scholarly journals General equations for determining species involved in solution equilibria and equilibrium constants from solution molecular mass measurements

1993 ◽  
Vol 58 (10) ◽  
pp. 2810-2816 ◽  
Author(s):  
Matthew G. Davidson ◽  
Ronald Snaith ◽  
Dietmar Stalke ◽  
Dominic S. Wright
Keyword(s):  
Molecular Mass ◽  
Equilibrium Constants ◽  
Mass Measurements ◽  
Solution Equilibria

Accuracy Requirements for Peptide Characterization by Monoisotopic Molecular Mass Measurements

1996 ◽  
Vol 68 (22) ◽  
pp. 4060-4063 ◽  
Author(s):  
Roman A. Zubarev ◽  
Per Håkansson ◽  
Bo Sundqvist
Keyword(s):  
Molecular Mass ◽  
Mass Measurements ◽  
Peptide Characterization

Modelling complex solution equilibria. II. Systems involving ligand substitutions and uncertainties in equilibrium constants derived from formation constants

1990 ◽  
Vol 68 (12) ◽  
pp. 2208-2211 ◽  
Author(s):  
Pierre G. Potvin
Keyword(s):  
Equilibrium Constants ◽  
Correlation Coefficients ◽  
Formation Constants ◽  
Ligand Substitution ◽  
Complex Solution ◽  
Unknown Parameters ◽  
Solution Equilibria

A general formalism is presented that expresses equilibrium constants K as combinations of pseudo-formation constants ψ. For equilibria involving complexes as reactants that undergo ligand substitutions, this formalism allows a reduction in the number of equations needed to model the system for faster calculation of species concentrations and refinement of unknown parameters. Gauss–Newton refinement of log ψ parameters is shown to be equivalent to that of log K parameters. Equations are developed for the calculation of uncertainties in log K and correlation coefficients between them from the corresponding values obtained for log ψ parameters. These equations can also be used to calculate the same quantities for constants (such as Ka's) derived from true formation constants. Keywords: Gauss–Newton, ligand substitution, equilibrium constants, formation constants.

Validation of molecular mass measurements by means of diffusion-ordered NMR spectroscopy: Application to oligosaccharides

2010 ◽  
Vol 13 (4) ◽  
pp. 412-415 ◽  
Author(s):  
Olivier Assemat ◽  
Marie-Aude Coutouly ◽  
Redouane Hajjar ◽  
Marc-André Delsuc
Keyword(s):  
Nmr Spectroscopy ◽  
Molecular Mass ◽  
Mass Measurements

Modelling complex solution equilibria. I. Fast, worry-free least-squares refinement of equilibrium constants

1990 ◽  
Vol 68 (12) ◽  
pp. 2198-2207 ◽  
Author(s):  
Pierre G. Potvin
Keyword(s):  
Least Squares ◽  
Taylor Series ◽  
Global Minimum ◽  
Infinite Order ◽  
Equilibrium Constants ◽  
Complex Solution ◽  
First Order ◽  
Solution Equilibria ◽  
Higher Derivatives ◽  
Series Expression

The methods of Steepest Descent, Gauss–Newton (first-order Taylor series) and Newton–Raphson (second-order Taylor series) least-squares iteration were examined in the context of the refinement of estimated equilibrium constants β in solution. Under certain conditions, all three can produce corrections to the parameters that overshoot the global minimum and diverge therefrom, owing to the shape of the parameter surface. The latter two methods are problematic when the β parameters are overestimated, or when their logarithms are underestimated, whence a useful approximation to the analytical second and higher derivatives was found for any data type. This reduces an exact, infinite-order Taylor series expression of any observable to a simple first-order expression. As illustrated with experimental pH data, faster, more reliable refinement results without overshoot or divergence problems, and without resort to computationally onerous algorithms, such as the Marquardt–Levenberg, Fletcher–Powell, or Hartley–Wentworth methods. Keywords: equilibrium constants, least-squares, Gauss–Newton, complex solution equilibria.

New validation of molecular mass measurements by means of 2D DOSY 1H NMR experiments: Application to surfactants

2015 ◽  
Vol 18 (2) ◽  
pp. 187-192 ◽  
Author(s):  
Maggy Hologne ◽  
Alexandra Gaubert ◽  
Corinne Sanglar ◽  
Claire Bordes ◽  
Hervé Casabianca
Keyword(s):  
Molecular Mass ◽  
1H Nmr ◽  
Mass Measurements

Cobalt(II), nickel(II), and copper(II) complexes of di- and tetrapeptides containing tyrosine and glycine residues

1979 ◽  
Vol 57 (1) ◽  
pp. 104-112 ◽  
Author(s):  
Mohamed S. El- Ezaby ◽  
Jassim M. Al-Hassan ◽  
Namek F. Eweiss ◽  
Farida Al-Massaad
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Mixed Solvent ◽  
Equilibrium Constants ◽  
Carboxyl Groups ◽  
Experimental Conditions ◽  
Ph Titration ◽  
Solution Equilibria ◽  
Wide Range ◽  
Ph Range

The solution equilibria of di- and tetrapeptides containing tyrosine and glycine residues have been investigated in absence and presence of cobalt(II), nickel(II), and copper(II) ions. The equilibrium constants have been determined by pH titration at 30 °C and μ = 0.1 M(NaNO3) in 80% by weight DMSO – water mixed solvent. Protons are ionized from terminal (protonated amino and carboxyl) groups as well as from peptidic nitrogens. Complexes of 1:1 composition of metal ion – tetrapeptides were formed in quite a wide range of pH; also 1:1 complexes of the metal ions – dipeptides were formed in solution under the same conditions. Other higher complexes cannot be proved to form in the pH range studied. The complexes of these metal ions with glycine and O-Bzl-L-tyrosine were also studied under the same experimental conditions as control experiments and their equilibrium constants were calculated.

Radial mass analysis of unstained STEM images of molluscan hemocyanins

1990 ◽  
Vol 48 (3) ◽  
pp. 810-811
Author(s):  
M.G. Hamilton ◽  
T.T. Herskovits ◽  
J.S. Wall
Keyword(s):  
Image Analysis ◽  
Hollow Cylinder ◽  
Electron Micrographs ◽  
Side View ◽  
Mass Analysis ◽  
Mass Measurements ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Microscopic Studies

The hemocyanins of molluscs are aggregates of a cylindrical decameric subparticle that assembles into di-, tri-, tetra-, penta-, and larger multi-decameric particles with masses that are multiples of the 4.4 Md decamer. Electron micrographs of these hemocyanins typically show the particles with two profiles: circular representing the cylinder viewed from the end and rectangular representing the side-view of the hollow cylinder.The model proposed by Mellema and Klug from image analysis of a didecameric hemocyanin with the two decamers facing one another with collar (closed) ends outward fits the appearance of side-views of the negatively-stained cylinders. These authors also suggested that there might be caps at the ends. In one of a series of transmission electron microscopic studies of molluscan hemocyanins, Siezen and Van Bruggen supported the Mellema-Klug model, but stated that they had never observed a cap component. With STEM we have tested the end cap hypothesis by direct mass measurements across the end-views of unstained particles.

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