Quantum chemical study of tautomerization in select pharmaceuticals

Prototropička tautomerizacija je ravnotežna reakcija pomaka protona s kiselog centra molekule na bazični, uz istovremeni pomak π-elektrona u suprotnom smjeru. Molekule koje posjeduju -CH-C(=O)-NH- fragment postoje u tri tautomerna oblika: keto, enol i iminol. Među takvim molekulama nalazi se značajan broj lijekova. Tautomeri se međusobno razlikuju po fizikalno-kemijskim osobinama, stoga je karakterizacija tautomerne smjese važna za razumijevanje farmakokinetike i farmakodinamike lijekova, kao i za postupke proizvodnje i oblikovanja. Udio svakog tautomera u ravnotežnoj smjesi ovisi o njihovim relativnim stabilnostima. Gibbsova energija molekule može se odrediti in silico, koristeći računalne programe bazirane na zakonima kvantne mehanike. U ovom radu ispitane su stabilnosti tautomera 15 molekula farmaceutika. Keto oblik najstabilniji je u svim slučajevima. Iminolni oblik većine molekula dovoljno je stabilan kako bi se smatrao značajnim dijelom ravnotežne smjese, za razliku od enola čiji se udio zbog nestabilnosti može zanemariti. Supstituenti na amidnom dušiku i α-ugljiku utječu na energije tautomera: najjači su stabilizatori elektron-akceptorske skupine, aromatski sustavi i strukture koje omogućuju uspostavu produžene konjugacije. Stabilnost se može povećati i uspostavom intramolekulske vodikove veze. Ispitivani lijekovi koriste se u terapiji velikog broja pacijenata širom svijeta. Karakterizacija tautomera pomoći će u produbljivanju razumijevanja njihovih fizikalno-kemijskih osobina te u izgradnji srodnih lijekova poboljšanih svojstava.Prototropic tautomerization is an equilibrium reaction that includes a proton shift from the acidic centre of a molecule to the basic centre, with the simultaneous shift of π-electrons in the opposite direction. Molecules possessing the -CH-C(=O)-NH- fragment exist in three tautomeric forms: keto, enol and iminol. Among such molecules is a large number of pharmaceuticals. Tautomers differ in physico-chemical properties. The characterisation of the tautomeric equilibrium is thus important for the understanding of pharmacokinetics and pharmacodynamics of drugs, as well as for their manufacturing and formulation. The percentage of each tautomer in the equilibrium depends on their relative stabilities. The Gibbs energy of a molecule can be determined in silico, using computer programs based on the laws of quantum mechanics. In this thesis the stabilities of tautomers of 15 molecules were examined. Keto form is the most stable in all cases. Iminolic form of most molecules is stable enough to be considered a significant part of the tautomeric mix, while the enolic form is very unstable, so its presence can be deemed negligible. Substituents on the amidic nitrogen and the α-carbon affect the energies of tautomers: electron-accepting groups, aromatic structures and conjugated systems possess the strongest stabilizing effect. Stability of tautomers can also be increased by the formation of an intramolecular hydrogen bond. The analyzed pharmaceuticals are widely used for treatment of patients all over the world. Characterization of their tautomers will help increase the understanding of their physico-chemical properties and aid in design of related drugs with improved features

Fate and transformation of silver nanoparticles in different biological conditions

The exploitation of silver nanoparticles (AgNPs) in biomedicine represents more than one third of their overall application. Despite their wide use and significant amount of scientific data on their effects on biological systems, detailed insight into their in vivo fate is still lacking. This study aimed to elucidate the biotransformation patterns of AgNPs following oral administration. Colloidal stability, biochemical transformation, dissolution, and degradation behaviour of different types of AgNPs were evaluated in systems modelled to represent biological environments relevant for oral administration, as well as in cell culture media and tissue compartments obtained from animal models. A multimethod approach was employed by implementing light scattering (dynamic and electrophoretic) techniques, spectroscopy (UV–vis, atomic absorption, nuclear magnetic resonance) and transmission electron microscopy. The obtained results demonstrated that AgNPs may transform very quickly during their journey through different biological conditions. They are able to degrade to an ionic form and again reconstruct to a nanoparticulate form, depending on the biological environment determined by specific body compartments. As suggested for other inorganic nanoparticles by other research groups, AgNPs fail to preserve their specific integrity in in vivo settings

