1
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Barron LD. 'A careful disorderliness' in biomolecular structure revealed by Raman optical activity. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 300:122959. [PMID: 37269652 DOI: 10.1016/j.saa.2023.122959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 05/29/2023] [Indexed: 06/05/2023]
Abstract
Following its first observation 50 years ago Raman optical activity (ROA), which refers to a circular polarization dependence of Raman scattering from chiral molecules, has evolved into a powerful chiroptical spectroscopy for studying a large range of biomolecules in aqueous solution. Among other things ROA provides information about motif and fold as well as secondary structure of proteins; structure of carbohydrates and nucleic acids; polypeptide and carbohydrate structure of intact glycoproteins; and protein and nucleic acid structure of intact viruses. Quantum chemical simulations of observed Raman optical activity spectra can provide complete three-dimensional structures of biomolecules, together with information about conformational dynamics. This article reviews how ROA has provided new insight into the structure of unfolded/disordered states and sequences, ranging from the complete disorder of the random coil to the more controlled type of disorder exemplified by poly L-proline II helix in proteins, high mannose glycan chains in glycoproteins and constrained dynamic states of nucleic acids. Possible roles for this 'careful disorderliness' in biomolecular function, misfunction and disease are discussed, especially amyloid fibril formation.
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Affiliation(s)
- Laurence D Barron
- Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK.
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2
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Quiñones-Ruiz T, Rosario-Alomar MF, Shanmugasundaram M, Ali MM, Lednev IK. Spontaneous Refolding of Amyloid Fibrils from One Polymorph to Another Caused by Changes in Environmental Hydrophobicity. Biochemistry 2022; 61:1456-1464. [PMID: 35786852 DOI: 10.1021/acs.biochem.2c00143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Here, we report a new phenomenon in which lysozyme fibrils formed in a solution of acetic acid spontaneously refold to a different polymorph through a disassembled intermediate upon the removal of acetic acid. The structural changes were revealed and characterized by deep-UV resonance Raman spectroscopy, nonresonance Raman spectroscopy, intrinsic tryptophan fluorescence spectroscopy, and atomic force microscopy. A PPII-like structure with highly solvent-exposed tryptophan residues predominates the intermediate aggregates before refolding to polymorph II fibrils. Furthermore, the disulfide (SS) bonds undergo significant rearrangements upon the removal of acetic acid from the lysozyme fibril environment. The main SS bond conformation changes from gauche-gauche-trans in polymorph I to gauche-gauche-gauche in polymorph II. Changing the hydrophobicity of the fibril environment was concluded to be the decisive factor causing the spontaneous refolding of lysozyme fibrils from one polymorph to another upon the removal of acetic acid. Potential biological implications of the discovered phenomenon are discussed.
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Affiliation(s)
- Tatiana Quiñones-Ruiz
- Department of Chemistry, University at Albany, SUNY, Albany, New York 12222, United States
| | | | | | - Muhammad M Ali
- Department of Chemistry, University at Albany, SUNY, Albany, New York 12222, United States
| | - Igor K Lednev
- Department of Chemistry, University at Albany, SUNY, Albany, New York 12222, United States
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3
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Yamamoto S, Kimura F. Probing the solvation of the α-helix with extended amide III bands in Raman optical activity. Phys Chem Chem Phys 2022; 24:3191-3199. [PMID: 35043805 DOI: 10.1039/d1cp04480j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Experimental and theoretical Raman optical activity (ROA) study of α-helical peptides and proteins has suggested that the relative intensity of two extended amide III ROA bands at ∼1340 cm-1 (I band) and ∼1300 cm-1 (II band) can be used to monitor the permittivity of the surrounding medium of the α-helix. So far, the ROA intensity ratio, II/III, has been interpreted from two different viewpoints. The first one is in terms of a direct effect of permittivity around the α-helix. The second one is based on a structural equilibrium of two types of α-helical structures, "hydrated" and "unhydrated" ones. In the present study, temperature- and solvent-dependences of II/III are measured for highly-α-helical peptides and compared to the theoretical spectra while varying the permittivity or the type of α-helical structure. A fragment method with partial optimization in the normal modes is adopted in density functional theory calculations. The main features of the experimental spectra and a trend of the observed II/III are well reproduced by the simulations, which leads us to a conclusion that the II/III is dominantly governed by a direct influence of the permittivity of the environment and just accessorily by the equilibrium of the two types of α-helices. The simulations also opposed the conventional assignments of the I and II bands to "hydrated" and "unhydrated" α-helical structures, respectively. In the case of α-helical proteins, solvent exposure of the α-helix may be monitored by the ROA ratio.
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Affiliation(s)
- Shigeki Yamamoto
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka 560-0043, Japan.
| | - Fumiya Kimura
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka 560-0043, Japan.
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4
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Bogaerts J, Aerts R, Vermeyen T, Johannessen C, Herrebout W, Batista JM. Tackling Stereochemistry in Drug Molecules with Vibrational Optical Activity. Pharmaceuticals (Basel) 2021; 14:877. [PMID: 34577577 PMCID: PMC8468215 DOI: 10.3390/ph14090877] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 08/25/2021] [Accepted: 08/26/2021] [Indexed: 12/29/2022] Open
Abstract
Chirality plays a crucial role in drug discovery and development. As a result, a significant number of commercially available drugs are structurally dissymmetric and enantiomerically pure. The determination of the exact 3D structure of drug candidates is, consequently, of paramount importance for the pharmaceutical industry in different stages of the discovery pipeline. Traditionally the assignment of the absolute configuration of druggable molecules has been carried out by means of X-ray crystallography. Nevertheless, not all molecules are suitable for single-crystal growing. Additionally, valuable information about the conformational dynamics of drug candidates is lost in the solid state. As an alternative, vibrational optical activity (VOA) methods have emerged as powerful tools to assess the stereochemistry of drug molecules directly in solution. These methods include vibrational circular dichroism (VCD) and Raman optical activity (ROA). Despite their potential, VCD and ROA are still unheard of to many organic and medicinal chemists. Therefore, the present review aims at highlighting the recent use of VOA methods for the assignment of the absolute configuration of chiral small-molecule drugs, as well as for the structural analysis of biologics of pharmaceutical interest. A brief introduction on VCD and ROA theory and the best experimental practices for using these methods will be provided along with selected representative examples over the last five years. As VCD and ROA are commonly used in combination with quantum calculations, some guidelines will also be presented for the reliable simulation of chiroptical spectra. Special attention will be paid to the complementarity of VCD and ROA to unambiguously assess the stereochemical properties of pharmaceuticals.
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Affiliation(s)
- Jonathan Bogaerts
- Department of Chemistry, University of Antwerp, 2020 Antwerp, Belgium; (J.B.); (R.A.); (T.V.); (C.J.); (W.H.)
| | - Roy Aerts
- Department of Chemistry, University of Antwerp, 2020 Antwerp, Belgium; (J.B.); (R.A.); (T.V.); (C.J.); (W.H.)
| | - Tom Vermeyen
- Department of Chemistry, University of Antwerp, 2020 Antwerp, Belgium; (J.B.); (R.A.); (T.V.); (C.J.); (W.H.)
