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Results reveal that some polymers display pi-aggregates resembling edge-on-structure at the air-water interface, while monolayer Langmuir-Blodgett films of the polymers show a reduction in the quantum yields. Polymers that do not form pi-aggregates exhibit a highly emissive face-on-structure at the air-water interface.

Research demonstrates the antimicrobial activity of the 12-helical beta-peptides. Data indicate a 40% cationic face is optimum for their activity and those with higher cationic face are inactive. The mechanism of action of beta-peptides is similar to those of antimicrobial alpha-peptides and they are impervious to proteases.

Nuclear magnetic resonance analysis reveal that 11-cis-locked cyclopropyl retinal adopts a twist chair conformation, involving the seven-membered ring, in solution. Data indicate that the compound exists as two diastereomeric populations. The native retinal does not exhibit twist preference around C6/C7 bond.

The relationship between the geometric and electronic structures of the yellow and pink low-temperature azide adducts of iron(III) superoxide dismutase is presented. Data indicate that alterations in the H-bond network leads to marked spectral changes correlated with perturbations in Fe-N(sub)3 bonding. Further, a second coordination sphere aids in the catalytic reactions.

Results describe the synthesis and characterization of cocaine benzoylthio ester. Data show the compound is optically pure, possesses correct stereochemistry at carbon-3, and reacts with catalytic monoclonal antibodies.

This article describes the nature and function of deoxyribozymes behaving as molecular scale logic gates. Research describes one set of logic gates, NOT and AND gates. Data suggest that these oligonucleotide-based multifunctional molecular platforms consist of an input and an output whose detection is measured by means of fluorescence measurement.

This article examines the enthalpy-entropy compensation in RNA with reference to hydration- and folding thermodynamics. Results indicate that the macromolecule structure limits the range of adoptable states for hydration molecules in the folded state leading to a favorable net enthalpy changes.

Results reveal that among the internal single-mismatches in A-RNA, only the A-C variants are stabilized by protonation at pH 5.5 with accompanying exothermicity. Data suggest that the folding stability is governed by deltaG and transition state and the extent and strength of solvation of the folded structures reflect deltaH and entropic penalty T.deltaS.

A self-assembling molecular capsule that exhibit electrostatic interaction was developed and analyzed via 1H nuclear magnetic resonance (NMR) spectroscopy. The hydrodynamic characterization derived from relaxation experiments suggested that the association between positively and negatively charged hydrophilic beta-cyclodextrin derivatives in 50 millimolar KCl aqueous solution was due to dimerization. The results showed that the NMR dynamic approach to studying self-assembled arrays is effective in obtaining viable information regarding the mean structure of associated species.

An investigation of how variation in the features of tri-bipyridine ligands or in the iron(II) salt affects the self-assembly of inorganic architectures found that the use of a different iron(II) salt produces a hexanuclear double helicate while a modification of ligand structure results in a tetranuclear double helicate. Data indicate two levels of self-assembly. One level is the organization of the ligands around metal ions; the other is a ring closure into a defined torus. Structural features in the ligand and substrate binding effects combine to produce a specific architecture.

Nuclear magnetic resonance and infrared spectroscopy of a combinatorial library of Beta-sheets consisting of two amino acid groups attached to a diamine backbone by two urea groups found that parallel Beta-sheet forming propensities are similar to that of antiparallel Beta-sheet. The model system prepared for the study allows multiple comparisons as well as the juxtaposition of two peptide groups without requiring long peptide segments. More sophisticated combinatorial methods will be needed for preparing and studying larger libraries.

An examination of the reactions of 1,1,3,3-tetramethylbutyl (tert-octyl) peroxypivalate with methyl methacrylate (MMA) and styrene found that both monomer systems produced alkoxamines derived from radicals. Alkyl radicals are formed by Beta-scission and intramolecular hydrogen abstraction and undergo addition/trapping in a manner analogous to tert-butyl radicals. Results indicate that steric effects caused the low rate of the 1,5-H shift in tert-octyloxyl radicals.

Use of van't Hoff method in the reevaluation of the enthalpy of conjugative interaction in styrene found that a single value is not sufficient for more sophisticated conjugative interaction systems. Results indicate that entropies can adversely affect the equilibrium position of conjugated isomers. Thermochemical data suggest that molecular mechanical programs cannot be used in predicting the equilibrium of the interplay between nonbonded steric interaction and its attenuation of pi-electron delocalization.

