Chemistry Commons^™

Gfsa Encodes A Novel Galactofuranosyltransferase Involved In Biosynthesis Of Galactofuranose Antigen Of O-Glycan In Aspergillus Nidulans And Aspergillus Fumigatus, Yuji Komachi, Shintaro Hatakeyama, Haruka Motomatsu, Taiki Futagami, Karina Kizjakina, Pablo Sobrado, Keisuke Ekino, Kaoru Takegawa, Masatoshi Goto, Yoshiyuki Nomura, Takuji Oka

Chemistry Faculty Research & Creative Works

Summary: The cells wall of filamentous fungi in the genus Aspergillus has galactofuranose (Galf)-containing polysaccharides and glycoconjugates, including O-glycans, N-glycans, fungal-type galactomannan and glycosylinositolphosphoceramide, which are important for cell wall integrity. Here, we attempted to identify galactofuranosyltransferases that couple Galf monomers onto other wall components in Aspergillus nidulans. Using reverse-genetic and biochemical approaches, we identified that the AN8677 gene encoded a galactofuranosyltransferase, which we called GfsA, involved in Galf antigen biosynthesis. Disruption of gfsA reduced binding of β-Galf-specific antibody EB-A2 to O-glycosylated WscA protein and galactomannoproteins. The results of an in-vitroGalf antigen synthase assay revealed that GfsA has β1,5- or …

N-Body:Many-Body Qm:Qm Vibrational Frequencies: Application To Small Hydrogen-Bonded Clusters, J. Coleman Howard, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

We present an efficient method for reproducing CCSD(T) (i.e., the coupled-cluster method with single, double and perturbative connected triple excitations) optimized geometries and harmonic vibrational frequencies for molecular clusters with the N-body:Many-body QM:QM technique. In this work, all 1-body through N-body interactions are obtained from CCSD(T) computations, and the higher-order interactions are captured at the MP2 level. The linear expressions from the many-body expansion facilitate a straightforward evaluation of geometrical derivative properties (e.g., gradients and Hessians). For (H₂O)_n clusters (n = 3-7), optimized structures obtained with the 2-body:Many-body CCSD(T):MP2 method are virtually identical to CCSD(T) optimized geometries. …

Examination Of Tyrosine/Adenine Stacking Interactions In Protein Complexes, Kari L. Copeland, Samuel J. Pellock, James R. Cox, Mauricio L. Cafiero, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

The π-stacking interactions between tyrosine amino acid side chains and adenine-bearing ligands are examined. Crystalline protein structures from the protein data bank (PDB) exhibiting face-to-face tyrosine/adenine arrangements were used to construct 20 unique 4-methylphenol/N9-methyladenine (p-cresol/9MeA) model systems. Full geometry optimization of the 20 crystal structures with the M06-2X density functional theory method identified 11 unique low-energy conformations. CCSD(T) complete basis set (CBS) limit interaction energies were estimated for all of the structures to determine the magnitude of the interaction between the two ring systems. CCSD(T) computations with double-ζ basis sets (e.g., 6-31G*(0.25) and aug-cc-pVDZ) indicate that the MP2 method overbinds …

Role Of Ser-257 In The Sliding Mechanism Of Nadp(H) In The Reaction Catalyzed By The Aspergillus Fumigatus Flavin-Dependent Ornithine N ⁵-Monooxygenase Sida, Carolyn Shirey, Somayesadat Badieyan, Pablo Sobrado

Chemistry Faculty Research & Creative Works

SidA (siderophore A) is a flavin-dependent N-hydroxylating monooxygenase that is essential for virulence in Aspergillus fumigatus. SidA catalyzes the NADPH- and oxygen-dependent formation of N5-hydroxyornithine. In this reaction, NADPH reduces the flavin, and the resulting NADP+ is the last product to be released. The presence of NADP+ is essential for activity, as it is required for stabilization of the C4a-hydroperoxyflavin, which is the hydroxylating species. As part of our efforts to determine the molecular details of the role of NADP(H) in catalysis, we targeted Ser-257 for site-directed mutagenesis and performed extensive characterization of the S257A enzyme. Using a combination of …

