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Roeters SJ, Strunge K, Pedersen KB, Golbek TW, Bregnhøj M, Zhang Y, Wang Y, Dong M, Nielsen J, Otzen DE, Schiøtt B, Weidner T. Elevated concentrations cause upright alpha-synuclein conformation at lipid interfaces. Nat Commun 2023; 14:5731. [PMID: 37723164 PMCID: PMC10507035 DOI: 10.1038/s41467-023-39843-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 06/23/2023] [Indexed: 09/20/2023] Open
Abstract
The amyloid aggregation of α-synuclein (αS), related to Parkinson's disease, can be catalyzed by lipid membranes. Despite the importance of lipid surfaces, the 3D-structure and orientation of lipid-bound αS is still not known in detail. Here, we report interface-specific vibrational sum-frequency generation (VSFG) experiments that reveal how monomeric αS binds to an anionic lipid interface over a large range of αS-lipid ratios. To interpret the experimental data, we present a frame-selection method ("ViscaSelect") in which out-of-equilibrium molecular dynamics simulations are used to generate structural hypotheses that are compared to experimental amide-I spectra via excitonic spectral calculations. At low and physiological αS concentrations, we derive flat-lying helical structures as previously reported. However, at elevated and potentially disease-related concentrations, a transition to interface-protruding αS structures occurs. Such an upright conformation promotes lateral interactions between αS monomers and may explain how lipid membranes catalyze the formation of αS amyloids at elevated protein concentrations.
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Affiliation(s)
- Steven J Roeters
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
- Department of Anatomy and Neurosciences, Amsterdam UMC, Vrije Universiteit, De Boelelaan 1108, 1081 HZ, Amsterdam, The Netherlands.
| | - Kris Strunge
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Kasper B Pedersen
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Thaddeus W Golbek
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Mikkel Bregnhøj
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Yuge Zhang
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
| | - Yin Wang
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
| | - Mingdong Dong
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
| | - Janni Nielsen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
| | - Daniel E Otzen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
| | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
| | - Tobias Weidner
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
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Li B, Ma Y, Han X, Hu P, Lu X. Enhanced Sum Frequency Generation for Monolayers on Au Relative to Silica: Local Field Factors and SPR Effect. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:659-667. [PMID: 36580605 DOI: 10.1021/acs.langmuir.2c03016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Using metals as signal magnified substrates, surface plasmon-enhanced sum frequency generation (SFG) vibrational spectroscopy is a promising technique to probe weak molecular-level signals at surfaces and interfaces. In this study, the vibrational signals of the n-alkane monolayer on the gold (Au) and silica substrates are investigated using the broadband femtosecond SFG. The enhancement factors are discovered to be up to ∼1076 and ∼31 for the methyl symmetric and asymmetric stretching (ss and as) modes of the monolayer, respectively. By systematically analyzing the second-order nonlinear susceptibility tensor components (χijks), the Fresnel coefficients (Fijks), and the surface plasmon resonance (SPR) effect, we find that the interplay between Fijk and χijk terms and the SPR effect dominate the SFG signal enhancement. Our study reveals that the relative contributions of different influencing factors (i.e., Fresnel coefficients and SPR) to the SFG signal enhancement provide an approach to interpreting enhanced SFG vibrational signals detected from probe molecules on distinct substrates and may finally guide the design of the experimental methodology to improve the detection sensitivity and signal-to-noise ratio.
