1
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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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2
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Schweitzer-Stenner R. The relevance of short peptides for an understanding of unfolded and intrinsically disordered proteins. Phys Chem Chem Phys 2023; 25:11908-11933. [PMID: 37096579 DOI: 10.1039/d3cp00483j] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2023]
Abstract
Over the last thirty years the unfolded state of proteins has attracted considerable interest owing to the discovery of intrinsically disordered proteins which perform a plethora of functions despite resembling unfolded proteins to a significant extent. Research on both, unfolded and disordered proteins has revealed that their conformational properties can deviate locally from random coil behavior. In this context results from work on short oligopeptides suggest that individual amino acid residues sample the sterically allowed fraction of the Ramachandran plot to a different extent. Alanine has been found to exhibit a peculiarity in that it has a very high propensity for adopting polyproline II like conformations. This Perspectives article reviews work on short peptides aimed at exploring the Ramachandran distributions of amino acid residues in different contexts with experimental and computational means. Based on the thus provided overview the article discussed to what extent short peptides can serve as tools for exploring unfolded and disordered proteins and as benchmarks for the development of a molecular dynamics force field.
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3
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Thursch LJ, Lima TA, O'Neill N, Ferreira FF, Schweitzer-Stenner R, Alvarez NJ. Influence of central sidechain on self-assembly of glycine-x-glycine peptides. SOFT MATTER 2023; 19:394-409. [PMID: 36454226 DOI: 10.1039/d2sm01082h] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Low molecular weight gelators (LMWGs) are the subject of intense research for a range of biomedical and engineering applications. Peptides are a special class of LMWG, which offer infinite sequence possibilities and, therefore, engineered properties. This work examines the propensity of the GxG peptide family, where x denotes a guest residue, to self-assemble into fibril networks via changes in pH and ethanol concentration. These triggers for gelation are motivated by recent work on GHG and GAG, which unexpectedly self-assemble into centimeter long fibril networks with unique rheological properties. The propensity of GxG peptides to self-assemble, and the physical and chemical properties of the self-assembled structures are characterized by microscopy, spectroscopy, rheology, and X-ray diffraction. Interestingly, we show that the number, length, size, and morphology of the crystalline self-assembled aggregates depend significantly on the x-residue chemistry and the solution conditions, i.e. pH, temperature, peptide concentration, etc. The different x-residues allow us to probe the importance of different peptide interactions, e.g. π-π stacking, hydrogen bonding, and hydrophobicity, on the formation of fibrils. We conclude that fibril formation requires π-π stacking interactions in pure water, while hydrogen bonding can form fibrils in the presence of ethanol-water solutions. These results validate and support theoretical arguments on the propensity for self-assembly and leads to a better understanding of the relationship between peptide chemistry and fibril self-assembly. Overall, GxG peptides constitute a unique family of peptides, whose characterization will aid in advancing our understanding of self-assembly driving forces for fibril formation in peptide systems.
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Affiliation(s)
- Lavenia J Thursch
- 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.
| | - Nichole O'Neill
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA.
- Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA.
| | - Fabio F Ferreira
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, São Paulo, Brazil
| | | | - Nicolas J Alvarez
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA.
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4
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O'Neill N, Lima TA, Ferreira FF, Thursch L, Alvarez N, Schweitzer-Stenner R. Forbidden Secondary Structures Found in Gel-Forming Fibrils of Glycylphenylalanylglycine. J Phys Chem B 2022; 126:8080-8093. [PMID: 36194765 DOI: 10.1021/acs.jpcb.2c05010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The zwitterionic l-tripeptide glycylphenylalanylglycine self-assembles into very long crystalline fibrils in an aqueous solution, which causes the formation of an exceptionally strong gel phase (G' ∼ 5 × 106 Pa). The Rietveld refinement analysis of its powder X-ray diffraction (PXRD) pattern reveals a unit cell with four peptides forming a P212121 space group and adopting an inverse polyproline II conformation, that is, a right-handed helical structure that occupies the "forbidden" region of the Ramachandran plot. This unusual structure is stabilized by a plethora of intermolecular interactions facilitated by the large number of different functional groups of the unblocked tripeptide. Comparisons of simulated and experimental Fourier transform infrared and vibrational circular dichroism (VCD) amide I' profiles corroborate the PXRD structure. Our experimental setup reduces the sample to a quasi-two-dimensional network of fibrils. We exploited the influence of this reduced dimensionality on the amide I VCD to identify the main fibril axis. We demonstrate that PXRD, vibrational spectroscopy, and amide I simulations provide a powerful toolset for secondary structure and fibril axis determination.
