Development and Validation of a Qualitative Method for Target Screening of 448 Pesticide Residues in Fruits and Vegetables Using UHPLC/ESI Q‑Orbitrap Based on Data-Independent Acquisition and Compound Database

A semiautomated qualitative method for target screening of 448 pesticide residues in fruits and vegetables was developed and validated using ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UHPLC/ESI Q-Orbitrap). The Q-Orbitrap Full MS/dd-MS² (data dependent acquisition) was used to acquire product-ion spectra of individual pesticides to build a compound database or an MS library, while its Full MS/DIA (data independent acquisition) was utilized for sample data acquisition from fruit and vegetable matrices fortified with pesticides at 10 and 100 μg/kg for target screening purpose. Accurate mass, retention time and response threshold were three key parameters in a compound database that were used to detect incurred pesticide residues in samples. The concepts and practical aspects of in-spectrum mass correction or solvent background lock-mass correction, retention time alignment and response threshold adjustment are discussed while building a functional and working compound database for target screening. The validated target screening method is capable of screening at least 94% and 99% of 448 pesticides at 10 and 100 μg/kg, respectively, in fruits and vegetables without having to evaluate every compound manually during data processing, which significantly reduced the workload in routine practice

Use of Recombinant Factor VII in Cardiac Surgery

The off-label use of recombinant human coagulation factor VIIa has been increasing to a number of different treatment areas since its original approval in 1999. Several US patents describe claims for FVIIa utilization in non-hemophilia patients, treatment of bleeding due to trauma, as a means to reverse major bleeding, including intracranial bleeding, induced from fibrinolytic therapy as well as a patent for using FVIIa in the treatment of bleeding for patients with bleeding disorders not caused by hemophilia, but rather bleeding disorders due to thrombocytopenia, platelet disorders, and von Willebrand’s disease. Bleeding after cardiac surgery remains a serious complication that can increase both morbidity and mortality. We review the off-label usage of recombinant factor VIIa as a hemostatic agent that may help control bleeding following cardiac surgery

The Carboxyl Terminus of Eremomycin Facilitates Binding to the Non‑d‑Ala‑d‑Ala Segment of the Peptidoglycan Pentapeptide Stem

Glycopeptide antibiotics inhibit cell wall biosynthesis in Gram-positive bacteria by targeting the peptidoglycan (PG) pentapeptide stem structure (l-Ala-d-iso-Gln-l-Lys-d-Ala-d-Ala). Structures of the glycopeptide complexed with a PG stem mimic have shown that the d-Ala-d-Ala segment is the primary drug binding site; however, biochemical evidence suggests that the glycopeptide–PG interaction involves more than d-Ala-d-Ala binding. Interactions of the glycopeptide with the non-d-Ala-d-Ala segment of the PG stem were investigated using solid-state nuclear magnetic resonance (NMR). LCTA-1421, a double ¹⁵N-enriched eremomycin derivative with a C-terminal [¹⁵N]­amide and [¹⁵N]­Asn amide, was complexed with whole cells of <i>Staphylococcus aureus</i> grown in a defined medium containing l-[3-¹³C]­Ala and d-[1-¹³C]­Ala in the presence of alanine racemase inhibitor alaphosphin. ¹³C­{¹⁵N} and ¹⁵N­{¹³C} rotational-echo double-resonance (REDOR) NMR measurements determined the ¹³C–¹⁵N internuclear distances between the [¹⁵N]­Asn amide of LCTA-1421 and the ¹³C atoms of the bound d-[1-¹³C]­Ala-d-[1-¹³C]­Ala to be 5.1 and 4.8 Å, respectively. These measurements also determined the distance from the C-terminal [¹⁵N]­amide of LCTA-1421 to the l-[3-¹³C]­Ala of PG to be 3.5 Å. The measured REDOR distance constraints position the C-terminus of the glycopeptide in the proximity of the l-Ala of the PG, suggesting that the C-terminus of the glycopeptide interacts near the l-Ala segment of the PG stem. <i>In vivo</i> REDOR measurements provided structural insight into how C-terminally modified glycopeptide antibiotics operate

Dual Mode of Action for Plusbacin A₃ in <i>Staphylococcus aureus</i>

We have used C­{F}, N­{F}, and N­{P} rotational-echo double resonance NMR to determine the location and conformation of ¹⁹F and ¹⁵N double-labeled plusbacin A₃ and of double-labeled <i>deslipo</i>-plusbacin A₃, each bound to the cell walls of whole cells of <i>Staphyloccocus aureus</i> grown in media containing [1-¹³C]­glycine. The ³¹P is primarily in wall teichoic acid. Approximately 25% of plusbacin headgroups (the cyclic depsipeptide backbone) are in a closed conformation (N–F separation of 6 Å), while 75% are in a more open conformation (N–F separation of 12 Å). The closed headgroups have no contact with wall teichoic acid, whereas the open headgroups have a strong contact. This places the closed headgroups in hydrophobic regions of the cell wall and the open headgroups in hydrophilic regions. None of the plusbacin tails have contact with the ³¹P of either wall teichoic acid or the cell membrane and thus are in hydrophobic regions of the cell wall. In addition, both heads and tails of plusbacin A₃ have contact with the glycyl ¹³C incorporated in cell-wall peptidoglycan pentaglycyl bridges <i>and</i> with ¹³C-labeled purines near the membrane surface. We interpret these results in terms of a dual mode of action for plusbacin A₃: <i>first</i>, disruption of the peptidoglycan layer nearest to the membrane surface by closed-conformation plusbacin A₃ leading to an inhibition of chain extension by transglycosylation; <i>second</i>, thinning and disruption of the membrane (possibly including disruption of ATP-binding cassette transporters embedded in the membrane) by open-conformation plusbacin A₃, thereby leading to release of ATP to the hydrophilic regions of the cell wall and subsequent binding by plusbacin A₃