Kinetic Model for Predicting Perfluoroalkyl Acid Degradation During UV-Sulfite Treatment

Hydrated electron (eaq-) treatment processes show great potential in remediating recalcitrant water contaminants, including perfluoroalkyl and polyfluoroalkyl substances (PFAS). However, treatment efficacy depends upon many factors relating to source water composition, UV light source characteristics, and contaminant reactivity. Here, we provide critical insights into the complex roles of solution parameters on contaminant abatement through application of a UV-sulfite kinetic model that incorporates first-principles information on eaq- photogeneration and reactivity. The model accurately predicts decay profiles of short-chain perfluoroalkyl acids (PFAAs) during UV-sulfite treatment and facilitates quantitative interpretation of the effects of changing solution composition on PFAS degradation rates. Model results also confirm that the enhanced degradation of PFAAs observed under highly alkaline pH conditions results from changes in speciation of nontarget eaq- scavengers. Reverse application of the model to UV-sulfite data collected for longer chain PFAAs enabled estimation of bimolecular rate constants (k2, M-1 s-1), providing an alternative to laser flash photolysis (LFP) measurements that are not feasible due to the water solubility limitations of these compounds. The proposed model links the disparate means of investigating eaq- processes, namely, UV photolysis and LFP, and provides a framework to estimate UV-sulfite treatment efficacy of PFAS in diverse water sources.

Chemical bonding in potential PFAS products from the thermal degradation of energetic devices, a DFT analysis

This work investigates stability and chemical bonding in possible per- and polyfluoroalkyl substances (PFAS) generated through the disposal of munitions in controlled detonations and open burns. Density functional theory (DFT) calculations were used to determine bond dissociation enthalpies (BDEs), activation energies, and other chemical properties. Calculated parameters were used to determine the functional groups most likely to be present based on the level of fluorination and the position of fluorines. In compounds that form C-O bonds, the presence of α-fluorines significantly strengthens the C-O bond by ∼4-18 kcal/mol. The results of this study indicate that fluoroalkyl alcohols are a very likely product of the disposal of munitions. This work was designed to expedite the analytical process of confirming that PFAS are created from current disposal methods of energetic devices by providing insight as to of what types of compounds should be expected. The PFAS generated in such reactions are expected to contain some functional groups (i.e., nitro and nitrite) that have not been known to exist as a result of the environmental degradation of industrially relevant PFAS, therefore, they may have been overlooked before. These initial results imply that PFAS with nitro functionalities may be formed in these conditions considering the abundance of NO2 radicals expected to be present as well as the strength of the C-N bond that can form (∼40-50 kcal/mol) whereas with nitroso functionalities are not expected to be found since the bonds formed are much weaker (∼25-35 kcal/mol), and nitrosoalkanes are known to decompose under mild conditions. Although these results are promising, analytical work is needed to assess the conclusions of this study in real systems.

Influence of Carbonate Speciation on Hydrated Electron Treatment Processes

Advanced reduction processes (ARPs) that generate hydrated electrons (e_aq^-; e.g., UV-sulfite) have emerged as a promising remediation technology for recalcitrant water contaminants, including per- and polyfluoroalkyl substances (PFASs). The effectiveness of ARPs in different natural water matrices is determined, in large part, by the presence of non-target water constituents that act to quench e_aq^- or shield incoming UV photons from the applied photosensitizer. This study examined the pH-dependent quenching of e_aq^- by ubiquitous dissolved carbonate species (H₂CO₃*, HCO₃^-, and CO₃^2-) and quantified the relative importance of carbonate species to other abundant quenching agents (e.g., H₂O, H⁺, HSO₃^-, and O_2(aq)) during ARP applications. Analysis of laser flash photolysis kinetic data in relation to pH-dependent carbonate acid-base speciation yields species-specific bimolecular rate constants for e_aq^- quenching by H₂CO₃*, HCO₃^-, and CO₃^2- (kH2CO3* = 2.23 ± 0.42 × 10⁹ M^-1 s^-1, kHCO3- = 2.18 ± 0.73 × 10⁶ M^-1 s^-1, and kCO32- = 1.05 ± 0.61 × 10⁵ M^-1 s^-1), with quenching dominated by H₂CO₃* (which includes both CO_2(aq) and H₂CO₃) at moderately alkaline pH conditions despite it being the minor species. Attempts to apply previously reported rate constants for e_aq^- quenching by CO_2(aq), measured in acidic solutions equilibrated with CO_2(g), overpredict quenching observed in this study at higher pH conditions typical of ARP applications. Moreover, kinetic simulations reveal that pH-dependent trends reported for UV-sulfite ARPs that have often been attributed to e_aq^- quenching by varying [H⁺] can instead be ascribed to variable acid-base speciation of dissolved carbonate and the sulfite sensitizer.

