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Islam MM, Nawagamuwage SU, Parshin IV, Richard MC, Burin AL, Rubtsov IV. Probing the Hydrophobic Region of a Lipid Bilayer at Specific Depths Using Vibrational Spectroscopy. J Am Chem Soc 2023; 145:26363-26373. [PMID: 37982703 DOI: 10.1021/jacs.3c10178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
A novel spectroscopic approach for studying the flexibility and mobility in the hydrophobic interior of lipid bilayers at specific depths is proposed. A set of test compounds featuring an azido moiety and a cyano or carboxylic acid moiety, connected by an alkyl chain of different lengths, was synthesized. FTIR data and molecular dynamics calculations indicated that the test compounds in a bilayer are oriented so that the cyano or carboxylic acid moiety is located in the lipid head-group region, while the azido group stays inside the bilayer at the depth determined by its alkyl chain length. We found that the asymmetric stretching mode of the azido group (νN3) can serve as a reporter of the membrane interior dynamics. FTIR and two-dimensional infrared (2DIR) studies were performed at different temperatures, ranging from 22 to 45 °C, covering the Lβ-Lα phase transition temperature of dipalmitoylphosphatidylcholine (∼41 °C). The width of the νN3 peak was found to be very sensitive to the phase transition and to the temperature in general. We introduced an order parameter, SN3, which characterizes restrictions to motion inside the bilayer. 2DIR spectra of νN3 showed different extents of inhomogeneity at different depths in the bilayer, with the smallest inhomogeneity in the middle of the leaflet. The spectral diffusion dynamics of the N3 peak was found to be dependent on the depth of the N3 group location in the bilayer. The obtained results enhance our understanding of the bilayer dynamics and can be extended to investigate membranes with more complex compositions.
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Affiliation(s)
- Md Muhaiminul Islam
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | | | - Igor V Parshin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Margaret C Richard
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Alexander L Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Igor V Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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Dynamics in tris(pentafluoroethyl)trifluorophosphate (FAP) anion based ionic liquids: A 2D-IR study with tungsten hexacarbonyl. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Recent progress of vibrational spectroscopic study on the interfacial structure of biomimetic membranes. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2021. [DOI: 10.1016/j.cjac.2021.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Abstract
Lipid membranes are more than just barriers between cell compartments; they provide molecular environments with a finely tuned balance between hydrophilic and hydrophobic interactions that enable proteins to dynamically fold and self-assemble to regulate biological function. Characterizing dynamics at the lipid-water interface is essential to understanding molecular complexities from the thermodynamics of liquid-liquid phase separation down to picosecond-scale reorganization of interfacial hydrogen-bond networks.Ultrafast vibrational spectroscopy, including two-dimensional infrared (2D IR) and vibrational sum-frequency generation (VSFG) spectroscopies, is a powerful tool to examine picosecond interfacial dynamics. Two-dimensional IR spectroscopy provides a bond-centered view of dynamics with subpicosecond time resolutions, as vibrational frequencies are highly sensitive to the local environment. Recently, 2D IR spectroscopy has been applied to carbonyl and phosphate vibrations intrinsically located at the lipid-water interface. Interface-specific VSFG spectroscopy probes the water vibrational modes directly, accessing H-bond strength and water organization at lipid headgroup positions. Signals in VSFG arise from the interfacial dipole contributions, directly probing headgroup ordering and water orientation to provide a structural view of the interface.In this Account we discuss novel applications of ultrafast spectroscopy to lipid membranes, a field that has experienced significant growth over the past decade. In particular, ultrafast experiments now offer a molecular perspective on increasingly complex membranes. The powerful combination of ultrafast, interface-selective spectroscopy and simulations opens up new routes to understanding multicomponent membranes and their function. This Account highlights key prevailing views that have emerged from recent experiments: (1) Water dynamics at the lipid-water interface are slow compared to those of bulk water as a result of disrupted H-bond networks near the headgroups. (2) Peptides, ions, osmolytes, and cosolvents perturb interfacial dynamics, indicating that dynamics at the interface are affected by bulk solvent dynamics and vice versa. (3) The interfacial environment is generally dictated by the headgroup structure and orientation, but hydrophobic interactions within the acyl chains also modulate interfacial dynamics. Ultrafast spectroscopy has been essential to characterizing the biophysical chemistry of the lipid-water interface; however, challenges remain in interpreting congested spectra as well as designing appropriate model systems to capture the complexity of a membrane environment.
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Affiliation(s)
- Jennifer C. Flanagan
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street Stop A5300, Austin, Texas 78712-1224, United States
| | - Mason L. Valentine
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street Stop A5300, Austin, Texas 78712-1224, United States
| | - Carlos R. Baiz
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street Stop A5300, Austin, Texas 78712-1224, United States
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Chen X, Cui Y, Gobeze HB, Kuroda DG. Assessing the Location of Ionic and Molecular Solutes in a Molecularly Heterogeneous and Nonionic Deep Eutectic Solvent. J Phys Chem B 2020; 124:4762-4773. [PMID: 32421342 PMCID: PMC7304071 DOI: 10.1021/acs.jpcb.0c02482] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
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Deep
eutectic solvents (DES) are emerging sustainable designer
solvents viewed as greener and better alternatives to ionic liquids.
