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The different size and site preferences of Mg and Zn in newly synthesized structural phases of Ae[M.sub.x][In.sub.4-x] (Ae = Sr, Ba; M = Mg, Zn) with Ba[Al.sub.4]-type features is discussed.

The synthesis and structural characterization of [Ca.sub.4][Au.sub.10][In.sub.3], the first ternary derivatives of the [Zr.sub.7][Ni.sub.10] structure is described. The structure exhibits a complex [[Au.sub.10][In.sub.3]] polyanion framework containing remarkable sinusoidal Au layers.

The solid-state reactions in welded Ta tubes at high temperature were used to synthesize the [M.sub.2]B[a.sub.2]S[n.sub.6] (M = Yb, Ca) compound. The electronic structures calculated indicate that the compounds are metallic with a deep pseudogap at the Fermi level.

The production of the ternary polar intermetallic phase [Mg.sub.5.231(8)][Sm.sub.0.231(8)][Sb.sub.4] from solid state reactions at 700-850 degrees Celsius in sealed Ta or Nb containers when the synthetic conditions took into account its characteristic incongruent melting point is reported. The results present the first example of a superstructure of a[Mg.sub.3][Sb.sub.2]-like structure with a doubled c axis induced by ordering a mixture of the larger divalent Sm and Mg ions separately within alternate layers of octahedral sites.

Three new compounds in the ternary Ba-(An,Hg)-(In,TI) systems are reported that are isostructural with orthorhombic CeCu2, a lower-symmetry relative of the CaIn2 type. The relativistic effects for the heavier Au and Hg are responsible for decreases in lattice parameters and bond lengths from BaIn2 to those in isostructural BaAu(sub 0.36)(4)In(sub 1.64)(4) and BaHg(sub 0.82)(2)In(sub 1.08)(2).

The phases LiMgCa(sub 10)Sb(sub 9), Mg(sub 2)Ca(sub 10)Sb(sub 9), and Li(sub 1.38(2))Sb(sub 9) are synthesized by high-temperature solid-state means and characterized by single-crystal means and property measurements. The LiMgCa(sub 10)Sb(sub 9) compound is correspondingly diamagnetic and presumably a semiconductor.

The syntheses, structural characterizations, and the electronic structure of and chemical bonding within the new phase region is reported. The structure shows substantial differences from related A(sub 15)Tl(sub 27) (A = Rb, Cs) in which the cation A that centers a six-membered ring of Tl(sub 11) fragments is replaced by M(sub 3).

Chemisorption of a methanol molecule onto a size-selected copper cluster ion, Cu(sub n)(super +(n=2-10) and subsequent reactions were investigated in a gas-beam geometry at a collision energy less than 2 eV in an apparatus based on a tandem-type mass spectrometer. The origin of the size-dependent reactivity was explained as the structural change of cluster, two-dimensional to three-dimensional structures.

The reaction of elemental In, Pb, or K, or Rb within welded Ta containers at 900 degree Celcius followed by subsequent annealing at 35 degree Celcius gives the new phases A(sub5)InPb(sub)8 (A = K, Rb). Wades rules for counting bonding electron states in a given class of clusters indicate that the charge assigned to an ideal deltahedral tetral cluster is independent of its nuclearity.

The ratio of Cu and Ga are changed to acquire four electrons in order to tune the primitive composition of the ternary Mg2Cu6Ga5 phase to a quasicrystalline approximant. However, these efforts produce the Mg35Cu24Ga53 compound consisting of a three-dimensional cubic network, whose synthesis, structure and bonding analysis are presented.

Structural stabilization among the three compounds namely K34In92.30Li2.70, K14Na20In91.82Li13.18 and K14Na20In96.30 reveals an intimate relationship between structure and valence electron requirements. The electronic tuning within the complicated network structure is realized by substitution of part of the iridium by electron-poorer lithium atoms.

