On-demand guest release from MOF-5 sealed with nitrophenylacetic acid photocapping groups.

Recently, we demonstrated that triphenylacetic acid could be used to seal dye molecules within MOF-5, but guest release required the digestion of the framework by treatment with acid. We prepared the sterically bulky photocapping group [bis-(3-nitro-benzyl)-amino]-(3-nitro-phenyl)-acetic acid (PC1) that can prevent crystal violet dye diffusion from inside MOF-5 until removed by photolysis.

MOF Decomposition and Introduction of Repairable Defects Using a Photodegradable Strut.

Photoswitchable components can modulate the properties of metal organic frameworks (MOFs); however, photolabile building blocks remain underexplored. A new strut NPDAC (2-nitro-1,4-phenylenediacetic acid) that undergoes photodecarboxylation has been prepared and incorporated into a MOF, using post-synthetic linker exchange (PSLE) from the structural analogue containing PDAC (p-phenylenediacetic acid). Irradiation of NPDAC-MOF leads to MOF decomposition and concomitant formation of amorphous material.

Detection of adsorbates on emissive MOF surfaces with X-ray photoelectron spectroscopy.

Luminescent metal-organic frameworks (MOFs) have been explored extensively as potential probes for nitroaromatic molecules, which are common constituents of explosive devices. Guest encapsulation within MOF pores is often cited as the prerequisite for emission changes, but the evidence for this signal transduction mechanism is often inadequate. Using the unique bipyridyl ligand AzoAEpP (2,2'-bis[N,N'-(4-pyridyl)ethyl]diaminoazobenzene), we constructed two luminescent pillared paddle-wheel Zn2+ MOFs using aryl dicarboxylate ligands 1,4-naphthalenedicarboxylic acid (ABMOF-1) and benzene 1,4-dicarboxylic acid (ABMOF-2).

Emissive Azobenzenes Delivered on a Silver Coordination Polymer.

Azobenzene has become a ubiquitous component of functional molecules and polymeric materials because of the light-induced trans → cis isomerization of the diazene group. In contrast, there are very few applications utilizing azobenzene luminescence, since the excitation energy typically dissipates via nonradiative pathways. Inspired by our earlier studies with 2,2'-bis[ N,N'-(2-pyridyl)methyl]diaminoazobenzene (AzoAM oP) and related compounds, we investigated a series of five aminoazobenzene derivatives and their corresponding silver complexes.

Impact of subglottic suctioning on the incidence of pneumonia after cardiac surgery: a retrospective observational study.

Objective: Continuous aspiration of subglottic secretions (CASS) has been found to decrease the incidence of pneumonia in the general intensive care unit (ICU) population, but its benefit in cardiac surgery patients is unclear. The present study aimed to determine whether the routine use of CASS in cardiac surgical patients was associated with decreased pneumonia.

Design: A retrospective, single-center observational study.

Transformation of a mononitrosyl iron complex to a [2Fe-2S] cluster by a cysteine analogue.

Reversible modification of iron-sulfur clusters by nitric oxide acts as a genetic switch in a group of regulatory proteins. While the conversion of [Fe-S] clusters to iron-nitrosyls has been widely studied in the past, little is known about the reverse process, the repair of [Fe-S] clusters. Reported here is a system in which a mononitrosyl iron complex (MNIC), (PPN)[Fe(S(t)Bu)3(NO)] (1), is converted to a [2Fe-2S] cluster, (PPN)2[Fe2S2(SCH2CH2C(O)OMe)4] (2).

Increasing the dynamic range of metal ion affinity changes in Zn2+ photocages using multiple nitrobenzyl groups.

Two generations of DiCast photocages that exhibit light-induced decreases in metal ion affinity have been prepared and characterized. Expansion of the common Zn(2+) chelator of N,N-dipicolylaniline (DPA) to include additional aniline ligand provides N,N'-diphenyl-N,N'-bis(pyridin-2-ylmethyl)ethane-1,2-diamine, a tetradentate ligand that was functionalized with two photolabile groups to afford DiCast-1. Uncaging of the nitrobenzhydrol reduces the electron density on two metal-bound aniline ligands, which decreases the Zn(2+) affinity 190-fold.

Quantifying factors that influence metal ion release in photocaged complexes using ZinCast derivatives.

Two generations of nitrobenzhydrol-based photocages for Zn(2+) have been prepared and characterized. The first series includes the tridentate ZinCast-1 utilizes a bis-pyridin-2-ylmethyl-aniline ligand that forms a 5,5-chelate ring upon metal binding. The related photocages ZinCast-2 with a N-[2-(pyridine-2-yl)ethyl]-N-(pyridine-2-ylmethyl)aniline (5,6-chelate ring) and ZinCast-3 with a N,N-bis[2-(pyridine-2-yl)ethyl]aniline (6,6-chelate ring) were synthesized for comparative studies.

