Structural classification and general principles for the design of spherical molecular hosts.

Cryptands, carcerands, polyoxometalates, and molecular capsules are cagelike hosts that complex guests through encapsulation. Following the discovery of a nanometer scale supramolecular shell-like spheroid, these and other shell-like hosts were structurally classified. Their frameworks may be catalogued according to principles of solid geometry. This has led to the identification of hosts that have not yet been synthesized or discovered (such as the cuboctahedron shown; X=O, S) and should lead to the design of additional container assemblies.

Non-covalent interactions exert extraordinary influence over conformation and properties of a well-known supramolecular building block.

At low pH, and in the presence of 4,4'-bipyridine, p-sulfonatocalix[4]arene crystallizes in the 1,3-alternate conformation rather than the expected cone conformation and exhibits remarkable stability.

Hydrogen-bonded molecular capsules are stable in polar media.

Robust, very large hydrogen-bonded capsules which are even stable in 50:50 water-acetone mixtures have been characterized both in solution and in the solid state.

Genetics and molecular biology of deafness.

With increased emphasis on early detection of hearing impairment, more babies are likely to be referred at younger ages to otolaryngologists for evaluation. With a diminution in the number of infants who have hearing impairment as a result of such factors as maternal infection, neonatal sepsis, or ototoxicity, the relative importance of detecting a genetic cause of newborn hearing impairment is likely to increase. Therefore, the otolaryngologist must become familiar with common causes of hereditary hearing impairment and the ways in which the newborn should be evaluated for hereditary hearing impairment. Advancements are rapidly being made in the ability to detect genes that cause hearing impairment, and we are now on the threshold of discovering ways to use gene therapy to prevent or treat hereditary deafness.

Hairy cell leukaemia occurring during phenytoin (diphenylhydantoin) treatment.

We describe the case of a patient who developed hairy cell leukaemia (leukaemic reticuloendotheliosis) during phenytoin treatment. Hairy cells were identified by fluorescence, phase contrast and electron microscopy; they contained tartrate-resistant acid phosphatase activity, formed rosettes with mouse but not sheep erythrocytes and bore monoclonal surface immunoglobulin. Because of the association of pseudo- and true lymphomas with phenytoin it is possible that this lymphoproliferative disorder arose as a result of the treatment with phenytoin, possibly in conjunction with sulthiame.

Cimetidine: interaction with oral anticoagulants in man.

In 6 patients anticoagulated with warfarin, nicoumalone, or phenindione the addition of cimetidine prolonged the prothrombin-time (PT) by a mean of 12.6 s (range 5--23 s). In 7 volunteers taking daily subtherapeutic doses of warfarin the addition of cimetidine increased the PT from 19.4 to 22.9 s and the plasma-warfarin concentration from 0.96 to 1.76 microgram/ml. Cimetidine reduced the single-dose clearance of warfarin and antipyrine. The basis of the interaction between cimetidine and oral anticoagulants is probably inhibition of drug metabolism. Care should be exercised in concomitant therapy.

The substrate specificity of Saccharomyces cerevisiae myristoyl-CoA:protein N-myristoyltransferase. Analysis of myristic acid analogs containing oxygen, sulfur, double bonds, triple bonds, and/or an aromatic residue.

We have explored the acyl-CoA substrate specificity of Saccharomyces cerevisiae myristoyl-CoA:protein N-myristoyltransferase (NMT) by synthesizing 81 fatty acid analogs and surveying their activity in a coupled in vitro assay containing Pseudomonas acyl-CoA synthetase and Escherichia coli-derived yeast NMT. Single oxygen or sulfur substitution for C-3 through C-13 is well tolerated by both enzymes. Detailed kinetic analyses suggest that the acyl-CoA and peptide-binding sites of NMT are relatively insensitive to placement of single group 6B heteroatoms. By contrast, di-oxygen-substituted analogs were very poor substrates, producing dramatic reductions in the affinity of NMTs peptide-binding site for a synthetic octapeptide substrate derived from the NH2-terminal sequence of a known N-myristoylprotein, the gag poly-protein precursor of human immunodeficiency virus 1 (HIV-1). This observation provides an example of binding site cooperativity in NMT. Replacement of one oxygen with sulfur at either the 6, 9, or 12 position of dioxatetradecanoic acids results in a general increase in peptide catalytic efficiency (Vmax/Km). An analysis of five fatty acids from octanoic to dodecanoic having terminal phenyl groups indicated that the best substrate was 10-phenyldecanoic acid even though Corey-Pauling-Koltun molecular models indicate that it has a length equivalent to that of tridecanoic acid. Six analogs having an equivalent length of 13 carbon atoms were subsequently prepared in which the phenyl group was systematically moved one methylene group closer to carboxyl. Movement of the phenyl just one carbon closer to carboxyl (producing 9-(p-methylphenyl) nonanoic acid) decreases peptide catalytic efficiency (Vmax/Km) severalfold compared to 10-phenyldecanoic acid. 10-(4-Tolyl)decanoic acid has the same relative positions of phenyl and carboxyl as 10-phenyldecanoic acid even though a methyl group is present on the phenyl ring. It produces peptide Km and Vmax values that are the same as 10-phenyldecanoic acid. Substitution of either oxygen or sulfur for a methylene group fails to override the effects noted when the phenyl group position is altered in the C-14 equivalent fatty acid series. Several fatty acids of differing chain lengths with cyclohexyl-, 2-furyl, and 2-thienyl groups at their omega termnius had activity profiles that paralleled those of the comparable phenyl-substituted compounds. Myristic acid analogs with triple bonds (beginning at positions 2 through 13), cis-double bonds (positions 3 through 13) and trans-double bond isomers (E5, E6, and E7) were also tested.(ABSTRACT TRUNCATED AT 400 WORDS)