A Ferrocene-Quinoxaline Derivative as a Highly Selective Probe for Colorimetric and Redox Sensing of Toxic Mercury(II) Cations

A new chemosensor molecule 3 based on a ferrocene-quinoxaline dyad recognizes mercury (II) cations in acetonitrile solution. Upon recognition, an anodic shift of the ferrocene/ferrocenium oxidation peaks and a progressive red-shift (Δλ = 140 nm) of the low-energy band, are observed in its absorption spectrum. This change in the absorption spectrum is accompanied by a colour change from orange to deep green, which can be used for a “naked-eye” detection of this metal cation

Investigation of Volatile Organic Compounds (VOCs) released as a result of spoilage in whole broccoli, carrots, onions and potatoes with HS-SPME and GC-MS

Vegetable spoilage renders a product undesirable due to changes in sensory characteristics. The aim of this study was to investigate the change in the fingerprint of VOC composition that occur as a result of spoilage in broccoli, carrots, onions and potatoes. SPME and GC-MS techniques were used to identify and determine the relative abundance of VOC associated with both fresh and spoilt vegetables. Although a number of similar compounds were detected in varying quantities in the headspace of fresh and spoilt samples, certain compounds which were detected in the headspace of spoilt vegetables were however absent in fresh samples. Analysis of the headspace of fresh vegetables indicated the presence of a variety of alkanes, alkenes and terpenes. Among VOCs identified in the spoilt samples were dimethyl disulphide and dimethyl sulphide in broccoli; Ethyl propanoate and Butyl acetate in carrots; 1-Propanethioland 2-Hexyl-5-methyl-3(2H)-furanone in onions; and 2, 3-Butanediol in potatoes. The overall results of this study indicate the presence of VOCs that can serve as potential biomarkers for early detection of quality deterioration and in turn enhance operational and quality control decisions in the vegetable industry

Conformational Bidentate Fluorescent Sensors for Small Halide Anions

Anions are involved in fundamental processes in all living things. Recognition, transport and concentration control of anions such as chloride, phosphate and sulfate is carried out by biological systems on a perpetual basis. Fluoride, nitrate and pertechnetate are potentially dangerous contaminants that can gain access to our water systems by various means. Fluorosis, toxicity due to high levels of fluoride in drinking water, is a serious human health concern in many parts of the world Synthetic chemists seek to mimic nature’s level of sophistication in designing and making chemosensors capable of determining the concentration of a target anion in any medium. Beginning with a review of anion sensor chemistry with a particular focus on developments over the past 15 years, this thesis documents research into novel molecular sensors that target the differential sensing of fluoride and chloride anions. The design of these sensors has focussed on an optical signalling event based on electronic changes on binding but in addition, by virtue of a significant change in structural conformation. Fluorescent molecules have been utilised and as such, fluorescence emission changes investigated in the presence of a variety of anions. Results and Discussion I outlines our conformational model and discusses the design, synthesis and sensory behaviour of phenyl(boronates). UV, electrochemical, fluorescence and NMR techniques are brought together to elucidate the response of this class of molecule to various anions. One example designed to fit our proposed model shows interesting and unusual fluorescence quenching response to chloride anion. In addition, the synthesis of a related carbamate species and a range of oxygen bridged boron macrocycles are reported. Results and Discussion II discloses our approaches to more synthetically demanding constructs, obeying the model but trying to overcome the challenges met previously. An interesting, highly selective ratiomeric response to fluoride is observed with an isolated target molecule. Fluoride binding behaviour of a previously unexamined sp2 boron centre is examined.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Ruthenium

Ruthenium is a precious metal not widely known to non-scientists. It is a target of much research, however. It is used in computer hard drives, the tips of fountain pens, and as a catalyst to purify car exhaust, among other uses. This book presents information and research on the properties and applications of ruthenium, including potential uses in phytochemical functions and anticancer activity

