A comparison of novel silicone plate vs. auricular cartilage in upper eyelid reconstruction following excision of malignant tumor.

Purpose: To compare surgical and functional outcomes, safety, efficacy and cost of silicone plate vs. autogenous auricular cartilage (AAC) as alternate material to tarsal plate for upper eyelid reconstruction after excision of malignant tumor. Methods: A prospective, comparative, interventional study of over 3 years was conducted on two groups of twenty patients each. All the patients had undergone the Modified Cutler Beard procedure with AAC being used as tarsal substitute in one group and a novel silicone plate in the other. Post-operative MRD 1, LPS action, Central Lid Thickness, and Lid contour were recorded at one week, one month and six months follow-up. Results: The pre-operative MRD 1 in the silicone plate and AAC group was -2.95 ± 1.19 mm and -3.05 ± 1(1).05 mm, post-operative in the silicone plate group 3.8 ± 0.4 mm, and in the AAC group, 3.8 ± 0.41 mm. The pre-operative LPS action in the silicone plate and AAC group was 1.2 ± 1.1 mm and 1.0 ± 0.9 mm and post-operative it was 13.8 ± 0.4 mm for the silicone plate group and 13.7 ± 0.4 mm for the AAC group. The post-operative lid thickness for the silicone plate group was 4.4 ± 0.17 mm and for the AAC group it was 4.4 ± 0.08 mm. Conclusion: The cosmetic outcome in terms of lid contour maintenance is better in the silicone plate group, in which it markedly reduces the surgical time, provides earlier rehabilitation, and eliminates disease transmission. Harvesting of AAC is a skillful and time-consuming procedure and adds to the post-operative morbidity due to the presence of a second surgical site. The low manufacturing cost of silicone plate as opposed to other allogenic and synthetic tarsal substitutes makes it readily available to resource limited populations. The silicone plate is reckoned to become the material of choice as tarsal substitute in the future. Abbreviations: AAC = Autogenous auricular cartilage, MRD-1 = Margin reflex distance-1, LPS = levator palpebrae superioris, PFH = palpebral fissure height.

Distinguishing between the Electrostatic Effects and Explicit Ion Interactions in a Stark Probe.

Vibrational Stark probes are incisive tools for measuring local electric fields in a wide range of chemical environments. The interpretation of the frequency shift often gets complicated due to the specific interactions of the probe, such as hydrogen bonding and Lewis bonding. Therefore, it is important to distinguish between the pure electrostatic response and the response due to such specific interactions. Here we report a molecular system that is sensitive to both the Stark effect from a single ion and the explicit Lewis bonding of ions with the probe. The molecule consists of a crown ether with an appended benzonitrile. The crown captures cations of various charges, and the electric field from the ions is sensed by the benzonitrile probe. Additionally, the lone pair of the benzonitrile can engage in Lewis interactions with some of the ions by donating partial charge density to the ions. Our system exhibits both of these effects and therefore is a suitable test bed for distinguishing between the pure electrostatic and the Lewis interactions. Our computational results show that the electrostatic influence of the ion is operative at large distances, while the Lewis interaction becomes important only within distances that permit orbital overlap. Our results may be useful for using the nitrile probe for measuring electrostatic and coordination effects in complex ionic environments such as the electrode-electrolyte interfaces.

Stability-Order Reversal in FSiY and FYSi (Y = N and P) Molecules after the Insertion of a Noble Gas Atom.

