In this work, the synthesis of biopolymer-based hydrogel networks with defined architecture is presented. In order to obtain materials with defined properties, the chemoselective copper-catalyzed azide-alkyne cycloaddition (or Click Chemistry) was used for the synthesis of gelatin-based hydrogels. Alkyne-functionalized gelatin was reacted with four different diazide crosslinkers above its sol-gel transition to suppress the formation of triple helices. By variation of the crosslinking density and the crosslinker flexibility, the swelling (Q: 150-470 vol.-%;) and the Young’s and shear moduli (E: 50 kPa - 635 kPa, G’: 0.1 kPa - 16 kPa) could be tuned in the kPa range. In order to understand the network structure, a method based on the labelling of free functional groups within the hydrogel was developed. Gelatin-based hydrogels were incubated with alkyne-functionalized fluorescein to detect the free azide groups, resulting from the formation of dangling chains. Gelatin hydrogels were also incubated with azido-functionalized fluorescein to check the presence of alkyne groups available for the attachment of bioactive molecules. By using confocal laser scanning microscopy and fluorescence spectroscopy, the amount of crosslinking, grafting and free alkyne groups could be determined. Dangling chains were observed in samples prepared by using an excess of crosslinker and also when using equimolar amounts of alkyne:azide. In the latter case the amount of dangling chains was affected by the crosslinker structure. Specifically, 0.1% of dangling chains were found using 4,4’-diazido-2,2’-stilbene-disulfonic acid as cosslinker, 0.06% with 1,8-diazidooctane, 0.05% with 1,12-diazidododecane and 0.022 % with PEG-diazide. This observation could be explained considering the structure of the crosslinkers. During network formation, the movements of the gelatin chains are restricted due to the formation of covalent netpoints. A further crosslinking will be possible only in the case of crosslinker that are flexible and long enough to reach another chain. The method used to obtain defined gelatin-based hydrogels enabled also the synthesis of hyaluronic acid-based hydrogels with tailorable properties. Alkyne-functionalized hyaluronic acid was crosslinked with three different linkers having two terminal azide functionalities. By variation of the crosslinking density and crosslinker type, hydrogels with elastic moduli in the range of 0.5-3 kPa have been prepared. The variation of the crosslinking density and crosslinker type had furthermore an influence also on the hydrolytic and enzymatic degradation of gelatin-based hydrogels. Hydrogels with a low crosslinker amount experienced a faster decrease in mass loss and elastic modulus compared to hydrogels with higher crosslinker content. Moreover, the structure of the crosslinker had a strong influence on the enzymatic degradation. Hydrogels containing a crosslinker with a rigid structure were much more resistant to enzymatic degradation than hydrogels containing a flexible crosslinker. During hydrolytic degradation, the hydrogel became softer while maintaining the same outer dimensions. These observations are in agreement with a bulk degradation mechanism, while the decrease in size of the hydrogels during enzymatic degradation suggested a surface erosion mechanism. Because of the use of small amount of crosslinker (0.002 mol.% 0.02 mol.%) the networks synthesized can still be defined as biopolymer-based hydrogels. However, they contain a small percentage of synthetic residues. Alternatively, a possible method to obtain biopolymer-based telechelics, which could be used as crosslinkers, was investigated. Gelatin-based fragments with defined molecular weight were obtained by controlled degradation of gelatin with hydroxylamine, due to its specific action on asparaginyl-glycine bonds. The reaction of gelatin with hydroxylamine resulted in fragments with molecular weights of 15, 25, 37, and 50 kDa (determined by SDS-PAGE) independently of the reaction time and conditions. Each of these fragments could be potentially used for the synthesis of hydrogels in which all components are