Investigations of Thienoacene Molecules for Classical and Entangled Two-Photon Absorption.

Investigations of the optical effects in thienoacene chromophores with different central atoms were performed. These chromophores provide a basis for the comparison of the linear, two-photon, and entangled two-photon properties in organic molecules with varying degrees of dipolar or quadrupolar character. Linear absorption and emission as well as time-dependent density functional theory calculations were performed for the chromophores investigated. Measurements of the classical two-photon absorption (TPA), entangled two-photon absorption (ETPA), as well as entangled two-photon fluorescence were experimentally performed for the four chromophores. Electronic structure calculations were utilized to provide estimates of the classical two-photon absorption coefficients. The results of the measured entangled two-photon cross sections were compared with theoretical estimates for the molecules investigated. It is found that the dipole (transition or permanent) pathway can have an effect on the trends in the entangled photon absorption process in dipolar organic chromophores. This study helps predict the properties of the entangled two-photon effect in chromophores with different dipolar and quadrupolar character.

Optically Excited Entangled States in Organic Molecules Illuminate the Dark.

We utilize quantum entangled photons to carry out nonlinear optical spectroscopy in organic molecules with an extremely small number of photons. For the first time, fluorescence is reported as a result of entangled photon absorption in organic nonlinear optical molecules. Selectivity of the entangled photon absorption process is also observed and a theoretical model of this process is provided. Through these experiments and theoretical modeling it is found that while some molecules may not have strong classical nonlinear optical properties due to their excitation pathways; these same excitation pathways may enhance the entangled photon processes. It is found that the opposite is also true. Some materials with weak classical nonlinear optical effects may exhibit strong non-classical nonlinear optical effects. Our entangled photon fluorescence results provide the first steps in realizing and demonstrating the viability of entangled two-photon microscopy, remote sensing, and optical communications.

Synthesis and photophysical properties of stilbeneoctasilsesquioxanes. Emission behavior coupled with theoretical modeling studies suggest a 3-D excited state involving the silica core.

A set of stilbene-substituted octasilicates [p-RStil(x)Ph(8-x)SiO(1.5)](8) (R = H, Me, MeO, Cl, NMe(2) and x = 5.3-8) and [o-MeStilSiO(1.5)](8) were prepared. Model compounds were also prepared including the corner and half cages: [p-MeStilSi(OEt)(3)], [p-Me(2)NStilSi(OSiMe(3))(3)], and [p-Me(2)NStilSi(O)(OSiMe)](4). These compounds were characterized by MALDI-TOF, TGA, FTIR, and (1)H NMR techniques. Their photophysical properties were characterized by UV-vis, two-photon absorption, and cathodoluminescence spectroscopy (on solid powders), including studies on the effects of solvent polarity and changes in concentration. These molecules are typically soluble, easily purified, and robust, showing T(d(5%)) > 400 degrees C in air. The full and partial cages all show UV-vis absorption spectra (in THF) identical to the spectrum of trans-stilbene, except for [o-MeStilSiO(1.5)](8), which exhibits an absorption spectrum blue-shifted from trans-stilbene. However, the partial cages show emissions that are red-shifted by approximately 20 nm, as found for stilbene-siloxane macrocycles, suggesting some interaction of the silicon center(s) with the stilbene pi* orbital in both the corner and half cages. In contrast, the emission spectra of the full cages show red-shifts of 60-100 nm. These large red-shifts are supported by density functional theoretical calculations and proposed to result from interactions of the stilbene pi* orbitals with a LUMO centered within the cage that has 4A(1) symmetry and involves contributions from all Si and oxygen atoms and the organic substituents. Given that this LUMO has 3-D symmetry, it appears that all of the stilbene units interact in the excited state, consistent with theoretical results, which show an increased red-shift with an increase in the functionalization of a single corner to functionalization of all eight corners with stilbene. In the case of the Me(2)N- derivatives, this interaction is primarily a charge-transfer interaction, as witnessed by the influence of solvent polarity on the emission behavior. More importantly, the two-photon absorption behavior is 2-3 times greater on a per p-Me(2)Nstilbene basis for the full cage than for the corner or half cages. Similar observations were made for p-NH(2)stilbenevinyl(8)OS cages, where the greater conjugation lengths led to even greater red-shifts (120 nm) and two-photon absorption cross sections. Cathodoluminescence studies done on [p-MeStilSiO(1.5)](8) or [p-MeStilOS](8) powders exhibit essentially the same emissions as seen in solution at high dilution. Given that only the emissions are greatly red-shifted in these molecules, whereas the ground-state UV-vis absorptions are not changed from trans-stilbene, except for the ortho derivative, which is blue-shifted 10 nm. It appears that the interactions are only in the excited state. Theoretical results show that the HOMO and LUMO states are always the pi and pi* states on the stilbene, which show very weak shifts with increasing degrees of functionalization, consistent with the small changes in the UV-vis spectra. The band gap between the lowest unoccupied 4a1 symmetry core state localized inside the silsesquioxane cage and the highest occupied state (pi state on stilbene), however, is markedly decreased as the number of stilbene functional groups is increased. This is consistent with the significant red-shifts in the emission spectra. The results suggest that the emission occurs from the 4a1 state localized on the cage. Moreover, for the compounds [p-RStil(6-7)Ph(2-1)OS](8), the emissions are blue-shifted compared to those of the fully substituted compounds, suggesting the molecular symmetry is reduced (from cubic), thereby reducing the potential for 3-D delocalization and raising the energy of the LUMO. The implications are that these octafunctional molecules exhibit some form of 3-D interaction in the excited state that might permit their use as molecular transistors as well as for energy collection and dispersion as molecular antennas, for example, and for nonlinear optical applications.

