DOCSLIB.ORG

Protein Shape Modulates Crowding Effects

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Protein Shape Modulates Crowding Effects Protein shape modulates crowding effects Alex J. Gusemana, Gerardo M. Perez Goncalvesa, Shannon L. Speera, Gregory B. Youngb, and Gary J. Pielaka,b,c,d,1 aDepartment of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; bDepartment of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; cLineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; and dIntegrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 Edited by Susan Marqusee, University of California, Berkeley, CA, and approved September 12, 2018 (received for review June 18, 2018) Protein−protein interactions are usually studied in dilute buffered mildly influenced by hard-core repulsions. Berg also predicted solutions with macromolecule concentrations of <10 g/L. In cells, that more-compact dimers are more likely to be stabilized by however, the macromolecule concentration can exceed 300 g/L, hard-core repulsions. Here, we test this idea by changing the resulting in nonspecific interactions between macromolecules. shape of a dimer in a controlled fashion. These interactions can be divided into hard-core steric repulsions Scaled particle theory is based on statistical mechanics. For and “soft” chemical interactions. Here, we test a hypothesis from situations like those investigated here, the theory considers so- scaled particle theory; the influence of hard-core repulsions on a lution nonideality as arising from the presence of cosolutes (13– protein dimer depends on its shape. We tested the idea using a 15). As often applied, the solvent and cosolutes are considered side-by-side dumbbell-shaped dimer and a domain-swapped ellip- hard spheres, which leads to three consequences: Molecules only soidal dimer. Both dimers are variants of the B1 domain of protein interact when they touch, the interaction energy is purely re- G and differ by only three residues. The results from the relatively pulsive, and the energy has a strong distance dependence. The inert synthetic polymer crowding molecules, Ficoll and PEG, sup- inability of billiard balls to interpenetrate is a macroscopic ex- port the hypothesis, indicating that the domain-swapped dimer is ample. Water and cosolute concentration are expressed as vol- stabilized by hard-core repulsions while the side-by-side dimer ume occupancy, Φ, the unitless parameter indicating the fraction shows little to no stabilization. We also show that protein coso- of the volume they occupy. The reversible work (i.e., free energy) lutes, which interact primarily through nonspecific chemical inter- to produce a monomer- and dimer-sized hole in water and in a actions, have the same small effect on both dimers. Our results cosolute-containing solution is calculated, and a thermodynamic suggest that the shape of the protein dimer determines the influ- cycle (16) is used to estimate the change in the free energy ence of hard-core repulsions, providing cells with a mechanism for of dissociation (KD→M) in cosolute solution minus the value − regulating protein protein interactions. in water, i.e., ΔΔG°′D→M, where a positive value indicates stabilization. macromolecular crowding | protein−protein interactions | The theory has several shortcomings, including its spherical scaled particle theory assumptions, neglect of chemical interactions, including solva- tion, and its extreme sensitivity to sphere size and density (17, rotein−protein interactions are essential for maintaining 18). Nevertheless, it has been successfully applied to assess the Pcellular homeostasis (1). Details of their equilibria under effects of crowding-induced hard-core interactions on protein thermodynamically ideal conditions have provided a trove of stability and protein−protein interactions (18–22). For instance, information. Ideality in this sense refers to dilute solutions, its application to protein stability led to the idea that crowding where each monomer contacts only solvent or another monomer, conditions far removed from those in cells where protein− Significance protein interactions evolved. In the cytoplasm, and other cellular compartments and biological fluids, macromolecules can occupy Macromolecular crowding influences protein−protein interac- up to 30% of the volume, and their concentrations often exceed tions via hard-core repulsions and chemical interactions. Scaled 300 g/L (2). particle theory predicts that the effect of hard-core repulsions Protein molecules take part in more-complex interactions depends on the shape of the protein complex, and simple ideas under nonideal conditions. The surrounding macromolecules about chemical interactions predict a dominant role for the influence proteins in two ways, neither of which is significant in chemical qualities of the protein surface. The theory predicts dilute solution. Hard-core repulsions arise from high volume that a collapsed, ellipsoidal, dimer will be stabilized by hard- occupancy, because