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Affiliation(s)
- Nichole O'Neill
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States.,Department of Chemical Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Thamires A Lima
- Department of Chemical Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Fabio Furlan Ferreira
- Center for Natural and Human Sciences (CCNH), Federal University of ABC (UFABC), Av. Dos Estados, 5001, S622-3, Santo André, São Paulo09210-580, Brazil
| | - Lavenia Thursch
- Department of Chemical Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Nicolas Alvarez
- Department of Chemical Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Reinhard Schweitzer-Stenner
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
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5
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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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6
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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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7
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Xing Z, Chen Y, Qiu F. Alternative Causal Link between Peptide Fibrillization and β-Strand Conformation. ACS OMEGA 2021; 6:12904-12912. [PMID: 34056442 PMCID: PMC8154227 DOI: 10.1021/acsomega.1c01423] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 04/23/2021] [Indexed: 02/08/2023]
Abstract
In the prevailing phenomenon of peptide fibrillization, β-strand conformation has long been believed to be an important structural basis for peptide assembly. According to a widely accepted theory, in most peptide fibrillization processes, peptide monomers need to intrinsically take or transform to β-strand conformation before they can undergo ordered packing to form nanofibers. In this study, we reported our findings on an alternative peptide fibrillization pathway starting from a disordered secondary structure, which could then transform to β-strand after fibrillization. By using circular dichroism, thioflavin-T binding test, and transmission electron microscopy, we studied the secondary structure and assembly behavior of Ac-RADARADARADARADA-NH2 (RADA16-I) in a low concentration range. The effects of peptide concentration, solvent polarity, pH, and temperature were investigated in detail. Our results showed that at very low concentrations, even though the peptide was in a disordered secondary structure, it could still form nanofibers through intermolecular assembly, and under higher peptide concentrations, the transformation from the disordered structure to β-strand could happen with the growth of nanofibers. Our results indicated that even without ordered β-strand conformation, driving forces such as hydrophobic interaction and electrostatic interaction could still play a determinative role in the self-assembly of peptides. At least in some cases, the formation of β-strand might be the consequence rather than the cause of peptide fibrillization.
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Affiliation(s)
- Zhihua Xing
- Laboratory
of Anesthesia and Critical Care Medicine, Translational Neuroscience
Center and National Clinical Research Center for Geriatrics, West
China Hospital, Sichuan University, Chengdu 610041, China
- Laboratory
of Ethnopharmacology, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Yongzhu Chen
- Laboratory
of Anesthesia and Critical Care Medicine, Translational Neuroscience
Center and National Clinical Research Center for Geriatrics, West
China Hospital, Sichuan University, Chengdu 610041, China
- Periodical
Press of West China Hospital, Sichuan University, Chengdu 610041, China
| | - Feng Qiu
- Laboratory
of Anesthesia and Critical Care Medicine, Translational Neuroscience
Center and National Clinical Research Center for Geriatrics, West
China Hospital, Sichuan University, Chengdu 610041, China
- National-Local
Joint Engineering Research Center of Translational Medicine of Anesthesiology,
West China Hospital, Sichuan University, Chengdu 610041, China
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8
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Katiyar A, Thompson WH. Temperature Dependence of Peptide Conformational Equilibria from Simulations at a Single Temperature. J Phys Chem A 2021; 125:2374-2384. [PMID: 33720712 DOI: 10.1021/acs.jpca.1c00150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding the structure of proteins is key to unraveling their function in biological processes. Thus, significant attention has been paid to the calculation of conformational free energies. In this paper, we demonstrate a simple extension of fluctuation theory that permits the calculation of the temperature derivative of the conformational free energy, and hence the internal energy and entropy, from single-temperature simulations. The method further enables the decomposition into the contribution of different interactions present in the system to the internal energy surface. We illustrate the method for the canonical test system of alanine dipeptide in aqueous solution, for which we examine the free energy as a function of two dihedral angles. This system, like many, is most effectively treated using accelerated sampling methods and we show how the present approach is compatible with an important class of these, those that introduce a bias potential, by implementing it within metadynamics.