Nonionic DESs possess unique properties such as viscosity and hydrophobicity
that make them desirable in microextraction applications such as oil-spill
remediation. This work builds upon a nonionic DES, NMA–LA DES,
previously designed by our group. The NMA–LA DES presents a
rich nanoscopic morphology that could be used to allocate solutes
of different polarities. In this work, the possibility of solvating
different solutes within the nanoscopically heterogeneous molecular
structure of the NMA–LA DES is investigated using ionic and
molecular solutes. In particular, the localized vibrational transitions
in these solutes are used as reporters of the DES molecular structure
via vibrational spectroscopy. The FTIR and 2DIR data suggest that
the ionic solute is confined in a polar and continuous domain formed
by NMA, clearly sensing the direct effect of the change in NMA concentration.
In the case of the molecular nonionic and polar solute, the data indicates
that the solute resides in the interface between the polar and nonpolar
domains. Finally, the results for the nonpolar and nonionic solute
(W(CO)6) are unexpected and less conclusive. Contrary to
its polarity, the data suggest that the W(CO)6 resides
within the NMA polar domain of the DES, probably by inducing a domain
restructuring in the solvent. However, the data are not conclusive
enough to discard the possibility that the restructuring comprises
not only the polar domain but also the interface. Overall, our results
demonstrate that the NMA–LA DES has nanoscopic domains with
affinity to particular molecular properties, such as polarity. Thus,
the presented results have a direct implication to separation science.
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Affiliation(s)
- Xiaobing Chen
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Yaowen Cui
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Habtom B Gobeze
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Daniel G Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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Gironi B, Lapini A, Ragnoni E, Calvagna C, Paolantoni M, Morresi A, Sassi P. Free volume and dynamics in a lipid bilayer. Phys Chem Chem Phys 2019; 21:23169-23178. [PMID: 31612182 DOI: 10.1039/c9cp03451j] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The lateral diffusion of lipids and of small molecules inside a membrane is strictly related to the arrangement of acyl chains and to their mobility. In this study, we use FTIR and time resolved 2D-IR spectroscopic techniques to characterize the structure and dynamics of the hydrophobic region of palmitoyl-oleylphosphatidylcholine/cholesterol vesicles dispersed in water/dimethylsulfoxide solutions. By means of a non-polar probe, hexacarbonyl tungsten, we monitor the distribution of free volumes inside the bilayer and the conformational dynamics of hydrophobic tails in relation to the different compositions of the membrane or the different compositions of the solvent. Despite the important structural changes induced by the presence of DMSO in the solvating medium, the picosecond dynamics of the membrane is preserved under the different conditions.
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Affiliation(s)
- Beatrice Gironi
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy.
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Kiefer LM, Kubarych KJ. Two-dimensional infrared spectroscopy of coordination complexes: From solvent dynamics to photocatalysis. Coord Chem Rev 2018. [DOI: 10.1016/j.ccr.2018.05.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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8
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Varner C, Zhou X, Saxman ZK, Leger JD, Jayawickramarajah J, Rubtsov IV. Azido alkanes as convenient reporters for mobility within lipid membranes. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.05.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Zang J, Feng M, Zhao J, Wang J. Micellar and bicontinuous microemulsion structures show different solute–solvent interactions: a case study using ultrafast nonlinear infrared spectroscopy. Phys Chem Chem Phys 2018; 20:19938-19949. [DOI: 10.1039/c8cp01024b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Using aqueous and organic probes to simultaneously explore the structural dynamics of reverse micellar and bicontinuous microemulsion structures.
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Affiliation(s)
- Jinger Zang
- Beijing National Laboratory for Molecular Sciences
- Molecular Reaction Dynamics Laboratory
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
| | - Minjun Feng
- Beijing National Laboratory for Molecular Sciences
- Molecular Reaction Dynamics Laboratory
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
| | - Juan Zhao
- Beijing National Laboratory for Molecular Sciences
- Molecular Reaction Dynamics Laboratory
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
| | - Jianping Wang
- Beijing National Laboratory for Molecular Sciences
- Molecular Reaction Dynamics Laboratory
- CAS Research/Education Center for Excellence in Molecular Sciences
- Institute of Chemistry
- Chinese Academy of Sciences
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Ricci M, Oliva R, Del Vecchio P, Paolantoni M, Morresi A, Sassi P. DMSO-induced perturbation of thermotropic properties of cholesterol-containing DPPC liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:3024-3031. [DOI: 10.1016/j.bbamem.2016.09.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 08/31/2016] [Accepted: 09/19/2016] [Indexed: 12/14/2022]
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12
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Abstract
Two-dimensional infrared (2D IR) spectroscopy has recently emerged as a powerful tool with applications in many areas of scientific research. The inherent high time resolution coupled with bond-specific spatial resolution of IR spectroscopy enable direct characterization of rapidly interconverting species and fast processes, even in complex systems found in chemistry and biology. In this minireview, we briefly outline the fundamental principles and experimental procedures of 2D IR spectroscopy. Using illustrative example studies, we explain the important features of 2D IR spectra and their capability to elucidate molecular structure and dynamics. Primarily, this minireview aims to convey the scope and potential of 2D IR spectroscopy by highlighting select examples of recent applications including the use of innate or introduced vibrational probes for the study of nucleic acids, peptides/proteins, and materials.
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Affiliation(s)
- Amanda L Le Sueur
- Department of Chemistry, Indiana University, Bloomington, Indiana, 47405, USA.
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