two molecules cannot occupy the same space core repulsions, whereas a less collapsed, side-by-side, dimer at the same time. This volume exclusion favors the most compact will not. We applied scaled particle theory to two dimers with state of a protein (3). Chemical interactions comprise transient nearly identical surfaces but different shapes. Our results contacts between protein surfaces arising from the diverse support the predictions; crowders that interact primarily chemical landscapes of proteins (4). When repulsive (i.e., like through hard-core repulsions stabilize the ellipsoidal domain- charges), they favor the state that maximizes the distance be- swapped dimer more than the side-by-side dimer, whereas tween charges, adding to the hard-core repulsions and stabilizing crowders that interact via chemical interactions have the same the native state. Attractive chemical interactions (e.g., opposite effect on both dimers. charges, hydrogen bonds) are destabilizing. We are beginning to understand how hard-core repulsions and chemical interactions Author contributions: A.J.G., G.B.Y., and G.J.P. designed research; A.J.G., G.M.P.G., and affect protein stability (5), but there are few studies about S.L.S. performed research; A.J.G. contributed new reagents/analytic tools; A.J.G., CHEMISTRY crowding effects on protein−protein interactions (6–9). G.M.P.G., S.L.S., and G.J.P. analyzed data; and A.J.G., G.M.P.G., S.L.S., G.B.Y., and G.J.P. Given the existential roles of both protein−protein interac- wrote the paper. tions and crowding in biology (10), we are undertaking efforts to The authors declare no conflict of interest. determine the effect of crowding on the simplest of protein This article is a PNAS Direct Submission. complexes, homodimers. Our first endeavor, which involved a Published under the PNAS license. side-by-side homodimer, highlighted chemical interactions and 1To whom correspondence should be addressed. Email: [email protected]. showed a small contribution from hard-core repulsions (11, 12). This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. These results were predicted by Berg (12), who used scaled 1073/pnas.1810054115/-/DCSupplemental. BIOPHYSICS AND particle theory to suggest that side-by-side dimers would be only Published online October 9, 2018. COMPUTATIONAL BIOLOGY www.pnas.org/cgi/doi/10.1073/pnas.1810054115 PNAS | October 23, 2018 | vol. 115 | no. 43 | 10965–10970 Downloaded by guest on October 9, 2021 The A34F variant (Fig. 2) forms a dimer reminiscent of kissing spheres (Figs. 1 and 3) that does not require a large conforma- tional change (26, 28). Dimerization occurs because the Phe-34 side chain becomes part of the hydrophobic core, displacing the Tyr-33 side chain at the surface and causing the C-terminal end of the sole helix to unfold, forming a pocket for the Tyr-33 side chain of the other monomer. The dimer is also stabilized by hydrogen bonds along the now adjacent β-sheets. The L5V;F30V;Y33F;A34F variant forms a more compact domain-swapped dimer (Fig. 2) whose monomer is a partially folded, molten-globule-like species (25, 27) (SI Appendix, Fig. S1) that undergoes refolding to form the dimer (Fig. 3). Swapping the turn between β-strand three and β-strand four results in inter- changed secondary structural units with concomitant formation of several interprotein interactions. The volumes, solvent accessible surface areas, changes in solvent-accessible surface area (SASA), and measured free energies of dissociation are shown in Fig. 3. The properties of protein surfaces determine the chemical ΔΔ o′ Fig. 1. Scaled particle theory-derived values of G D→M as a function of interactions with cosolutes (29–33). An advantageous aspect of eccentricity, L, at 10 values of L (solid symbols) of the indicated radii and the GB1 system is that the interactions are similar for both di- Φ volume occupancies, . As predicted by Berg (12), the more compact mers because their primary structures, and hence their surfaces, spherical, but not the side-by-side, dimer is stabilized. Shaded areas indicate are highly similar (Fig. 3). However, the change in SASA for the the estimated eccentricities of the GB1 dimers. The 4.1-Å species represents sucrose, and the 35-Å species represents BSA. domain-swapped dimer does not reflect its interface area, be- cause the peptide chains penetrate each other. In summary, the GB1 system is well suited for studying crowding effects on pro- effects comprise both hard-core repulsions and attractive or re- tein complex shape, because the monomers are not far removed pulsive chemical interactions (16, 23). from spheres, and the dimers have different shapes but similar We use the implementation of scaled particle theory (13) surfaces. described by Berg (12) to assess crowding effects. The monomers are assumed to be spheres. The dimers have twice the volume of Results the monomer, but their shapes, quantified as the eccentricity, L, Scaled Particle Theory Predictions. Positive values of ΔΔG°′D→M is varied (Fig. 1).
