Theoretical study of ions at phase interfaces

2 '\UToREFEaÁr v ČBsxÉuJAZYCE Autoreferát v českérnjazyce Předk1ádaná práce sestává z deseti publikací1_1o v mezinárodních recenzovaných Časopi. sech' doplněných rozšířenýmúvodem a diskusí získaných výsledků. Studovanou tématikuje moŽné rozdě]it do tří skupin, jejichž spoiečným jmenovatelem je chování iontů na fázových rozhraních. V práci se zabýwáme o ionty na rozhraní voda/vzduch Některé anorganické ionty se mohou, v rozporu s obecně přijímanými teoriemi, aku. mulovat na rozhraní voda/vzduch. Jedná se zejmóna o velké polarizovatelné antonty, např. jodidový, azidový, nebo thiokyanátoly. U organických kationtů s alifatickými řetězci je důvodem k akumulaci na rozhraní jejich hvdrofobicita. Rovnováha rrrezl hydratačnímia polarizačnímisilami v komplexních ionto'4ich roztocích je detailně diskutována v této črístidisertačnípráce. o ionty na rozhraní voda/led Vypuzování soli z mrznoucích slaných roztoků (např' z mořské vody) je důleŽitý přírodní děj, který ovlivňuje globální klima. NIetodami molekulovó dynamiky jsme studovali mechanismus tohoto procesu na atomární úrovni. o ionty na rozhraní voda/protein Ve dvou různých studiích jsme se zabývali specifický'rni interakcemi mezi proteiny a ionty. Nejdříve diskutujeme vliv iontů na aktivitu enzymu křenové peroxidázy. Druhý projekt poskytnul vysvětlení faktu, Že...1 ABSTRACT IN ENGIISři Abstract in English The present thesis consists of ten publicationsl-10 in international peer-reviewed journals with an extended introduction and a detailed discussion of the content of these papers. The work can be divided into three different topics, with ion behavior at interfaces being the common denominator. Namely, we focused on the following three issues: o lons at the ďr/water interface \\'e discuss the fact that certain inorganic ions can (contrary to the textbook knowl- edge) exhibit a propensity for the air/water interface. This is particularly true for large poiarizable anions, such as heavier halides, azide, or thiocyanate. Cations with aliphatic chains also show affinity to the surface, however, due to different reason - their hydrophobicity. The interplay between hydration and polarization forces in complex ionic mixtures is discussed in detail in this part of the thesis. o Ions at the ice/water interface Brine rejection from freezing salt solutions (e.g., sea water) is a very important natural phenomenon influencing the global climate. Molecular details of this process are established using molecular dynamics simulations. o lons at the protein/water interface We studied specific ion-protein interactions. First, we discuss the possible reasons behind the salt induced...Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryPřírodovědecká fakultaFaculty of Scienc

Theoretical study of ions at phase interfaces

1 ABSTRACT IN ENGIISři Abstract in English The present thesis consists of ten publicationsl-10 in international peer-reviewed journals with an extended introduction and a detailed discussion of the content of these papers. The work can be divided into three different topics, with ion behavior at interfaces being the common denominator. Namely, we focused on the following three issues: o lons at the ďr/water interface \\'e discuss the fact that certain inorganic ions can (contrary to the textbook knowl- edge) exhibit a propensity for the air/water interface. This is particularly true for large poiarizable anions, such as heavier halides, azide, or thiocyanate. Cations with aliphatic chains also show affinity to the surface, however, due to different reason - their hydrophobicity. The interplay between hydration and polarization forces in complex ionic mixtures is discussed in detail in this part of the thesis. o Ions at the ice/water interface Brine rejection from freezing salt solutions (e.g., sea water) is a very important natural phenomenon influencing the global climate. Molecular details of this process are established using molecular dynamics simulations. o lons at the protein/water interface We studied specific ion-protein interactions. First, we discuss the possible reasons behind the salt induced..

Specific Ion Effects at Protein Surfaces: A Molecular Dynamics Study of Bovine Pancreatic Trypsin Inhibitor and Horseradish Peroxidase in Selected Salt Solutions

The distribution of sodium, choline, sulfate, and chloride ions around two proteins, horseradish peroxidase (HRP) and bovine pancreatic trypsin inhibitor (BPTI), is investigated by means of molecular dynamics simulations with the aim to elucidate ion adsorption at the protein surface. Although the two proteins under investigation are very different from each other, the ion distributions around them are remarkably similar. Sulfate is always strongly attached to the proteins, choline shows a significant, but unspecific, propensity for the protein surfaces, and sodium ions have a weak surface affinity, while chloride has virtually no preference for the protein surface. In mixtures of all four ion species in protein solutions, the resulting distributions are almost a superposition of the distributions of sodium sulfate and choline chloride, except that sodium partially replaces choline close to the proteins. The present simulations support a picture of ions interacting with individual ionic and polar amino acid groups rather than with an averaged protein surface. The results thus show how subtle the so-called Hofmeister and electroselectivity effects are in salt solution of proteins, making all simplified interaction models questionable

Ion-specific thermodynamics of multicomponent electrolytes: a hybrid HNC/MD approach

Using effective infinite dilution ion-ion interaction potentials derived from explicit-water molecular dynamics (MD) computer simulations in the hypernetted-chain (HNC) integral equation theory we calculate the liquid structure and thermodynamic properties, namely, the activity and osmotic coefficients of various multicomponent aqueous electrolyte mixtures. The electrolyte structure expressed by the ion-ion radial distribution functions is for most ions in excellent agreement with MD and implicit solvent Monte Carlo (MC) simulation results. Calculated thermodynamic properties are also represented consistently among these three methods. Our versatile HNC/MD hybrid method allows for a quick prediction of the thermodynamics of multicomponent electrolyte solutions for a wide range of concentrations and an efficient assessment of the validity of the employed MD force-fields with possible implications in the development of thermodynamicall