Super-hydrophobic, highly adhesive, polydimethylsiloxane (PDMS) surfaces.

Super-hydrophobic surfaces have been fabricated by casting polydimethylsiloxane (PDMS) on a textured substrate of known surface topography, and were characterized using contact angle, atomic force microscopy, surface free energy calculations, and adhesion measurements. The resulting PDMS has a micro-textured surface with a static contact angle of 153.5° and a hysteresis of 27° when using de-ionized water.

An evaluation of tactical combat casualty care interventions in a combat environment.

Background: Tactical combat casualty care (TCCC) is a system of prehospital trauma care designed for the combat environment. Although widely adopted, very few studies have reported on how TCCC interventions are actually delivered on the battlefield, from a quality of care perspective.

Study Design: This was a prospective study of all trauma patients treated at the Role 3 multinational medical unit (MMU) at Kandahar Airfield Base from February 7, 2006 to May 30, 2006.

An evaluation of tactical combat casualty care interventions in a combat environment.

Background: Tactical combat casualty care (TCCC) is a system of prehospital trauma care designed for the combat environment. Although widely adopted, very few studies have reported on how TCCC interventions are actually delivered on the battlefield, from a quality of care perspective.

Study Design: This was a prospective study of all trauma patients treated at the Role 3 multinational medical unit (MMU) at Kandahar Airfield Base from February 7, 2006 to May 30, 2006.

Photocurrent generation in noncovalently assembled multilayered thin films.

Multilayered photocurrent generating thin films were fabricated by templated noncovalent assembly via stepwise assembly of molecular components. Each of films I-IV contained an underlying self-assembled monolayer (SAM) consisting of an alkanethiol linked covalently to a 2,6-dicarboxypyridine ligand that served as a binding site for attaching additional molecular components. The SAM subsequently was functionalized by sequential deposition of Cu(II), Co(II), or Fe(III) ions followed by a variety of substituted 2,6-dicarboxypyridine ligands as a means to incorporate one or more layers of pyrene chromophores into the film.

Role of aerosil dispersion on the activated kinetics of the LC1-xSilx system.

This study explores the role of aerosil dispersion on activated phase transitions of bulk octylcyanobiphenyl (8CB) liquid crystals by performing heating rate-dependent experiments. Differential scanning calorimetry (DSC) was used at various heating ramp rates in order to probe the activated phase dynamics of the system. The system, LC1-xSilx, was prepared by mixing aerosil nanoparticles (7 nm in diameter) in the bulk 8CB by the solvent dispersion method (SDM).

Thermodynamics of activated phase transitions of 8CB: DSC and MC calorimetry.

The present paper reports the heating rate effect on the phase transitions of a pure liquid crystal octylcyanobiphenyl (8CB) with use of Differential Scanning Calorimetry (DSC) and Modulation Calorimetry (MC) techniques. The DSC runs were taken at various temperature ramp rates from 20 to 0.5 K/min for heating and cooling scans.

Non-covalent assembly of a photoswitchable surface.

A noncovalently bound multilayered thin film in which individual layers are linked by metal ligand interactions undergoes a photochemically initiated permanent change in surface wettability. The film consists of three separate layers: a SAM on gold of 4-[(10-mercaptodecyl)oxy]pyridine-2,6-dicarboxylic acid, a layer of Cu(II) ions that are deposited onto the SAM and bind symmetrically in the site provided by the two carboxylate groups and the pyridyl nitrogen atom, and a layer of cis-2,2'-dipyridylethylene, which caps the Cu(II) layer by complexation through both pyridyl nitrogen atoms (Film I). Photoexcitation of the film in chloroform at 300 nm leads to substantial cis-trans isomerization as indicated by conductivity, impedance, grazing incidence IR, and contact angle measurements.

A non-covalent strategy for the assembly of supramolecular photocurrent-generating systems.

Three photocurrent-generating thin films were assembled on gold surfaces. SAM I was constructed from molecules consisting of an alkyl disulfide group linked covalently to a 12-residue helical peptide and terminated with an alanine residue containing a pyrene chromophore. SAM I served as a benchmark for multilayered films II and III in photocurrent generation experiments.

Strong N-H⋅⋅⋅O Hydrogen Bonding in a Model Compound of the Catalytic Triad in Serine Proteases.

Low-barrier hydrogen bond (LBHB) involvement in enzyme catalysis is examined by analysis of experimental nuclear and electron densities of a model compound for the catalytic triad in serine proteases (shown schematically), which is based on a cocrystal of betaine, imidazole, and picric acid. The three short, strong N-H⋅⋅⋅O hydrogen bonds in the structure have varying degrees of covalent bonding contributions suggesting a gradual transition to the LBHB situation.