No abstract

Laser-induced breakdown spectroscopy (LIBS), which is an excellent tool for trace elemental analysis, was studied as a method of detecting sub-part-per-10 6 (ppm) concentrations of aluminum in surrogates of human tissue. Tissue was modeled using a 2% agarose gelatin doped with an Al 2 O 3 nanoparticle suspension. A calibration curve created with standard reference samples of known Al concentrations was used to determine the limit of detection, which was less than 1 ppm. Rates of false negative and false positive detection results for a much more realistic sampling methodology were also studied, suggesting that LIBS could be a candidate for the real-time in vivo detection of metal contamination in human soft tissue.

lived component is similar to that of 6-MI monomer, 7 ns. The position of the probe shifts the fluorescent populations from 0.4 ns to 6.5ns upon formation of duplex, which implies that 6-MI local environment in these positions resembles that of the solvent exposed monomer. However, no direct correlation between adjacent base sequence and the fluorescent properties of 6MI was observed. To further investigate the increase in fluorescence upon duplex formation, we characterized the local and global structure of several oligonucleotides through temperature melts, quantum yield calculations, quenching assays, and Raman spectroscopy. The results suggest that, the position of 6-MI in the duplex sequence, helical turn, and surrounding base sequence determines the dynamics of 6-MI. This potentially leads to the formation of a fixed geometry of 6-MI which stacks poorly with adjacent bases. The lack of stacking interactions causes 6-MI to exhibit fluorescent properties of the monomer.

Nanoparticles have been conjugated to proteins to create unique imaging agents, multifunctional particles, and drug delivery vehicles. However, the biggest barrier for the success of these applications is understanding the interface of biomolecules with nanoparticles. Often conjugation of proteins and DNA with nanoparticles results in protein denaturation and non-specific adsorption, which are due to the many non-covalent interactions at the inorganic-biological interface. While development of new biological applications of nanoparticles has garnered a great deal of attention, the protein-nanoparticle interface has remained poorly characterized. As a result, insufficient understanding of the interface has limited the capabilities of nano-bio hybrids. We present work in which we study the interface between inorganic nanoparticles of Au and CoFe2O4 and the protein cytochrome c, which is covalently linked to the nanoparticle. We devise a method to site-specifically label the protein, minimizing non-specific adsorption. We study the effect of nanoparticle ligand, nanoparticle material, and protein labeling site on the structure of the protein. Biophysical techniques such as quantitative gel electrophoresis, circular dichroism, and optical spectroscopy are used to characterize the structure of the protein in the conjugate. These experiments allow us to understand the chemical interactions involved in non-specific adsorption, and come up with general design rules for optimal conjugation. We determine that nanoparticle labeling generally destabilizes the motif containing the labeling site, and that when the nanoparticle is labeled on certain motifs, protein denaturation is not recoverable.