We report the derivatization of hyperbranched poly(acrylic acid) (PAA) films with a wide range of amino- or alcohol-terminated molecules. These molecules can include moieties such as pyrene, ferrocene, poly(ethylene glycol), 15-crown-5, and a dye. To derivatize PAA films, we activate their carboxylic acid groups with isobutyl chloroformate and allow them to react with amine- or alcohol-containing molecules. Infrared spectroscopy demonstrates the formation of amide and ester bonds upon coupling as well as the presence of the derivative functional groups. Excimer fluorescence from pyrene-containing films implies a high density of pyrene groups. However, we can control the amount of pyrene in the film (and obtain monomer fluorescence) by varying the concentration of Py(CH2)3CONH(CH2)2NH2 in the derivatization solution. Cyclic voltammetry of ferrocene-containing films shows an electrochemically addressable ferrocenyl surface coverage of (6 ± 3) × 10-9 mol/cm2 in three-layer PAA films. PAA films and their derivatives are stable under sonication, Soxhlet extraction, and acidic and basic conditions. PAA films also respond to external stimuli. The ellipsometric thickness of PAA films increases by ≈45% upon deprotonation of the film's carboxylic acid groups and returns to its original thickness after acidification. Using surface acoustic wave mass sensors, we observed that pure PAA films adsorb or absorb volatile organic compounds (VOCs), although the amount is in the monolayer range. Fluorination of PAA films increases the amount of polar VOCs absorbed by an order of magnitude.

No abstract

No abstract

We report the synthesis and passivation properties of surface-grafted, highly fluorinated, hyperbranched poly(acrylic acid) (PAA) films that contain up to 50 atom % F. These films are very hydrophobic (water contact angle of up to 114°) and block electrochemical reactions on gold electrodes. Cyclic voltammetry in basic solution shows that while an electrode covered with a three-layer PAA (3-PAA) film mimics an assembly of microelectrodes, a fluorinated three-layer PAA (3-PAA/F) film blocks nearly all electron transfer to the gold surface. The charge transfer resistance of electrodes covered with a 3-PAA/F film is about 40 times greater than that for an electrode covered with a nonfluorinated 3-PAA film. 3-PAA/F films are initially 10 times more blocking than C16SH SAMs. Additionally, while the SAM is desorbed by electrochemical cycling, 3-PAA/F films are still highly blocking after ten potential sweeps over a 1.5 V range. Thus fluorinated PAA films are promising candidates for corrosion-inhibiting coatings.

No abstract

The synthesis of 60−1000 Å thick films of fluorinated polymers on gold and silica substrates via amidation of layered, hyperbranched poly(acrylic acid) surface-graft films with a fluorinated octylamine is described. These syntheses proceed either by formation and fluoramidation of layers of poly(acrylic acid) or by stepwise formation of layers of a mixture of poly(acrylic acid) and a fluorinated poly(acrylamide) on a carboxylic acid-containing self-assembled monolayer on gold or on aminopropylated silica. Depending on the chemistry used, these grafts can be prepared so that they have fluorinated interiors and either hydrophobic or hydrophilic exteriors. Ellipsometric studies of these grafts on gold show that the thickness of the layers can be controlled on the basis of the number of PAA layers present and that fluorination using a fluorinated octylamine roughly doubled layer thickness. Infrared and X-ray photoelectron spectroscopy studies were used to characterize these surfaces.

The spectroscopic properties and thermal stability of Er2O3 doped Bi2O3–B2O3–Na2O glasses are investigated experimentally. A close correlation is observed between the B2O3 content and the spectroscopic properties such as Judd–Ofelt intensity parameters Ωt (t=2,4,6), emission spectra, and lifetime of I13/24 level of Er3+. The value of Ω6 increases with an increase of B2O3 content, which is attributed to the decrease of the covalency of Er–O bond in terms of the glass microstructure and electronegativity theory. The emission spectra of I13/24→4I15/2 transition broadens as a consequence of the enhancement of the inhomogeneous distribution of Er3+ sites when increasing B2O3 content. The lifetime of I13/24 level of Er3+ in bismuth-based glass, compared with those in other glasses, is relative low due to the high-phonon energy of the B–O bond, the large refractive index of the host, and the existence of OH− in the glass. In addition, the glass stability is improved in which the substitution of B2O3 for Bi2O3 strengthens the network structure. The suitability of bismuth-based glass as a host for Er3+ doped for a broadband amplifier and its advantages over other glass hosts are also discussed.

Aminoglycoside antibiotics target an internal RNA loop within the bacterial ribosomal decoding site. Here, we described the synthesis and SAR of novel 3,5-diamino-piperidine derivatives as aminoglycoside mimetics, and show they act as inhibitors of bacterial translation and growth. KeywordsAminoglycosides; Antibiotics; Translation inhibitors; 2-deoxy-streptamine; Ribosome; Decoding site; 3; 5-diamino-piperidine Bacterial resistance to antibiotics is on the rise and represents a global medical threat. In hospitals in the United States, approximately two million patients per year are infected. 1 The majority of these nosocomial pathogens are resistant to at least one antibiotic and result in about 90,000 deaths per year; a number that has increased 7-fold over the last decade. The recent and rapid spread of community acquired methicillin resistant Staphylococcus aureus further highlights the threat of resistance development and illustrates the need for new antibiotics that work by novel mechanisms. 2 Given the broad genetic and physiological diversity of bacterial pathogens and the need for empiric therapies that cover a broad panel of organisms, it is not surprising that discovery of new antibiotics has advanced slowly. Central to antibiotic discovery is identifying broadly validated targets. One such proven target is the bacterial ribosome, which is the target for a significant number of clinically important antibiotics that bind at the ribosomal RNA (rRNA). 3 Here, we expand on the description of a novel series of antibacterial compounds that target rRNA and blocks bacterial translation and growth. 4Three-dimensional structures of different aminoglycosides bound to the decoding site, or Asite, within the 16S rRNA have been determined by X-ray crystallography. 5 Importantly, these studies have shown that 2-deoxystreptamine (2-DOS), a conserved core scaffold among aminoglycosides, binds in a similar manner regardless of the 4,5-or 4,6-disubstitutions found in the neomycin or gentamicin families, respectively (Fig. 1) Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript groups of 2-DOS are predominantly involved in base recognition by forming conserved hydrogen bonds with A1493, G1494 and U1495 of the 16S rRNA. These interactions anchor the aminoglycoside scaffold within the A-site internal loop and displace residues A1492 and A1493 from the RNA interior. These two adenine residues act as a molecular switch that is involved in securing the fidelity of translation by interacting w...