Evidence for Proximal Control of Ligand Specificity in Hemeproteins: Absorption and Raman Studies of Cryogenically Trapped Photoproducts of Ligand Bound Myoglobins

The absorption and resonance Raman spectra of cryogenically trapped photoproducts of oxy and carboxy derivatives of myoglobin (Mb) are compared and analyzed in an attempt to understand the structural basis for ligand specificity in hemeproteins. Pulsed and cw excitations over a wide temperature range are used in order to differentiate between kinetic hole burning (KHB), optical pumping of structural relaxation, and spontaneous relaxation effects. Using these techniques, we are able to correlate changes in the absorption spectrum (band III at ≈ 760 nm) with low-frequency Raman bands. Based on these correlations we are able to determine which proximal heme pocket parameters are participating in KHB and optical pumping phenomena. Differences in the spectra of the ligand specific photoproducts have revealed differences in the populations of conformational substates (CS) that participate in the geminate recombination (process I) at cryogenic temperatures. A model is presented that relates the ligand specific spectral differences to structural and functional differences in the bound protein. What emerges is evidence that Mb and hemoglobin (Hb) can differentiate between O2 and CO based on proximal control of the bond forming step between the ligand and the iron. © 1991

Temperature Dependent Coordination Effects in Base-Off Adenosyl and Methylcobalamin by X-Ray Edge Spectroscopy

Examination of the role of base-off cobalamin species (where the 5,6-dimethylbenzimidazole ligand coordinated to cobalt is detached by protonation of the imidazole nitrogen) in differentiation between homolytic and heterolytic cobalt-carbon bond cleavage mechanisms is a primary step in better understanding B12-dependent enzyme catalysis. X-ray absorption edge spectroscopy provides the first direct structural evidence of five-coordination in base-off adenosyl- and base-off methylcobalamin complexes at room temperature. Integration of 1s-3d pre-edge transitions of the base-off species reveals the dependence of coordination number on temperature. Gradual increases in 1s-3d transition intensities, as the temperature is increased from 180 K to 298 K, reflect a change in the coordination number from six (where a water molecule is presumed to occupy the coordination site vacated by the 5,6-dimethylbenzimidazole ligand) to primarily five-coordinate. Base-off configurations that strengthen the CoC bond may be both decreasing the tendency for homolytic cleavage while increasing the tendency for hetrolytic Co(I) B12 formation

CIVIL PRACTICE Verdict and Judgment: Provide for Discharge of Liens Against Real and Personal Property

The Act provides that when a bona fide purchaser has been in possession of real property for four years or personalty for two years, the property shall be discharged from the lien of any judgment against the seller or any predecessor in title

Super Terror: The Complex Relationship Between Sequential Art and Real World Political Violence

While scholars have recognized that the media plays a very important role in the understanding of terrorism and other forms of political violence, alternative and popular forms of media (such as the Comic Strip, Graphic Novel, Cartoon, etc.) have not been examined as closely by social scientists. This research is concerned with the reaction by graphic narratives to events of terror and the graphic work as a way of influencing the public in its opinion of terror. The main piece examined is Alan Moore’s V for Vendetta which was made as a discussion of the justification of terror witch specific historical examples such as Guy Fawkes and political violence in Ireland. Another text that this paper explores is The 9/11 Report Graphic Adaptation that is a graphic work that was made in response to the September 11th terrorist attacks in an attempt to better educate the masses about the events leading up to the attack. In contrast to this, I will examine Paul Jenkin’s Marvel Civil War: Front Line, a superhero narrative which actively criticizes United States governmental policy post 9-11. This research also starts a discussion of visual codes in Geoff John’s Green Lantern series that shows and then counters different stereotypes of Arab Americans that resulted from the aftermath of September eleventh and the War on Terror

PROPERTY Landlord and Tenant: Amend Dispossessory Proceedings

The Act provides that a writ of possession shall enter instantly if a tenant fails to answer a summons as provided in dispossessory proceedings. The Act further provides that if, upon trial of the case, judgment is entered against the tenant, the trial court shall issue a writ of possession and a writ of execution to be effective at the expiration of ten days after the judgment is entered. Finally, the Act provides that if the judgment is against the tenant, the court may upon motion of the landlord and upon good cause shown order the tenant to pay rent into the registry of the court in order to remain in possession of the premises during the appellate process

DNA Binding Provides a Molecular Strap Activating the Adenovirus Proteinase

Human adenovirus proteinase (AVP) requires two cofactors for maximal activity: pVIc, a peptide derived from the C terminus of adenovirus precursor protein pVI, and the viral DNA. Synchrotron protein footprinting was used to map the solvent accessible cofactor binding sites and to identify conformational changes associated with the binding of cofactors to AVP. The binding of pVIc alone or pVIc and DNA together to AVP triggered significant conformational changes adjacent to the active site cleft sandwiched between the two AVP subdomains. In addition, upon binding of DNA to AVP, it was observed that specific residues on each of the two major subdomains were significantly protected from hydroxyl radicals. Based on the locations of these protected side-chain residues and conserved aromatic and positively charged residues within AVP, a three-dimensional model of DNA binding was constructed. The model indicated that DNA binding can alter the relative orientation of the two AVP domains leading to the partial activation of AVP by DNA. In addition, both pVIc and DNA may independently alter the active site conformation as well as drive it cooperatively to fully activate AVP

