probe site and negatively charged species migrating in the opposite direction, toward the second probe site. As a proof-of-concept, fluorescent photoproducts of the hydroxyindoles, 5-hydroxytryptamine (serotonin), 5-hydroxytrptophan, and 5-hydroxyindole-2-carboxylic acid, are formed within a geometrically modified capillary and are transported electrophoretically and electroosmotically to probe sites several micrometers away. Although it is possible to detect all components in a single channel, or to use a two-channel imaging approach to independently detect positive and negative components, we have found the most rapid analysis approach involves a protocol in which laser light is alternately directed to opposing probe sites at high frequency (1 kHz), a strategy that allows positive and negative species to be detected with no cross-talk, even when components have overlapping detection times. Fluorescence-signal-averaging is performed on each temporal channel via summation of the two sequences of interdigitized electrophoretic traces. This approach allows photoproducts to be detected free from interferences from oppositely charged species, enabling positive and negative species in a mixture to be analyzed electrophoretically in ca. 6 micros, a period several-fold faster than was previously feasible using unidirectional electrophoresis.
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Affiliation(s)
- Eric T Ritschdorff
- Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712, USA
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8
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Abbruzzetti S, Bruno S, Faggiano S, Ronda L, Grandi E, Mozzarelli A, Viappiani C. Characterization of ligand migration mechanisms inside hemoglobins from the analysis of geminate rebinding kinetics. Methods Enzymol 2008; 437:329-45. [PMID: 18433636 DOI: 10.1016/s0076-6879(07)37017-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
The presence of internal hydrophobic cavities and packing defects has been demonstrated for several small globular proteins, including hemoglobins. The reduced thermodynamic stability appears to be compensated for by the capability of controlling ligand diffusion through the protein matrix to the active site, possibly by stocking more than one reactant molecule in selected sites. Photolysis of carbon monoxide complexes of hemoglobins encapsulated in silica gels leads to multiphasic geminate rebinding kinetics at room temperature, reflecting rebinding also from different temporary docking sites inside the protein matrix. A careful analysis of the ligand rebinding kinetics allows the determination of the microscopic rates for the underlying reactions, including those governing the migration to and from the docking sites. This chapter describes the experimental approach used to characterize the ligand rebinding kinetics for heme proteins in silica gels after nanosecond laser flash photolysis and the computational methods necessary to retrieve the kinetic parameters.
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9
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Sottini S, Abbruzzetti S, Viappiani C, Ronda L, Mozzarelli A. Determination of microscopic rate constants for CO binding and migration in myoglobin encapsulated in silica gels. J Phys Chem B 2007; 109:19523-8. [PMID: 16853522 DOI: 10.1021/jp054098l] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
CO rebinding kinetics after nanosecond photolysis of myoglobin encapsulated in wet silica gels exhibits an enhanced geminate phase that allows the determination of the microscopic rate constants and the activation barriers for distinct ligand docking sites inside the protein matrix. Using a maximum entropy method, we demonstrate that the geminate phase can be well-described by a biphasic lifetime distribution, reflecting rebinding from the distal and proximal sites. Microscopic rates and activation barriers were estimated using a four-state model.
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Affiliation(s)
- Silvia Sottini
- Dipartimento di Fisica, Università degli Studi di Parma, Parco Area delle Scienze 7/A, Università degli Studi di Parma, Parco Area delle Scienze 23/A, 43100 Parma, Italy
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Amadei A, D’Abramo M, Daidone I, D’Alessandro M, Nola AD, Aschi M. Statistical mechanical modelling of chemical reactions in complex systems: the kinetics of the Haem carbon monoxide binding–unbinding reaction in Myoglobin. Theor Chem Acc 2007. [DOI: 10.1007/s00214-006-0197-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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11
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Yang S, Cho M. Thermal Denaturation of Polyalanine Peptide in Water by Molecular Dynamics Simulations and Theoretical Prediction of Infrared Spectra: Helix−Coil Transition Kinetics. J Phys Chem B 2007; 111:605-17. [PMID: 17228919 DOI: 10.1021/jp0649091] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Perspectives in the helix-coil transition kinetics of secondary structures are examined by temperature-jump molecular dynamics (T-jump MD) simulations and theoretically calculated infrared (IR) spectra. Homopolymeric polyalanine, Ac-(A)(21)-NHMe (A21), is unfolded in water by T-jumps from 273 to 300 K approximately 450 K using AMBER ff99 and ff03 force fields. MD simulation results provide in silico evidence that 3(10)-helix and type I beta-turn motifs are highly probable in both ff99 and ff03 results. Temperature-dependent difference IR spectra of A21 do not possess an isosbestic point in both results, and isotope-labeled difference IR spectra in ff03 results predict characteristic profiles observed in experiments. Unfolding rates obtained from simulated time-resoled IR spectra are in good agreement with those estimated by helical contents, but they are still an order of magnitude smaller than experimental values. We demonstrate that the conventional criteria such as single-exponential fit of transient amide I absorbance, sigmoidal fit of temperature-dependent amide I absorbance, and Arrhenius plot of relaxation rates cannot guarantee the validity of assuming a two-state mechanism. We suggest a way of determining T(m) by the temperature dependence of center frequency and full width at half-maximum of amide I band. Overall, both ff99 and ff03 force fields give consistent results in reproducing key aspects concerned experimentally, but are not predominantly satisfactory in quantitative aspects.
