We have measured photoelectron angular distributions in the molecular frame (MF-PADs) for O 1s photoemission from CO 2 , using photoelectron-O + -CO + coincidence momentum imaging. Results for the molecular axis at 0, 45 and 90• to the electric vector of the light are reported. The major features of the MF-PADs are fairly well reproduced by calculations employing a relaxed-core Hartree-Fock approach. Weak asymmetric features are seen through a plane perpendicular to the molecular axis and attributed to symmetry lowering by anti-symmetric stretching motion.(Some figures in this article are in colour only in the electronic version) Photoelectron angular distributions in the molecular frame (MF-PADs) have been investigated extensively for K-shell photoemission from the diatomic molecules CO and N 2 [1-9]. The MF-PADs for molecules aligned parallel to the electric vector of the linearly polarized light exhibit rich structure in regions of shape resonances and provide a dynamical window on the underlying partial-wave composition of the photoelectron as it scatters off the anisotropic potential of the ion. It is worth noting that the observed MF-PADs for N 2 display reflection

From an extract of a Streptomyces culture, we identified and purified a novel compound, NP-06, which is active against human immunodeficiency virus (HIV) in vitro. Analyses indicate that NP-06 is a hydrophobic 21-mer oligopeptide, N terminally cyclized through the side chain of Asp-9, containing two intramolecular cystine linkages with a molecular weight of 2,163.4. The 50% inhibitory concentrations were 2.8 and 1.3 M when NP-06 was tested for in vitro anti-HIV-1 activity in ATH8 cells and phytohemagglutinin-activated peripheral blood mononuclear cells, respectively. NP-06 appears to block the early stage of HIV-1 infection, most likely at the stage of virus-cell fusion.We prepared ϳ9,000 different extracts from solitary colonies obtained by incubation of bacterial samples from various sources, including soil specimens collected in Japan. The methanol extract from each bacterial colony was tested for antihuman immunodeficiency virus type 1 (HIV-1) activity by using a colorimetric assay employing a tetrazolium salt (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide [MTT]) and MT4 cells (9). A crude extract of strain SKH-2344 (FERMP-14239), a Streptomyces species strain isolated from soil collected in Yamaguchi, was found to be active against HIV-1 (data not shown). The strain was then grown in culture medium and subjected to fermentation. On day 5 of fermentation, 20 liters of culture broth medium was centrifuged, and the supernatant was concentrated in vacuo to yield a paste, which was resuspended in 1 liter of methanol for 12 h. The methanol extract was then filtered and concentrated to yield a pale yellow oily specimen (fraction A). The pellet (the mycelium) was homogenized in 10 liters of methanol with agitation for 12 h, and the filtered solution was concentrated in vacuo to yield a yellow oily specimen (fraction B). Fractions A and B were combined, dissolved in water-saturated butanol, and concentrated in vacuo. The extract was column chromatographed on silica gel with ethyl acetate-methanol-water (10:5:0.25) and purified (Ͼ99%) by high-performance liquid chromatography with CH 3 CN-H 2 O-CF 3 COOH (38:62:0.1) to yield a white powder (100 mg), designated NP-06.Amino acid analysis of the NP-06 hydrolysate revealed the presence of one residue each of Ser, Ile, Leu, and Tyr; two residues each of Phe, Ala, Val, and Asp; and four residues each of Cys and Gly, although whether the two Asp residues represented Asn was to be confirmed. Thin-layer chromatography analysis of the hydrazine hydrolysate of NP-06 revealed that the C terminus was Trp. NP-06 could not be sequenced by the Edman degradation method, although the physical properties of NP-06 showed that it was a peptide. Therefore, nuclear magnetic resonance (NMR) spectroscopy was used to determine the amino acid sequence of NP-06. Inspection of the relayed signals arising from the amide resonances in a homonuclear Hartmann-Hahn spectroscopy experiment revealed the presence of 21-amino-acid spin systems. One Leu, one Ile, one Ser, two Val, two Ala,...

Measurements of photoelectron angular distributions for carbon K-shell ionization of fixed-in-space CO 2 molecules with the molecular axis oriented along, perpendicular and at 45• to the electric vector of the light are reported. The major features of these measured spectra are fairly well reproduced by calculations employing a relaxed-core Hartree-Fock approach. In contrast to the angular distribution for K-shell ionization of N 2 , which exhibits a rich structure dominated by the f-wave (l = 3) at the shape resonance, the angular distribution for carbon K-shell photoionization of CO 2 is quite unstructured over the entire observed range across the shape resonance.(Some figures in this article are in colour only in the electronic version)There have been significant advances in the development of techniques for measuring angular distributions of photoelectrons from fixed-in-space molecules (see, for example, [1][2][3]). To date these techniques have been extensively used to study the angular distributions of K-shell photoelectrons emitted from the diatomics CO and N 2 (see, for example, [1][2][3][4][5][6][7]). The measurements have confirmed the rich dynamical structure of photoelectron angular distributions for fixed-in-space molecules predicted in the seminal studies of Dehmer and

Satellite bands accompanying the C 1s photoline for the CO2 molecule parallel to the electric vector of the incident radiation E are found to be more intense than those for CO2 perpendicular to E in the shape resonance region. This indicates that multielectron excitations are caused in part by the interaction of the outgoing C 1s photoelectron with the valence electrons. The photoelectron-impact valence excitations couple with the C 1s single-hole ionization and distort the shape resonance significantly. We assign the broad resonance at approximately 312 eV to a distorted Sigma(u) shape resonance.