Investigating the impact of the COVID-19 pandemic on recovery colleges: multi-site qualitative study.

BACKGROUND: During the COVID-19 pandemic, mental health problems increased as access to mental health services reduced. Recovery colleges are recovery-focused adult education initiatives delivered by people with professional and lived mental health expertise. Designed to be collaborative and inclusive, they were uniquely positioned to support people experiencing mental health problems during the pandemic. There is limited research exploring the lasting impacts of the pandemic on recovery college operation and delivery to students. AIMS: To ascertain how the COVID-19 pandemic changed recovery college operation in England. METHOD: We coproduced a qualitative interview study of recovery college managers across the UK. Academics and co-researchers with lived mental health experience collaborated on conducting interviews and analysing data, using a collaborative thematic framework analysis. RESULTS: Thirty-one managers participated. Five themes were identified: complex organisational relationships, changed ways of working, navigating the rapid transition to digital delivery, responding to isolation and changes to accessibility. Two key pandemic-related changes to recovery college operation were highlighted: their use as accessible services that relieve pressure on mental health services through hybrid face-to-face and digital course delivery, and the development of digitally delivered courses for individuals with mental health needs. CONCLUSIONS: The pandemic either led to or accelerated developments in recovery college operation, leading to a positioning of recovery colleges as a preventative service with wider accessibility to people with mental health problems, people under the care of forensic mental health services and mental healthcare staff. These benefits are strengthened by relationships with partner organisations and autonomy from statutory healthcare infrastructures.

Clinical effectiveness of active Alpha-Stim AID versus sham Alpha-Stim AID in major depression in primary care in England (Alpha-Stim-D): a multicentre, parallel group, double-blind, randomised controlled trial.

BACKGROUND: Randomised sham-controlled trials of cranial electrostimulation with the Alpha-Stim Anxiety Insomnia and Depression (AID) device have reported improved anxiety and depression symptoms; however, no adequately powered sham-controlled trials in major depression are available. We investigated whether active Alpha-Stim AID is superior to sham Alpha-Stim AID in terms of clinical effectiveness for depression symptoms in major depression. METHODS: The Alpha-Stim-D trial was a multicentre, parallel group, double-blind, randomised controlled trial, recruiting participants from 25 primary care centres in two regions in England, UK. Eligible participants were aged 16 years or older with a current diagnosis of primary major depression, a score of 10-19 on the nine-item Patient Health Questionnaire, and had been offered or prescribed and reported taking antidepressant medication for at least 6 weeks in the previous 3 months. Main exclusion criteria were contraindications to Alpha-Stim AID device use, having persistent suicidal ideation or self-harm, neurological conditions, a substance use disorder or dependence, an eating disorder, bipolar disorder, or non-affective psychosis, or receiving psychological treatment in the past 3 months. Eligible participants were randomly assigned (1:1, minimised by region, anxiety disorder, and antidepressant use) to 1 h daily use of active (100 µA) or sham Alpha-Stim AID treatment for 8 weeks. Randomisation was via an independent web-based system, with participants, outcome assessors, and data analyst masked to treatment assignment. The primary outcome was change from baseline in score on the 17-item Hamilton Depression Rating Scale (HDRS-17, GRID version) at 16 weeks after randomisation, with participants analysed by intention to treat (ITT; all randomly assigned participants). Safety was assessed in all randomly assigned participants. The trial is registered with the ISRCTN registry (ISRCTN11853110); status completed. FINDINGS: Between Sept 8, 2020, and Jan 14, 2022, 236 eligible participants were randomly assigned to active or sham Alpha-Stim AID (n=118 each). 156 (66%) participants were women, 77 (33%) were men, and three (1%) self-reported as other gender; 200 (85%) were White British or Irish; and the mean age was 38·0 years (SD 15·3; range 16-83). 102 (86%) participants in the active Alpha-Stim AID group and 98 (83%) in the sham group were followed up 16 weeks after randomisation. In the ITT population, mean change in GRID-HDRS-17 at 16 weeks was -5·9 (95% CI -7·1 to -4·8) in the active Alpha-Stim AID group and -6·5 (-7·7 to -5·4) in the sham group (mean change difference -0·6 [95% CI -1·0 to 2·2], p=0·46). Among the 236 participants, 17 adverse events were reported in 17 (7%) participants (nine [8%] participants in the active Alpha-Stim AID group; and eight [7%] participants in the sham group). One serious adverse event of suicidal ideation leading to hospitalisation was reported in the sham group, which was judged to be unrelated to the device. INTERPRETATION: Active Alpha-Stim AID was safe and acceptable, but no more clinically effective than sham Alpha-Stim AID in major depression. FUNDING: National Institute for Health Research Applied Research Collaboration East Midlands and Electromedical Products International.

