Demineralization in organic solvents by alkylammonium salts of ethylenediaminetetra-acetic acid.

1. Insoluble salts of alklaine earth metals (e. g. calcium phosphate) dissolve in non-aqueous solvents containing EDTA salts of organic cations (e.g. tetraethylammonium). 2. Bone is efficiently demineralized in ethanolic trimethylammonium EDTA. Retention in the matrix of water-soluble materials (e.g. proteoglycan) is much better than in standard aqueous EDTA demineralization procedures.     

Fourth 3D structure of the chitosan molecule: conformation of chitosan in its salts with medical organic acids having a phenyl group

Chitosan salts with two medical organic acids having phenyl groups (salicylic and gentisic acids) exhibited fiber diffraction patterns of a new type of crystal which does not compare with known types I and II. The crystals, called type III salts, showed a fiber repeat of 2.550 nm and a meridional reflection at the 5th layer line. These results coupled with a conformational analysis indicate the chain conformation of chitosan with the salts to be a 5/3 helix, this helix differing from those of type I (an extended two-fold helix) and type II (a relaxed two-fold helix or a 4/1 helix). The fiber patterns of all the type III salts were similar. This observation has also been found with type II salts and is an indication that the acid ions are not arranged in regular positions in the crystals. A comparison of solid-state 13C-NMR spectra of the gentisic acid salt and the aspirin salt, which could not be crystallized, suggests that, in the latter salt, the chitosan molecules also formed a 5/3 helix.     

Effect of salts on D-glycerate dehydrogenase kinetic behavior.

Bovine liver D-glycerate dehydrogenase (D-glycerate:NAD (NADP) oxidoreductase, EC 1.1.1.29) adapts its kinetic behaviour to a sequential mechanism. The presence of NaCl causes an appreciable variation in the Km and V values. relative to the both substrates in the hydroxypyruvate/D-glycerate dehydrogenase/NADH system, which does not happen in the D-glycerate/D-glycerate dehydrogenase/NAD system. The former system is inhibited by high concentrations of NaCl and activated by low salt concentrations. The hydroxypyruvate concentration causing substrate inhibition increases as the concentration of NaCl increases; excess NADH inhibition is independent of the salt concentration. The variation of the initial rates of both systems, in the presence of chlorides having monovalent and divalent cations, or sodium halides, Na2SO4 and NaNO3 (at constant ionic strength) suggests that the anions have a specific action on the enzyme. An increase in the NaCl concentration causes a displacement of the optimum D-glycerate dehydrogenase pH (with hydroxypyruvate and NADH as substrates) towards the acid area. The enzyme stability, at varying pH, varies with the salt concentration.     

Two different molecular conformations found in chitosan type II salts

The type II structure of chitosan acidic salts prepared from crab tendon in solid state was studied using an X-ray fiber diffraction technique together with the linked-atom least-squares (LALS) technique. The cylindrical Patterson method was applied to confirm the molecular conformation of the chitosan. It was shown that there are two different helical conformations for type II salts. One is the relaxed twofold helix having a tetrasaccharide as an asymmetric unit as found in chitosan.HCl salt, which was previously reported as a conformation of chitosan.HCOOH salt. The other is the fourfold helix having a disaccharide as an asymmetric unit newly found in chitosan.HI salt.     

Enhancement of local anaesthesia action by organic acid salts. (I): Possible change of excitability in nerve fibre membrane

Measurements of action potentials recorded from giant nerve fibres of the crayfish abdomen showed that by addition of an organic acid salt to a local anaesthetic solution, the onset of anaesthetic action became more rapid and the duration of action was prolonged. Similar results were also obtained in rat vagal nerves. The chemical structure of compounds having these enhancing effects was found to have, in common, a carboxyl group connected with either a benzene ring or an aliphatic hydrocarbon. Topical application of anaesthetic solutions to the skin of flexor side of the forearm in humans revealed that the duration of anaesthesia evaluated by the apparent decrease of the number of pain points was significantly prolonged by the addition of salicylate. The use of local anaesthetics combined with organic acid salts would be promising in clinical practice to enhance their action greatly.     

Hydrolysis of chitosan in lactic acid

Effects of molecular weight and degree of acetylation on the hydrolysis of chitosan in dilute lactic acid were studied. It was demonstrated that the higher were the values of both parameters, the more rapid were the decreases in viscosity and viscosity-average molecular weight of chitosan.