Sum-frequency vibrational spectroscopic studies of Langmuir monolayers

Sung, Woongmo; Kim, Doseok; Shen, Y. R.

doi:10.1016/j.cap.2012.12.002

Cited by 55 publications

(49 citation statements)

References 120 publications

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“…According to the theory of surface sum-frequency generation, the intensity of SF output is determined as [12]:…”

Section: Sum-frequency Vibrational Spectroscopymentioning

confidence: 99%

“…Among the important issues concerning Langmuir monolayer are the conformation of molecules in the monolayer and its phase-transition behavior, and many experimental techniques such as X-ray diffraction/reflectivity [5,6], Brewster angle microscopy [7,8], ellipsometry [6,[8][9][10][11], and infrared reflection-absorption spectroscopy [9] have been employed to address these issues in the Langmuir monolayer system. As one of these techniques, sum-frequency generation (SFG) spectroscopy has proven to be the most promising and feasible technique to investigate the molecular conformation of the system [10,12,13] Based on the second-order nonlinear optical process which is not allowed in the system having inversion symmetry, SFG is a highly surface-sensitive probe to any light-accessible interface. It is also suitable to monitor the molecular conformation and structure because the sum-frequency response of each vibrational mode is an orientation average of specific moieties of the molecules in the system and changes sensitively with a subtle conformation change of the molecules [14].…”

Section: Introductionmentioning

confidence: 99%

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Two-Dimensional Correlation Analysis of Sum-Frequency Vibrational Spectra of Langmuir Monolayers

Lee¹,

Sung²,

Kim³

2014

Journal of the Optical Society of Korea

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Sum-frequency generation spectra of a Langmuir monolayer on water surface at varying surface areas were studied with two-dimensional correlation analysis. Upon enlarging the area/molecule of the Langmuir monolayer, the sum-frequency spectra changed reflecting the conformation change of the alkyl chains of the molecules in the monolayer. These changes stood out more clearly by employing two-dimensional correlation analysis of the above sum-frequency spectra. Features not very pronounced in the original spectra such as closely-spaced spectral bands can also be easily distinguished in the two-dimensional correlation spectra.

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“…According to the theory of surface sum-frequency generation, the intensity of SF output is determined as [12]:…”

Section: Sum-frequency Vibrational Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Correlation Analysis of Sum-Frequency Vibrational Spectra of Langmuir Monolayers

Lee¹,

Sung²,

Kim³

2014

Journal of the Optical Society of Korea

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“…Moreover, there is a direct thermodynamic relationship between bilayers and monolayers [126,127]. In addition, a large number of spectroscopic (UV-visible absorption [128][129][130][131][132][133][134], fluorescence [128,[131][132][133][134][135][136], and vibrational [137][138][139][140][141][142][143], (see [120,[144][145][146][147][148][149][150][151][152] for a review)), microscopic (Brewster angle [153,154] and fluorescence [155][156][157], (see [158][159][160][161][162][163][164] for a review)), and different additional physical methods [165][166][167]…”

Section: Monolayers As a Model Membrane To Study Hydrophobic Transmemmentioning

confidence: 99%

Comparison between the behavior of different hydrophobic peptides allowing membrane anchoring of proteins

Lhor¹,

Bernier²,

Horchani³

et al. 2014

Advances in Colloid and Interface Science

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Membrane binding of proteins such as short chain dehydrogenases reductases or tail-anchored proteins relies on their N-and/or C-terminal hydrophobic transmembrane segment. In this review, we propose guidelines to characterize such hydrophobic peptide segments using spectroscopic and biophysical measurements. The secondary structure content of the C-terminal peptides of retinol dehydrogenase 8, RGS9-1 anchor protein, lecithin retinol acyl transferase, and of the N-terminal peptide of retinol dehydrogenase 11 has been deduced by prediction tools from their primary sequence as well as by using infrared or circular dichroism analyses. Depending on the solvent and the solubilization method, significant structural differences were observed, often involving α-helices. The helical structure of these peptides was found to be consistent with their presumed membrane binding. Langmuir monolayers have been used as membrane models to study lipidpeptide interactions. The values of maximum insertion pressure obtained for all peptides using a monolayer of 1,2-dioleoyl-sn-glycero-3-phospho-ethanolamine (DOPE) are larger than the estimated lateral pressure of membranes, thus suggesting that they bind membranes. Polarization modulation infrared reflection absorption spectroscopy has been used to determine the structure and orientation of these peptides in the absence and in the presence of a DOPE monolayer. This lipid induced an increase or a decrease in the organization of the peptide secondary structure. Further measurements are necessary using other lipids to better understand the membrane interactions of these peptides.

