Revisiting the Preparation and Catalytic Performance of a Phosphine-Modified Co(II) Hydroformylation Precatalyst.

In light of recent conflicting reports regarding the hydroformylation catalytic activity derived from cationic Co(II) precatalysts of the form [Co(acac)(bis(phosphine))]BF4, the synthetic procedures and characterization of [Co(acac)(dppBz)]BF4, 1, are evaluated. Leveraging calibrated ESI-TOF MS methodologies, substantial quantities of Co(acac)2(dppBz), 2, were observed within samples of 1. The source of the impurity, 2, is determined to derive from incomplete protonolysis of the Co(acac)2 precursor and ligand scrambling occurring during the synthesis of 1. Revised synthetic procedures using lower temperature conditions and longer reaction times afford analytically pure samples of 1 based on ESI-TOF MS and NMR spectroscopic analysis. Complex 1 is demonstrated to act as a hydroformylation precatalyst for the conversion of 1-hexene to 1-heptanal under relatively mild conditions at 51.7 bar and 140 °C. The presence of impurity 2 is shown to dramatically decrease the catalytic performance derived from 1.

Leveraging machine learning to develop a postoperative predictive model for postoperative urinary retention following lumbar spine surgery.

Introduction: Postoperative urinary retention (POUR) is the inability to urinate after a surgical procedure despite having a full bladder. It is a common complication following lumbar spine surgery which has been extensively linked to increased patient morbidity and hospital costs. This study hopes to development and validate a predictive model for POUR following lumbar spine surgery using patient demographics, surgical and anesthesia variables. Methods: This is a retrospective observational cohort study of 903 patients who underwent lumbar spine surgery over the period of June 2017 to June 2019 in a tertiary academic medical center. Four hundred and nineteen variables were collected including patient demographics, ICD-10 codes, and intraoperative factors. Least absolute shrinkage and selection operation (LASSO) regression and logistic regression models were compared. A decision tree model was fitted to the optimal model to classify each patient's risk of developing POUR as high, intermediate, or low risk. Predictive performance of POUR was assessed by area under the receiver operating characteristic curve (AUC-ROC). Results: 903 patients were included with average age 60 ± 15 years, body mass index of 30.5 ± 6.4 kg/m2, 476 (53%) male, 785 (87%) white, 446 (49%) involving fusions, with average 2.1 ± 2.0 levels. The incidence of POUR was 235 (26%) with 63 (7%) requiring indwelling catheter placement. A decision tree was constructed with an accuracy of 87.8%. Conclusion: We present a highly accurate and easy to implement decision tree model which predicts POUR following lumbar spine surgery using preoperative and intraoperative variables.

Development of a Real-Time Dashboard for Overdose Touchpoints: User-Centered Design Approach.

BACKGROUND: Overdose Fatality Review (OFR) is an important public health tool for shaping overdose prevention strategies in communities. However, OFR teams review only a few cases at a time, which typically represent a small fraction of the total fatalities in their jurisdiction. Such limited review could result in a partial understanding of local overdose patterns, leading to policy recommendations that do not fully address the broader community needs. OBJECTIVE: This study explored the potential to enhance conventional OFRs with a data dashboard, incorporating visualizations of touchpoints-events that precede overdoses-to highlight prevention opportunities. METHODS: We conducted 2 focus groups and a survey of OFR experts to characterize their information needs and design a real-time dashboard that tracks and measures decedents' past interactions with services in Indiana. Experts (N=27) were engaged, yielding insights on essential data features to incorporate and providing feedback to guide the development of visualizations. RESULTS: The findings highlighted the importance of showing decedents' interactions with health services (emergency medical services) and the justice system (incarcerations). Emphasis was also placed on maintaining decedent anonymity, particularly in small communities, and the need for training OFR members in data interpretation. The developed dashboard summarizes key touchpoint metrics, including prevalence, interaction frequency, and time intervals between touchpoints and overdoses, with data viewable at the county and state levels. In an initial evaluation, the dashboard was well received for its comprehensive data coverage and its potential for enhancing OFR recommendations and case selection. CONCLUSIONS: The Indiana touchpoints dashboard is the first to display real-time visualizations that link administrative and overdose mortality data across the state. This resource equips local health officials and OFRs with timely, quantitative, and spatiotemporal insights into overdose risk factors in their communities, facilitating data-driven interventions and policy changes. However, fully integrating the dashboard into OFR practices will likely require training teams in data interpretation and decision-making.

