Bryan G. Reuben

Reactive solvent extraction of amino acids with cationic extractants

A mixture of amino acids (arginine, phenylalanine, alanine, glycine and aspartic acid) in solution was extracted by four acidic extractants (dinonylnaphthalenesulphonic acid (DNNSA), di(2-ethylhexyl)monothiophosphoric acid (D2EHPA(S)), di(2-ethylhexyl)phosphoric acid (D2EHPA) and Versatic 10) in toluene. The extractive capacity of the organic phase for the amino acids, using DNNSA, D2EHPA(S) and D2EHPA was found to decrease in the order arginine>phenylalanine>alanine>glycine>aspartic acid, although at low pH values phenylalanine>arginine occurred for D2EHPA(S) and D2EHPA. Separation factors derived for pairs of amino acids were in the range 2·0 (glycine–aspartic acid) to 20·1 (alanine–glycine). The extractive and loading capability of the extractants for the amino acids was found to decrease in the order DNNSA>D2EHPA(S)>D2EHPA>Versatic 10, which follows the reverse order of their respective acid dissociation constants. DNNSA was shown to be a promising extractant for the extraction and fractionation of amino acids.

Pharmaceutical chemicals in perspective

The Characteristics of the Pharmaceutical Industry. Patterns of Illness and Health Care. Pharmacological Concepts. The Production of Pharmaceuticals. Antibacterials and Antibiotics. Cardiovascular Drugs. Drugs Affecting the Central Nervous System. Antihistamines. Analgesics. Steroid Drugs. Nonsteroid Anti-Inflammatory Agents. Hypoglycemics. Anticholinergic Drugs. Antiasthma Drugs. Parkinsons Disease. Miscellaneous Drugs. Tropical Diseases. Prostaglandins. Antiviral Drugs. Anticancer Drugs. Orphan Drugs. Innovations and Issues. Appendices. Index.

Solvent extraction of bacteriocins from model solutions and fermentation broths

A novel method for the extraction and purification of bacteriocins (small peptides with antimicrobial properties) from fermentation broths is described. Model solutions of nisin were prepared from Nisaplin®, a commercial whey-based powder containing about 2.5% nisin and sold as a food preservative. These model solutions and fermentation broths from a culture of nisin-producing Lactococcus lactis subsp lactis were cross-flow filtered and stirred with toluene to obtain a white suspension in the toluene layer, which was back extracted with 10 mmol dm−3 HCl. Yields of the order of 90% for a single stage extraction were obtained followed by similar yields on back extraction. Yields dropped with decreasing pH, going through a minimum at pH 2. In larger scale experiments (11 dm3) at pH 6, a gel layer was formed which, on centrifugation and drying, gave a white solid containing about 50% nisin, the remainder being water and salt. Further process development would almost certainly bring this figure closer to the small-scale value. The phase transfer technique was also applied to solutions containing variacin and carnocin (produced by Micrococcus varians and Carnobacterium piscicola, respectively). The mechanism of bacteriocin extraction probably involves concentration of the peptides, which are surface active, at the interface until their solubility is exceeded and they form reverse submicelles, which aggregate into reverse micelles to give a gel. © 2000 Society of Chemical Industry

Pricing and Reimbursement Regulation in Europe: An Update on the Industry Perspective

Health costs, including the cost of pharmaceuticals, have been rising throughout the world for 35 years. Governments are determined to reduce public expenditure on health; pharmaceuticals are an obvious if frequently an inappropriate target. Cost containment measures include positive and negative lists, permission for more over-the-counter drugs, reference pricing and other price and profit controls, generic substitution, patient copayments, and drug budgets for general practitioners. These methods have been tried in various European countries and their experiences are reviewed. The advantages and drawbacks of the methods to patients, physicians, and the pharmaceutical industry are discussed. The question of elasticity of demand for pharmaceuticals is reviewed in an Appendix and a value varying between —0.44 and about —1.3 is obtained. The industry response to cost containment has been mixed. Some of the research-based companies have followed confrontational policies with their governments; others have tried collaborating. Companies aim at “satisficing” the market, that is, making the best profits they can consistent with not generating adverse publicity. The generics companies, which appear at first sight to profit from cost-cutting measures, are actually vulnerable to competition in generics from the research-based companies. Most companies are following policies of risk minimization and this is reflected in the large number of mergers in recent years. One change that has come about is that policy makers are collaborating internationally. The idea that multinationals can confront governments in Europe is now seen to be untrue, although it may be successful in the United States. The best prospect for pharmaceutical companies is to reach agreements with governments which enable them to flourish if they are innovative and to survive if they are not. This policy has so far been successful, and the industry seems to have emerged largely undamaged from the pressures of the early 1990s.

APPLICATION OF THE FIELD THEORETIC METHOD OF BOHM AND PINES TO THE DETERMINATION OF THE ACTIVITY COEFFICIENTS OF STRONG 1 : 1 ELECTROLYTES

Abstract A treatment based on the field theoretic formalism of Bohm and Pines is presented which produces theoretically determined activity coefficients in satisfactory agreement with experiment and those determined by computer simulation for 1 : 1 electrolytes of up to approximately molar strength.

Pricing and Reimbursement Regulation in Europe: The Industry Perspective

Health costs, including the cost of pharmaceuticals, have been rising throughout the world for 30 years. Governments are determined to reduce public expenditure on health; pharmaceuticals are an obvious, if frequently inappropriate, target. Cost containment measures include positive and negative lists, permission for more over-the-counter drugs, reference pricing and other price and profit controls, generic substitution, patient copayments, and drug budgets for general practitioners. These methods have been tried in various countries and their experiences are reviewed. The advantages and drawbacks of the methods to patients, physicians, and the pharmaceutical industry are discussed. Only the general practitioner budgets appear to have caused a sharp fall in spending on pharmaceuticals. The industry response has been mixed. Some of the research-based companies have followed confrontational policies with their governments; others have tried collaborating. Companies aim at making the best profits they can consistent with not generating adverse publicity. The generics companies, which appear at first sight to profit from cost-cutting measures, are actually vulnerable to competition in generics from the research-based companies. The change that has come about in recent years is that policy makers are collaborating internationally. The idea that multinationals can confront governments is now seen to be untrue. The best prospect for pharmaceutical companies is to reach agreements with governments which enable them to flourish if they are innovative and to survive if they are not.

Screened interactions in condensed media and statistical treatment of pH-dependent monolayer phase behaviour of long chain aliphatic amino acids

Abstract An experimental and theoretical study has been made of intermolecular interactions in monolayers of 2-aminotetradecanoic acid molecules at an air-water interface. A comparison of the interaction parameters required to fit to experiment a statistical mechanical model derived herein indicates strong screening between similarly charged ions in the interfacial region. An ‘electrostricted’ dielectric medium is an inappropriate description of the screening mechanism between ions of like charge. The free energy is minimised by the maintenance of a high degree of local screening by solvent molecules and other ions in the system.

Statistical mechanical treatment of reactive solvent extraction

Abstract A statistical mechanical lattice model of a reactive solvent extraction process involving two phase liquid-liquid ion exchange is presented. It is applied to literature data on the extraction of alipathic carboxylic acids by quaternary ammonium salts. The Helmholtz free energy of the system is constructed and minimised subject to the constraints of mass balance and electroneutrality. The equations defining the equilibrium conditions have been solved numerically for a range of interaction parameters and hence the equilibrium concentrations of the various partitioned species are obtained. These interaction parameters are compared with experiment. The intuitive notion that the extent of partition is dominated by electrostatic solute-extractant interactions is shown to neglect various other interactions that may, in some systems, be important.