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A Long Journey into the Investigation of the Structure–Dynamics–Function Paradigm in Proteins through the Activities of the Palermo Biophysics Group. BIOPHYSICA 2022. [DOI: 10.3390/biophysica2040040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
An overview of the biophysics activity at the Department of Physics and Chemistry Emilio Segrè of the University of Palermo is given. For forty years, the focus of the research has been on the protein structure–dynamics–function paradigm, with the aim of understanding the molecular basis of the relevant mechanisms and the key role of solvent. At least three research lines are identified; the main results obtained in collaboration with other groups in Italy and abroad are presented. This review is dedicated to the memory of Professors Massimo Ugo Palma, Maria Beatrice Palma Vittorelli, and Lorenzo Cordone, which were the founders of the Palermo School of Biophysics. We all have been, directly or indirectly, their pupils; we miss their enthusiasm for scientific research, their deep physical insights, their suggestions, their strict but always constructive criticisms, and, most of all, their friendship. This paper is dedicated also to the memory of Prof. Hans Frauenfelder, whose pioneering works on nonexponential rebinding kinetics, protein substates, and energy landscape have inspired a large part of our work in the field of protein dynamics.
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2
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De Michele V, Levantino M, Cupane A. Hysteresis in the temperature dependence of the IR bending vibration of deeply cooled confined water. J Chem Phys 2019; 150:224509. [PMID: 31202227 DOI: 10.1063/1.5096988] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using Fourier Transform Infrared (FTIR) spectroscopy, we investigate the temperature dependence of the bending vibrations of water confined in the pores of a silica hydrogel in the temperature interval of 270-180 K. We also investigate the presence of thermal hysteresis by cooling and reheating temperature scans. The results clearly show the presence, at about 230 K, of a crossover in the temperature dependence of the IR spectra; moreover, the presence of hysteresis is clearly demonstrated. By comparing FTIR data with neutron diffraction data and previous calorimetric data on the same samples, we conclude that the crossover and the hysteretical behavior do not involve a water glass transition or crystallization but are related to a first-order-like liquid-liquid transition.
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Affiliation(s)
- Vincenzo De Michele
- Dipartimento di Fisica e Chimica "Emilio Segrè," Università di Palermo, Viale delle Scienze Ed. 18, 90128 Palermo, Italy
| | - Matteo Levantino
- Dipartimento di Fisica e Chimica "Emilio Segrè," Università di Palermo, Viale delle Scienze Ed. 18, 90128 Palermo, Italy
| | - Antonio Cupane
- Dipartimento di Fisica e Chimica "Emilio Segrè," Università di Palermo, Viale delle Scienze Ed. 18, 90128 Palermo, Italy
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3
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Tsenkova R, Munćan J, Pollner B, Kovacs Z. Essentials of Aquaphotomics and Its Chemometrics Approaches. Front Chem 2018; 6:363. [PMID: 30211151 PMCID: PMC6121091 DOI: 10.3389/fchem.2018.00363] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Accepted: 07/30/2018] [Indexed: 01/13/2023] Open
Abstract
Aquaphotomics is a novel scientific discipline involving the study of water and aqueous systems. Using light-water interaction, it aims to extract information about the structure of water, composed of many different water molecular conformations using their absorbance bands. In aquaphotomics analysis, specific water structures (presented as water absorbance patterns) are related to their resulting functions in the aqueous systems studied, thereby building an aquaphotome-a database of water absorbance bands and patterns correlating specific water structures to their specific functions. Light-water interaction spectroscopic methods produce complex multidimensional spectral data, which require data processing and analysis to extract hidden information about the structure of water presented by its absorbance bands. The process of extracting information from water spectra in aquaphotomics requires a field-specific approach. It starts with an appropriate experimental design and execution to ensure high-quality spectral signals, followed by a multitude of spectral analysis, preprocessing and chemometrics methods to remove unwanted influences and extract water absorbance spectral pattern related to the perturbation of interest through the identification of activated water absorbance bands found among the common, consistently repeating and highly influential variables in all analytical models. The objective of this paper is to introduce the field of aquaphotomics and describe aquaphotomics multivariate analysis methodology developed during the last decade. Through a worked-out example of analysis of potassium chloride solutions supported by similar approaches from the existing aquaphotomics literature, the provided instruction should give enough information about aquaphotomics analysis i.e. to design and perform the experiment and data analysis as well as to represent water absorbance spectral pattern using various forms of aquagrams-specifically designed aquaphotomics graphs. The explained methodology is derived from analysis of near infrared spectral data of aqueous systems and will offer a useful and new tool for extracting data from informationally rich water spectra in any region. It is the hope of the authors that with this new tool at the disposal of scientists and chemometricians, pharmaceutical and biomedical spectroscopy will substantially progress beyond its state-of-the-art applications.
