33 results on '"Ellen M. Adams"'
Search Results
2. Local Mutations Can Serve as a Game Changer for Global Protein Solvent Interaction
- Author
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Ellen M. Adams, Simone Pezzotti, Jonas Ahlers, Maximilian Rüttermann, Maxim Levin, Adi Goldenzweig, Yoav Peleg, Sarel J. Fleishman, Irit Sagi, and Martina Havenith
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Chemistry ,QD1-999 - Published
- 2021
- Full Text
- View/download PDF
3. Nonlinear TeraHertz Transmission by Liquid Water at 1 THz
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Fabio Novelli, Chun Yu Ma, Nidhi Adhlakha, Ellen M. Adams, Thorsten Ockelmann, Debasish Das Mahanta, Paola Di Pietro, Andrea Perucchi, and Martina Havenith
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terahertz ,nonlinear ,water ,solvation ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The solvation properties of liquid water originate from the transient network of hydrogen-bonded molecules. In order to probe the coupling between the different modes of this network, nonlinear terahertz (THz) spectroscopy techniques are required. Ideally, these techniques should use a minimal volume and capitalize on sensitive field-resolved detection. Here we performed open aperture z-scan transmission experiments on static liquid cells, and detect the THz fields with electro-optical techniques. We show that it is possible to quantify the nonlinear response of liquid water at ~1 THz even when large signals originate from the sample holder windows.
- Published
- 2020
- Full Text
- View/download PDF
4. Palmitic Acid on Salt Subphases and in Mixed Monolayers of Cerebrosides: Application to Atmospheric Aerosol Chemistry
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Ellen M. Adams and Heather C. Allen
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palmitic acid ,cerebroside ,aerosol ,Brewster angle microscopy ,sum frequency generation ,monolayers ,Meteorology. Climatology ,QC851-999 - Abstract
Palmitic acid (PA) has been found to be a major constituent in marine aerosols, and is commonly used to investigate organic containing atmospheric aerosols, and is therefore used here as a proxy system. Surface pressure-area isotherms (π-A), Brewster angle microscopy (BAM), and vibrational sum frequency generation (VSFG) were used to observe a PA monolayer during film compression on subphases of ultrapure water, CaCl2 and MgCl2 aqueous solutions, and artificial seawater (ASW). π-A isotherms indicate that salt subphases alter the phase behavior of PA, and BAM further reveals that a condensation of the monolayer occurs when compared to pure water. VSFG spectra and BAM images show that Mg2+ and Ca2+ induce ordering of the PA acyl chains, and it was determined that the interaction of Mg2+ with the monolayer is weaker than Ca2+. π-A isotherms and BAM were also used to monitor mixed monolayers of PA and cerebroside, a simple glycolipid. Results reveal that PA also has a condensing effect on the cerebroside monolayer. Thermodynamic analysis indicates that attractive interactions between the two components exist; this may be due to hydrogen bonding of the galactose and carbonyl headgroups. BAM images of the collapse structures show that mixed monolayers of PA and cerebroside are miscible at all surface pressures. These results suggest that the surface morphology of organic-coated aerosols is influenced by the chemical composition of the aqueous core and the organic film itself.
- Published
- 2013
- Full Text
- View/download PDF
5. Highly Altered State of Proton Transport in Acid Pools in Charged Reverse Micelles
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Hongxia Hao, Ellen M. Adams, Sarah Funke, Gerhard Schwaab, Martina Havenith, and Teresa Head-Gordon
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Ions ,Oscillation ,Colloid and Surface Chemistry ,Interfaces ,General Chemistry ,Counterions ,Biochemistry ,Micelles ,Catalysis - Abstract
Transport mechanisms of solvated protons of 1 M HCl acid pools, confined within reverse micelles (RMs) containing the negatively charged surfactant sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) or the positively charged cetyltrimethylammonium bromide (CTABr), are analyzed with reactive force field simulations to interpret dynamical signatures from TeraHertz absorption and dielectric relaxation spectroscopy. We find that the forward proton hopping events for NaAOT are further suppressed compared to a nonionic RM, while the Grotthuss mechanism ceases altogether for CTABr. We attribute the sluggish proton dynamics for both charged RMs as due to headgroup and counterion charges that expel hydronium and chloride ions from the interface and into the bulk interior, thereby increasing the pH of the acid pools relative to the nonionic RM. For charged NaAOT and CTABr RMs, the localization of hydronium near a counterion or conjugate base reduces the Eigen and Zundel configurations that enable forward hopping. Thus, localized oscillatory hopping dominates, an effect that is most extreme for CTABr in which the proton residence time increases dramatically such that even oscillatory hopping is slow.
