Patterns of Marijuana Use and Nicotine Exposure in Patients Seeking Elective Aesthetic Procedures.

Background: With the increasing legalization and popularity of marijuana, it is frequently and sometimes unintentionally combined with nicotine-containing products. As a consequence, patients may fail to accurately report usage during preoperative examinations or remain unaware of the inclusion of nicotine. This poses a challenge for clinicians in identifying preoperative nicotine exposure.

The Impact of the COVID-19 Pandemic on Geographic Placement of Applicants to General Surgery Residency Programs.

Objective: COVID-19 greatly influenced medical education and the residency match. As new guidelines were established to promote safety, travel was restricted, visiting rotations discontinued, and residency interviews turned virtual. The purpose of this study is to assess the geographic trends in distribution of successfully matched General Surgery applicants prior to and after the implementation of pandemic guidelines, and what we can learn from them as we move forward.

Peptide diffusion in biomolecular condensates.

Diffusion determines the turnover of biomolecules in liquid-liquid phase-separated condensates. We considered the mean square displacement and thus the diffusion constant for simple model systems of peptides GGGGG, GGQGG, and GGVGG in aqueous solutions after phase separation by simulating atomic-level models. These solutions readily separate into aqueous and peptide-rich droplet phases.

Parameter Dependence of the Solubility Limit for Disodium Phosphate.

The solubility limit was calculated for supersaturated solutions of disodium phosphate in water as a function of the sodium-oxygen Lennard-Jones radius parameter . We found that changes in the sodium-oxygen were clearly exponentially related to the concentration of the solubility limit. Starting from standard force fields more suited to nucleic acids and phospholipids, only relatively small changes were required to achieve the experimentally known solubility limit.

Transition Mutations in the hTERT Promoter Are Unrelated to Potential i-motif Formation in the C-Rich Strand.

Increased expression of the human telomere reverse transcriptase (hTERT) in tumors promotes tumor cell survival and diminishes the survival of patients. Cytosine-to-thymine (C-to-T) transition mutations (C250T or C228T) in the promoter create binding sites for transcription factors, which enhance transcription. The G-rich strand of the promoter can form G-quadruplex structures, whereas the C-rich strand can form an i-motif in which multiple cytosine residues are protonated.

Direct measurements of biomolecular electrostatics through experiments.

Biomolecular electrostatics has been a subject of computational investigations based on 3D structures. This situation is changing because emerging experimental tools allow us to quantitatively investigate biomolecular electrostatics without any use of structure information. Now, electrostatic potentials around biomolecules can directly be measured for many residues simultaneously by nuclear magnetic resonance (NMR) spectroscopy.

"The Most Satisfactory Procedure in the Field of Pediatric Surgery": The History of Hypertrophic Pyloric Stenosis.

This historical retrospective explores the history of hypertrophic pyloric stenosis from its initial observations to the first surgical approaches to modern understandings of pathogenesis. The important work of Hirschsprung, Fredet, and Ramstedt remains a foundational part of management for this complex condition.

Effects of Conformational Constraint on Peptide Solubility Limits.

Liquid-liquid phase separation of proteins preferentially involves intrinsically disordered proteins or disordered regions. Understanding the solution chemistry of these phase separations is key to learning how to quantify and manipulate systems that involve such processes. Here, we investigate the effect of cyclization on the liquid-liquid phase separation of short polyglycine peptides.

Assessment of the Components of the Electrostatic Potential of Proteins in Solution: Comparing Experiment and Theory.

In this work, the components of the protein electrostatic potentials in solution are analyzed with NMR paramagnetic relaxation enhancement experiments and compared with continuum solution theory, and multiscale simulations. To determine the contributions of the solution components, we analyze them at different ionic strengths from 0 to 745 mM. A theoretical approximation allows the determination of the electrostatic potential at a given proton without reference to the protein structure given the ratio of paramagnetic relaxation enhancements rates between a cationic and an anionic probe.

The Effects of Flexibility on dsDNA-dsDNA Interactions.

A detailed understanding of the physical mechanism of ion-mediated dsDNA interactions is important in biological functions such as DNA packaging and homologous pairing. We report the potential of mean force (PMF) or the effective solvent mediated interactions between two parallel identical dsDNAs as a function of interhelical separation in 0.15 M NaCl solution.

Structural Studies on the Shapeshifting Murine Norovirus.

Noroviruses are responsible for almost a fifth of all cases of gastroenteritis worldwide. The calicivirus capsid is composed of 180 copies of VP1 with a molecular weight of ~58 kDa. This coat protein is divided into the N-terminus (N), the shell (S) and C-terminal protruding (P) domains.

From the Operating Room to Online: Medical Student Surgery Education in the Time of COVID-19.

