Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Earth Sciences (58714)
- Computer Sciences (57932)
- Environmental Sciences (52361)
- Engineering (40197)
- Life Sciences (39773)
-
- Physics (36526)
- Chemistry (34519)
- Geology (29715)
- Mathematics (27378)
- Social and Behavioral Sciences (24564)
- Oceanography and Atmospheric Sciences and Meteorology (16422)
- Statistics and Probability (13246)
- Education (12805)
- Computer Engineering (12790)
- Soil Science (11977)
- Medicine and Health Sciences (11785)
- Plant Sciences (11182)
- Natural Resources and Conservation (10266)
- Arts and Humanities (9726)
- Astrophysics and Astronomy (9206)
- Electrical and Computer Engineering (8897)
- Sustainability (8674)
- Natural Resources Management and Policy (8567)
- Artificial Intelligence and Robotics (8494)
- Water Resource Management (8291)
- Applied Mathematics (7991)
- Environmental Health and Protection (6879)
- Science and Mathematics Education (6757)
- Databases and Information Systems (6720)
- Institution
-
- University of Nebraska - Lincoln (24230)
- Western Michigan University (19508)
- Selected Works (16838)
- University of Kentucky (12002)
- TÜBİTAK (10317)
-
- Singapore Management University (7453)
- Utah State University (7340)
- Missouri University of Science and Technology (6056)
- Old Dominion University (5953)
- University of Wollongong (4868)
- William & Mary (4602)
- University of South Florida (3859)
- Wright State University (3840)
- Portland State University (3798)
- University of Nevada, Las Vegas (3640)
- Louisiana State University (3417)
- China Simulation Federation (3363)
- City University of New York (CUNY) (3219)
- Brigham Young University (2906)
- Purdue University (2813)
- Air Force Institute of Technology (2678)
- Claremont Colleges (2640)
- California Polytechnic State University, San Luis Obispo (2568)
- Western Washington University (2456)
- University of Arkansas, Fayetteville (2433)
- University of Texas Rio Grande Valley (2419)
- Department of Primary Industries and Regional Development, Western Australia (2354)
- University of Texas at El Paso (2316)
- Chinese Chemical Society | Xiamen University (2294)
- Chulalongkorn University (2268)
- Keyword
-
- Machine learning (1689)
- Climate change (1680)
- Western Australia (1581)
- Mathematics (1369)
- Chemistry (1157)
-
- Sustainability (1141)
- Physics (1068)
- Water quality (983)
- Deep learning (891)
- Geology (858)
- Groundwater (851)
- Machine Learning (828)
- Simulation (824)
- Research and Technical Reports (797)
- Water (780)
- United States (757)
- Education (756)
- Management (745)
- Nebraska (744)
- Agriculture (718)
- Artificial intelligence (707)
- Climate (702)
- GIS (698)
- Statistics (685)
- Security (681)
- Grains and field crops (674)
- Environment (672)
- Computer Science (667)
- Ecology (657)
- Optimization (656)
- Publication Year
-
- 2024 (7853)
- 2023 (12579)
- 2022 (18300)
- 2021 (27876)
- 2020 (15207)
-
- 2019 (15927)
- 2018 (13646)
- 2017 (12521)
- 2016 (12690)
- 2015 (12617)
- 2014 (12299)
- 2013 (11462)
- 2012 (12196)
- 2011 (10325)
- 2010 (8621)
- 2009 (7616)
- 2008 (7321)
- 2007 (6758)
- 2006 (5872)
- 2005 (5573)
- 2004 (4447)
- 2003 (3876)
- 2002 (3435)
- 2001 (3030)
- 2000 (2919)
- 1999 (2555)
- 1998 (2574)
- 1997 (2472)
- 1996 (2437)
- 1995 (2193)
- Publication
-
- Legacy Scout Tickets from Pure Oil Company (11044)
- Theses and Dissertations (8341)
- IGC Proceedings (1993-2023) (7001)
- Research Collection School Of Computing and Information Systems (6891)
- Thin Sections (5745)
-
- Electronic Theses and Dissertations (4194)
- Faculty Publications (3783)
- Journal of System Simulation (3363)
- Nebraska Tractor Tests (3348)
- Turkish Journal of Electrical Engineering and Computer Sciences (3020)
- Masters Theses (2634)
- Turkish Journal of Chemistry (2628)
- Turkish Journal of Mathematics (2494)
- Journal of Electrochemistry (2294)
- Honors Theses (2158)
- Faculty of Informatics - Papers (Archive) (2013)
- Physics Faculty Publications (1942)
- Bulletin of the Mineral Research and Exploration (1893)
- Doctoral Dissertations (1882)
- Dissertations, Theses, and Masters Projects (1876)
- Reports (1835)
- Dissertations (1816)
- Physics Faculty Research & Creative Works (1762)
- Department of Computer Science Technical Reports (1721)
- USF Tampa Graduate Theses and Dissertations (1607)
- School of Natural Resources: Faculty Publications (1586)
- United States Department of Agriculture Wildlife Services: Staff Publications (1529)
- Australian Institute for Innovative Materials - Papers (1524)
- Electronic Thesis and Dissertation Repository (1476)
- All Graduate Theses and Dissertations, Spring 1920 to Summer 2023 (1427)
- Publication Type
Articles 143851 - 143880 of 302516
Full-Text Articles in Physical Sciences and Mathematics
Addressing The Achievement Gap: Engaging Students In The Chemistry Classroom, Haidy Kamel Dr.
