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Zhang Y, Zhang L, Cai C, Zhang J, Lu P, Shi N, Zhu W, He N, Pan X, Wang T, Feng Z. In situ study of structural changes: Exploring the mechanism of protein corona transition from soft to hard. J Colloid Interface Sci 2024; 654:935-944. [PMID: 37898077 DOI: 10.1016/j.jcis.2023.10.095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Revised: 10/12/2023] [Accepted: 10/18/2023] [Indexed: 10/30/2023]
Abstract
HYPOTHESIS The process of protein corona changes has been widely believed to follow the Vroman effect, while protein structural change during the process is rarely reported, due to the lack of analytical methods. In-situ interpretation for protein structural change is critical to processes such as the recognition and transport of nanomaterials. EXPERIMENTS Molecular dynamics (MD) simulation was used to predict the deflection and twist of the protein tertiary structure. The structural changes of the surface protein corona during the interaction of nanoparticles (NPs) with lipid bilayer were probed in situ and real-time by sum frequency generation (SFG) spectroscopy. FINDINGS The ring tertiary structure of the protein corona is altered from vertical to horizontal on particle surface, a process of the soft-to-hard structural transition, which is contributed by the hydrogen bonding force between the protein and water molecules. The negatively charged protein corona can induce the redistribution of interfacial charge, leading to a more stable hydrogen bond network of the interfacial water. Our findings suggest that the structural change from flexible to rigid is a crucial process in the soft-to-hard transition of the protein corona, which will be a beneficial supplement to the Vroman effect of protein adsorption.
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Affiliation(s)
- Yixin Zhang
- State Key Laboratory of Bioelectronics, National Demonstration Center for Experimental Biomedical Engineering Education, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Liqiang Zhang
- State Key Laboratory of Bioelectronics, National Demonstration Center for Experimental Biomedical Engineering Education, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Chenglong Cai
- State Key Laboratory of Bioelectronics, National Demonstration Center for Experimental Biomedical Engineering Education, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Jixiang Zhang
- State Key Laboratory of Bioelectronics, National Demonstration Center for Experimental Biomedical Engineering Education, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Pengyu Lu
- State Key Laboratory of Bioelectronics, National Demonstration Center for Experimental Biomedical Engineering Education, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Neng Shi
- State Key Laboratory of Bioelectronics, National Demonstration Center for Experimental Biomedical Engineering Education, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Weiran Zhu
- SceneRay Co., Ltd., Suzhou 215123, China
| | - Nongyue He
- State Key Laboratory of Bioelectronics, National Demonstration Center for Experimental Biomedical Engineering Education, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Xuchao Pan
- Nanjing University of Science and Technology, Nanjing 210094, China.
| | - Ting Wang
- State Key Laboratory of Bioelectronics, National Demonstration Center for Experimental Biomedical Engineering Education, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China.
| | - Zhangqi Feng
- Nanjing University of Science and Technology, Nanjing 210094, China
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Mekawy M, Noguchi H, Kawakita J. Quantitative and qualitative studies for real monitoring of interfacial molecular water. J Colloid Interface Sci 2022; 613:311-319. [PMID: 35042031 DOI: 10.1016/j.jcis.2022.01.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/03/2022] [Accepted: 01/04/2022] [Indexed: 10/19/2022]
Abstract
HYPOTHESIS Interfacial water plays an essential role in natural phenomena and scientific applications despite causing many economic losses. Therefore, its real monitoring is no question mandatory; however, suitable techniques are quite rare and/or with limitations. EXPERIMENTS Moisture Sensor (MS) was used to detect the galvanic response current arising from the stacked interfacial water molecules between two dissimilar electrodes under controlled relative humidity (RH). Simultaneously, the frequency response was detected using QCM sensor as a quantitative tool. Bare and Hydrophilic (HP) sensor surfaces were used to examine the surface wettability. Moreover, sum frequency generation (SFG) was used to investigate the qualitative formation and the nature of stacked interfacial water molecules on bare and HP modified surfaces of quartz prism. FINDINGS Results revealed that, response current and frequency change were increased as the number of stacked water molecules increased. Correlating response current and frequency gave a clear quantitative estimation of stacked water molecules on the sensors' surfaces. Interfacial water molecules possessed strong H-bonding nature at the bare prism surface whereas, strong and weak H-bonding were existing at the HP/prism surface. Such findings provide feasible evaluation for the galvanic current source due to stacked interfacial water molecules at different levels of RH.
