Nanotechnology in Drug Delivery: Anatomy and Molecular Insight into the Self-Assembly of Peptide-Based Hydrogels.

The bioavailability, release, and stability of pharmaceuticals under physicochemical conditions is the major cause of drug candidates failing during their clinical trials. Therefore, extensive efforts have been invested in the development of novel drug delivery systems that are able to transport drugs to a desired site and improve bioavailability. Hydrogels, and peptide hydrogels in particular, have been extensively investigated due to their excellent biocompatibility and biodegradability properties.

Control of Intermediates and Products by Combining Droplet Reactions and Ion Soft-Landing.

Despite being recognized primarily as an analytical technique, mass spectrometry also has a large potential as a synthetic tool, enabling access to advanced synthetic routes by reactions in charged microdroplets or ionic thin layers. Such reactions are special and proceed primarily at surfaces of droplets and thin layers. Partial solvation of the reactants is usually considered to play an important role for reducing the activation barrier, but many mechanistic details still need to be clarified.

Binding of saturated and unsaturated C-hydrocarbons to the electrophilic anion [BBr]: a systematic mechanistic study.

The highly reactive gaseous ion [BBr] is a metal-free closed-shell anion which spontaneously forms covalent bonds with hydrocarbon molecules, including alkanes. Herein, we systematically investigate the reaction mechanism for binding of [BBr] to the five hexane isomers yielding [BBr(CH)], as well as to cyclohexane and several hexene isomers (yielding [BBr(CH)]) using collision-induced dissociation (CID), infrared photodissociation spectroscopy (IRPD) and computational methods. CID of the different [BBr(CH)] ions results in distinct fragmentation patterns dependent on the structure of the hexane isomer.

New Perspectives in the Noble Gas Chemistry Opened by Electrophilic Anions.

Binding of noble gases (NGs) is commonly considered to be the realm of highly reactive electophiles with cationic or at least non-charged character. Herein, we summarize our latest results evidencing that the incorporation of a strongly electrophilic site within a rigid cage-like anionic structure offers several advantages that facilitate the binding of noble gases and stabilize the formed NG adducts. The anionic superelectrophiles investigated by us are based on the -dodecaborate dianion scaffold.

LASER IONIZATION MASS SPECTROMETRY AT 55: QUO VADIS?

Laser ionization mass spectrometry (LIMS) was one of the first practical methods developed for in situ analysis of the surfaces of solid samples. This review will encompass several aspects related to this analytical method. First, we will discuss the process of laser ionization, the influence of the laser type on its performance, and imaging capabilities of this method.

Direct functionalization of C-H bonds by electrophilic anions.

Alkanes and [BX] (X = Cl, Br) are both stable compounds which are difficult to functionalize. Here we demonstrate the formation of a boron-carbon bond between these substances in a two-step process. Fragmentation of [BX] in the gas phase generates highly reactive [BX] ions which spontaneously react with alkanes.

Photoelectron spectroscopy of [MoX] dianions (X = Cl-I).

Photoelectron spectroscopy and theoretical investigations have been performed to systematically probe the intrinsic electronic properties of [MoX] (X = halogen). All three PE spectra of gaseous [MoX] (X = Cl, Br, I) dianions, which were generated by electrospray ionization, exhibit multiple resolved peaks in the recorded binding energy range. Theoretical investigations on the orbital structure and charge distribution were performed to support interpretation of the observed spectra and were further extended onto [MoF], a dianion that was not available for the experimental study.

Rational design of an argon-binding superelectrophilic anion.

Chemically binding to argon (Ar) at room temperature has remained the privilege of the most reactive electrophiles, all of which are cationic (or even dicationic) in nature. Herein, we report a concept for the rational design of anionic superelectrophiles that are composed of a strong electrophilic center firmly embedded in a negatively charged framework of exceptional stability. To validate our concept, we synthesized the percyano-dodecoborate [B(CN)], the electronically most stable dianion ever investigated experimentally.

Comparison of computationally cheap methods for providing insight into the crystal packing of highly bromomethylated azobenzenes.