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Affiliation(s)
- Bolin Li
- Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory (HMFL), Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences, Hefei, Anhui230031, P. R. China
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing210096, China
| | - Yonghao Ma
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing210096, China
| | - Xiaofeng Han
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing210096, China
| | - Pengcheng Hu
- School of Medical Imaging, Xuzhou Medical College, Xuzhou, Jiangsu221004, China
| | - Xiaolin Lu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing210096, China
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3
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Han XF, Sun WH, Wang SJ, Lu XL. Sum frequency spectroscopy studies on cell membrane fusion induced by divalent cations. CHINESE J CHEM PHYS 2022. [DOI: 10.1063/1674-0068/cjcp2110213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cell membrane fusion is a fundamental biological process involved in a number of cellular living functions. Regarding this, divalent cations can induce fusion of the lipid bilayers through binding and bridging of divalent cations to the charged lipids, thus leading to the cell membrane fusion. How-ever, the elaborate mechanism of cell membrane fusion induced by divalent cations is still needed to be elucidated. Here, surface/interface sensitive sum frequency generation vibrational spectroscopy (SFG-VS) and dynamic light scattering (DLS) were applied in this research to study the responses of phospholipid monolayer to the exposure of divalent metal ions i.e. Ca2+ and Mg2+. According to the particle size distribution results measured by DLS experiments, it was found that Ca2+ could induce inter-vesicular fusion while Mg2+ could not. An octadecyltrichlorosilane self-assembled monolayer (OTS SAM)-lipid monolayer system was designed to model the cell membrane for the SFG-VS experiment. Ca2+ could interact with the lipid PO2− head groups more strongly, resulting in cell membrane fusion more easily, in comparison with Mg2+. No specific interaction between the two metal cations and the C=O groups was observed. However, the C=O orientations changed more after Ca2+-PO2− binding than Mg2+ mediation on lipid monolayer. Meanwhile, Ca2+ could induce dehydration of the lipids (which should be related to the strong Ca2+-PO2− interaction), leading to the reduced hindrance for cell membrane fusion.
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Affiliation(s)
- Xiao-feng Han
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, National Demonstration Center for Experimental, Biomedical Engineering Education, Southeast University, Nanjing 210096, China
| | - Wen-hua Sun
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, National Demonstration Center for Experimental, Biomedical Engineering Education, Southeast University, Nanjing 210096, China
| | - Shu-jing Wang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, National Demonstration Center for Experimental, Biomedical Engineering Education, Southeast University, Nanjing 210096, China
| | - Xiao-lin Lu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, National Demonstration Center for Experimental, Biomedical Engineering Education, Southeast University, Nanjing 210096, China
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Xu Z, Zhang Y, Wu Y, Lu X. Spectroscopically Detecting Molecular-Level Bonding Formation between an Epoxy Formula and Steel. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:13261-13271. [PMID: 36254887 DOI: 10.1021/acs.langmuir.2c02325] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The formation of the interfacial adhesion between an epoxy adhesive and a substrate was normally accompanied by the epoxy curing process on the substrate. Although the debate on the formation mechanism of the interfacial adhesion is still ongoing, this issue can causally be resolved by studying the interfacial structural formation between the epoxy adhesive and the substrate. Herein, to reveal the interfacial structural formation of a representative formula composed of epoxy (digylcidyl ether of biphenyl A, DGEBA) and amine hardener (2,2'-(ethylenedioxy) diethylamine, EDDA) with the steel substrate upon curing and postcuring treatments, sum-frequency generation (SFG) vibrational spectroscopy with a sandwiched transparent window/epoxy adhesive/steel setup was applied to detect and track the buried molecular-level structures at the epoxy adhesive/steel interface. An X-ray photoelectron spectroscopic (XPS) experiment was performed to probe the intentionally exposed interface to disclose the occurring interfacial chemical reaction. The reaction between the epoxy groups and the steel-surface OH groups and the molecular reconstruction of interfacial epoxy methyl groups upon curing and postcuring steps were confirmed. The latter also indirectly indicated the formation of the additional hydrogen bonding and the former bonding reaction at the interface. The above two spectroscopic experimental results matched up with the further examination of the adhesion strength. Therefore, this work elucidates the formation of the interfacial bonding between the epoxy formula and the steel substrate upon curing and postcuring treatments at the molecular level, thus providing an in-depth insight into the origin of the interfacial adhesion.