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Affiliation(s)
- Ankita Katiyar
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Ward H Thompson
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
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9
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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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10
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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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11
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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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12
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Glycine in Water Favors the Polyproline II State. Biomolecules 2020; 10:biom10081121. [PMID: 32751224 PMCID: PMC7463814 DOI: 10.3390/biom10081121] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/22/2020] [Accepted: 07/27/2020] [Indexed: 01/09/2023] Open
Abstract
Conformational preferences of amino acid residues in water are determined by the backbone and side-chain properties. Alanine is known for its high polyproline II (pPII) propensity. The question of relative contributions of the backbone and side chain to the conformational preferences of alanine and other amino acid residues in water is not fully resolved. Because glycine lacks a heavy-atom side chain, glycine-based peptides can be used to examine to which extent the backbone properties affect the conformational space. Here, we use published spectroscopic data for the central glycine residue of cationic triglycine in water to demonstrate that its conformational space is dominated by the pPII state. We assess three commonly used molecular dynamics (MD) force fields with respect to their ability to capture the conformational preferences of the central glycine residue in triglycine. We show that pPII is the mesostate that enables the functional backbone groups of the central residue to form the most hydrogen bonds with water. Our results indicate that the pPII propensity of the central glycine in GGG is comparable to that of alanine in GAG, implying that the water-backbone hydrogen bonding is responsible for the high pPII content of these residues.
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13
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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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14
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Exploring the gel phase of cationic glycylalanylglycine in ethanol/water. I. Rheology and microscopy studies. J Colloid Interface Sci 2020; 564:499-509. [DOI: 10.1016/j.jcis.2019.10.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/07/2019] [Accepted: 10/08/2019] [Indexed: 01/04/2023]
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15
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DiGuiseppi D, Thursch L, Alvarez NJ, Schweitzer-Stenner R. Exploring the thermal reversibility and tunability of a low molecular weight gelator using vibrational and electronic spectroscopy and rheology. SOFT MATTER 2019; 15:3418-3431. [PMID: 30938745 DOI: 10.1039/c9sm00104b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Cationic glycylalanylglycine (GAG) self-assembles into a gel in a 55 mol% ethanol/45 mol% water mixture. The gel exhibits a network of crystalline fibrils grown to lengths on a 10-4-10-5 m scale (Farrel et al., Soft Matter, 2016, 12, 6096-6110). Rheological data are indicative of a rather strong gel with storage moduli in the 10 kPa regime. Spectroscopic data revealed the existence of two gel phases; one forms below T = 15 °C (phase I) while the other one forms in a temperature range between 15 °C and the melting temperature of ca. 35 °C (phase II). We explored the reformation of the cationic GAG gel in 55 mol% ethanol/45 mol% water after thermal annealing by spectroscopic and rheological means. Our data reveal that even a short residence time of 5 minutes in the sol phase at 50 °C produced a delay of the gelation process and a gel of lesser strength. These observations suggest that the residence time at the annealing temperature can be used to adjust the strength of both gel phases. Our spectroscopic data show that the annealing process does not change the chirality of peptide fibrils in the two gel phases and that the initial aggregation state of the reformation process is by far more ordered for phase I than it is for phase II. In the gel phases of GAG/ethanol/water mixtures, ethanol seems to function as a sort of catalyst that enables the self-assembly of the peptide in spite of its low intrinsic propensity for aggregation.
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Affiliation(s)
- David DiGuiseppi
- Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA.
