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Articles 331 - 360 of 397

Full-Text Articles in Chemistry

Rnase L: Its Biological Roles And Regulation, Shu Ling Liang, David Quirk, Aimin Zhou Sep 2006

Rnase L: Its Biological Roles And Regulation, Shu Ling Liang, David Quirk, Aimin Zhou

Chemistry Faculty Publications

2'-5'oligoadenylate-dependent ribonuclease L (RNase L) is one of the key enzymes involved in the function of interferons (IFNs), a family of cytokines participating in innate immunity against viruses and other microbial pathogens. Upon binding with its activator, 5'-phosphorylated, 2'-5' linked oligoadenylates (2-5A), RNase L degrades single-stranded viral and cellular RNAs and thus plays an important role in the antiviral and antiproliferative functions of IFNs. In recent years, evidence has revealed that RNase L displays a broad range of biological roles which are summarized in this review.

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10,10′-Dinitro-10,10′-(Butane-1,4-Di­Yl)Dianthracen-9(10h)-One, Mustafa Arslan, Erol Asker, John Masnovi, Ronald J. Baker Jul 2006

10,10′-Dinitro-10,10′-(Butane-1,4-Di­Yl)Dianthracen-9(10h)-One, Mustafa Arslan, Erol Asker, John Masnovi, Ronald J. Baker

Chemistry Faculty Publications

The title compound, C32H24N2O6, was obtained as the decomposition product of (E,E)-1,4-bis­[9,10-dihydro-9-nitro-10-(trinitro­meth­yl)-9-anthr­yl]butane, which was synthesized via a photochemical reaction of 1,4-bis­(9-anthr­yl)butane with tetra­nitro­methane. The asymmetric unit contains one half-mol­ecule; the complete mol­ecule is generated by a center of inversion. The crystal packing is determined mainly by inter­molecular C—H⋯O inter­actions.

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The Structural Integrity Of Anion Binding Exosite I Of Thrombin Is Required And Sufficient For Timely Cleavage And Activation Of Factor V And Factor Viii, Michael A. Bukys, Tivadar Orban, Paul Y. Kim, Daniel O. Beck, Michael E. Nesheim, Michael Kalafatis Jul 2006

The Structural Integrity Of Anion Binding Exosite I Of Thrombin Is Required And Sufficient For Timely Cleavage And Activation Of Factor V And Factor Viii, Michael A. Bukys, Tivadar Orban, Paul Y. Kim, Daniel O. Beck, Michael E. Nesheim, Michael Kalafatis

Chemistry Faculty Publications

Alpha-thrombin has two separate electropositive binding exosites (anion binding exosite I, ABE-I and anion binding exosite II, ABE-II) that are involved in substrate tethering necessary for efficient catalysis. Alpha-thrombin catalyzes the activation of factor V and factor VIII following discrete proteolytic cleavages. Requirement for both anion binding exosites of the enzyme has been suggested for the activation of both procofactors by alpha-thrombin. We have used plasma-derived alpha-thrombin, beta-thrombin (a thrombin molecule that has only ABE-II available), and a recombinant prothrombin molecule rMZ-II (R155A/R284A/R271A) that can only be cleaved at Arg(320) (resulting in an enzymatically active molecule that has only ABE-I …

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Numerical Simulation And Graphical Analysis Of In Vitro Benign Tumor Growth: Application Of Single-Particle State Bosonic Matter Equation With Length Scaling, Pradip K. Biswas, Jiansen Niu, Tobias Frederico, Valentin Gogonea Jul 2006

Numerical Simulation And Graphical Analysis Of In Vitro Benign Tumor Growth: Application Of Single-Particle State Bosonic Matter Equation With Length Scaling, Pradip K. Biswas, Jiansen Niu, Tobias Frederico, Valentin Gogonea

Chemistry Faculty Publications

We describe the application of a non-linear single-particle state bosonic condensate equation to simulate multicellular tumor growth by treating it as a coupling of two classical wave equations with real components. With one component representing the amplitude of the cells in their volume growth phase and the other representing the amplitude of the cells in their proliferation or mitosis phase, the two components of the coupled equation feed each other during the time evolution and are coupled together through diffusion and other linear and non-linear terms. The features of quiescent and necrotic cells, which result from poor nutrient diffusion into …