Formation of a Square-Planar Co(I) B12 Intermediate. Implications for Enzyme Catalysis

X-ray edge and extended x-ray absorption fine structure (EXAFS) techniques provide powerful tools for analysis of local molecular structure of complexes in solution. We present EXAFS results for Co(I) B12 that demonstrate a four-coordinate (distorted) square-planar configuration. Comparison of EXAFS solutions for Co(I) and Co(II) B12 (collected previously; Sagi et al. 1990. J. Am. Chem. Soc. 112:8639–8644) suggest that modulation of the Co-N bond to the axial 5,6-dimethylbenzimidazole (DMB), in the absence of changes in Co-N (equatorial) bond distances, may be a key mechanism in promoting homolytic versus heterolytic cleavage. As Co-C bond homolysis occurs, the Co-N (DMB) bond becomes stronger. However, for heterolytic cleavage to occur, earlier electrochemical studies (D. Lexa and J. M. Saveant. 1976. J. Am. Chem. Soc. 98:2652–2658) and recent studies of methylcobalamin-dependent Clostridium thermoaceticum (Ragsdale et al. 1987. J. Biol. Chem. 262:14289–14297) suggest that removal of the DMB ligand (before Co-C bond cleavage) favors formation of the four-coordinate square-planar Co(I) species while inhibiting formation of the five-coordinate Co(II) B12 complex. This paper presents the first direct evidence that formation of the Co(I) B12 intermediate must involve breaking of the Co-N (DMB) bond

Purification of a Variant-specific Surface Protein of Giardia lamblia and Characterization of its Metal-binding Properties

Giardia lamblia, an intestinal parasite of humans and other vertebrates, undergoes surface antigenic variation by modulating the expression of different variant-specific surface proteins (VSP). VSPs are cysteine-rich surface proteins that bind zinc and other heavy metals in vitro. We developed an immunoaffinity chromatographic method to purify a VSP in order to determine its biochemical properties. The sequences of two different proteolytic fragments agreed with the sequence deduced from the cloned gene, and amino-terminal sequence indicated the removal of a 14-residue signal peptide, consistent with the transport of VSP to the cell surface. The protein is not glycosylated and has an isoelectric point of 5.3. X-ray microanalyses indicated that the major metals in Giardia trophozoites, as well as purified VSP, are zinc and iron. The zinc concentration in Giardia cells was found to be 0.43 mM and the iron concentration 0.80 mM when compared with standard samples (zinc) or calculated from a known physical constants (iron). We propose that metal coordination stabilizes VSPs, rendering them resistant to proteolytic attack in the upper small intestine. Moreover, the ability to bind ions by Giardia may play a role in nutritional deficiency and/or malabsorption in heavily infected persons

Moving Forward: Expanding the Digital Marketing and Information Technology Strategy of a Thriving Nonprofit

The purpose of the project was to expand the digital marketing efforts and volunteer reporting and training processes of a thriving nonprofit healthcare organization. In 2015, the organization had an aging Web presence, disparate marketing systems, and inconvenient volunteer reporting and training processes. The project consisted of four central goals: improve website content management and update processes, improve website usability and digital marketing efforts, improve volunteer documentation and reporting processes, and improve volunteer training processes through accessible education resources. Utilizing a modest budget, the project team sought to improve marketing and information technology processes within the organization by implementing modern technology solutions, integrating systems, and providing convenient resources to stakeholders. The project resulted in a responsive website design, a reduction in ongoing website expenses, online event management and self-service ticketing for fundraising events, an email marketing and social media advertising strategy, HIPAA compliant volunteer reporting processes, and an online volunteer training program

Optical properties of current carrying molecular wires

We consider several fundamental optical phenomena involving single molecules in biased metal-molecule-metal junctions. The molecule is represented by its highest occupied and lowest unoccupied molecular orbitals, and the analysis involves the simultaneous consideration of three coupled fluxes: the electronic current through the molecule, energy flow between the molecule and electron-hole excitations in the leads and the incident and/or emitted photon flux. Using a unified theoretical approach based on the non-equilibrium Green function method we derive expressions for the absorption lineshape (not an observable but a ueful reference for considering yields of other optical processes) and for the current induced molecular emission in such junctions. We also consider conditions under which resonance radiation can induce electronic current in an unbiased junction. We find that current driven molecular emission and resonant light induced electronic currents in single molecule junctions can be of observable magnitude under appropriate realizable conditions. In particular, light induced current should be observed in junctions involving molecular bridges that are characterized by strong charge transfer optical transitions. For observing current induced molecular emission we find that in addition to the familiar need to control the damping of molecular excitations into the metal substrate the phenomenon is also sensitive to the way in which the potential bias si distributed on the junction.Comment: 56 pages, 8 figures; submitted to JC