Human-Specific NOTCH2NL Genes Expand Cortical Neurogenesis through Delta/Notch Regulation.

The cerebral cortex underwent rapid expansion and increased complexity during recent hominid evolution. Gene duplications constitute a major evolutionary force, but their impact on human brain development remains unclear. Using tailored RNA sequencing (RNA-seq), we profiled the spatial and temporal expression of hominid-specific duplicated (HS) genes in the human fetal cortex and identified a repertoire of 35 HS genes displaying robust and dynamic patterns during cortical neurogenesis. Among them NOTCH2NL, human-specific paralogs of the NOTCH2 receptor, stood out for their ability to promote cortical progenitor maintenance. NOTCH2NL promote the clonal expansion of human cortical progenitors, ultimately leading to higher neuronal output. At the molecular level, NOTCH2NL function by activating the Notch pathway through inhibition of cis Delta/Notch interactions. Our study uncovers a large repertoire of recently evolved genes active during human corticogenesis and reveals how human-specific NOTCH paralogs may have contributed to the expansion of the human cortex.

Enhanced Reactivity through Equatorial Sulfur Coordination in Nonheme Iron(IV)-Oxo Complexes: Insights from Experiment and Theory.

Sulfur ligation in metalloenzymes often gives the active site unique properties, whether it is the axial cysteinate ligand in the cytochrome P450s or the equatorial sulfur/thiol ligation in nonheme iron enzymes. To understand sulfur ligation to iron complexes and how it affects the structural, spectroscopic, and intrinsic properties of the active species and the catalysis of substrates, we pursued a systematic study and compared sulfur with amine-ligated iron(IV)-oxo complexes. We synthesized and characterized a biomimetic N4S-ligated iron(IV)-oxo complex and compared the obtained results with an analogous N5-ligated iron(IV)-oxo complex. Our work shows that the amine for sulfur replacement in the equatorial ligand framework leads to a rate enhancement for oxygen atom and hydrogen atom transfer reactions. Moreover, the sulfur-ligated iron(IV)-oxo complex reacts through a different reaction mechanism as compared to the N5-ligated iron(IV)-oxo complex, where the former reacts through hydride transfer with the latter reacting via radical pathways. We show that the reactivity differences are caused by a dramatic change in redox potential between the two complexes. Our studies highlight the importance of implementing a sulfur ligand into the equatorial ligand framework of nonheme iron(IV)-oxo complexes and how it affects the physicochemical properties of the oxidant and its reactivity.

Disparities in polysomnography referral in a high-risk cardiac population.

PURPOSE: Obstructive sleep apnea (OSA) is associated with metabolic, cardiovascular, and cerebrovascular comorbidities. Appropriate diagnosis and treatment of OSA might mitigate these comorbidities. This retrospective review sought to assess the impact of sex, age, race, ethnicity, and insurance status on polysomnography (PSG) referral rates. METHODS: An institutional STOP-Bang database of 299,320 patients was filtered for patients admitted to the hospital with an acute cardiac diagnosis between 2015-2020. A cohort of 4,735 patients were risk stratified by STOP-Bang (SB) score and correlations were made between PSG referrals and demographic and clinical variables (sex, age, race, ethnicity, and insurance status). RESULTS: Of the 25.3% of the cohort with high SB scores (5-8) only 21.3% were referred for PSG. Age and female sex were negatively associated with sleep study referrals (p < 0.001). No correlation was found between sleep study referral rates and race or ethnicity. No correlation was found between sleep study referrals and insurance provider. Admitting cardiac diagnosis significantly influenced sleep study referrals with diagnoses of arrhythmias and myocardial infarction being associated with an increased rate of PSG referrals compared to heart failure patients (p < 0.002). CONCLUSIONS: Our study found no significant correlation between PSG referral rates and race, ethnicity, or insurance provider. However, we found low overall rates of PSG referral, with negative correlations between older age and female sex and a high-risk cardiac population. This represents a substantial missed opportunity to identify patients at risk for OSA, obtain a diagnosis, and provider adequate treatment.

Therapeutic Potential of Nanocarrier Mediated Delivery of Peptides for Wound Healing: Current Status, Challenges and Future Prospective.