Recent theoretical prediction and experimental identification of fluorinated noble gas cyanides and isocyanides motivate us to explore a unique novel series of neutral noble gas-inserted heavier cyanofluoride isomers, FNgYSi and FNgSiY (Ng = Kr, Xe, and Rn; Y = N and P), theoretically using quantum chemical calculations. The concerned minima and saddle point geometries have been optimized using DFT, MP2, and CCSD(T) methods. The precursor molecule FSiY is more stable than its isomer FYSi, and the stability order is found to be reversed after the insertion of a noble gas (Ng) atom into them which is in contrast to the previously reported FCN/FNC systems where the stability order in the precursors remains intact after the insertion of a Ng atom into them. The predicted FNgYSi molecules are metastable in nature as they are kinetically stable but thermodynamically unstable with respect to the global minima products (FYSi and Ng). All the calculations for the corresponding FNgSiY molecules clearly indicate that the less stable FNgSiY behaves similarly to the FNgYSi in all respects. The energetics, force constant, and spectroscopic data strongly reinforce the possibility of occurrence of these predicted FNgYSi and FNgSiY molecules which might be experimentally realized under suitable cryogenic condition(s).

Electric Fields Influence Intramolecular Vibrational Energy Relaxation and Line Widths.

Intramolecular vibrational energy relaxation (IVR) is fundamentally important to chemical dynamics. We show that externally applied electric fields affect IVR and vibrational line widths by changing the anharmonic couplings and frequency detunings between modes. We demonstrate this effect in benzonitrile for which prior experimental results show a decrease in vibrational line width as a function of applied electric field. We identify three major channels for IVR that depend on electric field. In the dominant channel, the electric field affects the frequency detuning, while in the other two channels, variation of anharmonic couplings as a function of field is the underlying mechanism. Consistent with experimental results, we show that the combination of all channels gives rise to reduced line widths with increasing electric field in benzonitrile. Our results are relevant for controlling IVR with external or internal fields and for gaining a more complete interpretation of line widths of vibrational Stark probes.

Mechanistic Insights about Electrochemical Proton-Coupled Electron Transfer Derived from a Vibrational Probe.

Proton-coupled electron transfer (PCET) is a fundamental step in a wide range of electrochemical processes, including those of interest in energy conversion and storage. Despite its importance, several mechanistic details of such reactions remain unclear. Here, we have combined a proton donor (tertiary ammonium) with a vibrational Stark-shift probe (benzonitrile), to track the process from the entry of the reactants into the electrical double layer (EDL), to the PCET reaction associated with proton donation to the electrode, and the formation of products. We have used operando vibrational spectroscopy and periodic density functional theory under electrochemical bias to assign the reactant and product peaks and their Stark shifts. We have identified three main stages for the progress of the PCET reaction as a function of applied potential. First, we have determined the potential necessary for desolvation of the reactants and their entry into the polarizing environment of the EDL. Second, we have observed the appearance of product peaks prior to the onset of steady state electrochemical current, indicating formation of a stationary population of products that does not turn over. Finally, more negative of the onset potential, the electrode attracts additional reactants, displacing the stationary products and enabling steady state current. This work shows that the integration of a vibrational Stark-shift probe with a proton donor provides critical insight into the interplay between interfacial electrostatics and heterogeneous chemical reactions. Such insights cannot be obtained from electrochemical measurements alone.

Surgical outcomes of Tenzel rotational flap in upper and lower lid reconstruction without repair of posterior lamella: A modified approach.