Load more

Recommended publications
  • Dimerization of Carboxylic Acids: an Equation of State Approach
    Downloaded from orbit.dtu.dk on: Oct 05, 2021 Dimerization of Carboxylic Acids: An Equation of State Approach Tsivintzelis, Ioannis; Kontogeorgis, Georgios; Panayiotou, Costas Published in: Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical Link to article, DOI: 10.1021/acs.jpcb.6b10652 Publication date: 2017 Document Version Peer reviewed version Link back to DTU Orbit Citation (APA): Tsivintzelis, I., Kontogeorgis, G., & Panayiotou, C. (2017). Dimerization of Carboxylic Acids: An Equation of State Approach. Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical, 121(9), 2153-2163. https://doi.org/10.1021/acs.jpcb.6b10652 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. On the Dimerization of Carboxylic Acids: An Equation of State Approach Ioannis Tsivintzelis*,1, Georgios M. Kontogeorgis2 and Costas Panayiotou1 1Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece. 2Center for Energy Resources Engineering (CERE), Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs.
    [Show full text]
  • Spin Delocalization, Polarization, and London Dispersion Forces Govern the Formation of Diradical Pimers
    Chemistry Publications Chemistry 2-22-2020 Spin Delocalization, Polarization, and London Dispersion Forces Govern the Formation of Diradical Pimers Joshua P. Peterson Iowa State University, [email protected] Arkady Ellern Iowa State University, [email protected] Arthur H. Winter Iowa State University, [email protected] Follow this and additional works at: https://lib.dr.iastate.edu/chem_pubs Part of the Chemistry Commons The complete bibliographic information for this item can be found at https://lib.dr.iastate.edu/ chem_pubs/1215. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Article is brought to you for free and open access by the Chemistry at Iowa State University Digital Repository. It has been accepted for inclusion in Chemistry Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Spin Delocalization, Polarization, and London Dispersion Forces Govern the Formation of Diradical Pimers Abstract Some free radicals are stable enough to be isolated, but most are either unstable transient species or exist as metastable species in equilibrium with a dimeric form, usually a spin-paired sigma dimer or a pi dimer (pimer). To gain insight into the different modes of dimerization, we synthesized and evaluated a library of 15 aryl dicyanomethyl radicals in order to probe what structural and molecular parameters lead to σ- versus π-dimerization. We evaluated the divergent dimerization behavior by measuring the strength of each radical association by variable-temperature electron paramagnetic resonance spectroscopy, determining the mode of dimerization (σ- or π-dimer) by UV–vis spectroscopy and X-ray crystallography, and performing computational analysis.
    [Show full text]
  • Polymorphism, Halogen Bonding, and Chalcogen Bonding in the Diiodine Adducts of 1,3- and 1,4-Dithiane
    molecules Article Polymorphism, Halogen Bonding, and Chalcogen Bonding in the Diiodine Adducts of 1,3- and 1,4-Dithiane Andrew J. Peloquin 1, Srikar Alapati 2, Colin D. McMillen 1, Timothy W. Hanks 2 and William T. Pennington 1,* 1 Department of Chemistry, Clemson University, Clemson, SC 29634, USA; [email protected] (A.J.P.); [email protected] (C.D.M.) 2 Department of Chemistry, Furman University, Greenville, SC 29613, USA; [email protected] (S.A.); [email protected] (T.W.H.) * Correspondence: [email protected] Abstract: Through variations in reaction solvent and stoichiometry, a series of S-diiodine adducts of 1,3- and 1,4-dithiane were isolated by direct reaction of the dithianes with molecular diiodine in solution. In the case of 1,3-dithiane, variations in reaction solvent yielded both the equatorial and the axial isomers of S-diiodo-1,3-dithiane, and their solution thermodynamics were further studied via DFT. Additionally, S,S’-bis(diiodo)-1,3-dithiane was also isolated. The 1:1 cocrystal, (1,4-dithiane)·(I2) was further isolated, as well as a new polymorph of S,S’-bis(diiodo)-1,4-dithiane. Each structure showed significant S···I halogen and chalcogen bonding interactions. Further, the product of the diiodine-promoted oxidative addition of acetone to 1,4-dithiane, as well as two new cocrystals of 1,4-dithiane-1,4-dioxide involving hydronium, bromide, and tribromide ions, was isolated. Keywords: crystal engineering; chalcogen bonding; halogen bonding; polymorphism; X-ray diffraction Citation: Peloquin, A.J.; Alapati, S.; McMillen, C.D.; Hanks, T.W.; Pennington, W.T.