Substrate-Dependent Dynamics Of Udp-Galactopyranose Mutase: Implications For Drug Design, Leonardo Boechi, Cesar Augusto F. De Oliveira, Isabel Da Fonseca, Karina Kizjakina, Pablo Sobrado, John J. Tanner, J. Andrew Mccammon

Chemistry Faculty Research & Creative Works

Trypanosoma cruzi is the causative agent of Chagas disease, a neglected tropical disease that represents one of the major health challenges of the Latin American countries. Successful efforts were made during the last few decades to control the transmission of this disease, but there is still no treatment for the 10 million adults in the chronic phase of the disease. In T. cruzi, as well as in other pathogens, the flavoenzyme UDP-galactopyranose mutase (UGM) catalyzes the conversion of UDP-galactopyranose to UDP-galactofuranose, a precursor of the cell surface b-galactofuranose that is involved in the virulence of the pathogen. The fact that …

The Carriers Of The Interstellar Unidentified Infrared Emission Features: Constraints From The Interstellar C-H Stretching Features At 3.2-3.5 Μm, Xuejuan Yang, Rainer Glaser, Aigen Li, Jianxin Zhong

Chemistry Faculty Research & Creative Works

The unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm, commonly attributed to polycyclic aromatic hydrocarbon (PAH) molecules, have recently been ascribed to mixed aromatic/aliphatic organic nanoparticles. More recently, an upper limit of <9% was placed on the aliphatic fraction (i.e., the fraction of carbon atoms in aliphatic form) of the UIE carriers based on the observed intensities of the 3.4 μm and 3.3 μm emission features by attributing them to aliphatic and aromatic C-H stretching modes, respectively, and assuming A _3.4/A _3.3 ≈ 0.68 derived from a small set of aliphatic and aromatic compounds, where A _3.4 and A _3.3 are, respectively, the band strengths of the 3.4 μm aliphatic and 3.3 μm aromatic C-H bonds. To improve the estimate of the aliphatic fraction of the UIE carriers, here we analyze 35 UIE sources exhibiting both the 3.3 μm and …

Charge Transfer And Blue Shifting Of Vibrational Frequencies In A Hydrogen Bond Acceptor, Ashley M. Wright, Austin A. Howard, J. Coleman Howard, Gregory S. Tschumper, Nathan I. Hammer

Chemistry Faculty Research & Creative Works

A comprehensive Raman spectroscopic/electronic structure study of hydrogen bonding by pyrimidine with eight different polar solvents is presented. Raman spectra of binary mixtures of pyrimidine with methanol and ethylene glycol are reported, and shifts in ν₁, ν₃, ν_6a, ν_6b, ν_8a, ν_8b, ν_9a, ν₁₅, ν_16a, and ν_16b are compared to earlier results obtained for water. Large shifts to higher vibrational energy, often referred to as blue shifts, are observed for ν₁, ν_6b, and ν_8b (by as much …

Posterolateral Neck Texture (Insulin Neck): Early Sign Of Insulin Resistance, Katie S. Payne, Ryan K. Rader, Guido Lastra, William V. Stoecker

Chemistry Faculty Research & Creative Works

No abstract provided.

Targeting Udp-Galactopyranose Mutases From Eukaryotic Human Pathogens, Karina Kizjakina, John J. Tanner, Pablo Sobrado

Chemistry Faculty Research & Creative Works

UDP-Galactopyranose mutase (UGM) is a unique flavin-dependent enzyme that catalyzes the conversion of UDPgalactopyranose (UDP-Galp) to UDP-galactofuranose (UDP-Galf). The product of this reaction is the precursor to Galf, a major component of the cell wall and of cell surface glycoproteins and glycolipids in many eukaryotic and prokaryotic human pathogens. The function of UGM is important in the virulence of fungi, parasites, and bacteria. Its role in virulence and its absence in humans suggest that UGM is an ideal drug target. Significant structural and mechanistic information has been accumulated on the prokaryotic UGMs; however, in the past few years the research …