- Department of Chemistry, Ghent University, 9000 Ghent, Belgium
| | - Christian Johannessen
- Department of Chemistry, University of Antwerp, 2020 Antwerp, Belgium; (J.B.); (R.A.); (T.V.); (C.J.); (W.H.)
| | - Wouter Herrebout
- Department of Chemistry, University of Antwerp, 2020 Antwerp, Belgium; (J.B.); (R.A.); (T.V.); (C.J.); (W.H.)
| | - Joao M. Batista
- Institute of Science and Technology, Federal University of Sao Paulo, Sao Jose dos Campos 12231-280, SP, Brazil
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5
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Haldavnekar R, Venkatakrishnan K, Tan DB. Boosting the sub-cellular biomolecular cancer signals by self-functionalized tag-free nano sensor. Biosens Bioelectron 2021; 190:113407. [PMID: 34134072 DOI: 10.1016/j.bios.2021.113407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 05/19/2021] [Accepted: 06/01/2021] [Indexed: 02/07/2023]
Abstract
Surface Enhanced Raman Scattering (SERS)-based sub-cellular cancer diagnosis can simultaneously obtain multiple biomolecular signals crucial in diagnostic platform for a heterogeneous disease like cancer. But, SERS-probes being typically tagged with chemical functionalization demonstrate limitations due to adverse biocompatibility, ineffective cellular internalization, SERS-signal quenching and spectral contamination. Although, tag-free SERS-probes overcome these limitations; complexity in spectral interpretation and detection insensitivity make it disadvantageous. In this study, we have exploited the inherent charges of cellular biomolecules and introduced self-functionalized complementary charged, tag-free SERS nano probes for biomolecule-specific investigation. Extremely small nano probes (sub 10 nm), synthesized with multiphoton ionization were functionalized with charge by physical synthesis without any ligands or chemical processes. The probes demonstrated significant SERS (EF~106) with analyte molecules (4ATP & 4MBA). Multifold signal boost was achieved for the signals of cellular components - amplification of ~7 fold for DNA, ~16 fold for proteins and ~24 fold for lipids with the commentary charged nano probes as compared to the neutral nano probes. The signal boost was attributed to the efficient delivery of extremely small, complementary charged probes to the cellular biomolecules of interest enabling simultaneous detection of sub-cellular biomolecules such as DNA, proteins and lipids and with high reproducibility. Cancer classification and investigation of drug resistance in cancer with single cell sensitivity was demonstrated. Such biomolecule-specific investigation of cancer from intact cells will open pathways for comprehensive cancer diagnosis.
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Affiliation(s)
- Rupa Haldavnekar
- Institute for Biomedical Engineering, Science and Technology (iBEST), Toronto, Canada; Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada; Nanocharacterization Laboratory, Department of Aerospace Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada; Department of Biomedical Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada
| | - Krishnan Venkatakrishnan
- Keenan Research Center for Biomedical Science, St. Michael's Hospital, 30 Bond Street, Toronto, ON, M5B 1W8, Canada; Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada; Nanocharacterization Laboratory, Department of Aerospace Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada; Department of Biomedical Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada.
| | - Dr Bo Tan
- Keenan Research Center for Biomedical Science, St. Michael's Hospital, 30 Bond Street, Toronto, ON, M5B 1W8, Canada; Department of Biomedical Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada
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6
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Keiderling TA. Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques. Chem Rev 2020; 120:3381-3419. [DOI: 10.1021/acs.chemrev.9b00636] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Timothy A. Keiderling
- Department of Chemistry, University of Illinois at Chicago 845 West Taylor Street m/c 111, Chicago, Illinois 60607-7061, United States
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7
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Hope M, Šebestík J, Kapitán J, Bouř P. Understanding CH-Stretching Raman Optical Activity in Ala–Ala Dipeptides. J Phys Chem A 2020; 124:674-683. [DOI: 10.1021/acs.jpca.9b10557] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marius Hope
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí 2, 16610 Prague, Czech Republic
- Norwegian University of Science and Technology NO-7491 Trondheim, Norway
| | - Jaroslav Šebestík
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí 2, 16610 Prague, Czech Republic
| | - Josef Kapitán
- Department of Optics, Palacký University, 17. listopadu 12, 77146 Olomouc, Czech Republic
| | - Petr Bouř
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí 2, 16610 Prague, Czech Republic
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8
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Tan J, Zhang J, Luo Y, Ye S. Misfolding of a Human Islet Amyloid Polypeptide at the Lipid Membrane Populates through β-Sheet Conformers without Involving α-Helical Intermediates. J Am Chem Soc 2019; 141:1941-1948. [PMID: 30621387 DOI: 10.1021/jacs.8b08537] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Amyloid formation has been implicated in many fatal diseases, but its mechanism remains to be clarified due to a lack of effective methods that can capture the transient intermediates. Here, we experimentally demonstrate that sum frequency generation vibrational spectroscopy can unambiguously discriminate the intermediates during amyloid formation at the lipid membrane in situ and in real time by combining the chiral amide I and achiral amide II and amide III spectral signals of the protein backbone. Such a combination can directly identify the formation of β-hairpin-like monomers and β-sheet oligomers and fibrils. A strong correlation between the amide II signals and the formation of β-sheet oligomers and fibrils was found. With this approach, the structural evolution of human islet amyloid polypeptides (hIAPP) at negative lipid bilayers was elucidated. It was firmly confirmed that hIAPP populates through β-sheet conformers without involving α-helical intermediates. The membrane-associated assembly of hIAPP proceeds by assembling with a β-hairpin-like monomer at the lipid bilayer surface, rather than by inserting the preassembled β-sheet oligomers in solution. This newly established protocol is ready to be utilized in revealing the mechanism of amyloid aggregation at the lipid membrane.
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Affiliation(s)
- Junjun Tan
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, and Synergetic Innovation Center of Quantum Information & Quantum Physics , University of Science and Technology of China , Hefei , 230026 , China
| | - Jiahui Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, and Synergetic Innovation Center of Quantum Information & Quantum Physics , University of Science and Technology of China , Hefei , 230026 , China
| | - Yi Luo
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, and Synergetic Innovation Center of Quantum Information & Quantum Physics , University of Science and Technology of China , Hefei , 230026 , China
| | - Shuji Ye
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, and Synergetic Innovation Center of Quantum Information & Quantum Physics , University of Science and Technology of China , Hefei , 230026 , China
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9
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Abstract
The cellular prion protein, PrPC, is a small, cell surface glycoprotein with a function that is currently somewhat ill defined. It is also the key molecule involved in the family of neurodegenerative disorders called transmissible spongiform encephalopathies, which are also known as prion diseases. The misfolding of PrPC to a conformationally altered isoform, designated PrPTSE, is the main molecular process involved in pathogenesis and appears to precede many other pathologic and clinical manifestations of disease, including neuronal loss, astrogliosis, and cognitive loss. PrPTSE is also believed to be the major component of the infectious "prion," the agent responsible for disease transmission, and preparations of this protein can cause prion disease when inoculated into a naïve host. Thus, understanding the biochemical and biophysical properties of both PrPC and PrPTSE, and ultimately the mechanisms of their interconversion, is critical if we are to understand prion disease biology. Although entire books could be devoted to research pertaining to the protein, herein we briefly review the state of knowledge of prion biochemistry, including consideration of prion protein structure, function, misfolding, and dysfunction.