Synthesis of the first sulfur- and selenium-bridged [1]ferrocenophanes showed that these species have tilt angles of 31 degrees and 26 degrees respectively. Evidence for the high degree of ring strain was further provided by nuclear magnetic resonance chemical shifts of the ipso-carbon atoms in the [1]chalcogenaferrocenophanes. Data indicate that ring-opening polymerization reactions are less efficient in the formation of poly(ferrocenyl chalcogenides). Detailed studies of physical properties will be made when higher molecular weight samples of become available.

Modification of a one-step synthesis of 7,10-disubstituted fluoranthene through successive pyrolysis and bromination led to the 7,10-bis(1-chlorovinyl)fluoranthene precursor which enables producing 250-300mg samples of corannulene in a single pyrolysis run. This precursor can be produced just two steps away from commercially available starting materials. Results indicate that the first steps in the conversion of this precursor to corannulene involve thermal loss of two hydrogen chloride molecules to generate diyne 7,10-diethylfluoranthene.

Quantum chemical studies were carried out to determine the mechanism of diiron methane monooxygenase (MMO)-mediated C-H activation. The results revealed that the C-H activation proceeds via the reaction of the Fe2(II,II) dinuclear iron site of the reduced form of MMO with O2 to give two different Fe2(III,III) peroxo species. O-O bond cleavage then follows which yields an Fe2(IV,IV) bis-mu-oxo species that are thought to be analogous to 'compound Q' of MMO. The ensuing Jahn-Teller distortions lead to the formation of Fe(super III)-O-Fe (super IV)-O*. radical which causes the abstraction of a hydrogen from methane.

X-ray crystallography, supplemented with nuclear magnetic resonance and UV-visible spectroscopic studies were done to investigate the structure-reactivity relationship in interlocked molecular compounds. Such compounds were represented in the experiment as the product of interactions between hydroquinone-based compounds carrying polyether/polyester functions and the bipyridinium units of the cyclobis(paraquat-p-phenylene). There was an increased reactivity of the ester functions consequent to such reaction and this could be attributed to the hydrogen bonding interactions involving the ester carbonyl oxygen atoms and the acidic hydrogen atoms on the bipyridinium units.

A group of luminescent lanthanide complexes based on linear and macrocycle polyaminocarboxylate chelates that are covalently joined to the organic sensitizer carbostyril 124 are synthesized and spectrally characterized. The results show that the sensitizer does not cause nonradiative de-excitation and that their lanthanide emission quantum yield is close to unity. In addition, the macrocycle cheletes are the most efficient synthesized energy transfer donors as they cause two-color detection without spectral overlaps in a single excitation wavelength and can recognize autofluorescence.

Structural analysis shows that the active-site lysine residue (Lys41) interacts preferentially with the transition state for covalent bond cleavage and helps to activate catalysis. The bovine pancreatic ribonuclease A is seen to catalyze the P-O(super 5') bonds in RNA. Side chains donating a second hydrogen bond gain no significant catalytic advantage, thus revealing that during the catalysis, residue 41 donates a single hydrogen bond to the rate-limiting transition state.

The catalytic antibodies created against a single transition state analog exhibit high homology in the structural and biochemical properties. The haptens are attracted to the transition state stabilization and are identical to the transition state for obtaining the catalytic antibodies. The biochemical properties of six anti-haptenic phosphonate catalytic antibodies are studied to detect active site structure. The catalytic antibodies having highly homologous primary amino acid sequences contain homogeneous binding modes to the substrate or hapten.

Molecular design and chemical synthesis of many palmerolide A analogues have allowed the first structure activity relationships (SARs) of the newly discovered marine antitumor agent. The studies have helped in the design and synthesis of much more potent and selective palmerolide A analogues as biological tools and drug candidates.

The molecular basis of the NO detoxification mechanism is examined using a combination of classical and hybrid quantum-classical (QM-MM) simulation techniques. The structural flexibility of the protein, the ligand affinity properties, and the nitric oxide reaction with coordinated oxygen are also investigated.

The synthesis of novel poly(phenyleneethynylene) derivatives with polar cationic and nonpolar alkyl groups is presented. The amphiphilic polymers exhibit extended conformation as shown by Langmuir and emission studies. The polymers are membrane active as well..