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Affiliation(s)
- Zhaohui Xu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing210096, China
| | - Yinyu Zhang
- Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang621900, China
| | - Yeping Wu
- Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang621900, China
| | - Xiaolin Lu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing210096, China
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Zhang S, Andre JS, Hsu L, Toolis A, Esarey SL, Li B, Chen Z. Nondestructive In Situ Detection of Chemical Reactions at the Buried Interface between Polyurethane and Isocyanate-Based Primer. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01862] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Shuqing Zhang
- Department of Macromolecular Science and Engineering, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - John S Andre
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Lorraine Hsu
- Coatings and Innovation Center, PPG, 4325 Rosanna Drive, Allison Park, Pennsylvania 15101, United States
| | - Amy Toolis
- Coatings and Innovation Center, PPG, 4325 Rosanna Drive, Allison Park, Pennsylvania 15101, United States
| | - Samuel L Esarey
- Coatings and Innovation Center, PPG, 4325 Rosanna Drive, Allison Park, Pennsylvania 15101, United States
| | - Bolin Li
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Zhan Chen
- Department of Macromolecular Science and Engineering, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
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6
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Li B, Andre JS, Chen X, Walther B, Paradkar R, Feng C, Tucker C, Mohler C, Chen Z. Probing Molecular Behavior of Carbonyl Groups at Buried Nylon/Polyolefin Interfaces in Situ. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:11349-11357. [PMID: 32870007 DOI: 10.1021/acs.langmuir.0c02188] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Nylon and maleic anhydride (MAH)-grafted polyolefin-based thin co-extruded multilayer films are widely used in packaging applications encountered in daily life. The molecular structure of the nylon/MAH-grafted polyolefin buried interface and molecular bonding between these two chemically dissimilar layers are thought to play an important role in achieving packaging structures with good adhesion. Here, the molecular bonds present at a nylon/maleic anhydride (MAH)-grafted polyethylene buried interface were systematically examined in situ for the first time using sum frequency generation (SFG) vibrational spectroscopy. The carbonyl stretching frequency region of the SFG spectra of a nylon/MAH-grafted polyethylene buried interface showed the presence of hydrolyzed MAH groups grafted to the polyethylene chain and very low levels of unreacted MAH enriched at the buried interface. The ability of SFG to detect these molecular species at the buried interface yields important understanding of the interfacial molecular structure and provides the basis for subsequent in situ studies of the bonding reaction between the grafted MAH and nylon directly at the interface. This understanding may guide the design of multilayer films with improved properties such as enhanced adhesion between polymer layers. The approach used in this study is general and is applicable to study the molecular characteristics of other buried interfaces of significance, such as buried interfaces involving polymers in solar cells, polymer semiconductors, and batteries. Nylon impact modification is another area of interest where the interaction between the MAH-grafted elastomer and the continuous phase of nylon is important.
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Affiliation(s)
- Bolin Li
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - John S Andre
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Xiaoyun Chen
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Brian Walther
- Packaging and Specialty Plastics, The Dow Chemical Company, Lake Jackson, Texas 77541, United States
| | - Rajesh Paradkar
- Packaging and Specialty Plastics, The Dow Chemical Company, Lake Jackson, Texas 77541, United States
| | - Chuang Feng
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Christopher Tucker
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Carol Mohler
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Zhan Chen
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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7
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Li B, Andre JS, Chen X, Walther B, Paradkar R, Feng C, Tucker C, Mohler C, Chen Z. Observing a Chemical Reaction at a Buried Solid/Solid Interface in Situ. Anal Chem 2020; 92:14145-14152. [DOI: 10.1021/acs.analchem.0c03228] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Bolin Li
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - John S. Andre
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Xiaoyun Chen
- Core R&D,The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Brian Walther
- Packaging and Specialty Plastics,The Dow Chemical Company, Lake Jackson, Texas 77566, United States
| | - Rajesh Paradkar
- Packaging and Specialty Plastics,The Dow Chemical Company, Lake Jackson, Texas 77566, United States
| | - Chuang Feng
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Christopher Tucker
- Core R&D,The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Carol Mohler
- Core R&D,The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Zhan Chen
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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8
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Zhang C, Gao J, Hankett J, Varanasi P, Borst J, Shirazi Y, Zhao S, Chen Z. Corn Oil-Water Separation: Interactions of Proteins and Surfactants at Corn Oil/Water Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:4044-4054. [PMID: 32212710 DOI: 10.1021/acs.langmuir.0c00338] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Purification and collection of industrial products from oil-water mixtures are commonly implemented processes. However, the efficiencies of such processes can be severely influenced by the presence of emulsifiers that induce the formation of small oil droplets dispersed in the mixtures. Understanding of this emulsifying effect and its counteractions which occur at the oil/water interface is therefore necessary for the improvement of designs of these processes. In this paper, we investigated the interfacial mechanisms of protein-induced emulsification and the opposing surfactant-induced demulsification related to corn oil refinement. At corn oil/water interfaces, the pH-dependent emulsifying function of zein protein, which is the major storage protein of corn, was elucidated by the surface/interface-sensitive sum frequency generation (SFG) vibrational spectroscopy technique. The effective stabilization of corn oil droplets by zein protein was illustrated and correlated to its ordered amide I group at the oil/water interface. Substantial decrease of this ordering with the addition of three industrial surfactants to corn oil-zein solution mixtures was also observed using SFG, which explains the surfactant-induced destabilization and coalescence of small oil droplets. Surfactant-protein interaction was then demonstrated to be the driving force for the disordering of interfacial proteins, either by disrupting protein layers or partially excluding protein molecules from the interface. The ordered zein proteins at the interface were therefore revealed to be the critical factor for the formation of corn oil-water emulsion.