Precipitation at room temperature as a fast and versatile method for calcium phosphate/TiO2 nanocomposites synthesis

The constantly growing need for advanced bone regeneration materials has motivated the development of calcium phosphates (CaPs) composites with a different metal or metal-oxide nanomaterials and their economical and environmentally friendly production. Here, two procedures for the synthesis of CaPs composites with TiO2 nanoplates (TiNPl) and nanowires (TiNWs) were tested, with the immersion of TiO2 nanomaterials (TiNMs) in corrected simulated body fluid (c-SBF) and precipitation of CaP in the presence of TiNMs. The materials obtained were analyzed by powder X-ray diffraction, spectroscopic and microscopic techniques, Brunauer–Emmett–Teller surface area analysis, thermogravimetric analysis, dynamic and electrophoretic light scattering, and their hemocompatibility and ability to induce reactive oxygen species were evaluated. After 28 days of immersion in c-SBF, no significant CaP coating was formed on TiNMs. However, the composites with calcium-deficient apatite (CaDHA) were obtained after one hour in the spontaneous precipitation system. In the absence of TiNMs, CaDHA was also formed, indicating that control of the CaP phase formed can be accomplished by fine-tuning conditions in the precipitation system. Although the morphology and size of crystalline domains of CaDHA obtained on the different nanomaterials differed, no significant difference was detected in their local structure. Composites showed low reactive oxygen species (ROS) production and did not induce hemolysis. The results obtained indicate that precipitation is a suitable and fast method for the preparation of CaPs/TiNMs nanocomposites which shows great potential for biomedical applications

Implications for registry-based vaccine effectiveness studies from an evaluation of an immunization registry: A cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Population-based electronic immunization registries create the possibility of using registry data to conduct vaccine effectiveness studies which could have methodological advantages over traditional observational studies. For study validity, the base population would have to be clearly defined and the immunization status of members of the population accurately recorded in the registry. We evaluated a city-wide immunization registry, focusing on its potential as a tool to study pertussis vaccine effectiveness, especially in adolescents.</p> <p>Methods</p> <p>We conducted two evaluations – one in sites that were active registry participants and one in sites that had implemented an electronic medical record with plans for future direct data transfer to the registry – of the ability to match patients' medical records to registry records and the accuracy of immunization records in the registry. For each site, records from current pediatric patients were chosen randomly. Data regarding pertussis-related immunizations, clinic usage, and demographic and identifying information were recorded; for 11–17-year-old subjects, information on MMR, hepatitis B, and varicella immunizations was also collected. Records were then matched, when possible, to registry records. For records with a registry match, immunization data were compared.</p> <p>Results</p> <p>Among 350 subjects from sites that were current registry users, 307 (87.7%) matched a registry record. Discrepancies in pertussis-related data were common for up-to-date status (22.6%), number of immunizations (34.7%), dates (10.2%), and formulation (34.4%). Among 442 subjects from sites that planned direct electronic transfer of immunization data to the registry, 393 (88.9%) would have matched a registry record; discrepancies occurred frequently in number of immunizations (11.9%), formulation (29.1%), manufacturer (94.4%), and lot number (95.1%.) Inability to match and immunization discrepancies were both more common in subjects who were older at their first visit to the provider site. For 11–17-year-old subjects, discrepancies were also common for MMR, hepatitis B, and varicella vaccination data.</p> <p>Conclusion</p> <p>Provider records frequently could not be matched to registry records or had discrepancies in key immunization data. These issues were more common for older children and were present even with electronic data transfer. These results highlight general challenges that may face investigators wishing to use registry-based immunization data for vaccine effectiveness studies, especially in adolescents.</p