Wound healing presents a complex physiological process that involves a sequence of events orchestrated by various cellular and molecular mechanisms. In recent years, there has been growing interest in leveraging nanomaterials and peptides to enhance wound healing outcomes. Nanocarriers offer unique properties such as high surface area-to-volume ratio, tunable physicochemical characteristics, and the ability to deliver therapeutic agents in a controlled manner. Similarly, peptides, with their diverse biological activities and low immunogenicity, hold great promise as therapeutics in wound healing applications. In this review, authors explore the potential of peptides as bioactive components in wound healing formulations, focusing on their antimicrobial, anti-inflammatory, and pro-regenerative properties. Despite the significant progress made in this field, several challenges remain, including the need for standardized characterization methods, optimization of biocompatibility and safety profiles, and translation from bench to bedside. Furthermore, developing multifunctional nanomaterial-peptide hybrid systems represents promising avenues for future research. Overall, the integration of nanomaterials made up of natural or synthetic polymers with peptide-based formulations holds tremendous therapeutic potential in advancing the field of wound healing and improving clinical outcomes for patients with acute and chronic wounds.

Defluorination of Fluorophenols by a Nonheme Iron(IV)-Oxo Species: Observation of a New Intermediate Along the Reaction.

High-valent iron(IV)-oxo intermediates are versatile oxidants in the biotransformation of various substrates by metalloenzymes and catalyze essential reactions for human health as well as in the biodegradation of toxic organic pollutants in the environment. Herein, we report a biomimetic system that efficiently reacts with halophenols through defluorination reactions and characterize various short-lived intermediates along the reaction mechanism. We study the reactivity pattern of a nonheme iron(IV)-oxo species with a series of trihalophenols (X=F, Cl, Br). A combined experimental and computational study reveals that the oxidative dehalogenation of 2,4,6-trifluorophenol is initiated with an H-atom abstraction from the phenolic group by the iron(IV)-oxo species resulting in the formation of a phenolate radical and an iron(III)-hydroxo species. This iron(III)-hydroxo species forms an adduct with the oxidized substrate with λmax at 558 nm which subsequently decays to give quinones as products.

Biotransformation of Bisphenol by Human Cytochrome P450 2C9 Enzymes: A Density Functional Theory Study.

Bisphenol A (BPA, 2,2-bis-(4-hydroxyphenyl)propane) is used as a precursor in the synthesis of polycarbonate and epoxy plastics; however, its availability in the environment is causing toxicity as an endocrine-disrupting chemical. Metabolism of BPA and their analogues (substitutes) is generally performed by liver cytochrome P450 enzymes and often leads to a mixture of products, and some of those are toxic. To understand the product distributions of P450 activation of BPA, we have performed a computational study into the mechanisms and reactivities using large model structures of a human P450 isozyme (P450 2C9) with BPA bound. Density functional theory (DFT) calculations on mechanisms of BPA activation by a P450 compound I model were investigated, leading to a number of possible products. The substrate-binding pocket is tight, and as a consequence, aliphatic hydroxylation is not feasible as the methyl substituents of BPA cannot reach compound I well due to constraints of the substrate-binding pocket. Instead, we find low-energy pathways that are initiated with phenol hydrogen atom abstraction followed by OH rebound to the phenolic ortho- or para-position. The barriers of para-rebound are well lower in energy than those for ortho-rebound, and consequently, our P450 2C9 model predicts dominant hydroxycumyl alcohol products. The reactions proceed through two-state reactivity on competing doublet and quartet spin state surfaces. The calculations show fast and efficient substrate activation on a doublet spin state surface with a rate-determining electrophilic addition step, while the quartet spin state surface has multiple high-energy barriers that can also lead to various side products including C4-aromatic hydroxylation. This work shows that product formation is more feasible on the low spin state, while the physicochemical properties of the substrate govern barrier heights of the rate-determining step of the reaction. Finally, the importance of the second-coordination sphere is highlighted that determines the product distributions and guides the bifurcation pathways.

Quantum mechanical studies of p-azoxyanisole and identification of its electro-optic activity.