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Affiliation(s)
- Roumiana Tsenkova
- Biomeasurement Technology Laboratory, Graduate School of Agricultural Science, Kobe University, Kobe, Japan
| | - Jelena Munćan
- Biomeasurement Technology Laboratory, Graduate School of Agricultural Science, Kobe University, Kobe, Japan
- Nanolab, Biomedical Engineering Department, Faculty of Mechanical Engineering, University of Belgrade, Belgrade, Serbia
| | - Bernhard Pollner
- Department for Hygiene and Medical Microbiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Zoltan Kovacs
- Department of Physics and Control, Faculty of Food Science, Szent István University, Budapest, Hungary
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4
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Ridi F, Tonelli M, Fratini E, Chen SH, Baglioni P. Water as a Probe of the Colloidal Properties of Cement. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:2205-2218. [PMID: 29035549 DOI: 10.1021/acs.langmuir.7b02304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cement is produced by mixing mineral phases based on calcium silicates and aluminates with water. The hydration reaction of the mixture leads to a synthetic material with outstanding properties that can be used as a binder for construction applications. Despite the importance of cement in society, for a long time, the chemical reactions involved in its hydration remained poorly understood as a result of the complexity of hydration processes, nanostructure, and transport phenomena. This feature article reviews the recently obtained results using water as a probe to detail the essential features in the setting process. By examining the peculiar physicochemical properties of water, fundamental information on the evolving inorganic colloid matrix can be deduced, ranging from the fractal nanostructure of the inorganic silicate framework to the transport phenomena inside the developing porosity. A similar approach can be transferred to the investigation of a plethora of other complex systems, where water plays the main role in determining the final structural and transport properties (i.e., biomaterials, hydrogels, and colloids).
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Affiliation(s)
- Francesca Ridi
- Department of Chemistry "Ugo Schiff" and CSGI, University of Florence , via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence, Italy
| | - Monica Tonelli
- Department of Chemistry "Ugo Schiff" and CSGI, University of Florence , via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence, Italy
| | - Emiliano Fratini
- Department of Chemistry "Ugo Schiff" and CSGI, University of Florence , via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence, Italy
| | - Sow-Hsin Chen
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Piero Baglioni
- Department of Chemistry "Ugo Schiff" and CSGI, University of Florence , via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence, Italy
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5
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Montheil T, Echalier C, Martinez J, Subra G, Mehdi A. Inorganic polymerization: an attractive route to biocompatible hybrid hydrogels. J Mater Chem B 2018; 6:3434-3448. [DOI: 10.1039/c8tb00456k] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The sol–gel process is one of the main techniques leading to hybrid hydrogels that can be used in a wide scope of applications, especially in the biomedical field.