Mechanism of interaction of biothiols with silver and gold nanoparticles

Transformacije nanočestica zlata (AuNP) i srebra (AgNP) u biološkim sustavima utječu na njihov biološki identitet, ponašanje i biološke učinke. Zbog svojeg velikog afiniteta prema sumporu, AgNP i AuNP lako stupaju u interakcije s endogenim biotiolima, pa je razumijevanje takvih interakcija preduvjet njihove uspješne biomedicinske primjene. Cilj ove doktorske disertacije bio je utvrditi mehanizam interakcije i vezanja biotiola s AgNP i AuNP kombiniranom primjenom eksperimentalnih i računalnih metoda. Nanočestice su pripremljene metodom redukcije, te su karakterizirane obzirom na oblik, raspodjelu veličina, zeta potencijal i koloidnu stabilnost pomoću mikroskopskih i spektroskopskih tehnika. Direktna interakcija s biotiolima praćena je nuklearnom magnetskom rezonancijskom spektroskopijom, a primjenom kvantno-kemijskih i molekulsko-dinamičkih metoda potvrđen je pretpostavljeni mehanizam tih interakcija. Utvrđeno je da se prilikom interakcije biotiola s atomima Ag i Au na nanopovršini događa njihova oksidativna dimerizacija u disulfide. Mehanizam oksidativne dimerizacije odvija se u dva koraka: 1) oksidacija tiolne skupine u sulfensku kiselinu posredovana reaktivnim kisikovim vrstama i 2) reakcija tiola i sulfenske kiseline uz oslobađanje vode, katalizirana s Ag i Au. Nastali disulfidi adsorbiraju na površinu AgNP i AuNP putem nekovalentnih interakcija, u kojima sudjeluju sve njihove funkcionalne skupine. Izračunom energije vezanja potvrđena je spontanost adsorpcije i veći afinitet vezanja disulfida u odnosu na tiole. Stoga je konačni produkt interakcija metalnih površina s tiolima nastanak AgNP i AuNP obloženih disulfidima. Ova saznanja pridonose razumijevanju transformacija nanočestica u prisutnosti biotiola što je važno za procjenu njihovih bioloških učinaka i sigurnosti primjene u biomedicini.Transformations of gold and silver nanoparticles (AuNPs and AgNPs) impact their biological effects, behaviour and fate in the human body. Interaction of NPs with endogenous biothiols is one of the major events leading to those transformations, thus the understanding of their interplay is a prerequisite for biomedical applications of NPs. This study was conducted on a model system consisting of cysteine (CYS) or glutathione (GSH) and AgNPs or AuNPs, by combining experimental and theoretical approaches. NPs were prepared by the reduction method and their shape, size distribution, zeta potential and dissolution were determined by microscopy and spectroscopic techniques. Direct interaction of biothiols with Ag and Au was monitored during NP preparation by nuclear magnetic resonance spectroscopy, and the reaction mechanism and processes on the metal surface were determined by quantum-chemical and molecular dynamics methods. In the reaction mixture, simultaneously with the formation of nanoparticles, oxidative dimerization of biothiols occurs and disulphides bind to the nanoparticle surface. Mechanism of oxidative dimerization consists of two steps: 1) oxidation of the thiol group to sulfenic acid by reactive oxygen species, and 2) reaction of thiol with sulfenic acid involving the release of one water molecule (Ag and Au act as catalysts). Generated disulphides adsorb to the AgNP and AuNP surface through non-covalent interactions with participation from all functional groups. Binding energy calculations confirm the adsorption is spontaneous, and that disulphides bind with higher affinity compared to thiols. Thus, the final product of the interaction of metallic surfaces with thiols is the formation of disulphide-coated AgNPs and AuNPs. These findings contribute to the understanding of biotransformations of both biothiols and particles that are important for the application of nanoparticles in biomedicine

