Unexpected single-step formation of 1,2-anti-heterodisubstituted calix[4]arenes upon alkylation of a tribenzoyl precursor

The selective preparation and complete structural characterization of a small series of 1,2-anti-heterodisubstituted calix[4]arenes has been accomplished. These compounds were obtained in two steps from unsubstituted p-tert-butylcalix[4]arene by tribenzoylation and a subsequent one-pot, two-step sequence involving alkylation with simultaneous partial deacylation, resulting in heterodisubstituted calixarenes carrying an alkyl and an aroyl group. The monoalkyl-tribenzoyl intermediate, prior to in situ deprotection, could also be isolated.     

Particle Propagation in Cosmological Backgrounds

We analyse the quantum propagation of interacting particles in cosmological backgrounds. The model we use consists of a doublet of massive scalar fields propagating in an expanding universe filled with massless radiation. The masses are much larger than the Hubble expansion rate, so that the number of massive particles is preserved and the fields adequately described within the adiabatic approximation. We focus on the dissipative effects related to the expansion rate by computing the imaginary part of the self-energy. In the quasi static approximation, we recover the expected result that instantaneous decay rate is governed by the local temperature. We then analyse the long time behavior of the propagator to unravel the secular effects induced by the self-energy. We show that these effects can be expressed in terms of integrals of local quantities. Applications to the trans-Planckian question are briefly discussed.     

On the Number of Facets of Three-Dimensional Dirichlet Stereohedra III: Full Cubic Groups

We are interested in the maximum possible number of facets that Dirichlet stereohedra for three-dimensional crystallographic groups can have. In two previous papers, D. Bochiş and the second author studied the problem for noncubic groups. This paper deals with “full” cubic groups, while “quarter” cubic groups are left for a subsequent paper. Here, “full” and “quarter” refers to the recent classification of three-dimensional crystallographic groups by Conway, Delgado-Friedrichs, Huson and Thurston. This paper’s main result is that Dirichlet stereohedra for any of the 27 full groups cannot have more than 25 facets. We also find stereohedra with 17 facets for one of these groups. Research partially supported by the Spanish Ministry of Education and Science, grant number MTM2005-08618-C02-02.     

A kinetic study of the decomposition of N-bromoserine

This article reports the kinetics of the decomposition of N-bromoserine formed rapidly by bromation of serine by BrO^?. The main decomposition products are glycolaldehyde, ammonia, carbon dioxide, and bromide ions at pH < 11.5, and β-hydroxypyruvic acid, ammonia, and bromide ions at pH > 11.5. The reaction is of order one with respect to N-bromoserine, and is independent of ionic strength and excess serine. The rate constant increases with increasing pH at pH > 11 and with decreasing pH at pH < 8, and over the range pH 8–11 has the constant value 1.67 × 10^?3 s^?1 at 298 K.     

Summability and estimates for polynomials and multilinear mappings

In this paper we extend and generalize several known estimates for homogeneous polynomials and multilinear mappings on Banach spaces. Applying the theory of absolutely summing nonlinear mappings, we prove that estimates which are known for mappings on ?_p spaces in fact hold true for mappings on arbitrary Banach spaces.     

Neutral and cationic alkylmanganese(II) complexes containing 2,6-bisiminopyridine ligands

