An efficient H/D exchange method allowing the deuteration of pyridines, quinolines, indoles, and alkyl amines with D2 in the presence of Ru@PVP nanoparticles is described. By a general and simple ...procedure involving mild reaction conditions and simple filtration to recover the labeled product, the isotopic labeling of 22 compounds proceeded in good yield with high chemo‐ and regioselectivity. The viability of this procedure was demonstrated by the labeling of eight biologically active compounds. Remarkably, enantiomeric purity was conserved in the labeled compounds, even though labeling took place in the vicinity of the stereogenic center. The level of isotopic enrichment observed is suitable for metabolomic studies in most cases. This approach is also perfectly adapted to tritium labeling because it uses a gas as an isotopic source. Besides these applications to molecules of biological interest, this study reveals a rich and underestimated chemistry on the surface of ruthenium nanoparticles.
Don't just slap a label on it! A regioselective and stereospecific method for the deuteration of nitrogen‐containing compounds has been developed on the basis of a CH activation process triggered by Ru nanoparticles (RuNps). This general and efficient approach to deuterium labeling was applied to 22 compounds, including 8 biologically active substances (see scheme; PVP=polyvinylpyrrolidone).
The activation of CH bonds has revolutionized modern synthetic chemistry. However, no general strategy for enantiospecific CH activation has been developed to date. We herein report an ...enantiospecific CH activation reaction followed by deuterium incorporation at stereogenic centers. Mechanistic studies suggest that the selectivity for the α‐position of the directing heteroatom results from a four‐membered dimetallacycle as the key intermediate. This work paves the way to novel molecular chemistry on nanoparticles.
Various compounds, such as amines, amino acids, or peptides, can undergo enantiospecific CH activation/deuteration in the presence of ruthenium nanocatalysts under mild conditions. Theoretical studies revealed a four‐membered dimetallacycle as the key intermediate and suggested that the collective motion of surface species can facilitate the CH activation step by modulating the local electronic structure.
Objectives/Hypothesis:
We investigated the hypothesis that 30 minutes of raised intensity phonation alters transcript levels of vocal fold intercellular tight junction proteins and disrupts the vocal ...fold epithelial barrier.
Study Design:
Prospective animal study.
Methods:
Eighteen New Zealand white breeder rabbits were randomly assigned to receive 30 minutes of raised intensity phonation or approximation of the vocal folds without phonation. Quantitative polymerase chain reaction (qPCR) was used to investigate transcript levels of the epithelial intercellular tight junction proteins, occludin and zonula occludin‐1 (ZO‐1), and the adherens junction proteins β‐catenin and E‐cadherin. Structural alterations to the vocal fold epithelium were further examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
Results:
Mann‐Whitney U revealed significantly decreased occludin (P = .016) and β‐catenin (P = .016) gene expression from rabbits undergoing raised intensity phonation compared with control. There were no significant differences in Z0‐1 and E‐cadherin gene expression between groups (P > .025). SEM revealed significant obliteration, desquamation, and evidence of microhole formation in rabbit vocal folds exposed to raised intensity phonation compared with control, whereas TEM revealed dilated intercellular morphology between groups.
Conclusions:
Results provide support for the hypothesis that a transient episode of raised intensity phonation alters transcript levels of vocal fold intercellular tight junction proteins and disrupts integrity of the epithelial barrier. The loss of barrier integrity may have significant consequences on epithelial defenses and compromise protection of the underlying mucosa from damage secondary to prolonged vibration exposure.
Objectives/Hypothesis
Vocal fold scar is a major cause of dysphonia, and optimal treatments do not currently exist. Small intestinal submucosa (SIS) is a biomaterial developed for the treatment of a ...variety of pathologies. The purpose of this study was to investigate the effects of SIS implantation on tissue remodeling in scarred vocal folds using routine staining, immunohistochemistry, and high‐speed videoendoscopy (HSV).
Study Design
Prospective, blinded group analysis.
Methods
Thirteen New Zealand White rabbits underwent a vocal fold scarring procedure followed by microflap elevation with or without SIS implantation. Seven months later, they underwent a phonation procedure with HSV and laryngeal harvest. Alcian blue and elastica van Gieson staining and immunohistochemistry for collagen types I and III were used to evaluate histological healing outcomes. Dynamic functional remodeling of the scarred vocal fold in the presence of SIS implants was evaluated using HSV imaging to capture restoration of vibratory amplitude, amplitude ratio, and left‐right phase symmetry.
Results
Density of collagen I was significantly decreased in SIS versus microflap‐treated vocal folds. No differences were found between groups for hyaluronic acid, elastin, or collagen type III. Organization of elastin in the subepithelial region appeared to affect amplitude of vibration and the shape of the vocal fold edge.
Conclusions
SIS implantation into chronic scar reduced the density of collagen I deposits. There was no evidence of a negative impact or complication from SIS implantation. Regardless of treatment type, organization of elastin in the subepithelial region may be important to vibratory outcomes.
