DNA-hosted silver clusters (Ag:DNAs) have attracted a lot of attention due to their small size (~20 atoms), wide range of applications in chemistry and biology, and sequence-dependent optical... Show moreDNA-hosted silver clusters (Ag:DNAs) have attracted a lot of attention due to their small size (~20 atoms), wide range of applications in chemistry and biology, and sequence-dependent optical tunability. Most of the previous studies are focused on the ensemble of emitters in solution. However, little is known about the optical properties of individual emitters, which is a crucial step towards understanding of their real nature, otherwise lost in ensemble averaging. We show that the excitation and emission spectra of individual emitters are broad even at 1.7 K (FWHM ~25 nm). Also, polarization measurements indicate that the excitation is not strongly dependent on the polarization of excitation light, whereas the emission is highly linearly polarized. Furthermore, from time-resolved measurements, we can conclude that the emission of single emitters can be fitted with single exponential decay curve, whereas the emitters organized with nanometer precision on the DNA scaffolds show double–exponential decay. This indicates the interaction between densely packed Ag:DNAs. Finally, we show that the DNA tubes can be used as a nano-contact glue between the colloidal particles functionalized with short DNA strands. Show less
Diffusion-weighted magnetic resonance spectroscopy (DW-MRS) can play a key role in understanding neurobiological mechanisms of diseases that affect the human brain. The specific changes that occur... Show moreDiffusion-weighted magnetic resonance spectroscopy (DW-MRS) can play a key role in understanding neurobiological mechanisms of diseases that affect the human brain. The specific changes that occur within neurons can be reflected as changes in the diffusivity of tNAA, whereas the changes in glial cells can cause pronounced changes in the diffusivities of tCr and tCho. This information combined with that obtained from diffusion tensor imaging (DTI) and other MRI tools can help elucidate various disease processes in the future. The main purposes of this thesis are (i) to investigate neuroanatomy in vivo with DW-MRS, (ii) to develop methodology to enable future clinical applications of the technique in human brain in vivo, and (iii) to characterize the microstructural deficit in neuropsychiatric systemic lupus erythematous (NPSLE) with DW-MRS and other microstructural tools such as DTI and magnetization transfer imaging. The studies presented in this thesis show the robustness and clinical relevance of microstructural information obtained via DW-MRS. The contributions of this thesis such as the optimized acquisition protocols for single volume DW-MRS, the robust DW-CSI and DW-MRS post-processing pipelines that comprise information from DTI, will all facilitate the applications of DW-MRS both for basic neuroscience research and clinical research studies. Show less
