Showing papers in "Chemical Society Reviews in 1993"

Interactions of metal ions with nucleotides and nucleic acids and their constituents

Abstract: Phosphate-metal ion interactions of nucleotides and polynucleotides sugar-metal ion interactions dichotomy of metal ion binding to N1 and N7 of purines general conclusions from sold state studies of nucleotide-metal ion complexes solution studies of nucleotide-metal ion complexes - isomeric equilibria stacking interactions involving nucleotides and metal ion complexes the effect of metal ions on hydrolytic reactions of nucleotides and their phosphoesters metal complexes of sulfur-containing purine derivatives mechanistic insight from kinetic studies on the interaction of model palladium (II) complexes with nucleic acid components platinum (II)-nucleobase interactions - a kinetic approach NMR studies of oligonucleotide-metal ion interactions metal ion interactions with DNA - considerations on structure, stability and effects from metal ion binding electron transfer reactions through the double helix the role of metal ions in ribozymes ternary metal-nucleic acid base-protein complexes metal responsive gene regulation and the zinc metalloregulatory model the role of iron-sulfur proteins in gene regulation current status of structure-activity relationship of platinum anticancer drugs - activation of the trans-geometry cisplatin and derived anticancer drugs - mechanism and current status of DNA binding proteins that bind to and mediate the biological activity of platinum anticancer drug-DNA adducts interactions of metallopharmaceuticals with DNA.

Polymer micelle interactions - physical organic aspects

Abstract: This review presents a summary of attempts to characterize the morphology of the complexes formed between ionic and non-ionic surfactants and water-soluble polymers. It is now generally accepted that complex formation involves the binding of micelles to the macromolecule. This binding process modifies the size and properties of the micelles and affects the Gibbs energy of the polymer. A complex combination of interaction forces provides the driving force for complexation. Criteria for polymer-micelle interaction are discussed. Particular emphasis is placed on the role of charge and structure of the surfactant headgroup and on the effect of polymers on the micellar structure and properties of cetyltrimethylammonium salts.

How do diesel-fuel ignition improvers work?

Abstract: An important descriptor of diesel fuel is its Cetane Number: this is an indicator of the time delay between injection and spontaneous ignition of fuel in a standard diesel engine running under specified conditions; the shorter the ignition delay, the higher the cetane number. Thus, those groupings of atoms within a hydrocarbon molecule that are beneficial in conferring a resistance to spontaneous ignition in a gasoline, i.e. a high octane number, are undesirable when they occur in a diesel fuel, and vice versa. The cetane number scale uses two standard compounds, cetane (n-hexadecane) defined as 100, and heptamethyl-nonane defined as 15, so that, assuming linear mixing, a 1:1 mixture would have a cetane number of 57.5, a 1:2 mixture would have one of 43.3, &c. Long-chain paraffins tend to have high cetane numbers, e.g. n-dodecane = 80, n-tridecane = 83, in addition to cetane itself = 100. On the other hand, hydrocarbons containing benzene rings tend to have very low cetane numbers, e.g. diphenyl = 21, diphenylmethane = 11 and 1,2-diphenyl-ethane = 1. Extremely low cetane numbers are also found for hydrocarbons with a benzene ring carrying short-chain substituents, e.g. xylene = –10 and m-di-iso-propyl-benzene = –12, but as the side chain becomes longer, the cetane number rises, to 26 for n-hexyl-benzene and to 50 for n-nonyl-benzene. Substances containing fused rings also exhibit very low cetane numbers, e.g. α-methyl-naphthalene = 0. A corollary is that the minimum spontaneous ignition temperatures for aromatic hydrocarbons are higher than for non-aromatics. Legislated National Standards usually require that the cetane number of commercial diesel fuel shall exceed a certain value, say 40. Most diesel engines do not perform well with fuels of cetane number below this: for