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Affiliation(s)
- Seongeun Yang
- Department of Chemistry and Center for Multidimensional Spectroscopy, Korea University, Seoul 136-701, Korea
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12
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Kolb JS, Thomson MD, Novosel M, Sénéchal-David K, Rivière É, Boillot ML, Roskos HG. Characterization of Fe(II) complexes exhibiting the ligand-driven light-induced spin-change effect using SQUID and magnetic circular dichroism. CR CHIM 2007. [DOI: 10.1016/j.crci.2006.10.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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13
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Abbruzzetti S, Bruno S, Faggiano S, Grandi E, Mozzarelli A, Viappiani C. Time-resolved methods in Biophysics. 2. Monitoring haem proteins at work with nanosecond laser flash photolysis. Photochem Photobiol Sci 2006; 5:1109-20. [PMID: 17136275 DOI: 10.1039/b610236k] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Haem proteins have long been the most studied proteins in biophysics, and have become paradigms for the characterization of fundamental biomolecular processes as ligand binding and regulatory conformational transitions. The presence of the haem prosthetic group, the absorbance spectrum of which has a ligation sensitive region conveniently located in the UV-visible range, has offered a powerful and sensitive tool for the investigation of molecular functions. The central Fe atom is capable of reversibly binding diatomic ligands, including O(2), CO, and NO. The Fe-ligand bond is photolabile, and a reactive unligated state can be transiently generated with a pulsed laser. The photodissociated ligands quickly rebind to the haem and the process can be monitored by transient absorbance methods. The ligand rebinding kinetics reflects protein dynamics and ligand migration within the protein inner cavities. The characterization of these processes was done in the past mainly by low temperature experiments. The use of silica gels to trap proteins allows the characterization of internal ligand dynamics at room temperature. In order to show the potential of the laser flash photolysis techniques, combined with modern numerical analysis methods, we report experiments conducted on two non-symbiotic haemoglobins from Arabidopsis thaliana. The comparison between time courses recorded on haemoglobins in solution and encapsulated in silica gels allows for the highlighting of different interplays between protein dynamics and ligand migration.
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14
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Lednev IK, Ermolenkov VV, Higashiya S, Popova LA, Topilina NI, Welch JT. Reversible thermal denaturation of a 60-kDa genetically engineered beta-sheet polypeptide. Biophys J 2006; 91:3805-18. [PMID: 16891363 PMCID: PMC1630459 DOI: 10.1529/biophysj.106.082792] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A de novo 687-amino-acid residue polypeptide with a regular 32-amino-acid repeat sequence, (GA)(3)GY(GA)(3)GE(GA)(3)GH(GA)(3)GK, forms large beta-sheet assemblages that exhibit remarkable folding properties and, as well, form fibrillar structures. This construct is an excellent tool to explore the details of beta-sheet formation yielding intimate folding information that is otherwise difficult to obtain and may inform folding studies of naturally occurring materials. The polypeptide assumes a fully folded antiparallel beta-sheet/turn structure at room temperature, and yet is completely and reversibly denatured at 125 degrees C, adopting a predominant polyproline II conformation. Deep ultraviolet Raman spectroscopy indicated that melting/refolding occurred without any spectroscopically distinct intermediates, yet the relaxation kinetics depend on the initial polypeptide state, as would be indicative of a non-two-state process. Thermal denaturation and refolding on cooling appeared to be monoexponential with characteristic times of approximately 1 and approximately 60 min, respectively, indicating no detectable formation of hairpin-type nuclei in the millisecond timescale that could be attributed to nonlocal "nonnative" interactions. The polypeptide folding dynamics agree with a general property of beta-sheet proteins, i.e., initial collapse precedes secondary structure formation. The observed folding is much faster than expected for a protein of this size and could be attributed to a less frustrated free-energy landscape funnel for folding. The polypeptide sequence suggests an important balance between the absence of strong nonnative contacts (salt bridges or hydrophobic collapse) and limited repulsion of charged side chains.