The respiratory system influences flight mechanics in soaring birds.

The subpectoral diverticulum (SPD) is an extension of the respiratory system in birds that is located between the primary muscles responsible for flapping the wing1,2. Here we survey the pulmonary apparatus in 68 avian species, and show that the SPD was present in virtually all of the soaring taxa investigated but absent in non-soarers. We find that this structure evolved independently with soaring flight at least seven times, which indicates that the diverticulum might have a functional and adaptive relationship with this flight style. Using the soaring hawks Buteo jamaicensis and Buteo swainsoni as models, we show that the SPD is not integral for ventilation, that an inflated SPD can increase the moment arm of cranial parts of the pectoralis, and that pectoralis muscle fascicles are significantly shorter in soaring hawks than in non-soaring birds. This coupling of an SPD-mediated increase in pectoralis leverage with force-specialized muscle architecture produces a pneumatic system that is adapted for the isometric contractile conditions expected in soaring flight. The discovery of a mechanical role for the respiratory system in avian locomotion underscores the functional complexity and heterogeneity of this organ system, and suggests that pulmonary diverticula are likely to have other undiscovered secondary functions. These data provide a mechanistic explanation for the repeated appearance of the SPD in soaring lineages and show that the respiratory system can be co-opted to provide biomechanical solutions to the challenges of flight and thereby influence the evolution of avian volancy.

How Social Connectedness Helps Patients Stay Home After Hospital at Home Enrollment: A Mixed Methods Study.

BACKGROUND: While enrolled in Hospital at Home (HaH) programs, patients rely on their social network to provide supportive behaviors that are routinely provided by hospital staff in the inpatient setting. OBJECTIVE: This study investigated how social connectedness is associated with patient outcomes in a HaH program. DESIGN: The explanatory iterative sequential mixed methods design included an electronic health record review to collect quantitative measures to describe the severity of patient illness and healthcare utilization and then qualitative interviews to explain quantitative findings. PARTICIPANTS: The quantitative phase included 100 patients (18 years or older) admitted to the hospital who were subsequently enrolled in the HaH program. In the qualitative phase, 33 of the 100 patients participated in semi-structured interviews. ANALYSIS: Qualitative data was analyzed using the Sort & Sift, Think & Shift method. Integrated analysis included merged data displays of healthcare utilization data and patient descriptions of their care and genogram-type illustrations to enable variable-oriented analysis of structural support. We then examined patient narratives by two variables: life course and care elevation, to understand differences in the trajectories of six subsets of patients as identified by the quantitative data. KEY RESULTS: Three factors prompted patients to enroll in HaH: low attention from hospital staff during hospital stay; loneliness and isolation during hospital stay; and family encouragement to enroll. After discharge, social support within the home structure facilitated recovery during HaH. Conversely, HaH patients with limited support within the home were more likely to be readmitted. CONCLUSIONS: Structural social connectedness facilitates patient recovery in HaH. Before enrolling patients in HaH, clinicians should take an in-depth social history, including questions about social/familial roles, household responsibilities, and technology acceptance. Clinicians should engage formal and informal caregivers in these conversations early and communicate a clear picture of what caregivers should do to support the patient through recovery.

Evaluating the Ability of Brachial Plexus-Injured Patients to Control an Externally Powered (Myoelectric) Hand Prosthesis.