Ultra-short chain fluorocarboxylates exhibit wide ranging reactivity with hydrated electrons

Recent reports demonstrate that technologies generating hydrated electrons (e_aq^-; e.g., UV-sulfite) are a promising strategy for destruction of per- and polyfluoroalkyl substances, but fundamental rate constants are lacking. This work examines the kinetics and mechanisms of e_aq^- reactions with ultra-short chain (C2-C4) fluorocarboxylates using experimental and theoretical approaches. Laser flash photolysis (LFP) was used to measure bimolecular rate constants (k₂; M^-1 s^-1) for e_aq^- reactions with thirteen per-, and for the first time, polyfluorinated carboxylate structures. The measured k₂ values varied widely from 5.26 × 10⁶ to 1.30 × 10⁸ M^-1s^-1, a large range considering the minor structural changes among the target compounds. Molecular descriptors calculated using density functional theory did not reveal correlation between k₂ values and individual descriptors when considering the whole dataset, however, semiquantitative correlation manifests when grouping by similar possible initial reduction event such as electron attachment at the α-carbon versus β- or γ-carbons along the backbone. From this, it is postulated that fluorocarboxylate reduction by e_aq^- occurs via divergent mechanisms with the possibility of non-degradative pathways being prominent. These mechanistic insights provide rationale for contradictory trends between LFP-derived k₂ values and apparent degradation rates recently reported in UV-sulfite constant irradiation treatment experiments.

High-temperature decomposition chemistry of trimethylsiloxane surfactants, a potential Fluorine-Free replacement for fire suppression

Per- and polyfluoroalkyl substances (PFAS) have become global environmental contaminants due to being notoriously difficult to degrade, and it has become increasingly important to employ suitable PFAS alternatives, especially in aqueous film-forming foams (AFFF). Trimethylsiloxane (TriSil) surfactants are potential fluorine-free replacements for PFAS in fire suppression technologies. Yet because these compounds may be more susceptible to high-temperature decomposition, it is necessary to assess the potential environmental impact of their thermal degradation products. Our study analyzes the high-temperature degradation of a truncated trimethylsiloxane (TriSil-1n) surfactant based on quantum mechanical methods. The degradation chemistry of TriSil-1n was studied through radical formation and propagation initiated from two prominent pathways (unimolecular and bimolecular reactions) at both 298 K and 1200 K, a relevant temperature in flames and thermal incinerators. Regardless of the pathway taken and temperature, all radical intermediates stemmed from the polyethylene glycol chain and primarily formed stable polydimethylsiloxanes (PDMS) and small organics such as ethylene, formaldehyde, and acetaldehyde, among other products. The major degradation products of TriSil-1n resulting from high-temperature thermal degradation as predicted by this study would be relatively less harmful to the environment compared to PFAS incineration/combustion products from previous research, supporting the replacement of PFAS with TriSil surfactants.

Phototriggered Desorption of Hydrogen, Ethylene, and Carbon Monoxide from a Cu(I)-Modified Covalent Organic Framework

Materials that are capable of adsorbing and desorbing gases near ambient conditions are highly sought after for many applications in gas storage and separations. While the physisorption of typical gases to high surface area covalent organic frameworks (COFs) occurs through relatively weak intermolecular forces, the tunability of framework materials makes them promising candidates for tailoring gas sorption enthalpies. The incorporation of open Cu(I) sites into framework materials is a proven strategy to increase gas uptake closer to ambient conditions for gases that are capable of π-back-bonding with Cu. Here, we report the synthesis of a Cu(I)-loaded COF with subnanometer pores and a three-dimensional network morphology, namely Cu(I)-COF-301. This study focused on the sorption mechanisms of hydrogen, ethylene, and carbon monoxide with this material under ultrahigh vacuum using temperature-programmed desorption and Kissinger analyses of variable ramp rate measurements. All three gases desorb near or above room temperature under these conditions, with activation energies of desorption (E _des) calculated as approximately 29, 57, and 68 kJ/mol, for hydrogen, ethylene, and carbon monoxide, respectively. Despite these strong Cu(I)-gas interactions, this work demonstrated the ability to desorb each gas on-demand below its normal desorption temperature upon irradiation with ultraviolet (UV) light. While thermal imaging experiments indicate that bulk photothermal heating of the COF accounts for some of the photodriven desorption, density functional theory calculations reveal that binding enthalpies are systematically lowered in the COF-hydrogen matrix excited state initiated by UV irradiation, further contributing to gas desorption. This work represents a step toward the development of more practical ambient temperature storage and efficient regeneration of sorbents for applications with hydrogen and π-accepting gases through the use of external photostimuli.

Computational protocol for predicting 19 F NMR chemical shifts for PFAS and connection to PFAS structure

Per- and polyfluoroalkyl substances (PFAS) are robust "forever" chemicals that have become global environmental contaminants due to their inability to degrade using traditional techniques. In addition to the persistent nature of PFAS, the structural and functional diversity in PFAS creates a unique challenge in identification and remediation. Their identification is further complicated by the absence of standards for many PFAS. This work is aimed at developing a protocol for computing and establishing accurate ¹⁹ F NMR chemical shifts for PFAS using density functional theory (DFT), which can aid in the identification of PFAS. The impact of solvation and basis sets was evaluated by comparing the computed data with the experimental measurements. Results showed the addition of dispersion corrections in the methodology improve the accuracy of calculated NMR parameters within 4 ppm of the experimental values. Adding a second diffuse function and additional polarization did not improve the accuracy, likely because of the electronegativity of fluorine which does not allow the electron density of fluorine atoms to be polarized. The inclusion of various implicit solvation (DMSO, chloroform, and water) yielded negligible differences in accuracy, and were overall less accurate than the gas phase calculations. The most accurate methodology was then applied to more environmentally relevant PFAS, and the impact of helical nature on the NMR signatures was evaluated. The implication of this work is to be able to improve the identification of structurally diverse PFAS using the ¹⁹ F NMR.

