Formation of insoluble perylenetetracarboxylic diimide films by electro- or photo-crosslinking of pyrrole units

Perylenetetracarboxylic diimide derivatives bearing 2- or 4-peripheral pyrrole pendants could be efficiently crosslinked to form an insoluble film either by electropolymerization or visible light induced oxidative photopolymerization of the pyrrole units.     

Inverted sapphyrin: a new family of doubly N-confused expanded porphyrins

The synthesis of an inverted, methoxylated sapphyrin derivative is described. This system, wherein inversion of pyrrolic nitrogen atoms is configurationally enforced via the use of a 3,3'-bipyrrolic precursor, displays what is best described as "weak aromaticity" as judged from its spectroscopic features and supporting theoretical calculations.     

Solution state structure determination of silicate oligomers by 29SI NMR spectroscopy and molecular modeling

Evidence for nine new solution state silicate oligomers has been discovered by (29)Si NMR homonuclear correlation experiments of (29)Si-enriched samples. In addition to enhancing signal sensitivity, the isotopic enrichment increases the probability of the (29)Si-(29)Si two-bond scalar couplings that are necessary for the observation of internuclear correlations in 2-D experiments. The proposed assignments are validated by comparisons of experimental and simulated cross-peaks obtained with high digital resolution. The internuclear connectivity indicated by the NMR data suggests that several of these oligomers can have multiple stereoisomers, including conformers and/or diastereomers. The stabilities of these oligomers and their possible stereoisomers have been investigated by electronic structure calculations.     

Nanoporous block copolymer micelle/micelle multilayer films with dual optical properties

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with tunable optical properties. Protonated polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and anionic polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the opposite BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (M(w)) of the constituents. PS(7K)-b-P4VP(28K)/PS(2K)-b-PAA(8K) films prepared at pH 4 (for PS(7K)-b-P4VP(28K)) and pH 6 (for PS(2K)-b-PAA(8K)) are highly nanoporous and antireflective. In contrast, PS(7K)-b-P4VP(28K)/PS(2K)-b-PAA(8K) films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS(2K)-b-PAA(8K). Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS(36K)-b-P4VP(12K)/PS(16K)-b-PAA(4K) at pH 4/4) were also nanoporous. This is attributed to a decrease in interdigitation between the adjacent corona shells of the low M(w) BCMs, thus creating more void space between the micelles. Multilayer films with antireflective and photochromic properties were obtained by incorporating a water-insoluble photochromic dye (spiropyran) into the hydrophobic PS core of the BCMs assembled in the films. The optical properties of these films can be modulated by UV irradiation to selectively and reversibly control the transmission of light. Light transmission of higher than 99% was observed with accompanying photochromism in the (PS(7K)-b-P4VP(28K)/PS(2K)-b-PAA(8K)) multilayer films assembled at pH 4/6. Our approach highlights the potential to incorporate a range of materials, ranging from conventional hydrophilic materials with specific interactions to hydrophobic compounds, into the assembled BCMs to yield multifunctional nanoporous films.     

Diindolylquinoxalines: effective indole-based receptors for phosphate anion

The synthesis of a new series of 2,3-diindol-3'yl quinoxalines (DIQ), as well as a comparison of their anion recognition properties to those of our previously reported pyrrole based sensors, 2,3-dipyrrol-2'yl quinoxalines, is reported. To the best of our knowledge, this new DIQ system represents the first example of a free-standing indole-based small molecule receptor for which evidence of anion binding is available both in solution and in the solid-state. It also provides one of the few structurally characterized neutral receptor-dihydrogen phosphate complexes. This work thus serves to demonstrate the utility of indoles as an anion recognition motif.     

Preparation and evaluation of unimolecular pentavalent and hexavalent antigenic constructs targeting prostate and breast cancer: a synthetic route to anticancer vaccine candidates

Several novel, fully synthetic, carbohydrate-based antitumor vaccines have been assembled. Each construct consists of multiple cancer-related antigens displayed on a single polypeptide backbone. Recent advances in synthetic methodology have allowed for the incorporation of a complex oligosaccharide terminating in a sialic acid residue (i.e., GM2) as one of the carbohydrate antigens. Details of the vaccine synthesis as well as the results of preliminary immunological investigations are described herein.     

