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O'Neill NS, Alvarez NJ, Schweitzer-Stenner R. Tuning the thermostability of GHG gels by salts at different positions on the Hofmeister scale. Sci Rep 2024; 14:14742. [PMID: 38926473 PMCID: PMC11208536 DOI: 10.1038/s41598-024-65145-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 06/17/2024] [Indexed: 06/28/2024] Open
Abstract
The influence of Hofmeister cations (NH4+, Na+, Mg2+) and anions (H2PO4-, CH3COO-, Cl-, NO3-) on the thermostability of a GHG hydrogel was investigated. The combined results of UV circular dichroism (UVCD) and Small Amplitude Oscillatory Shear Rheology experiments reveal that the addition of salt reduces the stability of the gel phase and the underlying fibrils. In line with the cationic Hofmeister hierarchy, the chaotropic Mg2+ ions caused the greatest thermal destabilization of the gel phase with the gel → sol transition temperature Tgs value lowered by 10 °C. In the absence of salt, the gel → sol transition probed by the storage modulus and microscopy is biphasic. In the presence of salt, it becomes monophasic. Contrary to expectations the presence of Hofmeister anions leads to a nearly identical reduction of the gel → sol transition temperatures. However, UVCD spectra suggest that they affect the ππ-stacking between imidazole groups to a different extent. We relate the absence of ion specificity regarding the solubility of fibrils (probed by UVCD) to the observed enthalpy-entropy compensation of the dissolution process. Our results combined show how CD spectroscopy and rheology combined yields a more nuanced picture of the processes underlying the gel → sol transition.
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Affiliation(s)
- Nichole S O'Neill
- Department of Chemistry, Drexel University, Philadelphia, PA, 19104, USA
| | - Nicolas J Alvarez
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA, 19104, USA.
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O'Neill N, Lima TA, Furlan Ferreira F, Alvarez NJ, Schweitzer-Stenner R. Determining the nanostructure and main axis of gly-his-gly fibrils using the amide I' bands in FTIR, VCD, and Raman spectra. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 306:123584. [PMID: 37956526 DOI: 10.1016/j.saa.2023.123584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 09/29/2023] [Accepted: 10/26/2023] [Indexed: 11/15/2023]
Abstract
The zwitterionic tripeptide glycyl-histidine-glycine (GHG) has been shown to self-assemble into visible crystalline fibrils that form a gel-supporting network with a very high storage modulus. Here we elaborate on the theory and experimental setup behind our novel approach employed to determining the main fibril axis for these gel-forming fibrils by simulating the amide I band profile for infrared absorption (IR), vibrational circular dichroism (VCD), and visible Raman scattering. We also highlight that combining these three vibrational spectroscopies can help in validating structures that are solved using powder x-ray diffraction analysis (PXRD). The PXRD analysis yielded a GHG fibril unit cell with P21 symmetry containing two peptide monomers and two water molecules. The monomers adopt a conformation reminiscent of the distorted polyproline II conformation obtained for tri-lysine in aqueous solution. Stabilization occurs primarily through peptide-peptide intermolecular hydrogen bond interactions, while the role of water in peptide hydration is minimal. The comparison of simulated and experimental amide I' band profiles suggests that the xz plane of the crystal unit cell is being predominantly probed in the experimental IR and VCD spectra, with the x axis of the unit cell pointing in the direction of the main fibril axis. The monomer peptide in the unit cell interacts with six adjacent peptides forming hydrophobic channels by edge-to-face and parallel-displaced ππstacking in the y direction. These cores are further stabilized by a plethora of intermolecular interactions in the x and z directions. Our result suggests that the hydrophobic xz-surfaces would be a good target for the adsorption of hydrophobic drugs.
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Affiliation(s)
- Nichole O'Neill
- Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA; Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA
| | - Thamires A Lima
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA
| | - Fabio Furlan Ferreira
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, SP 09210-580, Brazil
| | - Nicolas J Alvarez
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA.