Aim: To evaluate the efficacy and usefulness of Tenzel rotational flap in upper and lower lid reconstruction in malignant tumors, to determine the anatomical alignment, functional, and cosmetic outcome after lid reconstruction and recurrence of the tumor and to observe the canthal and fornix status. Methods: Prospective, non-comparative,interventional clinical study of 30 patients over a period of 18 months. The study was conducted with strict inclusion and exclusion criteria. Evaluation parameters were LPS (Levator palpebrae superioris) action Pre and post operative, MRD-1 (Margin Reflex Distance-1) values pre and post operative, central vertical palpebral fissure height (PFH) pre and post operative,and the calculation of the created defect express in percentage preoperatively. None of the case posterior lamina was repaired. It formed or strengthened automatically. Results: The diagnosis of Sebaceous cell carcinoma was 14/30 by FNAC and 17/30 by histopathology. The mean MRD-1 pre-operatively was -1.09 ± 1.54 mm to 4.02 ± 0.36 mm postoperatively in the upper lid. The mean LPS action pre-operatively was 4.35 ± 0.96 mm to 12.42 ± 1.24 mm postoperatively in the upper lid tumor. The mean pre-operative central palpebral aperture was 4.76 ± 0.88 mm and post-operative central palpebral aperture was 10.47 ± 0.88 mm in the upper lid tumor. The mean incision length was 8.16 ± 0.61 mm in upper lid and 9.27 ± 0.87 mm in lower lid Tenzel reconstruction respectively. In all the cases, posterior lamella grew normally. In addition, no strengthening procedure was required. Conclusion: This reconstructive procedure was useful to repair 40%-60% of the upper lid and 40%-70% created a defect in the lower eyelid after the removal of the malignant tumor. Histopathological diagnosis of the specimen was more accurate than FNAC. No repair of posterior lamella was made. No extra surgical procedure was needed. Thus, the surgical procedure time was markedly reduced. After the surgery, all the patients presented a good uplift of the upper lid, good closure of the eyelids, and were visually and functionally well rehabilitated. The aesthetic appearance was excellent.

Electric Fields at Metal-Surfactant Interfaces: A Combined Vibrational Spectroscopy and Capacitance Study.

Surfactants modulate interfacial processes. In electrochemical CO2 reduction, cationic surfactants promote carbon product formation and suppress hydrogen evolution. The interfacial field produced by the surfactants affects the energetics of electrochemical intermediates, mandating their detailed understanding. We have used two complementary tools-vibrational Stark shift spectroscopy which probes interfacial fields at molecular length scales and electrochemical impedance spectroscopy (EIS) which probes the entire double layer-to study the electric fields at metal-surfactant interfaces. Using a nitrile as a probe, we found that at open-circuit potentials, cationic surfactants produce larger effective interfacial fields (∼-1.25 V/nm) when compared to anionic surfactants (∼0.4 V/nm). At a high bulk surfactant concentration, the surface field reaches a terminal value, suggesting the formation of a full layer, which is also supported by EIS. We propose an electrostatic model that explains these observations. Our results help in designing tailored surfactants for influencing electrochemical reactions via the interfacial field effect.

Functional insights into the mode of DNA and ligand binding of the TetR family regulator TylP from Streptomyces fradiae.

Tetracycline repressors (TetRs) modulate multidrug efflux pathways in several pathogenic bacteria. In Streptomyces, they additionally regulate secondary metabolic pathways like antibiotic production. For instance, in the antibiotic producer Streptomyces fradiae, a layered network of TetRs regulates the levels of the commercially important antibiotic tylosin, with TylP occupying the top of this cascading network. TetRs exist in two functional states, the DNA-bound and the ligand-bound form, which are allosterically regulated. Here, to develop deeper insights into the factors that govern allostery, the crystal structure of TylP was solved to a resolution of 2.3 Å. The structure revealed that TylP possesses several unique features; notably, it harbors a unique C-terminal helix-loop extension that spans the entire length of the structure. This anchor connects the DNA-binding domain (DBD) with the ligand-binding domain (LBD) via a mix of positively charged and hydrogen-bonding interactions. Supporting EMSA studies with a series of ΔC truncated versions show that a systematic deletion of this region results in complete loss of DNA binding. The structure additionally revealed that TylP is markedly different in the orientation of its DBD and LBD architecture and the dimeric geometry from its hypothesized Streptomyces homologue CprB, which is a γ-butyrolactone regulator. Rather, TylP is closer in structural design to macrolide-binding TetRs found in pathogens. Supporting molecular dynamic studies suggested that TylP binds a macrolide intermediate in the tylosin pathway. Collectively, the structure along with corroborating biochemical studies provided insights into the novel mode of regulation of TetRs in antibiotic-producing organisms.