Vibrational exciton delocalization precludes the use of infrared intensities as proxies for surfactant accumulation on aqueous surfaces

Carter-Fenk, Kimberly A.; Carter-Fenk, Kevin; Fiamingo, Michelle; Allen, Heather C.; Herbert, John M.

doi:10.1039/d1sc01276b

Cited by 4 publications

(5 citation statements)

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“…It has been demonstrated that IRRAS band intensities are not expected to increase linearly with surface concentration due to exciton delocalization and the loss of many small bands in the IRRAS baseline. 34 As a result, and due to the potential impact of different cations on the interfacial structure of water, we have not attempted to use IRRAS in a quantitative way to compare the efficacy of different salts in driving AAs to the surface. Nevertheless, our data corroborate our π measurements by showing that AA peaks are enhanced in the presence of salts.…”

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confidence: 99%

“…A representative result is given in Figure where several (negative) peaks show greater intensity in the presence of 3 versus 0 m CaCl 2 . It has been demonstrated that IRRAS band intensities are not expected to increase linearly with surface concentration due to exciton delocalization and the loss of many small bands in the IRRAS baseline . As a result, and due to the potential impact of different cations on the interfacial structure of water, we have not attempted to use IRRAS in a quantitative way to compare the efficacy of different salts in driving AAs to the surface.…”

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confidence: 99%

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Amino Acids Are Driven to the Interface by Salts and Acidic Environments

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Nowak

Davasam

et al. 2022

J. Phys. Chem. Lett.

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Amino acids (AAs), the building blocks of proteins, are enriched by several orders of magnitude in sea spray aerosols compared to ocean waters. This suggests that AAs may reside at the air–water interface and be highly surface active. Using surface tension measurements, infrared reflection–absorption spectroscopy, and molecular dynamics simulations, we show that AAs are surface active and that salts and low-pH environments are drivers of surface activity. At typical sea spray salt concentrations and pH values, we determine that the surface coverage of hydrophobic AAs increases by approximately 1 order of magnitude. Additionally, divalent cations such as Ca2+ and Mg2+ can further increase AA surface propensity, particularly at neutral pH. Overall, these results indicate that AAs are likely to be found at increased concentrations at the surface of sea spray aerosols, where they can impact the cloud activation properties of the aerosol and enhance peptide formation under certain conditions.

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confidence: 99%

Amino Acids Are Driven to the Interface by Salts and Acidic Environments

Angle

Nowak

Davasam

et al. 2022

J. Phys. Chem. Lett.

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“…Only effects that occur at the surface can be observed, and trends can be analysed to improve samplepreparation methods. The explanation as to why they occur cannot be understood using standard cryo-EM experiments alone and requires complementary approaches such as infrared spectroscopy or dynamic surface-tension measurement studies (Carter-Fenk et al, 2021;Tang et al, 2020). Alternative approaches to sample preparation have been proposed in recent years to overcome the preferred orientation issue (Esfahani et al, 2024;Drulyte et al, 2018;Glaeser & Han, 2017;Jain et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

Factors affecting macromolecule orientations in thin films formed in cryo-EM

Yadav,

Vinothkumar

2024

Acta Cryst Sect D Struct Biol

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The formation of a vitrified thin film embedded with randomly oriented macromolecules is an essential prerequisite for cryogenic sample electron microscopy. Most commonly, this is achieved using the plunge-freeze method first described nearly 40 years ago. Although this is a robust method, the behaviour of different macromolecules shows great variation upon freezing and often needs to be optimized to obtain an isotropic, high-resolution reconstruction. For a macromolecule in such a film, the probability of encountering the air–water interface in the time between blotting and freezing and adopting preferred orientations is very high. 3D reconstruction using preferentially oriented particles often leads to anisotropic and uninterpretable maps. Currently, there are no general solutions to this prevalent issue, but several approaches largely focusing on sample preparation with the use of additives and novel grid modifications have been attempted. In this study, the effect of physical and chemical factors on the orientations of macromolecules was investigated through an analysis of selected well studied macromolecules, and important parameters that determine the behaviour of proteins on cryo-EM grids were revealed. These insights highlight the nature of the interactions that cause preferred orientations and can be utilized to systematically address orientation bias for any given macromolecule and to provide a framework to design small-molecule additives to enhance sample stability and behaviour.

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“…Only the effects that occur at the surface can be observed, and trends can be analysed to improve the sample preparation methods. The explanation as to why they occur cannot be understood using standard cryo-EM experiments alone and requires complementary approaches such as infrared spectroscopy or dynamic surface tension measurement studies (Carter-Fenk et al, 2021; F. Tang et al, 2020). Alternative approaches to sample preparation have been proposed in recent years to overcome the preferred orientation issue (Esfahani et al, 2024 ;Drulyte et al, 2018; Glaeser & Han, 2017; Jain et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Factors affecting macromolecule orientations in thin films formed in cryo-EM

Yadav,

Vinothkumar

2023

Preprint

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The formation of vitrified thin film embedded with randomly oriented macromolecules is an essential prerequisite for cryogenic sample electron microscopy. Most commonly, this is achieved using the plunge freeze method described nearly 40 years ago. Although this is a robust method, the behaviour of different macromolecules shows great variation upon freezing and often needs to be optimized to obtain an isotropic, high-resolution reconstruction. For a macromolecule in such a film, the probability of encountering the air-water interface in the time between blotting and freezing and adopting preferred orientations is very high. 3D reconstruction using preferentially oriented particles often leads to anisotropic and uninterpretable maps. Currently, there are no general solutions to this prevalent issue, but several approaches largely focusing on sample preparation with the use of additives and novel grid modifications have been attempted. In this study, through an analysis of selected well-studied macromolecules, the effect of physical and chemical factors on the orientations of macromolecules was investigated, and important parameters that determine the behaviour of proteins on cryo-EM grids were revealed. These insights highlight the nature of interactions that cause preferred orientations and can be utilized to systematically address orientation bias for any given macromolecule and provide a framework to design small-molecule additives to enhance sample stability and behaviour.

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Vibrational exciton delocalization precludes the use of infrared intensities as proxies for surfactant accumulation on aqueous surfaces

Abstract: Surface-sensitive vibrational spectroscopy is a common tool for measuring molecular organization and intermolecular interactions at interfaces. Peak intensity ratios are typically used to extract molecular information from one-dimensional spectra but...

Cited by 4 publications

References 71 publications

Amino Acids Are Driven to the Interface by Salts and Acidic Environments

Amino Acids Are Driven to the Interface by Salts and Acidic Environments

Factors affecting macromolecule orientations in thin films formed in cryo-EM

Factors affecting macromolecule orientations in thin films formed in cryo-EM

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