    [Show full text]
  • Understanding the Kinetics of the Clo Dimer Cycle
    Atmos. Chem. Phys., 7, 3055–3069, 2007 www.atmos-chem-phys.net/7/3055/2007/ Atmospheric © Author(s) 2007. This work is licensed Chemistry under a Creative Commons License. and Physics Understanding the kinetics of the ClO dimer cycle M. von Hobe1, R. J. Salawitch2, T. Canty2, H. Keller-Rudek3, G. K. Moortgat3, J.-U. Grooß1, R. Muller¨ 1, and F. Stroh1 1Forschungszentrum Julich¨ GmbH, Institute for Chemistry and Dynamics of the Geosphere (ICG-1), Julich,¨ Germany 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA 3Max-Planck-Institute for Chemistry, Atmospheric Chemistry Division, Mainz, Germany Received: 12 June 2006 – Published in Atmos. Chem. Phys. Discuss.: 14 August 2006 Revised: 17 October 2006 – Accepted: 22 May 2007 – Published: 15 June 2007 Abstract. Among the major factors controlling ozone loss in 1 Introduction the polar vortices in winter/spring is the kinetics of the ClO dimer catalytic cycle. Here, we propose a strategy to test and The ClO dimer cycle is one of the most important catalytic improve our understanding of these kinetics by comparing cycles destroying ozone in the polar vortices in late win- and combining information on the thermal equilibrium be- ter/early spring (Molina and Molina, 1987): tween ClO and Cl2O2, the rate of Cl2O2 formation, and the krec Cl O photolysis rate from laboratory experiments, theoret- −→ 2 2 ClO + ClO + M Cl O + M (R1) ical studies and field observations. Concordant with a num- ←− 2 2 k ber of earlier studies, we find considerable inconsistencies of diss some recent laboratory results with rate theory calculations J Cl2O2 + hν −→ Cl + ClOO (R2) and stratospheric observations of ClO and Cl2O2.
    [Show full text]
  • (100) Surface with Fluorine in Presence of Water – a Density Functional Study
    Int. J. Mol. Sci. 2001, 2, 40-56 International Journal of Molecular Sciences ISSN 1422-0067 © 2001 by MDPI www.mdpi.org/ijms/ Structural And Energetic Changes of Si (100) Surface With Fluorine in Presence of Water – A Density Functional Study Abhijit Chatterjee *, Takashi Iwasaki and Takeo Ebina Inorganic Materials Section, Tohoku National Industrial Research Institute, 4-2-1 Nigatake, Miyagino- ku, Sendai 983-8551, JAPAN. Fax: +81-22-236-6839. Phone: +81-22-237-5211 * Author to whom correspondence should be addressed. Email: [email protected] Received: 16 November 2000 / Accepted: 28 January 2001 / Published: 1 May 2001 Abstract: We report density functional electronic structure calculations to monitor the change in the surface characteristics of the Si (100)-2x1 surface after fluorination followed by interaction with water. Embedded finite silicon clusters are used to model an extended Si (100)-2x1 surface. Two high symmetry pathways and subsequent adsorption sites were examined: (i) adsorption of an fluorine atom directing onto a silicon dangling bond to form a monocoordinated fluorine atom (ii) adsorption of a fluorine atom directing on top of silicon dimer to form a bridging dicoordinated fluorine atom. However, in the later case we find that no barrier exists for the bridging fluorine atom to slide towards silicon dimer dangling bond to form more stable mono coordinated Si-F bond. We calculated activation barriers and equilibrium surface configuration as a function of fluorine coverage upto 2.0 ML. We compared the stability of the fluorinated surface. The results were compared with existing experimental and theoretical results. The reaction of water with HF treated Si surface is monitored.
