Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Subject: search.filters.subject.EPR spectroscopyWoS Q: search.filters.wosQuartile.Q2

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  • Article
    Citation - WoS: 7
    Citation - Scopus: 7
    Increasing Spontaneous Wet Adhesion of Dopa With Gelation Characterized by Epr Spectroscopy
    (Elsevier Ltd., 2019) Göksel, Yaman; Akdoğan, Yaşar
    The presence of water molecules around both adhesive materials and surface results in the hydration barriers that weaken adhesion. In nature, mussels attach to various types of surfaces by using 3,4-dihydroxyphenylalanine (DOPA) containing mussel foot proteins. DOPA shows wet adhesive properties before and after contribution in the hydrogel formation. Here, the wet adhesive properties of DOPA modified four armed poly (ethylene glycol) polymer (PEG-(DOPA)(4)) and its hydrogels induced by (IO4)(-) or (Cr2O7)(2-) ions are compared by using electron paramagnetic resonance (EPR) spectroscopy in terms of their surface coverages. In water, spin labeled hydrophobic polystyrene (SL-PS) and hydrophilic silica (SL-SiO2) nanoparticles are prepared, and the percentages of their covered surface values are obtained. Without applying force, the adhesion to SL-PS increases in the order of PEG-(DOPA)(4) < PEG-(DOPA)(4) + (IO4)(-) hydrogel < PEG-(DOPA)(4) + (Cr2O7)(2-) hydrogel with the percentages of surface coverages 65%, 76% and 93%, respectively. Although, neither of PEG-(DOPA)(4) polymer and (IO4)(-) induced PEG-(DOPA)(4) hydrogel adhere to SL-SiO2 nanoparticle spontaneously, (Cr2O7)(2-) induced PEG-(DOPA)(4) hydrogel adhere to SL-SiO2 with a 59% of surface coverage. These results show that gelation mechanisms of DOPA have effect on the spontaneous adhesion of DOPA to the wet surfaces even for the hydrophilic silica surface.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 12
    The Effect of Dopa Hydroxyl Groups on Wet Adhesion To Polystyrene Surface: an Experimental and Theoretical Study
    (Elsevier, 2020) Yıldız, Remziye; Özen, Sercan; Şahin, Hasan; Akdoğan, Yaşar
    Mussels wet adhesive performance has been arousing curiosity for a long time. It is found that 3,4-dihydroxyphenylalanine (DOPA) is responsible for adhesive properties of mussels. Despite a large body of research characterizing the interactions DOPA with hydrophilic surfaces, relatively few works have addressed the mechanism of interactions with hydrophobic surfaces. The benzene ring of DOPA is the main attributor to the adhesion on hydrophobic polystyrene (PS) surface. However, here we showed that two hydroxyl groups of catechol have also effects on wet adhesion. We studied wet adhesive properties of DOPA, tyrosine and phenylalanine functionalized PEG polymers, PEG-(N-Boc-L-DOPA)(4), PEG-(N-Boc-L-Tyrosine)(4), PEG-(N-Boc-L-Phenylalanine)(4), on spin labeled PS nanobeads (SL-PS) by electron paramagnetic resonance (EPR) spectroscopy. Surface coverage ratio of SL-PS upon additions of PEG-(N-Boc-L-DOPA)(4), PEG-(N-Boc-L-Tyrosine)(4) and PEG-(N-Boc-L-Phenylalanine)(4) showed that SL-PS was covered with 70%, 50% and 0%, respectively. This showed that spontaneous wet adhesion on PS increases with the number of amino acids hydroxyl groups. This is also supported with the density functional theory (DFT) energy calculations and ab-initio molecular dynamics (AIMD) simulations. In water, interactions between water molecules and hydroxyl groups on the catechol induce catechol adhesion via 7C-7C stacking between the catechol and double styrene rings which were already tilted out with water.