biopolymer-based materials. / In dieser Arbeit wird die Synthese Biopolymer-basierter Hydrogelnetzwerke mit definierter Architektur beschrieben. Um Materialien mit definierten und einstellbaren Eigenschaften zu erhalten, wurde die chemoselektive Kupferkatalysierte Azid-Alkin-Cycloadditionsreaktion (auch als Click-Chemie bezeichnet) für die Synthese Gelatine-basierter Netzwerke eingesetzt. Alkin-funktionalisierte Gelatine wurde mit vier verschiedenen Diazid-Quervernetzern oberhalb der Gel-Sol-Übergangstemperatur umgesetzt, um die Formierung tripelhelikaler Bereiche durch Gelatineketten zu unterdrücken. Durch Variation der Menge an Quervernetzer (und damit der Netzdichte) sowie der Länge und Flexibilität der Quervernetzer konnten u.a. die Quellung (Q: 150-470 vol.-%) sowie der Young’s - und Schermodul im kPa Bereich eingestellt werden (E: 50 kPa - 635 kPa, G’: 0.1 kPa - 16 kPa). Um die Netzwerkarchitektur zu verstehen, wurde eine Methode basierend auf dem Labeln unreagierter Azid- und Alkingruppen im Hydrogel entwickelt. Die Gelatine-basierten Hydrogele wurden mit Alkin-funktionalisiertem Fluorescein umgesetzt, um freie Azidgruppen zu detektieren, die bei einem Grafting entstehen. Darüber hinaus wurden die Hydrogele mit Azid-funktionalisiertem Fluorescein reagiert, um die Menge an freien Alkingruppen zu bestimmen, die zudem potentiell für die Anbindung bioaktiver Moleküle geeignet sind. Quervernetzung, Grafting, und die Anzahl freier Alkingruppen konnten dann mit Hilfe der konfokalen Laser Scanning Mikroskopie und der Fluoreszenzmikroskopie qualitativ und quantitativ nachgewiesen werden. Gegraftete Ketten wurden in Systemen nachgewiesen, die mit einem Überschuss an Quervernetzer hergestellt wurden, entstanden aber auch beim Einsatz äquimolarer Mengen Alkin- und Azidgruppen. Im letzteren Fall wurde in Abhängigkeit von der Struktur des Diazids unterschiedliche Anteile gegrafteter Ketten festgestellt. 0.1 mol-% von gegrafteten Ketten wurden für 4,4’-Diazido-2,2’-stilbendisulfonsäure gefunden, 0.06 mol-% für 1,8-Diazidooktan, 0.05 mol% für 1,12-diazidododecan und 0.022 mol-% für PEG-Diazid. Diese Beobachtung kann durch die unterschiedliche Flexibilität der Vernetzer erklärt werden. Während der Netzwerkbildung werden die Bewegungen der Gelatineketten eingeschränkt, so dass kovalente Netzpunkte nur erhalten werden können, wenn der Vernetzer lang und flexibel genug ist, um eine andere Alkingruppe zu erreichen. Die Strategie zur Synthese von Biopolymer-basierten Hydrogelen mit einstellbaren Eigenschaften wurde von Gelatine- auf Hyaluronsäure-basierte Gele übertragen. Alkin-funktionalisierte Hyaluronäure wurde mit drei verschiedenen Diaziden quervernetzt, wobei Menge, Länge, und Flexibilität des Quervernetzers variiert wurden. In dieser Weise wurden sehr weiche Hydrogele mit E-Moduli im Bereich von 0.5-3 kPa hergestellt. Die Variation der Vernetzungsdichte und des Vernetzertyps beeinflusste weiterhin den hydrolytischen und enzymatischen Abbau der Hydrogele. Hydrogele mit einem geringerem Anteil an Quervernetzer wurden schneller abgebaut als solche mit einem höheren Quervernetzeranteil. Darüber hinaus konnte gezeigt werden, dass Hydrogele mit Quervernetzern mit einer rigiden Struktur deutlich langsamer degradierten als Hydrogele mit flexibleren Quervernetzern. Während des hydrolytischen Abbau wurden die Materialien weicher, behielten aber ihre Form bei, was mit einem Bulk-Abbau-Modell übereinstimmt. Während des enzymatischen Abbaus hingegen änderten sich die Materialeigenschaften kaum, jedoch wurden die Proben kleiner. Diese Beobachtung stimmt mit einem Oberflächenabbaumechanismus überein. Da in allen vorgestellten Systemen nur eine kleine Menge synthetischer Vernetzer eingesetzt wurde (0.002 – 0.02 mol%), können die Materialien noch als Biopolymer-basierte Materialien klassifiziert werden. Jedoch enthalten die Materialien synthetische Abschnitte. In Zukunft könnte es interessant sein, einen Zugang zu Materialien zu haben, die ausschließlich aus Biopolymeren aufgebaut sind. Daher wurde der Zugang zu Biopolymer basierten Telechelen untersucht, die potentiell als Vernetzer dienen können. Dazu wurden durch die kontrollierte