Biomimetic Radical Chemistry and Applications

The enormous importance of free radical chemistry for a variety of biological events, including ageing and inflammation, has attracted a strong interest in understanding the related mechanistic steps at the molecular level. Modelling the free radical chemical reactivity of biological systems is an important research area. When studying free-radical-based chemical mechanisms, biomimetic chemistry and the design of established biomimetic models come into play to perform experiments in a controlled environment that is suitably designed to be in strict connection with cellular conditions. This Special Issue gives the reader a wide overview of biomimetic radical chemistry, where molecular mechanisms have been defined and molecular libraries of products are developed to also be used as traces for the discovery of some relevant biological processes. Several subjects are presented, with 12 articles and 6 reviews written by specialists in the fields of DNA, proteins, lipids, biotechnological applications, and bioinspired synthesis, having “free radicals” as a common denominator

hAGT inhibitors as chemotherapy enhancers

[cat] La proteïna de reparació de l’ADN alquilguanina-ADN-O6-alquiltransferasa (hAGT) elimina productes d'alquilació en la posició O6 de les guanines, bloquejant la citotoxicitat dels agents alquilants i produint resistència a la quimioteràpia. Es considera rellevant com a marcador de pronòstic en càncer i representa una potencial diana terapèutica. L’objectiu a llarg termini d’aquesta tesi doctoral és trobar inhibidors de l’activitat d’hAGT per millorar l'efecte de la quimioteràpia en pacients amb càncer. En primer lloc, es va avaluar la capacitat de 10 compostos, potencials inhibidors d’h!GT, de formar un complexe amb hAGT utilitzant espectrometria de masses, i es va estudiar la seva toxicitat en cultius cel·lulars a través d'assajos de MTT i de formació de colònies. A continuació, es desenvolupen diferents mètodes per a la detecció de l’activitat d’hAGT, per a avaluar els potencials inhibidors d’aquesta proteïna in vitro. Dos d’aquests mètodes utilitzen el canvi conformacional que es produeix en l’aptàmer d’unió a la trombina (TBA) en introduir una O6-metilguanina, substracte d’hAGT, en una de les seves tètrades centrals. En el primer mètode es va emprar el TBA per generar un sensor de fluorescència incorporant un fluoròfor i un inhibidor de fluorescència a cadascun dels seus extrems. Aquest sensor permet la detecció de la disminució en la fluorescència deguda al canvi conformacional del TBA produït per l’activitat d’hAGT. Posteriorment, el canvi conformacional del TBA va permetre dissenyar un biosensor de l'activitat d'hAGT a nivell unimolecular sobre la superficie d’un origami d'ADN. La interacció del TBA amb la seva proteïna diana, l’alfa-trombina, es va seguir per AFM per detectar que l’estructura de G-quàdruplex metilada es restableix per la reparació d’hAGT. El tercer mètode es basa en la transferència de fluorescència al centre actiu d’h!GT degut a la reparació d’un oligonucleòtid que conté una guanina modificada amb un grup alquil marcat amb un fluoròfor. Amb aquest objectiu, es va portar a terme la síntesi química d’aquesta guanina modificada. En el marc d’una estada en la Universitat de Milà, es descriu l’estudi de nanopartícules funcionalitzades amb TBAs per a detectar una metilació en una guanina utilitzant espectroscòpia d’UV, DLS o MRI, amb l’objectiu de desenvolupar un nou assaig de l’activitat reparadora d’ADN d’hAGT.[eng] The O6-alkylguanine DNA alkyltransferase (hAGT or MGMT) is a DNA repair protein in charge of removing alkyl adducts from the O6 position of guanines, blocking their cytotoxic effects and playing an important role as a resistance mechanism to chemotherapy in cancer patients. For these reasons, it is considered relevant as a prognosis marker of cancer and represents a potential therapeutic target. Intense research efforts have been devoted to the identification of small molecules capable of inhibiting hAGT activity and enhancing the cytotoxic effect of the alkylating agents in tumour cells. In this doctoral thesis, we have explored 10 compounds with potential inhibitory activity against hAGT. The analysis by mass spectrometry (ESI-MS) confirmed the complex formation of hAGT with 5 of them (compounds 5, 6, 7, 8 and 9). MTT cytotoxicity studies in cell culture showed that 2 compounds (5 and 8) were non-toxic and showed enhancement of carmustine toxicity. This compounds were further analysed by colony formation assays, which confirmed that compound 8 was non-toxic at long-term experiments and exhibited a stimulation effect of carmustine. Compound 8 seem to be the best candidates for hAGT inhibition, as it forms a complex with hAGT and it enhances BCNU without being toxic in MTT and colony formation assays. Due to the lack of a consistent in vitro assay for the activity of hAGT, we have devoted part of this doctoral thesis to the search of bio and nanotechnologies to detect hAGT activity which enable the evaluation of potential inhibitors of the protein. Chapter 2 describes the development of a new fluorescence method using the conformational change of a DNA Gquadruplex, the thrombin binding aptamer (TBA), as a molecular beacon for the detection of hAGT activity and the development of new inhibitor compounds. The conformational change of TBA is further explored to develop a detection platform on DNA origami which allows de quantification of the repair activity of hAGT on a single molecules basis, through the direct visualization by AFM of the interaction of TBA-thrombin when its G-quadruplex structure is restored. In addition, this work reports the synthesis of guanine derivatives modified at position 6 and properly functionalized for their incorporation into double stranded oligonucleotides that are used for the development of another novel fluorescence methodology to evaluate hAGT activity and to assess potential inhibitors as enhancers of chemotherapy. Finally, during a short stay in the University of Milan, we have developed a new sensor to detect a methylation in TBA using three types of nanoparticles: AuNPs, SPIONs and AuSPIONs. AuSPIONs combine the features of the gold coating and the magnetic core, and exhibit similar performance as AuNPs and SPIONs in UV, DLS and MRI assays to detect thrombin and a single methylation in TBA. Ths results provide the basis for the development of a new straightforward method to study hAGT activity and to evaluate potential inhibitors

