Medium Effect on the Second-Stage Dissociation Constant of N,N-Bis(2-hydroxyethyl)glycine

1994 ◽  
Vol 39 (3) ◽  
pp. 599-601 ◽  
Author(s):  
H. A. Azab ◽  
Z. A. Khafagy ◽  
Ahmed Hassan ◽  
A. M. El-Nady
Keyword(s):  
Dissociation Constant ◽  
Medium Effect ◽  
Second Stage

Medium effect on the second-stage dissociation constant of N-(2-acetamido)imino diacetic acid (H2ADA)

1992 ◽  
Vol 70 (6) ◽  
pp. 1684-1687 ◽  
Author(s):  
Ahmed Hassan ◽  
H. A. Azab ◽  
S. A. El Gyar ◽  
Z. A. Khafagy
Keyword(s):  
Dissociation Constant ◽  
Aqueous Media ◽  
Acid Dissociation ◽  
Medium Effect ◽  
Solvent Mixtures ◽  
Diacetic Acid ◽  
Imino Group ◽  
Second Stage ◽  
Dissociation Equilibrium ◽  
Imino Diacetic Acid

The second-stage dissociation constant values of N-(2-acetamido)imino diacetic acid (H2ADA) were determined at 25 ± 0.1 °C by potentiometric titration in different mixed-solvent mixtures (methanol, ethanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, and dioxane). It was observed that the pKa value is slightly influenced as the solvent is enriched in methanol and ethanol, and remains practically constant in the presence of different amounts of DMF and DMSO. A prounounced change in the pKa value was observed as the solvent is enriched in acetone or dioxane. These results are discussed in terms of various solvent characteristics. It is concluded that the electrostatic effect has only a relatively small influence on the dissociation equilibrium of the imino group [Formula: see text]. Other solvent effects such as solvent basicity, different stabilization of the free base of the conjugate acid by hydrogen bonding interactions in aquoorganic solvent media relative to pure aqueous media, as well as proton–solvent interaction play an important role in the acid dissociation equilibrium.

ChemInform Abstract: Medium Effect on the Second Dissociation Constant of Amino Acids

ChemInform ◽  
1989 ◽  
Vol 20 (5) ◽  
Author(s):  
M. R. MAHMOUD ◽  
A. M. EL ROUDI ◽  
A. A. ABD EL GABER ◽  
E. M. ABD ALLA
Keyword(s):  
Amino Acids ◽  
Dissociation Constant ◽  
Medium Effect ◽  
Second Dissociation Constant

ULTRAVIOLET STUDY OF THE IONIZATION OF BISULFATE ION

1965 ◽  
Vol 43 (10) ◽  
pp. 2867-2871 ◽  
Author(s):  
J. T. Edward ◽  
I. C. Wang
Keyword(s):  
Sulfuric Acid ◽  
Aqueous Solutions ◽  
Dissociation Constant ◽  
Optical Density ◽  
Univalent Cations ◽  
Sulfate Ion ◽  
Sodium Potassium ◽  
Second Stage ◽  
Dilute Aqueous Solutions ◽  
Raman Spectral

Studies of the ultraviolet absorption of dilute aqueous solutions of lithium, sodium, potassium, and ammonium sulfates show that the concentration of sulfate ion in the presence of univalent cations can be determined from the optical density of the solution at 190 mμ. The concentrations of sulfate ion thus determined in dilute solutions of sulfuric acid are in agreement with values reported previously from Raman spectral, conductivity, and other studies, which indicate a dissociation constant K2 = 0.01 for the second stage in the ionization of sulfuric acid.

Altered Fine Structure of B Lymphocytes Correlated with Defective Terminal Differentiation

1973 ◽  
Vol 31 ◽  
pp. 386-387
Author(s):  
Dale E. Bockman ◽  
L. Y. Frank Wu ◽  
Alexander R. Lawton ◽  
Max D. Cooper
Keyword(s):  
Immune Deficiency ◽  
B Lymphocytes ◽  
Plasma Cells ◽  
Present Report ◽  
Specific Antigen ◽  
Terminal Differentiation ◽  
Second Stage ◽  
Two Stages ◽  
Deficiency Diseases ◽  
Cell Line Generation

B-lymphocytes normally synthesize small amounts of immunoglobulin, some of which is incorporated into the cell membrane where it serves as receptor of antigen. These cells, on contact with specific antigen, proliferate and differentiate to plasma cells which synthesize and secrete large quantities of immunoglobulin. The two stages of differentiation of this cell line (generation of B-lymphocytes and antigen-driven maturation to plasma cells) are clearly separable during ontogeny and in some immune deficiency diseases. The present report describes morphologic aberrations of B-lymphocytes in two diseases in which second stage differentiation is defective.

Cryomicroscopy of multiphase latices

1991 ◽  
Vol 49 ◽  
pp. 1060-1061
Author(s):  
O. L. Shaffer ◽  
M.S. El-Aasser ◽  
C. L. Zhao ◽  
M. A. Winnik ◽  
R. R. Shivers
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Freeze Fracture ◽  
Particle Morphology ◽  
Second Stage ◽  
Transmission Electron ◽  
Important Approach ◽  
Carbon Coated ◽  
Preparation Techniques

Transmission electron microscopy is an important approach to the characterization of the morphology of multiphase latices. Various sample preparation techniques have been applied to multiphase latices such as OsO4, RuO4 and CsOH stains to distinguish the polymer phases or domains. Radiation damage by an electron beam of latices imbedded in ice has also been used as a technique to study particle morphology. Further studies have been developed in the use of freeze-fracture and the effect of differential radiation damage at liquid nitrogen temperatures of the latex particles embedded in ice and not embedded.Two different series of two-stage latices were prepared with (1) a poly(methyl methacrylate) (PMMA) seed and poly(styrene) (PS) second stage; (2) a PS seed and PMMA second stage. Both series have varying amounts of second-stage monomer which was added to the seed latex semicontinuously. A drop of diluted latex was placed on a 200-mesh Formvar-carbon coated copper grid.

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