Synthesis And Fading Of Eighteenth-Century Prussian Blue Pigments: A Combined Study By Spectroscopic And Diffractive Techniques Using Laboratory And Synchrotron Radiation Sources, Louise Samain, Fernande Grandjean, Gary J. Long, Pauline Martinetto, Pierre Bordet, Jana Sanyova, David Strivay

Chemistry Faculty Research & Creative Works

Prussian blue, a hydrated iron(III) hexacyanoferrate(II) complex, is a synthetic pigment discovered in Berlin in 1704. Because of both its highly intense color and its low cost, Prussian blue was widely used as a pigment in paintings until the 1970s. The early preparative methods were rapidly recognized as a contributory factor in the fading of the pigment, a fading already known by the mid-eighteenth century. Herein two typical eighteenth-century empirical recipes have been reproduced and the resulting pigment analyzed to better understand the reasons for this fading. X-ray absorption and Mössbauer spectroscopy indicated that the early syntheses lead to Prussian …

Site-Specific Inter-Strand Cross-Links Of Dna Duplexes, Miao Ye, Johan Guillame, Yu Liu, Ruojie Sha, Risheng Wang, Nadrian C. Seeman, James W. Canary

Chemistry Faculty Research & Creative Works

We report the development of technology that allows inter-strand coupling across various positions within one turn of DNA. Four 2'-modified nucleotides were synthesized as protected phosphoramidites and incorporated into DNA oligonucleotides. The modified nucleotides contain either 5-atom or 16-atom linker components, with either amine or carboxylic acid functional groups at their termini, forming 10 or 32 atom (11 or 33 bond) linkages. Chemical coupling of the amine and carboxylate groups in designed strands resulted in the formation of an amide bond. Coupling efficiency as a function of trajectory distance between the individual linker components was examined. For those nucleotides capable …

Link Between Cancer And Alzheimer Disease Via Oxidative Stress Induced By Nitric Oxide-Dependent Mitochondrial Dna Overproliferation And Deletion, Gjumrakch Aliev, Mark E. Obrenovich, Shams Tabrez, Nasimudeen R. Jabir, Prakash Reddy, Yi Li, Geoffrey Burnstock, Ramon Cacabelos, Mohammad Amjad Kamal

Chemistry Faculty Research & Creative Works

Nitric oxide- (NO-) dependent oxidative stress results in mitochondrial ultrastructural alterations and DNA damage in cases of Alzheimer disease (AD). However, little is known about these pathways in human cancers, especially during the development as well as the progression of primary brain tumors and metastatic colorectal cancer. One of the key features of tumors is the deficiency in tissue energy that accompanies mitochondrial lesions and formation of the hypoxic smaller sized mitochondria with ultrastructural abnormalities. We speculate that mitochondrial involvement may play a significant role in the etiopathogenesis of cancer. Recent studies also demonstrate a potential link between AD and …

Sector Expansion And Elliptical Modeling Of Blue-Gray Ovoids For Basal Cell Carcinoma Discrimination In Dermoscopy Images, Pelin Guvenc, Robert W. Leander, Serkan Kefel, William V. Stoecker, Ryan K. Rader, Kristen A. Hinton, Sherea Monica Stricklin, Harold S. Rabinovitz, Margaret C. Oliviero, Randy Hays Moss

Chemistry Faculty Research & Creative Works

Background: Blue-gray ovoids (B-GOs), a critical dermoscopic structure for basal cell carcinoma (BCC), offer an opportunity for automatic detection of BCC. Due to variation in size and color, B-GOs can be easily mistaken for similar structures in benign lesions. Analysis of these structures could afford accurate characterization and automatic recognition of B-GOs, furthering the goal of automatic BCC detection. This study utilizes a novel segmentation method to discriminate B-GOs from their benign mimics.