Vibrational dynamics of DNA. I. Vibrational basis modes and couplings

Carrying out density functional theory calculations of four DNA bases, base derivatives, Watson-Crick (WC) base pairs, and multiple-layer base pair stacks, we studied vibrational dynamics of delocalized modes with frequency ranging from 1400 to 1800 cm(-1). These modes have been found to be highly sensitive to structure fluctuation and base pair conformation of DNA. By identifying eight fundamental basis modes, it is shown that the normal modes of base pairs and multilayer base pair stacks can be described by linear combinations of these vibrational basis modes. By using the Hessian matrix reconstruction method, vibrational coupling constants between the basis modes are determined for WC base pairs and multilayer systems and are found to be most strongly affected by the hydrogen bonding interaction between bases. It is also found that the propeller twist and buckle motions do not strongly affect vibrational couplings and basis mode frequencies. Numerically simulated IR spectra of guanine-cytosine and adenine-thymine bases pairs as well as of multilayer base pair stacks are presented and described in terms of coupled basis modes. It turns out that, due to the small interlayer base-base vibrational interactions, the IR absorption spectrum of multilayer base pair system does not strongly depend on the number of base pairs.     

Anion binding to monotopic and ditopic macrocyclic amides

[Structure: see text] Binding of fluoride anion as well as carboxylic acid tetraalkylammonium salts by macrocyclic compounds of different size was studied by NMR in DMSO-d6. It has been found that at least a 15-membered ring is necessary for successful recognition of fluoride. Larger macrocycles obtained in a [2+2] cyclization were shown to bind dicarboxylic acid salts. Effects of binding topicity are discussed.     

How do women decide? Accepting or declining BRCA1/2 testing in a nationwide clinical sample in the United States

OBJECTIVE: To examine the role of the practitioner, informed consent, and genetic counseling in genetic testing decisions and to assess their relative influence on women's decision to have clinical BRCA1/2 testing. METHODS: Qualitative study using in-depth open-ended interviews with 68 women who had considered clinical BRCA1/2 testing. RESULTS: Slightly less than half of the women who had considered BRCA1/2 testing were found to have had a clear and preexisting desire to test or not to test, irrespective of practitioner attitude or advice. CONCLUSION: The decision to accept or decline genetic testing is the result of a complex process that goes beyond interactions between health care providers and patients, indicating a caution against exclusive reliance on informed consent or counseling encounters.     

Purification and characterization of a biosurfactant produced by Pseudomonas sp. G11 by asymmetrical flow field-flow fractionation (AsFlFFF)

Three hundred and thirty two bacterial colonies were isolated from soil contaminated by an oil spill. All the bacteria were cultured in a liquid medium individually, and the surface tensions of the media were compared. The bacterium whose culture medium had the lowest surface tension was identified as Pseudomonas sp. G11. A biosurfactant was produced by cultivation of the Pseudomonas sp. G11 in the LB media. For extraction of the biosurfactant, two solvent systems were used (n-hexane and a 2:1 (v/v) mixture of chloroform/MeOH), and the results were compared. Various experimental conditions (solvent composition, flow rate, etc.) were tested to optimize the analysis of the biosurfactant by asymmetrical flow field-flow fractionation (AsFlFFF). The biosurfactant was successfully separated from the culture medium by AsFlFFF when pure water was used as the carrier. From the retention data, the hydrodynamic diameter (d _H) and molecular weight (M) of the biosurfactant were determined by AsFlFFF. The molecular weight was determined by using pullulans as the calibration standards. The d _H and M were 49 nm and 2.3 × 10⁵ Da when extracted with n-hexane, and 39 nm and 1.13 × 10⁵ Da when extracted with the 2:1 mixture of chloroform/MeOH, respectively. Figure Separation of biosurfactant from its culture medium by flow FFF