Isomerism of low-lying states in 86Y

Low-energy isomeric states of ⁸⁶Y were populated in the reaction ⁷³Ge + ¹⁶O at 57MeV and were investigated by means of delayed n $ \gamma$ and $ \gamma$ $ \gamma$ coincidences. A half-life of 70(7)ns was measured for the 5^- state at 208keV, yielding an exceptionally small B(M1) value of 2.0(7)×10^-5 W.u. and a B(E2) value of 0.34(⁺²⁴ _-13) W.u. For the other three known isomeric states at 218, 243, and 302keV, the half-lives extracted from the present experimental data are in very good agreement with previous measurements. Given the newly observed isomeric character of the 5^- 208keV state, the re-analysis of earlier experimental data on the 302keV isomer led to a new spin-parity assignment, 6⁺, for this state. In addition, this re-evaluation provided two g -factors, -0.083(3) and +0.63(2) , for the 208 and 302keV states, respectively. The results are discussed in terms of spherical-shell model calculations performed with a truncated space of configurations built on the f _5/2 , p _3/2 , p _1/2 , and g _9/2 valence orbitals. Effective spin, orbital, and “tensor” g -factors were determined empirically for protons and neutrons in the considered configuration space.     

Profiling and sequence analysis of gangliosides in human astrocytoma by high-resolution mass spectrometry

In this preliminary investigation, a low-grade astrocytoma (AcT) is investigated by high-resolution (HR) mass spectrometry (MS) aiming at characterization of gangliosides with potential biomarker value. The research was conducted towards a comparative mapping of ganglioside expression in AcT, its surrounding tissue (ST) and a normal control brain tissue (NT). HR MS was conducted in the negative ion mode nanoelectrospray ionization (nanoESI). Fragmentation analysis was carried out by collision-induced dissociation (CID) MS²–MS^4. Due to the high resolving power and mass accuracy, by comparative mapping of the ganglioside extracts from AcT, ST and NT, under identical conditions, 37 different species in AcT, 40 in ST and 56 in NT were identified. AcT and ST were found to contain 18 identical ganglioside components. Among all three specimens, ST extract presented the highest levels of sialylation, fucosylation and acetylation, a feature which might be correlated to the tumor expansion in the adjacent brain area. MS mapping indicated also that AcT, ST and NT share one doubly deprotonated molecule at m/z 1063.31, attributable to GT1(d18:1/18:0) or GT1(d18:0/18:1). CID MS²–MS⁴ on these particular ions detected in AcT and ST provided data supporting GT1c isomer in the investigated astrocytoma tissue. Our results show that HR MS has a remarkable potential in brain cancer research for the determination of tumor-associated markers and for their structural determination.

Fully automated chip-based nanoelectrospray combined with electron transfer dissociation for high throughput top-down proteomics

The conventional protocol for protein identification by electrospray ionization mass spectrometry (MS) is based on enzymatic digestion which renders peptides to be analyzed by liquid chromatography-MS and collision-induced dissociation (CID) multistage MS, in the so-called bottom-up approach. Though this method has brought a significant progress to the field, many limitations, among which, the low throughput and impossibility to characterize in detail posttranslational modifications in terms of site(s) and structure, were reported. Therefore, the research is presently focused on the development of procedures for efficient top-down fragmentation of intact protein ions. In this context, we developed here an approach combining fully automated chip-based-nanoelectrospray ionisation (nanoESI), performed on a NanoMate robot, with electron transfer dissociation (ETD) for peptide and top-down protein sequencing and identification. This advanced analytical platform, integrating robotics, microfluidics technology, ETD and alternate ETD/CID, was tested and found ideally suitable for structural investigation of peptides and modified/functionalized peptides as well as for top-down analysis of medium size proteins by tandem MS experiments of significantly increased throughput and sensitivity. The obtained results indicate that NanoMate-ETD and ETD/CID may represent a viable alternative to the current MS strategies, with potential to develop into a method of routine use for high throughput top-down proteomics.     

Signatures of γ softness or triaxiality in low energy nuclear spectra

Signatures of γ softness or rigid triaxiality in low energy, low spin nuclear spectra are discussed. Two classes of signatures, relating to γ-band energy staggering, are found to provide clear distinctions between these shapes. The data for even-even nuclei are compared to predictions for potentials with varying γ dependence. It is found that nuclei with large asymmetries can be characterized by potentials that are nearly γ flat, with, at most, a few percent deviation from γ independence.     