Role of Explicit Hydration in Predicting the Aqueous Standard Reduction Potential of Sulfate Radical Anion by DFT and Insight into the Influence of pH on the Reduction Potential

Sulfate radical anion (SO₄^•-) is a potent oxidant capable of destroying recalcitrant environmental contaminants such as perfluoroalkyl carboxylic acids. In addition, it is thought to participate in important atmospheric reactions. Its standard reduction potential (E°) is fundamental to its reactivity. Using theoretical methods to accurately predict the aqueous phase E° requires solvation with explicit water molecules. Herein, using density functional theory, we calculated the aqueous E° of SO₄^•- and evaluated sensitivity to explicit water count. The E° increased considerably with more waters until ca. 24 were included, after which change in E° was small. When a proton was added to these systems, the E° was similar regardless of the explicit water count and this value was similar to the E° for systems with a large number of explicit waters but no proton. This result agrees with literature evidence that the E° is pH independent. Natural Bond Orbital natural population analysis indicated that in the case of both SO₄^2- and SO₄^•-, considerable charge was donated from the SO₄ center to the explicit solvation shells.

Diazaborines oxidize slowly with H2O2 but rapidly with peroxynitrite in aqueous buffer

Reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) and peroxynitrite (ONOO^-) oxidize arylboronic acids to their corresponding phenols. When used in molecular imaging probes and in ROS-responsive molecules, however, simple arylboronic acids struggle to discriminate between H₂O₂ and ONOO^- because of their fast rate of reaction with both ROS. Here, we show that diazaborines (DABs) react slowly with H₂O₂ but rapidly with peroxynitrite in an aqueous buffer. In addition to their slow reaction with H₂O₂, the immediate product of DAB oxidation with H₂O₂ and ONOO^- can yield a kinetically trapped CN Z-isomer that slowly equilibrates with its E-isomer. Taken together, our work shows that diazaborines exhibit enhanced kinetic discrimination between H₂O₂ and ONOO^- compared to arylboronic acids, opening up new opportunities for diazaborine-based tools in chemical biology.

Structure and Reactivity of Alloxan Monohydrate in the Liquid Phase

Alloxan is an important toxic glucose analogue used to induce diabetes in lab test animals. Once regarded as a "problem structure," the condensed-phase structure of anhydrous alloxan has largely been settled, but literature inconsistencies remain for the structure of the typically employed reagent alloxan monohydrate. Due to the criticality of structure-function relationships, we have used ¹H/¹³C{¹H} NMR, IR spectroscopy, as well as quantum mechanical (QM) calculations to probe the liquid-phase structure and reactivity of alloxan monohydrate. In protic solvents (D₂O and acetic acid-d₄), hydration at the C5 carbonyl of alloxan monohydrate occurs quantitatively to form the C5 gem-diol (5,5'-dihydroxybarbituric acid). In the aprotic solvent dimethyl sulfoxide (DMSO)-d₆, there exists a mixture of the C5 gem-diol and planar tetraketo form of alloxan monohydrate. QM calculations explain the solvent-dependent hydration reactivity, where a solvent-assisted H-atom transfer mechanism lowers the activation energy of water addition at the C5 carbonyl by ∼16 or 27 kcal/mol in water or acetic acid, respectively, compared to the unassisted hydration reaction. Prompt recrystallization of alloxan monohydrate from boiling water does not alter the structure of the reagent. These findings probe the exact structure of alloxan monohydrate to guide future research efforts in biological sciences and in organic synthesis.

Understanding Fragmentation of Organic Small Molecules in Atom Probe Tomography

In atom probe tomography of molecular organic materials, field ionization of either entire molecules or molecular fragments can occur, but the mechanism governing this behavior was not previously understood. This work explains when a doubly ionized small molecule organic material is expected to undergo fragmentation. We find that multiple detection events arising from post-ionization fragmentation of a parent molecular dication into two daughter ions is well explained by the free energy and geometries of the molecules computed using density functional theory. Of the systems studied, exergonic free energies for formation of the daughter ions, smaller activation energies for dissociation, and increases in bond length are all found to be quantitative predictors for ion fragmentation. This work expands the applicability of atom probe tomography to organic materials by increasing the fundamental understanding of processes occurring during this analysis technique.

Periodic Trends behind the Stability of Metal Catalysts Supported on Graphene with Graphitic Nitrogen Defects

This study explored the fundamental chemical intricacies behind the interactions between metal catalysts and carbon supports with graphitic nitrogen defects. These interactions were probed by examining metal adsorption, specifically, the location of adsorption and the electronic structure of metal catalysts as the basis for the metal-support interactions (MSIs). A computational framework was developed, and a series of 12 transition metals was systematically studied over various graphene models with graphitic nitrogen defect(s). Different modeling approaches served to provide insights into previous MSI computational discrepancies, reviewing both truncated and periodic graphene models. The computational treatment affected the magnitudes of adsorption energies between the metals and support; however, metals generally followed the same trends in their MSI. It was found that the addition of the nitrogen dopant improved the MSI by promoting electronic rearrangement from the metals' d- to s-orbitals for greater orbital overlap with the carbon support, shown with increased favorable adsorption. Furthermore, the study observed periodic trends that were adept descriptors of the MSI fundamental chemistries.