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Affiliation(s)
- Titouan Montheil
- Institut des Biomolécules Max Mousseron
- Université de Montpellier
- CNRS
- ENSCM
- Montpellier
| | - Cécile Echalier
- Institut des Biomolécules Max Mousseron
- Université de Montpellier
- CNRS
- ENSCM
- Montpellier
| | - Jean Martinez
- Institut des Biomolécules Max Mousseron
- Université de Montpellier
- CNRS
- ENSCM
- Montpellier
| | - Gilles Subra
- Institut des Biomolécules Max Mousseron
- Université de Montpellier
- CNRS
- ENSCM
- Montpellier
| | - Ahmad Mehdi
- Institut Charles Gerhardt Université de Montpellier
- CNRS
- ENSCM
- Montpellier
- France
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6
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Cupane A, Fomina M, Schirò G. The boson peak of deeply cooled confined water reveals the existence of a low-temperature liquid-liquid crossover. J Chem Phys 2014; 141:18C510. [DOI: 10.1063/1.4895793] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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7
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Takamuku T, Kouda Y, Shimomura T. Heat-induced phase separation of alkali chloride–HFIP–water mixtures. J Mol Liq 2014. [DOI: 10.1016/j.molliq.2013.03.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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D'Amico M, Schirò G, Cupane A, D'Alfonso L, Leone M, Militello V, Vetri V. High fluorescence of thioflavin T confined in mesoporous silica xerogels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:10238-10246. [PMID: 23844566 DOI: 10.1021/la402406g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Trapping of organic molecules and dyes within nanoporous matrices is of great interest for the potential creation of new materials with tailored features and, thus, different possible applications ranging from nanomedicine to material science. The understanding of the physical basis of entrapment and the spectral properties of the guest molecules within the host matrix is an essential prerequisite for the design and control of the properties of these materials. In this work, we show that a mesoporous silica xerogel can efficiently trap the dye thioflavin T (ThT, a molecule used as a marker of amyloid fibrils and with potential drug benefits), sequestering it from an aqueous solution and producing a highly fluorescent material with a ThT quantum yield 1500 times greater than that of the free molecule. The study of spectroscopical properties of this system and the comparison with fluorescence of an uncharged analogue of ThT give indications about the mechanism responsible for the fluorescence switching-on of ThT molecules during their uptaking into the glass. Diffusion and nanocapillarity are responsible for ThT absorption, whereas electrostatic interaction between positive ThT molecules and negative dangling ≡SiO groups covering the pore surfaces causes the immobilization of ThT molecules inside the pores and the enhancement of its fluorescence, in line with the molecular rotor model proposed for this dye. We also show that entrapment efficiency and kinetics can be tuned by varying the electrostatic properties of the dye and/or the matrix.
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Affiliation(s)
- Michele D'Amico
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Via Archirafi 36, I-90123 Palermo, Italy.
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9
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Haramaki H, Shimomura T, Umecky T, Takamuku T. SANS, Infrared, and 7Li and 23Na NMR Studies on Phase Separation of Alkali Halide–Acetonitrile–Water Mixtures by Cooling. J Phys Chem B 2013; 117:2438-48. [DOI: 10.1021/jp309881v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Hiroki Haramaki
- Department of Chemistry
and Applied Chemistry, Faculty
of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Takuya Shimomura
- Department of Chemistry
and Applied Chemistry, Faculty
of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Tatsuya Umecky
- Department of Chemistry
and Applied Chemistry, Faculty
of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Toshiyuki Takamuku
- Department of Chemistry
and Applied Chemistry, Faculty
of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
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10
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Schirò G, Cupane A, Vitrano E, Bruni F. Dielectric Relaxations in Confined Hydrated Myoglobin. J Phys Chem B 2009; 113:9606-13. [DOI: 10.1021/jp901420r] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Giorgio Schirò
- CNISM and Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Palermo, Italy, and CNISM and Dipartimento di Fisica “E. Amaldi”, Università di Roma Tre, Rome, Italy
| | - Antonio Cupane
- CNISM and Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Palermo, Italy, and CNISM and Dipartimento di Fisica “E. Amaldi”, Università di Roma Tre, Rome, Italy