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10,10′-Dinitro-10,10′-(Propane-1,3-Di­Yl)Di-10h-Anthracen-9-One, Mustafa Arslan, Erol Asker, John Masnovi, Ronald J. Baker May 2006

10,10′-Dinitro-10,10′-(Propane-1,3-Di­Yl)Di-10h-Anthracen-9-One, Mustafa Arslan, Erol Asker, John Masnovi, Ronald J. Baker

Chemistry Faculty Publications

The title compound, C31H22N2O6, was obtained as the decomposition product of (E,E)-1,3-bis­[9,10-dihydro-9-nitro-10-(trinitro­meth­yl)-9-anthr­yl]propane, which was synthesized via a photochemical reaction of 1,3-di-9-anthrylpropane with tetra­nitro­methane. Inter­molecular C—H⋯O inter­actions are the most prominent features of the crystal packing; no indications of any inter­molecular π–π stacking were found.

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9-Ethyl-3-(9h-9-Ethyl­Carbazol-3-Yl)-4-Nitro­-9h-Carbazole, Erol Asker, John Masnovi Apr 2006

9-Ethyl-3-(9h-9-Ethyl­Carbazol-3-Yl)-4-Nitro­-9h-Carbazole, Erol Asker, John Masnovi

Chemistry Faculty Publications

In the mol­ecule of the title compound, C28H23N3O2, the nitro group is almost perpendicular to the carbazole ring to which it is attached. The crystal packing is determined by C—H⋯O and π–π inter­actions, where the nitrated carbazole ring of one mol­ecule associates in a shifted parallel planar orientation with the centrosymmetrically related non-nitrated carbazole ring of a neighbouring mol­ecule.

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Bis(9-Ethyl­Carbazol-3-Yl)Ethane, Erol Asker, John Masnovi Apr 2006

Bis(9-Ethyl­Carbazol-3-Yl)Ethane, Erol Asker, John Masnovi

Chemistry Faculty Publications

In the title compound, C30H28N2, each carbazole skeleton is essentially planar. The planes of the two carbazole ring systems are nearly parallel, with a dihedral angle of 2.33 (19)°. The crystal packing is stabilized only by van der Waals forces and weak C—H⋯π inter­actions.

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9,9′-Diethyl-3,3′-Di-9h-Carbazol­Yl, Erol Asker, John Masnovi Mar 2006

9,9′-Diethyl-3,3′-Di-9h-Carbazol­Yl, Erol Asker, John Masnovi

Chemistry Faculty Publications

In the title compound, C28H24N2, the carbazole ring systems are essentially planar to within 0.076 (3) Å. The dihedral angle between the planes of the ring systems is 40.38 (4)°. The contribution of inter­molecular π–π inter­actions to the mol­ecular stacking is observed.

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Bis(9-Ethyl­Carbazol-3-Yl)Methane, Erol Asker, John Masnovi Mar 2006

Bis(9-Ethyl­Carbazol-3-Yl)Methane, Erol Asker, John Masnovi

Chemistry Faculty Publications

In the title compound, C29H26N2, the carbazole ring systems are essentially planar. There is no indication of π–π interactions in the crystal structure, adjacent carbazole groups being non-parallel.

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Fluorescent Analysis Of Translesion Dna Synthesis By Using A Novel, Non-Natural Nucleotide Analogue, Irene Lee, Anthony J. Berdis Jan 2006

Fluorescent Analysis Of Translesion Dna Synthesis By Using A Novel, Non-Natural Nucleotide Analogue, Irene Lee, Anthony J. Berdis

Chemistry Faculty Publications

The replication of damaged DNA is a promutagenic process that can lead to disease development. This report evaluates the dynamics of nucleotide incorporation opposite an abasic site, a commonly formed DNA lesion, by using two fluorescent nucleotide analogues, 2-aminopurine deoxyribose triphosphate (2-APTP) and 5-phenylindole deoxyribose triphosphate (5-PhITP). In both cases, the kinetics of incorporation were compared by using a 32 P-radiolabel extension assay versus a fluorescence-quenching assay. Although 2-APTP is efficiently incorporated opposite a templating nucleobase (thymine), the kinetics for incorporation opposite an abasic site are significantly slower. The lower catalytic efficiency hinders its use as a probe to study …