Addressing The Achievement Gap: Engaging Students In The Chemistry Classroom, Haidy Kamel Dr.
Cleveland State University Regional Chemistry Teaching Symposium: March 12 & 13, 2015
No abstract provided.
Magical Science: Chemistry Magic Tricks Just For Fun! (Workshop), Regan L. Silvestri
Magical Science: Chemistry Magic Tricks Just For Fun! (Workshop), Regan L. Silvestri
Cleveland State University Regional Chemistry Teaching Symposium: March 12 & 13, 2015
Chemistry magic tricks are simply chemistry demonstrations cleverly performed, and are highly valuable for engaging and motivating students in the study of chemistry. Our agenda has been to adapt common chemistry demonstrations into presentations with clever twists, essentially turning them into magic tricks. This workshop will show how a science demonstration can be turned into a science magic trick simply by adapting the presentation. Science magic tricks provide a unique forum not only for expanding scientific knowledge, but moreover scientific interest. Our hope is that students will be engaged and motivated in the future study of chemistry.
Simple Mathematical Models Do Not Accurately Predict Early Siv Dynamics, Cecilia Noecker, Krista Schaefer, Kelly Zaccheo, Yiding Yang, Judy Day, Vitaly V. Ganusov
Simple Mathematical Models Do Not Accurately Predict Early Siv Dynamics, Cecilia Noecker, Krista Schaefer, Kelly Zaccheo, Yiding Yang, Judy Day, Vitaly V. Ganusov
Faculty Publications and Other Works -- Mathematics
Upon infection of a new host, human immunodeficiency virus (HIV) replicates in the mucosal tissues and is generally undetectable in circulation for 1–2 weeks post-infection. Several interventions against HIV including vaccines and antiretroviral prophylaxis target virus replication at this earliest stage of infection. Mathematical models have been used to understand how HIV spreads from mucosal tissues systemically and what impact vaccination and/or antiretroviral prophylaxis has on viral eradication. Because predictions of such models have been rarely compared to experimental data, it remains unclear which processes included in these models are critical for predicting early HIV dynamics. Here we modified the …
On Pi Day, A Serving Of Why We Need Math, Darren B. Glass
On Pi Day, A Serving Of Why We Need Math, Darren B. Glass
Math Faculty Publications
Today, our Facebook feeds will be peppered with references to Pi Day, a day of celebration that has long been acknowledged by math fans and that Congress recognized in 2009. Every high schooler learns that pi is the ratio of the circumference of a circle to its diameter and that its decimal expansion begins 3.14 and goes on infinitely without repeating. [excerpt]
Mathematical Analysis Of Uniform Polyhedra Having 2 Congruent Regular N-Gonal Faces, 2n Congruent Trapezoidal Faces, 5n Edges & 3n Vertices Lying On A Spherical Surface (Generalized Formula By H.C. Rajpoot), Harish Chandra Rajpoot Rajpoot Hcr
Mathematical Analysis Of Uniform Polyhedra Having 2 Congruent Regular N-Gonal Faces, 2n Congruent Trapezoidal Faces, 5n Edges & 3n Vertices Lying On A Spherical Surface (Generalized Formula By H.C. Rajpoot), Harish Chandra Rajpoot Rajpoot Hcr
Harish Chandra Rajpoot H.C. Rajpoot
All the formula have been generalized by the author which are applicable to calculate the important parameters, of any uniform polyhedron having 2 congruent regular n-gonal faces, 2n congruent trapezoidal faces each with three equal sides, 5n edges & 3n vertices lying on a spherical surface, such as solid angle subtended by each face at the centre, normal distance of each face from the centre, inner radius, outer radius, mean radius, surface area & volume. These are useful for analysis, designing & modeling of different uniform polyhedra.