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“…They attributed this behaviour to the trans -gauche conformational transformation, as discussed in Section 3.2.3. This behaviour is almost general for all surfactant adsorption layers (Bell et al, 1996;Sung et al, 2013), even at solidliquid interfaces (Bain, 1995). At high surface coverages, most of the adsorbed surfactants adopt an all-trans conformation to maximize their order and facilitate further surfactant adsorption for an optimal interfacial packing.…”

Section: Surface-active Organic Molecules At Fluid -Liquid Interfacementioning

confidence: 91%

“…lm α is the polarizability tensor and n μ  denotes the electric dipole operator for a particulate vibration, υ . Illustration of a methyl group with C 3v symmetry in the molecular coordinates (Sung et al, 2013). Blue coordinates exhibit the lab coordinates, and the green line is the C 3 rotation axes.…”

Section: This Correction Is Done Through the Fresnel Factors ( )mentioning

confidence: 99%

Molecular insights of adsorption and structure of surfactants and inorganic ions at fluid – liquid interfaces

Shahir¹

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Traditional approaches to studying fluid -liquid interfaces include the macroscopic measuring of interfacial properties such as surface tension and matching the collected data against adsorption models. This method is capable of producing valuable data about the thermodynamics of adsorption and has been widely used by the community to extract information about the adsorption of thousands of different surface-active molecules. Nonetheless, this methodology cannot produce any molecular-level information about the microscopic structure of adsorption layers and interfaces.As a result, the molecular origins of many interfacial phenomena remained unknown until the advent of surface-sensitive techniques such as computer simulation and non-linear spectroscopy.The new insights provided by these methods have challenged the traditional views about the origins of some interfacial phenomena and promise modification of classical theories which were developed to explain these phenomena.In general, this thesis aims to study the interfacial structure and adsorption of ionic surfactants, some surface-active alcohols as model nonionic surfactants including, n-pentanol, methyl isobutyl carbinol (MIBC) and n-hexanol and inorganic salts including LiCl, NaCl and CsCl at both microscopic and macroscopic levels. The employed methodology involves a combination of traditional adsorption modelling with some macroscopic measurements and sum frequency generation (SFG) spectroscopy, which is capable of distinguishing between bulk and interfacial molecules. Using SFG spectroscopy, the interfacial structure of adsorption layers and the composition of interfaces were investigated in detail and independently of the bulk solution.Specifically, the surface saturation of solutions of MIBC was identified directly using SFG spectroscopy and was then compared to equilibrium surface tension data to find that surface tension surprisingly continued to decrease even after full surface saturation. This is in contradiction to the traditional view that all surfactants adsorb at the outermost adsorption monolayer. Because of the limited surface area of the topmost adsorption monolayer, its full saturation is considered as the end of the adsorption process. This view is based on the notion of Gibbs dividing plane, which is usually taken as being equal to the physical adsorption monolayer in a surfactant solution. The postsaturation surface tension decrease, therefore, cannot be explained by the Gibbs convention. A different adsorption geometry, which considers the under-monolayer adsorption of alcohols, was proposed based on the Guggenheim extended interface model. In Chapter 5, a recent controversy about the applicability of the famous Gibbs adsorption isotherm to the analysis of surface tension data was addressed with regards to the new concept of under-monolayer adsorption. The results showed that the linearity of a surface tension plot is not necessarily indicative of a fully saturated ii surface. The same adsorption geometry was also proposed for t...

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Sum-frequency vibrational spectroscopic studies of Langmuir monolayers

Cited by 55 publications

References 120 publications

Two-Dimensional Correlation Analysis of Sum-Frequency Vibrational Spectra of Langmuir Monolayers

Two-Dimensional Correlation Analysis of Sum-Frequency Vibrational Spectra of Langmuir Monolayers

Comparison between the behavior of different hydrophobic peptides allowing membrane anchoring of proteins

Molecular insights of adsorption and structure of surfactants and inorganic ions at fluid – liquid interfaces

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