| | - Eugenio Vitrano
- CNISM and Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Palermo, Italy, and CNISM and Dipartimento di Fisica “E. Amaldi”, Università di Roma Tre, Rome, Italy
| | - Fabio Bruni
- CNISM and Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Palermo, Italy, and CNISM and Dipartimento di Fisica “E. Amaldi”, Università di Roma Tre, Rome, Italy
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11
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Ridi F, Luciani P, Fratini E, Baglioni P. Water Confined in Cement Pastes as a Probe of Cement Microstructure Evolution. J Phys Chem B 2009; 113:3080-7. [DOI: 10.1021/jp808754t] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Francesca Ridi
- Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence, Italy
| | - Paola Luciani
- Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence, Italy
| | - Emiliano Fratini
- Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence, Italy
| | - Piero Baglioni
- Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3-Sesto Fiorentino, I-50019 Florence, Italy
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12
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Santangelo MG, Levantino M, Cupane A, Jeschke G. Solvation of a Probe Molecule by Fluid Supercooled Water in a Hydrogel at 200 K. J Phys Chem B 2008; 112:15546-53. [DOI: 10.1021/jp805131j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Maria Grazia Santangelo
- Laboratory of Physical Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland and Department of Physical and Astronomical Sciences (DSFA), University of Palermo, via Archirafi 36, I-90123 Palermo, Italy
| | - Matteo Levantino
- Laboratory of Physical Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland and Department of Physical and Astronomical Sciences (DSFA), University of Palermo, via Archirafi 36, I-90123 Palermo, Italy
| | - Antonio Cupane
- Laboratory of Physical Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland and Department of Physical and Astronomical Sciences (DSFA), University of Palermo, via Archirafi 36, I-90123 Palermo, Italy
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland and Department of Physical and Astronomical Sciences (DSFA), University of Palermo, via Archirafi 36, I-90123 Palermo, Italy
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13
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Garbuio V, Andreani C, Imberti S, Pietropaolo A, Reiter GF, Senesi R, Ricci MA. Proton quantum coherence observed in water confined in silica nanopores. J Chem Phys 2007; 127:154501. [DOI: 10.1063/1.2789436] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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14
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Capaccioli S, Ngai KL, Shinyashiki N. The Johari-Goldstein beta-relaxation of water. J Phys Chem B 2007; 111:8197-209. [PMID: 17585798 DOI: 10.1021/jp071857m] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
There is a plethora of experimental data on the dynamics of water in mixtures with glycerol, ethylene glycol, ethylene glycol oligomers, poly(ethylene glycol) 400 and 600, propanol, poly(vinyl pyrrolidone), poly(vinyl methylether), and other substances. In spite of the differences in the water contents, the chemical compositions, and the glass transition temperatures Tg of these aqueous mixtures, a faster relaxation originating from the water (called the nu-process) is omnipresent, sharing the following common properties. The relaxation time tau(nu) has Arrhenius temperature dependence at temperatures below Tg of the mixture. The activation energies of tau(nu) all fall within a neighborhood of 50 kJ/mol. At the same temperature where mixtures are all in their glassy states, the values of tau(nu) of several mixtures are comparable. The Arrhenius temperature dependence of tau(nu) does not continue to higher temperatures and instead it crosses over to a stronger temperature dependence at temperatures above Tg. The dielectric relaxation strength of the nu-process, Deltaepsilon(nu)(T), has a stronger temperature dependence above Tg than below, mimicking the change of enthalpy, entropy, and volume when crossing Tg. These general property of the nu-process (except for the magnitude of the activation energy) had been found before in the secondary relaxation of the faster component in several binary nonaqueous mixtures. Other properties of the secondary relaxation in these nonaqueous mixtures have helped to identify it as the Johari-Goldstein (JG) secondary relaxation of the faster component. The similarities in properties lead us to conclude that the nu-processes in water mixtures are the JG secondary relaxations of water. The conclusion is reinforced by the processes behaving similarly to the nu-process found in 6 A thick water layer (two molecular layers) in fully hydrated Na-vermiculite clay, and in water confined in molecular sieves, silica hydrogels, and poly(2-hydroxyethyl methacrylate) hydrogels.