Methods: Contact dermoscopy images of 68 confirmed BCCs with B-GOs were obtained. Another set of 131 contact dermoscopic images of benign lesions possessing B-GO mimics provided a …

Surface Temperature Effects On The Dynamics Of N₂ Eley-Rideal Recombination On W(100), Ernesto Quintas-Sánchez, C. Crespos, P. Larrégaray, J. C. Rayez, L. Martin-Gondre, J. Rubayo-Soneira

Chemistry Faculty Research & Creative Works

Quasiclassical trajectories simulations are performed to study the influence of surface temperature on the dynamics of a N atom colliding a N-preadsorbed W(100) surface under normal incidence. A generalized Langevin surface oscillator scheme is used to allow energy transfer between the nitrogen atoms and the surface. The influence of the surface temperature on the N₂ formed molecules via Eley-Rideal recombination is analyzed at T = 300, 800, and 1500 K. Ro-vibrational distributions of the N₂ molecules are only slightly affected by the presence of the thermal bath whereas kinetic energy is rather strongly decreased when going from a …

In Vivo Ultrasonic Detection Of Polyurea Crosslinked Silica Aerogel Implants, Firouzeh Sabri, Merry E. Sebelik, Ryan K. Meacham, John Dudley Boughter, Mitchell J. Challis, Nicholas Leventis

Chemistry Faculty Research & Creative Works

Background:Polyurea crosslinked silica aerogels are highly porous, lightweight, and mechanically strong materials with great potential for in vivo applications. Recent in vivo and in vitro studies have demonstrated the biocompatibility of this type of aerogel. the highly porous nature of aerogels allows for exceptional thermal, electric, and acoustic insulating capabilities that can be taken advantage of for non-invasive external imaging techniques. Sound-based detection of implants is a low cost, non-invasive, portable, and rapid technique that is routinely used and readily available in major clinics and hospitals.Methodology:In this study the first in vivo ultrasound response of polyurea crosslinked silica aerogel implants …

Intercalation And Delamination Of Layered Carbides And Carbonitrides, Olha Mashtalir, Michael Naguib, Vadym Mochalin, Yohan Dall'agnese, Min Heon, Michel W. Barsoum, Yury G. Gogotsi

Chemistry Faculty Research & Creative Works

Intercalation and delamination of two-dimensional solids in many cases is a requisite step for exploiting their unique properties. Herein we report on the intercalation of two-dimensional Ti₃C₂, Ti₃ CN and TiNbC - so called MXenes. Intercalation of hydrazine, and its co-intercalation with N,N-dimethylformamide, resulted in increases of the c-lattice parameters of surface functionalized f-Ti₃C₂, from 19.5 to 25.48 and 26.8 Å, respectively. Urea is also intercalated into f-Ti₃C₂. Molecular dynamics simulations suggest that a hydrazine monolayer intercalates between f-Ti₃C₂ layers. Hydrazine is also intercalated …

Luminescent Laf₃:Ce-Doped Organically Modified Nanoporous Silica Xerogels, Mingzhen Yao, Ryan Hall, Wei Chen, Dhairyashil Mohite, Nicholas Leventis, N. Lu, J. Wang, M. J. Kim, H. Luo, Hongbing Lu

Chemistry Faculty Research & Creative Works

Organically modified silica compounds (ORMOSILs) were synthesized by a sol-gel method from amine-functionalized 3-aminopropyl triethoxylsilane and tetramethylorthosilicate and were doped in situ with LaF₃:Ce nanoparticles, which in turn were prepared either in water or in ethanol. Doped ORMOSILs display strong photoluminescence either by UV or X-ray excitation and maintain good transparency up to a loading level of 15.66% w/w. The TEM observations demonstrate that ORMOSILs remain nanoporous with pore diameters in the 5-10 nm range. LaF₃:Ce nanoparticles doped into the ORMOSILs are rod-like, 5 nm in diameter and 10-15 nm in length. Compression testing indicates that …

