Influence of the self-association of oleandomycin on its extraction from aqueous solutions

1984 ◽  
Vol 18 (9) ◽  
pp. 643-648
Author(s):  
E. V. Komarov ◽  
L. G. Kardo-Sysoeva ◽  
V. P. Mikhailova
Keyword(s):  
Aqueous Solutions ◽  
The Self ◽  
Self Association

Self-Association and Crystallization of Amylose

2007 ◽  
Vol 60 (10) ◽  
pp. 706 ◽  
Author(s):  
Alain Buléon ◽  
Gabrielle Véronèse ◽  
Jean-Luc Putaux
Keyword(s):  
Aqueous Solutions ◽  
Enzymatic Synthesis ◽  
Structural Changes ◽  
The Self ◽  
Model Systems ◽  
Starch Granules ◽  
In Vitro Synthesis ◽  
Self Association ◽  
Lamellar Crystals

Amylose, the linear constituent of starch, consists of α(1,4)-linked glucose monomers. Although weakly involved in the crystalline structure of starch, it can be recrystallized in a variety of allomorphic types, including those encountered in native starch (A- and B-types). Amylose can either be extracted from starch or produced in vitro by enzymatic synthesis using amylosucrase or phosphorylase. Recrystallization and self-association of amylose in aqueous solutions have been widely studied to understand both the crystallization of starch during biosynthesis and the structural changes that occur during starch processing. Depending on the chain length, concentration, and temperature, gels, spherulites, or lamellar crystals can be formed with A or B allomorphic type. Other ligand-dependent allomorphs (the various V-types) are obtained when amylose is complexed with molecules such as alcohols, lipids, or flavours. Amylose also self-associates into networks, spherulites, or axialites during in-vitro enzymatic synthesis by amylosucrase. When a highly branched acceptor like glycogen is used, dendritic nanoparticles are formed by elongation of the external chains. The recrystallization of amylose extracted from starch and the self-association of amylose during its in-vitro synthesis are described. The amylose properties are discussed in terms of polymer behaviour and model systems to investigate the structure and formation of starch granules.

Self-Association of the Macromolecules of Aldrich Humic Acid in Aqueous Solutions Using Ultraviolet–Visible (UV–Vis) Absorption Spectroscopy

2019 ◽  
Vol 73 (7) ◽  
pp. 810-815
Author(s):  
Nikolay L. Lavrik ◽  
Nikolay M. Bazhin
Keyword(s):  
Aqueous Solutions ◽  
Absorption Spectroscopy ◽  
Spectral Dependence ◽  
The Self ◽  
Dimerization Constant ◽  
Absorption Bands ◽  
Characteristic Absorption ◽  
Mathematical Algorithm ◽  
The Difference ◽  
Self Association

The ultraviolet–visible (UV–Vis) spectra of the aqueous solutions of humic acids (HA) Aldrich were obtained within the concentration range 1–20 mg/L (0.1–2ċ10–6 mol/L). A conclusion on the existence of the self-association (dimer formation) of HA macromolecules is based on the deviation of the concentration dependence of optical density (OD) from the linear one at [HA] > 10 mg/L (>10–6 mol/L). An original, mathematical algorithm is proposed to determine a dimerization constant K and a molar coefficient of dimer absorption [Formula: see text] The value of K was (2.56 ± 0.07) ċ 106 L/mol. The calculated molar coefficients of HA macromolecule dimer absorption, [Formula: see text], indicate an increase in the dimer extinction coefficient [Formula: see text] compared to the double value of the molar monomer absorption 2[Formula: see text]. It was established that the spectral dependence of the value β = [Formula: see text]/[Formula: see text] exhibits a minimum within a wavelength range of 300–450 nm, which is due to the difference in the efficiency of the interaction of various sites upon HA macromolecule dimerization. Thus, an approach of studying the processes of self-association is proposed using the method of UV–Vis absorption spectroscopy. This method is implemented for molecules that do not have characteristic absorption bands. The proposed method can also be successfully applied to molecules with characteristic absorption bands.

Sign in / Sign up

Export Citation Format

Share Document