Recovery Colleges Characterisation and Testing in England (RECOLLECT): rationale and protocol.

BACKGROUND: Recovery Colleges are a relatively recent initiative within mental health services. The first opened in 2009 in London and since then numbers have grown. They are based on principles of personal recovery in mental health, co-production between people with lived experience of mental health problems and professionals, and adult learning. Student eligibility criteria vary, but all serve people who use mental health services, with empirical evidence of benefit. Previously we developed a Recovery College fidelity measure and a preliminary change model identifying the mechanisms of action and outcomes for this group, which we refer to as service user students. The Recovery Colleges Characterisation and Testing (RECOLLECT) study is a five-year (2020-2025) programme of research in England. The aim of RECOLLECT is to determine Recovery Colleges' effectiveness and cost-effectiveness, and identify organisational influences on fidelity and improvements in mental health outcomes.  METHODS: RECOLLECT comprises i) a national survey of Recovery Colleges, ii) a prospective cohort study to establish the relationship between fidelity, mechanisms of action and psychosocial outcomes, iii) a prospective cohort study to investigate effectiveness and cost-effectiveness, iv) a retrospective cohort study to determine the relationship between Recovery College use and outcomes and mental health service use, and v) organisational case studies to establish the contextual and organisational factors influencing fidelity and outcomes. The programme has been developed with input from individuals who have lived experience of mental health problems. A Lived Experience Advisory Panel will provide input into all stages of the research. DISCUSSION: RECOLLECT will provide the first rigorous evidence on the effectiveness and cost effectiveness of Recovery Colleges in England, to inform their prioritising, commissioning, and running. The validated RECOLLECT multilevel change model will confirm the active components of Recovery Colleges. The fidelity measure and evidence about the fidelity-outcome relationship will provide an empirically-based approach to develop Recovery Colleges, to maximise benefits for students. Findings will be disseminated through the study website (researchintorecovery.com/recollect) and via national and international Recovery College networks to maximise impact, and will shape policy on how Recovery Colleges can help those with mental health problems lead empowered, meaningful and fulfilling lives.

A randomised controlled trial investigating the clinical and cost-effectiveness of Alpha-Stim AID cranial electrotherapy stimulation (CES) in patients seeking treatment for moderate severity depression in primary care (Alpha-Stim-D Trial).

BACKGROUND: Major depression is the second leading cause of years lost to disability worldwide and is a leading contributor to suicide. However, first-line antidepressants are only fully effective for 33%, and only 40% of those offered psychological treatment attend for two sessions or more. Views gained from patients and primary care professionals are that greater treatment uptake might be achieved if people with depression could be offered alternative and more accessible treatment options. Although there is evidence that the Alpha-Stim Anxiety Insomnia and Depression (AID) device is safe and effective for anxiety and depression symptoms in people with anxiety disorders, there is much less evidence of efficacy in major depression without anxiety. This study investigates the effectiveness of the Alpha-Stim AID device, a cranial electrotherapy stimulation (CES) treatment that people can safely use independently at home. The device provides CES which has been shown to increase alpha oscillatory brain activity, associated with relaxation. METHODS: The aim of this study is to investigate the clinical and cost-effectiveness of Alpha-Stim AID in treatment-seeking patients (aged 16 years upwards) with moderate to moderately severe depressive symptoms in primary care. The study is a multi-centre parallel-group, double-blind, non-commercial, randomised controlled superiority trial. The primary objective of the study is to examine the clinical efficacy of active daily use of 8 weeks of Alpha-Stim AID versus sham Alpha-Stim AID on depression symptoms at 16 weeks (8 weeks after the end of treatment) in people with moderate severity depression. The primary outcome is the 17-item Hamilton Depression Rating Scale at 16 weeks. All trial and treatment procedures are carried out remotely using videoconferencing, telephone and postal delivery considering the COVID-19 pandemic restrictions. DISCUSSION: This study is investigating whether participants using the Alpha-Stim AID device display a reduction in depressive symptoms that can be maintained over 8 weeks post-treatment. The findings will help to determine whether Alpha-Stim AID should be recommended, including being made available in the NHS for patients with depressive symptoms. TRIAL REGISTRATION: ISRTCN ISRCTN11853110 . Registered on 14 August 2020.