    [Show full text]
  • The Dimer-Monomer Equilibrium of SARS-Cov-2 Main
    www.nature.com/scientificreports OPEN The dimer‑monomer equilibrium of SARS‑CoV‑2 main protease is afected by small molecule inhibitors Lucia Silvestrini1, Norhan Belhaj2, Lucia Comez3, Yuri Gerelli2, Antonino Lauria4, Valeria Libera5, Paolo Mariani2, Paola Marzullo4, Maria Grazia Ortore2, Antonio Palumbo Piccionello4, Caterina Petrillo5, Lucrezia Savini1, Alessandro Paciaroni5 & Francesco Spinozzi2* The maturation of coronavirus SARS‑CoV‑2, which is the etiological agent at the origin of the COVID‑ 19 pandemic, requires a main protease Mpro to cleave the virus‑encoded polyproteins. Despite a wealth of experimental information already available, there is wide disagreement about the Mpro monomer‑dimer equilibrium dissociation constant. Since the functional unit of Mpro is a homodimer, the detailed knowledge of the thermodynamics of this equilibrium is a key piece of information for possible therapeutic intervention, with small molecules interfering with dimerization being potential broad‑spectrum antiviral drug leads. In the present study, we exploit Small Angle X‑ray Scattering (SAXS) to investigate the structural features of SARS‑CoV‑2 Mpro in solution as a function of protein concentration and temperature. A detailed thermodynamic picture of the monomer‑dimer equilibrium is derived, together with the temperature‑dependent value of the dissociation constant. SAXS is also used to study how the Mpro dissociation process is afected by small inhibitors selected by virtual screening. We fnd that these inhibitors afect dimerization and enzymatic activity to a diferent extent and sometimes in an opposite way, likely due to the diferent molecular mechanisms underlying the two processes. The Mpro residues that emerge as key to optimize both dissociation and enzymatic activity inhibition are discussed.
    [Show full text]
  • Nitrogen Oxides (Nox), Why and How They Are Controlled
    United States Office of Air Quality EPA 456/F-99-006R Environmental Protection Planning and Standards November 1999 Agency Research Triangle Park, NC 27711 Air EPA-456/F-99-006R November 1999 Nitrogen Oxides (NOx), Why and How They Are Controlled Prepared by Clean Air Technology Center (MD-12) Information Transfer and Program Integration Division Office of Air Quality Planning and Standards U.S. Environmental Protection Agency Research Triangle Park, North Carolina 27711 DISCLAIMER This report has been reviewed by the Information Transfer and Program Integration Division of the Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency and approved for publication. Approval does not signify that the contents of this report reflect the views and policies of the U.S. Environmental Protection Agency. Mention of trade names or commercial products is not intended to constitute endorsement or recommendation for use. Copies of this report are available form the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Virginia 22161, telephone number (800) 553-6847. CORRECTION NOTICE This document, EPA-456/F-99-006a, corrects errors found in the original document, EPA-456/F-99-006. These corrections are: Page 8, fourth paragraph: “Destruction or Recovery Efficiency” has been changed to “Destruction or Removal Efficiency;” Page 10, Method 2. Reducing Residence Time: This section has been rewritten to correct for an ambiguity in the original text. Page 20, Table 4. Added Selective Non-Catalytic Reduction (SNCR) to the table and added acronyms for other technologies. Page 29, last paragraph: This paragraph has been rewritten to correct an error in stating the configuration of a typical cogeneration facility.
