The mechanism underlying the functionalisation of cobalt nanoparticles by carboxylic acids: a first-principles computational study

The promise of biocompatible magnetic nanoparticles with high magnetic saturation in the implementation as drug carriers and hyperthermia agents has generated significant interest in functionalised cobalt nanoparticles. Carboxylic acid coatings on metallic nanoparticles have been shown as an attractive option owing to their respectable stability and biocompatibility. However, only limited information is available on the molecular mechanism leading to the formation of such protective coatings. In this study, ab initio molecular dynamics simulations have been used to unravel the functionalisation mechanism starting from a neutral cobalt cluster and valeric acid molecules. Three stages were detected in the coating process: (i) rapid initial adsorption of acid molecules, (ii) simultaneous adsorption of new molecules and dissociation of those already interacting with the cluster, and, finally, (iii) grouping of dissociated hydrogen atoms and subsequent desorption of acid molecules. The fate of the hydrogen atoms was probed through a combination of static and dynamic ab initio modelling approaches, which predicted H2 generation with favourable energetics. A better understanding of the functionalisation and interaction mechanisms will aid the rational design of biocompatible cobalt nanoparticles for various applications

Adsorbate-Induced Segregation of Cobalt from PtCo Nanoparticles: Modeling Au Doping and Core AuCo Alloying for the Improvement of Fuel Cell Cathode Catalysts

Platinum, when used as a cathode material for the oxygen reduction reaction, suffers from high overpotential and possible dissolution, in addition to the scarcity of the metal and resulting cost. Although the introduction of cobalt has been reported to improve reaction kinetics and decrease the precious metal loading, surface segregation or complete leakage of Co atoms causes degradation of the membrane electrode assembly, and either of these scenarios of structural rearrangement eventually decreases catalytic power. Ternary PtCo alloys with noble metals could possibly maintain activity with a higher dissolution potential. First-principles-based theoretical methods are utilized to identify the critical factors affecting segregation in Pt–Co binary and Pt–Co–Au ternary nanoparticles in the presence of oxidizing species. With a decreasing share of Pt, surface segregation of Co atoms was already found to become thermodynamically viable in the PtCo systems at low oxygen concentrations, which is assigned to high charge transfer between species. While the introduction of gold as a dopant caused structural changes that favor segregation of Co, creation of CoAu alloy core is calculated to significantly suppress Co leakage through modification of the electronic properties. The theoretical framework of geometrically different ternary systems provides a new route for the rational design of oxygen reduction catalysts

Terminologija klinične prehrane: Motnje prehranjenosti in s prehranjenostjo povezana stanja

Izhodišča: Prehransko stanje posameznika uvrščamo med ključne dejavnike njegovega zdravja. Za učinkovito individualno in multidisciplinarno obravnavo stanj, povezanih s prehranskim stanjem posameznika, moramo dobro poznati terminologijo klinične prehrane. Ker je klinična prehrana kot medicinska stroka razvita tudi pri nas, v tujini pa so tovrstni terminološki dokumenti že na voljo, želimo tudi v Sloveniji na podlagi konsenza oblikovati enotno terminologijo. Metode: Prispevek je osnovan na podlagi eksplicitnega terminološkega dogovora. K sodelovanju smo povabili obsežno skupino relevantnih slovenskih strokovnjakov s kliničnih, predkliničnih in drugih področij, ki so povezana z dejavnostjo klinične prehrane v medicini, pri oblikovanju pa je sodeloval tudi terminolog s področja medicine. Kot izhodišče smo izbrali terminološke smernice Evropskega združenja za klinično prehrano in presnovo ter ob njih upoštevali najnovejša strokovna priporočila za posamezne pojme. Avtorji so bili v stiku prek osebnih srečanj in elektronske pošte. Pri končnem oblikovanju konsenza je sodelovalo 42 avtorjev iz 19 slovenskih ustanov. Rezultati: Predstavljamo temeljne pojme, terminološke definicije in pripadajoče slovenske termine s področja klinične prehrane. Opredelili smo osnovne motnje prehranjenosti – podhranjenost, prekomerno hranjenost, neravnovesje mikrohranil in sindrom ponovnega hranjenja. Poleg tega smo opredelili tudi s prehranjenostjo povezana stanja – sarkopenijo in krhkost. Osnovne pojme smo podprli s kliničnim kontekstom, v katerem nastopajo. Zaključki: Poenoteno razumevanje osnovnih patoloških stanj, ki jih obravnava klinična prehrana, je izhodišče za nadaljnji razvoj stroke, poleg tega pa je podlaga tudi za prehransko obravnavo in učinkovito prehransko oskrbo

