Genomic analysis in Chilean patients with suspected Rett syndrome: keep a broad differential diagnosis.

Rett syndrome (RTT, MIM #312750) is a rare genetic disorder that leads to developmental regression and severe disability and is caused by pathogenic variants in the gene. The diagnosis of RTT is based on clinical features and, depending on resources and access, on molecular confirmation. There is scarce information on molecular diagnosis from patients in Latin America, mostly due to limited availability and coverage of genomic testing.

Probing gas phase catalysis by atomic metal cations with flow tube mass spectrometry.

The evolution and applications of flow tube mass spectrometry in the study of catalysis promoted by atomic metal ions are tracked from the pioneering days in Boulder, Colorado, to the construction and application of the ICP/SIFT/QqQ and ESI/qQ/SIFT/QqQ instruments at York University and the VISTA-SIFT instrument at the Air Force Research Laboratory. The physical separation of various sources of atomic metal ions from the flow tube in the latter instruments facilitates the spatial resolution of redox reactions and allows the separate measurement of the kinetics of both legs of a two-step catalytic cycle, while also allowing a view of the catalytic cycle in progress downstream in the reaction region of the flow tube. We focus on measurements on O-atom transfer and bond activation catalysis as first identified in Boulder and emphasize fundamental aspects such as the thermodynamic window of opportunity for catalysis, catalytic efficiency, and computed energy landscapes for atomic metal cation catalysis.

Relativistic Effects in the Ligation of Atomic Coinage Metal Cations with O and CH: Anomalous Formation of Relativistic Mono- and Bis-adducts with Au.

The interaction of the atomic coinage metal cations Cu, Ag, and Au with O, a weak ligand, and CH, a strong ligand, was investigated with measurements of rate coefficients of ligation and quantum-chemical computations of ligation energies with an eye on relativistic effects going down the periodic table. Strong "third row enhancements" were observed for both the rate coefficients of ligation and ligation energies with the O ligand and for the formation of both the mono- and bis-adducts of M and the monoadduct of M(CH). The computations revealed that the third-row enhancement in the ligation energy is attributable to a relativistic increase in the ligation energy.

Toward ICP-SIFT mass spectrometry and atomic cation ligation as a probe of relativistic effects-A personal journey.

The ICP-SIFT mass spectrometer at York University, a derivative of flowing afterglow (FA) and selected-ion flow tube (SIFT) mass spectrometers, has provided a powerful technique to measure the chemistry and kinetics of atomic cation-molecule reactions. Here, I focus on periodic trends in the kinetics of ligation reactions of atomic ions with small molecules. I examine trends in ammonia ligation kinetics across the first two rows of the atomic transition metal cations and their correlation with ligand bond enthalpies and ligand field stabilization energies.

Calcium & ROS: Two orchestra directors for the requiem of death.

Tumor necrosis factor alpha (TNF) triggers regulated necrosis of mycobacterium-infected macrophages through of mitochondrial reactive oxygen species (mitoROS) production in a RIPK1/3-dependent manner. To explain that, Roca and colleagues describe an inter-orgallenar circuit which involves the lysosomal ceramide production, mitoROS, BAX activation and RyR Ca efflux from the endoplasmic reticulum into the mitochondrion.

Hydrogenated Gold Clusters from Helium Nanodroplets: Cluster Ionization and Affinities for Protons and Hydrogen Molecules.

We report the mass spectrometric detection of hydrogenated gold clusters ionized by electron transfer and proton transfer. The cations appear after the pickup of hydrogen molecules and gold atoms by helium nanodroplets (HNDs) near zero K and subsequent exposure to electron impact. We focus on the size distributions of the gold cluster cations and their hydrogen content, the electron energy dependence of the ion yield, patterns of hydrogenated gold cluster cation stability, and the presence of "magic" clusters.

Ligation Kinetics as a Probe for Non-Covalent Electrostatic Bonding and Electron Solvation of Alkali and Alkaline Earth Cations with Ammonia.

Mono-ligation kinetics were measured for ammonia reacting with atomic cations in the first two groups of the periodic table (K, Rb, Cs and Ca, Sr, Ba). Also, mono-ligation energies were computed using density functional theory (DFT) in an attempt to assess the role of non-covalent electrostatic interactions in these chemical reactions. The measurements were performed at room temperature in helium bath gas at 0.

