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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
Molecular Interactions With Ice: Molecular Embedding, Adsorption, Detection, And Release, K D. Gibson, Grant G. Langlois, Wenxin Li, Daniel Killelea, S J. Sibener
Molecular Interactions With Ice: Molecular Embedding, Adsorption, Detection, And Release, K D. Gibson, Grant G. Langlois, Wenxin Li, Daniel Killelea, S J. Sibener
Chemistry: Faculty Publications and Other Works
The interaction of atomic and molecular species with water and ice is of fundamental importance for chemistry. In a previous series of publications, we demonstrated that translational energy activates the embedding of Xe and Kr atoms in the near surface region of ice surfaces. In this paper, we show that inert molecular species may be absorbed in a similar fashion.We also revisit Xe embedding, and further probe the nature of the absorption into the selvedge. CF4 molecules with high translational energies (≥3 eV) were observed to embed in amorphous solid water. Just as with Xe, the initial adsorption rate is …
A Novel Dual Allosteric Activation Mechanism Of Escherichia Coli Adp-Glucose Pyrophosphorylase: The Role Of Pyruvate, Matías D. Asención Diez, Mabel C. Aleanzi, Alberto A. Iglesias, Miguel Ballicora
A Novel Dual Allosteric Activation Mechanism Of Escherichia Coli Adp-Glucose Pyrophosphorylase: The Role Of Pyruvate, Matías D. Asención Diez, Mabel C. Aleanzi, Alberto A. Iglesias, Miguel Ballicora
Chemistry: Faculty Publications and Other Works
Fructose-1,6-bisphosphate activates ADP-glucose pyrophosphorylase and the synthesis of glycogen in Escherichia coli. Here, we show that although pyruvate is a weak activator by itself, it synergically enhances the fructose-1,6-bisphosphate activation. They increase the enzyme affinity for each other, and the combination increases Vmax, substrate apparent affinity, and decreases AMP inhibition. Our results indicate that there are two distinct interacting allosteric sites for activation. Hence, pyruvate modulates E. coli glycogen metabolism by orchestrating a functional network of allosteric regulators. We postulate that this novel dual activator mechanism increases the evolvability of ADP-glucose pyrophosphorylase and its related metabolic control.
Heavy Metal Analysis In Lens And Aqueous Humor Of Cataract Patients By Total Reflection X-Ray Fluorescence Spectrometry, Martina Schmeling, Bruce I. Gaines, Susanne Tidow-Kebritchi
Heavy Metal Analysis In Lens And Aqueous Humor Of Cataract Patients By Total Reflection X-Ray Fluorescence Spectrometry, Martina Schmeling, Bruce I. Gaines, Susanne Tidow-Kebritchi
Chemistry: Faculty Publications and Other Works
The human eye is continuously exposed to the environment yet little is known about how much of toxins, specifically heavy metals are present in its different parts and how they influence vision and acuity. To shed light into this subject, aqueous humor and lens samples were collected from 14 cataract patients to study the presence and concentration of selected metals in the eye. Subjects undergoing routine cataract surgery were consecutively enrolled for study by simple random sampling. Prior to surgery, subject demographic were compiled. The surgical procedure involved small incision cataract removal using phacoemulsification. During the procedure, a small aliquot …
Catalytic Kinetic Resolution Of A Dynamic Racemate: Highly Stereoselective Β-Lactone Formation By N-Heterocyclic Carbene Catalysis, Ryne C. Johnston, Daniel T. Cohen, Chad C. Eichman, Karl A. Scheidt, Paul Ha-Yeon Cheong
Catalytic Kinetic Resolution Of A Dynamic Racemate: Highly Stereoselective Β-Lactone Formation By N-Heterocyclic Carbene Catalysis, Ryne C. Johnston, Daniel T. Cohen, Chad C. Eichman, Karl A. Scheidt, Paul Ha-Yeon Cheong
Chemistry: Faculty Publications and Other Works