- Published
- 2023
6. Non-Linear Elasticity and Short-Range Mechanical Coupling Govern the Rate and Symmetry of Mouth Opening in Hydra
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Tapan Goel, Ellen M. Adams, April Bialas, Cassidy M. Tran, Trevor Rowe, Sara Martin, Maia Chandler, Johanna Schubert, Patrick H. Diamond, and Eva-Maria Collins
- Published
- 2023
7. La3+ and Y3+ interactions with the carboxylic acid moiety at the liquid/vapor interface: Identification of binding complexes, charge reversal, and detection limits
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Robert W. Corkery, Sanghamitra Sengupta, Adrien Sthoer, Ellen M. Adams, Eric Tyrode, and Heather C. Allen
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chemistry.chemical_classification ,Carboxylic acid ,Inorganic chemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion speciation ,Biomaterials ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Deprotonation ,chemistry ,Monolayer ,Hydroxide ,Carboxylate ,Surface charge ,Absorption (chemistry) - Abstract
Specific interactions of yttrium and lanthanum ions with a fatty acid Langmuir monolayer were investigated using vibrational sum frequency spectroscopy. The trivalent ions were shown to interact with the charged form of the carboxylic acid group from nanomolar concentrations (
- Published
- 2022
8. Terahertz pump–probe of liquid water at 12.3 THz
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J. Michael Klopf, Martina Havenith, Fabio Novelli, Claudius Hoberg, and Ellen M. Adams
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Materials science ,Terahertz radiation ,Anharmonicity ,Physics::Optics ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Signal ,Molecular physics ,0104 chemical sciences ,13. Climate action ,Thermal ,Transient (oscillation) ,Physical and Theoretical Chemistry ,0210 nano-technology ,Anisotropy ,Spectroscopy ,Excitation - Abstract
The dynamical complexity of the hydrogen-bonded water network can be investigated with intense Terahertz (THz) spectroscopy, which can drive the liquid into the nonlinear response regime and probe anharmonicity effects. Here we report single-color and polarization-dependent pump–probe experiments at 12.3 THz on liquid water, exciting the librational mode. By comparing results obtained on a static sample and a free-flowing water jet, we are able to disentangle the distinct contributions by thermal, acoustic, and nonlinear optical effects. We show that the transient transmission by the static water layer on a time scale of hundreds of microseconds can be described by thermal (slow) and acoustic (temperature-dependent) effects. In addition, during pump probe overlap we observe an anisotropic nonlinear optical response. This nonlinear signal is more prominent in the liquid jet than in the static cell, where temperature and density perturbations are more pronounced. Our measurements confirm that the THz excitation resonates with the rotationally-damped motion of water molecules, resulting in enhanced transient anisotropy. This model can be used to explain the non-linear response of water in the frequency range between about 1 and 20 THz.
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- 2022
9. Observation of dissipating solvated protons upon hydrogel formation
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Eliane P. van Dam, Benedikt König, Sashary Ramos, Ellen M. Adams, Gerhard Schwaab, and Martina Havenith
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General Physics and Astronomy ,Water ,Hydrogels ,Hydrogen Bonding ,Physical and Theoretical Chemistry ,Protons ,Hyaluronic Acid - Abstract
Aqueous hyaluronan solutions form an elastic hydrogel within a narrow pH range, around pH 2.4, making this a model system to study the conformational changes of the hydrogen bond network upon gelation. This pH-dependent behavior allows us to probe water surrounding a biologically relevant molecule in different environments (liquid
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- 2022
10. Local Mutations Can Serve as a Game Changer for Global Protein Solvent Interaction
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Yoav Peleg, Simone Pezzotti, Sarel J. Fleishman, Ellen M. Adams, Martina Havenith, Irit Sagi, Maxim Levin, Maximilian Rüttermann, Adi Goldenzweig, and Jonas Ahlers
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matrix metalloproteinase ,Chemistry ,Protein design ,rational design ,Rational design ,Orders of magnitude (numbers) ,Article ,molecular dynamics ,Solvent ,Molecular dynamics ,local thermodynamics ,THz spectroscopy ,Biophysics ,Computational design ,Molecule ,solvation science ,Surface protein ,QD1-999 - Abstract
Although it is well-known that limited local mutations of enzymes, such as matrix metalloproteinases (MMPs), may change enzyme activity by orders of magnitude as well as its stability, the completely rational design of proteins is still challenging. These local changes alter the electrostatic potential and thus local electrostatic fields, which impacts the dynamics of water molecules close the protein surface. Here we show by a combined computational design, experimental, and molecular dynamics (MD) study that local mutations have not only a local but also a global effect on the solvent: In the specific case of the matrix metalloprotease MMP14, we found that the nature of local mutations, coupled with surface morphology, have the ability to influence large patches of the water hydrogen-bonding network at the protein surface, which is correlated with stability. The solvent contribution can be experimentally probed via terahertz (THz) spectroscopy, thus opening the door to the exciting perspective of rational protein design in which a systematic tuning of hydration water properties allows manipulation of protein stability and enzymatic activity.