Terminologija klinične prehrane: Prehranska obravnava – presejanje prehranske ogroženosti in prehranski pregled

Izhodišča: Pomembno vlogo pri prehranski obravnavi imata tako presejanje prehranske ogroženosti kot prehranski pregled, na podlagi katerega lahko postavimo diagnozo motnje prehranjenosti ali s prehranjenostjo povezane motnje. Ocena posameznikovega prehranskega stanja, ki jo pridobimo s prehransko obravnavo, je namreč ključna za načrtovanje učinkovite prehranske oskrbe. Za razvoj področja je pomembno, da so vsi termini, ki se uporabljajo pri kliničnem delu, usklajeni. Taki terminološki dokumenti v mednarodnem prostoru že obstajajo, smiselni pa so tudi za slovenščino in naše okolje. Metode: Prispevek temelji na eksplicitnem terminološkem dogovoru skupine 42 relevantnih slovenskih strokovnjakov iz 19 slovenskih ustanov. Osnova oblikovanja terminoloških smernic je terminološki dokument Evropskega združenja za klinično prehrano in presnovo, pri čemer so bili upoštevani tudi novejši izsledki klinične prehrane. Rezultati: Predstavljeni so slovenski termini in terminološke definicije s področja klinične prehrane. Opredeljeni so osnovni pojmi s področja prehranske obravnave, ki je praviloma del medicinske obravnave. Predstavljena sta pojma prehranska ogroženost in presejanje prehranske ogroženosti, ob čemer so navedeni tudi različni presejalni testi za presejanje prehranskih motenj in s prehranjenostjo povezanih stanj. Podrobno so opredeljeni tudi prehranski pregled in njegovi sestavni deli. Zaključki: Tako presejanje prehranske ogroženosti kot prehranski pregled sta bistvena za diagnostično obravnavo v okviru klinične prehrane, poenoteno razumevanje terminologije pa omogoča primerno prepoznavo patoloških stanj pri bolnikih in pripravo ustreznega načrta prehranskih ukrepov

Ion chromatographic analysis of carbohydrates and amino acids

Biomolekule su iznimno važan dio svakoga organizma jer kontroliraju gotovo sve njegove aspekte, od strukture do životnih procesa i energije. Stoga posljednjih godina velik broj analitičara usmjerava pažnju upravo na unaprjeđenje postojećih i razvoj novih metoda i instrumentacije koja će omogućiti analizu biomolekula i dodatno razumijevanje njihovih uloga. Jedna od zastupljenijih metoda za analizu i odvajanje različitih nabijenih ili ionizirajućih molekula poput aminokiselina, proteina ili ugljikohidrata je ionska kromatografija. Ova metoda odlikuje se brojnim pogodnostima kao što su primjenjivost za simultanu analizu velikog broja molekula, lako povezivanje s drugim tehnikama (primjerice tehnikama detekcije), a u funkciji pročišćavanja omogućava dobivanje izrazito čistih proizvoda u relativno kratkom vremenu izvođenja. Velik napredak u analizi aminokiselina i ugljikohidrata bilo je uvođenje pulsne amperometrijske detekcije. Pregledom literature pronađene su brojne aplikacije za učinkovito i simultano razdvajanje i određivanje aminokiselina i ugljikohidrata anionskim izmjenjivačkim kolonama uz integriranu pulsnu amperometrijsku detekciju. Ovaj rad nudi pregled aktualnih metoda analize aminokiselina i ugljikohidrata s detaljnijim osvrtom na pronađene kromatografske aplikacije.Biomolecules are an extremely important part of every single organism since they control almost all of its aspects, from structure to metabolic processes and transformation of energy. Because of that, recent researches are driven towards the improvement of existing methods or development of the new ones, followed by development of instrumentation which will make analysis and understanding of biomolecules and the roles they have in organisms easier. Ion chromatography is one of the most intensively used methods in the analysis of biomolecules such as amino acids, proteins or carbohydrates. This method has a vast variety of advantages which includes simultaneous analysis of a huge number of molecules, simple linkage with other techniques (detection techniques, for example), and, in the purification mode, final products are extremely pure and obtained in short run time. Great progress has been made in the analysis of amino acids and carbohydrates when pulsed amperometric detection was introduced. By reviewing the literature, many applications have been found for the effective and simultaneous separation and determination of amino acids and carbohydrates on anion exchange columns with integrated pulsed amperometric detection. This manuscript is a review that summarises current methods for the analysis of amino acids and carbohydrates with emphasis on chromatographic techniques