Spaltung von Gelatine mit Hydroxylamin Gelatinefragmente mit definiertem Molekulargewicht hergestellt. Hydroxalamin reagiert unter Spaltung mit der Amidbindung zwischen Asparagin und Glycin, wobei Aspartylhydroxamate und Aminoendgruppen entstehen. Die Reaktion von Gelatine mit Hydroxylamin ergab Fragmente mit Molekulargewichten von 15, 25, 37, und 50 kDa (bestimmt mit SDS-PAGE), und die Formierung dieser Fragmente war unabhängig von den weiteren Reaktionsbedingungen und der Reaktionszeit. Jedes dieser Fragmente kann potentiell für die Synthese von Hydrogelen eingesetzt werden, die ausschließlich aus Biopolymeren bestehen.

Attention to Advertising Carl Patrik Nilsson, Umeå School of Business, Umeå University SE-901 87 Umeå, Sweden Abstract In advertising, capturing consumers’ attention is imperative. Yet, how attention to advertising works in a World Wide Web context has not been researched extensively. This area is the main focus of this research. The World Wide Web is an interactive medium which has characteristics that deviate from traditional media channels. Considering the unique properties of the World Wide Web it was deemed important to study how attention to advertising is affected by various contexts as well as attention getting techniques. The study was conducted in order to develop an understanding of how advertisements in different Web task environments are being attended to as well as how attention to advertisements varies between different attention getting techniques that are being used in Web advertising. Furthermore, a model which describes the relationship between context, attention getting techniques and attention to advertising was developed and tested. In connection to this it was tested whether click-through or click-rate is indeed an adequate method when measuring advertising effect and thereby to what extent the pay per click pricing strategy is appropriate. In order to address the research issues a theoretical framework was assembled. Nine hypotheses were formulated deriving from the framework. To test the hypotheses and the model, an experimental research design was employed. Three experiments were designed to study the hypotheses formulated. A total of 702 individual experiments were conducted. The conclusions from the study reveal that Web task environments indeed have an impact on attention to advertising. Increased complexity or a more difficult task environment demands more cognitive resources which in turn produces lower attention levels to the advertising stimulus. Reduced complexity, on the other hand, releases cognitive resources that can be spent elsewhere. Thus, a higher attention level to the advertising stimulus was recorded. This also confirmed the properties of the proposed model; namely that the permeability of a filtering mechanism is dependent on for instance level of goal orientation and complexity of the physical task environment i.e. the complexity of the Web site. The study revealed that attention getting techniques such as pop-up advertisements increase the attention to advertising. However, it was found that pop-up advertisements are effective, not mainly because of their abrupt presentation, but because of the distinct properties of the frame. It was found that the frame has a negative meaning for Web users and when the frame comes into the visual field it will attract their attention. At the same time attention will also be distributed towards the advertisement itself. This is recorded as an increase in attention towards the advertising message. The results show that the click-through measure is not an appropriate method when measuring advertising effect. The click-through measure may severely underestimate the advertising effect. Consequently, using click-through frequencies as a basis for pricing is inappropriate, unless the effects at play have been well understood and taken into consideration. Key words: Attention to advertising, attention getting techniques, Web advertising, Web environment, click-through Studies in Business Administration, B series, No 60. ISSN 0346-8291, ISBN 91-7264-189-4 Umeå School of Business - Sweden 2006