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Affiliation(s)
- Moataz Mekawy
- National Institute for Materials Science, 1-1, Namiki, Tsukuba-city 305-0044, Japan
| | - Hidenori Noguchi
- National Institute for Materials Science, 1-1, Namiki, Tsukuba-city 305-0044, Japan
| | - Jin Kawakita
- National Institute for Materials Science, 1-1, Namiki, Tsukuba-city 305-0044, Japan.
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Premadasa UI, Ma YZ, Sacci RL, Bocharova V, Thiele NA, Doughty B. Understanding Self-Assembly and the Stabilization of Liquid/Liquid Interfaces: The Importance of Ligand Tail Branching and Oil-Phase Solvation. J Colloid Interface Sci 2021; 609:807-814. [PMID: 34872722 DOI: 10.1016/j.jcis.2021.11.088] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 01/05/2023]
Abstract
HYPOTHESIS Organophosphorus-based ligands represent a versatile set of solvent extraction reagents whose chemical makeup plays an important role in extraction mechanism. We hypothesize that the branching of the extractant hydrophobic tail and its oil-phase solvation affect the liquid/liquid interfacial structure. Understanding the structure mediated adsorption and interfacial ordering becomes key in designing ligands with enhanced selectivity and efficiency for targeted extractions. EXPERIMENT We employed vibrational sum frequency generation spectroscopy and interfacial tension measurements to extract thermodynamic adsorption energies, map interfacial ordering, and rationalize disparate behaviors of model di-(2-ethylhexyl) phosphoric acid and dioctyl phosphoric acid ligands at the hexadecane water interface. FINDINGS With increased surface loading, ligands with branched hydrophobic tails formed stable interfaces at much lower concentrations than those observed for ligands with linear alkyl tails. The lack of an oil phase and associated solvation results in markedly different interfacial properties, and thus measurements made at air/liquid surfaces cannot be assumed to correlate with the processes occurring at buried liquid/liquid interfaces. We attribute these differences in the surface mediated self-assembly to key variations in hydrophobic interactions and tail solvation taking place in the oil phase demonstrating that interactions in both the polar and nonpolar phases are essential to understand self-assembly and function.
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Affiliation(s)
- Uvinduni I Premadasa
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Ying-Zhong Ma
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Robert L Sacci
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Vera Bocharova
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Nikki A Thiele
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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Xu B, Chen SL, Zhang Y, Li B, Yuan Q, Gan W. Evaluating the cross-membrane dynamics of a charged molecule on lipid films with different surface curvature. J Colloid Interface Sci 2021; 610:376-384. [PMID: 34923275 DOI: 10.1016/j.jcis.2021.12.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 11/27/2021] [Accepted: 12/04/2021] [Indexed: 11/25/2022]
Abstract
Does the curvature of a phospholipid membrane influence the permeability of the lipid bilayers? This is a question of great importance yet hard to answer. In this work the permeability of a positively charged rod like probing molecule (D289 dye) on the bilayers of DOPG lipid vesicles was investigated using angle resolved second harmonic generation method. It was revealed that the permeability of D289 on the surface of small vesicles with ∼ 100 nm diameter was notably lower than that on giant vesicles with ∼ 1000 nm diameter. With the increasing of temperature or the introducing of dimethyl sulfoxide (DMSO) in the solutions, the D289 permeability of the lipid bilayers was notably enhanced as expected, on both the small and the giant vesicles. Still, the D289 permeability of the lipid film with more curvature is lower than the relatively flat film in all these cases. This work demonstrated a general protocol for the investigating of surface permeability of lipid films with various curvature.
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Affiliation(s)
- Baomei Xu
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, and School of Science, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
| | - Shun-Li Chen
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Province, Shantou University, Shantou 515063, Guangdong, China
| | - Yiru Zhang
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, and School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, China
| | - Bifei Li
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, and School of Science, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
| | - Qunhui Yuan
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, and School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, China
| | - Wei Gan
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, and School of Science, Harbin Institute of Technology (Shenzhen), University Town, Shenzhen 518055, Guangdong, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China.
