The adsorption of cephalexin.H2O from aqueous solution on attapulgite, bentonite and kaolin has been studied at the human body temperature (37.5˚C) and at 5, 27, 47˚C in 0.1M hydrochloric acid (pH 1.2). The value of pH 1.2 has been chosen to simulate the pH of stomach fluid. The clays show the following order: Bentonite > attapulgite > kaolin, for their activity to adsorb cephalexin.H2O. The charged clay particles can attract molecules either by electrostatic forces, for the molecules of oppositely charged, or by inducing dipole formation in the neutral molecule. The L-shaped adsorption isotherm indicated that drug molecules arrangement in a flat geometry on the clay surface. The results indicated the applicability of Langmuir isotherm for adsorption of drug on three clays. The amount of cephalexin.H2O adsorbed on the three clays was increased with increasing pH value from 1.2 to 5. At the acidic pH, the competition between cephalexin.H2O molecules and hydronium ions results in a reduction in adsorption process. At fixed temperature and pH, the adsorption of cephalexin.H2O on the three clays was increased with increasing the ionic strength of solution. The data showed a little increase in the amount of drug adsorbed by attapulgite and bentonite with increasing temperature, so the adsorption process appeared endothermic. The reverse was observed with adsorption of cephalexin.H2O on kaolin surface (exothermic).The extent of desorption of cephalexin.H2O from the clays increased when the concentration of drug increased. This result may refer to the difficulty of desorption of the drug at low concentrations, which reflects a relatively higher adsorbate - adsorbent interaction.
INTRODUCTION Erythrocyte membrane, like all other eukaryotic plasma membranes, is composed of a bilayer of several different classes of lipid along with a variety of protein molecules [1]. It contains 52 % proteins, 40 % lipids and 8 % carbohydrates that is bound to lipids (glycolipids) or proteins (glycoproteins) [2]. The lipids form a rather continuous bilayer in which the outer layer contains mainly phosphatidylcholine and sphingomyelin, and the inner one, phosphatidylethanolamine and phosphatidylserine. Lipids provide mechanical stability and a strong tendency to form closed structures [3]. Membrane proteins are classified as peripheral or integral. Peripheral proteins are molecules that are bound to membrane primarily through interactions with integral membrane proteins. The integral proteins represent more than 70 % of membrane proteins and are very firmly associated with the membrane, the two major integral proteins are band and
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