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Affiliation(s)
- Igor K Lednev
- Department of Chemistry, University at Albany, State University of New York, Albany, New York, USA.
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15
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Chapter 13 Principal Components Analysis: A Review of its Application on Molecular Dynamics Data. ANNUAL REPORTS IN COMPUTATIONAL CHEMISTRY 2006. [DOI: 10.1016/s1574-1400(06)02013-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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16
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Cordone L, Cottone G, Giuffrida S, Palazzo G, Venturoli G, Viappiani C. Internal dynamics and protein–matrix coupling in trehalose-coated proteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2005; 1749:252-81. [PMID: 15886079 DOI: 10.1016/j.bbapap.2005.03.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Revised: 03/04/2005] [Accepted: 03/04/2005] [Indexed: 11/23/2022]
Abstract
We review recent studies on the role played by non-liquid, water-containing matrices on the dynamics and structure of embedded proteins. Two proteins were studied, in water-trehalose matrices: a water-soluble protein (carboxy derivative of horse heart myoglobin) and a membrane protein (reaction centre from Rhodobacter sphaeroides). Several experimental techniques were used: Mossbauer spectroscopy, elastic neutron scattering, FTIR spectroscopy, CO recombination after flash photolysis in carboxy-myoglobin, kinetic optical absorption spectroscopy following pulsed and continuous photoexcitation in Q(B) containing or Q(B) deprived reaction centre from R. sphaeroides. Experimental results, together with the outcome of molecular dynamics simulations, concurred to give a picture of how water-containing matrices control the internal dynamics of the embedded proteins. This occurs, in particular, via the formation of hydrogen bond networks that anchor the protein surface to the surrounding matrix, whose stiffness increases by lowering the sample water content. In the conclusion section, we also briefly speculate on how the protein-matrix interactions observed in our samples may shed light on the protein-solvent coupling also in liquid aqueous solutions.
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Affiliation(s)
- Lorenzo Cordone
- Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Italy.
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17
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Sottini S, Viappiani C, Ronda L, Bettati S, Mozzarelli A. CO Rebinding Kinetics to Myoglobin- and R-State-Hemoglobin-Doped Silica Gels in the Presence of Glycerol. J Phys Chem B 2004. [DOI: 10.1021/jp049472g] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Silvia Sottini
- Dipartimento di Fisica, Università degli Studi di Parma, Parco Area delle Scienze 7/A, 43100 Parma, Italy; Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, Parco Area delle Scienze 23/A, 43100 Parma, Italy; Dipartimento di Sanità Pubblica, Università degli Studi di Parma, via Volturno 39, 43100 Parma, Italy; and Istituto Nazionale per la Fisica della Materia (INFM), c/o Dipartimento di Fisica, Università di Parma, parco area delle scienze 7A, 43100 Parma, Italy
| | - Cristiano Viappiani
- Dipartimento di Fisica, Università degli Studi di Parma, Parco Area delle Scienze 7/A, 43100 Parma, Italy; Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, Parco Area delle Scienze 23/A, 43100 Parma, Italy; Dipartimento di Sanità Pubblica, Università degli Studi di Parma, via Volturno 39, 43100 Parma, Italy; and Istituto Nazionale per la Fisica della Materia (INFM), c/o Dipartimento di Fisica, Università di Parma, parco area delle scienze 7A, 43100 Parma, Italy
| | - Luca Ronda
- Dipartimento di Fisica, Università degli Studi di Parma, Parco Area delle Scienze 7/A, 43100 Parma, Italy; Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, Parco Area delle Scienze 23/A, 43100 Parma, Italy; Dipartimento di Sanità Pubblica, Università degli Studi di Parma, via Volturno 39, 43100 Parma, Italy; and Istituto Nazionale per la Fisica della Materia (INFM), c/o Dipartimento di Fisica, Università di Parma, parco area delle scienze 7A, 43100 Parma, Italy
| | - Stefano Bettati