Effects Of Heterogeneity In Small Π-Type Dimers: Homogeneous And Mixed Dimers Of Diacetylene And Cyanogen, Kari L. Copeland, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

The homo- and heterogeneous dimers of diacetylene (H-C≡C-C≡C-H) and cyanogen (N≡C-C≡N) were studied using ab initio electronic structure computations to probe the effects of heterogeneity on noncovalent interactions between systems with delocalized π electron networks. Full geometry optimizations and harmonic vibrational frequencies were performed using the robust coupled-cluster with single and double and perturbative triple excitations (CCSD(T)) method with the triple-ζ plus 2 sets of polarization functions TZ2P(f,d)++ basis set. Seven basic configurations were examined for each dimer (cross, stacked, parallel-slipped, parallel-tipped, linear, T-shaped and Y-shaped), but only four stationary points were identified on the potential energy surfaces (PESs) of …

Identification Of The Nad(P)H Binding Site Of Eukaryotic Udp-Galactopyranose Mutase, Richa Dhatwalia, Harkewal Singh, Luis M. Solano, Michelle Oppenheimer, Reeder M. Robinson, Jacob F. Ellerbrock, Pablo Sobrado, John J. Tanner

Chemistry Faculty Research & Creative Works

UDP-galactopyranose mutase (UGM) plays an essential role in galactofuranose biosynthesis in microorganisms by catalyzing the conversion of UDP-galactopyranose to UDP-galactofuranose. The enzyme has gained attention recently as a promising target for the design of new antifungal, antitrypanosomal, and antileishmanial agents. Here we report the first crystal structure of UGM complexed with its redox partner NAD(P)H. Kinetic protein crystallography was used to obtain structures of oxidized Aspergillus fumigatus UGM (AfUGM) complexed with NADPH and NADH, as well as reduced AfUGM after dissociation of NADP+. NAD(P)H binds with the nicotinamide near the FAD isoalloxazine and the ADP moiety extending toward the mobile …

Structural Insight Into The Mechanism Of Oxygen Activation And Substrate Selectivity Of Flavin-Dependent N-Hydroxylating Monooxygenases, Stefano Franceschini, Michael Fedkenheuer, Nancy J. Vogelaar, Howard H. Robinson, Pablo Sobrado, Andrea Mattevi

Chemistry Faculty Research & Creative Works

SidA from the human pathogen Aspergillus fumigatus catalyzes the generation of N5-hydroxyornithine in the biosynthesis of siderophores, a reaction essential for virulence. The crystal structures of SidA in complex with ornithine and lysine reveal the geometry of the interactions among flavin, NADP+, and the substrate amine group that underlie the hydroxylation reaction. The structural elucidation of the enzyme in complex with arginine provides insight into the role of electrostatics and hydrogen bonding in the mechanism of oxygen activation in this family of enzymes. © 2012 American Chemical Society.

Spectroscopy And Dynamics Of The Predissociated, Quasi-Linear S₂ State Of Chlorocarbene, Chong Tao, Craig A. Richmond, Calvin Mukarakate, Scott H. Kable, George B. Bacskay, Eric C. Brown, Richard Dawes, Phalgun Lolur, Scott A. Reid

Chemistry Faculty Research & Creative Works

In this work, we report on the spectroscopy and dynamics of the quasi-linear S₂ state of chlorocarbene, CHCl, and its deuterated isotopologue using optical-optical double resonance (OODR) spectroscopy through selected rovibronic levels of the S₁ state. This study, which represents the first observation of the S₂ state in CHCl, builds upon our recent examination of the corresponding state in CHF, where pronounced mode specificity was observed in the dynamics, with predissociation rates larger for levels containing bending excitation. In the present work, a total of 14 S₂ state vibrational levels with angular momentum 1 were observed …

Dynamical Reaction Pathways In Eley-Rideal Recombination Of Nitrogen From W(100), Ernesto Quintas-Sánchez, P. Larrégaray, C. Crespos, L. Martin-Gondre, J. Rubayo-Soneira, J. C. Rayez