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16
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Ilawe NV, Schweitzer-Stenner R, DiGuiseppi D, Wong BM. Is a cross-β-sheet structure of low molecular weight peptides necessary for the formation of fibrils and peptide hydrogels? Phys Chem Chem Phys 2019; 20:18158-18168. [PMID: 29696249 DOI: 10.1039/c8cp00691a] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Short peptides have emerged as versatile building blocks for supramolecular structures and hydrogels. In particular, the presence of aromatic amino acid residues and/or aromatic end groups is generally considered to be a prerequisite for initiating aggregation of short peptides into nanotubes or cross β-sheet type fibrils. However, the cationic GAG tripeptide surprisingly violates these rules. Specifically, in water/ethanol mixtures, GAG peptides aggregate into very long crystalline fibrils at temperatures below 35 °C where they eventually form a spanning network structure and, thus, a hydrogel. Two gel phases are formed in this network, and they differ substantially in chirality and thickness of the underlying fibrils, their rheological parameters, and the kinetics of oligomerization, fibrilization, and gel formation. The spectroscopic data strongly suggests that the observed fibrils do not exhibit canonical cross β-sheet structures and are indicative of a yet unknown secondary conformation. To complement our unusual experimental observations in this perspective article, we performed large-scale DFT calculations to probe the geometry and spectroscopic properties of these GAG oligomers. Most importantly, our experimental and computational results yield rather unconventional structures that are not reminiscent of classical cross-β-sheet structures, and we give two extremely likely candidates for oligomer structures that are consistent with experimental amide I' profiles in IR and vibrational circular dichroism (VCD) spectra of the two gel phases.
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Affiliation(s)
- Niranjan V Ilawe
- Department of Chemical & Environmental Engineering, and Materials Science & Engineering Program, University of California-Riverside, Riverside, CA 92521, USA.
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17
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Sun CQ. Aqueous charge injection: solvation bonding dynamics, molecular nonbond interactions, and extraordinary solute capabilities. INT REV PHYS CHEM 2018. [DOI: 10.1080/0144235x.2018.1544446] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Chang Q. Sun
- EBEAM, Yangtze Normal University, Chongqing, People's Republic of China
- NOVITAS, EEE, Nanyang Technological University, Singapore, Singapore
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18
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DiGuiseppi D, Milorey B, Lewis G, Kubatova N, Farrell S, Schwalbe H, Schweitzer-Stenner R. Probing the Conformation-Dependent Preferential Binding of Ethanol to Cationic Glycylalanylglycine in Water/Ethanol by Vibrational and NMR Spectroscopy. J Phys Chem B 2017; 121:5744-5758. [DOI: 10.1021/acs.jpcb.7b02899] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | - Nina Kubatova
- Institut
für Organische Chemie und Chemische Biologie, Johann Wolfgang Goethe-Universität, 60438 Frankfurt am Main, Germany
| | | | - Harald Schwalbe
- Institut
für Organische Chemie und Chemische Biologie, Johann Wolfgang Goethe-Universität, 60438 Frankfurt am Main, Germany
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19
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Secondary structure and colloidal stability of beta-casein in microheterogeneous water-ethanol solutions. Food Hydrocoll 2017. [DOI: 10.1016/j.foodhyd.2016.09.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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20
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Mondal S, Biswas B, Nandy T, Singh PC. Hydrophobic fluorine mediated switching of the hydrogen bonding site as well as orientation of water molecules in the aqueous mixture of monofluoroethanol: IR, molecular dynamics and quantum chemical studies. Phys Chem Chem Phys 2017; 19:24667-24677. [DOI: 10.1039/c7cp04663d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Fluorination of ethanol changes orientation of water in its aqueous mixture.
