1
|
Sauer MA, Heyden M. Frequency-Selective Anharmonic Mode Analysis of Thermally Excited Vibrations in Proteins. J Chem Theory Comput 2023; 19:5481-5490. [PMID: 37515568 PMCID: PMC10624555 DOI: 10.1021/acs.jctc.2c01309] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/31/2023]
Abstract
Low-frequency molecular vibrations at far-infrared frequencies are thermally excited at room temperature. As a consequence, thermal fluctuations are not limited to the immediate vicinity of local minima on the potential energy surface, and anharmonic properties cannot be ignored. The latter is particularly relevant in molecules with multiple conformations, such as proteins and other biomolecules. However, existing theoretical and computational frameworks for the analysis of molecular vibrations have so far been limited by harmonic or quasi-harmonic approximations, which are ill-suited to describe anharmonic low-frequency vibrations. Here, we introduce a fully anharmonic analysis of molecular vibrations based on a time correlation formalism that eliminates the need for harmonic or quasi-harmonic approximations. We use molecular dynamics simulations of a small protein to demonstrate that this new approach, in contrast to harmonic and quasi-harmonic normal modes, correctly identifies the collective degrees of freedom associated with molecular vibrations at any given frequency. This allows us to unambiguously characterize the anharmonic character of low-frequency vibrations in the far-infrared spectrum.
Collapse
Affiliation(s)
- Michael A Sauer
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| | - Matthias Heyden
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
| |
Collapse
|
2
|
Allen JL, Sanders TJ, Horvat J, Lewis RA, Rule KC. Determination of Vibrational Modes of l-Alanine Single Crystals by a Combination of Terahertz Spectroscopy Measurements and Density Functional Calculations. PHYSICAL REVIEW LETTERS 2023; 130:226901. [PMID: 37327443 DOI: 10.1103/physrevlett.130.226901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 03/17/2023] [Indexed: 06/18/2023]
Abstract
Density-functional theory may be used to predict both the frequency and the dipole moment of the fundamental oscillations of molecular crystals. Suitably polarized photons at those frequencies excite such oscillations. Thus, in principle, terahertz spectroscopy may confirm the calculated fundamental modes of amino acids. However, reports to date have multiple shortcomings: (a) material of uncertain purity and morphology and diluted in a binder material is employed; (b) consequently, vibrations along all crystal axes are excited simultaneously; (c) data are restricted to room temperature, where resonances are broad and the background dominant; and (d) comparison with theory has been unsatisfactory (in part because the theory assumes zero temperature). Here, we overcome all four obstacles, in reporting detailed low-temperature polarized THz spectra of single-crystal l-alanine, assigning vibrational modes using density-functional theory, and comparing the calculated dipole moment vector direction to the electric field polarization of the measured spectra. Our direct and detailed comparison of theory with experiment corrects previous mode assignments for l-alanine, and reveals unreported modes, previously obscured by closely spaced spectral absorptions. The fundamental modes are thereby determined.
Collapse
Affiliation(s)
- J L Allen
- Institute for Superconducting and Electronic Materials and School of Physics, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - T J Sanders
- Institute for Superconducting and Electronic Materials and School of Physics, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - J Horvat
- Institute for Superconducting and Electronic Materials and School of Physics, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - R A Lewis
- Institute for Superconducting and Electronic Materials and School of Physics, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - K C Rule
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234, Australia
| |
Collapse
|
3
|
|
4
|
Romo TD, Grossfield A, Markelz AG. Persistent Protein Motions in a Rugged Energy Landscape Revealed by Normal Mode Ensemble Analysis. J Chem Inf Model 2020; 60:6419-6426. [PMID: 33103888 DOI: 10.1021/acs.jcim.0c00879] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Proteins are allosteric machines that couple motions at distinct, often distant, sites to control biological function. Low-frequency structural vibrations are a mechanism of this long-distance connection and are often used computationally to predict correlations, but experimentally identifying the vibrations associated with specific motions has proved challenging. Spectroscopy is an ideal tool to explore these excitations, but measurements have been largely unable to identify important frequency bands. The result is at odds with some previous calculations and raises the question what methods could successfully characterize protein structural vibrations. Here we show the lack of spectral structure arises in part from the variations in protein structure as the protein samples the energy landscape. However, by averaging over the energy landscape as sampled using an aggregate 18.5 μs of all-atom molecular dynamics simulation of hen egg white lysozyme and normal-mode analyses, we find vibrations with large overlap with functional displacements are surprisingly concentrated in narrow frequency bands. These bands are not apparent in either the ensemble averaged vibrational density of states or isotropic absorption. However, in the case of the ensemble averaged anisotropic absorption, there is persistent spectral structure and overlap between this structure and the functional displacement frequency bands. We systematically lay out heuristics for calculating the spectra robustly, including the need for statistical sampling of the protein and inclusion of adequate water in the spectral calculation. The results show the congested spectrum of these complex molecules obscures important frequency bands associated with function and reveal a method to overcome this congestion by combining structurally sensitive spectroscopy with robust normal mode ensemble analysis.