Chemistry Faculty Research & Creative Works

The scattering of atomic nitrogen over a N-pre-adsorbed W(100) surface is theoretically described in the case of normal incidence off a single adsorbate. Dynamical reaction mechanisms, in particular Eley-Rideal (ER) abstraction, are scrutinized in the 0.1-3.0 eV collision energy range and the influence of temperature on reactivity is considered between 300 and 1500 K. Dynamics simulations suggest that, though non-activated reaction pathways exist, the abstraction process exhibits a significant collision energy threshold (0.5 eV). Such a feature, which has not been reported so far in the literature, is the consequence of a repulsive interaction between the impinging and the pre-adsorbed …

Crystal Structures Of Trypanosoma Cruzi Udp-Galactopyranose Mutase Implicate Flexibility Of The Histidine Loop In Enzyme Activation, Richa Dhatwalia, Harkewal Singh, Michelle Oppenheimer, Pablo Sobrado, John J. Tanner

Chemistry Faculty Research & Creative Works

Chagas disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. Here we report crystal structures of the galactofuranose biosynthetic enzyme UDP-galactopyranose mutase (UGM) from T. cruzi, which are the first structures of this enzyme from a protozoan parasite. UGM is an attractive target for drug design because galactofuranose is absent in humans but is an essential component of key glycoproteins and glycolipids in trypanosomatids. Analysis of the enzyme-UDP noncovalent interactions and sequence alignments suggests that substrate recognition is exquisitely conserved among eukaryotic UGMs and distinct from that of bacterial UGMs. This observation has implications for inhibitor …

A Fluorescence Polarization Binding Assay To Identify Inhibitors Of Flavin-Dependent Monooxygenases, Jun Qi, Karina Kizjakina, Reeder Robinson, Karishma Tolani, Pablo Sobrado

Chemistry Faculty Research & Creative Works

N-Hydroxylating monooxygenases (NMOs) are essential for pathogenesis in fungi and bacteria. NMOs catalyze the hydroxylation of sine and ornithine in the biosynthesis of hydroxamate-containing siderophores. Inhibition of kynurenine monooxygenase (KMO), which catalyzes the conversion of kynurenine to 3-hydroxykynurenine, alleviates neurodegenerative disorders such as Huntington's and Alzheimer's diseases and brain infections caused by the parasite Trypanosoma brucei. These enzymes are examples of flavin-dependent monooxygenases, which are validated drug targets. Here, we describe the development and optimization of a fluorescence polarization assay to identify potential inhibitors of flavin-dependent monooxygenases. Fluorescently labeled ADP molecules were synthesized and tested. An ADP-TAMRA chromophore bound to …

Templated Synthesis Of Nylon Nucleic Acids And Characterization By Nuclease Digestion, Yu Liu, Risheng Wang, Liang Ding, Roujie Sha, Nadrian C. Seeman, James W. Canary

Chemistry Faculty Research & Creative Works

Nylon nucleic acids containing oligouridine nucleotides with pendent polyamide linkers and flanked by unmodified heteronucleotide sequences were prepared by DNA templated synthesis. Templation was more efficient than the single-stranded synthesis; coupling step yields were as high as 99.2%, with up to 7 amide linkages formed in the synthesis of a molecule containing 8 modified nucleotides. Controlled digestion by calf spleen phosphodiesterase enabled the mapping of modified nucleotides in the sequences. a combination of complete degradation of nylon nucleic acids by snake venom phosphodiesterase and dephosphorylation of the resulting nucleotide fragments by bacterial alkaline phosphatase, followed by LCMS analysis, clarified the …

Hydrocarbon/Water Interactions: Encouraging Energetics And Structures From Dft But Disconcerting Discrepancies For Hessian Indices, Kari L. Copeland, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