Mechanism of interaction of biothiols with silver and gold nanoparticles

Transformacije nanočestica zlata (AuNP) i srebra (AgNP) u biološkim sustavima utječu na njihov biološki identitet, ponašanje i biološke učinke. Zbog svojeg velikog afiniteta prema sumporu, AgNP i AuNP lako stupaju u interakcije s endogenim biotiolima, pa je razumijevanje takvih interakcija preduvjet njihove uspješne biomedicinske primjene. Cilj ove doktorske disertacije bio je utvrditi mehanizam interakcije i vezanja biotiola s AgNP i AuNP kombiniranom primjenom eksperimentalnih i računalnih metoda. Nanočestice su pripremljene metodom redukcije, te su karakterizirane obzirom na oblik, raspodjelu veličina, zeta potencijal i koloidnu stabilnost pomoću mikroskopskih i spektroskopskih tehnika. Direktna interakcija s biotiolima praćena je nuklearnom magnetskom rezonancijskom spektroskopijom, a primjenom kvantno-kemijskih i molekulsko-dinamičkih metoda potvrđen je pretpostavljeni mehanizam tih interakcija. Utvrđeno je da se prilikom interakcije biotiola s atomima Ag i Au na nanopovršini događa njihova oksidativna dimerizacija u disulfide. Mehanizam oksidativne dimerizacije odvija se u dva koraka: 1) oksidacija tiolne skupine u sulfensku kiselinu posredovana reaktivnim kisikovim vrstama i 2) reakcija tiola i sulfenske kiseline uz oslobađanje vode, katalizirana s Ag i Au. Nastali disulfidi adsorbiraju na površinu AgNP i AuNP putem nekovalentnih interakcija, u kojima sudjeluju sve njihove funkcionalne skupine. Izračunom energije vezanja potvrđena je spontanost adsorpcije i veći afinitet vezanja disulfida u odnosu na tiole. Stoga je konačni produkt interakcija metalnih površina s tiolima nastanak AgNP i AuNP obloženih disulfidima. Ova saznanja pridonose razumijevanju transformacija nanočestica u prisutnosti biotiola što je važno za procjenu njihovih bioloških učinaka i sigurnosti primjene u biomedicini.Transformations of gold and silver nanoparticles (AuNPs and AgNPs) impact their biological effects, behaviour and fate in the human body. Interaction of NPs with endogenous biothiols is one of the major events leading to those transformations, thus the understanding of their interplay is a prerequisite for biomedical applications of NPs. This study was conducted on a model system consisting of cysteine (CYS) or glutathione (GSH) and AgNPs or AuNPs, by combining experimental and theoretical approaches. NPs were prepared by the reduction method and their shape, size distribution, zeta potential and dissolution were determined by microscopy and spectroscopic techniques. Direct interaction of biothiols with Ag and Au was monitored during NP preparation by nuclear magnetic resonance spectroscopy, and the reaction mechanism and processes on the metal surface were determined by quantum-chemical and molecular dynamics methods. In the reaction mixture, simultaneously with the formation of nanoparticles, oxidative dimerization of biothiols occurs and disulphides bind to the nanoparticle surface. Mechanism of oxidative dimerization consists of two steps: 1) oxidation of the thiol group to sulfenic acid by reactive oxygen species, and 2) reaction of thiol with sulfenic acid involving the release of one water molecule (Ag and Au act as catalysts). Generated disulphides adsorb to the AgNP and AuNP surface through non-covalent interactions with participation from all functional groups. Binding energy calculations confirm the adsorption is spontaneous, and that disulphides bind with higher affinity compared to thiols. Thus, the final product of the interaction of metallic surfaces with thiols is the formation of disulphide-coated AgNPs and AuNPs. These findings contribute to the understanding of biotransformations of both biothiols and particles that are important for the application of nanoparticles in biomedicine

