On-line electrogeneration of copper-peptide complexes in microspray mass spectrometry

The interaction of copper ions with peptides was investigated by electrospray mass spectrometry. Two electrospray micro-emitters were compared, the first one with a platinum electrode using a copper(II) electrolyte solution containing a peptide sample, and the second one with a sacrificial copper anode in a water/methanol solution containing only a peptide (i.e., angiotensin III, bradykinin, or Leu-enkephalin). The former yielded mainly Cu2+ complexes either with histidine residues or with the peptide backbone (Cu+ complexes can be also formed due to gas-phase reactions), whereas the latter can generate a mixture of both Cu+ and Cu2+ aqueous complexes that yield different complexation patterns. This study shows that electrospray emitters with soluble copper anodes enable the study of Cu(I)-peptide complexes in solutio

Prévenir et gérer la résistance des insectes aux pesticides : le cas de la noctuelle Helicoverpa armigera

Des ravageurs des cultures plus virulents ou résistants aux pesticides apparaissent. Le cotonnier n'est pas épargné. Les chercheurs analysent les facteurs de régulation de ces populations puis expérimentent des solutions avec les agriculteurs. Le Cirad, en complément d'une protection chimique raisonnée, propose des pratiques culturales et des variétés ayant un certain degré de résistance à un ravageur considéré. Différentes méthodologies pour la caractérisation de biotypes et la transformation génétique du cotonnier sont décrites. Des programmes de protection sont développés en Afrique de l'Ouest, comme la lutte étagée ciblée : le calcul d'un seuil économique permet d'ajuster les produits et leurs doses en fonction des résultats d'observations de terrain. Les agriculteurs économisent ainsi 40 à 50 % des quantités de produits. Les observations constituent le principal facteur limitant : une formation soutenue et des adaptations locales sont nécessaires. Les expériences acquises permettent d'envisager une simplification de ces observations. La prévention et la gestion de la résistance des insectes aux pesticides est un sujet de préoccupation majeure de la recherche : la résistance aux pyréthrinoïdes d'Helicoverpa armigera sur cotonnier en est une illustration. Il est primordial d'assurer un suivi en laboratoire et sur le terrain grâce à un réseau international : c'est le cas en Afrique de l'Ouest et du Centre. Les mécanismes mis en cause sont à l'étude. La collaboration entre plusieurs pays et plusieurs filières (par exemple coton et maraîchage), ainsi que le concours de différents services nationaux sont indispensables à la mise en place d'une protection intégrée des cultures

Potentially inappropriate prescribing including under-use amongst older patients with cognitive or psychiatric co-morbidities

Objective: the study aimed to determine the prevalence of and risk factors for inappropriate prescribing (IP) and prescribing omission (PO) in elderly with mental co-morbidities. Participants: one hundred fifty consecutive inpatients with mental co-morbidities hospitalised for acute medical illness (mean age 80 ± 9, 70% of women) were considered for the study. Measurements: IP and PO were prospectively indentified according to STOPP/START criteria at hospital admission. Results: over 95% were taking ≥1 medication (median = 7) which amounted to 1,137 prescriptions. The prevalence of IP was 77% and PO was 65%. The most frequent encountered IP concerned drugs adversely affecting fallers (25%) and antiaggregants therapy without atherosclerosis (14%). PO concerned antidepressants with moderate/severe depression (20%) and calcium-vitamin D supplementation (18%). Independent predictors for IP were increased number of concomitant drugs (odds ratio [OR] 1.54, 95% confidence interval [CI] 1.13-1.89), being cognitively impaired (OR 1.83, 95% CI 1.55-2.24), and having fallen in the preceding 3 months (OR 2.03, 95% CI 1.52-2.61) or hospitalised in the preceding year (OR 1.09, 95% CI 1.02-1.23). Concerning PO, psychiatric disorder (OR 1.64, 95% CI 1.42-2.01) and increase level of co-morbidities (OR 1.79, 95% CI 1.48-1.99) were identified. Living in an institutional setting was a predictive maker for both IP (OR 1.45, 95% CI 1.27-1.74) and PO (OR 1.67, 95% CI 1.32-1.91). Conclusion: IP and PO were highly prevalent raising the need of a greater health literacy concerning geriatric conditions in non-geriatrician practitioners who care elderly as well as in the community, in hospital and institutional settings for improving quality and safety in prescribing medicatio

About the Electrospray Ionization Source in Mass Spectrometry: Electrochemistry and On-chip Reactions

The present work shows that the electrochemical properties of electrospray ionization (ESI) can be used to add functions to the process. As example, we show how the choice of the electrode material can be used to study interactions between metal ions and biomolecules in mass spectrometry (MS). In positive ionization MS, an electrospray device acts as anode, which implies oxidation reactions. Sacrificial electrodes (made of copper or zinc) are used to supply the electrospray current and to produce cations that are able to react on-line with compounds of interest. Thus, the interactions between copper ions and ligands or peptides were investigated by using a copper electrode. Another example is the in situ electrogeneration of a dinuclear zinc(II) complex for the mass tagging of phosphopeptides when working with a zinc electrode. In order to perform these reactions on the same microchip, a dual-channel microsprayer was used, where one channel was dedicated to the tag electrogeneration and the other to the infusion of a phosphopeptides solution. Finally, this dual-channel microsprayer was used to study complexation at liquid-liquid interfaces in biphasic ESI-MS, such as thioether crowns and lead ions or peptides and phospholipids complexes. These examples illustrate the use of electrochemistry and on-chip reactions in ESI-MS analysis

Copper(I) and copper(II) binding to β-amyloid 16 (Aβ16) studied by electrospray ionization mass spectrometry

Copper-b-amyloid 16 (Aβ16) complexes were investigated by electrospray ionization mass spectrometry (ESI-MS). Copper(I) and (II) complexes were formed on-line in a microchip electrospray emitter by using a sacrificial copper electrode as the anode in positive ionization mode. In the presence of ascorbic acid in the peptide solution, the amount of Cu(I)-Aβ16 generated electrochemically was even higher. A kinetic model is proposed to account for the generation of copper complexes. The structure of Cu(I)-Aβ16 was investigated by tandem mass spectrometry (MS/MS), and the binding site of Cu(I) to Aβ16 was identified at the His13, His14 residues. Cu(II)-Aβ16 was also investigated by MS/MS and, based on the unusual observations of a-ions, the two binding residues of His13 and His14 of Aβ16 to Cu(II) were also confirmed. This approach provides direct information on Cu(I)-Aβ16 complexes generated in solution from metallic copper and gives evidence that both His13 and His14 are involved in the coordination of both Cu(I)- and Cu(II)-Aβ16 complexes