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Wang Z, Walter ED, Sassi M, Zhang X, Zhang H, Li XS, Chen Y, Cui W, Tuladhar A, Chase Z, Winkelman AD, Wang HF, Pearce CI, Clark SB, Rosso KM. The role of surface hydroxyls on the radiolysis of gibbsite and boehmite nanoplatelets. J Hazard Mater 2020; 398:122853. [PMID: 32768813 DOI: 10.1016/j.jhazmat.2020.122853] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 04/30/2020] [Accepted: 05/01/2020] [Indexed: 06/11/2023]
Abstract
Understanding mechanistic pathways to radiolytic hydrogen generation by metal oxyhydroxide nanomaterials is challenging because of the difficulties of distinguishing key locations of OH bond scission, from structural interiors to hydroxylated surfaces to physi-sorbed water molecules. Here we exploited the interface-selectivity of vibrational sum frequency generation (VSFG) to isolate surface versus bulk hydroxyl groups for gibbsite and boehmite nanoplatelets before and after 60Co irradiation at dose levels of approximately 7.0 and 29.6 Mrad. While high-resolution microscopy revealed no effect on particle bulk and surface structures, VSFG results clearly indicated up to 83% and 94% radiation-induced surface OH bond scission for gibbsite and boehmite, respectively, a substantially higher proportion than observed for interior OH groups by IR and Raman spectroscopy. Electron paramagnetic spectroscopy revealed that the major radiolysis products bound in the mineral structures are trapped electrons, O, O2- and possibly F-centers in gibbsite, and H, O and O3- in boehmite, which persist on the time frame of several months. The entrapped radiolysis products appear to be highly stable, enduring re-hydration of particle surfaces, and likely reflect a permanent adjustment in the thermodynamic stabilities of these nanomaterials.
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Affiliation(s)
- Zheming Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States.
| | - Eric D Walter
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Michel Sassi
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Xin Zhang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Hailin Zhang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Xiaohong S Li
- Energy and Environmental Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Ying Chen
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Wenwen Cui
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Aashish Tuladhar
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Zizwe Chase
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Austin D Winkelman
- Energy and Environmental Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, 220 Handan Road, Shanghai 200433, China
| | | | - Carolyn I Pearce
- Energy and Environmental Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Sue B Clark
- Energy and Environmental Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States; Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, 220 Handan Road, Shanghai 200433, China
| | - Kevin M Rosso
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
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Mizuguchi T, Nuriya M. Applications of second harmonic generation (SHG)/sum-frequency generation (SFG) imaging for biophysical characterization of the plasma membrane. Biophys Rev 2020; 12:10.1007/s12551-020-00768-4. [PMID: 33108561 PMCID: PMC7755958 DOI: 10.1007/s12551-020-00768-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Accepted: 10/20/2020] [Indexed: 12/12/2022] Open
Abstract
The plasma membrane is a lipid bilayer of < 10 nm width that separates intra- and extra-cellular environments and serves as the site of cell-cell communication, as well as communication between cells and the extracellular environment. As such, biophysical phenomena at and around the plasma membrane play key roles in determining cellular physiology and pathophysiology. Thus, the selective visualization and characterization of the plasma membrane are crucial aspects of research in wide areas of biology and medicine. However, the specific characterization of the plasma membrane has been a challenge using conventional imaging techniques, which are unable to effectively distinguish between signals arising from the plasma membrane and those from intracellular lipid structures. In this regard, interface-specific second harmonic generation (SHG) and sum-frequency generation (SFG) imaging demonstrate great potential. When combined with exogenous SHG/SFG active dyes, SHG/SFG can specifically highlight the plasma membrane as the most prominent interface associated with cells. Furthermore, SHG/SFG imaging can be readily extended to multimodal multiphoton microscopy with simultaneous occurrence of other multiphoton phenomena, including multiphoton excitation and coherent Raman scattering, which shed light on the biophysical properties of the plasma membrane from different perspectives. Here, we review traditional and current applications, as well as the prospects of long-known but unexplored SHG/SFG imaging techniques in biophysics, with special focus on their use in the biophysical characterization of the plasma membrane.
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Affiliation(s)
- Takaha Mizuguchi
- Department of Pharmacology School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Mutsuo Nuriya
- Department of Pharmacology School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012, Japan.
- Keio Advanced Research Center for Water Biology and Medicine, Keio University, 2-15-45 Mita, Minato-ku, Tokyo, 108-8345, Japan.
- Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya, Yokohama, Kanagawa, 240-8501, Japan.
