Charge‐assisted hydrogen bonding in salts of 2‐amino‐1H‐benzimidazole with 3‐phenylpropynoic acid and oct‐2‐ynoic acid

The 100 K structures of two salts, namely 2‐amino‐1H‐benzimidazolium 3‐phenylpropynoate, C₇H₈N₃⁺·C₉H₅O₂⁻, (I), and 2‐amino‐1H‐benzimidazolium oct‐2‐ynoate, C₇H₈N₃⁺·C₈H₁₁O₂⁻, (II), both have monoclinic symmetry (space group P2₁/c) and display N—H...O hydrogen bonding. Both structures show packing with corrugated sheets of hydrogen‐bonded molecules lying parallel to the [001] direction. Two hydrogen‐bonded ring motifs can be identified and described with graph sets R²₂(8) and R⁴₄(16), respectively, in both (I) and (II). Computational chemistry calculations performed on both compounds show that the hydrogen‐bonded ion pairs are more energetically favourable in the crystal structure than their hydrogen–bonded neutral molecule counterparts.     

Separation and recovery of intact gold-virus complex by agarose electrophoresis and electroelution: application to the purification of cowpea mosaic virus and colloidal gold complex

Colloidal gold has been coupled to a mutant cowpea mosaic virus (CPMV), which contains 60 cysteine residues on the surface. A purification process was developed to separate the gold-containing viral nanoblocks (VNBs) from the free gold. Agarose electrophoresis was utilized to separate the mixture followed by electroelution of the desired sample to recover the intact virus. Mobility of Au-VNB and free colloidal gold was facilitated by the addition of thioctic acid (TA). 30% of the gold-containing virus was recovered after electroelution as determined by absorbance measurements. Histogram analysis of transmission electron microscopy (TEM) images demonstrated the efficient separation of gold-containing virus from free gold. TEM and scanning electron microscopy (SEM) images indicated that the virus was recovered intact. Monodisperse spherical particles of nominal size of 45 nm were observed under SEM.     

Pentane‐1,5‐diaminium dibromide

The crystal structure of the title salt, C₅H₁₆N₂²⁺·2Br⁻, with Z = 12 and more unusually Z′ = 3, forms part of a small group of crystal structures in the Cambridge Structural Database that are ammonium bromide salts. One of the diaminium cation chains in the asymmetric unit exhibits positional disorder, which was modelled using a suitable disorder model. This compound also exhibits organic–inorganic layering in its packing arrangement that is typical of this class of compound. An extensive complex three‐dimensional hydrogen‐bonding network is also identified. The hydrogen bonds evident in this crystal structure were identified as being most likely strong charge‐assisted hydrogen bonds.     

Reactivity trends of cobalt(III) complexes towards various amino acids based on the properties of the amino acid alkyl chains

The reactivity of the cobalt(III) complexes dichlorido[tris(2‐aminoethyl)amine]cobalt(III) chloride, [CoCl₂(tren)]Cl, and dichlorido(triethylenetetramine)cobalt(III) chloride, [CoCl₂(trien)]Cl, towards different amino acids (l ‐proline, l ‐asparagine, l ‐histidine and l ‐aspartic acid) was explored in detail. This study presents the crystal structures of three amino acidate cobalt(III) complexes, namely, (l ‐prolinato‐κ²N,O)[tris(2‐aminoethyl)amine‐κ⁴N,N′,N′′,N′′′]cobalt(III) diiodide monohydrate, [Co(C₅H₈NO₂)(C₆H₁₈N₄)]I₂·H₂O, I , (l ‐asparaginato‐κ²N,O)[tris(2‐aminoethyl)amine‐κ⁴N,N′,N′′,N′′′]cobalt(III) chloride perchlorate, [Co(C₄H₇N₂O₃)(C₆H₁₈N₄)](Cl)(ClO₄), II , and (l ‐prolinato‐κ²N,O)(triethylenetetramine‐κ⁴N,N′,N′′,N′′′)cobalt(III) chloride perchlorate, [Co(C₄H₇N₂O₃)(C₆H₁₈N₄)](Cl)(ClO₄), V . The syntheses of the complexes were followed by characterization using UV–Vis spectroscopy of the reaction mixtures and the initial rates of reaction were obtained by calculating the slopes of absorbance versus time plots. The initial rates suggest a stronger reactivity and hence greater affinity of the cobalt(III) complexes towards basic amino acids. The biocompatibility of the complexes was also assessed by evaluating the cytotoxicity of the complexes on cultured normal human fibroblast cells (WS1) in vitro. The compounds were found to be nontoxic after 24 h of incubation at concentrations up to 25 mM.     