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Recent Developments Inthe Mechanistic Enzymology Of The Atp-Dependent Lon Protease From Escherichia Coli: Highlights From Kinetic Studies, Irene Lee, Anthony J. Berdis, Carolyn K. Suzuki Jan 2006

Recent Developments Inthe Mechanistic Enzymology Of The Atp-Dependent Lon Protease From Escherichia Coli: Highlights From Kinetic Studies, Irene Lee, Anthony J. Berdis, Carolyn K. Suzuki

Chemistry Faculty Publications

Lon protease, also known as protease La, is one of the simplest ATP-dependent proteases that plays vital roles in maintaining cellular functions by selectively eliminating misfolded, damaged and certain short-lived regulatory proteins. Although Lon is a homo-oligomer, each subunit of Lon contains both an ATPase and a protease active site. This relatively simple architecture compared to other hetero-oligomeric ATP-dependent proteases such as the proteasome makes Lon a useful paradigm for studying the mechanism of ATP-dependent proteolysis. In this article, we survey some recent developments in the mechanistic characterization of Lon with an emphasis on the utilization of pre-steady-state enzyme kinetic …

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(E)-9,10-Dihydro-9-Methyl-9-Nitro-10-(Trinitro­Meth­Yl)Anthracene, Mustafa Arslan, Ronald J. Baker, John Masnovi, Erol Asker Dec 2005

(E)-9,10-Dihydro-9-Methyl-9-Nitro-10-(Trinitro­Meth­Yl)Anthracene, Mustafa Arslan, Ronald J. Baker, John Masnovi, Erol Asker

Chemistry Faculty Publications

The title compound, C16H12N4O8, was prepared by the photochemical reaction of 9-methyl­anthracene and tetra­nitro­methane in dichloromethane. Intermolecula face-to-face π–π stacking inter­actions are present along the a axis.

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Lead Optimization Of 7-Benzyloxy 2-(4′-Pyridylmethyl)Thio Isoflavone Aromatase Inhibitors, Bin Su, John C. Hackett, Edgar S. Diaz-Cruz, Young Woo Kim, Robert W. Brueggemeier Dec 2005

Lead Optimization Of 7-Benzyloxy 2-(4′-Pyridylmethyl)Thio Isoflavone Aromatase Inhibitors, Bin Su, John C. Hackett, Edgar S. Diaz-Cruz, Young Woo Kim, Robert W. Brueggemeier

Chemistry Faculty Publications

Aromatase, the enzyme responsible for estrogen biosynthesis, is a particularly attractive target in the treatment of hormone-dependent breast cancer. The synthesis and biological evaluation of a series of 2-(4′-pyridylmethyl)thio, 7-alkyl- or aryl-substituted isoflavones as potential aromatase inhibitors are described. The isoflavone derivatives demonstrate IC50 values from 79 to 553 nM and compete with the endogenous substrate, androstenedione. Data supporting the ability of these analogs to suppress aromatase enzyme activity in the SK-BR-3 breast cancer cell line are also presented.

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1,3-Bis(9-Ethyl­Carbazol-3-Yl)Propane, Erol Asker, John Masnovi Sep 2005

1,3-Bis(9-Ethyl­Carbazol-3-Yl)Propane, Erol Asker, John Masnovi

Chemistry Faculty Publications

In the title compund, C31H30N2, π–π overlap is absent in the region where carbazole groups of two adjacent mol­ecules are inclined toward each other. The eth­yl groups which protrude from the plane of the carbazole groups and the alkyl­ene chain connecting the two carbazole groups are responsible for the poor mol­ecular stacking.