Collapse
Affiliation(s)
- Tod D Romo
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642, United States
| | - Alan Grossfield
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642, United States
| | - Andrea G Markelz
- Department of Physics, University at Buffalo, SUNY, Buffalo, New York 14260, United States
| |
Collapse
|
5
|
Bordos E, Islam MT, Florence AJ, Halbert GW, Robertson J. Use of Terahertz-Raman Spectroscopy to Determine Solubility of the Crystalline Active Pharmaceutical Ingredient in Polymeric Matrices during Hot Melt Extrusion. Mol Pharm 2019; 16:4361-4371. [PMID: 31436094 PMCID: PMC6785800 DOI: 10.1021/acs.molpharmaceut.9b00703] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/14/2019] [Accepted: 08/22/2019] [Indexed: 11/29/2022]
Abstract
Polymer-based amorphous solid dispersions (ASDs) comprise one of the most promising formulation strategies devised to improve the oral bioavailability of poorly water-soluble drugs. Exploitation of such systems in marketed products has been limited because of poor understanding of physical stability. The internal disordered structure and increased free energy provide a thermodynamic driving force for phase separation and recrystallization, which can compromise therapeutic efficacy and limit product shelf life. A primary concern in the development of stable ASDs is the solubility of the drug in the polymeric carrier, but there is a scarcity of reliable analytical techniques for its determination. In this work, terahertz (THz) Raman spectroscopy was introduced as a novel empirical approach to determine the saturated solubility of crystalline active pharmaceutical ingredient (API) in polymeric matrices directly during hot melt extrusion. The solubility of a model compound, paracetamol, in two polymer systems, Affinisol 15LV (HPMC) and Plasdone S630 (copovidone), was determined by monitoring the API structural phase transitions from crystalline to amorphous as an excess of crystalline drug dissolved in the polymeric matrix. THz-Raman results enabled construction of solubility phase diagrams and highlighted significant differences in the solubilization capacity of the two polymer systems. The maximum stable API-load was 20 wt % for Affinisol 15LV and 40 wt % for Plasdone S630. Differential scanning calorimetry and XRPD studies corroborated these results. This approach has demonstrated a novel capability to provide real-time API-polymer phase equilibria data in a manufacturing relevant environment and promising potential to predict solid-state solubility and physical stability of ASDs.
Collapse
Affiliation(s)
- Ecaterina Bordos
- EPSRC
Future Manufacturing Research Hub, CMAC, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, U.K.
| | - Muhammad T. Islam
- EPSRC
Future Manufacturing Research Hub, CMAC, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, U.K.
| | - Alastair J. Florence
- EPSRC
Future Manufacturing Research Hub, CMAC, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, U.K.
| | - Gavin W. Halbert
- EPSRC
Future Manufacturing Research Hub, CMAC, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, U.K.
- Cancer
Research UK Formulation Unit, SIPBS, University
of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, U.K.
| | - John Robertson
- EPSRC
Future Manufacturing Research Hub, CMAC, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, U.K.
| |
Collapse
|
6
|
van Thor JJ. Coherent two-dimensional electronic and infrared crystallography. J Chem Phys 2019; 150:124113. [PMID: 30927871 DOI: 10.1063/1.5079319] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The two-dimensional electronic and infrared spectroscopy of oriented single crystals is sensitive to structure and point group symmetry. The third order response of crystals is generally different from measurements of isotropic solutions because each coherence path that contributes to the measured field scales to the ensemble average of the four-point correlation functions of the four field-dipole interactions involved in the respective Feynman paths. An analytical evaluation of 2D optical crystallography which depends on the crystal symmetry, laboratory orientation, and the orientation in the crystallographic frame is presented. Applying a symmetry operator in the basis of the allowed polarised radiation modes provides a method for evaluation of non-zero fourth rank tensor elements alternative to direct inspection methods. Uniaxial and biaxial systems are distinguished and the contributions to the rephasing and non-rephasing directions are evaluated for isolated and coupled oscillators. By exploiting coordinate analysis, the extension of non-linear electronic and infrared crystallography for coupled oscillators demonstrates the structural, directional, and symmetry dependent selection of coherences to the four-wave mixing signal.
