Specific Recognition Of A Genetically Engineered Gold Binding Peptide On Gold Substrate: Interfacial Charge Mechanisms

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2010Bu tez çalışmasında, altına özgül olarak bağlanan bir peptitin altın yüzeyini moleküler tanıması esnasında arayüzey yüklerinin etkisi araştırılmıştır. Buradaki esas amaç, anorganiklere özgül bağlanan peptitler (GEPI) ve hedef anorganik malzeme arasındaki özgül ilişki hakkında temel bir kavrayışa vakıf olmaktır. Kullandığımız model peptit 3rGBP1 ardarda üç kere tekrarlanan MHGKTQATSGTIQS amino asit dizisine sahiptir. Biz bu çalışmada peptit, çözelti ve metal yüzey arasında oluşan arayüzey dengesini metal yüzeyine voltaj uygulayarak ve çözeltinin pH ve ion konsantrasyonu değiştirerek özellikle bozduk. Daha sonra da, farklı yüklere sahip arayüzeylerde ortaya çıkan değişimleri kantitatif olarak gözlemledik. Tüm deneyler sıvı ortamında impedans görüntüleyecili elektrokimyasal kuvars kristal mikroterazi (EQCM-Z) sisteminde gerçekleştirilmiştir. Sonuçlar göstermektedir ki; 3rGBP1 moleküllerinin kendiliğinden dizilme özellikleri ara yüzey yüklerinden önemli ölçüde etkilenmektedir. Özellikle arayüzeydeki pozitif yüklü parçacıkların 3rGBP1’nin bağlanma hızını ve miktarını arttırdığı gözlemlenmiştir. Bu çalışmada GEPI’lerin adaptasyon esnekliği 3rGBP1 model peptiti kullanılarak gösterilmiştir. Bu özellik, GEPI’lerin biyonanoteknoloji uygulamalarındaki kullanım alanını genişletecektir.In this dissertation, we investigated the influence of interfacial charge on the molecular recognition of a gold binding peptide on the gold surface in order to gain fundamental understanding about the specific relationship between a genetically engineered inorganic binding peptide (GEPI) and its associated solid in aqueous environments. Our model peptide was 3rGBP1 possessing an amino acid sequence MHGKTQATSGTIQS in triply tandem repeat form. In this study, we, intentionally, disturbed the equilibrium interface between peptide, buffer solution and the solid surface by applying external voltage to the solid surface and variation of solution charge through its pH and ionic strength. Subsequently, we observed the differences at several charged environments quantitatively. All experiments were performed in solution using an electrochemical quartz crystal microbalance with impedance monitoring (EQCM-Z). Results revealed that self-assembly properties of 3rGBP1 were significantly influenced by interfacial charge alterations. Particularly the presence of positively charged species at the interface accelerated the adsorption rates in substantial amounts. The adaptation flexibility of GEPI, shown in this study using a model protein 3rGBP1, will certainly expand their utility in bionanotechnological applications.DoktoraPh

Polyelectrolyte multilayer microcapsules templated on spherical, elliptical and square calcium carbonate particles

Recent studies have revealed that a variety of shaped particles can interact with cells in a different way. Elongated particles can be effectively and quickly internalized intercellularly compared with other configurations. Herein we present the potential of fabrication of anisotropic polyelectrolyte multilayer capsules formed by coating spherical, ellipsoid-like and square calcium carbonate (CaCO3) particles. By varying the intermixing speed, time, pH value and ratio of initial ingredients during precipitation such CaCO3 templates are produced. Particles loaded with FITC-dextran and coated with polyelectrolytes could maintain the templated shape after core removal. Quantitative data are derived from analysis of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) measurements

Loading capacity versus enzyme activity in anisotropic and spherical calcium carbonate microparticles

A new method of fabrication of calcium carbonate microparticles of ellipsoidal, rhomboidal, and spherical geometries is reported by adjusting the relative concentration ratios of the initial salt solutions and/or the ethylene glycol content in the reaction medium. Morphology, porosity, crystallinity, and loading capacity of synthesized CaCO3 templates were characterized in detail. Particles harboring dextran or the enzyme guanylate kinase were obtained through encapsulation of these macromolecules using the layer-by-layer assembly technique to deposit positively and negatively charged polymers on these differently shaped CaCO3 templates and were characterized by confocal laser scanning fluorescence microscopy, fluorometric techniques, and enzyme activity measurements. The enzymatic activity, an important application of such porous particles and containers, has been analyzed in comparison with the loading capacity and geometry. Our results reveal that the particles’ shape influences morphology of particles and that, as a result, affects the activity of the encapsulated enzymes, in addition to the earlier reported influence on cellular uptake. These particles are promising candidates for efficient drug delivery due to their relatively high loading capacity, biocompatibility, and easy fabrication and handling