    [Show full text]
  • Robust Synthesis of Two-Dimensional Metal Dichalcogenides and Their Alloys by Active Chalcogen Monomer Supply
    Robust synthesis of two-dimensional metal dichalcogenides and their alloys by active chalcogen monomer supply Kaihui Liu ( [email protected] ) State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871 https://orcid.org/0000-0002-8781-2495 Yonggang Zuo Institute of Physics, Chinese Academy of Sciences https://orcid.org/0000-0003-1262-6767 Can Liu State Key Laboratory for Mesoscopic Physics, Frontiers Science Centre for Nanooptoelectronics, School of Physics, Peking University, Beijing, China https://orcid.org/0000-0001-5451-4144 Liping Ding Institute for Basic Science Ruixi Qiao Peking University Chang Liu Peking University Ying Fu Institute of Physics, Chinese Academy of Sciences Kehai Liu Institute of Physics, Chinese Academy of Sciences Xu Zhou South China Normal University https://orcid.org/0000-0003-3318-8735 Qinghe Wang Peking University Quanlin Guo Peking University Guodong Xue Peking University Jinhuan Wang Beijing Institute of Technology Hao Hong State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Centre of Quantum Matter, School of Physics, Peking University Muhong Wu Peking University https://orcid.org/0000-0003-3607-8945 Dapeng Yu Institute for Quantum Science and Engineering and Department of Physics, South University of Science and Technology of China Enge Wang Peking University Xuedong Bai Institute of Physics, Chinese Academy of Sciences https://orcid.org/0000-0002-1403-491X Feng Ding Institute for Basic Science https://orcid.org/0000-0001-9153-9279 Physical Sciences - Article Keywords: Two-dimensional transition metal dichalcogenides, alloys, chalcogen monomers supply Posted Date: April 21st, 2021 DOI: https://doi.org/10.21203/rs.3.rs-411823/v1 License: This work is licensed under a Creative Commons Attribution 4.0 International License.
    [Show full text]
  • Dimerization and Hydration of Benzoic Acid and Salicylic Acid in Aprotic Solvents
    This dissertation has been microfilmed exactly as received 69 -8602 VAN DUYNE, Roger Lynn, 1942- DIMERIZATION AND HYDRATION OF BENZOIC ACID AND SALICYLIC ACID IN APROTIC SOLVENTS. The University of Oklahoma, Ph.D., 1969 Chemistry, physical University Microfilms, Inc., Ann Arbor, Michigan THE UNIVERSITY OF OKLAHOMA GRADUATE COLLEGE DIMERIZATION AND HYDRATION OF BENZOIC ACID AND SALICYLIC ACID IN APROTIC SOLVENTS A DISSERTATION SUBMITTED TO THE GRADUATE FACULTY in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY BY ROGER LYNN VAN DUYNE Norman, Oklahoma 1969 DIMERIZATION AND HYDRATION OF BENZOIC ACID AND SALICYLIC ACID IN APROTIC SOLVENTS APPROVED BY ricpizëf DISSERTATION COMMITTEE ACKNOWLEDGMENT The author is extremely grateful for the invaluable guidance and encouragement received from Dr. Sherril D. Christian and the late Dr. Harold E. Affsprung throughout the course of this investigation. He is also grateful for the valued friendship and assistance of his colleagues in the laboratory, particularly Dr. James R. Johnson, Dr. M. Duane Gregory and Mr. Ronald L. Lynch who have assisted in many aspects of the study. In addition, the writer acknowledges his nephew, Mr. Larry Zerby, for illustrating the vapor pressure lowering apparatus. I especially wish to thank my wife, Cherie, for her gratifying encouragement and understanding, and for the many sacrifices which she has willingly made to make graduate study possible. This research was supported by funds from the National Institutes of Health and a Traineeship from the National Aeronautics and Space Administration. Ill Dedicated with love to the memory of my father, Charles Bentley Van Duyne IV TABLE OF CONTENTS Page LIST OF TABLES.......................................
    [Show full text]
  • Surface Pka of Saturated Carboxylic Acids at the Air/Water Interface
    This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. pubs.acs.org/JPCC Article K Surface p a of Saturated Carboxylic Acids at the Air/Water Interface: A Quantum Chemical Approach Yuri B. Vysotsky, Elena S. Kartashynska, Dieter Vollhardt,* and Valentin B. Fainerman Cite This: J. Phys. Chem. C 2020, 124, 13809−13818 Read Online ACCESS Metrics & More Article Recommendations ABSTRACT: In the present study a theoretical approach is proposed for the pKa estimation of monolayers at the air/water interface on the basis of saturated carboxylic acids. This model involves calculating only the Gibbs energies of formation and dimerization of carboxylic acid associates in the neutral and dissociated forms, as well as the corresponding monomers in the water and gas phases. The model does not require the construction of any thermodynamic cycles. The calculations are performed using semiempirical quantum chemical methods PM3 and PM6 within the framework of the conductor-like screening model for monomers and − dimers of carboxylic acids CnH2n+1COOH (n =6 16). It is shown that the minimum clusterization Gibbs energy corresponds to associates with the degree of dissociation α = 0.5. A relationship is derived between the surface and bulk pKa values. In particular, it follows from this that, unlike the bulk pKa, the surface pKa depends on the alkyl chain length of the surfactant. It is due to the difference between the solvation energies of the alkyl chains of the corresponding neutral and dissociated monomers.