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Affiliation(s)
- Saptarsi Mondal
- Department of Spectroscopy
- Indian Association for the Cultivation of Science
- Kolkata
- India
| | - Biswajit Biswas
- Department of Spectroscopy
- Indian Association for the Cultivation of Science
- Kolkata
- India
| | - Tonima Nandy
- Department of Spectroscopy
- Indian Association for the Cultivation of Science
- Kolkata
- India
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21
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Farrell S, DiGuiseppi D, Alvarez N, Schweitzer-Stenner R. The interplay of aggregation, fibrillization and gelation of an unexpected low molecular weight gelator: glycylalanylglycine in ethanol/water. SOFT MATTER 2016; 12:6096-6110. [PMID: 27363780 DOI: 10.1039/c6sm00879h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Hydrogels formed by polypeptides could be much-favored tools for drug delivery because their main ingredients are generally biodegradable. However, the gelation of peptides in aqueous solution generally requires a minimal length of the peptide as well as distinct sequences of hydrophilic and hydrophobic residues. The aggregation of short peptides like tripeptides, which are relatively cheap and offer a high degree of biodegradability, are generally thought to require a high hydrophobicity of their residues. We found that contrary to this expectation cationic glycylalanylglycine in 55 mol% ethanol/45 mol% water forms a gel below a melting temperature of ca. 36 °C. A pure hydrogel state can be obtained after allowing the ethanol component to evaporate. The gel phase consists of crystalline fibrils of several 100 μm, which form a sample-spanning network. Rheological data reveal a soft elastic solid gel. We investigated the kinetics of the various processes that lead to the final gel state of the ternary mixture by a unique combination of UV circular dichroism, infrared, vibrational circular dichroism (VCD) and rheological measurements. A mathematical analysis of our data show that gelation is preceded by the formation of peptide β-sheet like tapes or ribbons, which give rise to a significant enhancement of the amide I' VCD signal, and the subsequent formation of rather thick and long fibrils. The VCD signals indicate that the tapes exhibit a right-handed helicity at temperatures above 16 °C and a left-handed helicity below. The tapes'/ribbons' helicity change occurs at a temperature where the UVCD data reflect a relatively long nucleation process. The kinetics of gel formation probed by the storage and loss moduli are composed of a fast process that follows tape/ribbon/fibril formation and is clearly identifiable in a movie that shows the gelation process and a slow process that causes an additional gel stabilization. The rheological data indicate that left-handed fibrils observed at low temperatures form a more solid-like structure than their right-handed counterparts formed at higher temperatures. Taken together our data reveal GAG as an unexpected gelator, the formation of which is underlied by a set of distinguishable kinetic processes.
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Affiliation(s)
- Stefanie Farrell
- Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA.
| | - David DiGuiseppi
- Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA.
| | - Nicolas Alvarez
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA
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22
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Almeida GG, Cordeiro JMM, Martín ME, Aguilar MA. Conformational Changes of the Alanine Dipeptide in Water–Ethanol Binary Mixtures. J Chem Theory Comput 2016; 12:1514-24. [DOI: 10.1021/acs.jctc.5b00952] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Glauco G. Almeida
- Faculdade de Engenharia,
Universidade Estadual Paulista “Julio de Mesquita Filho″, Ilha Solteira 15385-000, Brasil
| | - João M. M. Cordeiro
- Faculdade de Engenharia,
Universidade Estadual Paulista “Julio de Mesquita Filho″, Ilha Solteira 15385-000, Brasil
| | - M. Elena Martín
- Área
de Química Física, University of Extremadura, Avda.
Elvas s/n, Edif. José Ma Viguera
Lobo, 3a planta, Badajoz 06006, Spain
| | - Manuel A. Aguilar
- Área
de Química Física, University of Extremadura, Avda.
Elvas s/n, Edif. José Ma Viguera
Lobo, 3a planta, Badajoz 06006, Spain
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23
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Bhatia NK, Kishor S, Katyal N, Gogoi P, Narang P, Deep S. Effect of pH and temperature on conformational equilibria and aggregation behaviour of curcumin in aqueous binary mixtures of ethanol. RSC Adv 2016. [DOI: 10.1039/c6ra24256a] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Conformational equilibria of curcumin, a potential therapeutic agent, can be modulated by changing pH, temperature and solvent composition.
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Affiliation(s)
- Nidhi K. Bhatia
- Department of Chemistry
- Indian Institute of Technology
- Delhi
- India
| | | | - Nidhi Katyal
- Department of Chemistry
- Indian Institute of Technology
- Delhi
- India
| | - Pankaj Gogoi
- Department of Chemistry
- Indian Institute of Technology
- Delhi
- India
| | - Payal Narang
- Department of Chemistry
- Indian Institute of Technology
- Delhi
- India
| | - Shashank Deep
- Department of Chemistry
- Indian Institute of Technology
- Delhi
- India
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