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Affiliation(s)
- Andrew C Gill
- School of Chemistry, Joseph Banks Laboratories, University of Lincoln, Lincoln, United Kingdom; Division of Neurobiology, The Roslin Institute and Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Edinburgh, United Kingdom.
| | - Andrew R Castle
- Division of Neurobiology, The Roslin Institute and Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Edinburgh, United Kingdom
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10
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Martial B, Lefèvre T, Auger M. Understanding amyloid fibril formation using protein fragments: structural investigations via vibrational spectroscopy and solid-state NMR. Biophys Rev 2018; 10:1133-1149. [PMID: 29855812 PMCID: PMC6082320 DOI: 10.1007/s12551-018-0427-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 05/17/2018] [Indexed: 12/11/2022] Open
Abstract
It is well established that amyloid proteins play a primary role in neurodegenerative diseases. Alzheimer's, Parkinson's, type II diabetes, and Creutzfeldt-Jakob's diseases are part of a wider family encompassing more than 50 human pathologies related to aggregation of proteins. Although this field of research is thoroughly investigated, several aspects of fibrillization remain misunderstood, which in turn slows down, or even impedes, advances in treating and curing amyloidoses. To solve this problem, several research groups have chosen to focus on short fragments of amyloid proteins, sequences that have been found to be of great importance for the amyloid formation process. Studying short peptides allows bypassing the complexity of working with full-length proteins and may provide important information relative to critical segments of amyloid proteins. To this end, efficient biophysical tools are required. In this review, we focus on two essential types of spectroscopic techniques, i.e., vibrational spectroscopy and its derivatives (conventional Raman scattering, deep-UV resonance Raman (DUVRR), Raman optical activity (ROA), surface-enhanced Raman spectroscopy (SERS), tip-enhanced Raman spectroscopy (TERS), infrared (IR) absorption spectroscopy, vibrational circular dichroism (VCD)) and solid-state nuclear magnetic resonance (ssNMR). These techniques revealed powerful to provide a better atomic and molecular comprehension of the amyloidogenic process and fibril structure. This review aims at underlining the information that these techniques can provide and at highlighting their strengths and weaknesses when studying amyloid fragments. Meaningful examples from the literature are provided for each technique, and their complementarity is stressed for the kinetic and structural characterization of amyloid fibril formation.
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Affiliation(s)
- Benjamin Martial
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, l'ingénierie et les applications des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Centre québécois sur les matériaux fonctionnels (CQMF), Université Laval, Québec, QC, G1V 0A6, Canada
| | - Thierry Lefèvre
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, l'ingénierie et les applications des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Centre québécois sur les matériaux fonctionnels (CQMF), Université Laval, Québec, QC, G1V 0A6, Canada
| | - Michèle Auger
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, l'ingénierie et les applications des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Centre québécois sur les matériaux fonctionnels (CQMF), Université Laval, Québec, QC, G1V 0A6, Canada.
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11
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The PPII-to-α-helix transition of poly- l -lysine in methanol/water solvent mixtures accompanied by fibrillar self-aggregation: An influence of fluphenazine molecules. Biophys Chem 2017; 227:14-20. [DOI: 10.1016/j.bpc.2017.05.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 05/23/2017] [Accepted: 05/23/2017] [Indexed: 11/19/2022]
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12
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Castle AR, Gill AC. Physiological Functions of the Cellular Prion Protein. Front Mol Biosci 2017; 4:19. [PMID: 28428956 PMCID: PMC5382174 DOI: 10.3389/fmolb.2017.00019] [Citation(s) in RCA: 128] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 03/22/2017] [Indexed: 01/09/2023] Open
Abstract
The prion protein, PrPC, is a small, cell-surface glycoprotein notable primarily for its critical role in pathogenesis of the neurodegenerative disorders known as prion diseases. A hallmark of prion diseases is the conversion of PrPC into an abnormally folded isoform, which provides a template for further pathogenic conversion of PrPC, allowing disease to spread from cell to cell and, in some circumstances, to transfer to a new host. In addition to the putative neurotoxicity caused by the misfolded form(s), loss of normal PrPC function could be an integral part of the neurodegenerative processes and, consequently, significant research efforts have been directed toward determining the physiological functions of PrPC. In this review, we first summarise important aspects of the biochemistry of PrPC before moving on to address the current understanding of the various proposed functions of the protein, including details of the underlying molecular mechanisms potentially involved in these functions. Over years of study, PrPC has been associated with a wide array of different cellular processes and many interacting partners have been suggested. However, recent studies have cast doubt on the previously well-established links between PrPC and processes such as stress-protection, copper homeostasis and neuronal excitability. Instead, the functions best-supported by the current literature include regulation of myelin maintenance and of processes linked to cellular differentiation, including proliferation, adhesion, and control of cell morphology. Intriguing connections have also been made between PrPC and the modulation of circadian rhythm, glucose homeostasis, immune function and cellular iron uptake, all of which warrant further investigation.
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Adzhubei AA, Anashkina AA, Makarov AA. Left-handed polyproline-II helix revisited: proteins causing proteopathies. J Biomol Struct Dyn 2016; 35:2701-2713. [PMID: 27562438 DOI: 10.1080/07391102.2016.1229220] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Left-handed polyproline-II type helix is a regular conformation of polypeptide chain not only of fibrous, but also of folded and natively unfolded proteins and peptides. It is the only class of regular secondary structure substantially represented in non-fibrous proteins and peptides on a par with right-handed alpha-helix and beta-structure. In this study, we have shown that polyproline-II helix is abundant in several peptides and proteins involved in proteopathies, the amyloid-beta peptides, protein tau and prion protein. Polyproline-II helices form two interaction sites in the amyloid-beta peptides, which are pivotal for pathogenesis of Alzheimer's disease (AD). It also with high probability is the structure of the majority of tau phosphorylation sites, important for tau hyperphosphorylation and formation of neurofibrillary tangles, a hallmark of AD. Polyproline-II helices form large parts of the structure of the folded domain of prion protein. They can undergo conversion to beta-structure as a result of relatively small change of one torsional angle of polypeptide chain. We hypothesize that in prions and amyloids, in general polyproline-II helices can serve as structural elements of the normal structure as well as dormant nuclei of structure conversion, and thus play important role in structure changes leading to the formation of fibrils.