    [Show full text]
  • Vibrational Resonant Inelastic X-Ray Scattering in Liquid Acetic Acid
    www.nature.com/scientificreports OPEN Vibrational resonant inelastic X‑ray scattering in liquid acetic acid: a ruler for molecular chain lengths Viktoriia Savchenko1,2,3*, Iulia Emilia Brumboiu1,4, Victor Kimberg1,2,3*, Michael Odelius5*, Pavel Krasnov2,3, Ji‑Cai Liu6, Jan‑Erik Rubensson7, Olle Björneholm7, Conny Såthe8, Johan Gråsjö7,13, Minjie Dong7, Annette Pietzsch9, Alexander Föhlisch9,10, Thorsten Schmitt11, Daniel McNally11, Xingye Lu11, Sergey P. Polyutov2,3, Patrick Norman1, Marcella Iannuzzi12, Faris Gel’mukhanov1,2,3 & Victor Ekholm7,8 Quenching of vibrational excitations in resonant inelastic X‑ray scattering (RIXS) spectra of liquid acetic acid is observed. At the oxygen core resonance associated with localized excitations at the O–H bond, the spectra lack the typical progression of vibrational excitations observed in RIXS spectra of comparable systems. We interpret this phenomenon as due to strong rehybridization of the unoccupied molecular orbitals as a result of hydrogen bonding, which however cannot be observed in x‑ray absorption but only by means of RIXS. This allows us to address the molecular structure of the liquid, and to determine a lower limit for the average molecular chain length. Te hydrogen bond (HB) is of central importance in chemistry and biochemistry and it is crucial in chemical reactions, supramolecular structures, molecular assemblies, and even life processes. Consequently, HBs have been immensely studied over the years, exploiting a plethora of spectroscopy and scattering methods, with liquid water as an important showcase1. Te new generation synchrotron radiation sources have allowed for a refnement of the resonant inelastic X-rays scattering (RIXS) technique, which now gives access to detailed information about the nature of the HB, not only in liquid water2–6, but also liquids like acetone7 and methanol8.
    [Show full text]
  • An Investigation of the Chalcogen Dimers
    This is an electronic reprint of the original article. This reprint may differ from the original in pagination and typographic detail. Author(s): Ritch, Jamie; Chivers, Tristram; Eisler, Dana; Tuononen, Heikki Title: Experimental and Theoretical Investigations of Structural Isomers of Dichalcogenoimidodiphosphinate Dimers: Dichalcogenides or Spirocyclic Contact Ion Pairs? Year: 2007 Version: Please cite the original version: Ritch, J., Chivers, T., Eisler, D., & Tuononen, H. (2007). Experimental and Theoretical Investigations of Structural Isomers of Dichalcogenoimidodiphosphinate Dimers: Dichalcogenides or Spirocyclic Contact Ion Pairs?. Chemistry - A European Journal, 13(16), 4643-4653. https://doi.org/10.1002/chem.200700001 All material supplied via JYX is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. Experimental and Theoretical Investigations of Structural Isomers of Dichalcogenoimidodiphosphinate Dimers: Dichalcogenides or Spirocyclic Contact Ion Pairs? Jamie S. Ritch,[a] Tristram Chivers,*[a] Dana J. Eisler,[a] and Heikki M. Tuononen[b] [a] J. S. Ritch, Prof. T. Chivers,* Dr. D. J. Eisler Department of Chemistry University of Calgary Calgary, AB T2N 1N4 (Canada) Fax: (+1) 403-289-9488 E-mail: [email protected] [b] Dr H. M. Tuononen Department of Chemistry University of Jyväskylä P.O. Box 35, 40014 Jyväskylä (Finland) 1 Abstract A synthetic protocol for the tert-butyl substituted dichalcogenoimidodiphosphinates [(tmeda)Na((EPtBu2)2N)] (3a, E = S; 3b, E = Se; 3c, E = Te) has been developed.
    [Show full text]