- Dipartimento di Fisica, Università degli Studi di Parma, Parco Area delle Scienze 7/A, 43100 Parma, Italy; Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, Parco Area delle Scienze 23/A, 43100 Parma, Italy; Dipartimento di Sanità Pubblica, Università degli Studi di Parma, via Volturno 39, 43100 Parma, Italy; and Istituto Nazionale per la Fisica della Materia (INFM), c/o Dipartimento di Fisica, Università di Parma, parco area delle scienze 7A, 43100 Parma, Italy
| | - Andrea Mozzarelli
- Dipartimento di Fisica, Università degli Studi di Parma, Parco Area delle Scienze 7/A, 43100 Parma, Italy; Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Parma, Parco Area delle Scienze 23/A, 43100 Parma, Italy; Dipartimento di Sanità Pubblica, Università degli Studi di Parma, via Volturno 39, 43100 Parma, Italy; and Istituto Nazionale per la Fisica della Materia (INFM), c/o Dipartimento di Fisica, Università di Parma, parco area delle scienze 7A, 43100 Parma, Italy
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Suydam IT, Boxer SG. Vibrational Stark Effects Calibrate the Sensitivity of Vibrational Probes for Electric Fields in Proteins. Biochemistry 2003; 42:12050-5. [PMID: 14556636 DOI: 10.1021/bi0352926] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Infrared spectroscopy is widely used to probe local environments and dynamics in proteins. The introduction of a unique vibration at a specific site of a protein or more complex assembly offers many advantages over observing the spectra of an unmodified protein. We have previously shown that infrared frequency shifts in proteins can arise from differences in the local electric field at the probe vibration. Thus, vibrational frequencies can be used to map electric fields in proteins at many sites or to measure the change in electric field due to a perturbation. The Stark tuning rate gives the sensitivity of a vibrational frequency to an electric field, and for it to be useful, the Stark tuning rate should be as large as possible. Vibrational Stark effect spectroscopy provides a direct measurement of the Stark tuning rate and allows a quantitative interpretation of frequency shifts. We present vibrational Stark spectra of several bond types, extending our work on nitriles and carbonyls and characterizing four additional bond types (carbon-fluorine, carbon-deuterium, azide, and nitro bonds) that are potential probes for electric fields in proteins. The measured Stark tuning rates, peak positions, and extinction coefficients provide the primary information needed to design amino acid analogues or labels to act as probes of local environments in proteins.
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Affiliation(s)
- Ian T Suydam
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA
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Hirano A, Moridera N, Akashi M, Saito M, Sugawara M. Imaging ofl-Glutamate Fluxes in Mouse Brain Slices Based on an Enzyme-Based Membrane Combined with a Difference-Image Analysis. Anal Chem 2003; 75:3775-83. [PMID: 14572043 DOI: 10.1021/ac030088+] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A time-resolved imaging method for visualizing L-glutamate release in mammalian brain slices is proposed by using an enzyme membrane combined with a difference-image analysis. The enzyme membrane is composed of L-glutamate oxidase and horseradish peroxidase incorporated into a bovine serum albumin matrix. L-Glutamate triggers an enzyme-coupling reaction to convert a redox substrate (DA-64) to Bindschedler's Green, which gives a green color signal. The difference-image analysis is based on calculating slopes of a signal versus time (t) plot in the time range from (t - 40 s) to (t + 40 s) for visualizing L-glutamate release in terms of its flux (in mol min(-1) cm(-2)). The method was applied to a time-resolved imaging of hippocampal distribution of ischemia-induced L-glutamate release in mouse brain slices. The image of L-glutamate distribution showed that the level and time courses of L-glutamate fluxes were neuronal region-dependent. The maximum flux of L-glutamate at CA1 was observed at 7.7 min after ischemia. The flux at 7.7 min increased in the order of CA1 approximately CA3 > DG. The time course of the L-glutamate flux in the CA1 region was biphasic and that in the DG region was modestly biphasic. In the CA3 region, such biphasic release of L-glutamate was not seen. The ischemia-induced L-glutamate flux was accelerated when Mg2+ was omitted from an extracellular solution. The present enzyme membrane-based approach provides a useful method for visualizing distribution of L-glutamate release in the brain slices during ischemia.