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Affiliation(s)
- Alexei A Adzhubei
- a Engelhardt Institute of Molecular Biology, Russian Academy of Sciences , Vavilov St 32, Moscow 119991 , Russia
| | - Anastasia A Anashkina
- a Engelhardt Institute of Molecular Biology, Russian Academy of Sciences , Vavilov St 32, Moscow 119991 , Russia
| | - Alexander A Makarov
- a Engelhardt Institute of Molecular Biology, Russian Academy of Sciences , Vavilov St 32, Moscow 119991 , Russia
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14
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Kumar P, Bansal M. Structural and functional analyses of PolyProline-II helices in globular proteins. J Struct Biol 2016; 196:414-425. [PMID: 27637571 DOI: 10.1016/j.jsb.2016.09.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/01/2016] [Accepted: 09/12/2016] [Indexed: 11/18/2022]
Abstract
PolyProline-II (PPII) helices are defined as a continuous stretch of a protein chain in which the constituent residues have backbone torsion angle (φ, ψ) values of (-75°, 145°) and take up an extended left handed helical conformation, without any intra-chain hydrogen bonds. They are found to occur quite frequently in protein structures, with their number exceeding that of π-helices, though it is considerably less than that of α-helices and β-strands. A relatively new procedure, ASSP, for the identification of regular secondary structures using Cα trace identifies 3597 PPII-helices in 3582 protein chains, solved at resolution ⩽2.0Å. Taking advantage of this significantly expanded database of PPII-helices, we have analyzed their structural and functional roles as well as determined the amino acid propensity within and around them. Though Pro residues are highly preferred, their presence is not a mandatory requirement for the formation of PPII-helices, since ∼40% PPII-helices were found to contain no Pro residues. Aromatic amino acids are avoided within this helix, while Gly, Asn and Asp residues are preferred in the proximal flanking regions. The PPII-helices range from 3 to 13 residues in length with the average twist and rise being -121.2°±9.2° and 3.0ű0.1Å respectively. A majority (∼72%) of PPII-helices were found to occur in conjunction with α-helices and β-strands, and serve as linkers as well. The analysis of various intra-helical non-bonded interactions revealed frequent presence of CH⋯O H-bonds. PPII-helices participate in maintaining the three-dimensional structure of proteins and are important constituents of binding motifs involved in various biological functions.
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Affiliation(s)
- Prasun Kumar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Manju Bansal
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
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15
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Rouget R, Sharma G, LeBlanc AC. Cyclin-dependent kinase 5 phosphorylation of familial prion protein mutants exacerbates conversion into amyloid structure. J Biol Chem 2015; 290:5759-71. [PMID: 25572400 DOI: 10.1074/jbc.m114.630699] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Familial prion protein (PrP) mutants undergo conversion from soluble and protease-sensitive to insoluble and partially protease-resistant proteins. Cyclin-dependent kinase 5 (Cdk5) phosphorylation of wild type PrP (pPrP) at serine 43 induces a conversion of PrP into aggregates and fibrils. Here, we investigated whether familial PrP mutants are predisposed to Cdk5 phosphorylation and whether phosphorylation of familial PrP mutants increases conversion. PrP mutants representing three major familial PrP diseases and different PrP structural domains were studied. We developed a novel in vitro kinase reaction coupled with Thioflavin T binding to amyloid structure assay to monitor phosphorylation-dependent amyloid conversion. Although non-phosphorylated full-length wild type or PrP mutants did not convert into amyloid, Cdk5 phosphorylation rapidly converted these into Thioflavin T-positive structures following first order kinetics. Dephosphorylation partially reversed conversion. Phosphorylation-dependent conversion of PrP from α-helical structures into β-sheet structures was confirmed by circular dichroism. Relative to wild type pPrP, most PrP mutants showed increased rate constants of conversion. In contrast, non-phosphorylated truncated PrP Y145X (where X represents a stop codon) and Q160X mutants converted spontaneously into Thioflavin T-positive fibrils after a lag phase of over 20 h, indicating nucleation-dependent polymerization. Phosphorylation reduced the lag phase by over 50% and thus accelerated the formation of the nucleating event. Consistently, phosphorylated Y145X and phosphorylated Q160X exacerbated conversion in a homologous seeding reaction, whereas WT pPrP could not seed WT PrP. These results demonstrate an influence of both the N terminus and the C terminus of PrP on conversion. We conclude that post-translational modifications of the flexible N terminus of PrP can cause or exacerbate PrP mutant conversion.
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Affiliation(s)
- Raphaël Rouget
- From the Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3T 1E2, Canada and
| | - Gyanesh Sharma
- From the Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3T 1E2, Canada and Department of Neurology and Neurosurgery, McGill University, 3775 University Street, Montréal, Québec H3A 2B4, Canada
| | - Andréa C LeBlanc
- From the Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3T 1E2, Canada and Department of Neurology and Neurosurgery, McGill University, 3775 University Street, Montréal, Québec H3A 2B4, Canada
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16
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Parchaňský V, Kapitán J, Bouř P. Inspecting chiral molecules by Raman optical activity spectroscopy. RSC Adv 2014. [DOI: 10.1039/c4ra10416a] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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17
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Toal S, Schweitzer-Stenner R. Local order in the unfolded state: conformational biases and nearest neighbor interactions. Biomolecules 2014; 4:725-73. [PMID: 25062017 PMCID: PMC4192670 DOI: 10.3390/biom4030725] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 06/17/2014] [Accepted: 06/20/2014] [Indexed: 12/23/2022] Open
Abstract
The discovery of Intrinsically Disordered Proteins, which contain significant levels of disorder yet perform complex biologically functions, as well as unwanted aggregation, has motivated numerous experimental and theoretical studies aimed at describing residue-level conformational ensembles. Multiple lines of evidence gathered over the last 15 years strongly suggest that amino acids residues display unique and restricted conformational preferences in the unfolded state of peptides and proteins, contrary to one of the basic assumptions of the canonical random coil model. To fully understand residue level order/disorder, however, one has to gain a quantitative, experimentally based picture of conformational distributions and to determine the physical basis underlying residue-level conformational biases. Here, we review the experimental, computational and bioinformatic evidence for conformational preferences of amino acid residues in (mostly short) peptides that can be utilized as suitable model systems for unfolded states of peptides and proteins. In this context particular attention is paid to the alleged high polyproline II preference of alanine. We discuss how these conformational propensities may be modulated by peptide solvent interactions and so called nearest-neighbor interactions. The relevance of conformational propensities for the protein folding problem and the understanding of IDPs is briefly discussed.
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Affiliation(s)
- Siobhan Toal
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19026, USA.