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Affiliation(s)
- S Capaccioli
- Dipartimento di Fisica, Università di Pisa, Largo B. Pontecorvo 3, I-56127, Pisa, Italy
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15
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Ridi F, Fratini E, Milani S, Baglioni P. Near-Infrared Spectroscopy Investigation of the Water Confined in Tricalcium Silicate Pastes. J Phys Chem B 2006; 110:16326-31. [PMID: 16913759 DOI: 10.1021/jp060026y] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Near-infrared (NIR) spectroscopy has been employed to investigate the evolution of the vibrational spectrum of water entrapped in a tricalcium silicate paste. The overall free water, which decreases as a function of time due to the formation of the hydrated phases (portlandite, Ca(OH)(2), and hydrated calcium silicate, C-S-H) during the hydration reaction, is quantified by the decrease in the area of the NIR band at about 5000 cm(-1). The coexistence of two types of water in the hydrated phases (a "surface-interacting water" (type I) and a "bulklike water" (type II)) during the hydration is obtained by the analysis of the band at about 7000 cm(-1). The deconvolution of this band allows the quantification of the two water types. As the reaction advances, part of the "bulklike water" is converted to "surface-interacting water" in direct agreement with the C-S-H surface development. Finally, the Ca(OH)(2) formation can be concurrently monitored by NIR through the increase of a very sharp peak at 7083 cm(-1). Near-infrared spectroscopy allows determination in a very simple way of the most important features of the tricalcium silicate setting process.
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Affiliation(s)
- Francesca Ridi
- Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy
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16
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Tsenkova RN, Iordanova IK, Toyoda K, Brown DR. Prion protein fate governed by metal binding. Biochem Biophys Res Commun 2005; 325:1005-12. [PMID: 15541389 DOI: 10.1016/j.bbrc.2004.10.135] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2004] [Indexed: 11/19/2022]
Abstract
The conversion of the normal cellular prion protein to an abnormal isoform is considered to be causal to the prion diseases or transmissible spongiform encephalopathies. The prion protein is a copper binding protein but under some conditions may bind other metals. In particular, the binding of manganese has been suggested to convert the prion protein (PrP) to a protease resistant isoform. Therefore, the differences in the way the protein binds copper and manganese might be revealing in terms of the mechanism of conversion of the protein or its normal cellular activity. We report the use of near-infrared spectroscopy for studies on aqueous solutions of prion protein binding Cu or Mn. These alloforms of the protein were analyzed by spectral data acquisition and multivariate analysis. Our results indicate that PrP binds both Mn and Cu differently. Analyses of Cu binding suggest that the PrP-Cu complex protected Cu from the water increasing protein stability. PrP-Mn does not protect Mn from water interactions. A real-time study of the protein alloforms showed that PrP-Cu remains stable in solution, but that PrP-Mn underwent highly different changes that led to fibril formation.
