Tools for Prescreening the Most Active Sites on Ir and Rh Clusters toward C−H Bond Cleavage of Ethane: NBO Charges and Wiberg Bond Indexes

B3LYP calculations were carried out to study the insertion of iridium (Ir) and rhodium (Rh) clusters into a C−H bond of ethane, which is often the ratelimiting step of the catalytic cycle of oxidative dehydrogenation of ethane. Our previous research on Ir catalysis correlates the diffusivity of the lowest unoccupied molecular orbital of the Ir clusters and the relative activities of the various catalytic sites. The drawback of this research is that the molecular orbital visualization is qualitative rather than quantitative. Therefore, in this study on C−H bond activation by the Ir and Rh clusters, we conducted analyses of natural bond orbital (NBO) charges and Wiberg bond indexes (WBIs), both of which are not only quantitative but also independent of the basis sets. We found strong correlation between the NBO charges, the WBIs, and the relative activities of the various catalytic sites on the Ir and Rh clusters. Analyses of the NBO charges and the WBIs provide a fast and reliable means of prescreening the most active sites on the Ir and Rh clusters and potentially on other similar transition-metal clusters that activate the C−H bonds of ethane and other light alkanes

Investigation into the Structure and Function of l-Mgm1 in inner mitochondrial membrane fusion

Mitochondria are key components of the cell as they provide energy in the form of ATP through cellular respiration. A balance of fission and fusion maintains a dynamic, inter-connected mitochondrial network, which is important for overall function. When fusion is disrupted, the mitochondrial network becomes fragmented, mitochondrial genomes are lost, and respiration ceases. Mitochondrial inner membrane fusion is mediated by the GTP hydrolase Mgm1 (Mitochondrial Genome Maintenance 1) in yeast. Yeast make an excellent model system to study mitochondrial physiology since they are not dependent on respiration for growth. Mgm1 exists as a membrane embedded long isoform (l-Mgm1) and a soluble short isoform (s-Mgm1). Both l-Mgm1 and s-Mgm1 are required for inner membrane fusion, but the role of l-Mgm1 remains unclear. Our goal is to determine the regions of l-Mgm1 that are important for fusion activity. To do this, we employed a polymerase chain reaction (PCR) splicing by overlapping extension (SOE) technique to make versions of l-Mgm1 with regions removed. Once constructed, we will test the mutated l-Mgm1 proteins with yeast physiology assays to determine effects on mitochondrial fusion, mitochondrial genome maintenance, and respiration. Construction of the l-Mgm1 mutants has proven challenging. I am currently optimizing the PCR conditions to complete this phase of the project. In the meantime, I am becoming familiar with yeast culturing techniques and physiological assays