- Published
- 2021
11. The key role of solvent in condensation: Mapping water in liquid-liquid phase-separated FUS
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Jonas Ahlers, Ellen M. Adams, Konstanze F. Winklhofer, Simone Pezzotti, Verian Bader, Jörg Tatzelt, and Martina Havenith
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0303 health sciences ,Aqueous solution ,Chemistry ,Hydrogen bond ,Amyotrophic Lateral Sclerosis ,Condensation ,Biophysics ,Water ,Articles ,DNA-Binding Proteins ,Solvent ,03 medical and health sciences ,0302 clinical medicine ,Protein Domains ,Chemical physics ,Phase (matter) ,Attenuated total reflection ,Solvents ,Side chain ,Humans ,RNA-Binding Protein FUS ,Dewetting ,030217 neurology & neurosurgery ,030304 developmental biology - Abstract
Formation of biomolecular condensates through liquid-liquid phase separation (LLPS) has emerged as a pervasive principle in cell biology, allowing compartmentalization and spatiotemporal regulation of dynamic cellular processes. Proteins that form condensates under physiological conditions often contain intrinsically disordered regions with low-complexity domains. Among them, the RNA-binding proteins FUS and TDP-43 have been a focus of intense investigation because aberrant condensation and aggregation of these proteins is linked to neurodegenerative diseases such as amyotrophic lateral sclerosis and frontotemporal dementia. LLPS occurs when protein-rich condensates form surrounded by a dilute aqueous solution. LLPS is per se entropically unfavorable. Energetically favorable multivalent protein-protein interactions are one important aspect to offset entropic costs. Another proposed aspect is the release of entropically unfavorable preordered hydration water into the bulk. We used attenuated total reflection spectroscopy in the terahertz frequency range to characterize the changes in the hydrogen bonding network accompanying the FUS enrichment in liquid-liquid phase-separated droplets to provide experimental evidence for the key role of the solvent as a thermodynamic driving force. The FUS concentration inside LLPS droplets was determined to be increased to 2.0 mM independent of the initial protein concentration (5 or 10 μM solutions) by fluorescence measurements. With terahertz spectroscopy, we revealed a dewetting of hydrophobic side chains in phase-separated FUS. Thus, the release of entropically unfavorable water populations into the bulk goes hand in hand with enthalpically favorable protein-protein interaction. Both changes are energetically favorable, and our study shows that both contribute to the thermodynamic driving force in phase separation.
- Published
- 2021
12. Reply to the 'Comment on 'Terahertz pump-probe of liquid water at 12.3 THz'' by A. F. G. van der Meer, PCCP, 2022, 24, D1CP05216K
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Fabio Novelli, Claudius Hoberg, Ellen M. Adams, J. Michael Klopf, and Martina Havenith
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General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
As outlined in our paper, we developed a model which is able to explain all recorded THz pump-probe data at 12.3 THz in the static water cell as well as in the liquid jet. The model includes an instantaneous temperature-dependent response by an acoustic phonon, an inherent non-linear response of water, and a slower thermal response. The order of magnitude of the non-linear contributions agrees with previous experimental results by us
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- 2022
13. Spectral signatures of excess-proton waiting and transfer-path dynamics
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Florian N. Brünig, Manuel Rammler, Ellen M. Adams, Martina Havenith, and Roland R. Netz
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Biophysics - Published
- 2023
14. Solvent dynamics play a decisive role in the complex formation of biologically relevant redox proteins
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Thomas Happe, Martina Havenith, Benedikt König, Oliver Lampret, and Ellen M. Adams
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Models, Molecular ,Static Electricity ,General Physics and Astronomy ,Plasma protein binding ,010402 general chemistry ,01 natural sciences ,Redox ,03 medical and health sciences ,Electron transfer ,Protein structure ,Molecular recognition ,Static electricity ,Physical and Theoretical Chemistry ,Protein Structure, Quaternary ,Ternary complex ,030304 developmental biology ,0303 health sciences ,Chemistry ,Spectrum Analysis ,Water ,0104 chemical sciences ,Ferredoxin-NADP Reductase ,Solvent ,Solvents ,Biophysics ,Ferredoxins ,Oxidation-Reduction ,Protein Binding - Abstract
Electron transfer processes between proteins are vital in many biological systems. Yet, the role of the solvent in influencing these redox reactions remains largely unknown. In this study, terahertz-time domain spectroscopy (THz-TDS) is used to probe the collective hydration dynamics of flavoenzyme ferredoxin-NADP+-reductase (FNR), electron transfer protein ferredoxin-1 (PetF), and the transient complex that results from their interaction. Results reveal changes in the sub-picosecond hydration dynamics that are dependent upon the surface electrostatic properties of the individual proteins and the transient complex. Retarded solvent dynamics of 8-9 ps are observed for FNR, PetF, and the FNR:PetF transient complex. Binding of the FNR:PetF complex to the substrate NADP+ results in bulk-like solvent dynamics of 7 ps, showing that formation of the ternary complex is entropically favored. Our THz measurements reveal that the electrostatic interaction of the protein surface with water results in charge sensitive changes in the solvent dynamics. Complex formation between the positively charged FNR:NADP+ pre-complex and the negatively charged PetF is not only entropically favored, but in addition the solvent reorganization into more bulk-like water assists the molecular recognition process. The change in hydration dynamics observed here suggests that the interaction with the solvent plays a significant role in mediating electron transfer processes between proteins.