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Boily JF, Fu L, Tuladhar A, Lu Z, Legg BA, Wang ZM, Wang H. Hydrogen bonding and molecular orientations across thin water films on sapphire. J Colloid Interface Sci 2019; 555:810-817. [PMID: 31425917 DOI: 10.1016/j.jcis.2019.08.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 08/07/2019] [Accepted: 08/08/2019] [Indexed: 01/28/2023]
Abstract
HYPOTHESIS Water vapor binding to metal oxide surfaces produces thin water films with properties controlled by interactions with surface hydroxo sites. Hydrogen bonding populations vary across films and induce different molecular orientations than at the surface of liquid water. Identifying these differences can open possibilities for tailoring film-mediated catalytic reactions by choice of the supporting metal oxide substrate. EXPERIMENTS The (0001) face of a single sapphire (α-Al2O3) sample exposed to water vapor and the surface of liquid water were probed by polarization dependent Sum Frequency Generation-Vibration Spectroscopy (SFG-VS). Molecular dynamics (MD) provided insight into the hydrogen bond populations and molecular orientations across films and liquid water. FINDINGS SFG-VS revealed a submonolayer film on sapphire exposed to 43% relative humidity (R.H.), and a multilayer film at 78% R.H. Polarization dependent SFG-VS spectra showed that median tilt angles of free OH bonds on the top of films are at ∼43° from the normal of the (0001) face but at 38° on neat liquid water. These values align with MD simulations, which also show that up to 36% of all OH bonds on films are free. This offers new means for understanding how interfacial reactions on sapphire-supported water films could contrast with those involving liquid water.
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Affiliation(s)
| | - Li Fu
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Aashish Tuladhar
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Zhou Lu
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Benjamin A Legg
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Zheming M Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Hongfei Wang
- Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200438, China
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8
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Huang W, Fu W, Li Y, Yang S. Specific ion binding interactions in potash flotation. J Colloid Interface Sci 2019; 553:418-426. [PMID: 31228756 DOI: 10.1016/j.jcis.2019.06.057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 06/08/2019] [Accepted: 06/16/2019] [Indexed: 10/26/2022]
Abstract
As the main resource of potash fertilizer, high grade of sylvite (KCl) is mainly separated from halite (NaCl) in soluble potash ores using flotation. An effective flotation collector determines the separation efficiency of sylvite. However, the collector adsorption mechanism is still the subject of much debate due to high ions concentration in the flotation pulp. This paper studies the hydration status of KCl, the flotation behavior of KCl and NaCl with lauric acid and the interfacial water structure of the soluble salts to provide further insights into the fundamental mechanisms at play. The contact angle measurements and laboratory micro-flotation experiments have shown that both the hydration status of KCl and the flotation soluble salts with lauric acid were dependent on the solution composition. Specifically, it was determined that the addition of Na-ions had an adverse effect on the hydrophobicity of KCl crystals. Both KCl and NaCl can be floated with lauric acid. However, flotation of NaCl is greatly enhanced with the addition of K-ions whereas the flotation of KCl is suppressed with the addition of Na-ions. Sum frequency generation (SFG) measurements have found, most strikingly, more disordered water molecules dominating the "structure maker" salt surfaces in a saturated NaCl solution. "Collins Concept" is employed to explain the specific ion binding behaviors in the flotation pulp.
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Affiliation(s)
- Wei Huang
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, Hubei 430070, China; School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Weng Fu
- School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Yubiao Li
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, Hubei 430070, China; State Key Laboratory of Mineral Processing, Beijing 102600, China.
| | - Siyuan Yang
- School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, Hubei 430070, China; State Key Laboratory of Mineral Processing, Beijing 102600, China; School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.
