Spectroscopic studies of biomolecules confined in self-assembled nanostructures

Doctoral thesis, 2013

The present thesis examines the effects of incorporating biomolecules into self-assembled nanostructures. This approach is exemplified by short DNA molecules in environments close to lipid bilayers and the immobilization of enzymes into mesoporous silica particles. The biomolecules and attached chromophore probes are studied in the nanostructures using optical spectroscopy. An important part of the thesis work is the spectroscopical considerations enforced by the complex samples formed by the biomolecules and the nanostructures. The small confining spaces rich in surfaces have effects on the physical properties of the nanostructures. The movement of the large biomolecules are hindered by the narrow environments and this is utilized for electrophoretic separation and orientation of oligonucleotides in lyotropic liquid crystals. The cubic phase of the monoolein-water system was shown to act as an electrophoresis matrix for both water soluble oligonucleotides and bilayer anchored molecules. The lamellar phase of the sodium octanoate-decanol-water system was used to introduce macroscopic ordering of oligonucleotides and bilayer bound chromophores for studies by linear dichroism. In addition to the orientational effects of the chromophores interacting with the lipid bilayers, spectral effects of the bilayer environment were also studied. In the spectroscopic studies of enzyme immobilized into mesoporous silica particles the pore pH were found to be slightly different compared to the external volume. Furthermore, direct spectroscopic determination of the pore loading was examined in contrast to common indirect approaches. Finally, the concept of pore filling as an analysis tool and the particle size influence on immobilization are discussed.