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18
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Yamamoto S, Furukawa T, Bouř P, Ozaki Y. Solvated States of Poly-l-alanine α-Helix Explored by Raman Optical Activity. J Phys Chem A 2014; 118:3655-62. [DOI: 10.1021/jp500794s] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shigeki Yamamoto
- Department
of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Tatsuya Furukawa
- Department
of Chemistry, School of Science and Technology, Kwansei Gakuin University, Gakuen 2-1, Sanda, Hyogo 669-1337, Japan
| | - Petr Bouř
- Institute
of Organic Chemistry and Biochemistry, Academy of Sciences, 166 10 Prague, Czech Republic
| | - Yukihiro Ozaki
- Department
of Chemistry, School of Science and Technology, Kwansei Gakuin University, Gakuen 2-1, Sanda, Hyogo 669-1337, Japan
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19
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Dzwolak W. Chirality and Chiroptical Properties of Amyloid Fibrils. Chirality 2014; 26:580-7. [DOI: 10.1002/chir.22335] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 03/28/2014] [Indexed: 01/23/2023]
Affiliation(s)
- Wojciech Dzwolak
- Biological and Chemical Research Centre, Department of Chemistry; University of Warsaw; Warsaw Poland
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20
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Zurawel AA, Walsh DJ, Fortier SM, Chidawanyika T, Sengupta S, Zilm K, Supattapone S. Prion nucleation site unmasked by transient interaction with phospholipid cofactor. Biochemistry 2014; 53:68-76. [PMID: 24328062 DOI: 10.1021/bi4014825] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Infectious mammalian prions can be formed de novo from purified recombinant prion protein (PrP) substrate through a pathway that requires the sequential addition of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) and RNA cofactor molecules. Recent studies show that the initial interaction between PrP and POPG causes widespread and persistent conformational changes to form an insoluble intermediate species, termed PrP(Int1). Here, we characterize the mechanism and functional consequences of the interaction between POPG and PrP. Negative-stain electron microscopy of PrP(Int1) revealed the presence of amorphous aggregates. Pull-down and photoaffinity label experiments indicate that POPG induces the formation of a PrP(C) polybasic-domain-binding neoepitope within PrP(Int1). The ongoing presence of POPG is not required to maintain PrP(Int1) structure, as indicated by the absence of stoichiometric levels of POPG in solid-state NMR measurements of PrP(Int1). Together, these results show that a transient interaction with POPG cofactor unmasks a PrP(C) binding site, leading to PrP(Int1) aggregation.
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Affiliation(s)
- Ashley A Zurawel
- Departments of Biochemistry and ‡Medicine, Geisel School of Medicine at Dartmouth , Hanover, New Hampshire 03755, United States
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21
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Chapron Y, Charlet L, Sahai N. Fate of pathological prion (PrP(sc)92-138) in soil and water: prion-clay nanoparticle molecular dynamics. J Biomol Struct Dyn 2013; 32:1802-16. [PMID: 24152238 DOI: 10.1080/07391102.2013.836461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Pathogenic prion protein scrapie (PrP(sc)) may contaminate soils for decades and remain in water in colloidal suspension, providing infection pathways for animals through the inhalation of ingested dust and soil particles, and drinking water. We used molecular dynamics simulations to understand the strong binding mechanism of this pathogenic peptide with clay mineral surfaces and compared our results to experimental works. We restricted our model to the moiety PrP(92-138), which is a portion of the whole PrP(sc) molecule responsible for infectivity and modeled it using explicit solvating water molecules in contact with a pyrophyllite cleavage plane. Pyrophyllite is taken as a model for common soil clay, but it has no permanent structural charge. However, partial residual negative charges occur on the cleavage plane slab surface due to a slab charge unbalance. The charge is isotropic in 2D and it was balanced with K(+) ions. After partially removing potassium ions, the peptide anchors to the clay surface via up to 10 hydrogen bonds, between protonated lysine or histidine residues and the oxygen atoms of the siloxane cavities. Our results provide insight to the mechanism responsible for the strong association between the PrP(sc) peptide and clay nanoparticles and the associations present in contaminated soil and water which may lead to the infection of animals.
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Affiliation(s)
- Yves Chapron
- a AIED, Research , 108 rue du puy, La Terrasse , 38660 , France
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22
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Polyproline-II Helix in Proteins: Structure and Function. J Mol Biol 2013; 425:2100-32. [DOI: 10.1016/j.jmb.2013.03.018] [Citation(s) in RCA: 363] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 02/28/2013] [Accepted: 03/11/2013] [Indexed: 12/31/2022]
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23
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Luber S. Solvent Effects in Calculated Vibrational Raman Optical Activity Spectra of α-Helices. J Phys Chem A 2013; 117:2760-70. [DOI: 10.1021/jp400105u] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sandra Luber
- University of Zurich, Winterthurerstrasse
190, 8057 Zurich, Switzerland
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24
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Yamamoto S, Bouř P. Detection of Molecular Chirality by Induced Resonance Raman Optical Activity in Europium Complexes. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201204765] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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25
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Yamamoto S, Bouř P. Detection of Molecular Chirality by Induced Resonance Raman Optical Activity in Europium Complexes. Angew Chem Int Ed Engl 2012; 51:11058-61. [DOI: 10.1002/anie.201204765] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Indexed: 11/07/2022]
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26
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Dzwolak W, Kalinowski J, Johannessen C, Babenko V, Zhang G, Keiderling TA. On the DMSO-Dissolved State of Insulin: A Vibrational Spectroscopic Study of Structural Disorder. J Phys Chem B 2012; 116:11863-71. [DOI: 10.1021/jp3062674] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Wojciech Dzwolak
- Department of Chemistry, University of Warsaw, Pasteura 1, 02-093
Warsaw, Poland
| | - Jarosław Kalinowski
- Institute of High
Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland
| | - Christian Johannessen
- Manchester Interdisciplinary
Biocentre, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Viktoria Babenko
- Department of Chemistry, University of Warsaw, Pasteura 1, 02-093
Warsaw, Poland
| | - Ge Zhang
- Department of Chemistry, University of Illinois at Chicago, 845
West Taylor Street (m/c 111), Chicago, Illinois 60607-7061, United
States
| | - Timothy A. Keiderling
- Department of Chemistry, University of Illinois at Chicago, 845
West Taylor Street (m/c 111), Chicago, Illinois 60607-7061, United
States
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27
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Conformational analyses of peptides and proteins by vibrational Raman optical activity. Anal Bioanal Chem 2012; 403:2203-12. [DOI: 10.1007/s00216-012-5891-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 02/09/2012] [Accepted: 02/20/2012] [Indexed: 10/28/2022]
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28
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Camilloni C, De Simone A, Vranken WF, Vendruscolo M. Determination of secondary structure populations in disordered states of proteins using nuclear magnetic resonance chemical shifts. Biochemistry 2012; 51:2224-31. [PMID: 22360139 DOI: 10.1021/bi3001825] [Citation(s) in RCA: 274] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
One of the major open challenges in structural biology is to achieve effective descriptions of disordered states of proteins. This problem is difficult because these states are conformationally highly heterogeneous and cannot be represented as single structures, and therefore it is necessary to characterize their conformational properties in terms of probability distributions. Here we show that it is possible to obtain highly quantitative information about particularly important types of probability distributions, the populations of secondary structure elements (α-helix, β-strand, random coil, and polyproline II), by using the information provided by backbone chemical shifts. The application of this approach to mammalian prions indicates that for these proteins a key role in molecular recognition is played by disordered regions characterized by highly conserved polyproline II populations. We also determine the secondary structure populations of a range of other disordered proteins that are medically relevant, including p53, α-synuclein, and the Aβ peptide, as well as an oligomeric form of αB-crystallin. Because chemical shifts are the nuclear magnetic resonance parameters that can be measured under the widest variety of conditions, our approach can be used to obtain detailed information about secondary structure populations for a vast range of different protein states.
