Angular-distribution He(I) /Ne(I) /Ar(I) photoelectron spectra of unsaturated hydrocarbons

The energy dependence of the anisotropy parameters of the π- and selected σ-bands of ethylene, 1,3-butadiene, benzene, cyclohexene, norbornadiene, 1,3-and 1,4-cyclohexadiene has been determined in the low energy region. Whereas the behaviour of the σ-bands is much less uniform, all π-band β-values decrease with decreasing energy towards similar threshold values. Strong intra-band energy dependencies have been observed for both π and σ orbitals, while in the multiple π-orbital molecules there is a symmetry-specific contribution to the π β-values. Marked intensity variations are observed among the ethylene, butadiene and benzene bands, and the anisotropy-parameter-based assignment of symmetric character to the 1,4-cyclohexadiene first band is confirmed.     

Photoelectron spectroscopic assignment of the p-states of benzenethiol

He(I) anisotropy parameters and He(I)/He(II) relative band intensities have been determined and utilised to make a complete assignment of the benzenethiol p-electron-region photoelectron spectrum. The major S-atom contribution appears more so in the third band than in the first.     

Total synthesis of camptotheein. I. Synthesis of ethyl 8-(α-chlorobutyryloxymethyl)-7,9-dioxo-7,8,9,11 -tetrahydroindolizino[ 1,2-a]quinoline-8-carboxylate and related tetracyclic compounds

A practical synthesis of the 8-ethoxycarlbonyl-8-hydroxymethyl-7,9-dioxo-7,8,9,11-tetrahydro-indolizino[ 1,2-a]quinoline ester of α-chlorohutyric acid, a tetracyclic intermediate for the total synthesis of the alkaloid camptothecin, was prepared from the anil of o-aminohenzaldehyde in six steps. Preparative procedures of other related tetracyclic compounds are also reported.     

High spin band structures in104Cd

High spin states in¹⁰⁴Cd have been investigated by means of heavy ion induced reactions using the Nordball detector array. The level scheme constructed from -coincidences is dominated by three band structures. The positive parity band shows no rotational like energy spacing. It is thus understood mostly in terms of quasiparticle excitations with vd_5/2, vg_7/2 andg_9/2 configurations. The collective properties of the negative parity bands are more pronounced. These bands are most likely due to v(h_11/2,d_5/2) and v(h_11/2,g_7/2) structures.     

In-beam study of the doubly-odd nucleus 61 140 Pm79 above the 8− β +-decaying isomer

An in-beamγ-ray study performed with the¹¹⁴Cd(³⁰Si,p 3n) reaction has established the structure of theN=79 nucleus¹⁴⁰Pm. States up toI=(20)? and 5.5 MeV excitation energy have been recognized above the 5.95 m isomeric state which we identify, from the GT decay to¹⁴⁰Nd, as the 8^? member of the (πd ₅ ^2/?1 vh ₁₁ ^2/?1 ) multiplet, changing the present 7^? assignment. The low energy part of the level scheme is discussed in terms of the coupling of the valence holes in respect to theZ=64,N=82 shell closure. A new 8⁺ isomeric state witht _1/2=1 _?0.5 ⁺¹ ns has been observed, having most likely a (πh _11/2 vh _11/2 ^-1 )₈ configuration.     

High spin states in131Ce

Gamma ray spectra from the¹¹⁷Sn(¹⁸O,4n)¹³¹ Ce reaction have been studied with the NORDBALL array of 15 Compton-suppressed Ge detectors. States up to I=51/2 , E8 MeV are populated. Observed bands are interpreted in terms of quasiparticle configurations.     

Editing of H2BC NMR spectra

New versions of the H2BC pulse sequence (Nyberg NT, Duus JØ, Sørensen OW. J. Am. Chem. Soc. 2005; 127: 6154) that edit into two subspectra according to the number of protons attached to ¹³C nuclei being odd or even are introduced. These sequences can be useful for resolving spectral overlap, which is demonstrated on the molecule prednisolone [(11 β)‐11,17,21‐trihydroxypregna‐1,4‐diene‐3,20‐dione] Copyright © 2005 John Wiley & Sons, Ltd.     

Neuropeptide conversion to bioactive fragments--an important pathway in neuromodulation

Biosynthetic pathways for the formation of neuroactive peptides and the processes for their inactivation include several enzymatic steps. In addition to enzymatic processing and degradation, several neuropeptides have been shown to undergo enzymatic conversion to fragments with retained or modified biological activity. This has most clearly been demonstrated for e.g. opioid peptides, tachykinins, calcitonin gene-related peptide (CGRP) as well as for peptides belonging to the renin-angiotensin system. Sometimes the released fragment shares the activity of the parent compound. However, in many cases the conversion reaction is linked to a change in the receptor activation profile, i.e. the generated fragment acts on and stimulates a receptor not recognized by the parent peptide. This review will describe the characteristics of certain neuropeptide fragments having the ability to modify the biological action of the peptide from which they are derived. Focus will be directed to the tachykinins, the opioid peptides, angiotensins as well as to CGRP, bradykinin and nociceptin. The kappa opioid receptor selective opioid peptide, dynorphin, recognized for its ability to produce dysphoria, is converted to the delta opioid receptor agonist Leu-enkephalin, with euphoric properties. The tachykinins, typified by substance P (SP), is converted to the bioactive fragment SP(1-7), a heptapeptide mimicking some but opposing other effects of the parent peptide. The bioactive angiotensin II, known to bind to and stimulate the AT-1 and AT-2 receptors, is converted to angiotensin IV (i.e. angiotensin 3-8) with preference for the AT-4 sites or to angiotensin (1-7), not recognized by any of these receptors. Both angiotensin IV and angiotensin (1-7) are biologically active. For example angiotensin (1-7) retains some of the actions ascribed for angiotensin II but is shown to counteract others. Thus, it is obvious that the activity of many neuroactive peptides is modulated by bioactive fragments, which are formed by the action of a variety of peptidases. This phenomenon appears to represent an important regulatory mechanism that modulates many neuropeptide systems but is generally not acknowledged.