Background: On March 17, 2020 the Association of American Medical Colleges recommended dismissal of medical students from clinical settings due to the COVID-19 pandemic. Third-year (M3) and fourth-year (M4) medical students were at home, M4s were interested in teaching, and residents and faculty had fewer clinical responsibilities due to elective surgery cancellations. To continue M3 access to education, we created a virtual surgery elective (VSE) that aimed to broaden students' exposure to, and elicit interest in, general surgery (GS).

Contributions of higher-order proximal distribution functions to solvent structure around proteins.

The proximal distribution function (pDF) quantifies the probability of finding a solvent molecule in the vicinity of solutes. The approach constitutes a hierarchically organized theory for constructing approximate solvation structures around solutes. Given the assumption of universality of atom cluster-specific solvation, reconstruction of the solvent distribution around arbitrary molecules provides a computationally convenient route to solvation thermodynamics.

Multiple Signals in the Gut Contract the Mouse Norovirus Capsid To Block Antibody Binding While Enhancing Receptor Affinity.

Human norovirus is the leading cause of gastroenteritis worldwide, with no approved vaccine or antiviral treatment to mitigate infection. These plus-strand RNA viruses have T = 3 icosahedral protein capsids with 90 pronounced protruding (P) domain dimers, to which antibodies and cellular receptors bind. We previously demonstrated that bile binding to the capsid of mouse norovirus (MNV) causes several major conformational changes; the entire P domain rotates by ∼90° and contracts onto the shell, the P domain dimers rotate about each other, and the structural equilibrium of the epitopes at the top of the P domain shifts toward the closed conformation, which favors receptor binding while blocking antibody binding.

De novo determination of near-surface electrostatic potentials by NMR.

Electrostatic potentials computed from three-dimensional structures of biomolecules by solving the Poisson-Boltzmann equation are widely used in molecular biophysics, structural biology, and medicinal chemistry. Despite the approximate nature of the Poisson-Boltzmann theory, validation of the computed electrostatic potentials around biological macromolecules is rare and methodologically limited. Here, we present a unique and powerful NMR method that allows for straightforward and extensive comparison with electrostatic models for biomolecules and their complexes.

Quantitative description of a contractile macromolecular machine.

Contractile injection systems (CISs) [type VI secretion system (T6SS), phage tails, and tailocins] use a contractile sheath-rigid tube machinery to breach cell walls and lipid membranes. The structures of the pre- and postcontraction states of several CISs are known, but the mechanism of contraction remains poorly understood. Combining structural information of the end states of the 12-megadalton R-type pyocin sheath-tube complex with thermodynamic and force spectroscopy analyses and an original modeling procedure, we describe the mechanism of pyocin contraction.

Thermodynamic Compensation in Peptides Following Liquid-Liquid Phase Separation.

Liquid-liquid phase separation of proteins often incorporates intrinsically disordered proteins or those with disordered regions. Examining these processes via the entropy change is desirable for establishing a quantitative foundation with which to probe and understand these phase transitions. Of interest is the effect of residue sequence on the entropy of the peptide backbone.

A Norovirus Uses Bile Salts To Escape Antibody Recognition While Enhancing Receptor Binding.

Noroviruses, members of the family, are the major cause of epidemic gastroenteritis in humans, causing ∼20 million cases annually. These plus-strand RNA viruses have T=3 icosahedral protein capsids with 90 pronounced protruding (P) domain dimers to which antibodies and cellular receptors bind. In the case of mouse norovirus (MNV), bile salts have been shown to enhance receptor (CD300lf) binding to the P domain.

Implementation and evaluation of eight virtual surgical electives for medical students during the COVID-19 pandemic.

Background: Eight novel virtual surgery electives (VSEs) were developed and implemented in April-May 2020 for medical students forced to continue their education remotely due to COVID-19.

Methods: Each VSE was 1-2 weeks long, contained specialty-specific course objectives, and included a variety of teaching modalities. Students completed a post-course survey to assess changes in their interest and understanding of the specialty.

A Strategy for Undergraduate Medical Education in Urology During the COVID-19 Pandemic.

Objective: To provide a framework for a virtual curriculum during the COVID-19 pandemic for medical student educators that introduces and teaches clinical concepts important in urology and surgical specialties in general.

Methods: We created a 1-week virtual urology course utilizing interactive lectures, case-based exercises, and faculty-proctored surgical video reviews. Students were assigned self-study modules and participated in case-based discussions and presentations on a topic of their choice.

Effects of Model Shape, Volume, and Softness of the Capsid for DNA Packaging of phi29.

Double-stranded DNA is under extreme confinement when packed in phage phi29 with osmotic pressures approaching 60 atm and densities near liquid crystalline. The shape of the capsid determined from experiment is elongated. We consider the effects of the capsid shape and volume on the DNA distribution.