In this work, ab initio electronic structure computations have been used to systematically examine the structures and energetics of nine small hydrocarbon molecules interacting with water. Full geometry optimizations and harmonic vibrational frequency calculations were performed on 30 unique dimer configurations with the MP2 method and a triple-ζ correlation consistent basis set (cc-pVTZ for H and aug-cc-pVTZ for C and O, denoted haTZ). Three different estimates of the CCSD(T) complete basis set (CBS) limit interaction energies were determined for all 30 MP2 optimized hydrocarbon/water structures, and they never deviate from their mean by more than 0.07 kcal mol -1. MP2 …

Chemical Mechanism Of Udp-Galactopyranose Mutase From Trypanosoma Cruzi: A Potential Drug Target Against Chagas' Disease, Michelle Oppenheimer, Ana Lisa Valenciano, Karina Kizjakina, Jun Qi, Pablo Sobrado

Chemistry Faculty Research & Creative Works

UDP-galactopyranose mutase (UGM) is a flavoenzyme that catalyzes the conversion of UDP-galactopyranose to UDP-galactofuranose, the precursor of galactofuranose (Galf). Galf is found in several pathogenic organisms, including the parasite Trypanosoma cruzi, the causative agent of Chagas' disease. Galf) is important for virulence and is not present in humans, making its biosynthetic pathway an attractive target for the development of new drugs against T. cruzi. Although UGMs catalyze a non-redox reaction, the flavin must be in the reduced state for activity and the exact role of the flavin in this reaction is controversial. The kinetic and chemical mechanism of TcUGM was …

Crystal Structures And Small-Angle X-Ray Scattering Analysis Of Udp-Galactopyranose Mutase From The Pathogenic Fungus Aspergillus Fumigatus, Richa Dhatwalia, Harkewal Singh, Michelle Oppenheimer, Dale B. Karr, Jay C. Nix, Pablo Sobrado, John J. Tanner

Chemistry Faculty Research & Creative Works

UDP-galactopyranose mutase (UGM) is a flavoenzyme that catalyzes the conversion of UDP-galactopyranose to UDP-galactofuranose, which is a central reaction in galactofuranose biosynthesis. Galactofuranose has never been found in humans but is an essential building block of the cell wall and extracellular matrix of many bacteria, fungi, and protozoa. The importance of UGM for the viability of many pathogens and its absence in humans make UGMa potential drug target. Here we report the first crystal structures and small-angle x-ray scattering data for UGM from the fungus Aspergillus fumigatus, the causative agent of aspergillosis. The structures reveal that Aspergillus UGM has several …

Basis Set Dependence Of Higher-Order Correlation Effects In Π-Type Interactions, Emily J. Carrell, Cara M. Thorne, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

The basis set dependence of higher-order correlation effects on -type interaction energies was examined by scanning the potential energy surfaces of five dimer systems. The dimers of acetylene (H-CC-H), diacetylene (H-CC-CC-H), cyanogen (NC-CN), diphosphorous (PP), and 1,4-diphosphabutadiyne (PC-CP) were studied in three different configurations: cross, parallel-displaced, and t-shaped. More than 800 potential energy curves (PECs) were generated by computing the interaction energies for all 15 dimer configurations over a range of intermolecular distances with the MP2, coupled-cluster single double (CCSD), and coupled-cluster single double triple (CCSD(T)) methods in conjunction with 21 basis sets ranging from a small 6-31G*(0.25) split-valence basis …

Neutron Repulsion, Oliver Manuel

Chemistry Faculty Research & Creative Works

Earth is connected gravitationally, magnetically and electrically to its heat source and the source of its chemical elements - a neutron star obscured from view by waste products in the photosphere. Neutron repulsion makes the solar core like the hot filament in an incandescent light bulb. Excited neutrons are emitted from the pulsar, decay to hydrogen, and partially fuse into the helium now trapped with it in the photosphere, like a frosted light bulb. Neutron repulsion is the overlooked source of energy, the keystone of an arch that locks together many earlier, puzzling observations: 1.) Excess ¹³⁶Xe accompanied primordial …