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Incorporation Of Factor Va Into Prothrombinase Is Required For Coordinated Cleavage Of Prothrombin By Factor Xa, Michael A. Bukys, Melissa A. Blum, Paul Y. Kim, Nicole Brufatto, Michael E. Nesheim, Michael Kalafatis Jul 2005

Incorporation Of Factor Va Into Prothrombinase Is Required For Coordinated Cleavage Of Prothrombin By Factor Xa, Michael A. Bukys, Melissa A. Blum, Paul Y. Kim, Nicole Brufatto, Michael E. Nesheim, Michael Kalafatis

Chemistry Faculty Publications

Prothrombin is activated to thrombin by two sequential factor Xa-catalyzed cleavages, at Arg271 followed by cleavage at Arg320. Factor Va, along with phospholipid and Ca2+, enhances the rate of the process by 300,000-fold, reverses the order of cleavages, and directs the process through the meizothrombin pathway, characterized by initial cleavage at Arg320. Previous work indicated reduced rates of prothrombin activation with recombinant mutant factor Va defective in factor Xa binding (E323F/Y324F and E330M/V331I, designated factor VaFF/MI). The present studies were undertaken to determine whether loss of activity can be attributed to selective loss of efficiency at one or both of …

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Synthesis And Characterization Of Azole Isoflavone Inhibitors Of Aromatase, John C. Hackett, Young Woo Kim, Bin Su, Robert W. Brueggemeier Jun 2005

Synthesis And Characterization Of Azole Isoflavone Inhibitors Of Aromatase, John C. Hackett, Young Woo Kim, Bin Su, Robert W. Brueggemeier

Chemistry Faculty Publications

The synthesis and biological evaluation of a series of 2-azole and 2-thioazole isoflavones as potential aromatase inhibitors are described. Differences in inhibitory activity of triazole and imidazole inhibitors are rationalized with density functional theory to expose a key difference in the electronic structure of these molecules. In addition, difference binding spectra of inhibitors to immunoaffinity-purified aromatase produces classical Type II spectra consistent with coordination of the nitrogen lone pair electrons to the aromatase P450 heme.

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Double-Stranded Rna-Dependent Protein Kinase (Pkr) Is Downregulated By Phorbol Ester, Yan Zhou, Barbara I. Chase, Mark Whitmore, Bryan R.G. Williams, Aimin Zhou Apr 2005

Double-Stranded Rna-Dependent Protein Kinase (Pkr) Is Downregulated By Phorbol Ester, Yan Zhou, Barbara I. Chase, Mark Whitmore, Bryan R.G. Williams, Aimin Zhou

Chemistry Faculty Publications

The double-stranded RNA-dependent protein kinase (PKR) is one of the key mediators of interferon (IFN) action against certain viruses. PKR also plays an important role in signal transduction and immunomodulation. Understanding the regulation of PKR activity is important for the use of PKR as a tool to discover and develop novel therapeutics for viral infections, cancer and immune dysfunction. We found that phorbol 12-myristate 13-acetate (PMA), a potent activator of protein kinase C (PKC), decreased the level of autophosphorylated PKR in a dose- and time-dependent manner in IFN-treated mouse fibroblast cells. Polyinosinic–polycytidylic acid (poly I:C) treatment enhanced the activity of …

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Potential Energy Surface Of The Reaction Of Imidazole With Peroxynitrite: Density Functional Theory Study, Valentin Gogonea Jan 2005

Potential Energy Surface Of The Reaction Of Imidazole With Peroxynitrite: Density Functional Theory Study, Valentin Gogonea

Chemistry Faculty Publications

This article presents a theoretical investigation of the reaction mechanism of imidazole nitration by peroxynitrite using density functional theory calculations. Understanding this reaction mechanism will help in elucidating the mechanism of guanine nitration by peroxynitrite, which is one of the assumed chemical pathways for damaging DNA in cells. This work focuses on the analysis of the potential energy surface (PES) for this reaction in the gas phase. Calculations were carried out using Hartree–Fock (HF) and density functional theory (DFT) Hamiltonians with double-zeta basis sets ranging from 6-31G(d) to 6-31++G(d,p), and the triple-zeta basis set 6-311G(d). The computational results reveal that …

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A Regularized And Renormalized Electrostatic Coupling Hamiltonian For Hybrid Quantum-Mechanical–Molecular-Mechanical Calculations, Pradip K. Biswas, Valentin Gogonea Jan 2005

