Ezequiel Perez-Inestrosa

Synthesis and Characterization of New Fluorescent Styrene-Containing Carborane Derivatives: The Singular Quenching Role of a Phenyl Substituent

A set of neutral and anionic carborane derivatives in which the styrenyl fragment is introduced as a fluorophore group has been successfully synthesized and characterized. The reaction of the monolithium salts of 1-Ph-1,2-C(2)B(10)H(11), 1-Me-1,2-C(2)B(10)H(11) and 1,2-C(2)B(10)H(12) with one equivalent of 4-vinylbenzyl chloride leads to the formation of compounds 1-3, whereas the reaction of the dilithium salt of 1,2-C(2)B(10)H(12) with two equivalents of 4-vinylbenzyl chloride gives disubstituted compound 4. The closo clusters were degraded using the classical method, KOH in EtOH, to afford the corresponding nido species, which were isolated as tetramethylammonium salts. The crystal structure of the four closo compounds 1-4 were analyzed by X-ray diffraction. All compounds, except 1, display emission properties, with quantum yields dependent on the nature of the cluster (closo or nido) and the substituent on the second C(cluster) atom. In general, closo compounds 2-4 exhibit high fluorescence emission, whereas the presence of a nido cluster produces a decrease of the emission intensity. The presence of a phenyl group bonded to the C(cluster) results in an excellent electron-acceptor unit that produces a quenching of the fluorescence. DFT calculations have confirmed the charge-separation state in 1 to explain the quenching of the fluorescence and the key role of the carboranyl fragment in this luminescent process.

Cephalosporin chemical reactivity and its immunological implications.

Purpose of reviewThe aim of this article is to analyze the chemical reactivity of cephalosporins resulting in the epitope responsible for recognition by IgE antibodies and to establish the basis of the allergenicity. Recent findingsIncreasing evidence supports the role of cephalosporins in IgE hypersensitivity reactions. Third and fourth generation cephalosporins appear to be more involved in specific IgE reactions and often no cross-reactivity with traditional benzyl penicillin determinants exists. In some instances selective responses to unique cephalosporins occur and in others common side-chain similarities exist. SummaryLack of knowledge of the exact chemical structure of cephalosporin antigenic determinants has hindered clinical interpretation of allergic reactions to these drugs and hampered understanding of the specific recognition by IgE molecules of these determinants. Data indicate that R2 is not present in the final conjugate and that recognition by IgE antibodies is mainly directed to the R1 acyl side chain and to the β-lactam fragment that remains linked to the carrier protein in the cephalosporin conjugation process.

OFF-ON-OFF fluorescence switch with T-latch function.

A novel molecular system with characteristics of an OFF-ON-OFF fluorescence switch was designed to integrate the function of a T-latch. In detail, a receptor1-fluorophore-receptor2 architecture was adopted to achieve fluorescence switching upon addition of protons.

Enhanced Functionality for Donor–Acceptor Oligothiophenes by means of Inclusion of BODIPY: Synthesis, Electrochemistry, Photophysics, and Model Chemistry

We have synthesized several new push-pull oligothiophenes based on the boron dipyrromethene (BODIPY) moiety as the electron acceptor and the more well-known oligothiophenes substituted with N,N-dialkylamino functions to enhance their electron-donor ability. A complete characterization of the electronic properties has been carried out; it consists of their photophysical, electrochemical, and vibrational properties. The compounds have been studied after chemical treatment with acids and after oxidation. In this regard, they can be termed as NIR dyes and amphoteric redox electroactive molecules. We have described the presence of dual fluorescence in these molecules and fluorescence quenching either by energy transfer or, in the push-pull molecules, by electron exchange. The combination of electrochemical and proton reversibility along with the interesting optical properties of the new species offer an interesting platform for sensor and material applications.

Immediate allergic reactions to betalactams: facts and controversies.

Purpose of reviewTo analyse the available data in the field of immediate allergic reactions to β-lactams, with particular emphasis on more recent studies, and to comment on the future role of this group of antibiotics. Recent findingsThe world of β-lactams has become more complex than initially thought, due to the increased number of chemical structures available, the wide variety of indications for their use in treating different infectious diseases, and possibly also due to the interaction of other as yet undetermined factors. Benzyl penicillin, the original inducer of allergic reactions, has now largely been replaced by amoxicillin and, to a lesser extent, by cephalosporins in inducing IgE-mediated allergic reactions. These structures often share extensive cross-reactivity, eliciting clinical reactions to many compounds, especially amongst penicillins. In other circumstances selective responses are observed which are restricted to one group or one single compound, as occurs in the group of cephalosporins. The application of new determinants for skin testing and the use of adapted in-vitro studies have enabled these findings to be confirmed in detail. SummaryResults indicate that evaluation of immediate reactions to β-lactams requires the use of several determinants for both in-vitro and in-vivo testing, and which must reflect the relevant drug involved in eliciting the response. This tendency will be strengthened in the future if use of benzyl penicillin continues to decrease as a drug to which populations are exposed.