Role of pH in the Transformation of Perfluoroalkyl Carboxylic Acids by Activated Persulfate: Implications from the Determination of Absolute Electron-Transfer Rates and Chemical Computations

Perfluoroalkyl carboxylic acids (PFCAs) are ubiquitous contaminants known for their bioaccumulation, toxicological harm, and resistance to degradation. Remediating PFCAs in water is an ongoing challenge with existing technologies being insufficient or requiring additional disposal. An emergent approach is using activated persulfate, which degrades PFCAs through sequential scission of CF₂ equivalents yielding shorter-chain homologues, CO₂ and F^-. This transformation is thought to be initiated by single electron transfer (SET) from the PFCA to the activate oxidant, SO₄^•-. A pronounced pH effect has been observed for thermally activated persulfate PFCA transformation. To evaluate the role of pH during SET, we directly determined absolute rate constants for perfluorobutanoic acid and trifluoroacetic acid oxidation by SO₄^•- in the pH range of 0.5-4.0 using laser flash photolysis. The average of the rate constants for both substrates across all pH values was 9 ± 2 × 10³ M^-1 s^-1 (±2σ), implying that acid catalysis of thermal persulfate activation may be the primary culprit of the observed pH effect, instead of pH influencing the SET step. In addition, density functional theory was used to investigate if SO₄^•-protonation might enhance PFCA transformation kinetics. We found that when calculations include explicit water molecules, direct SO₄^•- protonation does not occur.

Cognitive Performance and Neuro-Metabolites in HIV Using 3T Magnetic Resonance Spectroscopy: A Cross-Sectional Study from India

BACKGROUND

Cognitive impairment in patients with human immunodeficiency virus (HIV) is associated with higher morbidity. The prevalence of the metabolite changes in the brain associated with cognitive impairment in anti-retroviral therapy naïve patients with HIV is unknown.

OBJECTIVE

To estimate the prevalence of the neurometabolites associated with cognitive impairment in antiretroviral therapy (ART) naïve patients with HIV.

METHODS

We conducted a cross-sectional study among ART naïve patients with HIV aged 18-50 years in a tertiary care center in India. Cognition was tested using the Post Graduate Institute battery of brain dysfunction across five domains; memory, attention-information processing, abstraction executive, complex perceptual, and simple motor skills. We assessed the total N-acetyl aspartyl (tNAA), creatine (tCr) and glutamate + glutamine (Glx) using 3T magnetic resonance spectroscopy. Cognitive impairment was defined as an impairment in ≥2 domains.

RESULTS

Among 43 patients eligible for this study, the median age was 32 years (IQR 29, 40) and 30% were women. Median CD4 count and viral load were 317 cells/μL (IQR 157, 456) and 9.3 copies/ μL (IQR 1.4, 38), respectively. Impairment in at least one cognitive domain was present in 32 patients (74.4%). Impairment in simple motor skills and memory was present in 46.5% and 44% of patients, respectively. Cognitive impairment, defined by impairment in ≥2 domains, was found in 22 (51.2%) patients. There was a trend towards higher concentration of tNAA (7.3 vs. 7.0 mmol/kg), tGlx (9.1 vs. 8.2 mmol/kg), and tCr (5.5 vs. 5.2 mmol/kg) in the frontal lobe of patients with cognitive impairment vs. without cognitive impairment but it did not reach statistical significance (p>0.05 for all). There was no difference in the concentration of these metabolites in the two groups in the basal ganglia.

CONCLUSION

There is a high prevalence of cognitive impairment in ART naïve patients with HIV. There is no difference in metabolites in patients with or without cognitive impairment. Further studies, with longitudinal follow-up are required to understand the underlying pathophysiological mechanisms.

The management of women with thoracic endometriosis: a national survey of British gynaecological endoscopists

OBJECTIVES

This study evaluates current national opinions on screening, diagnosis, and management of thoracic endometriosis.

BACKGROUND

Thoracic endometriosis is a rare but serious condition with four main clinical presentations: pneumothorax, haemoptysis, haemothorax, and pulmonary nodules. There are no specialist centres in the United Kingdom despite growing patient desire for recognition, investigation, and treatment.

METHODS

We distributed a multiple-choice email survey to senior members of the British Society for Gynaecological Endoscopy. Descriptive statistics were used to present the results. Results: We received 67 responses from experienced clinicians having provided over 800 combined years of endometriosis patient care. The majority of respondents managed over 100 endometriosis patients annually, for more than five years. Over one third had never managed a patient with symptomatic thoracic endometriosis; just 9% had managed more than 30 cases over the course of their career. Screening varied by modality with only 4% of clinicians always taking a history of respiratory symptoms while 69% would always screen for diaphragmatic endometriosis during laparoscopy. The management of symptomatic thoracic endometriosis varied widely with the commonest treatment being surgery followed by hormonal therapies. Regarding management, 71% of respondents felt the team should comprise of four or more different specialists, and 56% believed care should be centralised either regionally or nationally.

