Savitvarkiai monosluoksniai suteikia metalų paviršiams norimas savybes ir plačiai taikomi elektronų pernašos tyrimuose, konstruojant (bio)jutiklius, biotechnologinius bei fotoelektroninius procesus. Teigiamo krūvio monosluoksniai naudojami kuriant anijonų jutiklius ir (bio)technologinius procesus su adsorbuotomis neigiamo krūvio makromolekulėmis. Darbe buvo susintetinta bifunkcinė molekulė su galinėmis tiolio ir piridinio grupėmis, suformuotas monosluoksnis ir ištirtos jo struktūrinės ir funkcinės savybės. Pagrindiniai darbo tikslai buvo ištirti N-(6-merkapto)heksilpiridinio (MHP) adsorbuoto ant Au ir Ag elektrodų struktūrą ir nustatyti monosluoksnio sąveikos su neorganiniais anijonais, dodecilsulfato anijonu ir grafeno oksidu dėsningumus. Naudojant paviršiaus sustiprintos Ramano spektroskopijos, kvantų chemijos skaičiavimo ir izotopinio pakeitimo metodus nustatyti MHP struktūros ir orientacijos elektrodo atžvilgiu Ramano sklaidos žymenys. Tiriant juostų intensyvumo priklausomybes nuo potencialo ir žadinančios spinduliuotės bangos ilgio parodyta, kad Au/MHP sistemoje pasireiškia krūvio pernešimo Ramano spektrų stiprinimo mechanizmas. Nustatyta, kad adsorbuotų neorganinių anijonų pilnai simetrinio virpesio dažnis sumažėja lyginant su tirpalo spektru ir tas pokytis koreliuoja su Gibso dehidracijos energija. Parodyta, kad MHP pritraukia grafeno oksidą. Nustatyta, kad grafeno oksido C-C ryšio ilgis ir elektroninė struktūra gali būti keičiama, keičiant potencialą. / Self-assembled monolayers provide possibility of changing metal surface properties in controllable manner and are widely used in studies of electron transfer, construction of (bio)sensors, and biotechnological and photoelectronic processes. Positively charged monolayers are valuable in development of sensors for anions and (bio)technological processes with adsorbed negatively charged macromolecules. In this work the structural and functional properties of monolayer formed from synthesized molecule with terminal thiol and pyridinium groups have been studied. The main tasks were to assess the structure of N-(6-mercapto)hexylpyridinium (MHP) on Ag and Au electrodes, and to determine the peculiarities of interaction with inorganic anions, dodecylsulfate, and graphene oxide. Based on surface enhanced Raman spectroscopy (SERS), quantum chemical calculations, and isotopic substitution studies, the Raman marker bands for structure and orientation of MHP have been evaluated. Dependence of SERS intensity on potential and excitation wavelength has revealed the operation of charge transfer Raman enhancement mechanism. It was found that the frequency of symmetric stretching mode of adsorbed ions decreases comparing with solution value and the extent of the shift correlates with the Gibbs dehydration energy. Adsorption of graphene oxide at MHP monolayer has been demonstrated. The electronic structure and length of C-C bonds of graphene oxide was found to be altered by the potential.