'He's my mate you see': a critical discourse analysis of the therapeutic role of companion animals in the social networks of people with a diagnosis of severe mental illness.

There is increasing recognition of the role pets play in the management of mental health conditions. Evidence suggests that pets promote social interaction and provide secure and intimate relationships which support the management of symptoms. This paper aimed to extend this evidence by exploring the phenomenological understanding of relationships and relationality with companion animals as therapeutic agents in the context of people's wider social networks.A qualitative study was undertaken incorporating 35 interviews with 12 participants with a diagnosis of severe mental illness who identified a pet as being important in the management of mental health. Participants took part in three in-depth interviews centred on ego network mapping over a 12-month period (baseline, 6 and 12 months). A critical discourse analysis examined therapeutic relationships with pets in relation to mental health and compared these to other types of support over time. Summative discourse analyses were combined with a cross-case thematic analysis to look for commonalities and differences across individuals.Compared with interactions with other therapeutic agents, relationships with pets were free from the obligations and complexities associated with other types of network members and provided an extension and reinforcement to an individual's sense of self which militated against the negative experiences associated with mental illness. Relationships with human network members were more variable in terms of consistency and capacity to manage demands (eg, network members requiring support themselves) and the emotions of others associated with fluctuations in mental health.This study adds weight to research supporting the inclusion of companion animals in the lexicon of mental health self-management through the therapeutic value attributed to them by participants within a wide personal network of support. The findings point to how consideration might usefully be given to how relationships with companion animals can be incorporated into healthcare planning and delivery.

Monoclonal Cell Line Generation and CRISPR/Cas9 Manipulation via Single-Cell Electroporation.

Stably transfected cell lines are widely used in drug discovery and biological research to produce recombinant proteins. Generation of these cell lines requires the isolation of multiple clones, using time-consuming dilution methods, to evaluate the expression levels of the gene of interest. A new and efficient method is described for the generation of monoclonal cell lines, without the need for dilution cloning. In this new method, arrays of patterned cell colonies and single cell transfection are employed to deliver a plasmid coding for a reporter gene and conferring resistance to an antibiotic. Using a nanofountain probe electroporation system, probe positioning is achieved through a micromanipulator with sub-micron resolution and resistance-based feedback control. The array of patterned cell colonies allows for rapid selection of numerous stably transfected clonal cell lines located on the same culture well, conferring a significant advantage over slower and labor-intensive traditional methods. In addition to plasmid integration, this methodology can be seamlessly combined with CRISPR/Cas9 gene editing, paving the way for advanced cell engineering.

Micro- and Nanoscale Technologies for Delivery into Adherent Cells.

Several recent micro- and nanotechnologies have provided novel methods for biological studies of adherent cells because the small features of these new biotools provide unique capabilities for accessing cells without the need for suspension or lysis. These novel approaches have enabled gentle but effective delivery of molecules into specific adhered target cells, with unprecedented spatial resolution. We review here recent progress in the development of these technologies with an emphasis on in vitro delivery into adherent cells utilizing mechanical penetration or electroporation. We discuss the major advantages and limitations of these approaches and propose possible strategies for improvements. Finally, we discuss the impact of these technologies on biological research concerning cell-specific temporal studies, for example non-destructive sampling and analysis of intracellular molecules.