CONCLUSIONS

Thoracic endometriosis is poorly screened for amongst clinicians with varied management lacking a common diagnostic or therapeutic pathway in the United Kingdom. Specialists expressed a preference for women to be managed in a large multidisciplinary team setting at a regional or national level.

106 Exogenous melatonin administration improves behavioural signs, serum melatonin, testosterone, and semen quality in male dromedary (Camelus dromedarius) camels

The present study aimed to evaluate the effects of exogenous administration of melatonin to male camels on reproductive behaviour, seminal parameters, and serum concentrations of melatonin and testosterone during the non-breeding and subsequent breeding seasons. In September 2018, male camels (n=12) were randomly allocated to subcutaneous injections of either melatonin (MLT, 0.643 mg/kg; n=6) dissolved in corn oil, or plain corn oil; (control n=6). The camels were observed for behavioural signs of rut. A second dose of either MLT (1 mg/kg) or corn oil (control) was administered on 7 October 2018 subcutaneously, as camels did not show any change in behaviour until 6 October 2018, and the camels were again observed for behavioural signs of rut. Blood was collected from all camels on 1 September 2018, and then at weekly intervals until 7 January 2019. The serum was separated and stored until further assay of serum melatonin and testosterone using ELISA kits. Semen was collected from camels showing signs of rut period, and the reaction time, copulation time, and seminal parameters were evaluated. Data obtained was analysed by using the computer program SPSS (version 25; IBM Corp.), and means and standard errors were compared. Male reproductive behaviours (protrusion of soft palate, poll gland secretions, frequent urination, increased frothy salivation) were more pronounced in MLT-treated camels (83.33%) than in control camels (50%). Reaction time and copulation times were lower (112.81±30.06s and 229.8±37.91s) in MLT-treated camels than in controls (359.00±41.35s and 301.89±93.90s). Higher semen volume was observed in MLT-treated (5.34±2.06mL) than in control (3.11±1.75mL) camels (P<0.01). Semen collected from MLT-treated camels had more gel formation (81.25%), significantly higher sperm motility (67.50±2.32%), and increased sperm concentration (326.56±38.67 million mL−1) compared with samples obtained from the control males (P<0.01). Serum melatonin concentrations increased in both treated and control camels during the breeding season compared with concentrations before the breeding season. In MLT-treated camels, serum melatonin concentrations increased significantly and continued to be significantly higher than that in control camels for the entire study period (P<0.01). Serum testosterone concentrations were higher in both MLT-treated and control camels during the breeding season compared with those during the non-breeding season (P<0.01). We concluded that exogenous subcutaneous MLT administration improves sexual behaviour, seminal parameters, and serum testosterone concentrations during both the non-breeding and breeding seasons.

THU0415 MELTING OF TOPHI WITH LOCAL STEROIDS IN CHRONIC TOPHACEOUS GOUT: AN OBSERVATIONAL STUDY

Background:

Chronic tophaceous gout is usually difficult to treat with urate lowering therapy (ULT) [1]. Faster resolution of tophi has been seen with use of pegloticase [2], but this drug is costly and not widely available. Local steroid use is recommended in acute gouty arthritis but its role in reduction of tophi has not been studied. This study was aimed to see the effect of local steroids in tophi resolution.

Objectives:

To study the change in size of gouty tophi with local steroid injection compared to conventional treatment.

Methods:

Four crystal proven chronic tophaceous gout patients with multiple tophi were screened and enrolled in the study after taking informed consent. Total 12 tophi in 4 patients were imaged by using Duel Energy Computed Scan (DECT) for their size and volume. All 4 patients were treated with ULT as per recommended dose to achieve target serum uric acid (SUV) level. Six tophi were treated with local steroids injection (methylprednisolone acetate) at two months interval till complete resolution of tophi. Dose of steroid varied from 10 mg to 40 mg depending upon tophi size but subsequent repeat doses were same in each tophi. Six tophi not treated with local steroid served as internal control in the same patients. All 4 patients were followed up regularly in out-patient department to monitor treatment response and local side effects if any.

Results:

All 4 patients achieved target SUV (<356 µmol/L) at three months of follow up. Six tophi which were treated with local steroids injection clinically had marked reduction in size at 7-12 months of follow up [Table-1], while other 6 tophi which served as internal control had no clinically significant change in size and volume of tophi. DECT was repeated in the same settings to confirm the clinical findings. DECT revealed near complete resolution of 5 tophi [Image-1], and 50% reduction in size of one tophi. Six tophi which were not treated with local steroid had no significant reduction in size in DECT as well. Only side effect noted was skin discoloration in 5 out of 6 injected sites, none of the tophi had infection.

Conclusion:

Interestingly this is the first such study to document the use of local steroid in tophi. Thus intralesional steroids can be alternative to pegloticase or surgery where faster dissolution of tophi is required. This observation needs to be explored in large number of patients to calculate the total dose requirement of steroid as per volume and urate burden of tophi. Possible explanation of melting tophi with steroids is breaking down outer fibrous layer of tophi by local steroids which might be acting as barrier in dissolution of urate crystals with ULT.