Ligation kinetics as a probe for gas-phase ligand field effects: Ligation of atomic transition metal cations with ammonia at room temperature.

The kinetics of ammonia ligation to atomic first and second row transition metal cations were measured in an attempt to assess the role of ligand field effects in gas-phase ion-molecule reaction kinetics. Measurements were performed at 295 ± 2 K in helium bath gas at 0.35 Torr using an inductively coupled plasma/selected-ion flow tube tandem mass spectrometer.

Uptake and accommodation of water clusters by adamantane clusters in helium droplets: interplay between magic number clusters.

We report an experimental study of water clusters as guests in interactions with clusters of adamantane (Ad) as hosts that occur in doped helium droplets at extremely low temperatures. Separate experiments with pure water as dopant showed ready formation of a distribution of water clusters (H2O)mH+ that peaks at m = 11 and extends beyond m = 100 with local maxima at m = 4, 11, 21, 28 and 30 with (H2O)21H+ being the most anomalous and showing the greatest stability with respect to clusters immediately adjacent in water content. When adamantane is also added as a dopant, extensive hydration is seen in the formation of water/adamantane clusters, (H2O)mAdn+; magic number clusters (H2O)21Adn+ are seen for all the adamantane clusters.

Fullerene ion chemistry: a journey of discovery and achievement.

An account is provided of the extraordinary features of buckminster fullerene cations and their chemistry that we discovered in our Ion Chemistry Laboratory at York University (Canada) during a 'golden' period of research in the early 1990s, just after C60 powder became available. We identified new chemical ways of C60 ionization and tracked novel chemistry of C60 (n+) as a function of charge state (n=1-3) with some 50 different reagent molecules. We found that multiple charges enhance reaction rates and diversify reaction products and mechanisms.

Building Carbon Bridges on and between Fullerenes in Helium Nanodroplets.

We report the observation of sequential encounters of fullerenes with C atoms in an extremely cold environment. Experiments were performed with helium droplets at 0.37 K doped with C60 molecules and C atoms derived from a novel, pure source of C atoms.

Double Methotrexate-Modified Neuropeptide Y Analogues Express Increased Toxicity and Overcome Drug Resistance in Breast Cancer Cells.

Bioconjugates containing the neuropeptide Y (NPY) analogue [F(7),P(34)]-NPY as targeting moiety are able to deliver toxic agents specifically to breast cancer cells that overexpress the human Y1-receptor (hY1R). To increase their activity, multiple toxophores can be attached to one peptide. Herein, synthesis and characterization of [F(7),P(34)]-NPY conjugates containing two methotrexate (MTX) molecules are presented.

Experimental evidence for the influence of charge on the adsorption capacity of carbon dioxide on charged fullerenes.

We show, both experimentally and theoretically, that the adsorption of CO2 is sensitive to charge on a capturing model carbonaceous surface. In the experiment we doped superfluid helium droplets with C60 and CO2 and exposed them to ionising free electrons. Both positively and negatively charged C60(CO2)n(+/-) cluster ion distributions are observed using a high-resolution mass spectrometer and they show remarkable and reproducible anomalies in intensities that are strongly dependent on the charge.

A cleavable cytolysin-neuropeptide Y bioconjugate enables specific drug delivery and demonstrates intracellular mode of action.

Myxobacterial tubulysins are promising chemotherapeutics inhibiting microtubule polymerization, however, high unspecific toxicity so far prevents their application in therapy. For selective cancer cell targeting, here the coupling of a synthetic cytolysin to the hY1-receptor preferring peptide [F(7),P(34)]-neuropeptide Y (NPY) using a labile disulfide linker is described. Since hY1-receptors are overexpressed in breast tumors and internalize rapidly, this system has high potential as peptide-drug shuttle system.

Controlling toxicity of Peptide-drug conjugates by different chemical linker structures.