Liquid crystals (LCs) are used in displays, visors, navigation systems and many more. Amongst a wide range of LCs, p-azoxyanisole (PAA) is considered to be an active LC. Focusing on different properties of this molecule, in the reported study, the theoretical identification of quantum mechanical parameters and the identification of electro-optic properties are carried out. Different functional theories such as B3LYP, M06-2X and M06L are used along with three basis sets 6-31G**, 6-311G and 6-311G**. A comparative study revealed that the M06-2X method produces higher values of band gap, ionization potential, electronegativity and electronic global hardness while M06L produces lower values and B3LYP gives intermediate values. Nonlinear optical properties of liquid crystals are evaluated. The nonlinear optical properties obtained for a PAA liquid crystal are much higher than those of urea. Due to its high nonlinear optical properties, our liquid crystal can be used in the field of telecommunication and optical interconnection. The order parameter and birefringence are calculated with variable electric field. We found out that the order parameter and birefringence increase with a gradually increasing electric field, which suggests that the PAA liquid crystal can be used for developing electro-optic and tunable metamaterial devices.

Oxidative dehalogenation of halophenols by high-valent nonheme iron(IV)-oxo intermediates.

Mononuclear high-valent iron(IV)-oxo intermediates are excellent oxidants towards oxygenation reactions by heme and nonheme metalloenzymes and their model systems. One of the most important functions of these intermediates in nature is to detoxify various environmental pollutants. Organic substrates, such as halogenated phenols, are known to be water pollutants which can be degraded to their less hazardous forms through an oxidation reaction by iron(IV)-oxo complexes. Metalloproteins in nature utilize various types of second-coordination sphere interactions to anchor the substrate in the vicinity of the active site. This concept of substrate-binding is well-known for natural enzymes, but is elusive for the relevant biomimetic model systems. Herein, we report the oxidative reactivity patterns of an iron(IV)-oxo intermediate, [FeIV(O)(2PyN2Q)]2+, (2PyN2Q = 1,1-di(pyridin-2yl)-N,N-bis(quinolin-2-ylmethyl)methanamine) with a series of mono-, di- and tri-halophenols. A detailed experimental study shows that the dehalogenation reactions of the halophenols by such iron(IV)-oxo intermediates proceed via an initial hydrogen atom abstraction from the phenolic O-H group. Furthermore, based on the size and nucleophilicity of the halophenol, an intermediate substrate-bound species forms that is a phenolate adduct to the ferric species, which thereafter leads to the formation of the corresponding products.

Statin and aspirin as adjuvant therapy in hospitalised patients with SARS-CoV-2 infection: a randomised clinical trial (RESIST trial).

BACKGROUND: Statins and aspirin have been proposed for treatment of COVID-19 because of their anti-inflammatory and anti-thrombotic properties. Several observational studies have shown favourable results. There is a need for a randomised controlled trial. METHODS: In this single-center, open-label, randomised controlled trial, 900 RT-PCR positive COVID-19 patients requiring hospitalisation, were randomly assigned to receive either atorvastatin 40 mg (Group A, n = 224), aspirin 75 mg (Group B, n = 225), or both (Group C, n = 225) in addition to standard of care for 10 days or until discharge whichever was earlier or only standard of care (Group D, n = 226). The primary outcome variable was clinical deterioration to WHO Ordinal Scale for Clinical Improvement ≥ 6. The secondary outcome was change in serum C-reactive protein, interleukin-6, and troponin I. RESULTS: The primary outcome occurred in 25 (2.8%) patients: 7 (3.2%) in Group A, 3 (1.4%) in Group B, 8 (3.6%) in Group C, and 7 (3.2%) in Group D. There was no difference in primary outcome across the study groups (P = 0.463). Comparison of all patients who received atorvastatin or aspirin with the control group (Group D) also did not show any benefit [Atorvastatin: HR 1.0 (95% CI 0.41-2.46) P = 0.99; Aspirin: HR 0.7 (95% CI 0.27-1.81) P = 0.46]. The secondary outcomes revealed lower serum interleukin-6 levels among patients in Groups B and C. There was no excess of adverse events. CONCLUSIONS: Among patients admitted with mild to moderate COVID-19 infection, additional treatment with aspirin, atorvastatin, or a combination of the two does not prevent clinical deterioration. Trial Registry Number CTRI/2020/07/026791 ( http://ctri.nic.in ; registered on 25/07/2020).

Idiopathic brachial plexopathy after pacemaker implant.

A middle-aged woman presented with symptomatic complete heart block and underwent an uneventful dual chamber pacemaker implantation. Three weeks post procedure, she developed left arm pain and weakness, with neurological localization to the lower trunk of left brachial plexus. Possibilities of traumatic compression by the device/leads or postoperative idiopathic brachial plexopathy were considered. After ruling out traumatic causes, she was started on oral steroids, to which she responded remarkably. This case highlights the importance of recognizing this rare cause of brachial plexopathy following pacemaker implantation, because not only does an expedited diagnosis and medical treatment lead to prompt recovery with minimal neurological deficits, but it also circumvents an unnecessary surgical re-exploration.