References:

[1]Dalbeth N, House ME, Horne A et al. Prescription and dosing of urate-lowering therapy, rather than patient behaviours, are the key modifiable factors associated with targeting serum urate in gout.BMC Musculoskelet Disord2012;13:174

[2]Baraf HS, Becker MA, Gutierrez-Urena SR, et al: Tophus burden reduction with pegloticase: results from phase 3 randomized trials and open-label extension in patients with chronic gout refractory to conventional therapy. Arthritis Res Ther 15:R137, 2013

Table 1.Age/sexTotal TophiTreated TophiOutcome of treated tophiInternal control tophiDuration in monthsCase 122/M21Near complete resolutionNo Change 7Case 245/F11Complete resolutionNA 8Case 358/M52Near complete resolutionNo change12Case 424/M42Completely resolved=1,50% size reduction=1No change12Figure 1

a: DECT of Rt foot shows urate crystal deposition at 1stMTP joint and 5thtoe. Figure1b: DECT after 7 months of steroid injection in Rt 1stMTP joint tophi shows almost complete resolution but no change in 5thtoe tophi (served as internal control).

Disclosure of Interests: :

None declared

Investigating the Photochemistry of C7 and C8 Functionalized N(5)-Ethyl-flavinium Cation: A Computational Study

Flavins are a diverse set of compounds with a wide variety of biological and nonbiological applications. Applications of flavins receiving attention recently consist of electro- and photocatalytic oxidation of substrates for organic synthesis, bioengineered nanotechnology, and water splitting catalysts, among others. While there is vast knowledge regarding the structure-property relationships of flavins and their electrochemistry, there is much less work elucidating the structure property relationships as they pertain to flavinium photochemistry. Herein, we report the effect of molecular tailoring on the molecular properties of N(5)-ethyl-flavinium cation (Et-Fl⁺), a derivative of the biocatalytic coenzyme riboflavin, by incorporating electron withdrawing and donating groups at the C7 and C8 position of the isoalloxazine ring. The presence of electron withdrawing groups at the C8 position caused a red shift in the absorption spectrum, while the electron donating groups caused a blue shift. Functionalization at the C7 position had the opposite effect on the absorption spectrum. The effects of single substitution were relatively negated with simultaneous functionalization at both the C8 and C7 positions. Difference density plots indicate no change in the nature of the S₁ excited state, which was confirmed by optimization of the excited state geometries. The results presented in this study indicate that functionalization of the isoalloxazine unit affects the photophysical properties of N(5)-ethyl-flavinium cations.

Reactive Molecular Dynamics Simulations and Quantum Chemistry Calculations To Investigate Soot-Relevant Reaction Pathways for Hexylamine Isomers

Sooting tendencies of a series of nitrogen-containing hydrocarbons (NHCs) have been recently characterized experimentally using the yield sooting index (YSI) methodology. This work aims to identify soot-relevant reaction pathways for three selected C₆H₁₅N amines, namely, dipropylamine (DPA), diisopropylamine (DIPA), and 3,3-dimethylbutylamine (DMBA) using ReaxFF molecular dynamics (MD) simulations and quantum mechanical (QM) calculations and to interpret the experimentally observed trends. ReaxFF MD simulations are performed to determine the important intermediate species and radicals involved in the fuel decomposition and soot formation processes. QM calculations are employed to extensively search for chemical reactions involving these species and radicals based on the ReaxFF MD results and also to quantitatively characterize the potential energy surfaces. Specifically, ReaxFF simulations are carried out in the NVT ensemble at 1400, 1600, and 1800 K, where soot has been identified to form in the YSI experiment. These simulations account for the interactions among test fuel molecules and pre-existing radicals and intermediate species generated from rich methane combustion, using a recently proposed simulation framework. ReaxFF simulations predict that the reactivity of the amines decrease in the order DIPA > DPA > DMBA, independent of temperature. Both QM calculations and ReaxFF simulations predict that C₂H₄, C₃H₆, and C₄H₈ are the main nonaromatic soot precursors formed during the decomposition of DPA, DIPA, and DMBA, respectively, and the associated reaction pathways are identified for each amine. Both theoretical methods predict that sooting tendency increases in the order DPA, DIPA, and DMBA, consistent with the experimentally measured trend in YSI. This work demonstrates that sooting tendencies and soot-relevant reaction pathways of fuels with unknown chemical kinetics can be identified efficiently through combined ReaxFF and QM simulations. Overall, predictions from ReaxFF simulations and QM calculations are consistent, in terms of fuel reactivity, major intermediates, and major nonaromatic soot precursors.

Characterization of the ALSEP Process at Equilibrium: Speciation and Stoichiometry of the Extracted Complex

We have determined the identity of the complexes extracted into the ALSEP process solvent from solutions of nitric acid. The ALSEP process is a new solvent extraction separation designed to separate americium and curium from trivalent lanthanides in irradiated nuclear fuel. ALSEP employs a mixture of two extractants, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and N,N,N',N'-tetra(2-ethylhexyl)diglycolamide (TEHDGA) in n-dodecane, which makes it difficult to ascertain the nature of the extracted metal complexes. It is often asserted that the weak acid extractant HEH[EHP] does not participate in the extracted complex under ALSEP extraction conditions (2-4 M HNO₃). However, the analysis of the Am extraction equilibria, Nd absorption spectra, and Eu fluorescence emission spectra of metal-loaded organic phases argues for the participation of HEH[EHP] in the extracted complex despite the high acidity of the aqueous phases. The extracted complex was determined to contain fully protonated molecules of HEH[EHP] with an overall stoichiometry of M(TEHDGA)₂(HEH[EHP])₂·3NO₃. Computations also demonstrate that replacing one TEHDGA molecule with one (HEH[EHP])₂ dimer is likely energetically favorable compared to Eu(TEHDGA)₃·3NO₃, whether the HEH[EHP] dimer is monodentate or bidentate.