A Regularized And Renormalized Electrostatic Coupling Hamiltonian For Hybrid Quantum-Mechanical–Molecular-Mechanical Calculations, Pradip K. Biswas, Valentin Gogonea

Chemistry Faculty Publications

We describe a regularized and renormalized electrostatic coupling Hamiltonian for hybrid quantum-mechanical (QM)–molecular-mechanical (MM) calculations. To remedy the nonphysical QM/MM Coulomb interaction at short distances arising from a point electrostatic potential (ESP) charge of the MM atom and also to accommodate the effect of polarized MM atom in the coupling Hamiltonian, we propose a partial-wave expansion of the ESP charge and describe the effect of a s-wave expansion, extended over the covalent radius rc, of the MM atom. The resulting potential describes that, at short distances, large scale cancellation of Coulomb interaction arises intrinsically from the localized expansion of the …

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9-Ethyl-3-Methyl-1, 6-Dinitrocarbazole, Erol Asker, John Masnovi Sep 2004

9-Ethyl-3-Methyl-1, 6-Dinitrocarbazole, Erol Asker, John Masnovi

Chemistry Faculty Publications

No abstract provided.

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Phospholipid Scramblase 1 Potentiates The Antiviral Activity Of Interferon, Beihua Dong, Quansheng Zhou, Ji Zhao, Aimin Zhou, Ronald N. Harty, Santanu Bose, Amiya Banerjee, Roger Slee, Jeanna Guenther, Bryan R.G. Williams, Therese Wiedmer, Peter J. Sims, Robert H. Silverman Sep 2004

Phospholipid Scramblase 1 Potentiates The Antiviral Activity Of Interferon, Beihua Dong, Quansheng Zhou, Ji Zhao, Aimin Zhou, Ronald N. Harty, Santanu Bose, Amiya Banerjee, Roger Slee, Jeanna Guenther, Bryan R.G. Williams, Therese Wiedmer, Peter J. Sims, Robert H. Silverman

Chemistry Faculty Publications

Phospholipid scramblase 1 (PLSCR1) is an interferon (IFN)- and growth factor-inducible, calcium-binding protein that either inserts into the plasma membrane or binds DNA in the nucleus depending on its state of palmyitoylation. In certain hematopoietic cells, PLSCR1 is required for normal maturation and terminal differentiation from progenitor cells as regulated by select growth factors, where it promotes recruitment and activation of Src kinases. PLSCR1 is a substrate of Src (and Abl) kinases, and transcription of the PLSCR1 gene is regulated by the same growth factor receptor pathways in which PLSCR1 potentiates afferent signaling. The marked transcriptional upregulation of PLSCR1 by …

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Eliminating Absorbing Interference Using The H-Point Standard Addition Method: Case Of Griess Assay In The Presence Of Interferent Heme Enzymes Such As Nos, Perera N. Indika, Mekki Bayachou Aug 2004

Eliminating Absorbing Interference Using The H-Point Standard Addition Method: Case Of Griess Assay In The Presence Of Interferent Heme Enzymes Such As Nos, Perera N. Indika, Mekki Bayachou

Chemistry Faculty Publications

Standard calibration methods used to determine trace analytes usually yield significant deviations from the actual analyte value in the presence of interferents in the assay media. These deviations become of particular concern when the concentration of the analyte is low, and when the results are used to draw mechanistic or kinetic conclusions, for instance in enzyme structure-function studies. In these circumstances, the H-point standard addition method (HPSAM) provides superior precision and accuracy. This method is developed here for the case of the spectrophotometric Griess assay used to determine nitrite in various enzymology investigations, such as nitrite determination in studies of …

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Evaluating The Contributions Of Desolvation And Base-Stacking During Translesion Dna Synthesis, Xuemei Zhang, Irene Lee, Anthony J. Berdis May 2004

Evaluating The Contributions Of Desolvation And Base-Stacking During Translesion Dna Synthesis, Xuemei Zhang, Irene Lee, Anthony J. Berdis