Damage-Associated Molecular Patterns (DAMPs) in Retinal Disorders.

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules released from the extracellular and intracellular space of damaged tissue or dead cells. Recent evidence indicates that DAMPs are associated with the sterile inflammation caused by aging, increased ocular pressure, high glucose, oxidative stress, ischemia, mechanical trauma, stress, or environmental conditions, in retinal diseases. DAMPs activate the innate immune system, suggesting their role to be protective, but may promote pathological inflammation and angiogenesis in response to the chronic insult or injury. DAMPs are recognized by specialized innate immune receptors, such as receptors for advanced glycation end products (RAGE), toll-like receptors (TLRs) and the NOD-like receptor family (NLRs), and purine receptor 7 (P2X7), in systemic diseases. However, studies describing the role of DAMPs in retinal disorders are meager. Here, we extensively reviewed the role of DAMPs in retinal disorders, including endophthalmitis, uveitis, glaucoma, ocular cancer, ischemic retinopathies, diabetic retinopathy, age-related macular degeneration, rhegmatogenous retinal detachment, proliferative vitreoretinopathy, and inherited retinal disorders. Finally, we discussed DAMPs as biomarkers, therapeutic targets, and therapeutic agents for retinal disorders.

Ferromagnetic Coupling in Oxidovanadium(IV)-Porphyrin Radical Dimers.

Three different oxidovanadium(IV) porphyrin dimers with anti, cis, and trans arrangements of the two rings have been synthesized by changing the bridge between the porphyrin macrocycles. This provides a unique opportunity to investigate the role of the bridge and spatial arrangement between the two VIVO centers for their electronic communication and magnetic coupling. They were characterized by the combined application of XRD analysis, UV-vis and electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, magnetic susceptibility, and DFT calculations. One- and two-electron oxidations produce mono- and dication diradical species, respectively, which display an unusual ferromagnetic interaction between the unpaired spins of vanadium(IV) and porphyrin π-cation radical, in contrast to other metalloporphyrin dimers. The oxidized species show a dissimilar behavior between cis and trans isomers. The ferromagnetic coupling occurs between the porphyrin π-cation radical and the unpaired electron of the VIVO ion on the dxy orbital, orthogonal to the porphyrin-based molecular orbitals a1u and a2u.

Interplay between two spin states determines the hydroxylation catalyzed by P450 monooxygenase from Trichoderma brevicompactum.

Tri11 (now renamed as tri22) encoded cytochrome P450 monooxygenase in Trichoderma brevicompactum catalyzes the C-4 C-H hydroxylation of 12, 13-epoxytrichothec-9-ene (EPT) to produce trichodermol in the biosynthetic pathway of trichodermin/harzianum A. The density functional theory (DFT)-quantum mechanics (QM) approach is applied to elucidate the hydroxylation of EPT by using a model active species of P450 (Cpd I). The QM calculations were performed on the active site complex, to find out transition-state structure, intermediate, and product complexes for the two spin states at different potential energy surfaces. The two state reactivity rebound-free product formation resulted from the interplay of two spin states (doublet and quartet).

Interplay Between Steric and Electronic Effects: A Joint Spectroscopy and Computational Study of Nonheme Iron(IV)-Oxo Complexes.

Iron is an essential element in nonheme enzymes that plays a crucial role in many vital oxidative transformations and metabolic reactions in the human body. Many of those reactions are regio- and stereospecific and it is believed that the selectivity is guided by second-coordination sphere effects in the protein. Here, results are shown of a few engineered biomimetic ligand frameworks based on the N4Py (N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) scaffold and the second-coordination sphere effects are studied. For the first time, selective substitutions in the ligand framework have been shown to tune the catalytic properties of the iron(IV)-oxo complexes by regulating the steric and electronic factors. In particular, a better positioning of the oxidant and substrate in the rate-determining transition state lowers the reaction barriers. Therefore, an optimum balance between steric and electronic factors mediates the ideal positioning of oxidant and substrate in the rate-determining transition state that affects the reactivity of high-valent reaction intermediates.

Hydrogen by Deuterium Substitution in an Aldehyde Tunes the Regioselectivity by a Nonheme Manganese(III)-Peroxo Complex.