- Published
- 2020
15. Proton Traffic Jam: Effect of Nanoconfinement and Acid Concentration on Proton Hopping Mechanism
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Teresa Head-Gordon, Maximilian Rüttermann, Itai Leven, Hongxia Hao, Hanna Wirtz, Ellen M. Adams, and Martina Havenith
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Proton ,Chemistry ,Force field (physics) ,micelles ,Organic Chemistry ,General Medicine ,General Chemistry ,Micelle ,Catalysis ,Ion ,Adsorption ,Chemical physics ,Atmospheric chemistry ,confined water ,THz spectroscopy ,Chemical Sciences ,Grotthuss mechanism ,Absorption (chemistry) ,proton hopping - Abstract
The properties of the water network in concentrated HCl acid pools in nanometer-sized reverse nonionic micelles were probed with TeraHertz absorption, dielectric relaxation spectroscopy, and reactive force field simulations capable of describing proton hopping mechanisms. We identify that only at a critical micelle size of W0 =9 do solvated proton complexes form in the water pool, accompanied by a change in mechanism from Grotthuss forward shuttling to one that favors local oscillatory hopping. This is due to a preference for H+ and Cl- ions to adsorb to the micelle interface, together with an acid concentration effect that causes a "traffic jam" in which the short-circuiting of the hydrogen-bonding motif of the hydronium ion decreases the forward hopping rate throughout the water interior even as the micelle size increases. These findings have implications for atmospheric chemistry, biochemical and biophysical environments, and energy materials, as transport of protons vital to these processes can be suppressed due to confinement, aggregation, and/or concentration.
- Published
- 2021
16. Spectral signatures of excess-proton waiting and transfer-path dynamics in aqueous hydrochloric acid solutions
- Author
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Florian N, Brünig, Manuel, Rammler, Ellen M, Adams, Martina, Havenith, and Roland R, Netz
- Abstract
The theoretical basis for linking spectral signatures of hydrated excess protons with microscopic proton-transfer mechanisms has so far relied on normal-mode analysis. We introduce trajectory-decomposition techniques to analyze the excess-proton dynamics in ab initio molecular-dynamics simulations of aqueous hydrochloric-acid solutions beyond the normal-mode scenario. We show that the actual proton transfer between two water molecules involves for relatively large water-water separations crossing of a free-energy barrier and thus is not a normal mode, rather it is characterized by two non-vibrational time scales: Firstly, the broadly distributed waiting time for transfer to occur with a mean value of 200-300 fs, which leads to a broad and weak shoulder in the absorption spectrum around 100 cm
- Published
- 2021
17. La
- Author
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Adrien, Sthoer, Ellen M, Adams, Sanghamitra, Sengupta, Robert W, Corkery, Heather C, Allen, and Eric C, Tyrode
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Ions ,Limit of Detection ,Carboxylic Acids ,Water ,Vibration - Abstract
Specific interactions of yttrium and lanthanum ions with a fatty acid Langmuir monolayer were investigated using vibrational sum frequency spectroscopy. The trivalent ions were shown to interact with the charged form of the carboxylic acid group from nanomolar concentrations (300 nM). Analysis of the spectral features from both the symmetric and the asymmetric carboxylate modes reveals the presence of at least three distinct coordination structures linked to specific binding configurations. Although the same species were identified for both La
- Published
- 2021
18. La3+ and Y3+ interactions with the carboxylic acid moiety at the liquid/vapour interface: identification of binding complexes, charge reversal, and detection limits
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Sanghamitra Sengupta, Heather C. Allen, Robert W. Corkery, Ellen M. Adams, Eric Tyrode, and Adrien Sthoer
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chemistry.chemical_classification ,chemistry.chemical_compound ,Deprotonation ,Chemistry ,Carboxylic acid ,Monolayer ,Inorganic chemistry ,Lanthanum ,Hydroxide ,chemistry.chemical_element ,Carboxylate ,Absorption (chemistry) ,Ion speciation - Abstract
Specific interactions of yttrium and lanthanum ions with a fatty acid Langmuir monolayer were investigated using vibrational sum frequency spectroscopy (VSFS). The trivalent ions were shown to interact with the charged form of the carboxylic acid group from nanomolar concentrations (
- Published
- 2021
19. Strong Anisotropy in Liquid Water upon Librational Excitation Using Terahertz Laser Fields
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N. Stavrias, Claudius Hoberg, Federico Sebastiani, Thorsten Ockelmann, Teresa Head-Gordon, Alejandro Colchero, Kochise Bennett, Gerhard Schwaab, Luis Ruiz Pestana, Martina Havenith, Ellen M. Adams, and Fabio Novelli
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Chemical Physics (physics.chem-ph) ,Materials science ,010304 chemical physics ,Field (physics) ,Terahertz radiation ,Far-infrared laser ,FOS: Physical sciences ,010402 general chemistry ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Molecular dynamics ,Orders of magnitude (time) ,Electric field ,Physics - Chemical Physics ,0103 physical sciences ,Materials Chemistry ,Physical and Theoretical Chemistry ,Anisotropy ,Excitation ,Optics (physics.optics) ,Physics - Optics ,FELIX - Free Electron Lasers for Infrared Experiments - Abstract
Tracking the excitation of water molecules in the homogeneous liquid is challenging due to the ultrafast dissipation of rotational excitation energy through the hydrogen-bonded network. Here we demonstrate strong transient anisotropy of liquid water through librational excitation using single-color pump-probe experiments at 12.3 THz. We deduce a third order response of chi^3 exceeding previously reported values in the optical range by three orders of magnitude. Using a theory that replaces the nonlinear response with a material response property amenable to molecular dynamics simulation, we show that the rotationally damped motion of water molecules in the librational band is resonantly driven at this frequency, which could explain the enhancement of the anisotropy in the liquid by the external Terahertz field. By addition of salt (MgSO4), the hydration water is instead dominated by the local electric field of the ions, resulting in reduction of water molecules that can be dynamically perturbed by THz pulses.