Immobilization of different bio- and organic molecules on solid supports is fundamental within many areas of science. Sometimes, it is desirable to obtain a directed orientation of the molecule in the immobilized state. In this thesis, the copper (I) catalyzed Huisgen 1,3-dipolar cycloaddition, referred to as a “click chemistry” reaction, was explored as a means to perform directed immobilization of small molecule ligands on gold surfaces. The aim was to synthesize alkyne- and azide-terminated alkanethiols that would form well-organized self assembled monolayers (SAMs) on gold from the commercially available substances orthoethylene glycol and bromo alkanoic acid. N-(23-azido-3,6,9,12,15,18,21-heptaoxatricosyl)-n-mercaptododekanamide/hexadecaneamide (n = 12, 16) were successfully synthesized and allowed to form SAMs of different compositions to study how the differences in density of the functional groups on the surface would influence the structure of the monolayer and the click chemistry reaction. The surfaces were characterized by different optical methods: ellipsometry, contact angle goniometry and infrared reflection-absorption spectroscopy (IRAS). The click reaction was found to proceed at very high yields on all investigated surfaces. Finally, the biomolecular interaction between a ligand immobilized by click chemistry on the gold surfaces and a model protein (bovine carbonic anhydrase) was demonstrated by surface plasmon resonance using a Biacore system.

Ce travail a pour objet l'obtention et la caractérisation de nouveaux copolymères amphiphiles et d'hydrogels à hydrophilie contrôlée, à partir de polymères naturels, avec comme utilisations potentielles la vectorisation de principes actifs. En conséquence, il est donc nécessaire que les polymères utilisés pour l'obtention de ces architectures répondent à un certain nombre de contraintes, notamment être non-toxiques, biocompatibles et biodégradables. Pour ces raisons, on retient le plus souvent comme matériaux de départ des polymères naturels, en particulier les polysaccharides. Quelques polymères synthétiques répondent aussi à ces contraintes, telle que la polycaprolactone. Ainsi, le matériau de base utilisé dans ce travail est l'amidon sur lequel a été greffé soit la poly (ε-caprolactone), soit une chaîne grasse. La thèse est structurée en cinq chapitres consacrés d'une part au greffage de structures hydrophobes sur l'amidon et la formation d'hydrogels à hydrophobie modulable, d'autre part à la vectorisation de la lévofloxacine par ces composés. La première partie traite du greffage de la polycaprolactone sur l'amidon par "click chemistry" (CuAAC) entre l'amidon fonctionnalisé par des fonctions alcynes et des polycaprolactones à fonction azoture en bout de chaîne, ces dernières étant préalablement obtenues par POC de la caprolactone. Les réactions de CuAAC ont été effectuées non seulement selon les protocoles habituels, mais aussi par micro ondes. Par ailleurs, l'amidon a aussi été hydrophobisé par les méthodes usuelles d'estérification par une chaîne grasse via le chlorure de l'acide palmitoique. Les produits ainsi obtenus ont été caractérisés par RMN, IR, XPS et leur comportement dans différents solvants (solubilité, gonflement) a été étudié. Une seconde partie est consacrée à l'élaboration d'hydrogels à base d'amidon et d'amidon modifié avec des chaînes d'acides gras et de PCL par réticulation avec l'acide citrique. Afin d'atteindre les objectifs, une stratégie multifactorielle expérimentale avec deux variables indépendantes a été utilisée. La modélisation mathématique des données expérimentales permet de remonter aux paramètres physico-chimiques pertinents, montre les effets de synergie et établit les conditions d'optimisation. Une dernière partie a permis d'évaluer les cinétiques de libération de la lévofloxacine, un antibiotique de dernière génération, par les hydrogels obtenus. Les matériaux obtenus ont montré des propriétés de libération contrôlée potentiellement intéressantes. Les résultats obtenus au cours de cette thèse ont été évalués par la publication de trois articles et par dissémination des résultats au six conférences internationales.

