Interlaced Fourier transformation of ultrafast 2D NMR data

A new protocol for processing the data arising in ultrafast 2D NMR is discussed and exemplified, based on the interlaced Fourier transformation. This approach is capable of dealing in a single, combined fashion, with the two mirror-imaged interferograms arising in this kind of experiment as a result of the acquisition of a train of magnetic field gradient echoes. By combining all the acquired data points into a common Fourier processing procedure the spectral width along the direct-acquisition domain becomes effectively doubled, giving the opportunity of employing acquisition gradients that are approximately half as strong as hitherto required. This in turn should lead to an overall enhancement in the signal-to-noise ratio of the experiment of ca. 2, as well as to improvements in the achievable digital resolution. These expectations were tested by carrying out a series of homo- and heteronuclear ultrafast 2D NMR acquisitions, and found systematically fulfilled. The robustness and conditions that allow the interlaced numerical procedure to be implemented in routine analytical applications were explored and are briefly discussed.     

Evidence for a kaon-bound state K(-)pp produced in K(-) absorption reactions at rest

We have searched for a deeply bound kaonic state by using the FINUDA spectrometer installed at the e(+)e(-) collider DAPhiNE. Almost monochromatic K(-)'s produced through the decay of phi(1020) mesons are used to observe K(-) absorption reactions stopped on very thin nuclear targets. Taking this unique advantage, we have succeeded to detect a kaon-bound state K(-)pp through its two-body decay into a Lambda hyperon and a proton. The binding energy and the decay width are determined from the invariant-mass distribution as 115(+6)(-5)(stat)(+3)(-4)(syst) MeV and 67(+14)(-11)(stat)(+2)(-3)(syst) MeV, respectively.     

Excited states in 163,164Ho populated through incomplete-fusion reactions

High-spin states in ^163,164Ho were investigated by means of in-beam -ray spectroscopy techniques using the multidetector array GASP. Excited states in ^163,164Ho were populated predominantly through the incomplete-fusion mechanism in the ¹⁶⁰Gd (¹¹B reaction at a beam energy of 61 MeV. Known rotational bands in ¹⁶³ Ho have been extended to higher spins and a three-quasiparticle band has been observed in this nucleus. Rotational bands have been identified in ¹⁶⁴Ho and their configurations have been discussed. Empirical Gallagher-Moszkowski (GM) splitting energies were extracted from the and GM doublets. Alignments, band crossing frequencies, and electromagnetic properties have been analyzed in the framework of the cranking model.Received: 13 February 2004, Revised: 18 March 2004, Published online: 14 September 2004PACS: 21.10.Re Collective levels - 21.60.Ev Collective models - 23.20.Lv transitions and level energies - 27.70. + q      

Real-time 2D NMR identification of analytes undergoing continuous chromatographic separation

We have recently proposed and demonstrated an approach that enables the acquisition of multidimensional nuclear magnetic resonance (NMR) spectra within a single scan. A promising application opened up by this new accelerated form of data acquisition concerns the possibility of monitoring in real time the chemical nature of analytes subject to a continuous flow. The present paper illustrates such potential, with the real-time acquisition of a series of 2D 1H NMR spectra arising from a mixture of compounds subject to a continuous liquid chromatography (LC) separation. This real-time 2D NMR identification of chemicals eluted minutes apart under usual LC-NMR conditions differs from the way in which LC-2D NMR has hitherto been carried out, which relies on stopped-flow modes of operations whereby fractions are first collected and then subject to individual, aliquot-by-aliquot analyses. The real-time LC-2D NMR experiment hereby introduced can be implemented in a straightforward manner using modern commercial LC-NMR hardware, thus opening up immediate possibilities in high-throughput characterizations of complex molecules.     

Glycosidic monoterpenes from Linaria capraria

During our systematic study on the species of genus Linaria (Scrophulariaceae) present in Italy, we examined the glycosidic fraction of Linaria capraria Moris et De Not., a species endemic of Tuscany archipelago. This fraction is particularly complex and we considered in this article only the medium polarity components. In accordance with previous studies, L. capraria shows acyl derivatives of antirrhinoside 1 as specific chemotaxonomic iridoidic markers. L. capraria exhibits a complex composition, with regard to iridoidic constituents, with several chromatographic problems to be resolved. We then isolated, besides the known antirrhinoside 1, two acyl derivatives of antirrhinoside, the 6'-O-senecioyl derivative, 2, and the 6'-O-angeloyl derivative, 3. In addition a glucoside of an acyclic monoterpene, 4, was also isolated, which may be correlated to the other monoterpenic glycosides isolated from other species of Scrophulariaceae.     

