Moleküler algılama; farklı türden molekülün bulunduğu bir ortamda, sadece belli bir molekülün, çoğunlukla zayıf fiziksel etkileşmeler aracılığıyla algılayıcı sisteme dönüşümlü olarak bağlanması ve salıverilmesi olarak tanımlanır. Biyolojik sistemlerde gözlemlenen moleküller arası özgün etkileşmelerin taklit edilerek endüstriyel amaçlı çalışmalara uygulanması son 20 yılın hızlı gelişen, disiplinler arası çalışma sahası haline gelmiştir. Yapay polimerler ya da polimerik jeller çok farklı özelliklere sahip monomerlerle sentezlenebilmektedir ve bunların özel bir teknikle (kalıplama tekniği) sentezlenmesi durumunda, biyolojik sistemlerde olduğu gibi, doğal seçici sistemlere benzer davranış gösteren yapay sistemlerin geliştirilebileceği düşünülebilir. Bu çalışmada hedef molekül olarak belirlenen floresans özelliğe sahip piranin molekülüne duyarlı jel sentezlenmesi ve bu jelin moleküler algılama kabiliyetinin jelin kompozisyonuna ve sıcaklık, pH, iyon derişimi gibi çevresel faktörlere bağlılığının araştırılması hedeflenmiştir. Karakterizasyon yöntemi olarak floresans spektroskopisi tekniği kullanılmıştır. Bu yöntemin en önemli üstünlükleri etkileşmeler hakkında oldukça zengin bilgi vermesi, uygulama kolaylığı ve maliyetinin düşük olmasıdır. Bu yöntem ile elde edilen spektrumlar değerlendirilerek jellerin Hafıza kabiliyetleri belirlenmiştir. Bu işlem bu tez kapsamında önerdiğimiz “Hafıza Parametresi” modeli ile gerçekleştirilmiştir. Hedef molekülün jele difüzyonu sonrası, jellerden alınan spektrumlarda meydana gelen dalgaboyu kaymaları yoluyla jellerin algılama kabiliyetleri tanımlanmıştır. Bu yolla tanımlanan ve ölçülen hafıza parametresinin kalıplanmamış jellerde sıfıra yakın çıkarken kalıplanmış jellerde en az 0.6 olarak bulunmuştur. Tezde sıcaklık, hedef molekül ve tuz derişimi, pH gibi parametrelerin algılama sürecine olan etkileri de ayrıntılı olarak tartışılmaktadır. Anahtar Kelimeler: Moleküler algılama, moleküler kalıplama, floresans spektroskopisi, polimerik jeller.The molecular recognition is defined as reversible adsorption -by means of weak physical interactions- of a specific molecule from a medium in which different kinds of molecules are exist together. Imitating the specific interactions available in the biological systems, and applying them to industrial applications have been one of rapidly developing interdisciplinary fields of last 20 years. Synthetic polymers or polymeric gels can be synthesized with monomers which have different functional peripheral groups. The physical interactions, like electrostatic, van der Waals, hydrogen bonding, and hydrophilic or hydrophobic, having different nature are possible between the polymer chains themselves, and also between the polymer chains and the solvent molecules. One of the most important properties of polymeric gels is undergoing phase transitions between collapsed and swollen states as a result of external stimuli. Namely, they are the smart materials which respond to external stimuli. This phase transition can be induced by temperature, solvent composition, pH, ionization degree of network, electric field or light. By synthesizing the polymeric gels with a special technique called as imprinting technique, it is possible to construct artificial systems showing similar behaviors with natural selective systems as in the biological systems. In these systems there are three different interactions between the target molecule and the host molecule. These are the covalent, non-covalent and semi-covalent (hybrid) interactions. The targets can be ions and molecules such as metals, small organic molecules like aminoacids, peptide, sugar and large organic molecules like polypeptide, proteins. In this work it is aimed to synthesis imprinted gels which can recognize the target molecule, pyranine, which is a fluoroprobe, and to study the strength of the recognition as a function of the composition of the gels and the environmental factors such as the concentration of the target molecule, temperature, pH and the concentration of the replacement molecules (NaCl). In these studies fluorescence technique was used as the experimental technique for characterization. Also absorption measurements were done to verify some of the fluorescence measurements. No stable dependence of the recognition on the concentration of the target molecules was observed. This is due to both the absence of replacement molecules and the loose network structure of the gel because of the small amount of crosslinker molecules. Since the network structure is very loose, the gel can not keep its initial conformation when it is collapsed. This means that the volume of the collapsed gel is smaller than the initial volume and also the size of the cavities in the gel is smaller. So this change in the sizes of the cavities destroys the imprinting effect. It was observed that at 60oC, although the gels were in collapsed state, the diffused amount of target molecules was the highest. And also the diffusion into the imprinted gel was much bigger than that of the random gel. At this temperature the imprinted gel has the most convenient conformation for the target molecules. But the random gel is not. Its volume is smaller than that of its initial volume. This smaller volume obstructs the diffusion into the random gel. It was observed that the diffusion into the gels at pH=4 is bigger than the other pH values. Since the pH of the conditions of synthesize of the gels were also around 4, it can be concluded that the microstructures of the gels became the most appropriate conformation at this pH value. Presence of the replacement molecules affects the diffusion of target molecules. At moderate concentrations of replacement molecules they bring the target molecules close to each other via the bridges constructed by the electrostatic interactions between Na+ and . In this case the fluorescence maximum of the target molecules is observed at both 430nm and 506nm. At high concentrations they separate the clusters and the fluorescence spectrum shift to 515 nm completely. The absorption experiments showed that the number of functionality groups of the target molecules was 3.1±0.9 for imprinted gel and 0.9±0.1 for the random gel. These values are very close the values given in literature. The ?Recognition Parameter? was defined first time in terms of the shifts in the wavelength of the fluorescence spectra of the gel in which the target molecules were diffused. It was calculated that it was almost zero for non-imprinted gels while it becomes bigger than 0.6 for imprinted gels. Keywords: Molecular recognition, molecular imprinting, fluorescence spectroscopy, polymeric gels.