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Affiliation(s)
- Carlo Camilloni
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
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29
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Yamamoto S, Watarai H. Raman optical activity study on insulin amyloid- and prefibril intermediate. Chirality 2011; 24:97-103. [DOI: 10.1002/chir.21029] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 08/11/2011] [Indexed: 11/06/2022]
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30
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Profant V, Baumruk V, Li X, Šafařík M, Bouř P. Tracking of the Polyproline Folding by Density Functional Computations and Raman Optical Activity Spectra. J Phys Chem B 2011; 115:15079-89. [DOI: 10.1021/jp207706p] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Václav Profant
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116, Prague 2, Czech Republic
| | - Vladimír Baumruk
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116, Prague 2, Czech Republic
| | - Xiaojun Li
- Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Tromsø, N-9037 Tromsø, Norway
| | - Martin Šafařík
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo nám. 2, 166 10 Prague, Czech Republic
| | - Petr Bouř
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo nám. 2, 166 10 Prague, Czech Republic
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31
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32
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Templeton CM, Ostovar pour S, Hobbs JR, Blanch EW, Munger SD, Conn GL. Reduced sweetness of a monellin (MNEI) mutant results from increased protein flexibility and disruption of a distant poly-(L-proline) II helix. Chem Senses 2011; 36:425-34. [PMID: 21343241 DOI: 10.1093/chemse/bjr007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Monellin is a highly potent sweet-tasting protein but relatively little is known about how it interacts with the sweet taste receptor. We determined X-ray crystal structures of 3 single-chain monellin (MNEI) proteins with alterations at 2 core residues (G16A, V37A, and G16A/V37A) that induce 2- to 10-fold reductions in sweetness relative to the wild-type protein. Surprisingly, no changes were observed in the global protein fold or the positions of surface amino acids important for MNEI sweetness that could explain these differences in protein activity. Differential scanning calorimetry showed that while the thermal stability of each mutant MNEI was reduced, the least sweet mutant, G16A-MNEI, was not the least stable protein. In contrast, solution spectroscopic measurements revealed that changes in protein flexibility and the C-terminal structure correlate directly with protein activity. G16A mutation-induced disorder in the protein core is propagated via changes to hydrophobic interactions that disrupt the formation and/or position of a critical C-terminal poly-(L-proline) II helix. These findings suggest that MNEI interaction with the sweet taste receptor is highly sensitive to the relative positions of key residues across its protein surface and that loss of sweetness in G16A-MNEI may result from an increased entropic cost of binding.
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Affiliation(s)
- Catherine M Templeton
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
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33
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Humenik M, Scheibel T, Smith A. Spider silk: understanding the structure-function relationship of a natural fiber. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 103:131-85. [PMID: 21999996 DOI: 10.1016/b978-0-12-415906-8.00007-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Spider silk is of great interest because of its extraordinary physical properties, such as strength and toughness. Here we discuss how these physical properties relate to the way in which spiders have utilized this material in prey capture, forcing its evolution to a high-performance fiber. Female spiders can produce up to seven different types of silk, and all these have different physical properties, which relate to their various functions. The variation in properties are due to underlying differences in the proteins making up these silks. As our understanding of spider silk has increased in the recent years, it has been possible to produce recombinant versions of the respective proteins. Recombinant proteins open up the potential to produce synthetic silk fibers with properties similar to those of the natural spider silk threads.
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Affiliation(s)
- Martin Humenik
- Lehrstuhl Biomaterialien, Universität Bayreuth, Bayreuth, Germany
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34
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Luber S, Reiher M. Prediction of Raman Optical Activity Spectra of Chiral 3-Acetylcamphorato-Cobalt Complexes. Chemphyschem 2010; 11:1876-87. [DOI: 10.1002/cphc.201000121] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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35
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Kirby L, Agarwal S, Graham JF, Goldmann W, Gill AC. Inverse correlation of thermal lability and conversion efficiency for five prion protein polymorphic variants. Biochemistry 2010; 49:1448-59. [PMID: 20085368 DOI: 10.1021/bi901855z] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transmissible spongiform encephalopathies (TSEs) are associated with the accumulation of deposits of an abnormal form, PrP(Sc), of the host-encoded prion protein, PrP(C). Amino acid substitutions in PrP(C) have long been known to affect TSE disease outcome. In extreme cases in humans, various mutations appear to cause disease. In animals, polymorphisms are associated with variations in disease susceptibility and, in sheep, several polymorphisms have been identified that are known to affect susceptibility of carriers to disease. The mechanisms of polymorphism-mediated modulation of disease susceptibility remain elusive, and we have been studying the effect of various amino acid substitutions at PrP codon 164 (mouse numbering), in the beta2-alpha2 loop region of the prion protein, to attempt to decipher how polymorphisms may affect disease susceptibility. Combined in vitro approaches suggest that there exists a correlation between the ability of protein variants to convert to abnormal isoforms in seeded conversion assays versus the thermal stability of the protein variants, as judged by both thermal denaturation and an unseeded in vitro oligomerization assay. We have performed molecular dynamics simulations to give an indication of backbone conformational changes as a result of amino acid changes and found that alteration of a single residue in PrP can result in local changes in structure that may affect global conformation and stability. Our results are consistent with modulation of disease susceptibility through differential protein stability leading to enhanced generic misfolding of TSE resistance-associated protein variants.
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Affiliation(s)
- Louise Kirby
- Neuropathogenesis Division, The Roslin Institute and Royal (Dick) School of Veterinary Studies, The Alexander Robertson Building, Easter Bush Veterinary Centre, Roslin, Midlothian EH25 9RG, UK
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36
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Taubner LM, Bienkiewicz EA, Copié V, Caughey B. Structure of the flexible amino-terminal domain of prion protein bound to a sulfated glycan. J Mol Biol 2009; 395:475-90. [PMID: 19913031 DOI: 10.1016/j.jmb.2009.10.075] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 09/24/2009] [Accepted: 10/28/2009] [Indexed: 11/29/2022]
Abstract
The intrinsically disordered amino-proximal domain of hamster prion protein (PrP) contains four copies of a highly conserved octapeptide sequence, PHGGGWGQ, that is flanked by two polycationic residue clusters. This N-terminal domain mediates the binding of sulfated glycans, which can profoundly influence the conversion of PrP to pathological forms and the progression of prion disease. To investigate the structural consequences of sulfated glycan binding, we performed multidimensional heteronuclear ((1)H, (13)C, (15)N) NMR (nuclear magnetic resonance), circular dichroism (CD), and fluorescence studies on hamster PrP residues 23-106 (PrP 23-106) and fragments thereof when bound to pentosan polysulfate (PPS). While the majority of PrP 23-106 remain disordered upon PPS binding, the octarepeat region adopts a repeating loop-turn structure that we have determined by NMR. The beta-like turns within the repeats are corroborated by CD data demonstrating that these turns are also present, although less pronounced, without PPS. Binding to PPS exposes a hydrophobic surface composed of aligned tryptophan side chains, the spacing and orientation of which are consistent with a self-association or ligand binding site. The unique tryptophan motif was probed by intrinsic tryptophan fluorescence, which displayed enhanced fluorescence of PrP 23-106 when bound to PPS, consistent with the alignment of tryptophan side chains. Chemical-shift mapping identified binding sites on PrP 23-106 for PPS, which include the octarepeat histidine and an N-terminal basic cluster previously linked to sulfated glycan binding. These data may in part explain how sulfated glycans modulate PrP conformational conversions and oligomerizations.