Intermolecular fluoroamination of allenes towards substituted vinyl fluorides

Allene difunctionalization: Selectfluor mediated intermolecular aminofluorination of allenes with triazole and tetrazole nucleophiles towards vinyl fluorides.

Determination of Vitamin B12 in Fortified Bovine Milk- Based Infant Formula Powder, Fortified Soya-Based Infant Formula Powder, Vitamin Premix, and Dietary Supplements by Surface Plasmon Resonance: Collaborative Study

A collaborative study was conducted on an inhibition-based protein-binding assay using the Biacore Q™ biosensor instrument and the Biacore Qflex™ Kit Vitamin B12 PI. The samples studied included infant formula, cereals, premixes, vitamin tablets, dietary supplements, and baby food. The collaborative study, which involved 11 laboratories, demonstrated that the assay showed an RSDr of 1.59–27.8 and HorRat values for reproducibility of 0.34–1.89 in samples with levels ranging from ppm to ppb. The assay studied is a label-free protein binding-based assay that uses the principle of surface plasmon resonance (SPR) to measure the interaction between vitamin B12 and a specifc binding protein. A Biacore Q biosensor uses this principle to detect binding directly at the surface of a sensor chip with a hydrophilic gold-dextran surface. The instrument passes a mixture of prepared sample extract and binding protein solution across a covalently immobilized vitamin B12 chip surface, and the response is given as free-binding protein as the mixture binds to the immobilized surface. This technique uses the specifcity and robustness of the protein-ligand interaction to allow minimal sample preparation and a wide range of matrixes to be analyzed rapidly. The reagents and accessories needed to perform this assay are provided as the ready-to-use format “Qflex Kit Vitamin B12 PI.” The method is intended for routine use in the quantitative determination of vitamin B12 (as cyanocobalamin) in a wide range of food products, dietary vitamin supplements, and multivitamin premixes.

Papilloedema: diffusion-weighted imaging of optic nerve head

AIM

To establish the correlation between clinical grading of papilloedema and diffusion abnormalities of optic nerve head (ONH) on diffusion-weighted imaging (DWI).

MATERIALS AND METHODS

Brain magnetic resonance imaging (MRI), including readout segmented echo planar imaging-based DWI, was performed in 32 patients with papilloedema and the same number of age- and sex-matched controls. Clinical grading of papilloedema was done according to the modified Frisén scale. Two neuroradiologists independently evaluated the MRI for ONH hyperintensity and apparent diffusion coefficient (ADC) value of ONH. The comparison between papilloedema clinical grade and qualitative grade of ONH hyperintensity and its presence between cases and control groups were done using the Chi-square test and Fisher's exact test, respectively. The comparison between mean ADC value of ONH among different grades and between cases and controls were done using analysis of variance (ANOVA)-F-test and Student's t-test, respectively. Receiver operating characteristic (ROC) analysis was done to calculate a cut-off ADC value between the case and control groups.

RESULTS

Significant correlation between ONH hyperintensity and mean ADC value of ONH with clinical grades of papilloedema and between cases and control groups were found. ONH hyperintensity was found to be a highly sensitive (87.5% for both) and specific (specificity 97.1% and 98.6% for two observers) sign of papilloedema. A mean cut-off ONH ADC value was found to have high sensitivity (96.83%) and specificity (95.31%) to distinguish between the cases and controls.

CONCLUSIONS

Diffusion parameters of ONH have significant correlation with clinical grading of papilloedema and can serve as a surrogate marker for intracranial pressure.

Resurrection and Reactivation of Acetylcholinesterase and Butyrylcholinesterase

Organophosphorus (OP) nerve agents and pesticides present significant threats to civilian and military populations. OP compounds include the nefarious G and V chemical nerve agents, but more commonly, civilians are exposed to less toxic OP pesticides, resulting in the same negative toxicological effects and thousands of deaths on an annual basis. After decades of research, no new therapeutics have been realized since the mid-1900s. Upon phosphylation of the catalytic serine residue, a process known as inhibition, there is an accumulation of acetylcholine (ACh) in the brain synapses and neuromuscular junctions, leading to a cholinergic crisis and eventually death. Oxime nucleophiles can reactivate select OP-inhibited acetylcholinesterase (AChE). Yet, the fields of reactivation of AChE and butyrylcholinesterase encounter additional challenges as broad-spectrum reactivation of either enzyme is difficult. Additional problems include the ability to cross the blood brain barrier (BBB) and to provide therapy in the central nervous system. Yet another complication arises in a competitive reaction, known as aging, whereby OP-inhibited AChE is converted to an inactive form, which until very recently, had been impossible to reverse to an active, functional form. Evaluations of uncharged oximes and other neutral nucleophiles have been made. Non-oxime reactivators, such as aromatic general bases and Mannich bases, have been developed. The issue of aging, which generates an anionic phosphylated serine residue, has been historically recalcitrant to recovery by any therapeutic approach-that is, until earlier this year. Mannich bases not only serve as reactivators of OP-inhibited AChE, but this class of compounds can also recover activity from the aged form of AChE, a process referred to as resurrection. This review covers the modern efforts to address all of these issues and notes the complexities of therapeutic development along these different lines of research.