BACKGROUND: Restoration of hand function after traumatic brachial plexus injury (BPI) remains a formidable challenge. Traditional methods such as nerve or free muscle transfers yield suboptimal results. Advancements in myoelectric prostheses, characterized by novel signal acquisition and improved material technology, show promise in restoring functional grasp. This study evaluated the ability of adults with a BPI injury to control an externally powered prosthetic hand using nonintuitive signals, simulating the restoration of grasp with a myoelectric prosthesis. It also assessed the effectiveness of a comprehensive multidisciplinary evaluation in guiding treatment decisions. METHODS: A multidisciplinary brachial plexus team assessed adults with compromised hand function due to BPI. The feasibility of amputation coupled with fitting of a myoelectric prosthesis for grasp reconstruction was evaluated. Participants' ability to control a virtual or model prosthetic hand using surface electromyography (EMG) as well as with contralateral shoulder motion-activated linear transducer signals was tested. The patient's input and injury type, along with the information from the prosthetic evaluation, were used to determine the reconstructive plan. The study also reviewed the number of participants opting for amputation and a myoelectric prosthetic hand for grasp restoration, and a follow-up survey was conducted to assess the impact of the initial evaluation on decision-making. RESULTS: Of 58 subjects evaluated, 47 (81%) had pan-plexus BPI and 42 (72%) received their initial assessment within 1 year post-injury. Forty-seven patients (81%) could control the virtual or model prosthetic hand using nonintuitive surface EMG signals, and all 58 could control it with contralateral uniscapular motion via a linear transducer and harness. Thirty patients (52%) chose and pursued amputation, and 20 (34%) actively used a myoelectric prosthesis for grasp. The initial evaluation was informative and beneficial for the majority of the patients, especially in demonstrating the functionality of the myoelectric prosthesis. CONCLUSIONS: The study indicates that adults with traumatic BPI can effectively operate a virtual or model myoelectric prosthesis using nonintuitive control signals. The simulation and multidisciplinary evaluation influenced informed treatment choices, with a high percentage of patients continuing to use the myoelectric prostheses post-amputation, highlighting its long-term acceptance and viability. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Small body size is associated with increased evolutionary lability of wing skeleton proportions in birds.

Birds are represented by 11,000 species and a great variety of body masses. Modular organisation of trait evolution across birds has facilitated simultaneous adaptation of different body regions to divergent ecological requirements. However, the role modularity has played in avian body size evolution, especially small-bodied, rapidly evolving and diverse avian subclades, such as hummingbirds and songbirds, is unknown. Modularity is influenced by the intersection of biomechanical restrictions, adaptation, and developmental controls, making it difficult to uncover the contributions of single factors such as body mass to skeletal organisation. We develop a novel framework to decompose this complexity, assessing factors underlying the modularity of skeletal proportions in fore-limb propelled birds distributed across a range of body masses. We demonstrate that differences in body size across birds triggers a modular reorganisation of flight apparatus proportions consistent with biomechanical expectations. We suggest weakened integration within the wing facilitates radiation in small birds. Our framework is generalisable to other groups and has the capacity to untangle the multi-layered complexity intrinsic to modular evolution.

Lymphovascular Invasion in Cutaneous Squamous Cell Carcinoma.

BACKGROUND: Although there is a large body of literature regarding risk stratification and outcomes for perineural invasion (PNI) in cutaneous squamous cell carcinoma (cSCC), there is a relative paucity of studies exploring the role of lymphovascular invasion (LVI) in cSCC and a lack of clear evidence-based guidelines for how to manage patients with these tumors. OBJECTIVE: This article is intended to review the available literature regarding LVI in cSCC and formulate evidence-based recommendations for clinical management. METHODS AND MATERIALS: A literature review was conducted using PubMed to find relevant articles relating to outcomes and management of primary cSCC with LVI. RESULTS: The available literature suggests that LVI is a major risk factor for poor outcomes and increased morbidity and mortality in cSCC. CONCLUSION: Lymphovascular invasion is a very high-risk feature that should place these tumors in the highest-risk category, and management of these tumors should be similar to that of squamous cell carcinoma with PNI.