Isolating single cells in a neurosphere assay using inertial microfluidics.

Sphere forming assays are routinely used for in vitro propagation and differentiation of stem cells. Because the stem cell clusters can become heterogeneous and polyclonal, they must first be dissociated into a single cell suspension for further clonal analysis or differentiation studies. The dissociated population is marred by the presence of doublets, triplets and semi-cleaved/intact clusters which makes identification and further analysis of differentiation pathways difficult. In this work, we use inertial microfluidics to separate the single cells and clusters in a population of chemically dissociated neurospheres. In contrast to previous microfluidic sorting technologies which operated at high flow rates, we implement the spiral microfluidic channel in a novel focusing regime that occurs at lower flow rates. In this regime, the curvature-induced Dean's force focuses the smaller, single cells towards the inner wall and the larger clusters towards the center. We further demonstrate that sorting in this low flow rate (and hence low shear stress) regime yields a high percentage (>90%) of viable cells and preserves multipotency by differentiating the sorted neural stem cell population into neurons and astrocytes. The modularity of the device allows easy integration with other lab-on-a-chip devices for upstream mechanical dissociation and downstream high-throughput clonal analysis, localized electroporation and sampling. Although demonstrated in the case of the neurosphere assay, the method is equally applicable to other sphere forming assays.

Single-cell detection of mRNA expression using nanofountain-probe electroporated molecular beacons.

New techniques for single-cell analysis enable new discoveries in gene expression and systems biology. Time-dependent measurements on individual cells are necessary, yet the common single-cell analysis techniques used today require lysing the cell, suspending the cell, or long incubation times for transfection, thereby interfering with the ability to track an individual cell over time. Here a method for detecting mRNA expression in live single cells using molecular beacons that are transfected into single cells by means of nanofountain probe electroporation (NFP-E) is presented. Molecular beacons are oligonucleotides that emit fluorescence upon binding to an mRNA target, rendering them useful for spatial and temporal studies of live cells. The NFP-E is used to transfect a DNA-based beacon that detects glyceraldehyde 3-phosphate dehydrogenase and an RNA-based beacon that detects a sequence cloned in the green fluorescence protein mRNA. It is shown that imaging analysis of transfection and mRNA detection can be performed within seconds after electroporation and without disturbing adhered cells. In addition, it is shown that time-dependent detection of mRNA expression is feasible by transfecting the same single cell at different time points. This technique will be particularly useful for studies of cell differentiation, where several measurements of mRNA expression are required over time.

Microfluidic device for stem cell differentiation and localized electroporation of postmitotic neurons.

New techniques to deliver nucleic acids and other molecules for gene editing and gene expression profiling, which can be performed with minimal perturbation to cell growth or differentiation, are essential for advancing biological research. Studying cells in their natural state, with temporal control, is particularly important for primary cells that are derived by differentiation from stem cells and are adherent, e.g., neurons. Existing high-throughput transfection methods either require cells to be in suspension or are highly toxic and limited to a single transfection per experiment. Here we present a microfluidic device that couples on-chip culture of adherent cells and transfection by localized electroporation. Integrated microchannels allow long-term cell culture on the device and repeated temporal transfection. The microfluidic device was validated by first performing electroporation of HeLa and HT1080 cells, with transfection efficiencies of ~95% for propidium iodide and up to 50% for plasmids. Application to primary cells was demonstrated by on-chip differentiation of neural stem cells and transfection of postmitotic neurons with a green fluorescent protein plasmid.

Microfluidic parallel patterning and cellular delivery of molecules with a nanofountain probe.