Correction: Unravelling the impact of hydrocarbon structure on the fumarate addition mechanism – a gas-phase ab initio study

Correction for ‘Unravelling the impact of hydrocarbon structure on the fumarate addition mechanism – a gas-phase ab initio study’ by Vivek S. Bharadwaj et al., Phys. Chem. Chem. Phys., 2015, 17, 4054–4066.

Intermediate selectivity in the oxidation of phenols using plasmonic Au/ZnO photocatalysts

Tunable reaction selectivity on a single catalyst is a continual goal in chemical syntheses. Herein, we report an unexpected light-directed intermediate selectivity using well-known plasmonic photocatalysts. We observed distinct intermediate selectivity behaviors between using UV and visible light irradiations. Chemical computations and quenching experiments suggest that the radicals generated by the plasmonic excitation govern the light-directed selectivity. The broader impact of this work ranges from selective yield of desirable intermediates for subsequent syntheses without tedious separation procedures, to arousing interest in examining new opportunities for plasmonic photocatalysts.

Quantum-Mechanical Study of the Reaction Mechanism for 2π-2π Cycloaddition of Fluorinated Methylene Groups

Perfluorocyclobutyl polymers are thermally and chemically stable, may be produced without a catalyst via thermal 2π-2π cycloaddition, and can form block structures, making them suitable for commercialization of specialty polymers. Thermal 2π-2π cycloaddition is a rare reaction that begins in the singlet state and proceeds through a triplet intermediate to form an energetically stable four-membered ring in the singlet state. This reaction involves two changes in spin state and, thus, two spin-crossover transitions. Presented here are density functional theory calculations that evaluate the energetics and reaction mechanisms for the dimerizations of two different polyfluorinated precursors, 1,1,2-trifluoro-2-(trifluoromethoxy)ethane and hexafluoropropylene. The spin-crossover transition states are thoroughly investigated, revealing important kinetics steps and an activation energy for the gas-phase cycloaddition of two hexafluoropropene molecules of 36.9 kcal/mol, which is in good agreement with the experimentally determined value of 34.3 kcal/mol. It is found that the first carbon-carbon bond formation is the rate-limiting step, followed by a rotation about the newly formed bond in the triplet state that results in the formation of the second carbon-carbon bond. Targeting the rotation of the C-C bond, a set of parameters were obtained that best produce high molecular weight polymers using this chemistry.

Unravelling the impact of hydrocarbon structure on the fumarate addition mechanism--a gas-phase ab initio study

The fumarate addition reaction mechanism is central to the anaerobic biodegradation pathway of various hydrocarbons, both aromatic (e.g., toluene, ethyl benzene) and aliphatic (e.g., n-hexane, dodecane). Succinate synthase enzymes, which belong to the glycyl radical enzyme family, are the main facilitators of these biochemical reactions. The overall catalytic mechanism that converts hydrocarbons to a succinate molecule involves three steps: (1) initial H-abstraction from the hydrocarbon by the radical enzyme, (2) addition of the resulting hydrocarbon radical to fumarate, and (3) hydrogen abstraction by the addition product to regenerate the radical enzyme. Since the biodegradation of hydrocarbon fuels via the fumarate addition mechanism is linked to bio-corrosion, an improved understanding of this reaction is imperative to our efforts of predicting the susceptibility of proposed alternative fuels to biodegradation. An improved understanding of the fuel biodegradation process also has the potential to benefit bioremediation. In this study, we consider model aromatic (toluene) and aliphatic (butane) compounds to evaluate the impact of hydrocarbon structure on the energetics and kinetics of the fumarate addition mechanism by means of high level ab initio gas-phase calculations. We predict that the rate of toluene degradation is ∼100 times faster than butane at 298 K, and that the first abstraction step is kinetically significant for both hydrocarbons, which is consistent with deuterium isotope effect studies on toluene degradation. The detailed computations also show that the predicted stereo-chemical preference of the succinate products for both toluene and butane are due to the differences in the radical addition rate constants for the various isomers. The computational and kinetic modeling work presented here demonstrates the importance of considering pre-reaction and product complexes in order to accurately treat gas phase systems that involve intra and inter-molecular non-covalent interactions.

Wellen's syndrome: Challenges in diagnosis

Wellen's syndrome is a pre-infarction stage of coronary artery disease characterised by predefined clinical and electrocardiographic (ECG) criteria of a subgroup of patients with myocardial ischaemia. Early recognition and appropriate intervention of this syndrome carry significant diagnostic and prognostic value. We report this unusual syndrome in an elderly man who presented with recurrent angina and characteristic ECG changes as T-waves inversion in the precordial leads, especially in V2-V6 during pain-free periods and ECG obtained during episodes of pain demonstrating upright T-waves with possible elevated ST segments from V1-V4. Cardiac enzymes were positive and coronary angiography revealed critical stenosis in the proximal left anterior descending artery. It is important to timely identify this condition and intervene appropriately as these patients may develop extensive myocardial infarction that carries a significant morbidity and mortality.