Matjaž Ličen, 20.4.2018 at 13:00 in F7 Seminar room

Photoregulating the self-assembly of lipophilic guanosine derivaters at the air-water interface
Odsek za kompleksne snovi, IJS


Basic blocks of DNA are very interesting constituents for designing supramolecular single-layer and multilayer surface  architectures. Our recent studies of self-assembly of nucleoside derivatives in monolayer films at the air-water interface (Langmuir films) reveal that guanosine derivatives exhibit very different behaviour from analogous derivatives containing other nucleobases [1]. We also demonstrated that the number of lipophilic chains attached to the sugar hydroxyl groups and the type/concentration of ions present in the water subphase strongly affected molecular organization of guanosine derivatives in Langmuir monolayers as well as in Langmuir-Blodgett (LB) films deposited on various solid substrates [2,3,4]. Modifications of these parameters hence provide a possibility of tuning intermolecular organization in thin film configurations.  An appealing strategy for control and manipulation of intermolecular organization is to use optical irradiation. To test the applicability of this method in case of guanosine derivatives we investigated Langmuir films of azo-functionalised guanosine molecules in which the isomerization can be switched from trans to cis and vice versa by irradiation with UV and visible light. Photoinduced modifications within Langmuir films were studied by film balance experiments and by Brewster angle microscopy (BAM). We were able to reversibly induce changes in the surface pressure of the film by alternatingly irradiating with UV and blue light, indicating a light-induced change in the film structure. The measurements for several different films mixed from a photoactive guanosine derivative and other non-photoactive nucleosides were compared to a simplified model of the film. The results from the model are in good agreement with the measurements for all films, except for the film formed by mixing guanosine and cytidine molecules, which hints at specific bonding between these two molecules.

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[2] M. Devetak, S. Masiero, S. Pieraccini, G. P. Spada, M. Copic, and I. Drevensek Olenik, Appl. Surf. Sci. 256,2038  2043 (2010)
[3] L. Coga, S. Masiero, and I. Drevensek Olenik, Colloid. Surface B 121, 114 – 121 (2014)
[4] L. Coga, S. Masiero, and I. Drevensek Olenik, Langmuir 31, 4837 – 4843 (2015)