Kac limit for finite-range spin glasses

We consider a finite-range spin glass model in arbitrary dimension, where the strength of the two-body coupling decays to zero over some distance gamma(-1). We show that, under mild assumptions on the interaction potential, the infinite-volume free energy of the system converges to that of the Sherrington-Kirkpatrick one, in the Kac limit gamma-->0. This could be a first step toward an expansion around mean-field theory, for spin glass systems.     

Solid-phase synthesis and characterization of a novel fullerene-peptide derived from histone H3

A peptide analogue from a histone H3 protein containing the L-fulleropyrrolidino-glutamic acid has been prepared by a solid-phase approach and has been fully characterized. By molecular modelling it was verified that this peptide derivative is able to retain a binding capacity to the MHC (major histocompatibility complex) molecule similar to that of the cognate epitope.     

New beta cis folded organocobalt derivatives with a salen-type ligand

The reduction of [Co(III)(tmsalen)py(2)](+)ClO(4)(-), where tmsalen = 4,4',7,7'-tetramethylsalen, with NaBH(4)/PdCl(2) in alkaline methanolic solution, followed by the oxidative addition of CH(2)ClI, leads to the expected trans organometallic dimeric species 1, [CH(2)ClCo(tmsalen)](2), provided that the product is recovered from the reaction mixture immediately after the completion of the reaction. If 1 is left for longer time in contact with the reaction mixture, the intramolecular reaction of the axial chloromethyl group with the equatorial chelate leads to the formation of the monocationic complex 2, containing a seven-membered ring. In this complex the novel tetradentate ligand coordinates Co in a cis fashion, the other two positions being occupied by one py and one water molecule. The resulting complex is chiral, even if the reaction product is a racemic compound. The unidentate ligands of 2 have been exchanged quantitatively for N-MeIm, and the resulting complex 3 still maintains the beta cis geometry. Therefore, 2 may be considered the precursor of a new class of organocobalt derivatives with a folded tetradentate ligand and two adjacent exchangeable sites. On the basis of the geometry of the tetradentate Schiff bases in complexes, where they adopt a planar geometry, it was suggested that there is a significant electron density delocalization involving the metal center over the two chemically equivalent moieties of Co(chel). Comparison of the geometry of the planar salicylaldiminate (sal) moiety with that of the cyclized methoxy-iminate one (imi) in 2 and 3 strongly supports that the delocalization, still present in sal, is essentially either lost or strongly reduced in imi.     

SUBPOL: a novel SUcrose-Based Polymer support for solid-phase peptide synthesis and affinity chromatography applications

A novel SUcrose-Based Polymer support (SUBPOL) with tailored morphology suitable for the use in solid-phase peptide synthesis (SPPS) is described, and its application as a hydrophilic affinity matrix for the specific removal of fibrinogen from human plasma is demonstrated. After suspension polymerization of partly methacrylated 2,1':4,6-di-O-isopropylidene sucrose and subsequent removal of the protecting groups, hydrophilic spherical polymer beads were obtained. The morphology of the resulting resin was controlled by variation of the porogen as well as the average degree of substitution with respect to the methacryloyl groups of the monomer mixture. After introduction of amino groups for a permanent attachment of immobilized peptide ligands, prevention of unintended esterification during SPPS was achieved by silylation of remaining hydroxy groups. Alternatively, a Rink amide linker was introduced prior to SPPS to allow cleavage and subsequent analysis of the peptide assembled on the SUBPOL resins. Two hexapeptides of sequence kwiivw and hffflw, consisting of d-amino acids, as well as a 19-mer peptide corresponding to the sequence GSGVRGDFGSLAPRVARQL of the VP1 protein from the foot-and-mouse disease virus (FMDV) were successfully prepared both manually or in a semi-automated process on SUBPOL resins according to the Fmoc/tBu strategy. Yields and purities were comparable to peptides prepared on commercially available polystyrene resins. A specific affinity adsorbent containing the fibrinogen-binding pentapeptide GPRPK was prepared by SPPS on SUBPOL resins of different morphology, and the strong impact of the affinity matrix on adsorption performance was demonstrated.