Bitki ekstrelerinden elde edilen çiçek şekilli nano biyokatalizörlerin peroksidaz benzeri aktivitelerinin polimerleşme reaksiyonları üzerine etkisinin incelenmesi
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Date
2021
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Hatay Mustafa Kemal Üniversitesi
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info:eu-repo/semantics/openAccess
Abstract
Enzim katalizörü eşliğinde gerçekleştirilen polimerleşme reaksiyonları çevreye dost ve uygulaması kolay bir yöntem olarak yoğun araştırma yapılan konulardan biri olmuştur. Enzimlerin çoğu metal iyonlarından oluşan katalitik uçlara sahiptir (örneğin peroksidazlar ve süperoksit dismutazlar). Horseradish peroksidaz (yaban turpu peroksidaz, HRP) gibi hemoproteinler, vinil grubu içeren monomerlerin ve aromatik bileşiklerin (fenol, anilin vb.) radikalik polimerleşme reaksiyonlarında oldukça fazla kullanılan enzimlerdir. Bu katalizörler hidrojen peroksit'ten substrat'a elektron transfer ederek polimerleşmeyi başlatacak radikali oluşturmayı başarmaktadırlar. Bu sayede birçok polimerik malzeme enzim katalizörleriyle başarılı bir şekilde sentezlenmektedir. Ancak enzimlerin pahalı oluşu, sulu çözeltilerde kararsız oluşları, yüksek sıcaklık ve organik çözücüler içerisinde denatürasyona uğramaları ve tekrar kullanılabilmelerinin verimli olmaması enzimlerin endüstriyel ölçekteki kullanımını oldukça kısıtlamaktadır. Bu sebepten dolayı enzimlerin gösterdiği katalitik aktiviteyi gösterebilecek yeni nesil katalizörler bulmak ticari ve bilimsel açıdan oldukça önem arz etmektedir. Son zamanlarda bitki ekstrelerinden elde edilen çiçek şekilli hibrit nano biyokatalizörler bu açığı kapatma adına önemli bir alternatif olmuş ve bu konuda yoğun çalışmalar yapılmaya devam edilmektedir. İnorganik bileşen olarak metal iyonları (örneğin Cu2+) ve organik bileşen olarak da değişik bitki ekstrelerinin kullanılmasıyla hibrit organik-inorganik çiçek yapılı nano biyokatalizörler sentezlenebilmekte ve elde edilen bu çiçek şekilli nano biyokatalizörler oksidasyon reaksiyonlarında enzim benzeri aktivite gösterebilmektedirler. Bu tarz hibrit nano biyokatalizörlerin temel oksidasyon davranışları incelenmiş olmasına rağmen, literatürde henüz polimerleşme reaksiyonlarında kullanımları incelenmemiştir. Tez çalışmasında iki farklı bitki ekstresinin (yeşil çay ve kartopu çiçeği ekstreleri) Cu2+ iyonları ile koordine edildikten sonra elde edilen çiçek şekilli nano biyokatalizörlerin peroksidaz benzeri aktivitelerinin, fenol türevi monomerlerin (fenol, guaiacol ve salisilik asit) polimerleştirilmesi üzerine etkileri incelenmiştir. Elde edilen bulgulara göre sentezlenen katalizörler fenol ve guaiacol'ün polimerleşmesi üzerine oldukça yüksek katalitik aktivite göstermiştir. Bu iki monomerle gerçekleştirilen polimerleşmelerde polimerleşme verimleri ve elde edilen polimerlerin molekül ağırlıkları oldukça yüksek bulunmuştur. Salisilik asit'in sulu ortamda çözünme probleminden dolayı bu monomerin polimerleşme reaksiyonları her iki katalizör ortamında da oldukça düşük verimlerde gerçekleşmiştir. Bununla birlikte HRP enziminin aktivitesini kaybettiği 60 oC ve üzerindeki sıcaklıklarda dahi sentezlenen katalizörler oldukça yüksek katalitik aktivite sergilemiştir. Bu özellik HRP enziminin aksine bu tarz katalizörlerin yüksek sıcaklık gerektiren reaksiyonlarda da kullanılabilir olduğunu göstererek hem bilimsel ve hemde endüstriyel açıdan önemli avantajlar sağlamaktadır.