This brief report describes a novel tool for microfluidic patterning of biomolecules and delivery of molecules into cells. The microdevice is based on integration of nanofountain probe (NFP) chips with packaging that creates a closed system and enables operation in liquid. The packaged NFP can be easily coupled to a micro/nano manipulator or atomic force microscope for precise position and force control. We demonstrate here the functionality of the device for continuous direct-write parallel patterning on a surface in air and in liquid. Because of the small volume of the probes (~3 pL), we can achieve flow rates as low as 1 fL/s and have dispensed liquid drops with submicron to 10 µm diameters in a liquid environment. Furthermore, we demonstrate that this microdevice can be used for delivery of molecules into single cells by transient permeabilization of the cell membrane (i.e., electroporation). The significant advantage of NFP-based electroporation compared with bulk electroporation and other transfection techniques is that it allows for precise and targeted delivery while minimizing stress to the cell. We discuss the ongoing development of the tool toward automated operation and its potential as a multifunctional device for microarray applications and time-dependent single-cell studies.

Nanofountain probe electroporation (NFP-E) of single cells.

The ability to precisely deliver molecules into single cells is of great interest to biotechnology researchers for advancing applications in therapeutics, diagnostics, and drug delivery toward the promise of personalized medicine. The use of bulk electroporation techniques for cell transfection has increased significantly in the past decade, but the technique is nonspecific and requires high voltage, resulting in variable efficiency and low cell viability. We have developed a new tool for electroporation using nanofountain probe (NFP) technology, which can deliver molecules into cells in a manner that is highly efficient and gentler to cells than bulk electroporation or microinjection. Here we demonstrate NFP electroporation (NFP-E) of single HeLa cells within a population by transfecting them with fluorescently labeled dextran and imaging the cells to evaluate the transfection efficiency and cell viability. Our theoretical analysis of the mechanism of NFP-E reveals that application of the voltage creates a localized electric field between the NFP cantilever tip and the region of the cell membrane in contact with the tip. Therefore, NFP-E can deliver molecules to a target cell with minimal effect of the electric potential on the cell. Our experiments on HeLa cells confirm that NFP-E offers single cell selectivity, high transfection efficiency (>95%), qualitative dosage control, and very high viability (92%) of transfected cells.

Protonation of the dinitrogen-reduction catalyst [HIPTN3N]Mo(III) investigated by ENDOR spectroscopy.

Dinitrogen is reduced to ammonia by the molybdenum complex of L = [HIPTN3N](3-) [Mo; HIPT = 3,5-(2,4,6-iPr3C6H2)2C6H3]. The mechanism by which this occurs involves the stepwise addition of proton/electron pairs, but how the first pair converts MoN2 to MoN ═ NH remains uncertain. The first proton of reduction might bind either at Nß of N2 or at one of the three amido nitrogen (N(am)) ligands. Treatment of MoCO with [2,4,6-Me3C5H3N]BAr'4 [Ar' = 2,3-(CF3)2C6H3] in the absence of reductant generates HMoCO(+), whose electron paramagnetic resonance spectrum has greatly reduced g anisotropy relative to MoCO. (2)H Mims pulsed electron nuclear double-resonance spectroscopy of (2)HMoCO(+) shows a signal that simulations show to have a hyperfine tensor with an isotropic coupling, aiso((2)H) = -0.22 MHz, and a roughly dipolar anisotropic interaction, T((2)H) = [-0.48, -0.93, 1.42] MHz. The simulations show that the deuteron is bound to N(am), near the Mo equatorial plane, not along the normal, and at a distance of 2.6 Å from Mo, which is nearly identical with the (Nam)(2)H(+)-Mo distance predicted by density functional theory computations.

The structure of formaldehyde-inhibited xanthine oxidase determined by 35 GHz 2H ENDOR spectroscopy.

The formaldehyde-inhibited Mo(V) state of xanthine oxidase (I) has been studied for four decades, yet it has not proven possible to distinguish unequivocally among the several structures proposed for this form. The uniquely large isotropic hyperfine coupling for (13)C from CH(2)O led to the intriguing suggestion of a direct Mo-C bond for the active site of I. This suggestion was supported by the recent crystal structures of glycol- and glycerol-inhibited forms of aldehyde oxidoreductase, a member of the xanthine oxidase family. (1)H and (2)H ENDOR spectra of I(C(1,2)H(2)O) in H(2)O/D(2)O buffer now have unambiguously revealed that the active-site structure of I contains a CH(2)O adduct of Mo(V) in the form of a four-membered ring with S and O linking the C to Mo and have ruled out a direct Mo-C bond. Density functional theory computations are consistent with this conclusion. We interpret the large (13)C coupling as resulting from a "transannular hyperfine interaction".