This study describes the combined experimental and computational elucidation of the mechanism and origins of stereoselectivities in the NHC-catalyzed dynamic kinetic resolution (DKR) of α-substituted-β-ketoesters. Density functional theory computations reveal that the NHC-catalyzed DKR proceeds by two mechanisms, depending on the stereochemistry around the forming bond: 1) a concerted, asynchronous formal (2+2) aldol-lactonization process, or 2) a stepwise spiro-lactonization mechanism where the alkoxide is trapped by the NHC-catalyst. These mechanisms contrast significantly from mechanisms found and postulated in other related transformations. Conjugative stabilization of the electrophile and non-classical hydrogen bonds are key in controlling the stereoselectivity. This reaction constitutes an …
The Dimerization Domain In Dape Enzymes Is Required For Catalysis, Boguslaw Nocek, Anna Starus, Magdalena Makowska-Grzyska, Blanca Gutierrez, Stephen Sanchez, Robert Jedrzejczak, Jamey C. Mack, Kenneth W. Olsen, Andrzej Joachimiak, Richard C. Holz
The Dimerization Domain In Dape Enzymes Is Required For Catalysis, Boguslaw Nocek, Anna Starus, Magdalena Makowska-Grzyska, Blanca Gutierrez, Stephen Sanchez, Robert Jedrzejczak, Jamey C. Mack, Kenneth W. Olsen, Andrzej Joachimiak, Richard C. Holz
Chemistry: Faculty Publications and Other Works
The emergence of antibiotic-resistant bacterial strains underscores the importance of identifying new drug targets and developing new antimicrobial compounds. Lysine and meso-diaminopimelic acid are essential for protein production and bacterial peptidoglycan cell wall remodeling and are synthesized in bacteria by enzymes encoded within dap operon. Thereforedap enzymes may serve as excellent targets for developing a new class of antimicrobial agents. The dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) convertsN-succinyl-L,L-diaminopimelic acid to L,L-diaminopimelic acid and succinate. The enzyme is composed of catalytic and dimerization domains, and belongs to the M20 peptidase family. To understand the specific role …
Parkinson Disease-Associated Mutation R1441h In Lrrk2 Prolongs The “Active State” Of Its Gtpase Domain, Jingling Liao, Chun-Xiang Wu, Christopher Burlak, Sheng Zhang, Dali Liu
Parkinson Disease-Associated Mutation R1441h In Lrrk2 Prolongs The “Active State” Of Its Gtpase Domain, Jingling Liao, Chun-Xiang Wu, Christopher Burlak, Sheng Zhang, Dali Liu
Chemistry: Faculty Publications and Other Works
Mutation in leucine-rich-repeat kinase 2 (LRRK2) is a common cause of Parkinson disease (PD). A disease-causing point mutation R1441H/G/C in the GTPase domain of LRRK2 leads to overactivation of its kinase domain. However, the mechanism by which this mutation alters the normal function of its GTPase domain [Ras of complex proteins (Roc)] remains unclear. Here, we report the effects of R1441H mutation (RocR1441H) on the structure and activity of Roc. We show that Roc forms a stable monomeric conformation in solution that is catalytically active, thus demonstrating that LRRK2 is a bona fide self-contained GTPase. We further show …
Analysis Of Genesis Sample 60234 By Laboratory Total Reflection X-Ray Fluorescence Spectrometry And Synchrotron Grazing Incidence X-Ray Fluorescence, Martina Schmeling, E. Hwang, Y. Choi, P.J. Eng, J.E. Stubbs, I.V. Veryovkin
Analysis Of Genesis Sample 60234 By Laboratory Total Reflection X-Ray Fluorescence Spectrometry And Synchrotron Grazing Incidence X-Ray Fluorescence, Martina Schmeling, E. Hwang, Y. Choi, P.J. Eng, J.E. Stubbs, I.V. Veryovkin
Chemistry: Faculty Publications and Other Works
Genesis sample 60234 was characterized by laboratory TXRF and synchrotron GI-XRF. Surface contaminants were identified as well as elements within the bulk.
Cellulose Acetate Replica Cleaning Study Of Genesis Non-Flight Sample 3cz00327, K.R. Kuhlman, Martina Schmeling, C.P. Gonzalez, J.H. Allton, D.S. Burnett
Cellulose Acetate Replica Cleaning Study Of Genesis Non-Flight Sample 3cz00327, K.R. Kuhlman, Martina Schmeling, C.P. Gonzalez, J.H. Allton, D.S. Burnett
Chemistry: Faculty Publications and Other Works
Cellulose acetate replica cleaning of Genesis samples is validated using control sample 3CZ00327. Residues are removed using hot xylene and acetone.