Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

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

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Author: search.filters.author.Han, SongiPublication Index: search.filters.publicationIndex.PubMed

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  • Article
    Citation - WoS: 66
    Citation - Scopus: 71
    Signature of an Aggregation-Prone Conformation of Tau
    (Nature Publishing Group, 2017) Eschmann, Neil A.; Georgieva, Elka R.; Ganguly, Pritam; Borbat, Peter P.; Rappaport, Maxime D.; Akdoğan, Yaşar; Freed, Jack H.; Shea, Joan-Emma; Han, Songi
    The self-assembly of the microtubule associated tau protein into fibrillar cell inclusions is linked to a number of devastating neurodegenerative disorders collectively known as tauopathies. The mechanism by which tau self-assembles into pathological entities is a matter of much debate, largely due to the lack of direct experimental insights into the earliest stages of aggregation. We present pulsed double electron-electron resonance measurements of two key fibril-forming regions of tau, PHF6 and PHF6∗, in transient as aggregation happens. By monitoring the end-to-end distance distribution of these segments as a function of aggregation time, we show that the PHF6 (∗) regions dramatically extend to distances commensurate with extended β-strand structures within the earliest stages of aggregation, well before fibril formation. Combined with simulations, our experiments show that the extended β-strand conformational state of PHF6 (∗) is readily populated under aggregating conditions, constituting a defining signature of aggregation-prone tau, and as such, a possible target for therapeutic interventions.
  • Article
    Citation - WoS: 58
    Citation - Scopus: 86
    Intrinsic Surface-Drying Properties of Bioadhesive Proteins
    (John Wiley and Sons Inc., 2014) Akdoğan, Yaşar; Wei, Wei; Huang, Kuo-Ying; Kageyama, Yoshiyuki; Danner, Eric W.; Miller, Dusty R.; Martinez Rodriguez, Nadine R.; Waite, J. Herbert; Han, Songi
    Sessile marine mussels must "dry" underwater surfaces before adhering to them. Synthetic adhesives have yet to overcome this fundamental challenge. Previous studies of bioinspired adhesion have largely been performed under applied compressive forces, but such studies are poor predictors of the ability of an adhesive to spontaneously penetrate surface hydration layers. In a force-free approach to measuring molecular-level interaction through surface-water diffusivity, different mussel foot proteins were found to have different abilities to evict hydration layers from surfaces - a necessary step for adsorption and adhesion. It was anticipated that DOPA would mediate dehydration owing to its efficacy in bioinspired wet adhesion. Instead, hydrophobic side chains were found to be a critical component for protein-surface intimacy. This direct measurement of interfacial water dynamics during force-free adsorptive interactions at solid surfaces offers guidance for the engineering of wet adhesives and coatings. Home and dry underwater: Repulsive hydration forces hinder wet adhesion in the absence of applied external forces. The direct measurement of hydration-water dynamics by NMR relaxometry at 10 GHz revealed that the most hydrophobic mussel adhesive protein, and not the most enriched with 3,4-dihydroxyphenylalanine, effectively dries the surface and overcomes repulsive hydration forces to adsorb spontaneously to surfaces in preparation for adhesion.