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Affiliation(s)
- Chengcheng Zhang
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Jinpeng Gao
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Jeanne Hankett
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Prabodh Varanasi
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Joseph Borst
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Yaser Shirazi
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Shouxun Zhao
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Zhan Chen
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
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Wang C, Luo Y, Li X, Zhang F, Wang F, Han X, Wang T, Beke-Somfai T, Lu X. Revealing Molecular-Level Interaction between a Polymeric Drug and Model Membrane Via Sum Frequency Generation and Microfluidics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:1615-1622. [PMID: 31967838 DOI: 10.1021/acs.langmuir.9b03676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Body fluids flow all over the body and affect the biological processes at biointerfaces. To simulate such a case, sum frequency generation (SFG) vibrational spectroscopy and a self-designed microfluidic chip were combined together to investigate the interaction between a pH-responsive polymeric drug, poly(α-propylacrylic acid) (PPAAc), and the model cell membranes in different liquid environments. By examining the SFG spectra under the static and flowing conditions, the drug-membrane interaction was revealed comprehensively. The interfacial water layer was screened as the key factor affecting the drug-membrane interaction. The interfacial water layer can prevent the side propyl groups on PPAAc from inserting into the model cell membrane but would be disrupted by numerous ions in buffer solutions. Without flowing, at pH 6.6, the interaction between PPAAc and the model cell membrane was strongest; with flowing, at pH 5.8, the interaction was strongest. Flowing was proven to substantially affect the interaction between PPAAc and the model cell membranes, suggesting that the fluid environment was of key significance for biointerfaces. This work demonstrated that, by combining SFG and microfluidics, new information about the molecular-level interaction between macromolecules and the model cell membranes can be acquired, which cannot be obtained by collecting the normal static SFG spectra.
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Affiliation(s)
- Chu Wang
- Department of Biomedical Engineering , Southeast University , Jiangsu 210096 , China
| | - Yongsheng Luo
- Department of Biomedical Engineering , Southeast University , Jiangsu 210096 , China
| | - Xu Li
- Department of Biomedical Engineering , Southeast University , Jiangsu 210096 , China
| | - Furong Zhang
- Department of Biomedical Engineering , Southeast University , Jiangsu 210096 , China
| | - Feng Wang
- Department of Biomedical Engineering , Southeast University , Jiangsu 210096 , China
| | - Xiaofeng Han
- Department of Biomedical Engineering , Southeast University , Jiangsu 210096 , China
| | - Ting Wang
- Department of Biomedical Engineering , Southeast University , Jiangsu 210096 , China
| | - Tamás Beke-Somfai
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences , Hungarian Academy of Sciences , H-1117 Budapest , Hungary
| | - Xiaolin Lu
- Department of Biomedical Engineering , Southeast University , Jiangsu 210096 , China
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10
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High-resolution and high-repetition-rate vibrational sum-frequency generation spectroscopy of one- and two-component phosphatidylcholine monolayers. Anal Bioanal Chem 2019; 411:4861-4871. [DOI: 10.1007/s00216-019-01690-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Revised: 01/21/2019] [Accepted: 02/13/2019] [Indexed: 01/23/2023]
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11
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Hu P, Li X, Li B, Han X, Zhang F, Chou KC, Chen Z, Lu X. Molecular Coupling between Organic Molecules and Metal. J Phys Chem Lett 2018; 9:5167-5172. [PMID: 30141630 DOI: 10.1021/acs.jpclett.8b01765] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Molecular couplings at interfaces play important roles in determining the performance of nanophotonics and molecular electronics. In this Letter, using femtosecond sum frequency generation to trace free-induction decay of vibrationally excited aromatic thiol molecules immobilized on metal with and without the bridged methylene group(s), metal surface free electron-coupled and uncoupled phenyl C-H stretching vibrational modes were identified, with dephasing times of ∼0.28 and ∼0.60 ps, respectively. For thiols on Au with the bridged methylene group(s) (benzyl mercaptan and phenylethanethiol), both the coupled and uncoupled modes were observed; for thiol on Au without the bridged methylene group (thiophenol), only the coupled mode was observed. This indicates that the bridged methylene group(s) serving as a spacer can be used to adjust the molecular coupling between the phenyl vibration and surface free electrons. The experimental approach can be used to tune molecular couplings in advanced nanophotonics and molecular electronics.
