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We derived a theory of biomolecule binding to the surface of Aun clusters and of the Au plane based on the hard soft acid base (HSAB) principle and the free electron metallic surface model. With the use of quantum mechanical calculations, the chemical potential (μ) and the chemical hardness (η) of the biomolecules are estimated. The effect of the gold is introduced via the empirical value of the gold chemical potential (−5.77 eV) as well as by using the expression (modified here) for the chemical hardness (η). The effect of an aqueous environment is introduced by means of the ligand molecular geometry influenced by the PCM field. This theory allows for a fast and low-cost estimation of binding biomolecules to the AuNPs surface. The predicted binding of thiolated genistein and abiraterone to the gold surface is about 20 kcal/mol. The model of the exchange reaction between these biomolecules and citrates on the Au surface corresponds well with the experimental observations for thiolated abiraterone. Moreover, using a model of the place exchange of linear mercaptohydrocarbons on 12-mercaptododecane acid methyl ester bound to the Au surface, the present results reflect the known relation between exchange energy and the size of the reagents. [ABSTRACT FROM AUTHOR]

A simple linear relationship between the functionalization reaction energies for the exohedral monovalent addition on the surface of an ideal, infinitely long, single-walled carbon nanotube (SWCNT) and the reciprocal SWCNT radius has been derived employing the hard-soft acid basis principle and the tight binding model. The slope of the derived linear relationship is a function of the effective number of valence electrons involved in the functionalization reaction. The intercept of the derived linear relationship, equal to the reaction energies on a planar graphite surface, is a function of the electrophilicity of the monovalent addend and of the condensed Fukui function of its reacting atom. The theoretical predictions of this simple formula are coherent with the computational density functional theory data reported in the literature. [ABSTRACT FROM AUTHOR]

Based on the free electron metallic disc model, the derivation of a simple expression for evaluation of the Fukui function for the molecular models of polycyclic aromatic hydrocarbons (PAHs) of the general formula $$ {\rm{C}}_{{6{n}}^{2}} {\rm{H}}_{6{n}} $$ was described. We also investigated the functionalization energy with OH radicals for the molecular models of PAHs ( n = 1-6). Our metallic disc model-based functionalization reaction energy was in agreement with the DFT:B3LYP/6-31G( d) calculated values. Asymptotic values of the functionalization energies ( $$ {{n}} \to \infty $$) were predicted to be −30.1 ± 0.1 and −8.7 ± 0.1 kcal/mol for the external and internal border carbon atoms, respectively. [ABSTRACT FROM AUTHOR]

Quantum mechanical, molecular mechanics and molecular dynamics (MD) methods were used to investigate initial steps of 2'-deoxyuridine-5'-monophosphate (dUMP) methylation catalysed by the thymidylate synthase (TS) enzyme. The amino acid residues surrounding the active site within a 10 Å radius sphere were modelled with the combined quantum mechanical (B3LYP/LANL2DZ) and molecular mechanics ONIOM double-layer method. The results indicated the initial nucleophilic attack of Cys146 on dUMP to be concerted with formation of a hydrogen bond to the oxygen O4 of dUMP. Moreover, the proton in the vicinity of the O4 atom appears to act as a 'proton switch': if a proton is present near O4, it stabilises the S(Cys146)-C6(dUMP) sulphur-carbon bond, but if it is absent, the sulphur-carbon bond does not form. If the O4 oxygen is replaced by sulphur atom, the 'switch effect' does not occur. The suggested correlation between the strength of hydrogen bond involving O4 oxygen and the ability of dUMP to form bonds at C6 corresponds well to the crystal structures of TS complexes available in the Protein Data Bank. In the vast majority of crystal structures, the presence of the S(Cys146)-C6(dUMP) bond was coupled with the presence of hydrogen bond between the dUMP O4 atom and the conserved Asn177. The 'proton switch' hypothesis is supported also by the results of MD studies of TS binary complexes, suggesting that average distance separating S(Cys146) and C6(dUMP) becomes distinctly shorter in the presence of hydrogen bonding between Asn177 and O4. [ABSTRACT FROM AUTHOR]

Abstract: Switchable materials have tremendous potential for application in sensor development that could be applied to many fields. We are focusing on emerging area of wireless sensor networks due to the potential impact of this concept in society. Spiropyran-based sensors are probably the most studied type of photoswitchable sensing devices. They suffer from many issues but photofatigue, insufficient selectivity and lack of sensitivity are probably the most important characteristics that hinder their wider application. Here, we are address these issues and demonstrate that covalent attachment of modified spiropyran into a polymeric film significantly reduces photodegradation. The observed signal loss after 12th cycle of switching between the spiropyran and merocyanine forms is only about 27% compared to the loss of 57% of the initial signal in an equivalent experiment based on non-immobilized spiropyran. This has enabled us to demonstrate at least five reversible cycles of detection of an ion of interest (in our case H+) with minimal signal loss. Furthermore, we demonstrate that the sensitivity can be increased by incorporation of additional binding groups in the parent spiropyran molecule. Using molecular modelling to calculate the relevant bond lengths as a measure of interaction between MC and H+, the calculated increase of H-bond strength is approximately an order of magnitude for a derivative containing a methoxy group incorporated in the o-position of the parent spiropyran in comparison to the equivalent unsubstituted phenol. This theoretical result was found to correspond very well with experimental observation. As a result, we have increased the sensitivity to H+ by approximately one order of magnitude. [Copyright &y& Elsevier]

Cancer is one of the leading causes of morbidity and mortality worldwide and nanotechnology has a significant potential to enhance the therapeutic and diagnostic performance of anti-cancer agents. Our work offers a simple and feasible strategy for thiocompound nanomedicines to be used in cancer therapy. Novel gold nanoparticles conjugated with thioabiraterone (AuNP-S-AB) were synthesized and significant new analytical methodologies were developed for their characterization by UV–Vis, TEM, IR, NMR and TGA. Our synthetic approach was based on the ligand exchange of citrates to thioabiraterone on gold nanoparticles. The average particle size of AuNP-S-AB was 14.5 nm with a spherical shape. The identity of thioabiraterone on the gold nanoparticles was proved by NMR and IR spectroscopy. The coverage of the gold nanoparticles with 40.9% (m/m) thioabiraterone was calculated from a TGA analysis. Molecular interactions between the thiol group of thioabiraterone and gold nanoparticles were evaluated through a combined experimental and theoretical study using the density functional theory (DFT). Additionally, an experiment conducted on hepatocytes or human prostate epithelial cells proved that newly synthesized thiol forms of abiraterone, as well as AuNP-S-AB, are more biocompatible than abiraterone. Our proposed idea of delivering abiraterone with our newly designed AuNP-S-AB may constitute a promising and novel prospect in cancer therapy. [ABSTRACT FROM AUTHOR]