The measurement of art judgment in everyday life.

Thesis (Ed.M.)--Boston Universit

Photo-Activation of 2,2’-Bipyridine-Sulfur Oxides Donor-Acceptor Complex

The work presented in this thesis discusses the synthesis of a novel photochromic molecule which is induced by a bipyridine-sulfur dioxide (SO2) charge transfer mechanism. SO2 is produced in large quantities by many industrial processes, and great effort is spent to reduce its emission. SO2 is an underutilized feedstock for chemical reactions and functional materials alike, so great interest is applied to new uses of this byproduct.Photochromic bipyridines typically appear N, N’-disubstituted-4,4’-bipyridines, known as viologens. Following exposure to UV light, viologens undergo a one electron reduction to a blue colored radicle cation. This radicle cation is easily detectable by EPR spectroscopy. The photochromic bipyridine presented in this work undergoes a color change from light yellow to magenta upon irradiation, resulting in a new absorption peak at 550 nm. The EPR spectroscopy of the irradiated colored product does not detect any radicles, which suggests a new mechanism different from viologens. The present bipyridine containing system exhibits photochromic response for small molecule solids, small molecule solutions, and polymeric systems. Each of these environments exhibit tunable color change. Small molecule solutions and polymeric systems exhibit t-type photochromic behavior. DFT calculations were performed on the photochromic small molecule complexed with SO2. The results of these calculations indicate that photochromism is attributed to a UV-induced bipyridine-SO2 bond strengthening. The decrease of N-S bond length lowers the energy of the of the charge transfer band into the visible range. This represents a new class of photo-responsivity which can be applied to various applications common to photo switching materials. The concluding remarks suggest future directions of mechanistic studies as well as implementation of the photoproduct in film fabrication, and as a light induced mechano-responsive material

Axon regeneration: Vaccinating against spinal cord injury

AbstractMyelin is a potent inhibitor of axon regeneration, but has been viewed as just one of many factors that prevent regeneration after injury. So it comes as a surprise that immunization against myelin has been found to allow extensive axon regeneration after injury, without apparent autoimmune-induced demyelination

Implications of Dam Removal: Modeling Streamflow in Lansing, Michigan Using the Soil and Water Assessment Tool

This paper uses hydrologic modeling methods to determine the effects of dam removal in Lansing, Michigan, on the streamflow of the Grand River, flooding risks, and flood mitigation strategies. In Michigan, more than one-half of the state’s dam infrastructure is more than 50 years old, and more than one-third are classified as having a moderate-to high-risk potential. Lansing, Michigan, contains two moderate-to high-risk dams along the Grand River that are a significant hazard to the surrounding community in the event of structural failure. This research utilizes the Soil and Water Assessment Tool (SWAT) to model the impacts of the Moores Park Dam and the North Lansing Dam on streamflow in the greater Lansing area. The purpose of using SWAT was to represent baseline streamflow conditions in the Grand River, compare the differences in streamflow magnitude between baseline conditions and a dam-out environment, and interpret the implications of modeling results for mitigation and management strategies in the study area. Our model exhibited similar streamflow patterns to USGS historical data, with overestimation errors during calibration and validation stemming from groundwater infiltration inaccuracies. The dams-out model for streamflow was higher than the baseline model for streamflow; however, both model iterations require further calibration and validation for the magnitude differences to be considered statistically significant. Despite issues of model calibration and validation, and ongoing model adjustments for accurately representing heavily impounded watershed, the results of this study provide a template for the City of Lansing to adapt their flood mitigation strategies in the study area and further calibrate SWAT with improved sediment, nutrient, and dam attribute data

Myelin-associated Glycoprotein Interacts with Neurons via a Sialic Acid Binding Site at ARG118 and a Distinct Neurite Inhibition Site

Inhibitory components in myelin are largely responsible for the lack of regeneration in the mammalian CNS. Myelin-associated glycoprotein (MAG), a sialic acid binding protein and a component of myelin, is a potent inhibitor of neurite outgrowth from a variety of neurons both in vitro and in vivo. Here, we show that MAG's sialic acid binding site is distinct from its neurite inhibitory activity. Alone, sialic acid–dependent binding of MAG to neurons is insufficient to effect inhibition of axonal growth. Thus, while soluble MAG-Fc (MAG extracellular domain fused to Fc), a truncated form of MAG-Fc missing Ig-domains 4 and 5, MAG(d1-3)-Fc, and another sialic acid binding protein, sialoadhesin, each bind to neurons in a sialic acid– dependent manner, only full-length MAG-Fc inhibits neurite outgrowth. These results suggest that a second site must exist on MAG which elicits this response. Consistent with this model, mutation of arginine 118 (R118) in MAG to either alanine or aspartate abolishes its sialic acid–dependent binding. However, when expressed at the surface of either CHO or Schwann cells, R118-mutated MAG retains the ability to inhibit axonal outgrowth. Hence, MAG has two recognition sites for neurons, the sialic acid binding site at R118 and a distinct inhibition site which is absent from the first three Ig domains

HCV IRES manipulates the ribosome to promote the switch from translation initiation to elongation.

The internal ribosome entry site (IRES) of the hepatitis C virus (HCV) drives noncanonical initiation of protein synthesis necessary for viral replication. Functional studies of the HCV IRES have focused on 80S ribosome formation but have not explored its role after the 80S ribosome is poised at the start codon. Here, we report that mutations of an IRES domain that docks in the 40S subunit's decoding groove cause only a local perturbation in IRES structure and result in conformational changes in the IRES-rabbit 40S subunit complex. Functionally, the mutations decrease IRES activity by inhibiting the first ribosomal translocation event, and modeling results suggest that this effect occurs through an interaction with a single ribosomal protein. The ability of the HCV IRES to manipulate the ribosome provides insight into how the ribosome's structure and function can be altered by bound RNAs, including those derived from cellular invaders

Crystal structure of the Nogo-receptor-2

The inhibition of axon regeneration upon mechanical injury is dependent on interactions between Nogo receptors (NgRs) and their myelin-derived ligands. NgRs are composed of a leucine-rich repeat (LRR) region, thought to be structurally similar among the different isoforms of the receptor, and a divergent “stalk” region. It has been shown by others that the LRR and stalk regions of NgR1 and NgR2 have distinct roles in conferring binding affinity to the myelin associated glycoprotein (MAG) in vivo . Here, we show that purified recombinant full length NgR1 and NgR2 maintain significantly higher binding affinity for purified MAG as compared to the isolated LRR region of either NgR1 or NgR2. We also present the crystal structure of the LRR and part of the stalk regions of NgR2 and compare it to the previously reported NgR1 structure with respect to the distinct signaling properties of the two receptor isoforms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83453/1/597_ftp.pd