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Valls A, Altava B, Aseyev V, García-Verdugo E, Luis SV. Imidazolium based gemini amphiphiles derived from L-valine. Structural elements and surfactant properties. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.117434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Schweitzer-Stenner R, Alvarez NJ. Short Peptides as Tunable, Switchable, and Strong Gelators. J Phys Chem B 2021; 125:6760-6775. [PMID: 34133176 DOI: 10.1021/acs.jpcb.1c01447] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This Perspective outlines our current understanding of molecular gels composed of short and ultrashort peptides over the past 20 years. We discuss in detail the state of the art regarding self-assembly mechanisms, structure, thermal stability, and kinetics of fibril and/or network formation. Emphasis is put on the importance of the combined use of spectroscopy and rheology for characterizing and validating self-assembly models. While a range of peptide chemistries are reviewed, we focus our discussion on a unique new class of ultrashort peptide gelators, denoted GxG peptides (x: guest residue), which are capable of forming self-assembled fibril networks. The storage moduli of GxG gels are tunable up to 100 kPa depending on concentration, pH, and/or cosolvent. The sheet structures of the fibrils differ from canonical β-sheets. When appropriate, each section highlights opportunities for additional research and technologies that would further our understanding.
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Hesser M, Thursch LJ, Lewis TR, Lima TA, Alvarez NJ, Schweitzer-Stenner R. Concentration Dependence of a Hydrogel Phase Formed by the Deprotonation of the Imidazole Side Chain of Glycylhistidylglycine. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:6935-6946. [PMID: 34077210 DOI: 10.1021/acs.langmuir.1c00382] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Upon deprotonation of its imidazole group at ∼pH 6, the unblocked tripeptide glycylhistidylglycine (GHG) self-assembles into very long crystalline fibrils on a 10-1000 μm scale which are capable of forming a volume spanning network, that is, hydrogel. The critical peptide concentration for self-assembly at a pH of 6 lies between 50 and 60 mM. The fraction of peptides that self-assemble into fibrils depends on the concentration of deprotonated GHG. While IR spectra seem to indicate the formation of fibrils with standard amyloid fibril β-sheet structures, vibrational circular dichroism spectra show a strongly enhanced amide I' signal, suggesting that the formed fibrils exhibit significant chirality. The fibril chirality appears to be a function of peptide concentration. Rheological measurements reveal that the rate of gelation is concentration-dependent and that there is an optimum gel strength at intermediate peptide concentrations of ca. 175 mM. This paper outlines the unique properties of the GHG gel phase which is underlain by a surprisingly dense fibril network with an exceptionally strong modulus that make them potential additives for biomedical applications.
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Affiliation(s)
- Morgan Hesser
- Department of Chemistry, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Lavenia J Thursch
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Todd R Lewis
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Thamires A Lima
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Nicolas J Alvarez
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
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Thursch LJ, Lima TA, Schweitzer-Stenner R, Alvarez NJ. The impact of thermal history on the structure of glycylalanylglycine ethanol/water gels. J Pept Sci 2021; 27:e3305. [PMID: 33619869 DOI: 10.1002/psc.3305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 01/07/2021] [Accepted: 01/26/2021] [Indexed: 12/30/2022]
Abstract
This work revisits several open questions regarding the mechanisms of GAG fibril formation and structure as a function of temperature. The authors recently hypothesized that there is a solubility limit of GAG in ethanol/water that induces self-assembly. In other words, not all peptides can participate in fibrillization and some fraction is still soluble in solution. We show via FTIR spectroscopy that, indeed, free peptides are still present in solution after fibril formation, strongly supporting the solubility model. Furthermore, previous work showed GAG self-assembled into right-handed (phase I) or left-handed (phase II) chiral structures depending on temperature. In this study, we analyze the crystalline structure of phase I and II gels via WAXS and SAXS to compare their crystalline structures and order. Rheological measurements were used to investigate the response of the fibrillar network to temperature. They reveal that the ability of the peptide to self-assemble depends on the solubility at a given temperature and not on thermal history. Furthermore, the gel softening point, the linear viscoelastic gel microstructure, and relaxation spectrum are very similar between phase I and phase II. Overall, the temperature only affects the chirality of the fibrils and the formation kinetics.
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Affiliation(s)
- Lavenia J Thursch
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA, USA
| | - Thamires A Lima
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA, USA
| | | | - Nicolas J Alvarez
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA, USA
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Zhang S, Andrews B, Schweitzer-Stenner R, Urbanc B. Intrinsic Conformational Dynamics of Alanine in Water/Ethanol Mixtures: An Experiment-Driven Molecular Dynamics Study. J Phys Chem B 2020; 124:11600-11616. [PMID: 33300341 DOI: 10.1021/acs.jpcb.0c08245] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In vitro, cationic glycylalanylglycine (GAG) forms a hydrogel in binary mixtures of water and ethanol. In water, alanine residue is known for its high polyproline II (pPII) content. Spectroscopic data, including three J-coupling constants and amide I' profiles, indicate that addition of 42% ethanol to water significantly reduces the pPII content of alanine residue in GAG. Here, experiment-based Gaussian Ramachandran distributions of alanine in GAG at different ethanol fractions are examined and three MD force fields are evaluated with respect to their ability to capture these ethanol-induced conformational changes. MD simulations on monomeric GAG in eight different water/ethanol mixtures within Amber ff14SB, OPLS-AA/M, and CHARMM36m reveal that only Amber ff14SB partially captures the ethanol-induced conformational changes of alanine residue in monomeric GAG when 42% ethanol is added to water. MD simulations of 200 mM GAG ensembles in pure water and in the aqueous solution with 42% ethanol showcase the ability of CHARMM36m to capture the effect of ethanol on the average pPII content of alanine in GAG and provide a plausible explanation for this effect, which may stem from an increased propensity of GAG to form oligomers in the presence of ethanol.