The synthesis and characterisation of inorganic and organic luminophores suitable for biomolecule conjugation

Inorganic transition metal complexes have been under extensive investigation for many years in supramolecular assemblies due to their favourable photophysical and redox properties including; absorbance and emission in the visible region of the spectrum, large stokes shifts, long lifetimes, intense luminescence, good photostability and useful photosensitising properties for photodynamic therapy. Their properties make them potentially very valuable biological probes but to date relatively little application of transition metals in this area have been made. This thesis focuses on a range of novel ruthenium and iridium luminophores, their bioconjugates and nanoparticle conjugates which were prepared for applications in cell imaging. A key aim of this thesis was the synthesis, characterisation and identification of novel bioconjugates suitable for applications in cellular imaging. Some preliminary studies of their application in cell imaging are also presented. Chapter 1 outlines how metal complexes have been used previously in cellular imaging and how conjugation of these transition metal complexes to biomolecules has lead to more targeted and improved applications in medical diagnostics, photodynamic therapy, cellular imaging and pharmaceutical drug delivery. Chapters 3 & 4 detail the synthesis and photophysical characterisation of a series of Raman and oxygen sensitive, water soluble and water insoluble ruthenium (II) and novel iridium (III) polypyridyl complexes suitable for biomolecule coupling. Following conjugation of these luminophores to gold nanoparticles in Chapter 3 and cell penetrating peptides in Chapter 5, the dye-conjugates were shown to transport efficiently across the cellular membrane of mammalian SP2 and CHO cells and locate throughout the cell’s organelles. Whereas, using confocal fluorescence microscopy, the parent complexes were shown not to internalise within the cellular structures. The inherent properties of the dyes, such as Raman and lifetime sensitivity, may then be used to determine pH and oxygen levels inside the cell. This could provide critical information for the early detection of certain diseases, as abnormal pH and oxygen levels are indicative of cancerous tumours. Furthermore, the generation of singlet oxygen following light absorption by the luminophores is known to cause additional cell apoptosis. Finally, Chapter 6 describes attempts to functionalise the nucleobase guanine with a fluorescent fluorescein molecule through a short and rigid linker. A range of synthetic techniques such as Suzuki coupling, Sonogashira coupling, click chemistry and Buchwald-Hartwig coupling were used in an effort to achieve this. Using DNA as a scaffold for the first time, the modified nucleoside may be incorporated into the sequence of DNA which may be surface immobilised. Thus, providing an efficient light harvesting supramolecular assembly for the conversion of solar energy into electrical potential