High dielectric hyperbranched polyaniline materials.

New organic materials for the purpose of high speed capacitor applications are discussed. The effect of the microcrystalline size dependence of different polyaniline polymeric systems on the dielectric constant is investigated. Two different methods are described for the preparation of the polyaniline dielectric materials. By sonication polymerization, the prepared polyaniline with a suggested hyperbranched structure showed much larger microcrystalline domains in comparison to the conventional linear polyaniline. Investigations of the dielectric constant and capacitance at a relatively high frequency (>100 kHz) suggested that the system with the larger microcrystalline domains (hyperbranched) gives rise to a larger dielectric constant. The mechanism of the increased dielectric response at higher frequencies is investigated by EPR spectroscopy, and these results suggest that delocalized polarons may provide a way to enhance the dielectric response at high frequency.

Polaron delocalization in ladder macromolecular systems.

Organic macromolecules with conjugated building blocks have been the focus of extensive research that is motivated, in part, by the potential to create optical and electronic devices. We have shown that palladium-catalyzed amination can assemble triarylamine ladder materials with extended structures. Two ladder macromolecules have been prepared in high yields by a series of twelve or sixteen C-N coupling reactions. Studies of the electronic and optical properties of neutral and oxidized forms of the ladder structures were conducted. The optical and electronic properties of the ladder systems are compared to those of the linear tetra-phenyl-p-phenylenediamine as well as the tetra-p-anisyl-p-tetraazacyclophane. The electrochemistry of the ladder systems consists of a multiwave voltammogram with a relatively low first oxidation potential. Electron paramagnetic resonance spectroscopy of the ladder systems suggests the presence of a large density of delocalized polarons. Linear absorption measurements of the chemically oxidized ladders revealed both polaron and intervalence absorption bands. Steady-state and time-resolved fluorescence measurements were also carried out to characterize the dynamics in these novel systems.

Time-resolved spectroscopy of organic dendrimers and branched chromophores.