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Affiliation(s)
- Shuting Zhang
- Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Brian Andrews
- Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | | | - Brigita Urbanc
- Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
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Levine MS, Ghosh M, Hesser M, Hennessy N, DiGuiseppi DM, Adler-Abramovich L, Schweitzer-Stenner R. Formation of peptide-based oligomers in dimethylsulfoxide: identifying the precursor of fibril formation. SOFT MATTER 2020; 16:7860-7868. [PMID: 32761042 DOI: 10.1039/d0sm00035c] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The well-studied dipeptide fluorenylmethyloxycarbonyl-di-phenylalanine (FmocFF) forms a rigid hydrogel upon dissolving in dimethylsulfoxide (DMSO) and dilution in H2O. Here, we explored the pre-aggregation of the peptide in pure DMSO by vibrational spectroscopies, X-ray powder diffraction and dynamic light scattering. Our results show an equilibrium between a dominant population of amorphous oligomers (on a length scale of 2 nm) and a small number of protofibrils/fibrils (on a length scale of 30 nm in the centimolar and of 200 nm in the sub-molar region). To probe the mechanism underlying the formation of these protofilaments, we measured the 1H-NMR, IR and visible Raman spectra of DMSO containing different FmocFF concentrations, ranging between 10 and 300 mM. Our data reveal that interpeptide hydrogen bonding leads to the self-assembly of FmocFF in the centimolar region, while π-π stacking between Fmoc-groups is observed above 100 mM. The high 3J(HNHCα) coupling constant of the N-terminal amide proton indicates that the Fmoc end-cap of the peptide locks the N-terminal residue into a conformational ensemble centered at a φ-value of ca. -120°, which corresponds to a parallel β-sheet type conformation. The 3J(HNHCα) coupling constant of the C-terminal residue is indicative of a polyproline II (pPII)/βt mixture. Our results suggest that the gelation of FmocFF caused by the addition of a small amount of water to DMSO mixtures is facilitated by the formation of disordered protofibrils in pure DMSO.
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Affiliation(s)
- Matthew S Levine
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | - Moumita Ghosh
- Department of Oral Biology, The Goldschleger School of Dental Medicine, Sackler Faculty of Medicine, and The Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel.
| | - Morgan Hesser
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | - Nathan Hennessy
- Department of Chemistry, The University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom
| | - David M DiGuiseppi
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | - Lihi Adler-Abramovich
- Department of Oral Biology, The Goldschleger School of Dental Medicine, Sackler Faculty of Medicine, and The Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel.
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DiGuiseppi DM, Thursch L, Alvarez NJ, Schweitzer-Stenner R. Exploring the gel phase of cationic glycylalanylglycine in ethanol/water. II. Spectroscopic, kinetic and thermodynamic studies. J Colloid Interface Sci 2020; 573:123-134. [DOI: 10.1016/j.jcis.2020.03.108] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Revised: 03/27/2020] [Accepted: 03/28/2020] [Indexed: 12/24/2022]
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Hesser M, Thursch L, Lewis T, DiGuiseppi D, Alvarez NJ, Schweitzer-Stenner R. The tripeptide GHG as an unexpected hydrogelator triggered by imidazole deprotonation. SOFT MATTER 2020; 16:4110-4114. [PMID: 32322858 DOI: 10.1039/d0sm00224k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The tripeptide glycyl-histidyl-glycine (GHG) self-assembles into long, crystalline fibrils forming a strong hydrogel (G'∼ 50 kPa) above a critical concentration of 40 mM upon the deprotonation of its imidazole group. Spectroscopic data reveal a mixture of helically twisted β-sheets and monomers to coexist in the gel phase.
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Affiliation(s)
- Morgan Hesser
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
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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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