Identification Of A Histidine Metal Ligand In The Arge-Encoded N-Acetyl-L-Ornithine Deacetylase From Escherichia Coli, Wade C. Mcgregor, Danuta Gillner, Sabina I. Swierczek, Dali Liu, Richard C. Holz
Identification Of A Histidine Metal Ligand In The Arge-Encoded N-Acetyl-L-Ornithine Deacetylase From Escherichia Coli, Wade C. Mcgregor, Danuta Gillner, Sabina I. Swierczek, Dali Liu, Richard C. Holz
Richard C. Holz
The H355A, H355K, H80A, and H80K mutant enzymes of the argE-encoded N-acetyl-L-ornithine deacetylase (ArgE) from Escherichia coli were prepared, however, only the H355A enzyme was found to be soluble. Kinetic analysis of the Co(II)-loaded H355A exhibited activity levels that were 380-fold less than Co(II)-loaded WT ArgE. Electronic absorption spectra of Co(II)-loaded H355A-ArgE indicate that the bound Co(II) ion resides in a distorted, five-coordinate environment and Isothermal Titration Calorimetry (ITC) data for Zn(II) binding to the H355A enzyme provided a dissociation constant (Kd) of 39 μM. A three-dimensional homology model of ArgE was generated using the X-ray crystal structure of the …
The High-Resolution Structures Of The Neutral And The Low Ph Crystals Of Aminopeptidase From Aeromonas Proteolytica, William Desmarais, David Bienvenue, Krzysztof Bzymek, Gregory Petsko, Dagmar Ringe, Richard Holz
The High-Resolution Structures Of The Neutral And The Low Ph Crystals Of Aminopeptidase From Aeromonas Proteolytica, William Desmarais, David Bienvenue, Krzysztof Bzymek, Gregory Petsko, Dagmar Ringe, Richard Holz
Richard C. Holz
The aminopeptidase from Aeromonas proteolytica (AAP) contains two zinc ions in the active site and catalyzes the degradation of peptides. Herein we report the crystal structures of AAP at 0.95-Å resolution at neutral pH and at 1.24-Å resolution at low pH. The combination of these structures allowed the precise modeling of atomic positions, the identification of the metal bridging oxygen species, and insight into the physical properties of the metal ions. On the basis of these structures, a new putative catalytic mechanism is proposed for AAP that is likely relevant to all binuclear metalloproteases.
Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica: Characterization Of Substrate Binding, Brian Bennett, Richard Holz
Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica: Characterization Of Substrate Binding, Brian Bennett, Richard Holz
Richard C. Holz
The Co(II)Zn(II)- and Zn(II)Co(II)-substituted derivatives of the aminopeptidase from Aeromonas proteolytica (AAP) were probed by EPR spectroscopy. EPR spectra of the high-spin S = 3/2 Co(II) ions in [CoZn(AAP)] and [ZnCo(AAP)] indicated that each metal binding site provides a spectroscopically distinct signature. For [CoZn(AAP)], subtraction of EPR spectra recorded at pH 7.5 and 10 revealed that two species were present and that the relative contributions to each of the experimental spectra were pH-dependent. The first EPR species, predominant at lower pH values, was simulated as a relatively featureless axial signal with geff values of 2.20, 3.92, and …
Acrylamide Production Using Encapsulated Nitrile Hydratase From Pseudonocardia Thermophila In A Sol–Gel Matrix, Salette Martinez, Misty Kuhn, James Russell, Richard Holz, Timothy Elgren
Acrylamide Production Using Encapsulated Nitrile Hydratase From Pseudonocardia Thermophila In A Sol–Gel Matrix, Salette Martinez, Misty Kuhn, James Russell, Richard Holz, Timothy Elgren
Richard C. Holz
The cobalt-type nitrile hydratase from Pseudonocardia thermophila JCM 3095 (PtNHase) was successfully encapsulated in tetramethyl orthosilicate sol–gel matrices to produce a PtNHase:sol–gel biomaterial. The PtNHase:sol–gel biomaterial catalyzed the conversion of 600 mM acrylonitrile to acrylamide in 60 min at 35 °C with a yields of >90%. Treatment of the biomaterial with proteases confirmed that the catalytic activity is due to the encapsulated enzyme and not surface bound NHase. The biomaterial retained 50% of its activity after being used for a total of 13 consecutive reactions for the conversion of acrylonitrile to acrylamide. The thermostability and long-term storage of the PtNHase:sol–gel …
The Active Site Sulfenic Acid Ligand In Nitrile Hydratases Can Function As A Nucleophile, Salette Martinez, Rui Wu, Ruslan Sanishvili, Dali Liu, Richard C. Holz
The Active Site Sulfenic Acid Ligand In Nitrile Hydratases Can Function As A Nucleophile, Salette Martinez, Rui Wu, Ruslan Sanishvili, Dali Liu, Richard C. Holz
