Heterodyne measurements of hot bands and isotopic transitions of N2O near 7.8 µm

Heterodyne frequency measurements are reported for absorption transitions of N₂O in the frequency range from 1257 to 1335 cm^?1. The measurements use a CO laser as a transfer oscillator whose frequency is measured directly against combinations of frequencies of two stabilized CO₂ lasers whose frequencies are well known. A tunable diode laser is locked to the N₂O absorption feature and the frequency difference is measured between the diode laser and the CO laser. Thev ₃ fundamental bands of the¹⁵N¹⁴N¹⁶O and¹⁴N¹⁵N¹⁶O isotopes are reported. Measurements are also given for the 00⁰2–00⁰1, 02⁰1–02⁰0, and 02²1–02²0 vibrational transitions of N₂O. A table of frequencies is given for the 00⁰2–00⁰0 band near 2560 cm^?1 based on these and earlier measurements.     

Selection of the cis and trans phosph(III)azane macrocycles [{P(mu-NtBu)}2(1-Y-2-NH-C6H4)]2(Y=O, S)

The 1 : 1 reactions of [ClP(mu-NtBu)]2 with the difunctional aromatic amines 1,2-1-YH-2-NH2-C6H4 in the presence of Et3N give the dimeric phosph(III)azane macrocycles [{P(mu-NtBu)2(1-Y-2-HN-C6H4)]2, predominantly as the cis isomer in the case of Y=O (1.cis) and as the trans isomer for Y=S (2.trans). Model M.O. calculations suggest that the selection of the cis and trans isomers is not thermodynamically controlled. The alternative isomers 1.trans and 2.cis are generated exclusively by the deprotonation of the model intermediates [(1-Y-2-NH2-C6H4)P(mu-NtBu)]2[Y=O (3), S (4)] with nBuLi followed by cyclisation with [ClP(mu-NtBu)]2. The solid-state structures of 1.cis/trans(50 : 50), 2.cis, 3 and 4 are reported.     

Exo-metal coordination by a tricyclic [(P(mu-N-2-NC5H4))2(mu-O)]2 dimer in [(P(mu-N-2-NC5H4))2(mu-O)]2(CuCl x (C5H5N)2)4 (2-NC5H4 = 2-pyridyl, C5H5N = pyridine)

The in situ reaction of the phosphazane dimer [CIP(mu-N-2-NC5H4)]2 (2) with CuCl in the presence of CsH5N/H2O gives the title complex [(P(mu-N-2-NC5H4))2(mu-O)]2(CuCl x (C5H5N)2)4 (1), containing a tricyclic [(P(mu-N-2-NC5H4))2(mu-O)]2 ligand which is isoelectronic with species of the type [(P(mu-NR))2NR]2.     

Synthesis and structure of the calixarene-like phosph(III)azane macrocycle [{P(mu-N(t)Bu)}2{1,5-(NH)2C10H6}]3

The reaction of [ClP(mu-NtBu)]2 with 1,5-diamino-naphthalene [1,5-(NH2)2C10H6] in Et3N-thf gives the trimeric macrocycle [{P(mu-NtBu)}2{1,5-(NH)2C10H6}]3(1); the X-ray structure of the toluene solvate 1.3toluene reveals a cone-shaped (calixarene-like) arrangement in which toluene guest molecules are trapped within the cavity.     

Vibrational spectra and conformational behavior of benzyl fluoride

Infrared and Raman spectra have been obtained for benzyl fluoride and a vibrational assignment has been made. The spectra indicate the presence of a large number of conformers that differ only in the orientation of the C-F bond, as a result of free or nearly free internal rotation.     