- Published
- 2020
20. Back Cover: Proton Traffic Jam: Effect of Nanoconfinement and Acid Concentration on Proton Hopping Mechanism (Angew. Chem. Int. Ed. 48/2021)
- Author
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Itai Leven, Hanna Wirtz, Maximilian Rüttermann, Ellen M. Adams, Teresa Head-Gordon, Martina Havenith, and Hongxia Hao
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Acid concentration ,Proton ,Chemistry ,INT ,Cover (algebra) ,General Chemistry ,Photochemistry ,Catalysis - Published
- 2021
21. Rücktitelbild: Proton Traffic Jam: Effect of Nanoconfinement and Acid Concentration on Proton Hopping Mechanism (Angew. Chem. 48/2021)
- Author
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Hongxia Hao, Teresa Head-Gordon, Itai Leven, Hanna Wirtz, Maximilian Rüttermann, Ellen M. Adams, and Martina Havenith
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Acid concentration ,Proton ,Chemistry ,General Medicine ,Photochemistry ,Mechanism (sociology) - Published
- 2021
22. Surface organization of a DPPC monolayer on concentrated SrCl2 and ZnCl2 solutions
- Author
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Richard E. Cochran, Ellen M. Adams, Heather C. Allen, Elizabeth A. Stone, Dominique Verreault, and Thilina Jayarathne
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inorganic chemicals ,chemistry.chemical_classification ,Brewster's angle ,Aqueous solution ,Analytical chemistry ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,Crystallography ,chemistry.chemical_compound ,chemistry ,Transition metal ,Dipalmitoylphosphatidylcholine ,Phase (matter) ,Monolayer ,symbols ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Alkyl - Abstract
Transition metals are known to be enriched in organic-coated marine aerosols, but the impact these cations have on their surface properties is not well understood. Here the effect of Zn2+ enrichment on the surface properties of a dipalmitoylphosphatidylcholine (DPPC) monolayer was investigated and compared to that of the alkaline earth metal Sr2+, an ion not enriched in aerosols. Phase behavior of the DPPC film on concentrated aqueous solutions was probed with surface pressure–area isotherms while domain morphology was monitored with Brewster angle microscopy (BAM). Infrared reflection–absorption spectroscopy (IRRAS) and vibrational sum frequency generation (VSFG) spectroscopy were used to assess the impact of cations on the conformation and orientation of alkyl chains as well as the hydration state of the carbonyl and phosphatidylcholine (PC) moieties. Results of compression isotherms and BAM show that Zn2+ strongly interacts with DPPC molecules, and induces condensation of the monolayer while Sr2+ only weakly interacts with the monolayer in expanded phases. Conformational order and orientation of alkyl chains in the condensed phase are not significantly altered by either cation. IRRAS indicates that Sr2+ has weak interactions with the PC headgroup. Zn2+ ions cause dehydration of carbonyl groups and binds to the phosphate group in a 2 : 1 bridging complex. Findings here suggest that Sr2+ is not enriched in aerosols because it behaves similar to a monovalent ion and only weakly interacts with the monolayer, while enrichment of Zn2+ is due to strong binding to the lipid film.
- Published
- 2016
23. Interfacial properties of avian stratum corneum monolayers investigated by Brewster angle microscopy and vibrational sum frequency generation
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Alex M. Champagne, Joseph B. Williams, Ellen M. Adams, and Heather C. Allen
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Langmuir ,Morphology (linguistics) ,Surface Properties ,Population ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Miscibility ,Vibration ,symbols.namesake ,Monolayer ,Stratum corneum ,medicine ,Molecule ,Animals ,Passeriformes ,education ,Molecular Biology ,education.field_of_study ,Microscopy ,Brewster's angle ,Chemistry ,Organic Chemistry ,Water ,Cell Biology ,021001 nanoscience & nanotechnology ,Lipid Metabolism ,Lipids ,0104 chemical sciences ,Crystallography ,medicine.anatomical_structure ,symbols ,Epidermis ,0210 nano-technology - Abstract
The outermost layer of skin, the stratum corneum (SC), contains a complex mixture of lipids, which controls the rate of cutaneous water loss (CWL) in reptiles, mammals, and birds. However, the molecular structure of SC lipids and how molecular configurations influence CWL is poorly understood. Here, the organization and structure of SC lipids extracted from birds were investigated by means of Langmuir films. Properties of lipids from the SC of arid and semi-arid adapted larks, known to have a low CWL, were compared with lipids extracted from the SC of mesic lark species with higher CWL to gain insight into how structure impacts CWL. Film properties were probed with surface pressure-area isotherms, Brewster angle microscopy (BAM), and vibrational sum frequency generation (VSFG). Results indicate organization and ordering of SC lipids in the arid-adapted hoopoe lark was vastly different from all other species, forming a miscible, rigid monolayer, whereas monolayers from semi-arid and mesic species were immiscible and disordered. Probing of interfacial water structure reveals that film morphology determines organization of water molecules near the monolayer; monolayers with a porous morphology had an increased population of water molecules that are weakly hydrogen-bonded. In general, CWL appears related to the miscibility and ordering of lipid components within the SC, as well as the ability of these lipids to interact with water molecules. From a broader perspective, CWL in larks appears linked to both the SC lipid composition and the aridity of the species' environment.
