Visualization of Molecular Permeation into a Multi-compartment Phospholipid Vesicle.

Passive permeation of small molecules into vesicles with multiple compartments is a critical event in many chemical and biological processes. We consider the translocation of the peptide NAF-1 labeled with a fluorescent fluorescein dye across membranes of rhodamine-labeled 1,2-dioleoyl--glycero-3-phosphocholine (DOPC) into liposomes with internal vesicles. Time-resolved microscopy revealed a sequential absorbance of the peptide in both the outer and inner micrometer vesicles that developed over a time period of minutes to hours, illustrating the spatial and temporal progress of the permeation.

Leaflet-Dependent Effect of Anionic Lipids on Membrane Insertion by Cationic Cell-Penetrating Peptides.

Cationic membrane-permeating peptides can cross membranes unassisted by transmembrane protein machinery, and there is consensus that anionic lipids facilitate this process. Although membranes are asymmetric in lipid composition, investigations of the impact of anionic lipids on peptide-membrane insertion in model vesicles primarily use symmetric anionic lipid distributions between bilayer leaflets. Here, we investigate the leaflet-specific influence of three anionic lipid headgroups [phosphatidic acid (PA), phosphatidylserine (PS), and phosphatidylglycerol (PG)] on insertion into model membranes by three cationic membrane-permeating peptides (NAF-1, RW, and WWWK).

Noninvasive Detection of Chemical Defenses in Poison Frogs Using the MasSpec Pen.

Poison frogs are well-known for their fascinating ability to store alkaloids in their skin as chemical defense against predators. Chemical methods used to study these alkaloids are limited by requirements for euthanasia or stress during sampling. Here, we demonstrate sensitive and biocompatible alkaloid detection and monitoring using the MasSpec Pen, a handheld, noninvasive chemical detection device coupled to a mass spectrometer.

Identifying Clinically Relevant Bacteria Directly from Culture and Clinical Samples with a Handheld Mass Spectrometry Probe.

Background: Rapid identification of bacteria is critical to prevent antimicrobial resistance and ensure positive patient outcomes. We have developed the MasSpec Pen, a handheld mass spectrometry-based device that enables rapid analysis of biological samples. Here, we evaluated the MasSpec Pen for identification of bacteria from culture and clinical samples.

Design of Peptides for Membrane Insertion: The Critical Role of Charge Separation.

A physical understanding of membrane permeation and translocation by small, positively charged molecules can illuminate cell penetrating peptide mechanisms of entry and inform drug design. We have previously investigated the permeation of the doubly charged peptide WKW and proposed a defect-assisted permeation mechanism where a small molecule with +2 charge can achieve a metastable state spanning the bilayer by forming a membrane defect with charges stabilized by phospholipid phosphate groups. Here, we investigate the membrane permeation of two doubly charged peptides, WWK and WWWK, with charges separated by different lengths.

Rapid Screening of COVID-19 Directly from Clinical Nasopharyngeal Swabs Using the MasSpec Pen.

The outbreak of COVID-19 has created an unprecedent global crisis. While the polymerase chain reaction (PCR) is the gold standard method for detecting active SARS-CoV-2 infection, alternative high-throughput diagnostic tests are of a significant value to meet universal testing demands. Here, we describe a new design of the MasSpec Pen technology integrated to electrospray ionization (ESI) for direct analysis of clinical swabs and investigate its use for COVID-19 screening.

Clinical Translation and Evaluation of a Handheld and Biocompatible Mass Spectrometry Probe for Surgical Use.

Background: Intraoperative tissue analysis and identification are critical to guide surgical procedures and improve patient outcomes. Here, we describe the clinical translation and evaluation of the MasSpec Pen technology for molecular analysis of in vivo and freshly excised tissues in the operating room (OR).

Methods: An Orbitrap mass spectrometer equipped with a MasSpec Pen interface was installed in an OR.