Manganese alkyl complexes stabilised by 2,6-bis(N,N'-2,6-diisopropyl-phenyl)acetaldiminopyridine ((iPr)BIP) have been selectively prepared by reacting suitable alkylmanganese(II) precursors, such as homoleptic dialkyls [(MnR(2))(n)] or the corresponding THF adducts [{MnR(2)(thf)}(2)] with the mentioned ligand. For R=CH(2)CMe(2)Ph or CH(2)Ph, formally Mn(I) derivatives are produced, in which one of the two R groups migrates to the 4-position of the central pyridine ring in the (iPr)BIP ligand. In contrast, a true dialkyl complex [MnR(2)((iPr)BIP)] can be isolated for R=CH(2)SiMe(3). In solution, this compound slowly evolves to the corresponding Mn(I) monoalkyl derivative. A detailed study of this reaction provides insights on its mechanism, showing that it proceeds through successive alkyl migrations, followed by spontaneous dehydrogenation. Protonation of [Mn(CH(2)SiMe(3))(2)((iPr)BIP)] with the pyridinium salt [H(Py)(2)][BAr'(4)] (Ar'=3,5-C(6)H(3)(CF(3))(2)) leads to the cationic species [Mn(CH(2)SiMe(3))(Py)((iPr)BIP)](+). Alternatively, the same complex can be produced by reaction of the pyridine complex [{Mn(CH(2)SiMe(3))(2)(Py)}(2)] with the protonated ligand salt [H(iPr)BIP](+)[BAr'(4)](-). This last reaction allows the synthesis of analogous cationic alkylmanganese(II) derivatives, when precursors of type [MnR(2)((iPr)BIP)] are not available. Treatment of these neutral and cationic (iPr)BIP alkylmanganese derivatives with a range of typical co-catalysts (modified methylaluminoxane (MMAO), B(C(6)F(5))(3), trimethyl or triisobutylaluminum) does not lead to active ethylene polymerisation catalysts.     

Synthesis of methyl (±)-3,5-bis(substitutedmethyl)pyrrolidine-2-carboxylates: a convenient approach to proline-mimetics

Starting from readily available N-benzyl protected methyl 3,5-bis(hydroxymethyl)pirrolidinecarboxylate a number of racemic methyl t-3,t-5-disubstitutedprolinates have been synthesised, thus opening a practical way towards the preparation of a variety of putative proline-mimetics. In this context, N-Boc protected derivatives proved to be better intermediates than their N-benzyl counterparts in terms of cleanness and overall yield of the synthetic procedure.     

Application of thiophilic chromatography to deplete serum immunoglobulins in sample preparation for bidimensional electrophoresis

Serum is a typical sample for non-invasive studies in clinical research. Its proteome characterization is challenging, since requires extensive protein depletion. Methods used nowadays for removal of high-abundance proteins are expensive or show quite often a low loading capacity, which has strong repercussions on the number of samples and replicates per analysis.In order to deplete immunoglobulins (Igs) and albumin (HSA) from 1 mL serum samples, we have developed a protocol based on a combination of thiophilic chromatography, not previously used in clinical proteomics, and a HSA-specific resin. Ig/HSA-depleted samples, immunoglobulinome and albuminone were analyzed by 2-DE. Thiophilic chromatography, coupled with HSA-depletion, allows a good 2-DE resolution as well as the visualization of new spots. Moreover, it yields enough protein to evaluate technical variability and facilitate subsequent protein identification. To validate the protocol, we carried out a preliminary comparative study between triplicate Igs/HSA-depleted serum samples from healthy control individuals and recently diagnosed/untreated rheumatoid arthritis (RA) patients. RA patients showed several acute phase proteins, as well as additional serum proteins, differentially and significantly regulated.Therefore, thiophilic chromatography can be used as an efficient and economical method in 2-DE to deplete immunoglobulins from large human serum samples before a more extensive fractioning.     

Cell integrity signaling and response to stress in fission yeast

Cellular responses to external signals are regulated by conserved mitogen-activated protein (MAP) kinase signaling cascades. These pathways are triggered by a vast range of stimuli. They phosphorylate numerous proteins, produce significant changes in the gene expression, and regulate diverse processes ranging from proliferation and differentiation to apoptosis in all eukaryotic cells. Three conserved MAP kinase signaling pathways have been identified in the fission yeast Schizosaccharomyces pombe. In this article, we present an overview of two of those pathways that regulate the response of fission yeast to stress and maintain cell integrity. The structure of these signaling modules and the function of the pathways, including the regulation by endogenous inhibitors, are discussed.