Oligonucleotides are short fragments of DNA (10-100nt) which are of great interest because their applications in molecular biology, biomedicine and nanotechnology. As a result of their ability to base pairing, oligonucleotides can be used as primers, hybridization probes in biosensors, agents for controlling gene expression, structural material in nanotechnology or as substrates for a variety of biochemical and biophysical studies. Chemical modification of oligonucleotides as well as conjugation to different functional molecules allows for modulation of both therapeutical and biotechnological properties. This thesis is focused in the nucleic acid chemistry field and the main objective is the synthesis of modified oligonucleotides for obtaining structures with therapeutical and/or biotechnological interest. Oligonucleotides capable to form structures other than the canonical DNA double helix have received considerable attention in the last years. The ability of triplex forming oligonucleotides (TFOs) to bind specifically to certain duplex DNA regions provides a strategy for site-directed modification of genomic DNA. Besides, G-quadruplexes are four-stranded DNA structures stabilized by stacking of guanine tetrads which have been found in telomeres and some promoters and play a role in regulation of transcription and translation. In addition, they are also interesting for nanotechnological devices. In this context, the first part of the research work was addressed to synthesize parallel stranded oligonucleotide clamps carrying LNA (locked nucleic acid) residues and study the stability of the triplex formed with DNA and RNA target sequences. Secondly, a novel strategy to obtain parallel clamps using the non-templated chemical ligation of two oligonucleotides by 5’-5’ linkages was developed. For this purpose, several protocols for introduce azido and alkyne moieties in the 5’-end of different sequences were developed so that the modified DNA strands could form a parallel hairpin after their chemical ligation by click chemistry. Thirdly, a system composed of four DNA strands whose 5’ ends are covalently attached was designed to form a monomolecular parallel G-quadruplex, which was used to study the effects of some nucleobase modifications in quadruplex structure. Finally, oligonucleotide conjugates carrying Cu(II) complexes were synthesized to construct arrays of electrochemical oscillators for nanotechnology applications.

Les MOFs résultent de l'organisation de polyèdres métalliques reliés par des molécules organiques chélatantes pour former un réseau poreux. La construction de solides hybrides organiques/inorganiques permet d'imaginer un très grand nombre de matériaux aux propriétés structurales et physico-chimiques variées. Le confinement du substrat dans une structure rigide, associé à des propriétés particulières des clusters métalliques ainsi qu'à des parois pouvant être fonctionnalisées, fournissent un environnement catalytique unique, plaçant les MOF à la frontière entre les espèces types zéolites et les enzymes. Cependant, il existe aujourd'hui très peu de MOFs possédant plus d'une fonction catalytique. Néanmoins, les propriétés catalytiques des MOFs peuvent être améliorées de façons non négligeables grâce aux méthodes de post-fonctionalisation. Dans ce travail, nous reportons le développement d'une méthode de post-fonctionnalisation originale des amino-MOFs. La première étape consiste à convertir la fonction amine en fonction azoture. Puis, sans isolation ni purification, le MOF fonctionnalisé est obtenu par " Click Chemistry " en ajoutant l'alcyne correspondant. Cette méthode peut être appliquée à tous les types d'amino-MOFs et à quasi toutes les fonctions chimiques que l'on souhaite greffer. Une large librairie de nouveaux matériaux a ainsi été obtenue et complètement caractérisée. Cette méthode a aussi été utilisée pour créer des MOFs catalytiques à façon pour une réaction de transesterification, ainsi que pour l'investigation de nouvelles applications plus fines (niches industrielle)

No description available.

An antenna for light harvesting is an organized multicomponent system in which several chromophoric molecular species absorb the incident light and channel the excitation energy to a common acceptor component. In this study, Click chemistry has been successfully applied in the synthesis of a bay region tetraboron dipyrrin (BODIPY) appended perylenediimide (PDI). This light-harvesting molecule presents a large cross section for the absorption of light in the visible region. Excitation energy is efficiently channeled to the perylenediimide core. This novel antenna system is the first demonstration of the efficiency of energy transfer in a BODIPY- PDI bichromophoric system and appears to be highly promising for the design and synthesis of similar dendritic structures.