Assessment of the Molecular Expression and Structure of Gangliosides in Brain Metastasis of Lung Adenocarcinoma by an Advanced Approach Based on Fully Automated Chip-Nanoelectrospray Mass Spectrometry

Gangliosides (GGs), sialic acid-containing glycosphingolipids, are known to be involved in the invasive/metastatic behavior of brain tumor cells. Development of modern methods for determination of the variations in GG expression and structure during neoplastic cell transformation is a priority in the field of biomedical analysis. In this context, we report here on the first optimization and application of chip-based nanoelectrospray (NanoMate robot) mass spectrometry (MS) for the investigation of gangliosides in a secondary brain tumor. In our work a native GG mixture extracted and purified from brain metastasis of lung adenocarcinoma was screened by NanoMate robot coupled to a quadrupole time-of-flight MS. A native GG mixture from an age-matched healthy brain tissue, sampled and analyzed under identical conditions, served as a control. Comparative MS analysis demonstrated an evident dissimilarity in GG expression in the two tissue types. Brain metastasis is characterized by many species having a reduced N-acetylneuraminic acid (Neu5Ac) content, however, modified by fucosylation or O-acetylation such as Fuc-GM4, Fuc-GM3, di-O-Ac-GM1, O-Ac-GM3. In contrast, healthy brain tissue is dominated by longer structures exhibiting from mono- to hexasialylated sugar chains. Also, significant differences in ceramide composition were discovered. By tandem MS using collision-induced dissociation at low energies, brain metastasis-associated GD3 (d18:1/18:0) species as well as an uncommon Fuc-GM1 (d18:1/18:0) detected in the normal brain tissue could be structurally characterized. The novel protocol was able to provide a reliable compositional and structural characterization with high analysis pace and at a sensitivity situated in the fmol range.     

B(E2) values in 150Nd and the critical point symmetry X(5)

Lifetimes of states in 150Nd were measured using the recoil distance method following Coulomb excitation of 150Nd by a 132 MeV 32S beam. The experiment was performed at the Yale Tandem accelerator, employing the SPEEDY gamma-ray detector array and the New Yale Plunger Device. Reduced transition probabilities in 150Nd are compared to the predictions of the critical point symmetry X(5) of the phase/shape transition that occurs for the N = 90 rare earth isotones. Very good agreement was observed between the parameter-free (apart from scale) X(5) predictions and the low-spin level scheme of 150Nd, revealing this as the best case thus far for the realization of the X(5) symmetry.     

Chiral doublet structures in odd-odd n = 75 isotones: chiral vibrations

New sideband partners of the yrast bands built on the pi(h11/2)nu(h11/2) configuration were identified in 55Cs, 57La, and 61Pm N = 75 isotones of 134Pr. These bands form with 134Pr unique doublet-band systematics suggesting a common basis. Aplanar solutions of 3D tilted axis cranking calculations for triaxial shapes define left- and right-handed chiral systems out of the three angular momenta provided by the valence particles and the core rotation, which leads to spontaneous chiral symmetry breaking and the doublet bands. Small energy differences between the doublet bands suggest collective chiral vibrations.     

Shape changes and test of the critical-point symmetry X(5) in N = 90 nuclei

Reliable and precise lifetimes of excited states in ¹⁵⁴Gd and ¹⁵⁶Dy were measured using the recoil distance Doppler shift (RDDS) technique. Excited states of ¹⁵⁴Gd were populated via Coulomb excitation with a ³²S beam at 110 MeV delivered by the FN tandem accelerator at the University of Cologne. For ¹⁵⁶Dy a coincidence plunger experiment was performed at the Laboratori Nazionali di Legnaro with the GASP spectrometer and the Cologne coincidence plunger apparatus using the reaction ¹²⁴Sn(³⁶S,4n)¹⁵⁶Dy at a beam energy of 155 MeV. Shape changes previously suggested to appear in the ground-state band (gsb) of ¹⁵⁶Dy and in the s-band above the first band crossing were not supported by the transition probabilities determined in this work. The measured transition probabilities of ¹⁵⁶Dy and ¹⁵⁴Gd as well as the corresponding energy spectra are compared with the predictions of the recently proposed X(5) model and in the case of ¹⁵⁶Dy also with an IBA fit.Received: 30 October 2002, Published online: 2 March 2004PACS: 21.10.Tg Lifetimes - 27.70. + q - 21.60.Ev Collective models - 23.20.-g Electromagnetic transitions     

Robust nuclear observables and constraints on random interactions

The predictions of the interacting boson model two-body random ensemble are compared to empirical results on nuclei from Z = 8-100. Heretofore unrecognized but robust empirical trends are identified and related both to the distribution of valence nucleon numbers and to the need for and applicability of specific, nonrandom interactions. Applications to expected trends in exotic nuclei are discussed.