Collapse
Affiliation(s)
- Jasper J van Thor
- Molecular Biophysics, Imperial College London, SW7 2AZ London, United Kingdom
| |
Collapse
|
7
|
Niessen KA, Xu M, George DK, Chen MC, Ferré-D'Amaré AR, Snell EH, Cody V, Pace J, Schmidt M, Markelz AG. Protein and RNA dynamical fingerprinting. Nat Commun 2019; 10:1026. [PMID: 30833555 PMCID: PMC6399446 DOI: 10.1038/s41467-019-08926-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 02/04/2019] [Indexed: 01/30/2023] Open
Abstract
Protein structural vibrations impact biology by steering the structure to functional intermediate states; enhancing tunneling events; and optimizing energy transfer. Strong water absorption and a broad continuous vibrational density of states have prevented optical identification of these vibrations. Recently spectroscopic signatures that change with functional state were measured using anisotropic terahertz microscopy. The technique however has complex sample positioning requirements and long measurement times, limiting access for the biomolecular community. Here we demonstrate that a simplified system increases spectroscopic structure to dynamically fingerprint biomacromolecules with a factor of 6 reduction in data acquisition time. Using this technique, polarization varying anisotropy terahertz microscopy, we show sensitivity to inhibitor binding and unique vibrational spectra for several proteins and an RNA G-quadruplex. The technique’s sensitivity to anisotropic absorbance and birefringence provides rapid assessment of macromolecular dynamics that impact biology. The characterization of biomacromolecule structural vibrations has been impeded by a broad continuous vibrational density of states obscuring molecule specific vibrations. A terahertz microscopy system using polarization control produces signatures to dynamically fingerprint proteins and a RNA G-quadruplex.
Collapse
Affiliation(s)
| | - Mengyang Xu
- Department of Physics, University at Buffalo, SUNY, Buffalo, NY, USA
| | - Deepu K George
- Department of Physics, University at Buffalo, SUNY, Buffalo, NY, USA
| | - Michael C Chen
- National Heart, Lung and Blood Institute, Bethesda, MD, USA
| | | | - Edward H Snell
- Hauptman-Woodward Medical Research Institute & Department of Structural Biology, University at Buffalo, SUNY, Buffalo, NY, USA
| | - Vivian Cody
- Hauptman-Woodward Medical Research Institute & Department of Structural Biology, University at Buffalo, SUNY, Buffalo, NY, USA
| | - James Pace
- Hauptman-Woodward Medical Research Institute & Department of Structural Biology, University at Buffalo, SUNY, Buffalo, NY, USA
| | - Marius Schmidt
- Department of Physics, University of Wisconsin, Milwaukee, WI, USA
| | - Andrea G Markelz
- Department of Physics, University at Buffalo, SUNY, Buffalo, NY, USA. .,Hauptman-Woodward Medical Research Institute & Department of Structural Biology, University at Buffalo, SUNY, Buffalo, NY, USA.
| |
Collapse
|
8
|
Pharmaceutical Terahertz Spectroscopy and Imaging. ADVANCES IN DELIVERY SCIENCE AND TECHNOLOGY 2016. [DOI: 10.1007/978-1-4939-4029-5_5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
|
9
|
Acbas G, Niessen KA, Snell EH, Markelz AG. Optical measurements of long-range protein vibrations. Nat Commun 2015; 5:3076. [PMID: 24430203 DOI: 10.1038/ncomms4076] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 12/09/2013] [Indexed: 12/20/2022] Open
Abstract
Protein biological function depends on structural flexibility and change. From cellular communication through membrane ion channels to oxygen uptake and delivery by haemoglobin, structural changes are critical. It has been suggested that vibrations that extend through the protein play a crucial role in controlling these structural changes. While nature may utilize such long-range vibrations for optimization of biological processes, bench-top characterization of these extended structural motions for engineered biochemistry has been elusive. Here we show the first optical observation of long-range protein vibrational modes. This is achieved by orientation-sensitive terahertz near-field microscopy measurements of chicken egg white lysozyme single crystals. Underdamped modes are found to exist for frequencies >10 cm(-1). The existence of these persisting motions indicates that damping and intermode coupling are weaker than previously assumed. The methodology developed permits protein engineering based on dynamical network optimization.