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Li X, Roiaz M, Pramhaas V, Rameshan C, Rupprechter G. Polarization-Dependent SFG Spectroscopy of Near Ambient Pressure CO Adsorption on Pt(111) and Pd(111) Revisited. Top Catal 2018; 61:751-762. [PMID: 29950796 PMCID: PMC6010505 DOI: 10.1007/s11244-018-0949-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polarization-dependent sum frequency generation (SFG) vibrational spectroscopy was employed to examine CO overlayers on Pt(111) and Pd(111) single crystal surfaces at room temperature. Utilizing different polarization combinations (SSP and PPP) of the visible and SFG light allows to determine the molecular orientation (tilt angle) of interface molecules but the analysis of the measured \documentclass[12pt]{minimal}
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\begin{document}$$I_{\text{ppp}}/I_{\text{ssp}}$$\end{document}Ippp/Issp is involved and requires a proper optical interface model. For CO/Pt(111), the hyperpolarizability ratio \documentclass[12pt]{minimal}
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\begin{document}$$\left( {R={\beta _{aac}}/{\beta _{ccc}}={\beta _{bbc}}/{\beta _{ccc}}} \right)$$\end{document}R=βaac/βccc=βbbc/βccc is not exactly known and varying R in the range 0.1–0.5 yields tilt angles of 40°–0°, respectively. Based on the known perpendicular adsorption of CO on Pt, an exact R-value of 0.49 was determined. Polarization-dependent SFG spectra in the pressure range 10−4 to 36 mbar did not indicate any change of the tilt angle of adsorbed CO. Modeling also indicated a strong dependence of \documentclass[12pt]{minimal}
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\begin{document}$${I_{{\text{ppp}}}}/{I_{{\text{ssp}}}}$$\end{document}Ippp/Issp on the incidence angles of visible and IR laser beams. Complementing previous low temperature/low pressure data, room temperature CO adsorption on Pd(111) was examined from 10−6 to 250 mbar. The absolute PPP and SSP spectral intensities on Pt and Pd were simulated, as well as the expected \documentclass[12pt]{minimal}
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\begin{document}$${I_{{\text{ppp}}}}/{I_{{\text{ssp}}}}$$\end{document}Ippp/Issp ratios. Although CO on Pt and Pd should exhibit similar intensities (at high CO coverage), the higher \documentclass[12pt]{minimal}
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\begin{document}$${I_{{\text{ppp}}}}/{I_{{\text{ssp}}}}$$\end{document}Ippp/Issp ratio for Pd (48 vs. 27 on Pt) renders the detection of adsorbed CO in SSP spectra difficult. The presence or absence of CO species in SSP spectra can thus not simply be correlated to tilted or perpendicular CO molecules, respectively. Careful modeling, including not only molecular and interface properties, but also the experimental configuration (incidence angles), is certainly required even for seemingly simple adsorbate–substrate systems.
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Affiliation(s)
- Xia Li
- Institute of Materials Chemistry, TU Wien, 1060 Vienna, Austria
| | - Matteo Roiaz
- Institute of Materials Chemistry, TU Wien, 1060 Vienna, Austria
| | - Verena Pramhaas
- Institute of Materials Chemistry, TU Wien, 1060 Vienna, Austria
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Soblosky L, Ramamoorthy A, Chen Z. Membrane interaction of antimicrobial peptides using E. coli lipid extract as model bacterial cell membranes and SFG spectroscopy. Chem Phys Lipids 2015; 187:20-33. [PMID: 25707312 DOI: 10.1016/j.chemphyslip.2015.02.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 02/17/2015] [Accepted: 02/18/2015] [Indexed: 12/17/2022]
Abstract
Supported lipid bilayers are used as a convenient model cell membrane system to study biologically important molecule-lipid interactions in situ. However, the lipid bilayer models are often simple and the acquired results with these models may not provide all pertinent information related to a real cell membrane. In this work, we use sum frequency generation (SFG) vibrational spectroscopy to study molecular-level interactions between the antimicrobial peptides (AMPs) MSI-594, ovispirin-1 G18, magainin 2 and a simple 1,2-dipalmitoyl-d62-sn-glycero-3-phosphoglycerol (dDPPG)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) bilayer. We compared such interactions to those between the AMPs and a more complex dDPPG/Escherichia coli (E. coli) polar lipid extract bilayer. We show that to fully understand more complex aspects of peptide-bilayer interaction, such as interaction kinetics, a heterogeneous lipid composition is required, such as the E. coli polar lipid extract. The discrepancy in peptide-bilayer interaction is likely due in part to the difference in bilayer charge between the two systems since highly negative charged lipids can promote more favorable electrostatic interactions between the peptide and lipid bilayer. Results presented in this paper indicate that more complex model bilayers are needed to accurately analyze peptide-cell membrane interactions and demonstrates the importance of using an appropriate lipid composition to study AMP interaction properties.
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Affiliation(s)
- Lauren Soblosky
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Zhan Chen
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; Biophysics, University of Michigan, Ann Arbor, MI 48109, USA.
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