- Published
- 2017
24. Sodium-carboxylate contact ion pair formation induces stabilization of palmitic acid monolayers at high pH
- Author
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Bethany A. Wellen, Sandeep K. Reddy, Raphael Thiraux, Andrew S. Vidalis, Ellen M. Adams, Francesco Paesani, and Heather C. Allen
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chemistry.chemical_classification ,Aqueous solution ,Sodium ,General Physics and Astronomy ,chemistry.chemical_element ,Salt (chemistry) ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Palmitic acid ,chemistry.chemical_compound ,chemistry ,Desorption ,Monolayer ,Organic chemistry ,Carboxylate ,Physical and Theoretical Chemistry ,0210 nano-technology ,Alkyl - Abstract
Sea spray aerosols (SSA) are known to have an organic coating that is mainly composed of fatty acids. In this study, the effect of pH and salt on the stability and organization of a palmitic acid (PA) monolayer is investigated by surface vibrational spectroscopy and molecular dynamics simulations. Results indicate that alkyl chain packing becomes more disordered as the carboxylic headgroup becomes deprotonated. This is associated with packing mismatch of charged and neutral species as charged headgroups penetrate deeper into the solution phase. At pH 10.7, when the monolayer is ∼99% deprotonated, palmitate (PA-) molecules desorb and solubilize into the bulk solution where there is spectroscopic evidence for aggregate formation. Yet, addition of 100 mM NaCl to the bulk solution is found to drive PA- molecules to the aqueous surface. Free energy calculations show that PA- molecules become stabilized within the interface with increasing NaCl concentration. Formation of contact -COO-:Na+ pairs alters the hydration state of PA- headgroups, thus increasing the surface propensity. As salts are highly concentrated in SSA, these results suggest that deprotonated fatty acids may be found at the air-aqueous interface of aerosol particles due to sea salt's role in surface stabilization.
- Published
- 2017
25. Surface organization of a DPPC monolayer on concentrated SrCl
- Author
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Ellen M, Adams, Dominique, Verreault, Thilina, Jayarathne, Richard E, Cochran, Elizabeth A, Stone, and Heather C, Allen
- Abstract
Transition metals are known to be enriched in organic-coated marine aerosols, but the impact these cations have on their surface properties is not well understood. Here the effect of Zn
- Published
- 2016
26. Impact of Salt Purity on Interfacial Water Organization Revealed by Conventional and Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy
- Author
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Zishuai Huang, Wei Hua, Dominique Verreault, Heather C. Allen, and Ellen M. Adams
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chemistry.chemical_classification ,Aqueous solution ,Sum-frequency generation ,Analytical chemistry ,Salt (chemistry) ,Infrared spectroscopy ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,General Energy ,chemistry ,Impurity ,law ,Physical and Theoretical Chemistry ,Spectroscopy ,Filtration ,Sum frequency generation spectroscopy - Abstract
Water organization and ion distribution at air/aqueous interfaces investigated by nonlinear vibrational spectroscopy as well as by other surface-sensitive techniques depend critically on the purity grade and purification processing of the chosen salts and their solutions. This is true not only for the ACS grade salts but also for the ultrapure (UP) grade, even though both have
- Published
- 2013
27. Effect of cation enrichment on dipalmitoylphosphatidylcholine (DPPC) monolayers at the air-water interface
- Author
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Clayton B. Casper, Ellen M. Adams, and Heather C. Allen
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Langmuir ,Analytical chemistry ,Salt (chemistry) ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Biomaterials ,chemistry.chemical_compound ,symbols.namesake ,Colloid and Surface Chemistry ,Phase (matter) ,Monolayer ,Moiety ,Alkyl ,chemistry.chemical_classification ,Brewster's angle ,technology, industry, and agriculture ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,chemistry ,Dipalmitoylphosphatidylcholine ,symbols ,lipids (amino acids, peptides, and proteins) ,0210 nano-technology - Abstract
The effect of highly concentrated salt solutions of marine-relevant cations (Na(+), K(+), Mg(2+), and Ca(2+)) on Langmuir monolayers of dipalmitoylphosphatidylcholine (DPPC) was investigated by means of surface pressure-area isotherms, Brewster angle microscopy (BAM), and infrared reflection-absorption spectroscopy (IRRAS). It was found that monovalent cations and Mg(2+) have similar phase behavior, causing DPPC monolayers to expand, while Ca(2+) induces condensation. All cations disrupted the surface morphology at high cation concentration, resulting in decreased reflectivity from the monolayer. Monolayer refractive index was calculated from BAM image intensity in the liquid condensed phase and decreased with increasing cation concentration, which suggests that orientation of the alkyl chains change. Monovalent ions increase ordering of the alkyl chains, more than divalents, yet have little interaction with the DPPC headgroup. Mg(2+) induces gauche defects in the alkyl chain and increases headgroup hydration at low lipid coverage but increases chain ordering and dehydrates the headgroup at high lipid coverage. Ca(2+) orders alkyl chains and dehydrates the phosphate moiety, independent of lipid phase. At the highest salt concentration investigated, significant narrowing of the asymmetric PO2(-) vibrational mode occurs and is attributed to considerable dehydration of the DPPC headgroup.