Organic dendrimers have been considered for a number of optical applications and are now of great interest for the purpose of enhanced nonlinear optical effects. In order to understand the mechanism of the enhanced effects in branched structures it is important to probe the fundamental excitations and the degree of intramolecular interactions utilizing various spectroscopic techniques. In this review, the nonlinear optical and excited state dynamics of different dendritic and other branching chromophore structures are discussed. The methods of two-photon absorption, time-resolved fluorescence, transient absorption, and three-pulse photon echo peak shift are discussed in regards to the degree of intramolecular coupling in the macromolecular systems. These techniques are also used for a comparison of the dynamics in the linear molecular analog systems as well. Thus, this review focuses on the aspect of intramolecular interactions in a branched system and its importance to enhanced nonlinear optical effects useful for modern optical devices.

Optical excitations in organic dendrimers investigated by time-resolved and nonlinear optical spectroscopy.

Our research is concerned with the optical properties of covalently bound branched multichromophore systems. The presence of strong intramolecular interactions in dendrimers and other branched macromolecules has stimulated new approaches toward improved energy transfer and light-emitting and enhanced nonlinear optical materials, as well as the possibility of delocalized (exciton) excitations in molecular aggregates. This Account summarizes some of our investigations, which combine the use of different time-resolved techniques to examine the dynamics in organic (conjugated) branched structures and provide important structure-function correlations necessary for applications.

Electronic interactions in a branched chromophore investigated by nonlinear optical and time-resolved spectroscopy.

The third order nonlinear optical properties of a trimer branched chromophore system and its linear molecule analog are investigated. Two-photon absorption and degenerate four wave mixing measurements were carried out on both systems. An enhancement in the nonlinear optical effect is observed for the branched trimer molecule in comparison to the linear chromophore system. Ultrafast time-resolved measurements were carried out to probe the excited state dynamics in the branched structures. The time-resolved measurements suggest that the two important processes affecting the nonlinear optical properties in the trimer system, charge transfer stabilization and initial electronic delocalization, occur on two different time scales.

1,2-Dibenzamidobenzene inhibitors of human factor Xa.

High-throughput screening of a combinatorial library of diamidophenols yielded lead compounds with the ability to inhibit human factor Xa (fXa) at micromolar concentrations (e.g. compound 4, fXa apparent K(ass) = 0.64 x 10(6) L/mol). SAR studies in this novel structural series of fXa inhibitors showed that the phenolic hydroxyl group was not essential for activity. The best activity was found in substituted 1,2-dibenzamidobenzenes in which the phenyl group of one benzoyl group (A-ring) was substituted in the 4-position with relatively small lipophilic or polarizable groups such as methoxy, vinyl, or chloro and the phenyl group of the other benzoyl group (B-ring) was substituted in the 4-position with larger lipophilic groups such as tert-butyl or dimethylamino. The central phenyl ring (C-ring) tolerated a wide variety of substituents, but methoxy, methanesulfonamido, hydroxyl, and carboxyl substitution produced slightly higher levels of activity than other substituents when present in combination with favorable B-ring substitution. Methylation of the amide nitrogen atoms was found to greatly decrease activity. Compound 12 is the highest affinity fXa inhibitor in this group of compounds, having fXa apparent K(ass) = 25.5 x 10(6) L/mol, about 40x more active than the original lead. This lead series does not show potent inhibition of human thrombin. A model for the binding of these ligands to the fXa active site is proposed. The model is consistent with the observed SAR and can serve to guide future SAR studies.

N(2)-Aroylanthranilamide inhibitors of human factor Xa.

Reversal of the A-ring amide link in 1,2-dibenzamidobenzene 1 (fXa K(ass) = 0.81 x 10(6) L/mol) led to a series of human factor Xa (hfXa) inhibitors based on N(2)-aroylanthranilamide 4. Expansion of the SAR around 4 showed that only small planar substituents could be accommodated in the A-ring for binding to the S1 site of hfXa. Bulky groups such as 4-isopropyl, 4-tert-butyl, and 4-dimethylamino were favored in the B-ring to interact with the S4 site of hfXa. The central (C) ring containing a 5-methanesulfonamido group yielded greater activity than carbamoyl groups. Combining the beneficial features from the B- and C-ring SAR, compound 55 represents the most potent hfXa inhibitor in the N(2)-aroylanthranilamide 4 series with hfXa K(ass) = 58 x 10(6) L/mol (K(i) = 11.5 nM).