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Affiliation(s)
- Lara M Taubner
- Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA.
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37
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Luber S, Reiher M. Intensity-Carrying Modes in Raman and Raman Optical Activity Spectroscopy. Chemphyschem 2009; 10:2049-57. [DOI: 10.1002/cphc.200900255] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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38
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Liégeois V. A Vibrational Raman Optical Activity Study of 1,1′-Binaphthyl Derivatives. Chemphyschem 2009; 10:2017-25. [DOI: 10.1002/cphc.200900115] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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39
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Liégeois V, Champagne B. Vibrational Raman optical activity of π-conjugated helical systems: Hexahelicene and heterohelicenes. J Comput Chem 2009; 30:1261-78. [DOI: 10.1002/jcc.21151] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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40
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Leliveld SR, Stitz L, Korth C. Expansion of the octarepeat domain alters the misfolding pathway but not the folding pathway of the prion protein. Biochemistry 2008; 47:6267-78. [PMID: 18473442 DOI: 10.1021/bi800253c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A misfolded conformation of the prion protein (PrP), PrP (Sc), is the essential component of prions, the infectious agents that cause transmissible neurodegenerative diseases. Insertional mutations that lead to an increase in the number of octarepeats (ORs) in PrP are linked to familial human prion disease. In this study, we investigated how expansion of the OR domain causes PrP to favor a prion-like conformation. Therefore, we compared the conformational and aggregation modulating properties of wild-type versus expanded OR domains, either as a fusion construct with the protein G B1 domain (GB1-OR) or as an integral part of full-length mouse PrP (MoPrP). Using circular dichroism spectroscopy, we first demonstrated that ORs are not unfolded but exist as an ensemble of three distinct conformers: polyproline helix-like, beta-turn, and "Trp-related". Domain expansion had little effect on the conformation of GB1-OR fusion proteins. When part of MoPrP however, OR domain expansion changed PrP's folding landscape, not by hampering the production of native alpha-helical monomers but by greatly reducing the propensity to form amyloid and by altering the assembly of misfolded, beta-rich aggregates. These features may relate to subtle pH-dependent conformational differences between wild-type and mutant monomers. In conclusion, we propose that PrP insertional mutations are pathogenic because they enhance specific misfolding pathways of PrP rather than by undermining native folding. This idea was supported by a trial bioassay in transgenic mice overexpressing wild-type MoPrP, where intracerebral injection of recombinant MoPrP with an expanded OR domain but not wild-type MoPrP caused prion disease.
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Affiliation(s)
- S Rutger Leliveld
- Institute for Molecular Biophysics (INB-2), Research Center Jülich, D-52425 Jülich, Germany
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41
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42
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Zhu F, Kapitan J, Tranter GE, Pudney PDA, Isaacs NW, Hecht L, Barron LD. Residual structure in disordered peptides and unfolded proteins from multivariate analysis and ab initio simulation of Raman optical activity data. Proteins 2008; 70:823-33. [PMID: 17729278 DOI: 10.1002/prot.21593] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Vibrational Raman optical activity (ROA), measured as a small difference in the intensity of Raman scattering from chiral molecules in right- and left-circularly polarized incident light, or as the intensity of a small circularly polarized component in the scattered light, is a powerful probe of the aqueous solution structure of proteins. The large number of structure-sensitive bands in protein ROA spectra makes multivariate analysis techniques such as nonlinear mapping (NLM) especially favorable for determining structural relationships between different proteins. We have previously used NLM to map a large dataset of peptide, protein, and virus ROA spectra into a readily visualizable two-dimensional space in which points close to or distant from each other, respectively, represent similar or dissimilar structures. As well as folded proteins, our dataset contains ROA spectra from many natively unfolded proteins, proteins containing both folded and unfolded domains, denatured partially structured molten globule and reduced protein states, together with folded proteins containing little or no alpha-helix or beta-sheet. In this article, the relative positions of these systems in the NLM plot are used to obtain information about any residual structure that they may contain. The striking differences between the structural propensities of proteins that are unfolded in their native states and those that are unfolded due to denaturation may be responsible for their often very different behavior, especially with regard to aggregation. An ab initio simulation of the Raman and ROA spectra of an alanine oligopeptide in the poly(L-proline) II-helical conformation confirms previous suggestions that this conformation is a significant structural element in disordered peptides and natively unfolded proteins. The use of ROA to identify and characterize proteins containing significant amounts of unfolded structure will, inter alia, be valuable in structural genomics/proteomics since unfolded sequences often inhibit crystallization.
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Affiliation(s)
- Fujiang Zhu
- WestCHEM, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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43
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Luber S, Herrmann C, Reiher M. Relevance of the Electric-Dipole−Electric-Quadrupole Contribution to Raman Optical Activity Spectra. J Phys Chem B 2008; 112:2218-32. [DOI: 10.1021/jp0756404] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Sandra Luber
- Laboratorium für Physikalische Chemie, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
| | - Carmen Herrmann
- Laboratorium für Physikalische Chemie, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
| | - Markus Reiher
- Laboratorium für Physikalische Chemie, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
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Zhu F, Davies P, Thompsett AR, Kelly SM, Tranter GE, Hecht L, Isaacs NW, Brown DR, Barron LD. Raman Optical Activity and Circular Dichroism Reveal Dramatic Differences in the Influence of Divalent Copper and Manganese Ions on Prion Protein Folding. Biochemistry 2008; 47:2510-7. [DOI: 10.1021/bi7022893] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fujiang Zhu
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
| | - Paul Davies
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
| | - Andrew R. Thompsett
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
| | - Sharon M. Kelly
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
| | - George E. Tranter
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
| | - Lutz Hecht
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
| | - Neil W. Isaacs
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
| | - David R. Brown
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
| | - Laurence D. Barron
- WestChem, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Chiralabs Ltd., BCIE, Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Oxfordshire OX5 1PF, United Kingdom
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45
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Liégeois V, Ruud K, Champagne B. An analytical derivative procedure for the calculation of vibrational Raman optical activity spectra. J Chem Phys 2007; 127:204105. [DOI: 10.1063/1.2801986] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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46
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Mikhonin AV, Asher SA. Direct UV Raman monitoring of 3(10)-helix and pi-bulge premelting during alpha-helix unfolding. J Am Chem Soc 2007; 128:13789-95. [PMID: 17044707 DOI: 10.1021/ja062269+] [Citation(s) in RCA: 50] [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
We used UV resonance Raman (UVRR) spectroscopy exciting at approximately 200 nm within the peptide bond pi --> pi* transitions to selectively study the amide vibrations of peptide bonds during alpha-helix melting. The dependence of the amide frequencies on their Psi Ramachandran angles and hydrogen bonding enables us, for the first time, to experimentally determine the temperature dependence of the peptide bond Psi Ramachandran angle population distribution of a 21-residue mainly alanine peptide. These Psi distributions allow us to easily discriminate between alpha-helix, 3(10)-helix and pi-helix/bulge conformations, obtain their individual melting curves, and estimate the corresponding Zimm and Bragg parameters. A striking finding is that alpha-helix melting is more cooperative and shows a higher melting temperature than previously erroneously observed. These Psi distributions also enable the experimental determination of the Gibbs free energy landscape along the Psi reaction coordinate, which further allows us to estimate the free energy barriers along the AP melting pathway. These results will serve as a benchmark for the numerous untested theoretical studies of protein and peptide folding.