Richard C. Holz
Nitrile hydratase (NHase) catalyzes the hydration of nitriles to their corresponding commercially valuable amides at ambient temperatures and physiological pH. Several reaction mechanisms have been proposed for NHase enzymes; however, the source of the nucleophile remains a mystery. Boronic acids have been shown to be potent inhibitors of numerous hydrolytic enzymes due to the open shell of boron, which allows it to expand from a trigonal planar (sp2) form to a tetrahedral form (sp3). Therefore, we examined the inhibition of the Co-type NHase from Pseudonocardia thermophila JCM 3095 (PtNHase) by boronic acids via kinetics and X-ray crystallography. Both 1-butaneboronic acid …
A New Colorimetric Assay For Methionyl Aminopeptidases: Examination Of The Binding Of A New Class Of Pseudopeptide Analog Inhibitors, Sanghamitra Mitra, Anna Dygas-Holz, Jiri Jiracek, Miroslava Zertova, Lenka Zakova, Richard Holz
A New Colorimetric Assay For Methionyl Aminopeptidases: Examination Of The Binding Of A New Class Of Pseudopeptide Analog Inhibitors, Sanghamitra Mitra, Anna Dygas-Holz, Jiri Jiracek, Miroslava Zertova, Lenka Zakova, Richard Holz
Richard C. Holz
A direct and convenient spectrophotometric assay has been developed for methionine aminopeptidases (MetAPs). The method employs the hydrolysis of a substrate that is a methionyl analogue of p-nitroaniline (l-Met-p-NA), which releases the chromogenic product p-nitroaniline. This chromogenic product can be monitored continuously using a UV–Vis spectrophotometer set at 405 nm. The assay was tested with the type I MetAP from Escherichia coli (EcMetAP-I) and the type II MetAP from Pyrococcus furiosus (PfMetAP-II). Using l-Met-p-NA, the kinetic constants kcat and Km were determined for EcMetAP-I and PfMetAP-II …
Mechanistic Studies On The Aminopeptidase From Aeromonas Proteolytica: A Two-Metal Ion Mechanism For Peptide Hydrolysis, Guanjing Chen, Tanya Edwards, Ventris D'Souza, Richard Holz
Mechanistic Studies On The Aminopeptidase From Aeromonas Proteolytica: A Two-Metal Ion Mechanism For Peptide Hydrolysis, Guanjing Chen, Tanya Edwards, Ventris D'Souza, Richard Holz
Richard C. Holz
The aminopeptidase from Aeromonas proteolytica (AAP) is uncompetitively inhibited by fluoride ion at pH 8.0 with an inhibition constant (Ki) of 30 mM. Thus, fluoride inactivates AAP only after substrate binding, and only a single fluoride ion binds to AAP. On the other hand, chloride ion does not inhibit AAP up to concentrations of 2 M at pH 8.0. The pH dependence of fluoride inhibition of AAP was measured over the pH range 6.0−9.5. Between pH values of 6.0 and 9.0, fluoride ion acts as a pure uncompetitive inhibitor of AAP, and the Ki increases from …
Analyzing The Catalytic Role Of Asp97 In The Methionine Aminopeptidase From Escherichia Coli, Sanghamitra Mitra, Kathleen M. Job, Lu Meng, Brian Bennett, Richard C. Holz
Analyzing The Catalytic Role Of Asp97 In The Methionine Aminopeptidase From Escherichia Coli, Sanghamitra Mitra, Kathleen M. Job, Lu Meng, Brian Bennett, Richard C. Holz
Richard C. Holz
An active site aspartate residue, Asp97, in the methionine aminopeptidase (MetAPs) from Escherichia coli (EcMetAP-I) was mutated to alanine, glutamate, and asparagine. Asp97 is the lone carboxylate residue bound to the crystallographically determined second metal-binding site in EcMetAP-I. These mutant EcMetAP-I enzymes have been kinetically and spectroscopically characterized. Inductively coupled plasma–atomic emission spectroscopy analysis revealed that 1.0 ± 0.1 equivalents of cobalt were associated with each of the Asp97-mutated EcMetAP-Is. The effect on activity after altering Asp97 to alanine, glutamate or asparagine is, in general, due to a ∼ 9000-fold decrease in kca towards Met-Gly-Met-Met as compared to the wild-type …
Spectroscopic Characterization Of The Europium(Iii) Complexes Of A Series Of N,N'-Bis(Carboxymethyl) Macrocyclic Ether Bis(Lactones), Richard Holz, C. Chang, William Horrocks
Spectroscopic Characterization Of The Europium(Iii) Complexes Of A Series Of N,N'-Bis(Carboxymethyl) Macrocyclic Ether Bis(Lactones), Richard Holz, C. Chang, William Horrocks
Richard C. Holz
