Kinetics of Hydrogen Halides in Shock Waves. II. A New Measurement of the Hydrogen Dissociation Rate

1967 ◽  
Vol 47 (1) ◽  
pp. 54-57 ◽  
Author(s):  
T. A. Jacobs ◽  
R. R. Giedt ◽  
Norman Cohen
Keyword(s):  
Shock Waves ◽  
Dissociation Rate ◽  
Hydrogen Halides ◽  
Hydrogen Dissociation ◽  
Kinetics Of

Kinetics of Hydrogen Halides in Shock Waves: HCl and DCl

1967 ◽  
Vol 46 (5) ◽  
pp. 1958-1968 ◽  
Author(s):  
T. A. Jacobs ◽  
Norman Cohen ◽  
R. R. Giedt
Keyword(s):  
Shock Waves ◽  
Hydrogen Halides ◽  
Kinetics Of

Kinetics of Hydrogen Halides in Shock Waves. IV. HBr

1969 ◽  
Vol 50 (12) ◽  
pp. 5374-5378 ◽  
Author(s):  
R. R. Giedt ◽  
N. Cohen ◽  
T. A. Jacobs
Keyword(s):  
Shock Waves ◽  
Hydrogen Halides ◽  
Kinetics Of

scholarly journals Desensitization Contributes to the Synaptic Response of Gain-of-Function Mutants of the Muscle Nicotinic Receptor

2006 ◽  
Vol 128 (5) ◽  
pp. 615-627 ◽  
Author(s):  
Sergio Elenes ◽  
Ying Ni ◽  
Gisela D. Cymes ◽  
Claudio Grosman
Keyword(s):  
Nicotinic Receptor ◽  
Dissociation Rate ◽  
Gain Of Function ◽  
Naturally Occurring ◽  
Channel Opening ◽  
Speed Up ◽  
High Concentrations ◽  
Dissociation Rate Constants ◽  
Kinetics Of ◽  
Peak Value

Although the muscle nicotinic receptor (AChR) desensitizes almost completely in the steady presence of high concentrations of acetylcholine (ACh), it is well established that AChRs do not accumulate in desensitized states under normal physiological conditions of neurotransmitter release and clearance. Quantitative considerations in the framework of plausible kinetic schemes, however, lead us to predict that mutations that speed up channel opening, slow down channel closure, and/or slow down the dissociation of neurotransmitter (i.e., gain-of-function mutations) increase the extent to which AChRs desensitize upon ACh removal. In this paper, we confirm this prediction by applying high-frequency trains of brief (∼1 ms) ACh pulses to outside-out membrane patches expressing either lab-engineered or naturally occurring (disease-causing) gain-of-function mutants. Entry into desensitization was evident in our experiments as a frequency-dependent depression in the peak value of succesive macroscopic current responses, in a manner that is remarkably consistent with the theoretical expectation. We conclude that the comparatively small depression of the macroscopic currents observed upon repetitive stimulation of the wild-type AChR is due, not to desensitization being exceedingly slow but, rather, to the particular balance between gating, entry into desensitization, and ACh dissociation rate constants. Disruption of this fine balance by, for example, mutations can lead to enhanced desensitization even if the kinetics of entry into, and recovery from, desensitization themselves are not affected. It follows that accounting for the (usually overlooked) desensitization phenomenon is essential for the correct interpretation of mutagenesis-driven structure–function relationships and for the understanding of pathological synaptic transmission at the vertebrate neuromuscular junction.

scholarly journals Oversized galactosides as a probe for conformational dynamics in LacY

2018 ◽  
Vol 115 (16) ◽  
pp. 4146-4151 ◽  
Author(s):  
Irina Smirnova ◽  
Vladimir Kasho ◽  
Xiaoxu Jiang ◽  
Hong-Ming Chen ◽  
Stephen G. Withers ◽  
...  
Keyword(s):  
Binding Site ◽  
Conformational Dynamics ◽  
Dissociation Rate ◽  
Binding Kinetics ◽  
Lactose Permease ◽  
E Coli ◽  
Open Conformation ◽  
Dissociation Rate Constants ◽  
Kinetics Of ◽  
Micromolar Range