For five bromomethylated azobenzenes, namely (E)-[4-(bromomethyl)phenyl][4-(dibromomethyl)phenyl]diazene, CHBrN, (E)-1,2-bis[4-(dibromomethyl)phenyl]diazene, CHBrN, (E)-[3-(bromomethyl)phenyl][3-(dibromomethyl)phenyl]diazene, CHBrN, (E)-[3-(dibromomethyl)phenyl][3-(tribromomethyl)phenyl]diazene, CHBrN, and (E)-1,2-bis[3-(dibromomethyl)phenyl]diazene, CHBrN, the computationally cheap CLP PIXEL approach and CrystalExplorer were used for calculating lattice energies and performing Hirshfeld surface analysis via the enrichment ratios of atomic contacts. The procedures and caveats are discussed in detail. The findings from these tools are contrasted with the results of geometric analysis of the structures.

"Solvent-in-salt" systems for design of new materials in chemistry, biology and energy research.

Inorganic and organic "solvent-in-salt" (SIS) systems have been known for decades but have attracted significant attention only recently. Molten salt hydrates/solvates have been successfully employed as non-flammable, benign electrolytes in rechargeable lithium-ion batteries leading to a revolution in battery development and design. SIS with organic components (for example, ionic liquids containing small amounts of water) demonstrate remarkable thermal stability and tunability, and present a class of admittedly safer electrolytes, in comparison with traditional organic solvents.

Superelectrophilic Behavior of an Anion Demonstrated by the Spontaneous Binding of Noble Gases to [B Cl ].

It is common and chemically intuitive to assign cations electrophilic and anions nucleophilic reactivity, respectively. Herein, we demonstrate a striking violation of this concept: The anion [B Cl ] spontaneously binds to the noble gases (Ngs) xenon and krypton at room temperature in a reaction that is typical of "superelectrophilic" dications. [B Cl Ng] adducts, with Ng binding energies of 80 to 100 kJ mol , contain B-Ng bonds with a substantial degree of covalent interaction.

Evidence for an intrinsic binding force between dodecaborate dianions and receptors with hydrophobic binding pockets.

A gas phase binding study revealed strong intrinsic intermolecular interactions between dianionic halogenated closo-dodecaborates [B12X12](2-) and several neutral organic receptors. Oxidation of a tetrathiafulvalene host allowed switching between two host-guest binding modes in a supramolecular complex. Complexes of β-cyclodextrin with [B12F12](2-) show remarkable stability in the gas phase and were successfully tested as carriers for the delivery of boron clusters into cancer cells.

Tuning of tetrathiafulvalene properties: versatile synthesis of N-arylated monopyrrolotetrathiafulvalenes via Ullmann-type coupling reactions.

An Ullmann-type coupling reaction was employed for the preparation of several N-arylated monopyrrolotetrathiafulvalenes with variable substitution patterns. Spectroscopic and electrochemical properties of the coupling products strongly depend on the electronic nature of the aromatic substituents due to their direct conjugation with the tetrathiafulvalene chromophore. The crystal packing of the arylated monopyrrolotetrathiafulvalenes is primarily defined by networks of C-H···X weak hydrogen bonds and short S···S contacts involving the tetrathiafulvalene moieties.

Light-controlled macrocyclization of tetrathiafulvalene with azobenzene: designing an optoelectronic molecular switch.

Macrocyclization between tetrathiafulvalene (TTF) dithiolates and bis-bromomethylazobenzenes/bis-bromomethylstilbenes is investigated under high dilution conditions. We show that macrocycles of different size can be formed depending on whether the (Z)- or (E)-isomers of azobenzene (AB) or stilbene are used. This represents the first example of a light-controllable cyclization reaction.

Relative substituent orientation in the structure of cis-3-chloro-1,3-dimethyl-N-(4-nitro-phen-yl)-2-oxo-cyclo-pentane-1-carboxamide.

The structure of the title compound, C14H15ClN2O4, prepared by reaction of a methacryloyl dimer with nitro-aniline, was determined to establish the relative substituent orientation on the cyclo-penta-none ring. In agreement with an earlier proposed reaction mechanism, the amide group and the methyl group adjacent to the chloro substituent adopt equatorial positions and relative cis orientation, whereas the Cl substituent itself and the methyl group adjacent to the amide have axial orientations relative to the mean plane of the five-membered ring. The conformation of the mol-ecule is stabilized by one classical N-H⋯O (2.