- Published
- 2016
28. Surface Potential of DPPC Monolayers on Concentrated Aqueous Salt Solutions
- Author
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Clayton B. Casper, Wei Hua, Ellen M. Adams, Heather C. Allen, and Dominique Verreault
- Subjects
chemistry.chemical_classification ,Cation binding ,Aqueous solution ,Chemistry ,Inorganic chemistry ,Salt (chemistry) ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Sea surface microlayer ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Phase (matter) ,Dipalmitoylphosphatidylcholine ,Monolayer ,Materials Chemistry ,Cloud condensation nuclei ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The presence and exchange of electrical charges on the surfaces of marine aerosols influence their ability to act as cloud condensation nuclei and play a role in thundercloud electrification. Although interactions exist between surface-active inorganic ions and organic compounds, their role in surface charging of marine aerosols is not well understood. In this study, the surface potential of dipalmitoylphosphatidylcholine (DPPC) monolayers, a zwitterionic phospholipid found in the sea surface microlayer, is measured on concentrated (0.3-2.0 M) chloride salt solutions containing marine-relevant cations (Na(+), K(+), Mg(2+), Ca(2+)) to model and elucidate the electrical properties of organic-covered marine aerosols. Monovalent cations show only a weak effect on the surface potential of DPPC monolayers in the condensed phase compared to water. In contrast, Mg(2+) and Ca(2+) increase the surface potential, indicating different cation binding modes and affinities for the PC headgroup. Moreover, it is found that for divalent chloride salt solutions, the PC headgroup and interfacial water molecules make the largest dipolar contribution to the surface potential. This study shows that for equal charge concentrations, divalent cations impact surface potential of DPPC monolayers more strongly than monovalents likely through changes in the PC headgroup orientation induced by their complexation along with the lesser ordering of interfacial water molecules caused by phosphate group charge screening.
- Published
- 2016
29. Hydrophobic Collapse of a Stearic Acid Film by Adsorbed <scp>l</scp>-Phenylalanine at the Air–Water Interface
- Author
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Veronica Vaida, Heather C. Allen, Elizabeth C. Griffith, and Ellen M. Adams
- Subjects
Surface Properties ,Air ,Phenylalanine ,Water ,food and beverages ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Crystallography ,Adsorption ,Pulmonary surfactant ,chemistry ,Chemical engineering ,Phase (matter) ,Monolayer ,Materials Chemistry ,Particle ,Stearic acid ,Surface layer ,Particle Size ,Physical and Theoretical Chemistry ,Hydrophobic collapse ,Hydrophobic and Hydrophilic Interactions ,Stearic Acids - Abstract
The surface morphology of atmospheric aerosol particles can influence the particle's overall effect on climate through enhancing or impeding its ability to uptake and evaporate water. In the work presented here, complementary surface-sensitive information from π-A isotherms, Brewster angle microscopy (BAM), and infrared reflection-absorption spectroscopy (IRRAS) are used to monitor the induced hydrophobic collapse of a surfactant film by an adsorbed amino acid at the air-water interface. The stearic acid film studied here is well-known to form a very stable floating monolayer at the air-water interface, and is shown in this work to withstand isotherm compression-expansion cycles without any premature collapse. With the presence of the water-soluble amino acid l-phenylalanine, however, significant disruption is observed of the stearic acid film, evidenced by the disappearance of its liquid-condensed phase from the isotherm cycles, as well as premature collapse structures observed in the BAM images and a change in intensity in stearic acid's C-H stretching region in the IRRAS spectra. Throughout this process, the surface layer is transformed from a homogeneous hydrophobic surface to an inhomogeneous surface with three-dimensional hydrophobic aggregates as well as hydrophilic "holes" with minimum surfactant coverage.
- Published
- 2012
30. Interaction of L-Phenylalanine with a Phospholipid Monolayer at the Water-Air Interface
- Author
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Elizabeth C. Griffith, Russell J. Perkins, Martina Roeselová, Veronica Vaida, Heather C. Allen, Ellen M. Adams, Lukasz Cwiklik, and Dana-Marie Telesford
- Subjects
1,2-Dipalmitoylphosphatidylcholine ,Surface Properties ,Phenylalanine ,Intercalation (chemistry) ,Analytical chemistry ,Context (language use) ,Molecular Dynamics Simulation ,Surface tension ,Molecular dynamics ,symbols.namesake ,Monolayer ,Microscopy ,Materials Chemistry ,Physical and Theoretical Chemistry ,Brewster's angle ,Molecular Structure ,Chemistry ,Air ,technology, industry, and agriculture ,Aqueous two-phase system ,Water ,Deuterium ,Surfaces, Coatings and Films ,Chemical physics ,symbols ,lipids (amino acids, peptides, and proteins) - Abstract
The interaction of l-phenylalanine with a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer at the air–water interface was explored using a combination of experimental techniques and molecular dynamics (MD) simulations. By means of Langmuir trough methods and Brewster angle microscopy, l-phenylalanine was shown to significantly alter the interfacial tension and the surface domain morphology of the DPPC film. In addition, confocal microscopy was used to explore the aggregation state of l-phenylalanine in the bulk aqueous phase. Finally, MD simulations were performed to gain molecular-level information on the interactions of l-phenylalanine and DPPC at the interface. Taken together, these results show that l-phenylalanine intercalates into a DPPC film at the air–water interface, thereby affecting the surface tension, phase morphology, and ordering of the DPPC film. The results are discussed in the context of biological systems and the mechanism of diseases such as phenylketonuria.