Structure-based design of potent, amidine-derived inhibitors of factor Xa: evaluation of selectivity, anticoagulant activity, and antithrombotic activity.

To enhance the potency of 1,2-dibenzamidobenzene-derived inhibitors of factor Xa (fXa), an amidine substituent was incorporated on one of the benzoyl side chains to interact with Asp189 in the S1 specificity pocket. Lead molecule 1 was docked into the active site of fXa to facilitate inhibitor design. Subsequently, iterative SAR studies and molecular modeling led to a 1000-fold increase in fXa affinity and a refined model of the new inhibitors in the fXa active site. Strong support for the computational model was achieved through the acquisition of an X-ray crystal structure using thrombin as a surrogate protein. The amidines in this series show high levels of selectivity for the inhibition of fXa relative to other trypsin-like serine proteases. Furthermore, the fXa affinity of compounds in this series (K(ass) = 50-500 x 10(6) L/mol) translates effectively into both anticoagulant activity in vitro and antithrombotic activity in vivo.

Pharmacologic actions of the second-generation leukotriene B4 receptor antagonist LY293111: in vitro studies.

The in vitro actions were investigated of LY293111, a potent and selective leukotriene B4 (LTB4) receptor antagonist, on human neutrophils, human blood fractions, guinea pig lung membranes, and guinea pig parenchymal and tracheal strips. The IC50 for inhibiting [3H]LTB4 binding to human neutrophils was 17.6 +/- 4.8 nM. LY293111 inhibited LTB4-induced human neutrophil aggregation (IC50 = 32 +/- 5 nM), luminol-dependent chemiluminescence (IC50 = 20 +/- 2 nM), chemotaxis (IC50 = 6.3 +/- 1.7 nM), and superoxide production by adherent cells (IC50 = 0.5 nM). Corresponding responses induced by N-formyl-L-methionyl-L-leucyl-L-phenylalanine were inhibited by 100-fold higher concentrations of LY293111. LTB4 binding to guinea pig tissues and subsequent activation were also inhibited. The Ki for inhibition of [3H]LTB4 binding to lung membranes was 7.1 +/- 0.8 nM; IC50 for preventing binding of [3H]LTB4 to spleen membranes was 65 nM. The compound inhibited LTB4-induced contraction of guinea pig lung parenchyma. At 10 nM, LY293111 caused a parallel rightward shift of the LTB4 concentration-response curve. At higher concentrations, plots were shifted in a nonparallel manner, and maximum responses were depressed. LY293111 did not prevent antigen-stimulated contraction of sensitized trachea strips. At micromolar concentrations, LY293111 inhibited production of LTB4 and thromboxane B2 by plasma-depleted human blood stimulated with N-formyl-L-methionyl-L-leucyl-L-phenylalanine and thrombin. In addition, at these higher concentrations, formation of LTB4 by A23187-activated whole blood and conversion of arachidonic acid to LTB4 by a human neutrophil cytosolic fraction were inhibited. In summary, LY293111 is a second-generation LTB4 receptor antagonist with much improved potency in a variety of functional assay systems.

High-affinity aptamers selectively inhibit human nonpancreatic secretory phospholipase A2 (hnps-PLA2).