Self-assembled monolayers provide possibility of changing metal surface properties in controllable manner and are widely used in studies of electron transfer, construction of (bio)sensors, and biotechnological and photoelectronic processes. Positively charged monolayers are valuable in development of sensors for anions and (bio)technological processes with adsorbed negatively charged macromolecules. In this work the structural and functional properties of monolayer formed from synthesized molecule with terminal thiol and pyridinium groups have been studied. The main tasks were to assess the structure of N-(6-mercapto)hexylpyridinium (MHP) on Ag and Au electrodes, and to determine the peculiarities of interaction with inorganic anions, dodecylsulfate, and graphene oxide. Based on surface enhanced Raman spectroscopy (SERS), quantum chemical calculations, and isotopic substitution studies, the Raman marker bands for structure and orientation of MHP have been evaluated. Dependence of SERS intensity on potential and excitation wavelength has revealed the operation of charge transfer Raman enhancement mechanism. It was found that the frequency of symmetric stretching mode of adsorbed ions decreases comparing with solution value and the extent of the shift correlates with the Gibbs dehydration energy. Adsorption of graphene oxide at MHP monolayer has been demonstrated. The electronic structure and length of C-C bonds of graphene oxide was found to be altered by the potential. / Savitvarkiai monosluoksniai suteikia metalų paviršiams norimas savybes ir plačiai taikomi elektronų pernašos tyrimuose, konstruojant (bio)jutiklius, biotechnologinius bei fotoelektroninius procesus. Teigiamo krūvio monosluoksniai naudojami kuriant anijonų jutiklius ir (bio)technologinius procesus su adsorbuotomis neigiamo krūvio makromolekulėmis. Darbe buvo susintetinta bifunkcinė molekulė su galinėmis tiolio ir piridinio grupėmis, suformuotas monosluoksnis ir ištirtos jo struktūrinės ir funkcinės savybės. Pagrindiniai darbo tikslai buvo ištirti N-(6-merkapto)heksilpiridinio (MHP) adsorbuoto ant Au ir Ag elektrodų struktūrą ir nustatyti monosluoksnio sąveikos su neorganiniais anijonais, dodecilsulfato anijonu ir grafeno oksidu dėsningumus. Naudojant paviršiaus sustiprintos Ramano spektroskopijos, kvantų chemijos skaičiavimo ir izotopinio pakeitimo metodus nustatyti MHP struktūros ir orientacijos elektrodo atžvilgiu Ramano sklaidos žymenys. Tiriant juostų intensyvumo priklausomybes nuo potencialo ir žadinančios spinduliuotės bangos ilgio parodyta, kad Au/MHP sistemoje pasireiškia krūvio pernešimo Ramano spektrų stiprinimo mechanizmas. Nustatyta, kad adsorbuotų neorganinių anijonų pilnai simetrinio virpesio dažnis sumažėja lyginant su tirpalo spektru ir tas pokytis koreliuoja su Gibso dehidracijos energija. Parodyta, kad MHP pritraukia grafeno oksidą. Nustatyta, kad grafeno oksido CC ryšio ilgis ir elektroninė struktūra gali būti keičiama, keičiant potencialą.

Les propriétés d'une nouvelle classe de chimie de surface basée sur les monocouches auto-assemblées de liquides ioniques (ILs-SAMs), ont été étudiées pour une utilisation dans la construction de biocapteurs basés sur la résonance des plasmons de surface (SPR). Les biocapteurs sont utiles pour détecter des biomolécules spécifiques dans une matrice biologique complexe. Cependant, le signal analytique de la biomolécule spécifique peut être masqué par l’adsorption non spécifique de la matrice biologique, produisant une réponse faussement positive. Par ailleurs, l'activité des récepteurs moléculaires est souvent réduite par des techniques d'immobilisation chimique. Ainsi, il est essentiel de déterminer une surface idéale pour la préparation de biocapteurs. Les liquides ioniques sont bien connus pour favoriser l'activité des récepteurs moléculaires et cette étude enquête si cette propriété importante peut se traduire sur des capteurs SPR. Différents liquides ioniques ont été utilisés pour former des monocouches auto-assemblées sur une surface d'or. Les ILs-SAMs sont tous basés sur les sels de mercapto-(chaîne alkyle)nCH2-méthylimidazolium avec différentes chaînes alkyles (n = 3, 6, 9, 12) et différents contre-anions (Br-, BF4-, PF6-, NTf2-). Des études cinétiques de l'adsorption non spécifique de sérum bovin ont été réalisées sur des capteurs SPR avec un instrument construit sur mesure, basé sur l'interrogation des longueurs d’ondes SPR sur un prisme d’inversion d’image (dove). Par la suite, l’anti-IgG de chèvre sélective à l’IgG humain a été utilisé en tant que modèle pour la confection de biocapteurs sur les ILs-SAMs. En solution, il est possible d’effectuer des échanges du contre-anion des liquides ioniques pour un contre-anion de plus en plus hydrophobe. Cependant, l’échange inverse, soit vers des anions de plus en plus hydrophile, s’avère impossible. Toutefois, il a été observé par les travaux présentés dans ce mémoire, que les liquides ioniques immobilisés sur une surface d'or ont la capacité d'échanger leurs contre-anions réversiblement, procurant une méthode simple de moduler leurs propriétés