High-Precision Single-Molecule Characterization of the Folding of an HIV RNA Hairpin by Atomic Force Microscopy.

The folding of RNA into a wide range of structures is essential for its diverse biological functions from enzymatic catalysis to ligand binding and gene regulation. The unfolding and refolding of individual RNA molecules can be probed by single-molecule force spectroscopy (SMFS), enabling detailed characterization of the conformational dynamics of the molecule as well as the free-energy landscape underlying folding. Historically, high-precision SMFS studies of RNA have been limited to custom-built optical traps.

Going Vertical To Improve the Accuracy of Atomic Force Microscopy Based Single-Molecule Force Spectroscopy.

Single-molecule force spectroscopy (SMFS) is a powerful technique to characterize the energy landscape of individual proteins, the mechanical properties of nucleic acids, and the strength of receptor-ligand interactions. Atomic force microscopy (AFM)-based SMFS benefits from ongoing progress in improving the precision and stability of cantilevers and the AFM itself. Underappreciated is that the accuracy of such AFM studies remains hindered by inadvertently stretching molecules at an angle while measuring only the vertical component of the force and extension, degrading both measurements.

Improved Free-Energy Landscape Quantification Illustrated with a Computationally Designed Protein-Ligand Interaction.

Quantifying the energy landscape underlying protein-ligand interactions leads to an enhanced understanding of molecular recognition. A powerful yet accessible single-molecule technique is atomic force microscopy (AFM)-based force spectroscopy, which generally yields the zero-force dissociation rate constant (k ) and the distance to the transition state (Δx ). Here, we introduce an enhanced AFM assay and apply it to probe the computationally designed protein DIG10.

Rapid Characterization of a Mechanically Labile α-Helical Protein Enabled by Efficient Site-Specific Bioconjugation.

Atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) is a powerful yet accessible means to characterize mechanical properties of biomolecules. Historically, accessibility relies upon the nonspecific adhesion of biomolecules to a surface and a cantilever and, for proteins, the integration of the target protein into a polyprotein. However, this assay results in a low yield of high-quality data, defined as the complete unfolding of the polyprotein.

Acute intraoperative neurogenic myocardial stunning during intracranial endoscopic fenestration and shunt revision in a pediatric patient.

Neurogenic stunned myocardium (NSM) is syndrome of myocardial dysfunction following an acute neurological insult. We report a case of NSM that occurred intraoperatively in a pediatric patient undergoing endoscopic fenestration and shunt revision. Accidental outflow occlusion of irrigation fluid and ventricular distension resulted in an acute increase in heart rate and arterial blood pressure.

Complications during the management of pediatric refractory status epilepticus with benzodiazepine and pentobarbital infusions.

The objective of this retrospective study was to evaluate complications in the management of refractory status epilepticus (RSE) treated with benzodiazepine and pentobarbital infusions. Of 28 children with RSE, eleven (39%) were treated with a pentobarbital infusion after failure to control RSE with a benzodiazepine infusion; while17 children (61%) required only a benzodiazepine infusion. The mean maximum pentobarbital infusion dosage was 5.

Ketogenic diet: rapid onset of selenium deficiency-induced cardiac decompensation.

Selenium-deficiency cardiomyopathy is a known secondary complication from long-term treatment with a ketogenic diet for medical refractory epilepsy. Our patient, a 5-year-old boy on a ketogenic diet for intractable seizures, had a normal selenium level before starting the diet, but he shortly thereafter developed acute reversible cardiomyopathy and ventricular tachycardia, which was unmasked during a hospitalization for an elective operative procedure. His cardiomyopathy was suspected to be secondary to a selenium-deficient state and was confirmed by way of a markedly low serum selenium level and supported by rapid improvement with the initiation of selenium supplementation and cessation of the ketogenic diet.

Neurogenic stunned myocardium after acute hydrocephalus.

Neurogenic stunned myocardium (NSM) is a syndrome of cardiac stunning after a neurological insult. It is commonly observed after aneurysmal subarachnoid hemorrhage but is increasingly being reported after other neurological events. The underlying mechanism of NSM is believed to be a hypothalamic-mediated sympathetic surge causing weakened cardiac contractility and even direct cardiac myocyte damage.