A family of sequence-related 2'-aminopyrimidine, 2'-hydroxylpurine aptamers, developed by oligonucleotide-based combinatorial chemistry, SELEX (systematic evolution of ligand by exponential enrichment) technology, binds human nonpancreatic secretory phospholipase A2 (hnps-PLA2) with nanomolar affinities and inhibits enzymatic activity. Aptamer 15, derived from the family, binds hnps-PLA2 with a Kd equal to 1.7 +/- 0.2 nM and, in a standard chromogenic assay of enzymatic activity, inhibits hnps-PLA2 with an IC50 of 4 nM, at a mole fraction of substrate concentration of 4 x 10(-6) and a calculated Ki of 0.14 nM. Aptamer 15 is selective for hnps-PLA2, having a 25- and 2500-fold lower affinity, respectively, for the unrelated proteins human neutrophil elastase and human IgG. Contractions of guinea pig lung pleural strips induced by hnps-PLA2 are abolished by 0.3 microM aptamer 15, whereas contractions induced by arachidonic acid are not altered. The structure that is essential for binding and inhibition appears to be a 40-base hairpin/loop motif with an asymmetrical internal loop. The affinity and activity of the aptamers demonstrate the ability of the SELEX process to isolate antagonists of nonnucleic-acid-binding proteins from vast oligonucleotide combinatorial libraries.

An assessment of the comprehension of the American Urological Association Symptom Index.

PURPOSE: We determine the reading grade level of the American Urological Association (AUA) symptom index, and assessed patient ability to read and understand the index using a standardized reading and IQ test. MATERIALS AND METHODS: The reading grade level required to read and understand the AUA symptom index was determined using the Spache and Dale-Chall readability formulas. A total of 202 men a mean of 66.1 years old completed the AUA symptom index, Wonderlic personnel test and scholastic level examination, and revised Ohio literacy test. Patients were instructed to report any difficulty in reading or understanding the AUA symptom score. RESULTS: According to the Spache and Dale-Chall readability formulas, the AUA symptom index requires a grade 6 reading level. Of the 202 patients 30 (14.9%) did not complete the symptom index due to an inability to read it (28, 13.9%) and poor comprehension (2, 1%). Tested mean IQ and reading grade level was 91.7 and 11, respectively. CONCLUSIONS: A grade 6 reading level is required to read and understand the AUA symptom index. A significant percentage of patients cannot read the index and require assistance from others for its completion. This assistance may introduce significant interviewer bias, potentially altering study outcome.

Pulmonary actions of LY255283, a leukotriene B4 receptor antagonist.

The actions of LY255283, a leukotriene (LT) B4 receptor antagonist, were examined on guinea pig lung. LTB4 and LY255283 displaced [3H]LTB4 from its binding site on lung membranes with pKi values of 9.9 and 7.0, respectively. In the functional correlate of the binding studies, LY255283 competitively reduced contractile responses of lung parenchyma to LTB4 (pA2 = 7.2). LTB4 produced airway obstruction which was reduced by LY255283 administered i.v. (ED50 = 2.8 mg/kg) or orally (ED50 = 11.0 mg/kg). Contractile responses to histamine, LTD4 and the thromboxane mimetic, U46619, were not reduced by LY255283. The compound also did not inhibit cyclooxygenase or 5-lipoxygenase enzymes. We conclude that LY255283 selectively antagonized pharmacologic responses to LTB4 on lung tissue and appears to be a useful tool to investigate the role of LTB4 in pulmonary disease.

Leukotriene B4 receptor antagonists: the LY255283 series of hydroxyacetophenones.

A series of hydroxyacetophenones was prepared for evaluation as leukotriene B4 (LTB4) receptor antagonists, culminating in 1-[5-ethyl-2-hydroxy-4-[[6-methyl-6-(1H-tetrazol-5- yl)heptyl]oxy]phenyl]ethanone (compound 35, LY255283). Using an assay for inhibition of specific [3H]LTB4 binding to human PMN, we found that substitution of a nonpolar substituent in the 5-position was required for activity. Best activity was realized with hydrogen in the 3-position, hydroxyl in the 2-position, short chain alkyl ketone in the 1-position, and a six- or eight-carbon chain linking the oxygen in the 4-position with an unsaturated terminal function. Compound 35, having an IC50 of 87 nM in the binding assay, was chosen for further preclinical evaluation.

Molecular cloning and expression of human Ca(2+)-sensitive cytosolic phospholipase A2.