Enzyme catalyzed polymerization reactions have been extensively studied by many polymer research groups and are known to be environmental friendly and easy method for many applications. Many enzymes have active sites containing metal ions, for example peroxidases and superoxide dismutases. Hemoproteins like Horseradish peroxidase (HRP) have been studied to explore radicalic polymerization reactions of some aromatic compounds (phenol, aniline, etc.) and vinyl monomers. These catalysts transfer an electron from hydrogen peroxide to the substrate to generate radicals for the initiation of polymerization. Due to that, many polymeric materials can be successfully synthesized by enzyme catalysts. However; high cost of enzymes, instability in aqueous solutions, denaturations in organic solvents and high temperatures, and inefficiency to be used over and over again of enzymes strictly limit their use in industrial applications. Especially, it is crucial requirement to use enzymes over and over again for commercial purposes. For this reason, it is important to discover new generation catalyst systems indicating similar catalytic activities like enzymes for commercial and scientific applications. Recently, flower shaped hybrid organic-inorganic nano biocatalysts obtained from plant extracts become alternative catalyst systems to overcome these disadvantages. Hybrid organic-inorganic flower shaped nano-biocatalysts are synthesized from metal ions (for example, copper (II) ions, Cu2+) as the inorganic component and plant extracts as the organic component. Obtained these flower shaped nano biocatalysts show enzyme like activities. Although the basic oxidation reactions of these types of hybrid nano biocatalysts have been studied by many research groups, their use in polymerization reactions has not yet been investigated in the literature. In the thesis study, the effects of peroxidase-like activities of flower-shaped nano-biocatalysts obtained from two different plant extracts (green tea and viburnum-opulus extract) and Cu2+ ions were investigated on the polymerization of phenol-derivatives (phenol, guaiacol and salicylic acid). Obtained successful outcomes showed that the synthesized catalysts showed very high catalytic activity upon polymerization of phenol and guaiacol. The polymerization yields and molecular weights of the obtained polymers in the polymerizations carried out with these two monomers were found to be quite high. Due to the solubility problem of salicylic acid in aqueous conditions, polymerization reactions of salycilic acid resulted in very low yields for polymerizations carried out for both catalyst systems. Free HRP enzyme loses its catalytical activities at 60 oC and above temperatures. However, the synthesized catalysts exhibited quite high catalytic acivities even at 60 oC and above reaction temperatures. This outcome provides significant advantages in some reactions requiring high temperatures and is very important to use them for both scientific studies and industrial applications.
Enzyme catalyzed polymerization reactions have been extensively studied by many polymer research groups and are known to be environmental friendly and easy method for many applications. Many enzymes have active sites containing metal ions, for example peroxidases and superoxide dismutases. Hemoproteins like Horseradish peroxidase (HRP) have been studied to explore radicalic polymerization reactions of some aromatic compounds (phenol, aniline, etc.) and vinyl monomers. These catalysts transfer an electron from hydrogen peroxide to the substrate to generate radicals for the initiation of polymerization. Due to that, many polymeric materials can be successfully synthesized by enzyme catalysts. However; high cost of enzymes, instability in aqueous solutions, denaturations in organic solvents and high temperatures, and inefficiency to be used over and over again of enzymes strictly limit their use in industrial applications. Especially, it is crucial requirement to use enzymes over and over again for commercial purposes. For this reason, it is important to discover new generation catalyst systems indicating similar catalytic activities like enzymes for commercial and scientific applications. Recently, flower shaped hybrid organic-inorganic nano biocatalysts obtained from plant extracts become alternative catalyst systems to overcome these disadvantages. Hybrid organic-inorganic flower shaped nano-biocatalysts are synthesized from metal ions (for example, copper (II) ions, Cu2+) as the inorganic component and plant extracts as the organic component. Obtained these flower shaped nano biocatalysts show enzyme like activities. Although the basic oxidation reactions of these types of hybrid nano biocatalysts have been studied by many research groups, their use in polymerization reactions has not yet been investigated in the literature. In the thesis study, the effects of peroxidase-like activities of flower-shaped nano-biocatalysts obtained from two different plant extracts (green tea and viburnum-opulus extract) and Cu2+ ions were investigated on the polymerization of phenol-derivatives (phenol, guaiacol and salicylic acid). Obtained successful outcomes showed that the synthesized catalysts showed very high catalytic activity upon polymerization of phenol and guaiacol. The polymerization yields and molecular weights of the obtained polymers in the polymerizations carried out with these two monomers were found to be quite high. Due to the solubility problem of salicylic acid in aqueous conditions, polymerization reactions of salycilic acid resulted in very low yields for polymerizations carried out for both catalyst systems. Free HRP enzyme loses its catalytical activities at 60 oC and above temperatures. However, the synthesized catalysts exhibited quite high catalytic acivities even at 60 oC and above reaction temperatures. This outcome provides significant advantages in some reactions requiring high temperatures and is very important to use them for both scientific studies and industrial applications.
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Kimya, Chemistry