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Affiliation(s)
- Aleksandr V Mikhonin
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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47
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Lefèvre T, Leclerc J, Rioux-Dubé JF, Buffeteau T, Paquin MC, Rousseau ME, Cloutier I, Auger M, Gagné SM, Boudreault S, Cloutier C, Pézolet M. Conformation of Spider Silk Proteins In Situ in the Intact Major Ampullate Gland and in Solution. Biomacromolecules 2007; 8:2342-4. [PMID: 17658884 DOI: 10.1021/bm7005517] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To understand the spinning process of dragline silk by spiders, the protein conformation before spinning has to be determined. Raman confocal spectromicroscopy has been used to study the conformation of the proteins in situ in the intact abdominal major ampullate gland of Nephila clavipes and Araneus diadematus spiders. The spectra obtained are typical of natively unfolded proteins and are very similar to that of a mixture of recombinant silk proteins. Vibrational circular dichroism reveals that the conformation is composed of random and polyproline II (PPII) segments with some alpha-helices. The alpha-helices seem to be located in the C-terminal part whereas the repetitive sequence is unfolded. The PPII structure can significantly contribute to the efficiency of the spinning process in nature.
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Affiliation(s)
- Thierry Lefèvre
- Department of Chemistry, Department of Biology, and Department of Biochemistry and Microbiology, Université Laval, Québec (Québec) G1K 7P4 Canada
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48
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Abstract
Among the diseases caused by protein misfolding is the family associated with the prion protein (PrP). This is a small extracellular membrane-anchored molecule of yet unknown function. Understanding how PrP folds both into its cellular and pathological forms is thought to be crucial for explaining protein misfolding in general and the specific role of PrP in disease. Since the first structure determination, an increasing number of structural studies of PrP have become available, showing that the protein is formed by a flexible N-terminal region and a highly conserved globular C-terminal domain. We review here the current knowledge on PrP structure. We focus on vertebrate PrPs and analyse in detail the similarities and the differences among the coordinates of the C-terminal domain of PrP from different species, in search for understanding the mechanism of disease-causing mutations and the molecular bases of species barrier.
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49
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Danecek P, Kapitán J, Baumruk V, Bednárová L, Kopecký V, Bour P. Anharmonic effects in IR, Raman, and Raman optical activity spectra of alanine and proline zwitterions. J Chem Phys 2007; 126:224513. [PMID: 17581069 DOI: 10.1063/1.2738065] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The difference spectroscopy of the Raman optical activity (ROA) provides extended information about molecular structure. However, interpretation of the spectra is based on complex and often inaccurate simulations. Previously, the authors attempted to make the calculations more robust by including the solvent and exploring the role of molecular flexibility for alanine and proline zwitterions. In the current study, they analyze the IR, Raman, and ROA spectra of these molecules with the emphasis on the force field modeling. Vibrational harmonic frequencies obtained with 25 ab initio methods are compared to experimental band positions. The role of anharmonic terms in the potential and intensity tensors is also systematically explored using the vibrational self-consistent field, vibrational configuration interaction (VCI), and degeneracy-corrected perturbation calculations. The harmonic approach appeared satisfactory for most of the lower-wavelength (200-1800 cm(-1)) vibrations. Modern generalized gradient approximation and hybrid density functionals, such as the common B3LYP method, provided a very good statistical agreement with the experiment. Although the inclusion of the anharmonic corrections still did not lead to complete agreement between the simulations and the experiment, occasional enhancements were achieved across the entire region of wave numbers. Not only the transitional frequencies of the C-H stretching modes were significantly improved but also Raman and ROA spectral profiles including N-H and C-H lower-frequency bending modes were more realistic after application of the VCI correction. A limited Boltzmann averaging for the lowest-frequency modes that could not be included directly in the anharmonic calculus provided a realistic inhomogeneous band broadening. The anharmonic parts of the intensity tensors (second dipole and polarizability derivatives) were found less important for the entire spectral profiles than the force field anharmonicities (third and fourth energy derivatives), except for a few weak combination bands which were dominated by the anharmonic tensor contributions.
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Affiliation(s)
- Petr Danecek
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo námestí 2, 16610 Prague 6, Czech Republic
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50
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Mikhonin AV, Asher SA, Bykov SV, Murza A. UV Raman spatially resolved melting dynamics of isotopically labeled polyalanyl peptide: slow alpha-helix melting follows 3(10)-helices and pi-bulges premelting. J Phys Chem B 2007; 111:3280-92. [PMID: 17388440 DOI: 10.1021/jp0654009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We used UV resonance Raman (UVRR) to examine the spatial dependence of the T-jump secondary structure relaxation of an isotopically labeled 21-residue mainly Ala peptide, AdP. The AdP penultimate Ala residues were perdeuterated, leaving the central residues hydrogenated, to allow separate monitoring of melting of the middle versus the end peptide bonds. For 5 to 30 degrees C T-jumps, the central peptide bonds show a approximately 2-fold slower relaxation time (189 +/- 31 ns) than do the exterior peptide bonds (97 +/- 15 ns). In contrast, for a 20 to 40 degrees C T-jump, the central peptide bond relaxation appears to be faster (56 +/- 6 ns) than that of the penultimate peptide bonds (131 +/- 46 ns). We show that, if the data are modeled as a two-state transition, we find that only exterior peptide bonds show anti-Arrhenius folding behavior; the middle peptide bonds show both normal Arrhenius-like folding and unfolding. This anti-Arrhenius behavior results from the involvement of pi-bulges/helices and 3(10)-helix states in the melting. The unusual temperature dependence of the (un)folding rates of the interior and exterior peptide bonds is due to the different relative (un)folding rates of 3(10)-helices, alpha-helices, and pi-bulges/helices. Pure alpha-helix unfolding rates are approximately 12-fold slower (approximately 1 micros) than that of pi-bulges and 3(10)-helices. In addition, we also find that the alpha-helix is most stable at the AdP N-terminus where eight consecutive Ala occur, whereas the three hydrophilic Arg located in the middle and at the C-terminus destabilize the alpha-helix in these regions and induce defects such as pi-bulges and 3(10)-helices.
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Affiliation(s)
- Aleksandr V Mikhonin
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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