physico-chimiques. Ce phénomène a été observé par la mesure d’angles de contacts et par les techniques spectroscopiques de l’infrarouge moyen (mid-IR), des photoélectrons de rayon-X (XPS) et par la diffusion Raman exaltée par les surfaces (SERS) ii ainsi que par la spectrométrie de masse (MS). La connaissance des propriétés d’échange d’anion est importante pour prédire le comportement de ces surfaces de liquides ioniques dans les tampons et fluides biologiques. / The properties of a novel class of surface chemistry based on ionic liquid self-assembled monolayers (IL-SAM) were investigated for use with surface plasmon resonance (SPR) biosensors. Biosensors are useful to detect specific biomolecules in a complex biological matrix. However, the analytical signal of a specific biomolecule can be masked by nonspecific adsorption of the biological matrix, resulting in a false positive response. Moreover, the activity of molecular receptors is often reduced by current immobilization chemistry. Thus, it is essential to determine an ideal surface for the preparation of biosensors. Ionic liquids are well-known to promote the activity of molecular receptors and this study investigates if this important property translates to SPR sensors. Different ionic liquids were used to form self-assembled monolayers on a gold surface. IL-SAM were based on mercapto(alkyl chain)n methylimidazolium salts with different alkyl chain (n = 3, 6, 9, 12) and counter anions (Br-, BF4-, PF6-, NTf2-). Kinetic studies of the nonspecific adsorption of bovine serum were carried on SPR sensors with a custom built instrument based on wavelength interrogation SPR on a dove prism. Thereafter, anti-goat IgG selective to human IgG was used as a model for biosensor employing ILs-SAM surface chemistry. Exchange of counter anion of ionic liquids was believed impossible for most hydrophobic counter anions. However, it was observed that ionic liquids immobilized on a gold surface have the ability to exchange their counter anions reversibly, allowing a simple method to modulate their physico-chemical properties. This phenomenon was observed by contact angle technique and by attenuated total reflectance mid-infrared (ATR mid-IR), X-ray photoelectron spectroscopy (XPS), surface enhanced raman spectroscopy (SERS) and mass spectrometry (MS). Better understanding of the anion exchange properties is crucial in predicting the behaviour of IL-SAM in presence of biological buffers and fluids.

Endocytosis is one of the most fundamental mechanisms by which the cell communicates with its surrounding. Specific signals are transduced through the cell membrane by a complex interplay between proteins and lipids. Clathrin depended endocytosis is one of important signalling pathways which leads to budding of the plasmalemma and a formation of endosomes. The FCHo2 is an essential protein at the initial stage of the this process. In is a membrane binding protein containing BAR (BIN, Amphiphysin, Rvs) domain which is responsible for a membrane binding. Although numerous valuable work on BAR proteins was published recently, the mechanistic description of a BAR domain functionality is missing. In present work we applied in vitro systems in order to gain knowledge about molecular basis of the activity of the FCHo2 BAR domain. In our studies we used supported lipid bilayers (SLBs) and lipid monolayers as s model membrane system. The experiments were carried out with a minimal number of components including the purified FCHo2 BAR domain. Using SLBs we showed that the BAR domain can bind to entirely flat bilayers. We also demonstrated that these interactions depend on the negatively charged lipid species incorporated in the membrane. We designed an assay which allows to quantify the membrane tubulation. We found out that the interaction of the FCHo2 BAR domain with the lipid membrane is concentration dependent. We showed that an area of the bilayer deformed by the protein depends on the amount of the used BAR domain. In order to study the relation between the mobility of lipids and the activity of FCHo2 BAR domain we designed a small-volume monolayer trough. The design of this micro-chamber allows for the implementation of the light microscopy. We demonstrated that the measured lipid diffusion in the monolayer by our new approach is in agreement with literature data. We carried out fluorescence correlation spectroscopy (FCS) experiments at different density of lipids at the water-air interface.We showed that the FCHo2 BAR domain binding affinity is proportional to the mean molecular area (MMA). We additionally demonstrated that the increased protein binding is correlated with the higher lipid mobility in the monolayer. Additionally, by curing out high-speed atomic force microscopy (hsAFM) we acquired the structural information about FCHo2 BAR domains orientation at the membrane with a high spatio-temporal resolution. Obtained data indicate the BAR domains interact witheach other by many different contact sites what results in a variety of protein orientations in a protein assemble.