The Eu3+ and Y3+ complexes of a series of N,N'-bis(carboxymethyl) macrocyclic ether bis(lactone) ligands derived from ethyl-enediaminetetraacetic acid (EDTA) were characterized in solution by using Eu3+ laser-induced luminescence and 1H and 13CNMR spectroscopy. The complexation of EDTA was also studied for comparison purposes. These ligands form 1:1 complexes with Eu3+ at the concentrations studied (10 µM), with the luminescence lifetimes in H2O and D2O providing the number of coordinated water molecules. The 7F0 -> 5D0 excitation spectra indicate that for each of …
Epr And X-Ray Crystallographic Characterization Of The Product-Bound Form Of The MnIi-Loaded Methionyl Aminopeptidase From Pyrococcus Furiosus, Alicja Copik, Boguslaw Nocek, Sabina Swierczek, Shane Ruebush, Se Jang, Lu Meng, Ventris D'Souza, John Peters, Brian Bennett, Richard Holz
Epr And X-Ray Crystallographic Characterization Of The Product-Bound Form Of The MnIi-Loaded Methionyl Aminopeptidase From Pyrococcus Furiosus, Alicja Copik, Boguslaw Nocek, Sabina Swierczek, Shane Ruebush, Se Jang, Lu Meng, Ventris D'Souza, John Peters, Brian Bennett, Richard Holz
Richard C. Holz
Methionine aminopeptidases (MetAPs) are ubiquitous metallohydrolases that remove the N-terminal methionine from nascent polypeptide chains. Although various crystal structures of MetAP in the presence of inhibitors have been solved, the structural aspects of the product-bound step has received little attention. Both perpendicular- and parallel-mode electron paramagnetic resonance (EPR) spectra were recorded for the MnII-loaded forms of the type-I (Escherichia coli) and type-II (Pyrococcus furiosus) MetAPs in the presence of the reaction product l-methionine (l-Met). In general, similar EPR features were observed for both [MnMn(EcMetAP-I)]−l-Met and [MnMn(PfMetAP-II)]−l-Met. The observed perpendicular-mode EPR spectra consisted of a six-line hyperfine pattern at g = …
One- And Two-Dimensional Proton Nmr Studies Of The Active Site Of Iron(Ii) Superoxide Dismutase From Escherichia Coli, Li-June Ming, John Lynch, Richard Holz, Lawrence Que
One- And Two-Dimensional Proton Nmr Studies Of The Active Site Of Iron(Ii) Superoxide Dismutase From Escherichia Coli, Li-June Ming, John Lynch, Richard Holz, Lawrence Que
Richard C. Holz
The iron(II) superoxide dismutase (FeSOD) from Escherichia coli exhibits relatively sharp well-resolved paramagnetically shifted NMR signals. These signals can be associated with the endogenous ligands characterized by X-ray crystallography for the oxidized form FeIlISOD. Our results demonstrate that the active site remains intact upon reduction of the Fe(III) site, retaining the same coordination modes for the three N,-coordinated His residues (presumably His-26, His-75, and His-162) and the Asp residue (presumably Asp-158). The N-H resonances of the coordinated histidines are found at 88, 43, and 37 ppm, while the signals at 24.5 (E), 19 (G), and 15 (J) ppm …
Kinetic, Spectroscopic, And X-Ray Crystallographic Characterization Of The Functional E151h Aminopeptidase From Aeromonas Proteolytica, Krzysztof Bzymek, Aaron Moulin, Sabina Swierczek, Dagmar Ringe, Gregory Petsko, Brian Bennett, Richard Holz
Kinetic, Spectroscopic, And X-Ray Crystallographic Characterization Of The Functional E151h Aminopeptidase From Aeromonas Proteolytica, Krzysztof Bzymek, Aaron Moulin, Sabina Swierczek, Dagmar Ringe, Gregory Petsko, Brian Bennett, Richard Holz
Richard C. Holz
Glutamate151 (E151) has been shown to be catalytically essential for the aminopeptidase from Vibrio proteolyticus (AAP). E151 acts as the general acid/base during the catalytic mechanism of peptide hydrolysis. However, a glutamate residue is not the only residue capable of functioning as a general acid/base during catalysis for dinuclear metallohydrolases. Recent crystallographic characterization of the d-aminopeptidase from Bacillus subtilis (DppA) revealed a histidine residue that resides in an identical position to E151 in AAP. Because the active-site ligands for DppA and AAP are identical, AAP has been used as a model enzyme to understand the mechanistic role of H115 in …
Electrochemical Properties Of The Diiron Core Of Uteroferrin And Its Anion Complexes, Dan Wang, Richard Holz, Sheila David, Lawrence Que, Marian Stankovich
Electrochemical Properties Of The Diiron Core Of Uteroferrin And Its Anion Complexes, Dan Wang, Richard Holz, Sheila David, Lawrence Que, Marian Stankovich
Richard C. Holz