The side effects of chemotherapy can be overcome by linking toxic agents to tumor-targeting peptides with cleavable linkers. Herein, this concept is demonstrated by addressing the human Y1 receptor (hY1 R), overexpressed in breast tumors, with analogues of the hY1 R-preferring [F(7) ,P(34) ]NPY. First, carboxytetramethylrhodamine was connected to [F(7) ,P(34) ]NPY by an amide, ester, disulfide, or enzymatic linkage.

Specific tandem mass spectrometric detection of AGE-modified arginine residues in peptides.

Glycation is a non-enzymatic reaction of protein amino and guanidino groups with reducing sugars or dicarbonyl products of their oxidative degradation. Modification of arginine residues by dicarbonyls such as glyoxal and methylglyoxal results in formation of advanced glycation end-products (AGEs). In mammals, these modifications impact in diabetes mellitus, uremia, atherosclerosis and ageing.

Drug delivery and release systems for targeted tumor therapy.

Most toxic agents currently used for chemotherapy show a narrow therapeutic window, because of their inability to distinguish between healthy and cancer cells. Targeted drug delivery offers the possibility to overcome this issue by selectively addressing structures on the surface of cancer cells, therefore reducing undesired side effects. In this broad field, peptide-drug conjugates linked by intracellular cleavable structures have evolved as highly promising agents.

The receptor for advanced glycation end products (RAGE) specifically recognizes methylglyoxal-derived AGEs.

Diabetes-induced hyperglycemia increases the extracellular concentration of methylglyoxal. Methylglyoxal-derived hydroimidazolones (MG-H) form advanced glycation end products (AGEs) that accumulate in the serum of diabetic patients. The binding of hydroimidozolones to the receptor for AGEs (RAGE) results in long-term complications of diabetes typified by vascular and neuronal injury.

Multi-component ion modifiers and arcing suppressants to enhance differential mobility spectrometry for separation of peptides and drug molecules.

The optimization of ion/molecule chemistry in a differential mobility spectrometer (DMS) is shown to result in improved peak capacity, separation, and sensitivity. We have experimented with a modifier composed of multiple components, where each component accomplishes a specific task on mixtures of peptides and small drug molecules. Use of a higher proton affinity modifier (hexanol) provides increased peak capacity and separation.

Decorating (C) , = 1-3, with CO at low temperatures: Sterically enhanced physisorption.

Multiple attachment of CO to the monomer, dimer and trimer cations of C has been observed in the mass spectra of He nanodroplets sequentially doped with C and CO and exposed to electron ionization at 50 eV. Remarkable anomalies were seen in the ion yield for CO coverage for (C)(CO) and (C)(CO). These provide insight into the influence of steric properties on the nature of physisorption.

Trimethylation and Differential Mobility Spectroscopy in Quantitative Peptide Analysis: Increasing Selectivity and Sensitivity through Ion/Molecule Chemistry.

Isotopic labeling of peptides by trimethylation creates a charged quaternary amine group on the peptide that provides clear differentiation from unlabeled protonated peptides and protonated or sodiated chemical background. Differential mobility spectrometry, with its use of a chemical modifier, allows otherwise undesirable ion/molecule reactions in the mobility cell to increase selectivity and sensitivity of quantitative peptide analysis. A high proton affinity modifier selectively removes protonated and sodiated interference and background ions by proton and sodium transfer, while leaving the trimethylated ions with their quaternary amine groups unchanged.

Locating Pb2+ and Zn2+ in zinc finger-like peptides using mass spectrometry.

The binding preferences of Pb(2+)and Zn(2+) in doubly charged complexes with zinc finger-like 12-residue peptides (Pep), [Mn(Pep-2(n-1)H)](2+) have been explored using tandem mass spectrometry. The peptides were synthesized strategically by blocking the N-terminus with an acetyl group and with four cysteine and/or histidine residues in positions 2, 5, 8, and 11, arranged in different motifs: CCHH, CHCH, and CCCC. The MS(2) spectra of the Pb(2+) and Zn(2+) complexes show multiple losses of water and a single methane loss and these provide a sensitive method for locating the metal dication and so elucidating its coordination.

[Active muscle extension testing of the hamstrings: reference values and impacting factors].

Introduction: Less muscle elasticity of the hamstrings increases the risk of muscle strain. Muscle balance is the purpose of muscle stretching. The active knee-extension test (AKE) represents an established test of muscle elasticity.