Ion chromatographic analysis of carbohydrates and amino acids

Biomolekule su iznimno važan dio svakoga organizma jer kontroliraju gotovo sve njegove aspekte, od strukture do životnih procesa i energije. Stoga posljednjih godina velik broj analitičara usmjerava pažnju upravo na unaprjeđenje postojećih i razvoj novih metoda i instrumentacije koja će omogućiti analizu biomolekula i dodatno razumijevanje njihovih uloga. Jedna od zastupljenijih metoda za analizu i odvajanje različitih nabijenih ili ionizirajućih molekula poput aminokiselina, proteina ili ugljikohidrata je ionska kromatografija. Ova metoda odlikuje se brojnim pogodnostima kao što su primjenjivost za simultanu analizu velikog broja molekula, lako povezivanje s drugim tehnikama (primjerice tehnikama detekcije), a u funkciji pročišćavanja omogućava dobivanje izrazito čistih proizvoda u relativno kratkom vremenu izvođenja. Velik napredak u analizi aminokiselina i ugljikohidrata bilo je uvođenje pulsne amperometrijske detekcije. Pregledom literature pronađene su brojne aplikacije za učinkovito i simultano razdvajanje i određivanje aminokiselina i ugljikohidrata anionskim izmjenjivačkim kolonama uz integriranu pulsnu amperometrijsku detekciju. Ovaj rad nudi pregled aktualnih metoda analize aminokiselina i ugljikohidrata s detaljnijim osvrtom na pronađene kromatografske aplikacije.Biomolecules are an extremely important part of every single organism since they control almost all of its aspects, from structure to metabolic processes and transformation of energy. Because of that, recent researches are driven towards the improvement of existing methods or development of the new ones, followed by development of instrumentation which will make analysis and understanding of biomolecules and the roles they have in organisms easier. Ion chromatography is one of the most intensively used methods in the analysis of biomolecules such as amino acids, proteins or carbohydrates. This method has a vast variety of advantages which includes simultaneous analysis of a huge number of molecules, simple linkage with other techniques (detection techniques, for example), and, in the purification mode, final products are extremely pure and obtained in short run time. Great progress has been made in the analysis of amino acids and carbohydrates when pulsed amperometric detection was introduced. By reviewing the literature, many applications have been found for the effective and simultaneous separation and determination of amino acids and carbohydrates on anion exchange columns with integrated pulsed amperometric detection. This manuscript is a review that summarises current methods for the analysis of amino acids and carbohydrates with emphasis on chromatographic techniques

Ion chromatographic analysis of carbohydrates and amino acids

Biomolekule su iznimno važan dio svakoga organizma jer kontroliraju gotovo sve njegove aspekte, od strukture do životnih procesa i energije. Stoga posljednjih godina velik broj analitičara usmjerava pažnju upravo na unaprjeđenje postojećih i razvoj novih metoda i instrumentacije koja će omogućiti analizu biomolekula i dodatno razumijevanje njihovih uloga. Jedna od zastupljenijih metoda za analizu i odvajanje različitih nabijenih ili ionizirajućih molekula poput aminokiselina, proteina ili ugljikohidrata je ionska kromatografija. Ova metoda odlikuje se brojnim pogodnostima kao što su primjenjivost za simultanu analizu velikog broja molekula, lako povezivanje s drugim tehnikama (primjerice tehnikama detekcije), a u funkciji pročišćavanja omogućava dobivanje izrazito čistih proizvoda u relativno kratkom vremenu izvođenja. Velik napredak u analizi aminokiselina i ugljikohidrata bilo je uvođenje pulsne amperometrijske detekcije. Pregledom literature pronađene su brojne aplikacije za učinkovito i simultano razdvajanje i određivanje aminokiselina i ugljikohidrata anionskim izmjenjivačkim kolonama uz integriranu pulsnu amperometrijsku detekciju. Ovaj rad nudi pregled aktualnih metoda analize aminokiselina i ugljikohidrata s detaljnijim osvrtom na pronađene kromatografske aplikacije.Biomolecules are an extremely important part of every single organism since they control almost all of its aspects, from structure to metabolic processes and transformation of energy. Because of that, recent researches are driven towards the improvement of existing methods or development of the new ones, followed by development of instrumentation which will make analysis and understanding of biomolecules and the roles they have in organisms easier. Ion chromatography is one of the most intensively used methods in the analysis of biomolecules such as amino acids, proteins or carbohydrates. This method has a vast variety of advantages which includes simultaneous analysis of a huge number of molecules, simple linkage with other techniques (detection techniques, for example), and, in the purification mode, final products are extremely pure and obtained in short run time. Great progress has been made in the analysis of amino acids and carbohydrates when pulsed amperometric detection was introduced. By reviewing the literature, many applications have been found for the effective and simultaneous separation and determination of amino acids and carbohydrates on anion exchange columns with integrated pulsed amperometric detection. This manuscript is a review that summarises current methods for the analysis of amino acids and carbohydrates with emphasis on chromatographic techniques