This critical review summarizes recent developments in the fabrication of patterned polymer brushes. As top-down lithography reaches the length scale of a single macromolecule, the combination with the bottom-up synthesis of polymer brushes by surface-initiated polymerization becomes one main avenue to design new materials for nanotechnology. Recent developments in surface-initiated polymerizations are highlighted along with diverse strategies to create patterned polymer brushes on all length scales based on irradiation (photo- and interference lithography, electron-beam lithography), mechanical contact (scanning probe lithography, soft lithography, nanoimprinting lithography) and on surface forces (capillary force lithography, colloidal lithography, Langmuir–Blodgett lithography) (116 references). / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

>Magister Scientiae - MSc / Glucose oxidase (GOx) and horseradish peroxidase (HRP) are important enzymes for the development of amperometric enzyme linked immunosensors. The selectivity of each enzyme towards its analyte deepens its importance in determining the sensitivity of the resultant immunosensor. In designing immunosensors that have customized transducer surfaces, the incorporation with FAD and iron based enzymes ensures that electron kinetics remains optimal for electrochemical measurement. Various different immobilization strategies are used to produce response signals directly proportional to the concentration of analyte with minimal interferences. The combination of self-assembled monolayers and supramolecular chemistry affords stability and simplicity in immunosensor design. In this work, two electrochemical strategies for the detection of human chorionic gonadotropin(hCG) is presented. This involves the modification of a gold surface with a thiolated β-cyclodextrin epichlorohydrin polymer (βCDPSH) to form a supramolecular inclusion complex with ferrocene (Fc)-functionalised carboxymethyl cellulose polymer (CMC). Cyclic voltammetry indicated that ferrocene is in close proximity to the electrode surface due to the supramolecular complex formed with βCDPSH. Furthermore, strategy (a) for the detection of hCG used α-antihCG labelled (HRP) as reporter conjugate. Strategy (b) maintained the CMC bifunctionalised with Fc and recognition antibody for hCG hormone. However, the system was functionalised with a HRP enzyme and detection is done by using GOx reporter conjugates for in situ production of hydrogen peroxide. The reduction of H2O2 was used for the amperometric detection of hCG by applying a potential of 200 mV. The sensitivity and limit of detection of both strategies were calculated from calibration plots. For strategy (a) the LOD was found to be 3.7283 ng/mL corresponding to 33.56 mIU/mL and a sensitivity of 0.0914 nA ng-1 mL-1. The corresponding values for strategy (b) are 700 pg/mL (6.3 mIU/mL) and 0.94 nA ng-1 mL-1.