Mutant Escherichia coli aspartate aminotransferases (eAATases) are characterized to redesign the substrate specificity of eAATase into that of Escherichia coli tyrosine aminotransferase. Details regarding the determination of the high-resolution crystal structures of ligand complexes of HEX + A293D, SRHEPT (eAATase with seven substitutions), and SRHEPT + A239D are explained.

The synthesis, structure and bonding of the nonclassical Zintl phase K5As3Pb3 are described. It is shown that the nonclassical bonding is encountered most often in more electron-deficient cluster systems, particularly with triel (group 13) members.

The bcc structure contains the multiply endohedral cluster polyhedra shown around each lattice point, the last two shells being shared with like neighbors. Atom site preferences parallel the greater electronegativity of Cd over Tl.

Results describe the syntheses of the quaternary lanthanide halide cluster compounds containing transition metal interstitials and alkali or alkaline-earth metal ions using high temperature solid state techniques. The compounds exhibit rhombohedral structure and semiconductor activity.

The first total syntheses of (+)-zampanolide and (+)-dactylolide, members of a new class of tumor cell growth inhibitory macrolides, are achieved. Key features of the unified synthetic scheme included the stereocontrolled construction of the cis-2,6-disubstituted tetrahydropyran through a modified Petasis-Ferrier rearrangement, a highly convergent assembly of the macrocyclic domain, and, in the case of zampanolide, a Curtius rearrangement/acylation tactic to install the N-acyl hemiaminal.

Research has been conducted on KNa (sub)3 In (sub)9. The results of the single-crystal X-ray diffraction analysis demonstrate that this compound crystallizes in the orthorhombic system which contains indium network constructed of empty indium icosahedra layers.

Research examines the insertion of a palladium atom into a known triel element cluster leading to the formation of palladium-centered thallium clusters. Data indicate that in such clustering process the atom and orbital sizes of the two components as well as the anionic characteristics of thallium appear to be important.

The study presents a new method to identify enzyme inhibitors, which conducts synthesis of the targeted enzyme. This means that a screening method that enhances the ability to detect the best inhibitor is proposed and the key to the method is an irreversible destruction reaction, which destroys weak inhibitors.

Research has been conducted on the heterometallic compounds from the orthorhombic family. The synthesis and structures of these compounds have been carried out and their electronic structures have been investigated and are discussed.

Research has been conducted on the trans-2,3-piperidinedicarboxylic and trans-3,4-piperidinedicarboxylic acids and their N-Boc and N-Cbz protected analogues. The asymmetric synthesis of these compounds is reported.

The synthesis and characterization of the new BaTi3 compound is done by physical property measurements and electronic structure calculations. The unique geometric features of the anionic thallium layers gives rise to unusual competition between inter and intracluster bonds.

Research has been conducted on the compounds containing square pyramidal tin and lead Tt (sub)5 polyanions. Results indicate that these compounds have been obtained via the direct fusion of the alkaline-earth or rare-earth metal-tetrel systems followed by slow cooling.

Research has been conducted on the formation of K (sub)2 SrIn (sub)7. The direct fusion of the neat elements in a niobium tube has been investigated, and the results of the single-crystal X-ray diffraction analysis revealing that K (sub)2 SrIn (sub)7 crystallizes in the orthorhombic system are presented.

Apratoxin A is considered as a potent novel cytotoxin from the marine cyanobacterium Lyngbya majuscula and its structure is discussed.

Research has been conducted on the K (sub)6 Tl (sub)2 Sb (sub)3 with the heteroatomic anionic chains discovered in the K-Tl-Sb system. The results indicate that the active metal-thallium-pnictide compound exhibits Tl-Tl bonding.

Open-shell Sr3In5 was synthesized and characterized and an unusual electron deficiency beyond the Zintl boundary was observed.