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Affiliation(s)
- Pengcheng Hu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering , Southeast University , Nanjing 210096 , China
| | - Xu Li
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering , Southeast University , Nanjing 210096 , China
| | - Bolin Li
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering , Southeast University , Nanjing 210096 , China
| | - Xiaofeng Han
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering , Southeast University , Nanjing 210096 , China
| | - Furong Zhang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering , Southeast University , Nanjing 210096 , China
| | - Keng C Chou
- Department of Chemistry , University of British Columbia , Vancouver , BC , Canada V6T 1Z1
| | - Zhan Chen
- Department of Chemistry , University of Michigan , 930 North University Avenue , Ann Arbor , Michigan 48109 , United States
| | - Xiaolin Lu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering , Southeast University , Nanjing 210096 , China
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12
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Yesudas F, Mero M, Kneipp J, Heiner Z. Vibrational sum-frequency generation spectroscopy of lipid bilayers at repetition rates up to 100 kHz. J Chem Phys 2018; 148:104702. [PMID: 29544264 DOI: 10.1063/1.5016629] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Freeda Yesudas
- School of Analytical Sciences Adlershof, Humboldt Universität zu Berlin, Albert-Einstein-Str. 5-11, 12489 Berlin, Germany
- Department of Chemistry, Humboldt Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Mark Mero
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Str. 2a, 12489 Berlin, Germany
| | - Janina Kneipp
- School of Analytical Sciences Adlershof, Humboldt Universität zu Berlin, Albert-Einstein-Str. 5-11, 12489 Berlin, Germany
- Department of Chemistry, Humboldt Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Zsuzsanna Heiner
- School of Analytical Sciences Adlershof, Humboldt Universität zu Berlin, Albert-Einstein-Str. 5-11, 12489 Berlin, Germany
- Department of Chemistry, Humboldt Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany
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13
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Han X, Zheng J, Lin F, Kuroda K, Chen Z. Interactions between Surface-Immobilized Antimicrobial Peptides and Model Bacterial Cell Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:512-520. [PMID: 29232144 DOI: 10.1021/acs.langmuir.7b03411] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Sum frequency generation (SFG) vibrational spectroscopy was used to study surface immobilization effects on the interactions between antimicrobial peptide cecropin P1 (CP1) and model cell membranes. While free CP1 in solution interacted with a model cell membrane composed of a phosphatidylglycerol (PG) bilayer, electrostatic interaction led to the attachment of CP1 molecules onto the PG surface and the hydrophobic domain in the lipid bilayer enabled the peptides to insert into the bilayer and form α-helices from random coil structures. While CP1 molecules immobilized on a self-assembled monolayer interacted with PG lipid vesicles, the intensity of the SFG peak for the peptide α-helix decreased as the PG vesicle concentration increased. It was believed that when surface-immobilized CP1 molecules interacted with lipid vesicles, they lay down on the surface or became random coils. When the immobilized CP1 interacted with a PG lipid monolayer on water, the strong interaction led to the lying-down orientation of all of the surface-immobilized peptides as well. Differently, no significant interactions between surface-immobilized CP1 with the mammalian cell membrane model 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer were observed. Our results suggest that, instead of membrane insertion, the electrostatic interactions between the surface cationic charges of CP1 and anionic bacterial membranes may play an important role in the antimicrobial activity of the surface-immobilized CP1 peptide.
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Affiliation(s)
- Xiaofeng Han
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, National Demonstration Center for Experimental Biomedical Engineering Education, Southeast University , Nanjing 210096, China
| | - Jingguo Zheng
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, National Demonstration Center for Experimental Biomedical Engineering Education, Southeast University , Nanjing 210096, China
| | - Fengming Lin
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, National Demonstration Center for Experimental Biomedical Engineering Education, Southeast University , Nanjing 210096, China
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