Submitted by TIAGO AZEVEDO BENITES null (tiagoazb@gmail.com) on 2017-10-09T17:59:58Z No. of bitstreams: 1 Tese Tiago.pdf: 5384805 bytes, checksum: 86cf0d44920d96e8154badd25a07c674 (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-10-09T19:38:54Z (GMT) No. of bitstreams: 1 benites_ta_dr_araiq.pdf: 5384805 bytes, checksum: 86cf0d44920d96e8154badd25a07c674 (MD5) / Made available in DSpace on 2017-10-09T19:38:54Z (GMT). No. of bitstreams: 1 benites_ta_dr_araiq.pdf: 5384805 bytes, checksum: 86cf0d44920d96e8154badd25a07c674 (MD5) Previous issue date: 2017-09-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Dentro da eletroquímica, o estudo de reações de transferência de elétrons (TE) pode ser explorado por meio de eletrodos de ouro modificados com monocamadas auto-organizadas (SAMs), visto que elas são capazes de modificar as propriedades físico-químicas superficiais e controlar a cinética de TE. Este trabalho investigou as reações de TE em eletrodos de ouro modificados com SAMs eletroativas. Especificamente, foi estudado a cinética de TE em SAMs de 11-ferrocenil-undecanotiol sobre superfícies de ouro, por meio de análise de voltametria cíclica e espectroscopia de impedância/capacitância eletroquímica (EIE/ECE). Por meio dessas técnicas foi possível estimar variáveis como a densidade de estados redox (aproximadamente 3,4×〖10〗^14 estados cm-2 próximos aos valores reportados na literatura), de capacitância eletroquímica ou redox (137(±9) μF 〖cm〗^(-2)), a constante cinética de transferência de elétrons em 1,05×〖10〗^4 s^(-1) similares às reportadas por Creager, além da estimativa da energia de reorganização de Marcus (λ) em torno de 1,0 eV, valores similares a outros já previamente estimados para funcionalizações de SAMs eletroativas. Expandiram-se essas análises por meio da imobilização de complexos eletroativos de Bis(2,2′-bipiridina)-(5-Aminofenantrolina)rutênio bis(hexafluorofosfato) sobre superfícies de Au, por síntese orgânica com tióis ancoradores de diferentes cadeias (cisteína e 3-ácido carboxílico-6-mercaptopiridina), utilizando reação de ativação com DIC/HOBt em acetonitrila. Neste caso, obteve-se uma densidade de estados redox de cerca de 8,9×〖10〗^14 estados cm-2 e 9,3×〖10〗^14 estados cm-2, além de uma constante cinética de 2,6×〖10〗^3 s^(-1) e 1,07×〖10〗^3 s^(-1) para as abordagens I (3-ácido carboxílico-6-mercaptopiridina) e II (Cisteína) respectivamente. Resultados sugeriram uma maior capacidade das moléculas ancoradoras compostas de anel piridinico (abordagem I) na condução de carga quando comparados com a abordagem II, o que foi posteriormente confirmado por análise de condutância em que a abordagem I apresentou G=6×〖10〗^(-3) S contra G=2×〖10〗^(-3) S da abordagem II. Este trabalho apresentou uma abordagem teórico-experimental que relaciona as componentes físico-químicas quânticas através de uma nova perspectiva baseada nos estudos teóricos de Marcus-Buttiker e em análises experimentais centradas na capacitância eletroquímica. / In electrochemistry, the study of electron transfer reactions (TE) can be explored using Au electrodes modified with self-assembled monolayers (SAMs), since they are able to modify the physicochemical properties of electrodes surface and control the TE kinetics. This work investigated TE reactions on Au electrodes modified with SAMs. Specifically, TE kinetics were studied using 11-ferrocenyl-undecanethiol SAMs on Au surfaces by means of cyclic voltammetry and electrochemical impedance/capacitance spectroscopy (EIS/ECS) analysis. By means of these techniques, it was possible to estimate variables such as the density of redox states (approximately 3.4 × 1014 states per cm-2 , near the reported results in the literature), electrochemical or redox capacitance (137(±9) �� ��−2 ), the kinetic electron transfer constant at 1.05 × 104 � −1 similar to those reported by Creager, in addition to the estimation of the Marcus´ reorganization energy (�) of around 1.0 eV, value similar to others already previously estimated for functionalization of electroactive SAMs. These analyzes were expanded by immobilization of Bis(2,2'-bipyridine)-(5-Aminophenanthroline)ruthenium-bis (hexafluorophosphate) electroactive complexes on Au surfaces by organic synthesis with anionic thiols of different chains (cysteine and 3-carboxylic acid-6-mercaptopyridine), using activation reaction with DIC/HOBt in acetonitrile. In this case, a redox state density of about 8.9 × 1014 states cm-2 and 9.3 × 1014 states cm-2 , in addition to a kinetic constant of 2.6 × 103 � −1 and 1.07 × 103 � −1 to I (3-carboxylic acid-6- mercaptopyridine) and II (Cysteine) approaches, respectively, were used in the present study. Results suggesting a higher capacity of the pyridinium ring compound anchoring molecules (I approach) in charge conduction when compared to the II approach, which was later confirmed by conductance analysis: the I approach presented � = 6 × 10−3 � and � = 2 × 10−3 � for approach II. This work presented a theoretical-experimental approach relating the quantum physicochemical components through a new perspective based on the theoretical studies of Marcus-Buttiker and on experimental analyzes focused on the electrochemical capacitance.