Chemistry Faculty Publications

DNA polymerases catalyze the insertion of a nucleoside triphosphate into the growing polymer chain using the template strand as a guide. Numerous factors such as hydrogen bonding interactions, base-stacking contributions, and desolvation play important roles in controlling the efficiency and fidelity of this process. We previously demonstrated that 5-nitro-indolyl-2′-deoxyriboside triphosphate, a non-natural nucleobase with enhanced base-stacking properties, was more efficiently inserted opposite a non-templating DNA lesion compared to natural templating nucleobases (E. Z. Reineks and A. J. Berdis, Biochemistry, 2004, 43, 393–404). The catalytic enhancement was proposed to reflect increased base-stacking interactions of the non-natural nucleobase with the polymerase and …

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Measurement Of The Anticancer Agent Gemcitabine And Its Deaminated Metabolite At Low Concentrations In Human Plasma By Liquid Chromatography-Mass Spectrometry, Yan Xu, Bruce Keith, Jean L. Grem Apr 2004

Measurement Of The Anticancer Agent Gemcitabine And Its Deaminated Metabolite At Low Concentrations In Human Plasma By Liquid Chromatography-Mass Spectrometry, Yan Xu, Bruce Keith, Jean L. Grem

Chemistry Faculty Publications

A liquid chromatography/mass spectrometry (LC-MS) method has been developed and validated for the determination of the anticancer agent gemcitabine (dFdC) and its metabolite 2′,2′-difluoro-2′-deoxyuridine (dFdU) in human plasma. An Oasis® HLB solid phase extraction cartridge was used for plasma sample preparation. Separation of the analytes was achieved with a YMC ODS-AQ (5 μm, 120 Å, mm) column. The initial composition of the mobile phase was 2% methanol/98% 5 mM ammonium acetate at pH 6.8 (v/v), and the flow rate was 0.2 ml/min. An isocratic gradient was used for 3 min, followed by a linear gradient over 4 min to 30% …

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The Contribution Of Amino Acid Region Asp695-Tyr698 Of Factor V To Procofactor Activation And Factor Va Function, Daniel O. Beck, Michael A. Bukys, Lisam S. Singh, Katalin A. Szabo, Michael Kalafatis Jan 2004

The Contribution Of Amino Acid Region Asp695-Tyr698 Of Factor V To Procofactor Activation And Factor Va Function, Daniel O. Beck, Michael A. Bukys, Lisam S. Singh, Katalin A. Szabo, Michael Kalafatis

Chemistry Faculty Publications

There is strong evidence that a functionally important cluster of amino acids is located on the COOH-terminal portion of the heavy chain of factor Va, between amino acid residues 680 and 709. To ascertain the importance of this region for cofactor activity, we have synthesized five overlapping peptides representing this amino acid stretch (10 amino acids each, HC1-HC5) and tested them for inhibition of prothrombinase assembly and function. Two peptides, HC3 (spanning amino acid region 690-699) and HC4 (containing amino acid residues 695-704), were found to be potent inhibitors of prothrombinase activity with IC(50) values of approximately 12 and approximately …

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Characterization Of Drawn And Undrawn Poly-L-Lactide Films By Differential Scanning Calorimetry, John F. Turner Ii, A. Riga, Anne O'Connor, Jing Zhang, Jennifer Collis Jan 2004

Characterization Of Drawn And Undrawn Poly-L-Lactide Films By Differential Scanning Calorimetry, John F. Turner Ii, A. Riga, Anne O'Connor, Jing Zhang, Jennifer Collis

Chemistry Faculty Publications

Poly-L-lactic acid (PLLA) is an optically active, biocompatible and biodegradable polymer that has been widely investigated as an artificial cell scaffold material. In its most crystalline form, PLLA is highly anisotropic and is one of the most piezoelectric polymers known. Conversely, amorphous PLLA exhibits little, if any, piezoelectric behavior. Compression molded PLLA films can be endowed with varying amounts of crystalline character and piezoelectricity by uniaxially stretching the polymer in a hot air bath. Understanding the precise crystalline architecture of PLLA that results from tensile drawing is important for constructing cell scaffolds that have highly tailored biodegradation and cell guiding …

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Determination Of Crystalline Content Gradients In Cold-Drawn Poly-L-Lactic Acid Films By Dsc, Anne O'Connor, A. Riga, John F. Turner Ii Jan 2004