The reduction potentials (Em) of the purple acid phosphatase from porcine uterus, uteroferrin (Uf), and its phosphate, arsenate, and molybdate complexes were determined by coulometric methods at various pH values. The midpoint potential of Uf at the pH value for optimal enzyme activity (pH 5) was found to be +367 mV versus a normal hydrogen electrode (NHE), while at pH 6.01 Uf exhibits a reduction potential of +306 mV. At pH 6.01 molybdate was found to shift the potential of Uf more positive by 192 mV, while phosphate and arsenate shift the potential of Uf more negative by 193 and …
Spectroscopic And Thermodynamic Characterization Of The E151d And E151a Altered Leucine Aminopeptidases From Aeromonas Proteolytica, Krzysztof Bzymek, Sabina Swierczek, Brian Bennett, Richard Holz
Spectroscopic And Thermodynamic Characterization Of The E151d And E151a Altered Leucine Aminopeptidases From Aeromonas Proteolytica, Krzysztof Bzymek, Sabina Swierczek, Brian Bennett, Richard Holz
Richard C. Holz
Previous kinetic characterization of the glutamate 151 (E151)-substituted forms of the leucine aminopeptidase from Aeromonas proteolytica (Vibrio proteolyticus; AAP) has provided critical evidence that this residue functions as the general acid/base. The close proximity of similar glutamate residues to the bridging water/hydroxide of the dinuclear active sites of metalloenzymes (2.80 and 3.94 Å in carboxypeptidase G2 and 3.30 and 3.63 Å in AAP), suggests it may also be involved in stabilizing the active-site metal ions. Therefore, the structural perturbations of the dinuclear active site of AAP were examined for two E151-substituted forms, namely E151D-AAP and E151A-AAP, by …
Substrate Specificity, Metal Binding Properties, And Spectroscopic Characterization Of The Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase From Haemophilus Influenzae, David Bienvenue, Danuta Gilner, Ryan Davis, Brian Bennett, Richard Holz
Substrate Specificity, Metal Binding Properties, And Spectroscopic Characterization Of The Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase From Haemophilus Influenzae, David Bienvenue, Danuta Gilner, Ryan Davis, Brian Bennett, Richard Holz
Richard C. Holz
The catalytic and structural properties of divalent metal ion cofactor binding sites in the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae were investigated. Co(II)-substituted DapE enzyme was 25% more active than the Zn(II)-loaded form of the enzyme. Interestingly, Mn(II) can activate DapE, but only to ∼20% of the Zn(II)-loaded enzyme. The order of the observed kcat values are Co(II) > Zn(II) > Cd(II) > Mn(II) >Ni(II) ∼ Cu(II) ∼ Mg(II). DapE was shown to only hydrolyze l,l-N-succinyl-diaminopimelic acid (l,l-SDAP) and was inactive toward d,l-, l,d-, and d,d-SDAP. DapE was also inactive toward several acetylated amino acids as …
Mono-N-Acyl-2,6-Diaminopimelic Acid Derivatives: Analysis By Electromigration And Spectroscopic Methods And Examination Of Enzyme Inhibitory Activity, Jan Hlaváček, Miloslava Vítovcová, Petra Sázelová, Jan Pícha, Václav Vaněk, Miloš Buděšínský, Jiří Jiráček, Danuta Gillner, Richard Holz, Ivan Mikšík, Václav Kašička
Mono-N-Acyl-2,6-Diaminopimelic Acid Derivatives: Analysis By Electromigration And Spectroscopic Methods And Examination Of Enzyme Inhibitory Activity, Jan Hlaváček, Miloslava Vítovcová, Petra Sázelová, Jan Pícha, Václav Vaněk, Miloš Buděšínský, Jiří Jiráček, Danuta Gillner, Richard Holz, Ivan Mikšík, Václav Kašička
Richard C. Holz
Thirteen mono-N-acyl derivatives of 2,6-diaminopimelic acid (DAP)—new potential inhibitors of the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE; EC 3.5.1.18)—were analyzed and characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies and two capillary electromigration methods: capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC). Structural features of DAP derivatives were characterized by IR and NMR spectroscopies, whereas CZE and MEKC were applied to evaluate their purity and to investigate their electromigration properties. Effective electrophoretic mobilities of these compounds were determined by CZE in acidic and alkaline background electrolytes (BGEs) and by MEKC in acidic and alkaline BGEs containing a pseudostationary …
Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By Aliphatic Alcohols. Characterization Of The Hydrophobic Substrate Recognition Site, Leila Ustynyuk, Brian Bennett, Tanya Edwards, Richard Holz
Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By Aliphatic Alcohols. Characterization Of The Hydrophobic Substrate Recognition Site, Leila Ustynyuk, Brian Bennett, Tanya Edwards, Richard Holz
Richard C. Holz