Mechanism of interaction of biothiols with silver and gold nanoparticles

Transformacije nanočestica zlata (AuNP) i srebra (AgNP) u biološkim sustavima utječu na njihov biološki identitet, ponašanje i biološke učinke. Zbog svojeg velikog afiniteta prema sumporu, AgNP i AuNP lako stupaju u interakcije s endogenim biotiolima, pa je razumijevanje takvih interakcija preduvjet njihove uspješne biomedicinske primjene. Cilj ove doktorske disertacije bio je utvrditi mehanizam interakcije i vezanja biotiola s AgNP i AuNP kombiniranom primjenom eksperimentalnih i računalnih metoda. Nanočestice su pripremljene metodom redukcije, te su karakterizirane obzirom na oblik, raspodjelu veličina, zeta potencijal i koloidnu stabilnost pomoću mikroskopskih i spektroskopskih tehnika. Direktna interakcija s biotiolima praćena je nuklearnom magnetskom rezonancijskom spektroskopijom, a primjenom kvantno-kemijskih i molekulsko-dinamičkih metoda potvrđen je pretpostavljeni mehanizam tih interakcija. Utvrđeno je da se prilikom interakcije biotiola s atomima Ag i Au na nanopovršini događa njihova oksidativna dimerizacija u disulfide. Mehanizam oksidativne dimerizacije odvija se u dva koraka: 1) oksidacija tiolne skupine u sulfensku kiselinu posredovana reaktivnim kisikovim vrstama i 2) reakcija tiola i sulfenske kiseline uz oslobađanje vode, katalizirana s Ag i Au. Nastali disulfidi adsorbiraju na površinu AgNP i AuNP putem nekovalentnih interakcija, u kojima sudjeluju sve njihove funkcionalne skupine. Izračunom energije vezanja potvrđena je spontanost adsorpcije i veći afinitet vezanja disulfida u odnosu na tiole. Stoga je konačni produkt interakcija metalnih površina s tiolima nastanak AgNP i AuNP obloženih disulfidima. Ova saznanja pridonose razumijevanju transformacija nanočestica u prisutnosti biotiola što je važno za procjenu njihovih bioloških učinaka i sigurnosti primjene u biomedicini.Transformations of gold and silver nanoparticles (AuNPs and AgNPs) impact their biological effects, behaviour and fate in the human body. Interaction of NPs with endogenous biothiols is one of the major events leading to those transformations, thus the understanding of their interplay is a prerequisite for biomedical applications of NPs. This study was conducted on a model system consisting of cysteine (CYS) or glutathione (GSH) and AgNPs or AuNPs, by combining experimental and theoretical approaches. NPs were prepared by the reduction method and their shape, size distribution, zeta potential and dissolution were determined by microscopy and spectroscopic techniques. Direct interaction of biothiols with Ag and Au was monitored during NP preparation by nuclear magnetic resonance spectroscopy, and the reaction mechanism and processes on the metal surface were determined by quantum-chemical and molecular dynamics methods. In the reaction mixture, simultaneously with the formation of nanoparticles, oxidative dimerization of biothiols occurs and disulphides bind to the nanoparticle surface. Mechanism of oxidative dimerization consists of two steps: 1) oxidation of the thiol group to sulfenic acid by reactive oxygen species, and 2) reaction of thiol with sulfenic acid involving the release of one water molecule (Ag and Au act as catalysts). Generated disulphides adsorb to the AgNP and AuNP surface through non-covalent interactions with participation from all functional groups. Binding energy calculations confirm the adsorption is spontaneous, and that disulphides bind with higher affinity compared to thiols. Thus, the final product of the interaction of metallic surfaces with thiols is the formation of disulphide-coated AgNPs and AuNPs. These findings contribute to the understanding of biotransformations of both biothiols and particles that are important for the application of nanoparticles in biomedicine

Lamellarity-Driven Differences in Surface Structural Features of DPPS Lipids: Spectroscopic, Calorimetric and Computational Study

Although single-lipid bilayers are usually considered models of eukaryotic plasma membranes, their research drops drastically when it comes to exclusively anionic lipid membranes. Being a major anionic phospholipid in the inner leaflet of eukaryote membranes, phosphatidylserine-constituted lipid membranes were occasionally explored in the form of multilamellar liposomes (MLV), but their inherent instability caused a serious lack of efforts undertaken on large unilamellar liposomes (LUVs) as more realistic model membrane systems. In order to compensate the existing shortcomings, we performed a comprehensive calorimetric, spectroscopic and MD simulation study of time-varying structural features of LUV made from 1,2-dipalmitoyl-sn-glycero-3-phospho-L-serine (DPPS), whereas the corresponding MLV were examined as a reference. A substantial uncertainty of UV/Vis data of LUV from which only Tm was unambiguously determined (53.9 ± 0.8 °C), along with rather high uncertainty on the high-temperature range of DPPS melting profile obtained from DSC (≈50–59 °C), presumably reflect distinguished surface structural features in LUV. The FTIR signatures of glycerol moiety and those originated from carboxyl group serve as a strong support that in LUV, unlike in MLV, highly curved surfaces occur continuously, whereas the details on the attenuation of surface features in MLV were unraveled by molecular dynamics