Research demonstrates small molecules behaving as 'chaperones' in the spontaneous assembly of synthetic noncovalent structures, the absence of which leading to the formation of nondefined structures that are unable to rearrange to give assembly of structures.

More than two million compounds having structures that are identical to natural products and consistent with miniaturized assays were synthesized via a six-step reaction sequence. The technique involved a number of coupling processes and split-pool methodologies to produce multiple products. Moreover, it required water-compatible photolabile supports when implementing large numbers of miniaturized cell culture assays targeted at isolating cell permeable ligands. The resulting compounds were structurally diverse, stereochemically defined and rigid.

Homologous gamma-peptides were synthesized via peptide coupling and chain extension and examined by two-dimensional-nuclear magnetic resonance spectroscopy. The findings showed that the resulting peptides had stable right-handed helical secondary structures in organic solvents. Moreover, the alpha-substitution in the peptides resulted in more stable helical structures if the configuration of the alpha-group is consistent with the main peptide backbone.

Predominantly nonaqueous soft chemical methods were used to transform germanium oxide into Ge7O14.5F2*{(CH3)2NH2}3(H2O)0.86. The structure was established from Ge7 cluster units attached into a three-dimensional porous net containing intersecting channels in which water and (CH3)2NH2+ (DMA+) guests are located. Results showed that the reversible exchange of DMA+ for Na+ maintains the periodicity and integrity of the germanate open framework structure.

Ab initio computations implemented on pyrrole were compared to those performed on benzene to elucidate the interaction of tetramethylammonium (TMA) ions with the cycles of aromatic amino acids. The structures were found to be similar for indole, pyrrole and benzene, with minor distortions in the parallel planes of the three hydrogens of TMA. The high affinity of indole for TMA accounts for a substantial fraction of MP2 correlation energy, while the large distortion of phenol from parallelism does not favor correlation.

A wide range of N-t-BOC-protected glycine functionalized dendrimers were synthesized by reacting the N-hydroxy succinimidyl ester of N-t-BOC glycine with poly(propylene imine) amines and characterized via nuclear magnetic resonance and infrared spectroscopy. The X-ray structure of the dendrimers exhibited multiple interactions between various end groups of the dendrimer. The findings provided strong evidence that the localization of end groups as well as the density profiles in dendrimers are a function of the structure of the dendrimer.

Mass spectrometry and nuclear magnetic resonance spectroscopy was done to characterize a newly synthesized endohedral simple enol. The results revealed that the capsule cage of the lantern-shaped molecule can provide a unique reaction environment for the endohedral functionality due to the separation of its interior from the bulk phase. The lantern-shaped framework was also observed to be a useful structure for efficient stabilization of highly reactive species such as a monounsubstituted simple enol.

Expression of DEBS1 containing the first two modules of a polyketide synthase (PKS) 6-deoxyerythronolide, in Streptomyces coelicolor catalyzes the biosynthesis of a triketide lactone. This catalytic biosynthesis indicates that a bimodular polypeptide is sufficient for this catalysis. These two modules are independent of the remaining part of the PKS and may even be a single module. The presence of such single modules as functional units enables formation of polyketides of desired lengths.

Molecular modeling studies and structure-activity relations enable the structure-based design of a series of chiral, low molecular weight and potent nonpeptide HIV PR inhibitors. These inhibitors have a structural scaffold relating to other peptidomimetics. Conformational stability and replacement of water molecules in the active site explain the potential of these compounds.

A study conducted detailed investigations on the electronic structure of the deoxyhemerythrin and oxyhemerythrin non-heme metalloproteins. Significant insight was obtained into the key geometric features of the electronic structure of oxyhemerythrin. The bonding descriptions of deoxyhemerythrin and oxyhemerythrin provided the foundation for developed a detailed understanding of the fascinating reaction of O2 binding to hemerythrin. Experimental methods and results are presented.

Molecular dynamics simulations of thermal denaturation of wild-type and two mutant forms of barnase are employed in the comparison of the phi-value analysis of the folding/unfolding pathway of barnase with an explicit structural analysis of the transition state. Results of experiment and simulation were searched for similarities, finding excellent agreement. THe key difference between simulation and experiment is the presence of alpha2 in the simulated transition state, although phi-values indicate that it is unstructured.