With the proliferation of global climate change, farmers in economically developing countries find it becomes ever more difficult to meet basic needs. Often times, access to formal insurance markets, such as the markets we see in America today, in developing countries is minimal and households find that they must use informal insurance mechanisms in order to help mediate their risk. My research asks whether households in Thailand send migrants out with the intention of receiving income from these family members in order to account for potentially lost income during years that crop yield is notably lower because of unexpected environmental changes. I answer this question by estimating a two stage least squares model with environmental shocks as the instrumental variable. My project fills the current gaps in the literature by looking at the effects of long-term environmental shocks versus short-term environmental shocks on the change in income from remittances. I also contribute to the current literature by focusing on the impact of migrants that are still living and working within the country but outside of the household.

Research has shown that exposure to biomass smoke can lead to adverse health effects. However, the potential impacts of how wood smoke (WS) sources influence health outcomes are unknown. Wildfire and residential WS particulate matter (PM) are health risks to the general population, as well as a source of occupational exposure to those fighting wildfires. These different sources of WS likely constitute different hazards, especially in small mountain communities where wood or other solid fuels are easily accessible. In order to investigate the potential impacts following exposures to these different sources, the particles released during these different burning events were harvested and employed in an in vitro model to explore the potential effects on macrophage pro-inflammatory activity and cell viability. In the lung, macrophages are the front line of defense when inhaling foreign particles (e.g., dust, pathogens, etc.) and can trigger an immune response. This response is largely dependent on the source (or chemistry) of the inhaled particles. Determining the impact of these inhaled particles on macrophages will improve our understanding of how WS sources influence health.

Using a versatile aerosol concentration enrichment system particle concentrator (VACES-PC), WS was harvested for the planned in vitro studies. Wildfire PM was harvested on the roof of the Skaggs building on the University of Montana’s campus downwind from a wildfire occurring just outside of Lolo, Montana in 2013. Wood stove WS particles were harvested from both an “old” wood stove and an EPA-certified wood stove chimney during burns. Each particle type was then concentrated into stock solutions. In a dose-response manner using a human cell line (THP-1 macrophages), cells were exposed to the three different sources of WS and controls (i.e. NIST 1648 standard for urban particulate matter and SiO₂). Results demonstrate that wildfire WS is significantly more pro-inflammatory than particles from an “old” wood stove, an EPA-certified wood stove, and urban particulate matter. Also, other measures (i.e., endotoxin burden) show significant differences in source chemistry. These data suggest that the source of WS likely plays a significant role in health outcome.

The folding of proteins into their native states is a requirement for proper function. Proteins that aggregate or fail to fold correctly can lead to many proteopathic diseases, including but not limited to, Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and prion diseases.¹ Christian Anfinsen famously postulated that the amino acid sequence was the determinate of the native fold in small globular proteins. Here we investigate the lysine residue found at position 72 in an important conserved region of cytochrome c called the heme-crevice loop. The heme-crevice loop plays an important part in regulating cytochrome c’s ability to transfer electrons in the electron transport chain helping to make the energy molecule ATP, and to oxidize the mitochondrial membrane lipid cardiolipin during programmed cell death.

For this investigation we made a mutation at position 72 from a large, basic lysine (K72) residue to a small, non-polar alanine (K72A) residue. This allows us to measure changes that the protein undergoes in its overall stability, local movement of the heme-crevice loop, and changes in the functions discussed above. Cytochrome c has a covalently bound heme group. This is the part of the protein that allows the chemistry of electron transfer and peroxidase activity (catalyzing the H₂O₂ to H₂O reaction) to take place. Other lysine residues such as those at positions 79 and to a lesser extent 73 have been shown to have the ability to swing in and displace the natively bound residue (methionine 80, M80) once they lose a proton at alkaline/basic pH. While investigating residue 72, we discovered that this lysine may in fact also bind to the heme during the alkaline conformational transition, which was previously thought not to take place based on studies with horse heart cytochrome c.² (The replacement of the natively bound heme ligand, M80, with alternative ligands is called the alkaline conformational transition).

When K72 is replaced with an alanine we see an increase in the pKa (the pH where half of the protein is in the native conformer and half is in the alkaline conformer) compared to the native (WT) protein (9.54±0.03 for WT to 10.00±0.13 for K72A). This means that the native M80 bound state is being stabilized. We pursued this interesting observation with stopped-flow pH Jumps. This experiment allows us to quickly change the pH of our protein and monitor the heme-crevice loop adjusting to the rapid change in pH. Fitting these data, we can determine the number of protons (n) that are involved in each binding reaction. When we fit for WT we get n = 2.32±0.18 and for K72A we get n=1.08±0.016. This shows that one more proton is involved in the WT jump compared to the K72A jump. Lastly, we examined the peroxidase activity of cytochrome c. Here we saw a sharp separation of WT and K72A peroxidase activity with increasing pH. As M80 is weakly bound, we see increased peroxidase activity. This observation indicates that K72 is important for controlling peroxidase activity.

1) Walker, Lary C., Harry Levine, Mark P. Mattson, and Mathias Jucker. "Inducible Proteopathies." Trends in Neurosciences 29.8 (2006): 438-43.

2) Hoang, Linh, Haripada Maity, Mallela M.G. Krishna, Yan Lin, and S. Walter Englander. "Folding Units Govern the Cytochrome C Alkaline Transition." Journal of Molecular Biology 331.1 (2003): 37-43.