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Affiliation(s)
- Ayumi Hirano
- Department of Physics and Applied Physics and Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajousui, Setagaya, Tokyo 156-8550, Japan.
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21
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Enhanced geminate ligand rebinding upon photo-dissociation of silica gel-embedded myoglobin–CO. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)01027-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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23
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Abstract
Weak particle gels have attracted increasing attention in the last decade. These gels have a very short region of deformation over which their viscoelastic parameters are constant. They can be broken easily in response to external forces. Therefore the rheological measurements in these systems must be performed at very small deformations, which may frequently be below the accuracy limits of conventional rheological instruments. In the present paper we discuss the application of the thickness shear mode resonator technique for the measurement of viscoelastic parameters of weak particle gels in the MHz frequency range. The technique provides information on the viscoelasticity of weak gels in the time scale 10(-7)-10(-9) s. The length scale of the measurements, determined by the depth of penetration and the wavelength of the shear wave, falls in the submicron and micron range. The displacements in the shear deformations generated in this technique are extremely small, in the order of Angstroms, and the shear strain, approximately 10(-3), corresponds to the low limits in the classical dynamic rheology measurements. Only small volumes, down to 0.1 ml, of sample are required and this is another advantage of this technique. The measurements of the storage, G', and the loss, G'', moduli can be carried out non-invasively and continuously at various frequencies in the same sample during the whole length of the process of gelation. General and specific aspects of the measurements and interpretation of experimental results are discussed in the present paper.
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Affiliation(s)
- V Buckin
- Department of Chemistry, University College Dublin, Belfield, Ireland.
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24
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Schulze BG, Grubmüller H, Evanseck JD. Functional Significance of Hierarchical Tiers in Carbonmonoxy Myoglobin: Conformational Substates and Transitions Studied by Conformational Flooding Simulations. J Am Chem Soc 2000. [DOI: 10.1021/ja993788y] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Brita G. Schulze
- Contribution from the Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146-0431, and Max-Planck-Institut für Biophysikalische Chemie, Göttingen, Germany
| | - Helmut Grubmüller
- Contribution from the Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146-0431, and Max-Planck-Institut für Biophysikalische Chemie, Göttingen, Germany
| | - Jeffrey D. Evanseck
- Contribution from the Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146-0431, and Max-Planck-Institut für Biophysikalische Chemie, Göttingen, Germany
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25
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Abstract
During protein folding, many of the events leading to secondary and tertiary structure occur in milliseconds or faster. Modern nuclear magnetic resonance and laser detection techniques, coupled with fast initiation of the folding reaction, are probing these events in great detail. Theory, ranging from analytical models to molecular dynamics calculations, is beginning to match up with experiment. As a result, timescales, from such elementary steps as the addition of a residue to a helix to strange kinetics of collapsing protein backbones, can now be measured and interpreted.
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Affiliation(s)
- M Gruebele
- Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana, IL 61801, USA.
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26
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Stange P, Mikhailov AS, Hess B. Mutual Synchronization of Molecular Turnover Cycles in Allosteric Enzymes II. Product Inhibition. J Phys Chem B 1999. [DOI: 10.1021/jp9900640] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- P. Stange
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4−6, D-14195 Berlin, Germany, and Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Str. 11 D-44227 Dortmund, Germany2
| | - A. S. Mikhailov
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4−6, D-14195 Berlin, Germany, and Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Str. 11 D-44227 Dortmund, Germany2
| | - B. Hess
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4−6, D-14195 Berlin, Germany, and Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Str. 11 D-44227 Dortmund, Germany2
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27
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Goldbeck RA, Thomas YG, Chen E, Esquerra RM, Kliger DS. Multiple pathways on a protein-folding energy landscape: kinetic evidence. Proc Natl Acad Sci U S A 1999; 96:2782-7. [PMID: 10077588 PMCID: PMC15846 DOI: 10.1073/pnas.96.6.2782] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The funnel landscape model predicts that protein folding proceeds through multiple kinetic pathways. Experimental evidence is presented for more than one such pathway in the folding dynamics of a globular protein, cytochrome c. After photodissociation of CO from the partially denatured ferrous protein, fast time-resolved CD spectroscopy shows a submillisecond folding process that is complete in approximately 10(-6) s, concomitant with heme binding of a methionine residue. Kinetic modeling of time-resolved magnetic circular dichroism data further provides strong evidence that a 50-microseconds heme-histidine binding process proceeds in parallel with the faster pathway, implying that Met and His binding occur in different conformational ensembles of the protein, i.e., along respective ultrafast (microseconds) and fast (milliseconds) folding pathways. This kinetic heterogeneity appears to be intrinsic to the diffusional nature of early folding dynamics on the energy landscape, as opposed to the late-time heterogeneity associated with nonnative heme ligation and proline isomers in cytochrome c.