Probing in vivo Mn2+ speciation and oxidative stress resistance in yeast cells with electron-nuclear double resonance spectroscopy.

Manganese is an essential transition metal that, among other functions, can act independently of proteins to either defend against or promote oxidative stress and disease. The majority of cellular manganese exists as low molecular-weight Mn(2+) complexes, and the balance between opposing "essential" and "toxic" roles is thought to be governed by the nature of the ligands coordinating Mn(2+). Until now, it has been impossible to determine manganese speciation within intact, viable cells, but we here report that this speciation can be probed through measurements of (1)H and (31)P electron-nuclear double resonance (ENDOR) signal intensities for intracellular Mn(2+). Application of this approach to yeast (Saccharomyces cerevisiae) cells, and two pairs of yeast mutants genetically engineered to enhance or suppress the accumulation of manganese or phosphates, supports an in vivo role for the orthophosphate complex of Mn(2+) in resistance to oxidative stress, thereby corroborating in vitro studies that demonstrated superoxide dismutase activity for this species.

Experimental and theoretical EPR study of Jahn-Teller-active [HIPTN(3)N]MoL complexes (L = N(2), CO, NH(3)).

The trigonally symmetric Mo(III) coordination compounds [HIPTN(3)N]MoL (L = N(2), CO, NH(3); [HIPTN(3)N]Mo = [(3,5-(2,4,6-i-Pr(3)C(6)H(2))(2)C(6)H(3)NCH(2)CH(2))(3)N]Mo) are low-spin d(3) (S = (1)/(2)) species that exhibit a doubly degenerate (2)E ground state susceptible to a Jahn-Teller (JT) distortion. The EPR spectra of all three complexes and their temperature and solvent dependences are interpreted within a formal "two-orbital" model that reflects the ground-state configuration, describes the vibronic interactions that lead to the JT distortions, and addresses whether these complexes exhibit static or dynamic JT distortions. The electronic and vibronic properties of these complexes are then analyzed through ab initio quantum chemical computations. It is not possible to interpret the spectroscopic properties of the orbitally degenerate [HIPTN(3)N]MoL with DFT methods, so we have resorted to multi-reference wavefunction approaches, the entry level of which is the complete active space self-consistent field (CASSCF) method. Overall, the experimental and computational studies provide new insights into the role of trigonal coordination, as enforced by the [HIPTN(3)N](3-) ligand, in activating the Mo ion for the binding and reduction of N(2).

Spectroscopic and electronic structure studies of symmetrized models for reduced members of the dimethylsulfoxide reductase enzyme family.

Enzymes belonging to the dimethylsulfoxide reductase (DMSOR) family of pyranopterin Mo enzymes have a unique active-site geometry in the reduced form that lacks a terminal oxo ligand, unlike the reduced active sites of other pyranopterin Mo enzymes. Furthermore, the DMSOR family is characterized by the coordination of two pyranopterin-ene-1,2-dithiolate ligands in their active sites, which is distinctive among the other pyranopterin Mo enzymes but analogous to all of the currently known tungsten-containing enzymes. Electronic absorption, resonance Raman, and ground- and excited-state density functional calculations of symmetrized analogues of the reduced DMSOR active site ([NEt4][Mo(IV)(QAd)(S2C2Me2)2] where Ad = 2-adamantyl; Q = O, S, Se) have allowed for a detailed description of Mo-bisdithiolene electronic structure in the absence of a strong-field oxo ligand. The electronic absorption spectra are dominated by dithiolene S --> Mo charge-transfer transitions, and the totally symmetric Mo-S Raman stretch is observed at approximately 400 cm(-1) for all three complexes. These data indicate that the Mo-bisdithiolene bonding scheme in high-symmetry [Mo(QAd)(S2C2Me2)2]- complexes is not strongly perturbed by the apical QAd- ligands, but instead, the dithiolene ligands define the t(2g) ligand field splitting. The effects of conserved geometric distortions observed in DMSOR, relative to these high-symmetry models, were explored by spectroscopically calibrated bonding calculations, and the results are discussed within the context of electronic structure contributions to ground-state destabilization and transition-state stabilization. The specific electronic structure tuning of the endogenous amino acid ligation on the mechanism of DMSOR is also discussed.