No description available.

As ligações de hidrogênio (LH), fundamentais na determinação da estrutura da água, proteínas, etc., são muito importantes no reconhecimento molecular e nos mecanismos de reações enzimáticas. A determinação da energia das LHs intramoleculares em proteínas e intermoleculares entre uma proteína e o solvente água, porque fornece informações sobre a estrutura secundária, terciária e quaternária das proteínas. Um método para quantificar e qualificar as LHs foi desenvolvido utilizando critérios de distância, geométricos e energéticos a partir das trajetórias obtidas por simulações de dinâmica molecular. O método foi testado com o monômero de uma fosfolipase A2 homodimérica, sem atividade catalítica, isolada do veneno da Bothrops asper(BaspMT-II). No dímero, a análise das LHs mostrou que elas são também essenciais na manutenção da estrutura quaternária. Essa análise permitiu identificar movimentos do tipo dobradiça acompanhados da formação transitória, na interface dimérica, de LHs controladas pelo triptofano na posição 77. Esses movimentos podem estar associados à ação danosa às membranas, uma vez que podem promover a inserção da região C-terminal na membrana. Estudos prévios mostraram que o peptídeo sintético (3Y codificado pelos aminoácidos 115-129 da BaspMT-II) apresenta atividade bactericida e citolítica. Um outro peptídeo (3W), mutante de 3Y, no qual três resíduos tirosina são substituidos por triptofano, apresenta um aumento do dano às membranas e do efeito miotóxico. Os mecanismos de ação desses peptídeos e as suas estruturas foram estudados por dinâmica molecular, dicroísmo circular (DC), microscopia de fluorescência e monocamadas de Langmuir (Mlang). As adsorções dos peptídeos em monocamadas de ácido dimiristoil fosfatídico (DMPA) e dimiristoilfosfatidilcolina (DMPC) se processam por mecanismos diferentes ocasionados pelas diferentes naturezas físico-químicas dos resíduos tirosina e triptofano. A microscopia de fluorescência acoplada a Mlang de DMPA com 3W adsorvido mostra um aumento da fluidez da monocamada, enquanto que o 3Y modifica os domínios do DMPA para pequenas estruturas circulares. Foram realizadas simulações dos peptídeos 3Y e 3W em meio aquoso e nas regiões interfaciais água/n-hexano e água/bicamadas de DMPC. Os resultados confirmam os obtidos por Mlang, demonstrando que os peptídeos interagem diferentemente com as membranas por adotar conformações alternativas definidas previamente. Essas conformações, diferentes das observadas em meio aquoso, dependem da natureza da interface. As estruturas encontradas no final das simulaçoes corroboram o mecanismo proposto por Mlang, assim como as estruturas sugeridas por DC. Isso sugere que a atividade biológica reduzida do peptídeo 3Y ocorre porque os seus dois resíduos Leu se adsorvem na interface sem penetrá-la. Ao contrário de 3W, os resíduos carregados do peptídeo 3Y não estão localizados corretamente para promover uma interação suficientemente atrativa para permitir a sua inserção na membrana celular. / Hydrogen bonds (HB) are highly important in the determination of the structure of the water and proteins. They also play a important role in molecular recognition and in enzyme reaction mechanisms. The determination of protein/water intermolecular and protein intramolecular HB energies provide information with respect to the formation and stabilization of secondary, tertiary and quaternary protein structure. A method that quantifies and qualifies the properties of HB was developed using distance, geometric and energy criteria as applied to data obtained from the atomic trajectories generated by molecular dynamics simulations. The method was tested with a monomer of a catalytically inactive homodimeric phospholipase A2 from Bothrops asper(BaspMT-II) venom. HBs at dimmer interface are essential for maintaining the quaternary structure, and are