Collapse
Affiliation(s)
- Gheorghe Acbas
- Department of Physics, University at Buffalo, SUNY, 239 Fronczak Hall, Buffalo, New York 14260, USA
| | - Katherine A Niessen
- Department of Physics, University at Buffalo, SUNY, 239 Fronczak Hall, Buffalo, New York 14260, USA
| | - Edward H Snell
- Department of Structural Biology, Hauptman-Woodward Medical Research Institute, University at Buffalo, SUNY, 700 Ellicott St., Buffalo, New York 14203, USA
| | - A G Markelz
- 1] Department of Physics, University at Buffalo, SUNY, 239 Fronczak Hall, Buffalo, New York 14260, USA [2] Department of Structural Biology, Hauptman-Woodward Medical Research Institute, University at Buffalo, SUNY, 700 Ellicott St., Buffalo, New York 14203, USA
| |
Collapse
|
10
|
Niessen KA, Xu M, Markelz AG. Terahertz optical measurements of correlated motions with possible allosteric function. Biophys Rev 2015; 7:201-216. [PMID: 28510171 DOI: 10.1007/s12551-015-0168-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 02/26/2015] [Indexed: 10/23/2022] Open
Abstract
A suggested mechanism for allosteric response is the distortion of the energy landscape with agonist binding changing the protein structure's access to functional configurations. Intramolecular vibrations are indicative of the energy landscape and may have trajectories that enable functional conformational change. Here, we discuss the development of an optical method to measure the intramolecular vibrations in proteins, namely, crystal anisotropy terahertz microscopy, and the various approaches which can be used to identify the spectral data with specific structural motions.
Collapse
Affiliation(s)
- Katherine A Niessen
- Department of Physics, University at Buffalo (SUNY), Buffalo, NY, 14260, USA
| | - Mengyang Xu
- Department of Physics, University at Buffalo (SUNY), Buffalo, NY, 14260, USA
| | - A G Markelz
- Department of Physics, University at Buffalo (SUNY), Buffalo, NY, 14260, USA.
| |
Collapse
|
11
|
Sun Y, Zhong J, Zhang C, Zuo J, Pickwell-MacPherson E. Label-free detection and characterization of the binding of hemagglutinin protein and broadly neutralizing monoclonal antibodies using terahertz spectroscopy. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:037006. [PMID: 25757856 DOI: 10.1117/1.jbo.20.3.037006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 02/16/2015] [Indexed: 05/20/2023]
Abstract
Hemagglutinin (HA) is the main surface glycoprotein of the influenza A virus. The H9N2 subtype influenza A virus is recognized as the most possible pandemic strain as it has crossed the species barrier, infecting swine and humans. We use terahertz spectroscopy to study the hydration shell formation around H9 subtype influenza A virus's HA protein (H9 HA) as well as the detection of antigen binding of H9 HA with the broadly neutralizing monoclonal antibody. We observe a remarkable concentration dependent nonlinear response of the H9 HA, which reveals the formation process of the hydration shell around H9 HA molecules. Furthermore, we show that terahertz dielectric properties of the H9 HA are strongly affected by the presence of the monoclonal antibody F10 and that the terahertz dielectric loss tangent can be used to detect the antibody binding at lower concentrations than the standard ELISA test.
Collapse
MESH Headings
- Animals
- Antibodies, Monoclonal/analysis
- Antibodies, Monoclonal/immunology
- Antibodies, Neutralizing/analysis
- Antibodies, Neutralizing/immunology
- Antibodies, Viral
- Antigen-Antibody Reactions
- Enzyme-Linked Immunosorbent Assay
- Hemagglutinin Glycoproteins, Influenza Virus/analysis
- Hemagglutinin Glycoproteins, Influenza Virus/immunology
- Humans
- Influenza A Virus, H9N2 Subtype/chemistry
- Influenza A Virus, H9N2 Subtype/immunology
- Influenza, Human/virology
- Sensitivity and Specificity
- Swine
- Terahertz Spectroscopy/methods
Collapse
Affiliation(s)
- Yiwen Sun
- Shenzhen University, School of Medicine, National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, Department of Biomedical Engineering, Shenzhen 518060, Ch
| | - Junlan Zhong
- Shenzhen University, School of Medicine, National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, Department of Biomedical Engineering, Shenzhen 518060, Ch
| | - Cunlin Zhang
- Capital Normal University, Department of Physics, Beijing 100037, China
| | - Jian Zuo
- Capital Normal University, Department of Physics, Beijing 100037, China
| | | |
Collapse
|
12
|
Mahé J, Jaeqx S, Rijs AM, Gaigeot MP. Can far-IR action spectroscopy combined with BOMD simulations be conformation selective? Phys Chem Chem Phys 2015; 17:25905-14. [DOI: 10.1039/c5cp01518a] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The combination of conformation selective far-IR/UV double resonance spectroscopy with Born–Oppenheimer molecular dynamics (BOMD) simulations is presented here for the structural characterization of the Ac-Phe-Pro-NH2 peptide in the far-infrared spectral domain, i.e. for radiation below 800 cm−1.