ENDOR characterization of a synthetic diiron hydrazido complex as a model for nitrogenase intermediates.

Molybdenum-dependent nitrogenase binds and reduces N2 at the [Fe7, Mo, S9, X, homocitrate] iron-molybdenum cofactor (FeMo-co). Kinetic and spectroscopic studies of nitrogenase variants indicate that a single Fe-S face is the most likely binding site. Recently, substantial progress has been made in determining the structures of nitrogenase intermediates formed during alkyne and N2 reduction through use of ENDOR spectroscopy. However, constraints derived from ENDOR studies of biomimetic complexes with known structure would powerfully contribute in turning experimentally derived ENDOR parameters into structures for species bound to FeMo-co during N2 reduction. The first report of a paramagnetic Fe-S compound that binds reduced forms of N2 involved Fe complexes stabilized by a bulky beta-diketiminate ligand (Vela, J.; Stoian, S.; Flaschenriem, C. J.; Münck, E.; Holland, P. L. J. Am. Chem. Soc. 2004, 126, 4522-4523). Treatment of a sulfidodiiron(II) complex with phenylhydrazine gave an isolable mixed-valence FeII-Fe(III) complex with a bridging phenylhydrazido (PhNNH2) ligand, and this species now has been characterized by ENDOR spectroscopy. Using both 15N, 2H labeled and unlabeled forms of the hydrazido ligand, the hyperfine and quadrupole parameters of the -N-NH2 moiety have been derived by a procedure that incorporates the (near-) mirror symmetry of the complex and involves a strategy which combines experiment with semiempirical and DFT computations. The results support the use of DFT computations in identifying nitrogenous species bound to FeMo-co of nitrogenase turnover intermediates and indicate that 14N quadrupole parameters from nitrogenase intermediates will provide a strong indication of the nature of the bound nitrogenous species. Comparison of the large 14N hyperfine couplings measured here with that of a hydrazine-derived species bound to FeMo-co of a trapped nitrogenase intermediate suggests that the ion(s) are not high spin and/or that the spin coupling coefficients of the coordinating cofactor iron ion(s) in the intermediate are exceptionally small.

Comparing the electronic properties of the low-spin cyano-ferric [Fe(N4)(Cys)] active sites of superoxide reductase and p450cam using ENDOR spectroscopy and DFT calculations.

Superoxide reductase (SOR) and P450 enzymes contain similar [Fe(N)4(SCys)] active sites and, although they catalyze very different reactions, are proposed to involve analogous low-spin (hydro)peroxo-Fe(III) intermediates in their respective mechanisms that can be modeled by cyanide binding. The equatorial FeN4 ligation by four histidine ligands in CN-SOR and the heme in CN-P450cam is directly compared by 14N ENDOR, while the axial Fe-CN and Fe-S bonding is probed by 13C ENDOR of the cyanide ligand and 1Hbeta ENDOR measurements to determine the spin density delocalization onto the cysteine sulfur. There are small, but notable, differences in the bonding between Fe(III) and its ligands in the two enzymes. The ENDOR measurements are complemented by DFT computations that support the semiempirical equation used to compute spin densities on metal-coordinated cysteinyl and shed light on bonding changes as the Fe-C-N linkage bends. They further indicate that H bonds to the cysteinyl thiolate sulfur ligand reduce the spin density on the sulfur in both active sites to a degree that exceeds the difference induced by the alternative sets of "in-plane" nitrogen ligands.