A series of isostructural compounds R5Ga3 (R = Sc, Y, Ho, Er, Tm, Lu) are shown to have a new distorted version of the familiar Mn5Si3 structure type. The electronic calculations reveal that the distortion and formation of Ga2 anions allows a significant displacement of antibonding dimer levels above E(sub F) and an appreciable lowering of Ga-Ga and Ga-Sc states just below E(sub F).

The most egregious of the errors committed or possible for Cr5B3-like phases, those that are uniquely stabilized by hydride (or fluoride) are reported. The new ternary phases are generally Pauli-paramagnetic, evidently with pi electrons from the characteristic tetrelide dimers in this structure type at least partially delocalized into the conduction band and the Sn-Sn bonds appear correspondingly shortened on oxidation.

The synthesis and characterization of centered cluster halides and tellurides of the earliest transition metals is summarized. It also looks into the broad interstitial chemistry of the widespread group of metallic transition-metal phases with a Mn5Si3 type structure.

Research shows that the metal-metal bonding in the transition metal chalcogenides is facilitated by the crystallization of these compounds in the Fe(sub)2P structure type called Zr(sub)6CoAl(sub)2. Results demonstrate that the chalcogenides containing metal substituents exhibit structural and electronic flexibility and the metal-metal bonding is one dimensional in character.

A statistical report on the amount of emissions produced in United States waters in 1997 by commercial shipping vessels.

The basic building blocks in these novel anionic chains are the pentagonal antiprisms centered by Cd. Band calculations and resistivity and magnetic susceptibility measurements clarify the unusual architecture and properties. Additional four-bonded Tl atoms on one side of the chain make the structure acentric.

Research has been conducted on the K (sub)10 Tl (sub)7. The synthesis of the compound by direct fusion of the elements has been carried out.

Sc(sub9)Te(sub2) structure was investigated, comprising distorted columns of scandium metal and a corrugated layer of tellurium atoms, separating rumpled metal layers.

Research has been conducted on the biosynthesis of the nonadride CP-225,917. Experiments include the dimerization of the C (sub)16 anhydride from the lauric and oxaloacetic acids condensation.

The authors discuss the reactions in the La-Br-Z system where Z=Fe, Ru and Os metal atoms. Results demonstrate that only Os has led to the characterization of La (sub)48 Br (sub)81 Os (sub)8 phase.

A new compound containing the isolated gallium clusters Ga10Ni10- was revealed through the exploration of the sodium-gallium-nickel system. The single-crystal X-ray diffraction studies of Na10Ga10Ni demonstrate that it is isostructural with K10In10Ni. A strong tendency to form extended structures was observed which makes the formation of isolated Ga10Ni10- units in Na10Ga10Ni an even more interesting result.

Research was conducted to examine a novel network design which provides what appears to be an ideal connectivity for intercluster electron delocalization. The syntheses of alpha-K4R6I14Os (R = La, Pr), with their unusual cluster connectivities and all the delocalization implications thereof, clearly show how the introduction of alkali metals can lead to the formation of more open and less bridged structures. The 2D band calculations clearly shows the increased dispersion and delocalization that can be derived in the 2D-planar net of iodine-bridged clusters, which was the first unexpected feature of the new cluster structure.

The synthesis of a new compound which is a nominal polymorph of the novel tetragonal (alpha-)K4-La6I14Os, in which undistorted octahedral La6(Os)I(super i)(sub 10) units are interbridged by I(super i-a)(sub 4/2) into a new planar network, is reported. The synthesis emphasizes the possibility of new structures that can be produced by subtle variations in such quaternary systems.

The structure of Sc(sub 5)Ni(sub 2)Te(sub 2) prepared by high-temperature solid-state techniques was investigated. The structure contained pairs of eclipsed zigzag chains of nickel atoms that were coated by scandium atoms and demarcated from other chains by tellurium atoms. The structure was isotypic with that of Hf5Co(sub 1+x)P(sub 3-x) but shifted atomic positions and a different ordering of the main group and late transition elements gave it a clearly one-dimensional character.