Miniaturized capillary isoelectric focusing in plastic microfluidic devices

We report the demonstration of miniaturized capillary isoelectric focusing (CIEF) in plastic microfluidic devices. Conventional CIEF technique was adapted to the microfluidic devices to separate proteins and to detect protein-protein interactions. Both acidic and basic proteins with isoelectric points (pI) ranging from 5.4 to 11.0 were rapidly focused, mobilized, and detected in a 1.2 cm long channel (50 microm deep x 120 microm wide) with a total analysis time of 150 s. In a device with a focusing distance of 4.7 cm, the separation efficiency for a basic protein, lysozyme, was achieved as high as 1.5 x 10(5) plates, corresponding to 3.2 million plates per meter. We also experimentally confirmed that IEF resolution is essentially independent of focusing length when the applied voltage is kept the same and within a range that it does not cause Joule heating. Further, we demonstrated the use of miniaturized CIEF to study the interactions between two pairs of proteins, immunoglobulin G (IgG) with protein G and anti-six histidine (anti-6xHis) with 6xHis-tagged green fluorescent protein (GFP). Using this approach, protein-protein interactions can be detected for as little as 50 fmol of protein. We believe miniaturized CIEF is useful for studying protein-protein interactions when there is a difference in pI between a protein-protein complex and its constitutent proteins.     

Temporal dynamics of receptor-induced apoptosis in an affinity microdevice

The temporal dynamics of Fas-induced apoptosis is elucidated. Jurkat cells are captured on the affinity surface of a microdevice coated with anti-CD95, an antibody known to induce apoptosis in cells via the extrinsic (caspase 8) pathway. The timing of apoptosis induction is controlled by the binding of the cells to the surface. Once bound, the cells are continuously stained with the caspase probe, l-bisaspartic acid rhodamine 110 (D₂R), and the fluorescence of the cells was monitored for 6 h by light microscopy. This approach normalizes the temporal dynamics for each cell, as the binding event is also the start of apoptosis. In addition to providing the number of apoptotic cells over time, the fluorescence of individual cells can be monitored, providing information about the timing of caspase activity in each cell. The rate of caspase cleavage of D₂R in each cell is also measured and shows good agreement between the cells in a given population. The effects of the caspase inhibitor, z-VAD-FMK, on the timing of caspase activity are also investigated and are shown to dramatically slow the apoptotic process. In the future, other caspase probes could be used to provide additional information about the temporal dynamics of caspase activation. Additional techniques, such as fluorescence correlation spectroscopy, can be coupled to these methods to provide faster temporal response and help to elucidate the heterogeneity of the apoptosis process.     

Enzyme‐Mediated Site‐Specific Bioconjugation of Metal Complexes to Proteins: Sortase‐Mediated Coupling of Copper‐64 to a Single‐Chain Antibody

The enzyme‐mediated site‐specific bioconjugation of a radioactive metal complex to a single‐chain antibody using the transpeptidase sortase A is reported. Cage amine sarcophagine ligands that were designed to function as substrates for the sortase A mediated bioconjugation to antibodies were synthesized and enzymatically conjugated to a single‐chain variable fragment. The antibody fragment scFv_anti‐LIBS targets ligand‐induced binding sites (LIBS) on the glycoprotein receptor GPIIb/IIIa, which is present on activated platelets. The immunoconjugates were radiolabeled with the positron‐emitting isotope ⁶⁴Cu. The new radiolabeled conjugates were shown to bind selectively to activated platelets. The diagnostic potential of the most promising conjugate was demonstrated in an in vivo model of carotid artery thrombosis using positron emission tomography. This approach gives homogeneous products through site‐specific enzyme‐mediated conjugation and should be broadly applicable to other metal complexes and proteins.     

Energetic propane‐1,3‐diaminium and butane‐1,4‐diaminium salts of N,N′‐dinitroethylenediazanide: syntheses,crystal structures and thermal properties

The acidity of the amine H atoms and the consequent salt formation ability of ethylenedinitramine (EDNA) were analyzed in an attempt to improve the thermal stability of EDNA. Two short‐chain alkanediamine bases, namely propane‐1,3‐diamine and butane‐1,4‐diamine, were chosen for this purpose. The resulting salts, namely propane‐1,3‐diaminium N,N′‐dinitroethylenediazanide, C₃H₁₂N₂²⁺·C₂H₄N₄O₄^2?, and butane‐1,4‐diaminium N,N′‐dinitroethylenediazanide, C₄H₁₄N₂²⁺·C₂H₄N₄O₄^2?, crystallize in the orthorhombic space group Pbca and the monoclinic space group P2₁/n, respectively. The resulting salts display extensive hydrogen‐bonding networks because of the presence of ammonium and diazenide ions in the crystal lattice. This results in an enhanced thermal stability and raises the thermal decomposition temperatures to 202 and 221 °C compared to 180 °C for EDNA. The extensive hydrogen bonding present also plays a crucial role in lowering the sensitivity to impact of these energetic salts.     

Community engagement and informed consent in the International HapMap project

The International HapMap Consortium has developed the HapMap, a resource that describes the common patterns of human genetic variation (haplotypes). Processes of community/public consultation and individual informed consent were implemented in each locality where samples were collected to understand and attempt to address both individual and group concerns. Perceptions about the research varied, but we detected no critical opposition to the research. Incorporating community input and responding to concerns raised was challenging. However, the experience suggests that approaching genetic variation research in a spirit of openness can help investigators better appreciate the views of the communities whose samples they seek to study and help communities become more engaged in the science.