Towards a morphology of cobalt nanoparticles: Size and strain effects

Cobalt nanoparticles with diameters of 8 nm have recently shown promising performance for biomedical applications. However, it is still unclear how the shape of cobalt clusters changes with size when reaching the nanoparticle range. In the present work, density functional theory calculations have been employed to compare the stabilities of two non-crystalline (icosahedron and decahedron) shapes, and three crystalline motifs (hcp, fcc, and bcc) for magic numbered cobalt clusters with up to 1500 atoms, based on the changes in the cohesive energies, coordination numbers, and nearest-neighbour distances arising from varying geometries. Obtained trends were extrapolated to a 104 size range, and an icosahedral shape was predicted for clusters up to 5500 atoms. Larger sized clusters adopt hcp stacking, in correspondence with the bulk phase. To explain the crystalline/non-crystalline crossovers, the contributions of the elastic strain density and twin boundary from the specimen surfaces to the cohesive energy of different motifs were evaluated. These results are expected to aid the design and synthesis of cobalt nanoparticles for applications ranging from catalysis to biomedical treatments

Binding modes of carboxylic acids on cobalt nanoparticles

Owing to their high saturation magnetisation, cobalt nanoparticles hold significant potential for the hyperthermia treatment of tumours. Covalent binding of carboxylic acids to the nanoparticles can induce biocompatibility, whilst also preventing the formation of surface oxides which reduce the magnetic properties of cobalt. Understanding the origin of the acid-metal interaction is key, yet probably the most experimentally challenging step, for the rational design of such entities. In this density functional theory study, we use static calculations to establish that a 57-atom Co cluster is the smallest model able to reproduce the adsorption behaviour of carboxylic acids, and ab initio metadynamics to obtain the structure and the free energy landscape for its interaction with valeric acid. Our simulations show that a bridging bidentate binding mode has a stronger affinity compared to monodentate binding, with energetically high transition barriers between the two. A chelate interaction mode of two carboxyl oxygen atoms can be formed as an intermediate. These results clarify the organic-inorganic interactions in the cobalt-acid system, providing a basis for the rational design of biocompatible metallic nanoparticles

A Tale of Two Proteases: M^Pro and TMPRSS2 as Targets for COVID-19 Therapies

Considering the importance of the 2019 outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resulting in the coronavirus disease 2019 (COVID-19) pandemic, an overview of two proteases that play an important role in the infection by SARS-CoV-2, the main protease of SARS-CoV-2 (MPro) and the host transmembrane protease serine 2 (TMPRSS2), is presented in this review. After summarising the viral replication cycle to identify the relevance of these proteases, the therapeutic agents already approved are presented. Then, this review discusses some of the most recently reported inhibitors first for the viral MPro and next for the host TMPRSS2 explaining the mechanism of action of each protease. Afterward, some computational approaches to design novel MPro and TMPRSS2 inhibitors are presented, also describing the corresponding crystallographic structures reported so far. Finally, a brief discussion on a few reports found some dual-action inhibitors for both proteases is given. This review provides an overview of two proteases of different origins (viral and human host) that have become important targets for the development of antiviral agents to treat COVID-19