highly conserved during hinge-like movements of the dimmer. HB formed by tryptophan residue at position 77 controls this movement. These motions can be associated to the membrane damaging action since they facilitate the insertion of the C-terminus into the cellular membrane. Previous studies have shown that synthetic peptide (3Y, coding the amino acids 115-129 of BaspMT-II ) presents bactericidal and cytolitic activities. A peptide variant ( 3W ), in which tyrosine residues were substituted by tryptophan residues, presents an enhanced membrane damaging activity increased miotoxic effect. The mechanism of action of the peptides and their structures were studied by molecular dynamics simulations, circular dichroism (CD), fluorescence microscopy and Langmuir monolayers (Mlang). The adsorption of the peptides on a monolayer composed of dimiristoyl phosphatidic acid (DMPA) and dimiristoylphosphatidyl choline (DMPC) occurs through different processes due to the differences in the physic-chemical nature of the tyrosine and tryptophan residues. Fluorescence microscopy together with Mlang of DMPA with adsorbed 3W indicates an increase of the membrane fluidity while small circular domains are formed with DMPA. Simulations were conducted with the 3Y and 3W peptides in aqueous media, is a water/n-hexane and water/DMPC bilayers. The results confirm the Mlang results, showing that the peptides interact differently with the membranes by adopting alternative previously defined conformations. These two conformations, both of which are different to those observed in water, are dependent of the nature of the interfaces. The final simulated configurations confirm the mechanism proposed by Mlang and the structures proposed by CD. It is suggest that the reduced biological activity of the 3Y peptide is due to the two Leu residues that only adsorb to the cellular membrane without penetrating the bilayer. In contrast to the 3W peptide, no charged residue is correctly located to promote the interaction and insertion of the 3Y peptide into the membrane.

Exploiting coordination bonding of aromatic carboxylic acids at metal surfaces, this thesis explores new directions in the design and application of self-assembled monolayers (SAMs). The SAMs are investigated using a multi-technique approach comprising of a complementary combination of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In addition, the X-ray standing wave technique (XSW) was used to characterise the substrates. The process of layer formation and the final structures of the SAMs are found to be strikingly dependent on the combination of molecule and substrate, which is discussed in terms of the intermolecular and molecule-substrate interactions, bonding geometries and symmetry of the organic molecules. This is illustrated by the dramatic difference between molecular adsorption on Ag and Cu for molecules such as biphenyl-3,4',5-tricarboxylic acid and biphenyl-4-acetic acid. In the case of self-assembly on Cu, the molecule-substrate interactions play a decisive role in the resulting SAM structure, whereas on Ag, the intermolecular interactions dominate over the weaker molecule-substrate binding. This exploration of the balance of interactions that lead to the formation of these SAM structures lays the foundation for a systematic design of the structures and properties of aromatic carboxylic acid based monolayers. Finally, different applications and properties of some SAMs were investigated, namely coordination of a Pd(II) complex to a pyridine/pyrazole terminated molecule adsorbed on Ag. Evidence of coordination of Pd(II) to single molecules was provided by STM, XPS and NEXAFS spectroscopy. Additionally, controlled STM tip induced modification of local areas of a 1,3,5-tris(4-carboxyphenyl)benzene SAM on Ag was performed, opening an exciting prospect for nanoscale molecular manipulation.