Skin testing for immediate hypersensitivity to betalactams: comparison between two commercial kits

Introduction:  Skin testing with major and minor determinants of benzylpenicillin is the recommended standard practice to evaluate subjects with immediate hypersensitivity to betalactams. The withdrawal of these products from the market has set us back to the early days, before the introduction of reagents for in vivo testing.

Highly sensitive dendrimer-based nanoplasmonic biosensor for drug allergy diagnosis.

A label-free biosensing strategy for amoxicillin (AX) allergy diagnosis based on the combination of novel dendrimer-based conjugates and a recently developed nanoplasmonic sensor technology is reported. Gold nanodisks were functionalized with a custom-designed thiol-ending-polyamido-based dendron (d-BAPAD) peripherally decorated with amoxicilloyl (AXO) groups (d-BAPAD-AXO) in order to detect specific IgE generated in patients serum against this antibiotic during an allergy outbreak. This innovative strategy, which follows a simple one-step immobilization procedure, shows exceptional results in terms of sensitivity and robustness, leading to a highly-reproducible and long-term stable surface which allows achieving extremely low limits of detection. Moreover, the viability of this biosensor approach to analyze human biological samples has been demonstrated by directly analyzing and quantifying specific anti-AX antibodies in patients serum without any sample pretreatment. An excellent limit of detection (LoD) of 0.6ng/mL (i.e. 0.25kU/L) has been achieved in the evaluation of clinical samples evidencing the potential of our nanoplasmonic biosensor as an advanced diagnostic tool to quickly identify allergic patients. The results have been compared and validated with a conventional clinical immunofluorescence assay (ImmunoCAP test), confirming an excellent correlation between both techniques. The combination of a novel compact nanoplasmonic platform and a dendrimer-based strategy provides a highly sensitive label free biosensor approach with over two times better detectability than conventional SPR. Both the biosensor device and the carrier structure hold great potential in clinical diagnosis for biomarker analysis in whole serum samples and other human biological samples.

PEGylated aza-BODIPY derivatives as NIR probes for cellular imaging

Neutral water-soluble aza-dipyrromethene boron difluoride (aza-BODIPY) derivatives are synthesized for biological imaging applications. Aqueous solubility is increased by optimizing the synthetic conditions to obtain aza-BODIPYs with several tetraethyleneglycol groups. Their spectral properties and assays performed on cultured cells, demonstrate the potential of these compounds as near-infrared (NIR) emitting fluorescent probes.

BODIPY-Labeled DC-SIGN-Targeting Glycodendrons Efficiently Internalize and Route to Lysosomes in Human Dendritic Cells

Glycodendrons bearing nine copies of mannoses or fucoses have been prepared by an efficient convergent strategy based on Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC). These glycodendrons present a well-defined structure and have an adequate size and shape to interact efficiently with the C-type lectin DC-SIGN. We have selected a BODIPY derivative to label these glycodendrons due to its interesting physical and chemical properties as chromophore. These BODIPY-labeled glycodendrons were internalized into dendritic cells by mean of DC-SIGN. The internalized mannosylated and fucosylated dendrons are colocalized with LAMP1, which suggests routing to lysosomes. The interaction of these glycodendrons with DC-SIGN at the surface of dendritic cells did not induce maturation of the cells. Signaling analysis by checking different cytokines indicated also the lack of induction the expression of inflammatory and noninflammatory cytokines by these second generation glycodendrons.

The C-terminus of H-ras as a target for the covalent binding of reactive compounds modulating Ras-dependent pathways

Ras proteins are crucial players in differentiation and oncogenesis and constitute important drug targets. The localization and activity of Ras proteins are highly dependent on posttranslational modifications at their C-termini. In addition to an isoprenylated cysteine, H-Ras, but not other Ras proteins, possesses two cysteine residues (C181 and C184) in the C-terminal hypervariable domain that act as palmitoylation sites in cells. Cyclopentenone prostaglandins (cyPG) are reactive lipidic mediators that covalently bind to H-Ras and activate H-Ras dependent pathways. Dienone cyPG, such as 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2) and Δ12-PGJ2 selectively bind to the H-Ras hypervariable domain. Here we show that these cyPG bind simultaneously C181 and C184 of H-Ras, thus potentially altering the conformational tendencies of the hypervariable domain. Based on these results, we have explored the capacity of several bifunctional cysteine reactive small molecules to bind to the hypervariable domain of H-Ras proteins. Interestingly, phenylarsine oxide (PAO), a widely used tyrosine phosphatase inhibitor, and dibromobimane, a cross-linking agent used for cysteine mapping, effectively bind H-Ras hypervariable domain. The interaction of PAO with H-Ras takes place in vitro and in cells and blocks modification of H-Ras by 15d-PGJ2. Moreover, PAO treatment selectively alters H-Ras membrane partition and the pattern of H-Ras activation in cells, from the plasma membrane to endomembranes. These results identify H-Ras as a novel target for PAO. More importantly, these observations reveal that small molecules or reactive intermediates interacting with spatially vicinal cysteines induce intramolecular cross-linking of H-Ras C-terminus potentially contributing to the modulation of Ras-dependent pathways.