2-(1,3-Di-thiol-2-yl-idene)-1,3-di-thiole-4-carbaldehyde.

The structure of the title compound, C7H4OS4, at 100 K has ortho-rhom-bic symmetry. In the crystal, tetra-thia-fulvalene mol-ecules form π-stacks along the a axis, with a stacking distance of 3.4736 (6) Å.

Rationally designed calix[4]arene-pyrrolotetrathiafulvalene receptors for electron-deficient neutral guests.

Four upper rim bis-monopyrrolotetrathiafulvalene-calix[4]arene conjugates 2a,b and 3a,b have been efficiently synthesized using a modular construction approach. The new compounds feature a molecular tweezer architecture with a quasi-parallel arrangement of redox-active tetrathiafulvalene (TTF) arms, which serve as the guest binding centers. Complexation studies using UV/vis binding titrations revealed a high affinity of the calixarene-TTF receptors for planar electron-deficient guests, leading to formation of deeply colored charge-transfer complexes in solution.

5,11,17,23-Tetra-kis(chloro-meth-yl)-25,26,27,28-tetra-propoxycalix[4]arene.

The title calix[4]arene, C(44)H(52)Cl(4)O(4), displays the 1,3-alternate conformation with crystallographically imposed twofold symmetry. Four phenolic rings of the calixarene backbone are tilted into the calix cavity, making dihedral angles of 77.42 (2) and 77.

Real-time, in vivo monitoring and pharmacokinetics of valproic acid via a novel biomarker in exhaled breath.

Extractive electrospray ionization mass spectrometry is shown to allow real-time, in vivo drug monitoring and pharmacokinetic measurement in a non-invasive, pain-free manner as demonstrated by the mass spectral measurement of a novel exhaled breath biomarker for valproic acid, a medication used to control epilepsy.

2,3,6,7-Tetra-kis(bromo-meth-yl)naphthalene.

The title compound, C(14)H(12)Br(4), crystallizes with imposed inversion symmetry. In the crystal, the mol-ecules pack in layers parallel to (10). The layers involve two Br⋯Br and one H⋯Br contact.

Conformational behavior of pyrazine-bridged and mixed-bridged cavitands: a general model for solvent effects on thermal "vase-kite" switching.

The controllable switching of suitably bridged resorcin[4]arene cavitands between a "vase" conformation, with a cavity capable of guest inclusion, and a "kite" conformation, featuring an extended flattened surface, provides the basis for ongoing developments of dynamic molecular receptors, sensors, and molecular machines. This paper describes the synthesis, X-ray crystallographic characterization, and NMR analysis of the "vase-kite" switching behavior of a fully pyrazine-bridged cavitand and five other mixed-bridged quinoxaline-bridged cavitands with one methylene, phosphonate, or phosphate bridge. The pyrazine-bridged resorcin[4]arene cavitand displayed an unexpectedly high preference for the kite conformation in nonpolar solvents, relative to the quinoxaline-bridged analogue.

Selective steroid recognition by a partially bridged resorcin[4]arene cavitand.

The partially bridged resorcin[4]arene cavitand featuring a cleft-shaped recognition site formed by two anti-quinoxaline bridges and four convergent HO-groups was prepared in three steps and characterised by X-ray crystallography; cavitand was found to be a selective receptor for steroidal substrates in CDCl3, with the best binding observed for steroids with a flat A-ring and two H-bonding sites on rings A and C/D.

Clear evidence of fluorescence resonance energy transfer in gas-phase ions.

Fluorescence resonance energy transfer (FRET) is a distance-sensitive method that correlates changes in fluorescence intensity with conformational changes, for example, of biomolecules in the cellular environment. Applied to the gas phase in combination with Fourier transform ion cyclotron resonance mass spectrometry, it opens up possibilities to define structural/conformational properties of molecular ions, in the absence of solvent, and without the need for purification of the sample. For successfully observing FRET in the gas phase it is important to find suitable fluorophores.