Collapse
Affiliation(s)
- Jérôme Mahé
- LAMBE CNRS UMR8587
- Université d'Evry val d'Essonne
- 91025 Evry
- France
| | - Sander Jaeqx
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - Anouk M. Rijs
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - Marie-Pierre Gaigeot
- LAMBE CNRS UMR8587
- Université d'Evry val d'Essonne
- 91025 Evry
- France
- Institut Universitaire de France
| |
Collapse
|
13
|
Parrott EPJ, Zeitler JA. Terahertz time-domain and low-frequency Raman spectroscopy of organic materials. APPLIED SPECTROSCOPY 2015; 69:1-25. [PMID: 25506684 DOI: 10.1366/14-07707] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
With the ongoing proliferation of terahertz time-domain instrumentation from semiconductor physics into applied spectroscopy over the past decade, measurements at terahertz frequencies (1 THz ≡ 10(12) Hz ≡ 33 cm(-1)) have attracted a sustained growing interest, in particular the investigation of hydrogen-bonding interactions in organic materials. More recently, the availability of Raman spectrometers that are readily able to measure in the equivalent spectral region very close to the elastic scattering background has also grown significantly. This development has led to renewed efforts in performing spectroscopy at the interface between dielectric relaxation phenomena and vibrational spectroscopy. In this review, we briefly outline the underlying technology, the physical phenomena governing the light-matter interaction at terahertz frequencies, recent examples of spectroscopic studies, and the current state of the art in assigning spectral features to vibrational modes based on computational techniques.
Collapse
Affiliation(s)
- Edward P J Parrott
- Chinese University of Hong Kong, Department of Electronic Engineering, Shatin, New Territories, Hong Kong Sar, China
| | | |
Collapse
|
14
|
Optical nonlinearity and electric conductivity origin study on sucrose crystal by using IR, Raman, INS, NMR, and EPR spectroscopies. Carbohydr Res 2014; 395:29-37. [DOI: 10.1016/j.carres.2014.05.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 05/20/2014] [Accepted: 05/23/2014] [Indexed: 11/19/2022]
|
15
|
Sibik J, Sargent MJ, Franklin M, Zeitler JA. Crystallization and phase changes in paracetamol from the amorphous solid to the liquid phase. Mol Pharm 2014; 11:1326-34. [PMID: 24579729 PMCID: PMC3980750 DOI: 10.1021/mp400768m] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
For the case of paracetamol, we show how terahertz time-domain spectroscopy can be used to characterize the solid and liquid phase dynamics. Heating of supercooled amorphous paracetamol from 295 K in a covered sample under vacuum leads to its crystallization at 330 K. First, form III is formed followed by the transformation of form III to form II at 375 K, to form I at 405 K, and finally melting is observed around 455 K. We discuss the difference between the featureless spectra of the supercooled liquid and its liquid melt. Lastly, we studied the onset of crystallization from the supercooled liquid in detail and quantified its kinetics based on the Avrami-Erofeev model. We determined an effective rate constant of k = 0.056 min(-1) with a corresponding onset of crystallization at T = 329.5 K for a heating rate of 0.4 K min(-1).
Collapse
Affiliation(s)
- Juraj Sibik
- Department of Chemical Engineering and Biotechnology, University of Cambridge , New Museums Site, Pembroke Street, Cambridge CB2 3RA, United Kingdom
| | | | | | | |
Collapse
|
16
|
Jaeqx S, Oomens J, Cimas A, Gaigeot MP, Rijs AM. Gas-Phase Peptide Structures Unraveled by Far-IR Spectroscopy: Combining IR-UV Ion-Dip Experiments with Born-Oppenheimer Molecular Dynamics Simulations. Angew Chem Int Ed Engl 2014; 53:3663-6. [DOI: 10.1002/anie.201311189] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Indexed: 11/11/2022]
|
17
|
Jaeqx S, Oomens J, Cimas A, Gaigeot MP, Rijs AM. Gas-Phase Peptide Structures Unraveled by Far-IR Spectroscopy: Combining IR-UV Ion-Dip Experiments with Born-Oppenheimer Molecular Dynamics Simulations. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201311189] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|