Determination Of Crystalline Content Gradients In Cold-Drawn Poly-L-Lactic Acid Films By Dsc, Anne O'Connor, A. Riga, John F. Turner Ii

Chemistry Faculty Publications

Poly-L-lactic acid (PLLA) is a semi-crystalline, optically active, biodegradable, and biocompatible polymer that has been utilized extensively in biomedical applications as an implantable artificial cell scaffold material. In its crystalline form, PLLA is piezoelectric and it has been implicated in the enhancement of electromechanically induced osteogenesis in vivo. In its amorphous state, however, PLLA does not exhibit piezoelectricity. By uniaxially cold-drawing the polymer, PLLA can be endowed with varying degrees of piezoelectricity. It is important to understand the crystalline architecture of drawn PLLA so that the osteogenic potential imparted by piezoelectricity, if any, can be differentiated from the effects of …

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Measurement Of Anti-Cancer Agent Methoxyamine In Plasma By Tandem Mass Spectrometry With On-Line Sample Extraction, Shuming Yang, Lili Liu, Stanton L. Gerson, Yan Xu Oct 2003

Measurement Of Anti-Cancer Agent Methoxyamine In Plasma By Tandem Mass Spectrometry With On-Line Sample Extraction, Shuming Yang, Lili Liu, Stanton L. Gerson, Yan Xu

Chemistry Faculty Publications

In this work, we present the development and validation of a tandem mass spectrometry method for the quantitative determination of methoxyamine (CH3ONH2), a potential new chemotherapeutic agent, in human and mouse plasma. Methoxyamine together with the internal standard (I.S.) methoxyl-D3-amine was directly derivatized in plasma sample with a novel chemical agent 4-(N,N-diethylamino)benzaldehyde. The product solution was injected into an on-line Oasis® HLB extraction column ( mm) for analyte extraction. After the elution of extractives, the derivatized analytes were monitored by the positive-electrospray-ionization mass spectrometry (ESI-MS-MS). The structures of derivatized analytes were elucidated by fragmentation. Quantitation of plasma methoxyamine was carried …

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Structural Requirements For Expression Of Factor Va Activity, Michael Kalafatis, Daniel O. Beck, Kenneth G. Mann Aug 2003

Structural Requirements For Expression Of Factor Va Activity, Michael Kalafatis, Daniel O. Beck, Kenneth G. Mann

Chemistry Faculty Publications

Thrombin activated factor Va (factor VIIa, residues 1-709 and 1546-2196) has an apparent dissociation constant (Kd,app) for factor Xa within prothrombinase of approximately 0.5 nM. A protease (NN) purified from the venom of the snake Naja nigricollis nigricollis, cleaves human factor V at Asp697, Asp1509, and Asp1514 to produce a molecule (factor VNN) that is composed of a Mr 100,000 heavy chain (amino acid residues 1-696) and a Mr 80,000 light chain (amino acid residues 1509/1514-2196). Factor VNN, has a Kd,app for factor Xa of 4 nm and reduced clotting activity. Cleavage of factor VIIa by NN at Asp697 results …

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Amino Acids Glu323, Tyr324, Glu330, And Val331 Of Factor Va Heavy Chain Are Essential For Expression Of Cofactor Activity, Lisam S. Singh, Michael A. Bukys, Daniel O. Beck, Michael Kalafatis Jul 2003

Amino Acids Glu323, Tyr324, Glu330, And Val331 Of Factor Va Heavy Chain Are Essential For Expression Of Cofactor Activity, Lisam S. Singh, Michael A. Bukys, Daniel O. Beck, Michael Kalafatis

Chemistry Faculty Publications

We have recently demonstrated that amino acid region 323-331 of factor Va heavy chain (9 amino acids, AP4') contains a binding site for factor Xa (Kalafatis, M., and Beck, D. O. (2002) Biochemistry 41, 12715-12728). To ascertain which amino acids within this region are important for the effector and receptor properties of the cofactor with respect to factor Xa, we have synthesized three overlapping peptides (5 amino acids each) spanning the amino acid region 323-331 and tested them for their effect on prothrombinase complex assembly and function. Peptide containing amino acids 323EYFIA327 alone was found to increase the catalytic efficiency …

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