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Affiliation(s)
- R A Goldbeck
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
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28
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Callender RH, Dyer RB, Gilmanshin R, Woodruff WH. Fast events in protein folding: the time evolution of primary processes. Annu Rev Phys Chem 1999; 49:173-202. [PMID: 9933907 DOI: 10.1146/annurev.physchem.49.1.173] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Most experimental studies on the dynamics of protein folding have been confined to timescales of 1 ms and longer. Yet it is obvious that many phenomena that are obligatory elements of the folding process occur on much faster timescales. For example, it is also now clear that the formation of secondary and tertiary structures can occur on nanosecond and microsecond times, respectively. Although fast events are essential to, and sometimes dominate, the overall folding process, with a few exceptions their experimental study has become possible only recently with the development of appropriate techniques. This review discusses new approaches that are capable of initiating and monitoring the fast events in protein folding with temporal resolution down to picoseconds. The first important results from those techniques, which have been obtained for the folding of some globular proteins and polypeptide models, are also discussed.
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Affiliation(s)
- R H Callender
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA. ,
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29
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Luo Y, Peyton DH, Yee S. Proton resonance assignments and ligand exchange kinetics in high-spin and mixed-spin myoglobin complexes using two-dimensional exchange spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1388:66-76. [PMID: 9774707 DOI: 10.1016/s0167-4838(98)00161-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The task of assigning resonances in proton nuclear magnetic resonance spectra of paramagnetic heme proteins can be an arduous process, but with the development of multi-dimensional NMR methods the situation has improved. It is demonstrated here that two-dimensional exchange spectroscopic experiments can be used to obtain to assignment correlations for the heme protons of methydroxy-, metthiocyano-, metaquo-, and metimidazole-myoglobin forms. All the assignments are unambiguous and straightforward when the temperature and mixing times are adjusted to minimize nuclear Overhauser cross-peaks from each complex. Moreover, saturation transfer experiments allow the study of ligand binding kinetics. The exchange rates between metaquo- and metimidazole- (or methyl substituted imidazole) myoglobin complexes are estimated. The differences between the exchange rates reflect differences in the hydrophobic and steric interactions between the ligands and the protein moiety.
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Affiliation(s)
- Y Luo
- Department of Chemistry, Portland State University, P.O. Box 751, Portland, OR 97207-0751, USA
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30
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Lyon LA, Keating CD, Fox AP, Baker BE, He L, Nicewarner SR, Mulvaney SP, Natan MJ. Raman spectroscopy. Anal Chem 1998; 70:341R-361R. [PMID: 9640107 DOI: 10.1021/a1980021p] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- L A Lyon
- Department of Chemistry, Pennsylvania State University, University Park 16802, USA
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31
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Abstract
The addition of circular or, more generally, elliptical polarization state detection to fast optical absorption spectroscopy can increase the amount of electronic and nuclear conformational information obtained about transient molecular species. To accomplish this, fast circular dichroism methods have emerged over the past decade that overcome the millisecond limit on time resolution associated with conventional modulation techniques and enable structural studies of excited states and kinetic intermediates. This article reviews techniques for time-resolved natural and magnetic circular dichroism spectroscopy covering the picosecond to millisecond time regimes and their applications, with particular emphasis on quasi-null ellipsometric techniques for nanosecond multichannel measurements of circular dichroism. Closely related quasi-null polarimetric techniques for nanosecond optical rotatory dispersion and linear dichroism measurements are also discussed.
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Affiliation(s)
- R A Goldbeck
- Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064-1077, USA.
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