Mononuclear nonheme MnIII -peroxo complexes are important intermediates in biology, and take part in oxygen activation by photosystem II. Herein, we present work on two isomeric biomimetic side-on MnIII -peroxo intermediates with bispidine ligand system and reactivity patterns with aldehydes. The complexes are characterized with UV/Vis and mass spectrometric techniques and reaction rates with cyclohexane carboxaldehyde (CCA) are measured. The reaction gives an unusual regioselectivity switch from aliphatic to aldehyde hydrogen atom abstraction upon deuteration of the substrate, leading to the corresponding carboxylic acid product for the latter, while the former gives a deformylation reaction. Mechanistic details are established from kinetic isotope effect studies and density functional theory calculations. Thus, replacement of C-H by C-D raises the hydrogen atom abstraction barriers and enables a regioselectivity switch to a competitive pathway that is slightly higher in energy.

Diheme Cytochrome c: Structure-Function Correlation and Effect of Heme-Heme Interactions.

We explore here the structure-function relationship of the diheme cytochrome c using synthetic diheme analogs which serve as a convenient tool to investigate various aspects of Nature's sophisticated design in vitro. A large series of diiron ethane-bridged porphyrin dimers, both in the oxidized and the reduced states, are synthesized and their structural, chemical, and electrochemical properties have been scrutinized. Interestingly, the iron-to-iron nonbonding separation observed in such dihemes ranges from 9.49 to 10.06 Å which is very similar to the separation of 9.4 and 9.9 Å observed in the crystal structures of diheme cytochromes c isolated from Geobacter sulfurreducens and Haemophilus influenza, respectively. The FeIII/FeII redox couple in the diheme complex is shifted toward more positive than their monomeric analog. Present study unmasks the electronic structure and properties of diheme centers and also highlights the significance of their structural arrangement and axial ligand orientation, and heme-to-heme separation. The Atoms in Molecules (AIM) analysis suggests long-range attractive dispersion forces between the heme units for the observed structure and properties in dihemes.

Tunable transmission of a nematic liquid crystal as defect in a 1D periodic structure of dielectric materials by orientation and re-orientation of liquid crystal molecules.

In this paper, we investigate tunable transmission characteristics of a one-dimensional periodic structure (1DPS), designed with periodic dielectric materials containing a nematic liquid crystal (NLC) as a defect layer, on the basis of orientation and re-orientation of LC molecules. The nonlinear differential equation for the director of the liquid crystal under the light field is solved numerically. The relation between the liquid crystal director and the intensity of the electromagnetic wave (EMW) is derived. Transmittances of the liquid crystal defect layer in the 1DPS are calculated with the variation of the intensity of the incident wave and liquid crystal director tilt angles. By varying the director tilt angle of the liquid crystal molecules as well as the incident angle of the EMW, the shifting of the transmitted defect mode wavelengths is studied. Such study is helpful to understand how orientation and reorientation of the molecules affect the transmittance of the considered periodic structure when the EMW interacts with an embedded liquid crystal as a defect layer in the 1DPS of dielectric materials. Such photonic structure of dielectric materials with the liquid crystal layer as a defect layer can be used to fabricate bistable switches, optical filters, feedback lasers, etc.

Higher efficacy of pegylated interferon-α2b add-on therapy in hepatitis B envelope antigen-positive chronic hepatitis B patients on tenofovir monotherapy.