Level of Evidence
NA. Laryngoscope, 128:901–908, 2018
This work deals with the determination, using equilibrium and nonequilibrium molecular dynamics, of the viscosity of an ionic liquid: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ...(emimTf2N). A first method consists in computing the shear viscosity using the Green-Kubo formalism from the pressure tensor correlation function obtained from equilibrium simulations. On the other hand, the Newtonian viscosity can be extracted from the shear rate dependence of the viscosity in nonequilibrium simulations using the mode-coupling theory and the standard Cross and Carreau equations. We show that both methods lead to the same viscosity value, provided that the simulation time is long enough for the first method (much longer than advocated in the literature) and that special care is taken in the extrapolation procedure of the latter (simulations must be performed at very low shear rate). The force field employed in this work leads to an overestimation of the viscosity, with respect to experiment, by a factor ranging between 6 and 4 in the 293 K to 500 K temperature domain.
We have developed a novel surgical/computational model for the investigation of unilat-eral vocal fold paralysis (UVFP) which will be used to inform future in silico approaches to improve surgical ...outcomes in type I thyroplasty. Healthy phonation (HP) was achieved using cricothyroid suture approximation on both sides of the larynx to generate symmetrical vocal fold closure. Following high-speed videoendoscopy (HSV) capture, sutures on the right side of the larynx were removed, partially releasing tension unilaterally and generating asymmetric vocal fold closure characteristic of UVFP (sUVFP condition). HSV revealed symmetric vibration in HP, while in sUVFP the sutured side demonstrated a higher frequency (10–11%). For the computational model, ex vivo magnetic resonance imaging (MRI) scans were captured at three configurations: non-approximated (NA), HP, and sUVFP. A finite-element method (FEM) model was built, in which cartilage displacements from the MRI images were used to prescribe the adduction, and the vocal fold deformation was simulated before the eigenmode calculation. The results showed that the frequency comparison between the two sides was consistent with observations from HSV. This alignment between the surgical and computational models supports the future application of these methods for the investigation of treatment for UVFP.
Objective
An obstacle to clinical use of RNA‐based gene suppression is instability and inefficiency of current delivery modalities. Nanoparticle delivery likely holds great promise, but the kinetics ...and transfection conditions must be optimized prior to in vivo utility. We investigated a RNA nanoparticle complex incorporating a lipitoid transfection reagent in comparison to a commercially available reagent.
Study Design
In vitro.
Methods
We investigated which variables influence transfection efficiency of lipitoid oligomers and a commercially available reagent across species, in vitro. These variables included duration, dose, and number of administrations, as well as serum and media conditions. The target gene was Smad3, a signaling protein in the transforming growth factor‐β cascade implicated in fibroplasia in the vocal folds and other tissues.
Results
The two reagents suppressed Smad3 mRNA for up to 96 hours; lipitoid performed favorably and comparably. Both compounds yielded 60% to 80% mRNA knockdown in rat, rabbit, and human vocal fold fibroblasts (P < 0.05 relative to control). Dose and number of administrations played a significant role in gene suppression (P < 0.05). Suppression was more dose‐sensitive with lipitoid. At a constant siRNA concentration, a 50% decrease in gene expression was observed in response to a five‐fold increase in lipitoid concentration. Increased number of administrations enhanced gene suppression, ∼45% decrease between one and four administrations. Neither serum nor media type altered efficiency.
Conclusion
Lipitoid effectively knocked down Smad3 expression across multiple transfection conditions. These preliminary data are encouraging, and lipitoid warrants further investigation with the goal of clinical utility.
Level of Evidence
NA. Laryngoscope, 127:E231–E237, 2017
Picosecond pulse–probe radiolysis measurements of highly concentrated Cl– aqueous solutions are used to probe the oxidation mechanism of the Cl–. The transient absorption spectra are measured from ...340 to 710 nm in the picosecond range for the ultrafast electron pulse radiolysis of halide solutions at different concentrations up to 8 M. The amount of Cl2 •– formation within the electron pulse increases notably with increasing Cl– concentration. Kinetic measurements reveal that the direct ionization of Cl– cannot solely explain the significant amount of fast Cl2 •– formation within the electron pulse. The results suggest that Cl– reacts with the precursor of the OH• radical, i.e., H2O•+ radical, to form Cl• atom within the electron pulse and the Cl• atom reacts subsequently with Cl– to form Cl2 •– on very short time scales. The proton transfer reaction between H2O•+ and the water molecule competes with the electron transfer reaction between Cl– and H2O•+. Molecular dynamics simulations show that number of water molecules in close proximity decreases with increasing concentration of the salt (NaCl), confirming that for highly concentrated solutions the proton transfer reaction between H2O•+ and a water molecule becomes less efficient. Diffusion-kinetic simulations of spur reactions including the direct ionization of Cl– and hole scavenging by Cl– show that up to 30% of the H2O•+ produced by the irradiation could be scavenged for solutions containing 5.5 M Cl–. This process decreases the yield of OH• radical in solution on the picosecond time scale. The experimental results for the same concentration of Cl– at a given absorbed dose show that the radiation energy absorbed by counterions is transferred to Cl– or water molecules and the effect of the countercation such as Li+, K+, Na+, and Mg2+ on the oxidation yield of Cl– is negligible.
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