Phospholipases A2 (PLA2s) play a key role in inflammatory processes through production of precursors of eicosanoids and platelet-activating factor. Recently, we described the purification of a novel approximately 100-kDa cytosolic PLA2 (cPLA2) from human monoblast U937 cells that is activated by physiological (intracellular) concentrations of Ca2+ (Kramer, R. M., Roberts, E. F., Manetta, J., and Putnam, J. E. (1991) J. Biol. Chem. 266, 5268-5272). Here we report the isolation of the complementary DNA encoding human cPLA2 and confirm its identity by expression in bacteria and in hamster cells. The predicted 749-amino acid cPLA2 protein has no similarity to the well known secretory PLA2s, but contains a structural element homologous to the C2 region of protein kinase C. The molecular cloning of cPLA2 will allow further studies defining the structure, function, and regulation of this novel PLA2.

Structure of recombinant human rheumatoid arthritic synovial fluid phospholipase A2 at 2.2 A resolution.

Phospholipases A2 (PLA2s) may be grouped into distinct families of proteins that catalyse the hydrolysis of the 2-acyl bond of phospholipids and perform a variety of biological functions. The best characterized are the small (relative molecular mass approximately 14,000) calcium-dependent, secretory enzymes of diverse origin, such as pancreatic and venom PLA2s. The structures and functions of several PLA2s are known. Recently, high-resolution crystal structures of complexes of secretory PLA2s with phosphonate phospholipid analogues have provided information about the detailed stereochemistry of transition-state binding, confirming the proposed catalytic mechanism of esterolysis. By contrast, studies on mammalian nonpancreatic secretory PLA2s (s-PLA2s) have only recently begun; s-PLA2s are scarce in normal cells and tissues but large amounts are found in association with local and systemic inflammatory processes and tissue injury in animals and man. Such s-PLAs have been purified from rabbit and rat inflammatory exudate, from synovial fluid from patients with rheumatoid arthritis and from human platelets. Cloning and sequencing shows that the primary structure of the human s-PLA2 has about 37% homology with that of bovine pancreatic PLA2 and 44% homology with that of Crotalus atrox PLA2. The human s-PLA2 is an unusually basic protein, yet contains most of the highly conserved amino-acid residues and sequences characteristic of the PLA2s sequenced so far. Here we report the refined, three-dimensional crystal structure at 2.2 A resolution of recombinant human rheumatoid arthritic synovial fluid PLA2. This may aid the development of potent and specific inhibitors of this enzyme using structure-based design.

Production of a hybrid macrolide antibiotic in Streptomyces ambofaciens and Streptomyces lividans by introduction of a cloned carbomycin biosynthetic gene from Streptomyces thermotolerans.

The structurally related macrolide antibiotics carbomycin (Cb) and spiramycin (Sp) are produced by Streptomyces thermotolerans and Streptomyces ambofaciens, respectively. Both antibiotics contain 16-membered lactone rings to which deoxysugars are attached. There are three sugars in Sp (forosamine, mycaminose and mycarose) and two sugars in Cb (mycaminose and a derivative of mycarose containing an isovaleryl group at position 4). We have identified the gene from S. thermotolerans (designated carE), which appears to encode an enzyme that acylates this mycarose sugar, and have shown that recombinant strains containing carE can use Sp as a substrate and convert it to the hybrid antibiotic, isovaleryl Sp (ivSp). Expression of carE was demonstrated in two heterologous hosts: in S. ambofaciens, where endogenously synthesized Sp was converted to ivSp, and in Streptomyces lividans where exogenously added Sp was converted to ivSp. The carE gene was isolated on a cosmid that also encodes genes required for Cb-lactone formation. These genes reside on a DNA segment of about 70 kb and are part of a Cb biosynthetic gene cluster that is flanked by two Cb-resistance genes, carA and carB. Mapping studies and nucleotide sequence analysis revealed that carE is located at one end of this gene cluster, immediately adjacent to the carB gene. Genes carB and carE are transcribed convergently and may share a common transcriptional terminator sequence.