AIM: Monotherapy with pegylated interferon-α (Peg-IFNα) or the nucleos(t)ide analogs (NA) currently approved for treating chronic hepatitis B (CHB) has limited efficacy. Studies on the combination of Peg-IFNα/NA have shown conflicting results. We investigated whether sequentially adding on Peg-IFNα to tenofovir enhances serological response rates. METHODS: Treatment-naïve, hepatitis B envelope antigen (HBeAg)-positive CHB patients with moderately elevated alanine aminotransferase (ALT; 48-200 IU/mL) were started on tenofovir (300 mg/day) and enrolled at week 12 in a 1:1 ratio to either receive Peg-IFNα2b add-on (1.5 µg/kg/week) from week 12 to 36 (n = 53) or continue tenofovir monotherapy (n = 53). Both treatment arms received tenofovir consolidation therapy until week 72. The primary end-point was HBeAg loss at week 72. RESULTS: At week 72, the rate of HBeAg loss was higher in the Peg-IFNα2b add-on group (35.8%) compared to the tenofovir monotherapy group (17%) (P = 0.028; odds ratio, 2.73, 95% confidence interval, 1.09-6.79), and considerably higher in patients with a baseline hepatitis B virus (HBV)-DNA level >6 log IU/mL (32.6% vs 11.4%; P = 0.021). Rates of HBV-DNA loss (77.4% vs 71.7%; P = 0.51), ALT normalization (62.3% vs 52.8%; P = 0.32), and sustained virologic response (20.8% vs 11.3%; P = 0.18) at week 72 were comparable between the two groups. Significantly more patients in the add-on group had >3 log HBV-DNA reduction at week 36 (92.5% vs 66%; P = 0.001). Four patients treated with Peg-IFNα2b add-on achieved hepatitis B surface antigen (HBsAg) loss compared with one patient receiving tenofovir monotherapy. Decline of HBV-DNA of >2 log at week 4 led to higher HBeAg loss at week 72, independent of treatment arm. No patient had treatment-related adverse effects requiring treatment discontinuation. CONCLUSIONS: Twenty-four weeks of Peg-IFNα2b as an add-on sequential regimen to tenofovir is safe and resulted in greater loss of HBeAg and HBsAg compared to tenofovir monotherapy in selected HBeAg-positive patients. Viral load reduction followed by immune modulation is a potentially useful approach.

Keto-Enol Tautomerization Triggers an Electrophilic Aldehyde Deformylation Reaction by a Nonheme Manganese(III)-Peroxo Complex.

Oxygen atom transfer by high-valent enzymatic intermediates remains an enigma in chemical catalysis. In particular, manganese is an important first-row metal involved in key biochemical processes, including the biosynthesis of molecular oxygen (through the photosystem II complex) and biodegradation of toxic superoxide to hydrogen peroxide by superoxide dismutase. Biomimetic models of these biological systems have been developed to gain understanding on the structure and properties of short-lived intermediates but also with the aim to create environmentally benign oxidants. In this work, we report a combined spectroscopy, kinetics and computational study on aldehyde deformylation by two side-on manganese(III)-peroxo complexes with bispidine ligands. Both manganese(III)-peroxo complexes are characterized by UV-vis and mass spectrometry techniques, and their reactivity patterns with aldehydes was investigated. We find a novel mechanism for the reaction that is initiated by a hydrogen atom abstraction reaction, which enables a keto-enol tautomerization in the substrate. This is an essential step in the mechanism that makes an electrophilic attack on the olefin bond possible as the attack on the aldehyde carbonyl is too high in energy. Kinetics studies determine a large kinetic isotope effect for the replacement of the transferring hydrogen atom by deuterium, while replacing the transferring hydrogen atom by a methyl group makes the substrate inactive and hence confirm the hypothesized mechanism. Our new mechanism is confirmed with density functional theory modeling on the full mechanism and rationalized through valence bond and thermochemical cycles. Our unprecedented new mechanism may have relevance to biological and biomimetic chemistry processes in general and gives insight into the reactivity patterns of metal-peroxo and metal-hydroperoxo intermediates in general.

A Systematic Account on Aromatic Hydroxylation by a Cytochrome P450 Model Compound I: A Low-Pressure Mass Spectrometry and Computational Study.

Cytochrome P450 enzymes are heme-containing mono-oxygenases that mainly react through oxygen-atom transfer. Specific features of substrate and oxidant that determine the reaction rate constant for oxygen atom transfer are still poorly understood and therefore, we did a systematic gas-phase study on reactions by iron(IV)-oxo porphyrin cation radical structures with arenes. We present herein the first results obtained by using Fourier transform-ion cyclotron resonance mass spectrometry and provide rate constants and product distributions for the assayed reactions. Product distributions and kinetic isotope effect studies implicate a rate-determining aromatic hydroxylation reaction that correlates with the ionization energy of the substrate and no evidence of aliphatic hydroxylation products is observed. To further understand the details of the reaction mechanism, a computational study on a model complex was performed. These studies confirm the experimental hypothesis of dominant aromatic over aliphatic hydroxylation and show that the lack of an axial ligand affects the aliphatic pathways. Moreover, a two-parabola valence bond model is used to rationalize the rate constant and identify key properties of the oxidant and substrate that drive the reaction. In particular, the work shows that aromatic hydroxylation rates correlate with the ionization energy of the substrate as well as with the electron affinity of the oxidant.