Binding kinetics of α-galactopyranoside homologs with fluorescent aglycones of different sizes and shapes were determined with the lactose permease (LacY) of Escherichia coli by FRET from Trp151 in the binding site of LacY to the fluorophores. Fast binding was observed with LacY stabilized in an outward-open conformation (kon = 4–20 μM−1·s−1), indicating unobstructed access to the binding site even for ligands that are much larger than lactose. Dissociation rate constants (koff) increase with the size of the aglycone so that Kd values also increase but remain in the micromolar range for each homolog. Phe27 (helix I) forms an apparent constriction in the pathway for sugar by protruding into the periplasmic cavity. However, replacement of Phe27 with a bulkier Trp does not create an obstacle in the pathway even for large ligands, since binding kinetics remain unchanged. High accessibility of the binding site is also observed in a LacY/nanobody complex with partially blocked periplasmic opening. Remarkably, E. coli expressing WT LacY catalyzes transport of α- or β-galactopyranosides with oversized aglycones such as bodipy or Aldol518, which may require an extra space within the occluded intermediate. The results confirm that LacY specificity is strictly directed toward the galactopyranoside ring and also clearly indicate that the opening on the periplasmic side is sufficiently wide to accommodate the large galactoside derivatives tested here. We conclude that the actual pathway for the substrate entering from the periplasmic side is wider than the pore diameter calculated in the periplasmic-open X-ray structures.

Kinetics of energy liberation during thermal decomposition of nitrates in shock waves

1988 ◽  
Vol 24 (2) ◽  
pp. 251-255 ◽  
Author(s):  
I. S. Zaslonko ◽  
V. N. Smirnov ◽  
A. M. Tereza ◽  
S. A. Tsyganov
Keyword(s):  
Thermal Decomposition ◽  
Shock Waves ◽  
Energy Liberation ◽  
Kinetics Of

scholarly journals Kinetics of the inhibition of human factor Xa by full-length and truncated recombinant tissue factor pathway inhibitor

1994 ◽  
Vol 297 (1) ◽  
pp. 131-136 ◽  
Author(s):  
T Lindhout ◽  
G Willems ◽  
R Blezer ◽  
H C Hemker
Keyword(s):  
Tissue Factor ◽  
Tissue Factor Pathway Inhibitor ◽  
Factor Xa ◽  
Product Formation ◽  
Dissociation Rate ◽  
Full Length ◽  
Inhibition Constant ◽  
Half Time ◽  
Tissue Factor Pathway ◽  
Kinetics Of

The inhibition equilibrium and kinetics of association and dissociation of the binding of three types of recombinant tissue factor pathway inhibitor (TFPI), namely full-length TFPI, C-terminal-truncated TFPI, and TFPI without the third Kunitz domain (TFPI1-161), to factor Xa have been measured. Formation and dissociation of the complexes were monitored by continuous measurement of the changes in the rate of hydrolysis of a peptidyl-p-nitroanilide substrate. Progress curves of product formation were fitted to a set of equations describing a one-step bimolecular inhibitory reaction in the presence of a competing substrate. For full-length TFPI the rate constants of association (kon) and dissociation (koff) were (5.1 +/- 0.7) x 10(6) M-1.s-1 and (2.6 +/- 0.9) x 10(-4)s-1 respectively. Thus, although the inhibition constant (50 pM) is far below the plasma concentration (2.5 nM) of TFPI, the half-time for transition to equilibrium in plasma is rather long (66s). The truncated forms of TFPI differ in that they have a 4-fold lower kon value but a similar dissociation rate constant. Therefore the inhibition constant, Ki, is 4-fold higher (0.2 nM) and the half-time to achieve equilibrium is prolonged to 250 s. The kon values of full-length and C-terminal-truncated TFPI, but not that of TFPI1-161, were found to decrease with increasing ionic strength.

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