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Affiliation(s)
- Roumiana N Tsenkova
- Department of Bioproduction Engineering, Faculty of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
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17
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Crupi V, Majolino * D, Migliardo P, Venuti V, Mizota T. Vibrational and diffusional dynamics of water in Mg50-A zeolites by spectroscopic investigation. Mol Phys 2004. [DOI: 10.1080/00268970412331293857] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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18
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Cammarata M, Levantino M, Cupane A, Longo A, Martorana A, Bruni F. Structure and dynamics of water confined in silica hydrogels: X-ray scattering and dielectric spectroscopy studies. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2003; 12 Suppl 1:S63-S66. [PMID: 15011018 DOI: 10.1140/epjed/e2003-01-016-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2003] [Indexed: 05/24/2023]
Abstract
We have used a sol-gel technique to obtain optically transparent hydrogels in which water is confined within a 3D silica matrix. In this work we report X-ray scattering and dielectric spectroscopy measurements on samples having different aging times and compare them with previously obtained results with near-infrared (NIR) absorption spectroscopy. X-ray scattering at room temperature enables to characterize the structure and size of the matrix pores and the non-uniform distribution of water inside the hydrogel. Broad band dielectric spectroscopy in the temperature range 130-280 K enables to study water dynamics. In aged hydrogels two relaxations are clearly evident and show characteristic temperature dependence. The faster relaxation has an Arrhenius behavior in the whole temperature range investigated with an activation enthalpy of approximately 50 kJ/mol; it is attributed to water molecules strongly interacting with the silica matrix. The slower relaxation has a markedly non-Arrhenius behavior which can be fitted with a Vogel-Fulcher-Tamman (VFT) relation with critical temperature of approximately 100 K and activation enthalpies of 35 and 95 kJ/mol at 300 and 170 K respectively; it is attributed to water molecules within the pores that do not interact strongly with the matrix and behave collectively. The VFT temperature dependence of the dielectric relaxation time suggests that this water does not crystallize, in agreement with previous results from NIR spectroscopy.
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Affiliation(s)
- M Cammarata
- INFM and Dept. of Physical and Astronomical Sciences, University of Palermo, Palermo, Italy
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19
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Rovere M, Gallo P. Effects of confinement on static and dynamical properties of water. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2003; 12:77-81. [PMID: 15007683 DOI: 10.1140/epje/i2003-10027-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Molecular-dynamics results on water confined in a silica pore are reviewed and discussed in connection with experiments performed on water in Vycor and with studies of water in contact with proteins. The properties of confined water are studied as a function of both temperature and hydration level. The interaction of water in the film close to the substrate with the silica atoms induces a strong distortion of the hydrogen bond network. At high hydration levels a double dynamical regime is observed. At low hydration an anomalous diffusion is found upon supercooling with a transition from a Brownian to a non-Brownian regime on approaching the substrate in agreement with results found in studies of water in contact with globular proteins.
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Affiliation(s)
- M Rovere
- Dipartimento di Fisica E. Amaldi, Universitá Roma Tre, INFM Unitá Roma Tre, Italy.
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20
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Santangelo MG, Levantino M, Vitrano E, Cupane A. Ferricytochrome c encapsulated in silica hydrogels: correlation between active site dynamics and solvent structure. Biophys Chem 2003; 103:67-75. [PMID: 12504255 DOI: 10.1016/s0301-4622(02)00235-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ferricytochrome c encapsulated in silica hydrogels has been prepared by the sol-gel technique following, with some modifications, the procedure originally developed by Ellerby et al. (Science 255 1113 (1992)). A suitable preparation of hydrogels enables having both 'wet' and 'dry' samples. Wet samples have a high water content: as the temperature is lowered below approximately 260 K, water freezes and the samples crack. On the contrary, dry samples have a low water content (hydration h approximately equal 0.35): in these conditions water does not freeze even at cryogenic temperatures and the samples remain transparent and non-cracking. The dynamics of ferricytochrome c and its dependence on the surrounding medium have been studied by optical absorption spectroscopy in the temperature range 10-300 K. At each temperature, spectra were collected both in the Soret region and in the near infrared at approximately 1.45 microm (the water overtone band); this enables probing the local dynamics of the protein active site as well as the 'structure' of water molecules present in the sample. The data show that sol-gel encapsulation 'per se' does not alter the protein active site dynamics, but rather introduces an increased local heterogeneity. We find a correlation between active site dynamics and water structure: in the wet hydrogel, freezing of water quenches the ensemble of soft modes linearly coupled to the Soret transition; while, in the dry hydrogel, water does not freeze and an active site dynamic behavior--similar to the non-freezing water/glycerol solution--is observed.
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Affiliation(s)
- Maria Grazia Santangelo
- National Institute for the Physics of Matter and Department of Physical and Astronomical Sciences, University of Palermo, via Archirafi 36, I-90123, Palermo, Italy
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