Cooperative spin transition in a lipid layer like system

A novel iron(II) mononuclear spin transition complex [FeL(py)(2)] displays an abrupt spin transition around 225 K accompanied by a very wide thermal hysteresis loop (～50 K) that spreads out over 100 K. Crystal structure analysis in both low-spin and high-spin states reveals a lipid layer-like arrangement of the complex molecules and provides insights into the spin switching mechanism.     

Noninvasive imaging of cell death using an Hsp90 ligand

Cell death plays a central role in normal physiology and in disease. Common to apoptotic and necrotic cell death is the eventual loss of plasma membrane integrity. We have produced a small organoarsenical compound, 4-(N-(S-glutathionylacetyl)amino)phenylarsonous acid, that rapidly accumulates in the cytosol of dying cells coincident with loss of plasma membrane integrity. The compound is retained in the cytosol predominantly by covalent reaction with the 90 kDa heat shock protein (Hsp90), the most abundant molecular chaperone of the eukaryotic cytoplasm. The organoarsenical was tagged with either optical or radioisotope reporting groups to image cell death in cultured cells and in murine tumors ex vivo and in situ. Tumor cell death in mice was noninvasively imaged by SPECT/CT using an (111)In-tagged compound. This versatile compound should enable the imaging of cell death in most experimental settings.     

Synthesis of Quinoline-Based Thieno-Seleno-Phenylquinazolinones

The synthesis of quinoline-substituted phenylquinazolinones containing sulfur and selenium is described. These molecules were isolated from a series of reactions of 2-phenyl-4H-3,1-benzoxazin-4-one with 2-chloro, 2-thieno, and 2-selenoquinoline-3-carbaldehyde hydrazones. The structure of the isolated compounds has been elucidated on the basis of IR, ¹ H NMR, mass spectral, and elemental analysis data.     

Optical Modulation of Azobenzene‐Modified Peptide for Gold Surface Binding

The ability to precisely and remotely modulate reversible binding interactions between biomolecules and abiotic surfaces is appealing for many applications. To achieve this level of control, an azobenzene‐based optical switch is added to nanoparticle‐binding peptides in order to switch peptide conformation and attenuate binding affinity to gold surfaces via binding and dissociation of peptides.     

Tandem mass spectrometry of kahalalides: identification of two new cyclic depsipeptides, kahalalide R and S from Elysia grandifolia

Spectra obtained using electrospray ionization mass spectrometry (ESI-MS) of the mollusk Elysia grandifolia showed a cluster of molecular ion peaks centered at a molecular mass of 1478 Da (kahalalide F, an anticancer agent). Two new molecules, kahalalide R (m/z 1464) and S (m/z 1492) were characterized using tandem mass spectrometry. The mass differences of 14 Da suggest that they are homologous molecules. In addition, previously identified kahalalide D and kahalalide G are also reported. However, the ESI-MS of the mollusk's algal diet Bryopsis plumosa showed the presence of only kahalalide F. The amino acid sequences of kahalalide R and S are proposed using collision-induced dissociation (CID) experiments of singly and doubly charged molecular ions and by comparison with the amino acid sequence of kahalalide F. The pathway is presented for the loss of amino acid residues in kahalalide F. It is observed that there is sequential loss of amino acids in the linear peptide chain, but in the cyclic part the ring opens at the amide bond rather than at the lactone linkage, and the loss of amino acid residues is not sequential. The CID experiment of the alkali-metal-cationized molecular ions shows that the sodium and potassium ions coordinate to the amide nitrogen/oxygen in the linear peptide chain of the molecule and not to the lactone oxygen of the lactone. In the case of kahalalide D, CID of the protonated peptide opens the depsipeptide ring to form a linear peptide with acylium ion, and fragment ion signals indicate losses of amino acids in sequential order. In this study, tandem mass spectrometry has provided the detailed information required to fully characterize the new peptides.     

Synthesis and spectroscopic characterization of transition metal complexes derived from novel benzofuran hydrazone chelating ligand: DNA cleavage studies and antimicrobial activity with special emphasis on antituberculosis

Mononuclear divalent complexes of Co, Ni, Cu and Zn derived from a benzofuran‐based novel hydrazone tridentate ligand were synthesized and characterized using various spectroscopic methods. Elemental analysis reveals that the metal‐to‐ligand ratio is 1:2 which is supported by mass spectrometry results. Conductivity measurements suggest that all the complexes are non‐electrolytic in nature. The ligand and complexes were evaluated for their antimicrobial potency. Bioassay of all hydrazone chelates shows enhanced activity as compared to that of the ligand. The complex with cobalt ion as the metal centre shows better activity against fungi than the standard. Also, ligand and complexes were screened for antituberculosis activity; some analogues (Ni, Cu, Zn) are eight times more active than the standard. Both ligand and complexes show moderate ability to cleave calf thymus DNA. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of sodium metasilicate on natural flotability of coal

The effect of the quantity of sodium metasilicate and conditioning time in one set of experiments, and the effect of the solution concentration of sodium metasilicate, added at the same dosage and conditioning time to coal slurry, on flotability of a typical Indian coal in another set of experiments are studied. Two sets of 3² full factorial experiments are carried out to assess the effects of the aforementioned variables. The generated data are analyzed quantitatively and explained qualitatively. At 0.1% (w/v) solution concentration of solution added (0.02 g/kg) and 8 min conditioning time, sodium metasilicate acted as activator for kaolinite, whereas at 1.0% (w/v) solution concentration (0.2 g/kg), it acted as dispersant. The best observed condition of depressant is obtained at an added concentration of 10.0% (w/v, 0.2 g/kg) and 8 min conditioning time. The desired effect of the sodium metasilicate can be achieved by controlling its quantity, solution concentration added, and conditioning time.     

Detection of OH on photolysis of styrene oxide at 193 nm in gas phase

Photodissociation of styrene oxide at 193 nm in gas phase generates OH, as detected by laser-induced fluorescence technique. Under similar conditions, OH was not observed from ethylene and propylene oxides, primarily because of their low absorption cross-sections at 193 nm. Mechanism of OH formation involves first opening of the three-membered ring from the ground electronic state via cleavage of either of two CO bonds, followed by isomerization to enolic forms of phenylacetaldehyde and acetophenone, and finally scission of the COH bond of enols. Ab initio molecular orbital calculations support the proposed mechanism.     

Simple electro-optic technique to generate temporally flat-top laser pulses

A simple technique is presented to generate temporally flat-top shaped laser pulses using electro-optic modulator (Pockels cell). It involves splitting of input laser pulse into two halves of equal intensity and then stacking together with appropriate optical delay to get a temporally flat-top laser pulse. It also allows generation of other pulse shapes by varying the relative intensity, delay, and phase between two halves of the input laser pulse. Temporally flat-top laser pulses of duration ~ 9 ns have been generated using ~ 7 ns duration incident laser pulses from a flash lamp pumped Q-switched Nd:glass laser oscillator. The rise and fall-time of the shaped pulse is limited by speed of electro-optic switch (Pockels cell), which is ~ 2 ns in the present case.