The application of Global Internet gives birth to a new trading method, electronic commerce (EC). Because EC possesses advantages such as rapid circulation, far-reaching, low cost, and anytime and anywhere etc., the development of EC replaces the information, contacts, and consultation processes in some traditional sales channels and even develops into direct mode of shopping. Tourism products belong to intangible experiential services with characteristics such as heterogeneity, intangibility, and perishability etc., which makes the travel industry an information intensive industry and is very suitable for the development of EC. Resource-based theory is used as a framework to study its application on the travel industry in this research. It is combined with field interviews and case analysis to study the tourism EC. The critical success factors for travel agencies to develop EC are summarized through the analysis and comprehensive comparison of two different types of travel agencies. It is found that the profitability of tourism EC is mainly dominated by cost leading strategy with the differentiation strategy as a supplement. However, the differentiation strategy can attract customers and lock them in; the most important among them is to enhance the added values. Enterprises will transform their organization structure and strategies according to their own characteristics and resources during the development of EC and the tourism industry belongs to information flow intensive industry in which the deployment of EC requires a set of suitable and complete business model to have a high possibility of success. The research results show that ¡§fully understanding customers¡¦ needs¡¨ is the necessary capability to develop EC successfully and customer and member base is the critical success factor. Also, ¡§value creation¡¨ can be achieved through the development of social networks and blog marketing; at the same time, the research also shows that travel agencies are gradually developing cross channel integration in the process of developing electronic commerce: whether it is virtual travel agency moving from virtual to brick and mortar or traditional agency moving from brick and mortar to virtual, they tend to move toward the integration of click-and-mortar. EC is not just simply establishing a web site: it also includes solving problems such as internal process transformation, computerization, networking, and communicating with external resources etc. It bounds to change certain part of work which employees perform currently and induces behavior changes in consumers. The critical point to the success of the tourism EC is how to coordinate so that employees will accept the new work model and consumers will accept new consumption method.

Modular polyketide synthases (PKSs) are the largest enzymes known to man and are responsible for synthesizing some of the most important human medicines. Their ability to construct stereochemically-rich carbon chains containing diverse substituents has inspired the biosynthetic community to engineer these factories for the in vitro synthesis of a small library of polyketide compounds. New complex polyketides are discovered every year, yet the lack of compound prohibits characterization and testing of these new compounds for medicinal properties. Smaller polyketide compounds generated in vitro could be organically manipulated to generate larger, more complex polyketide natural products and natural product analogs. Chemoenzymatic approaches like this would be extremely beneficial to the scientific community; however, there are still obstacles that must be overcome before the use of PKS for the preparative synthesis of an in vitro generated polyketide library would prove fruitful: purchasing substrates such as methylmalonyl-CoA is cost-prohibitive, PKSs are often difficult to express and purify, and the products generated are typically nonchromophoric. The use of a malonyl-CoA ligase from Streptomyces coelicolor (MatB) was investigated for the enzymatic synthesis of polyketide extender units such as methylmalonyl-CoA (Chapter 2). MatB synthesized a total of 5 CoA-linked extender units in vitro: malonyl-, methylmalonyl-, ethylmalonyl-, hydroxymalonyl- and methoxymalonyl-CoA. Two ternary complex structures of MatB with bound product and leaving group were also solved to sub-2Å resolution. MatB generated extender units were employed in the module-catalyzed synthesis of a triketide pyrone. The selectivity of a PKS module to incorporate a variety of side chains into triketide pyrones was also investigated (Chapter 3). A total of 10 triketide pyrone compounds were synthesized, 5 produced via modular "stuttering" and one possessing a terminal alkyne chemical handle. Lastly, nonchromphoric polyketide products were made visible upon copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) with fluorescent sulforhodamine B azide revealing insights into in vitro reactivites of a PKS module (Chapter 4). The work described in this dissertation has helped advance the scientific community towards procuring an in vitro synthesized polyketide library for future synthetic applications. / text