- Published
- 2014
31. Cation effects on interfacial water organization of aqueous chloride solutions. I. Monovalent cations: Li+, Na+, K+, and NH4(+)
- Author
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Ellen M. Adams, Heather C. Allen, Wei Hua, Dominique Verreault, and Zishuai Huang
- Subjects
inorganic chemicals ,Double layer (biology) ,chemistry.chemical_classification ,Aqueous solution ,Chemistry ,Inorganic chemistry ,Analytical chemistry ,Ionic bonding ,Salt (chemistry) ,Alkali metal ,Chloride ,Surfaces, Coatings and Films ,Ion ,chemistry.chemical_compound ,Materials Chemistry ,medicine ,Ammonium chloride ,Physical and Theoretical Chemistry ,medicine.drug - Abstract
The influence of monovalent cations on the interfacial water organization of alkali (LiCl, NaCl, and KCl) and ammonium chloride (NH4Cl) salt solutions was investigated using surface-sensitive conventional vibrational sum frequency generation (VSFG) and heterodyne-detected (HD-)VSFG spectroscopy. It was found in the conventional VSFG spectra that LiCl and NH4Cl significantly perturb water’s hydrogen-bonding network. In contrast, NaCl and KCl had little effect on the interfacial water structure and exhibited weak concentration dependency. The Im χs(2)(ωIR) spectra from HD-VSFG further revealed that, for all chloride solutions, the net transition dipole moments of hydrogen-bonded water molecules (O → H) are oriented more toward the vapor phase relative to neat water. This suggests the presence of an interfacial electric field generated from the formation of an ionic double layer in the interfacial region with a distribution of Cl(-) ions located above the countercations, in agreement with predictions from MD simulations. The magnitude of this electric field shows a small but definite cation specificity and follows the order Li(+) ≈ Na(+)NH4(+)K(+). The observed trend was found to be in good agreement with previously published surface potential data.
- Published
- 2014
32. Medical Secretary's Manual
- Author
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Ellen M. Adams
- Subjects
Background information ,Phrase ,Index (publishing) ,business.industry ,Section (typography) ,Schematic ,Medicine ,General Medicine ,Gregg shorthand ,business ,Hospital records ,Linguistics ,Term (time) - Abstract
From her practical experience as a physician's secretary and as a teacher of medical shorthand, the author has prepared a manual for medical secretaries and assistants. The material presented is clinically oriented, each section devoted to a particular system or organ of the body. Before confronting the reader with definitions and shorthand symbols for each specific term or phrase, Miss Eshom provides a simplified description of the system under discussion and frequently includes helpful schematic drawings. This background information distinguishes her book from the usual text of medical shorthand. The practice material was taken from actual office and hospital records, and the author has suggested a practice routine which should assist in committing to memory these new shorthand symbols (based upon conventional Gregg shorthand). An extensive index has also been supplied for speedy reference. Although for maximal retention classroom instruction and supervision would probably be required, Miss Eshom's book should
- Published
- 1967
33. Nonlinear TeraHertz Transmission by Liquid Water at 1 THz
- Author
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Nidhi Adhlakha, Paola Di Pietro, Fabio Novelli, Debasish Das Mahanta, Chun Yu Ma, Ellen M. Adams, Thorsten Ockelmann, Martina Havenith, and Andrea Perucchi
- Subjects
Materials science ,Terahertz radiation ,Liquid water ,water ,Physics::Optics ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,lcsh:Technology ,terahertz ,lcsh:Chemistry ,General Materials Science ,Spectroscopy ,Instrumentation ,lcsh:QH301-705.5 ,Fluid Flow and Transfer Processes ,Coupling ,business.industry ,lcsh:T ,Process Chemistry and Technology ,General Engineering ,Solvation ,021001 nanoscience & nanotechnology ,lcsh:QC1-999 ,0104 chemical sciences ,Computer Science Applications ,Nonlinear system ,Transmission (telecommunications) ,lcsh:Biology (General) ,lcsh:QD1-999 ,lcsh:TA1-2040 ,Optoelectronics ,nonlinear ,Transient (oscillation) ,solvation ,0210 nano-technology ,business ,lcsh:Engineering (General). Civil engineering (General) ,lcsh:Physics - Abstract
The solvation properties of liquid water originate from the transient network of hydrogen-bonded molecules. In order to probe the coupling between the different modes of this network, nonlinear terahertz (THz) spectroscopy techniques are required. Ideally, these techniques should use a minimal volume and capitalize on sensitive field-resolved detection. Here we performed open aperture z-scan transmission experiments on static liquid cells, and detect the THz fields with electro-optical techniques. We show that it is possible to quantify the nonlinear response of liquid water at ~1 THz even when large signals originate from the sample holder windows.
- Full Text
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