Seven aliphatic and two aromatic alcohols were tested as reporters of the substrate selectivity of the aminopeptidase from Aeromonas proteolytica (AAP). This series of alcohols was chosen to systematically probe the effect of carbon chain length, steric bulk, and inhibitor shape on the inhibition of AAP. Initially, however, the question of whether AAP is denatured in the presence of aliphatic alcohols was addressed. On the basis of circular dichroism (CD), electronic absorption, and fluorescence spectra, the secondary structure of AAP, with and without added aliphatic alcohols, was unchanged. These data clearly indicate that AAP is not denatured in aliphatic alcohols, …
Kinetic And Spectroscopic Characterization Of The H178a Methionyl Aminopeptidase From Escherichia Coli, Alicja Copik, Sabina Swierczek, W. Lowther, Ventris D'Souza, Brian Matthews, Richard Holz
Kinetic And Spectroscopic Characterization Of The H178a Methionyl Aminopeptidase From Escherichia Coli, Alicja Copik, Sabina Swierczek, W. Lowther, Ventris D'Souza, Brian Matthews, Richard Holz
Richard C. Holz
To gain insight into the role of the strictly conserved histidine residue, H178, in the reaction mechanism of the methionyl aminopeptidase from Escherichia coli (EcMetAP-I), the H178A mutant enzyme was prepared. Metal-reconstituted H178A binds only one equivalent of Co(II) or Fe(II) tightly with affinities that are identical to the WT enzyme based on kinetic and isothermal titration calorimetry (ITC) data. Electronic absorption spectra of Co(II)-loaded H178A EcMetAP-I indicate that the active site divalent metal ion is pentacoordinate, identical to the WT enzyme. These data indicate that the metal binding site has not been affected by altering H178. …
Slow-Binding Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By Peptide Thiols: Synthesis And Spectroscopic Characterization, Kristi Huntington, David Bienvenue, Yaoming Wei, Brian Bennett, Richard Holz, Dehua Pei
Slow-Binding Inhibition Of The Aminopeptidase From Aeromonas Proteolytica By Peptide Thiols: Synthesis And Spectroscopic Characterization, Kristi Huntington, David Bienvenue, Yaoming Wei, Brian Bennett, Richard Holz, Dehua Pei
Richard C. Holz
Peptide-derived thiols of the general structure N-mercaptoacyl-leucyl-p-nitroanilide (1a−c) were synthesized and found to be potent, slow-binding inhibitors of the aminopeptidase from Aeromonas proteolytica (AAP). The overall potencies (KI*) of these inhibitors against AAP range from 2.5 to 57 nM exceeding that of the natural product bestatin and approaching that of amastatin. The corresponding alcohols (2a−b) are simple competitive inhibitors of much lower potencies (KI = 23 and 360 μM). These data suggest that the free thiols are involved in the formation of the E·I and E·I* complexes, presumably serving as a metal ligand. To investigate the nature of the interaction …
The Aminopeptidase From Aeromonas Proteolytica: Structure And Mechanism Of Co-Catalytic Metal Centers Involved In Peptide Hydrolysis, Richard Holz
Richard C. Holz
Enzymes containing multi-metal active sites are central to numerous biological processes and, consequently, characterization of their structure and function is a problem of outstanding importance. One of the least-explored groups of enzymes is the hydrolases that contain dinuclear metal centers. These enzymes play key roles in carcinogenesis, tissue repair, and protein degradation processes. In addition, some of these enzymes can catalyze the hydrolysis of phosphorus(V) compounds found in nerve gases and agricultural neurotoxins. The determination of detailed reaction mechanisms for these enzymes is required for the design of highly potent, specific inhibitors that can function as potential pharmaceuticals. Hydrolytic enzymes …
Interaction Of Porcine Uterine Fluid Purple Acid Phosphatase With Vanadate And Vanadyl Cation, Debbie C. Carans, Carmen M. Simone, Richard C. Holz, Lawrence Que,Jr
Interaction Of Porcine Uterine Fluid Purple Acid Phosphatase With Vanadate And Vanadyl Cation, Debbie C. Carans, Carmen M. Simone, Richard C. Holz, Lawrence Que,Jr
Richard C. Holz
