Mass Spectrometry Study and Infrared Spectroscopy of the Complex Between Camphor and the Two Enantiomers of Protonated Alanine: The Role of Higher-Energy Conformers in the Enantioselectivity of the Dissociation Rate Constants

Chirality ◽  
2013 ◽  
Vol 25 (8) ◽  
pp. 436-443 ◽  
Author(s):  
Ananya Sen ◽  
Katia Le Barbu-Debus ◽  
Debora Scuderi ◽  
Anne Zehnacker-Rentien
Keyword(s):  
Mass Spectrometry ◽  
Infrared Spectroscopy ◽  
Rate Constants ◽  
Dissociation Rate ◽  
Mass Spectrometry Study ◽  
Dissociation Rate Constants

scholarly journals Electrostatic and Hydrophobic Interactions Differentially Tune Membrane Binding Kinetics of the C2 Domain of Protein Kinase Cα

2013 ◽  
Vol 288 (23) ◽  
pp. 16905-16915 ◽  
Author(s):  
Angela M. Scott ◽  
Corina E. Antal ◽  
Alexandra C. Newton
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Rate Constants ◽  
Electrostatic Interactions ◽  
Hydrophobic Interactions ◽  
Dissociation Rate ◽  
C2 Domain ◽  
Pkc Isozymes ◽  
Dissociation Rate Constants

The cellular activation of conventional protein kinase C (PKC) isozymes is initiated by the binding of their C2 domains to membranes in response to elevations in intracellular Ca2+. Following this C2 domain-mediated membrane recruitment, the C1 domain binds its membrane-embedded ligand diacylglycerol, resulting in activation of PKC. Here we explore the molecular mechanisms by which the C2 domain controls the initial step in the activation of PKC. Using stopped-flow fluorescence spectroscopy to measure association and dissociation rate constants, we show that hydrophobic interactions are the major driving force in the binding of the C2 domain to anionic membranes, whereas electrostatic interactions dominate in membrane retention. Specifically, mutation of select hydrophobic or select basic residues in the Ca2+-binding loops reduces membrane affinity by distinct mechanisms; mutation of hydrophobic residues primarily alters association rate constants, whereas mutation of charged residues affects dissociation rate constants. Live cell imaging reveals that introduction of these mutations into full-length PKCα not only reduces the Ca2+-dependent translocation to plasma membrane but, by impairing the plasma membrane-sensing role of the C2 domain, causes phorbol ester-triggered redistribution of PKCα to other membranes, such as the Golgi. These data underscore the key role of the C2 domain in driving conventional PKC isozymes to the plasma membrane and reveal that not only the amplitude but also the subcellular location of conventional PKC signaling can be tuned by altering the affinity of this module for membranes.

An ICR mass spectrometry study of ion/molecule reactions between ethyl chloride and alkylamines

1991 ◽  
Vol 69 (2) ◽  
pp. 363-367
Author(s):  
Guoying Xu ◽  
Jan A. Herman
Keyword(s):  
Mass Spectrometry ◽  
Key Words ◽  
Rate Constant ◽  
Rate Constants ◽  
Ethyl Chloride ◽  
Ion Molecule Reactions ◽  
Mass Spectrometry Study ◽  
Ethyl Cation

Ion/molecule reactions in mixtures of ethyl chloride with C1–C4 alkylamines were studied by ICR mass spectrometry. Ethyl cation transfer to C1–C4 alkylamines proceeds mainly through diethylchloronium ions with rate constants ~3 × 10−10cm3 s−1. In the case of s-butylamine the corresponding rate constant is 0.5 × 10−10 cm3 s−1. Key words: ICR mass spectrometry, ion/molecule reactions, ethylchloride, methylamine, ethylamine, propylamines, butylamines

scholarly journals Dissociation Rate Constants of Human Fibronectin Binding to Fibronectin-binding Proteins on LivingStaphylococcus aureusIsolated from Clinical Patients

2012 ◽  
Vol 287 (9) ◽  
pp. 6693-6701 ◽  
Author(s):  
Nadia N. Casillas-Ituarte ◽  
Brian H. Lower ◽  
Supaporn Lamlertthon ◽  
Vance G. Fowler ◽  
Steven K. Lower
Keyword(s):  
Rate Constants ◽  
Binding Proteins ◽  
Dissociation Rate ◽  
Human Fibronectin ◽  
Fibronectin Binding ◽  
Dissociation Rate Constants

scholarly journals Head-to-tail polymerization of microtubules in vitro. Electron microscope analysis of seeded assembly.

1980 ◽  
Vol 84 (1) ◽  
pp. 141-150 ◽  
Author(s):  
L G Bergen ◽  
G G Borisy
Keyword(s):  
Electron Microscope ◽  
Rate Constants ◽  
Dissociation Constants ◽  
Dissociation Rate ◽  
Association Constants ◽  
Directional Growth ◽  
Microtubule Protein ◽  
Electron Microscope Analysis ◽  
Dissociation Rate Constants

Microtubules are polar structures, and this polarity is reflected in their biased directional growth. Following a convention established previously (G. G. Borisy, 1978, J. Mol. Biol. 124:565--570), we define the plus (+) and minus (-) ends of a microtubule as those equivalent in structural orientation to the distal and proximal ends, respectively, of the A subfiber of flagellar outer doublets. Rates of elongation were obtained for both ends using flagellar axonemes as seeds and porcine brain microtubule protein as subunits. Since the two ends of a flagellar seed are distinguishable morphologically, elongation of each end may be analyzed separately. By plotting rates of elongation at various concentrations of subunit protein, we have determined the association and dissociation rate constants for the plus and minus ends. Under our conditions at 30 degrees C, the association constants were 7.2 X 10(6) M-1 s-1 and 2.25 X 10(6) M-1 s-1 for the plus and minus ends, respectively, and the dissociation constants were 17 s-1 and 7 s-1. From these values and Wegner's equations (1976, J. Mol. Biol. 108:139--150), we identified the plus end of the microtubule as its head and calculated "s," the head-to-tail polymerization parameter. Surprisingly small values (s = 0.07 +/- 0.02) were found. The validity of models of mitosis based upon head-to-tail polymerization (Margolis et al., 1978, Nature (Lond.) 272:450--452) are discussed in light of a small value for s.

scholarly journals Mechanism of a Disassembly Driven Sensing System Studied by Stopped-Flow Kinetics

2021 ◽  
Author(s):  
Cara Gallo ◽  
Suma S. Thomas ◽  
Allison Selinger ◽  
Fraser Hof ◽  
Cornelia Bohne
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Artificial Saliva ◽  
Global Analysis ◽  
Dissociation Rate ◽  
Stopped Flow ◽  
Steady State Fluorescence ◽  
Saliva Analysis ◽  
Binding Isotherms ◽  
Dissociation Rate Constants

<div> Mechanistic studies were carried out on the kinetics for the assembly of a DimerDye (DD12) and the binding of the monomeric DimerDye (DD1) with nicotine in aqueous buffer and artificial saliva. DD12 is non-fluorescent, while monomeric DD1 and DD1-nicotine fluoresce. Binding isotherms were determined from steady-state fluorescence experiments. The report includes measurements of the steady-state fluorescence at pHs 2.2, 6.3 and 12.1, and stopped-flow kinetic data for the homodimerization forming DD12 and DD1-nicotine formation in buffer and artificial saliva. Analysis of the homodimerization kinetics led to the recovery of the association and dissociation rate constants for DD12. These rate constants were used in the global analysis for the coupled kinetics for DD1-nicotine formation, which led to the determination of the association and dissociation rate constants for nicotine binding to DD1.</div>

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