The Plasma Membrane as a Reservoir,Protective Shield,and Light‐Triggered Launch Pad for Peptide Therapeutics

Although peptide‐based therapeutics are finding increasing application in the clinic, extensive structural modification is typically required to prevent their rapid degradation by proteases in the blood. We have evaluated the ability of erythrocytes to serve as reservoirs, protective shields (against proteases), and light‐triggered launch pads for peptides. We designed lipidated peptides that are anchored to the surface of red blood cells, which furnishes a protease‐resistant environment. A photocleavable moiety is inserted between the lipid anchor and the peptide backbone, thereby enabling light‐triggered peptide release from erythrocytes. We have shown that a cell‐permeable peptide, a hormone (melanocyte stimulating hormone), and a blood‐clotting agent can be anchored to erythrocytes, protected from proteases, and photolytically released to create the desired biological effect.     

Hydrogen-bonding interactions in peptide nucleic acid and deoxyribonucleic acid: a comparative study

Peptide nucleic acid (PNA) is a synthetic analogue of deoxyribonucleic acid (DNA) capable of tightly binding to itself and DNA with high specificity. Using hybrid density functional methods, hydrogen-bond (H-bond) strengths have been evaluated for isolated Watson-Crick base pairs, PNA base pairs, and charged as well as neutral DNA base pairs. Heterogeneous base pairs of PNA with charged and neutral DNA have also been investigated. The competing effects of short-range H-bonding and long-range Coulombic repulsions in charged DNA base pairs have been analyzed. Polarizable continuum models have been employed to evaluate solvation effects on the binding energies.     

Spectroscopic investigations under whole-cell conditions provide new insight into the metal hydride chemistry of [FeFe]-hydrogenase

Hydrogenases are among the fastest H₂ evolving catalysts known to date and have been extensively studied under in vitro conditions. Here, we report the first mechanistic investigation of an [FeFe]-hydrogenase under whole-cell conditions. Functional [FeFe]-hydrogenase from the green alga Chlamydomonas reinhardtii is generated in genetically modified Escherichia coli cells by addition of a synthetic cofactor to the growth medium. The assembly and reactivity of the resulting semi-synthetic enzyme was monitored using whole-cell electron paramagnetic resonance and Fourier-transform Infrared difference spectroscopy as well as scattering scanning near-field optical microscopy. Through a combination of gas treatments, pH titrations, and isotope editing we were able to corroborate the formation of a number of proposed catalytic intermediates in living cells, supporting their physiological relevance. Moreover, a previously incompletely characterized catalytic intermediate is reported herein, attributed to the formation of a protonated metal hydride species.

The mechanism of hydrogen gas formation by [FeFe] hydrogenase is probed under whole cell conditions, revealing the formation of reactive metal hydride species under physiologically relevant conditions.     

Asymmetric synthesis of dihydroindanes by convergent alkoxide-directed metallacycle-mediated bond formation

A convergent synthesis of highly substituted and stereodefined dihydroindanes is described from alkoxide-directed Ti-mediated cross-coupling of internal alkynes with substituted 4-hydroxy-1,6-enynes (substrates that derive from 2-directional functionalization of readily available epoxy alcohol derivatives). In addition to describing a new and highly stereoselective approach to bimolecular [2 + 2 + 2] annulation that delivers products not available with other methods in this area of chemical reactivity, evidence is provided to support annulation by way of regioselective alkyne-alkyne coupling, followed by metal-centered [4 + 2] rather than stepwise alkene insertion and reductive elimination. Overall, the reaction proceeds with exquisite stereochemical control and defines a convenient, convergent, and enantiospecific entry to fused carbocycles of great potential value in target-oriented synthesis and medicinal chemistry.     

Sensor Array: Impedimetric Label‐Free Sensing of DNA Hybridization in Real Time for Rapid,PCR‐Based Detection of Microorganisms

A novel, impedance‐based electronic sensor format was used for label‐free, real‐time detection of microbial DNA on oligonucleotide probe arrays. Detection limits of 5–10 nM were achieved for single‐stranded, PCR‐amplified DNA targets. Hybridization selectivity yielded 9‐ to 12‐fold signal increases for specific targets, and the sensor arrays were re‐used multiple times without significant signal degradation. These and other features of the SHARP Laboratories of America (SLA) sensor array, such as its ability to acquire continuous measurements of DNA as it accumulates on the array surface, make it an attractive biosensor platform for field detection and monitoring of sentinel and/or pathogenic microorganisms.     

Hemoglobin adsorption to silica monitored with polarization-dependent evanescent-wave cavity ring-down spectroscopy

Evanescent-wave cavity ring-down spectroscopy was used to monitor the adsorption of human hemoglobin to a fused-silica surface from aqueous solution. An uncoated dove prism was situated in a ring-down cavity such that the beam entered and exited with a normal-incidence geometry. This afforded ring-down times as high as 5 mus and values of sigma(tau)/tau as low as 0.3%. Normal-incidence geometry permits the detection of both S- and P-polarized light, yielding some information of the orientation of adsorbates. The orientation of the adsorbed hemoglobin molecules is found to change as adsorption progresses, but with a different time profile than adsorption itself. The adsorption kinetics from a quiescent solution is consistent with a reaction-diffusion model that includes both reversible and irreversible adsorption operating in parallel. Systems behaving according to this model also seem to display adsorption isotherms, although the increased adsorption from more concentrated solutions is only a consequence of the system being under kinetic control. In some cases, this may be sufficient to explain the paradox of protein adsorption systems which seem to be both irreversible and consistent with isotherm models as well.     

Synthesis and electric field actuation of an ionic liquid polymer

Polymerizable ionic liquids and their actuation in an electric field are a combination of material and properties with unique potential to display structural and fluid dynamics above that found in small molecule ionic liquids. In an effort to blend ionic liquid nature with actuation response, we have synthesized a new ionic liquid ammonium sulfonate monomer and polymer. The liquid temperature ranges of both the monomer and polymer ionic liquid systems are quite large extending from their respective glass transitions (Tg) of -57 and -49 degrees C to decomposition at approximately 200 degrees C. Particularly remarkable is the small Tg increment that accompanies the transformation from monomer to polymer. The electrowetting behavior of the polymer and of the monomer presents an interesting contrast. This communication will encompass the polymerization, characterization, and actuation of these new ionic liquids.     

Nonperturbative calculation of born-infeld effects on the schrödinger spectrum of the hydrogen atom

We present the first nonperturbative calculations of the nonrelativistic hydrogen spectrum as predicted by first-quantized nonlinear Maxwell-Born-Infeld electrodynamics with point charges. Judged against empirical data our results significantly restrict the range of viable values of the new electromagnetic constant beta introduced by Born. We assess Born's own proposal for the value of beta.     

Synthesis of the new pyrido[1,2-c]benzo-v-triazinium system via valence bond isomerization

α-Pyridylphenyl diazonium salts 2 were found to undergo valence bond isomerization and gave the new pyrido[ 1 ,2-c]benzo-v-triazinium salts 3. The ir and nmr studies on the products showed that isomers 2 and 3 form an equilibrium, and the ring closure is favoured by electron withdrawing substituents.