Uteroferrin, the purple acid phosphatase from porcine uterine fluid, is noncompetitively inhibited by vanadate in a time-dependent manner under both aerobic and anaerobic conditions. This time-dependent inhibition is observed only with the diiron enzyme and is absent when the FeZn enzyme is used. The observations are attributed to the sequential formation of two uteroferrin-vanadium complexes. The first complex forms rapidly and reversibly, while the second complex forms slowly and results in the production of catalytically inactive oxidized uteroferrin and V(IV), which is observed by EPR. The redox reaction can be reversed by treatment of the oxidized enzyme first with (V(1V)) …
The Aminopeptidase From Aeromonas Proteolytica Can Function As An Esterase, David Bienvenue, Rebecca Matthew, Dagmar Ringe, Richard Holz
The Aminopeptidase From Aeromonas Proteolytica Can Function As An Esterase, David Bienvenue, Rebecca Matthew, Dagmar Ringe, Richard Holz
Richard C. Holz
The aminopeptidase from Aeromonas proteolytica (AAP) can catalyze the hydrolysis of L-leucine ethyl ester (L-Leu-OEt) with a rate of 96±5 s–1 and a K m of 700 µM. The observed turnover number for L-Leu-OEt hydrolysis by AAP is similar to that observed for peptide hydrolysis, which is 67±5 s–1. The k cat values for the hydrolysis of L-Leu-OEt and L-leucine-p-nitroanilide (L-pNA) catalyzed by AAP were determined at different pH values under saturating substrate concentrations. Construction of an Arrhenius plot from the temperature dependence of AAP-catalyzed ester hydrolysis indicates that the rate-limiting step does not change as a function of temperature …
Characterization Of The Catalytically Active Mn(Ii)-Loaded Arge-Encoded N-Acetyl-L-Ornithine Deacetylase From Escherichia Coli, Wade Mcgregor, Sabina Swierczek, Brian Bennett, Richard Holz
Characterization Of The Catalytically Active Mn(Ii)-Loaded Arge-Encoded N-Acetyl-L-Ornithine Deacetylase From Escherichia Coli, Wade Mcgregor, Sabina Swierczek, Brian Bennett, Richard Holz
Richard C. Holz
The catalytically competent Mn(II)-loaded form of the argE-encoded N-acetyl-l-ornithine deacetylase from Escherichia coli (ArgE) was characterized by kinetic, thermodynamic, and spectroscopic methods. Maximum N-acetyl-l-ornithine (NAO) hydrolytic activity was observed in the presence of one Mn(II) ion with k cat and K m values of 550 s−1 and 0.8 mM, respectively, providing a catalytic efficiency (k cat/K m) of 6.9 × 105 M−1 s−1. The ArgE dissociation constant (K d) for Mn(II) was determined to be 0.18 μM, correlating well with a value obtained by isothermal titration …
Structural Evidence That The Methionyl Aminopeptidase From Escherichia Coli Is A Mononuclear Metalloprotease, Nathaniel Cosper, Ventris D'Souza, Robert Scott, Richard Holz
Structural Evidence That The Methionyl Aminopeptidase From Escherichia Coli Is A Mononuclear Metalloprotease, Nathaniel Cosper, Ventris D'Souza, Robert Scott, Richard Holz
Richard C. Holz
The Co and Fe K-edge extended X-ray absorption fine structure (EXAFS) spectra of the methionyl aminopeptidase from Escherichia coli (EcMetAP) have been recorded in the presence of 1 and 2 equiv of either Co(II) or Fe(II) (i.e., [Co(II)_(EcMetAP)], [Co(II)Co(II)(EcMetAP)], [Fe(II)_(EcMetAP)], and [Fe(II)Fe(II)(EcMetAP)]). The Fourier transformed data of both [Co(II)_(EcMetAP)] and [Co(II)Co(II)(EcMetAP)] are dominated by a peak at ca. 2.05 Å, which can be fit assuming 5 light atom (N,O) scatterers at 2.04 Å. Attempts to include a Co−Co interaction (in the 2.4−4.0 Å range) in the curve-fitting parameters were unsuccessful. Inclusion of multiple-scattering contributions from the outer-shell atoms of a …
Characterization Of The Active Site And Insight Into The Binding Mode Of The Anti-Angiogenesis Agent Fumagillin To The Manganese(Ii)-Loaded Methionyl Aminopeptidase From Escherichia Coli, Ventris D'Souza, Robert Brown, Brian Bennett, Richard Holz
Characterization Of The Active Site And Insight Into The Binding Mode Of The Anti-Angiogenesis Agent Fumagillin To The Manganese(Ii)-Loaded Methionyl Aminopeptidase From Escherichia Coli, Ventris D'Souza, Robert Brown, Brian Bennett, Richard Holz
Richard C. Holz
EPR spectra were recorded for methionine aminopeptidase from Escherichia coli (EcMetAP-I) samples (~2.5 mM) to which one and two equivalents of Mn(II) were added (the latter is referred to as [MnMn(EcMetAP-I)]). The spectra for each sample were indistinguishable except that the spectrum of [MnMn(EcMetAP-I)] was twice as intense. The EPR spectrum of [MnMn(EcMetAP-I)] exhibited the characteristic six-line g≈2 EPR signal of mononuclear Mn(II) with A av(55Mn)=9.3 mT (93 G) and exhibited Curie-law temperature dependence. This signal is typical of Mn(II) in a ligand sphere comprising oxygen and/or nitrogen …