Application of total selective solvent extraction of germanium,phosphorus and silicon to the simultaneous determination of arsenic,germanium, phosphorus and silicon

A simple rapid, accurate, and reliable method of simultaneous determination of arsenic, germanium, phosphorus, and silicon is reported. The method involves first, the determination of germanium as its phenlfluorone complex and its selective extraction with isoamyl alcohol. Phosphorus is next determined as its heteropoly blue after selective extraction of phosphomolybdic acid by isobutyl acetate at pH 1.0-0.8 and its direct reduction in this solvent. Silicon is then determined after its extraction as silicomolybdic acid by isooctyl alcohol at pH < 0.4 and direct reduction in the solvent phase. Finally, arsenic is determined in the remaining aqueous phase after reduction to its heteropoly blue.     

5α-24-Norcholestan-3β-ol and (24Z)-Stigmasta-5,7,24(28)-trien-3β-ol,Two New Marine Sterols from the Pacific Sponges Terpios zeteki and Dysidea herbacea

The steroidal components of 2 marine sponges, Terpios zeteki (from Hawaii) and Dysidea herbacea (from Australia) were fractionated through a combination of chromatographic methods, including reversed phase HPLC., and were analyzed by a combination of physical methods, including high resolution GC.-MS. and 360 MHz ¹H-NMR. T. zeteki contains 6 conventional 5α-stanols which comprise 91% of the sterol mixture, and traces (0.5%) of a new C₂₆ sterol, 5α-24-norcholestan-3β-ol. Minor amounts of conventional Δ⁵-sterols (6.5%) and of a single Δ⁴-3-ketosteroid (1.5%) were also present. In contrast, the Australian sponge (D. herbacea) contains 3 Δ^5,7-sterols which comprise 1.5% of the sterol mixture, and one new C₂₉ sterol, (24 Z)-stigmasta-5,7,24(28)-trien-3β-ol, as the major component (75%). In addition, minor amounts of conventional 5α-stanols (0.5%), Δ⁵-sterols (5%) and 5α-Δ⁷-sterols (18%) were present in this complex sterol mixture. The possible dietary or endosymbiotic origins of these sterols are discussed.     

The structure of di-μ-pentafluorobenzoatobis[bis(pentafluorophenyl)(triphenylphosphine oxide)thallium(iii)]

An X-ray crystallographic study has shown that the complex (C₆H₅)₂TlO₂CC₆F₅(OPPh₃) has a dimeric structure with unsymmetrical pentafluorobenzoate bridging (TlO 2.531 and 2.789 Å) but an exact crystallographic centre of symmetry. The pentafluorobenzoate groups are also unsymmetrically chelated to thallium (TlO 2.389 and 2.531 Å.), which overall has irregular six coordination.     

Electrospray ionization mass spectrometry studies of noncovalent myosin VI complexes reveal a new specific calmodulin binding site

Among the myosin superfamily, myosin VI differs from all others by a reverse directionality and a particular motility. Little structural information is available for myosin VI. It is known that it binds one calmodulin (CaM) by means of a single "IQ motif" and that myosin VI contains a specific insert located at the junction between the motor domain (MD) and the lever arm, likely to play a critical role for the unusual motility previously observed. Electrospray ionization mass spectrometry (MS) was used to determine the CaM and Ca2+ stoichiometries in several myosin VI constructs. In particular, the experimental conditions required for the observation of multiprotein/Ca2+ noncovalent assemblies are detailed for two truncated MD constructs (less than 20 kDa) and for three full MD constructs (more than 90 KDa). The specificity of the detected stoichiometries is discussed for each construct and the resolving power of Time of Flight mass spectrometry is stressed, in particular for the detection of metal ions binding to high molecular weight complexes. MS reveals a new CaM binding site for myosin VI and highlights a different behavior for the five myosin VI constructs versus Ca2+ binding. In addition to these stoichiometry based experiments, gas-phase dissociation analyses on intact complexes are described. They reveal that Ca2+ transfer between protein partners occurs during the dissociation process for one construct with a full MD. Charge-transfer and dissociation behavior has allowed to draw structural assumptions for the interaction of the MD with the CaM N-terminal lobe.