Assembly and Repair of Photosystem II in Chlamydomonas reinhardtii.

Oxygenic photosynthetic organisms use Photosystem II (PSII) to oxidize water and reduce plastoquinone. Here, we review the mechanisms by which PSII is assembled and turned over in the model green alga Chlamydomonas reinhardtii. This species has been used to make key discoveries in PSII research due to its metabolic flexibility and amenability to genetic approaches. PSII subunits originate from both nuclear and chloroplastic gene products in Chlamydomonas. Nuclear-encoded PSII subunits are transported into the chloroplast and chloroplast-encoded PSII subunits are translated by a coordinated mechanism. Active PSII dimers are built from discrete reaction center complexes in a process facilitated by assembly factors. The phosphorylation of core subunits affects supercomplex formation and localization within the thylakoid network. Proteolysis primarily targets the D1 subunit, which when replaced, allows PSII to be reactivated and completes a repair cycle. While PSII has been extensively studied using Chlamydomonas as a model species, important questions remain about its assembly and repair which are presented here.

A Nurse-Led Algorithm for Diagnosing Urinary Tract Infection in Homebound Older Adults.

PURPOSE: We designed a nurse-led algorithm to standardize urinary tract infection (UTI) diagnosis for older adults receiving home-based medical care. Aims of this pilot quality improvement study were to reduce the frequency of empiric antibiotic therapy initiated without a urinalysis and urine culture (UA/UC) first being obtained, reduce antibiotic use without a concomitant increase in emergency department (ED) visits or hospital admissions, and ensure stakeholders' satisfaction with algorithm use. METHOD: A nurse-led diagnostic algorithm was designed and pilot-tested to address challenges and standardize diagnosis of UTI in a population of homebound older adults. RESULTS: In pre/post data analysis, algorithm implementation was associated with improved frequency of obtaining UA/UC before empiric antibiotic therapy was initiated, but the overall rate of antibiotic use for UTI did not decrease. No increase in ED or hospital admissions was identified. CONCLUSION: Use of a diagnostic algorithm for UTI among homebound older adults was associated with reduced frequency of empiric antibiotic initiation for suspected UTI without a UA/UC first being obtained. More rigorous study is needed to confirm and expand on these findings. [Research in Gerontological Nursing, 17(2), 92-97.].

Radiology Resident Ownership Scale (RROS): Adapting a Validated Measure of Patient Care Ownership to the Radiology Context.

RATIONALE AND OBJECTIVES: The aim of this study was to develop a validated instrument to measure radiology residents' sense of psychological ownership of patient care. MATERIALS AND METHODS: A previously validated measure of patient care ownership was adapted through a two-step process of expert review and revision by six academic radiology faculty. An online, anonymous survey was distributed to 64 residents and fellows at the end of three consecutive four-week long rotations. We calculated Cronbach's α to determine the scale's internal consistency, performed exploratory factor analysis to identify possible subscales, and conducted bivariate and correlational analysis to establish construct validity. RESULTS: The 11-item ownership scale demonstrated good internal consistency (Cronbach's α = 0.93), and three subscales were identified corresponding to assertiveness, conscientiousness, and confidence/perceived competence. Sense of ownership was significantly associated with training level, prior experience in the type of rotation, stress, sleep, burnout, peer support, relationships with clinical staff, and recognition by department. We found no significant association between ownership and age, gender, type of rotation, site of rotation, type of residency, perceived interruption frequency, or remote work frequency. CONCLUSION: The radiology resident patient care ownership scale demonstrates good internal consistency and preliminary evidence of validity. After further validation, we expect the scale to be a valuable tool in evaluating interventions aimed at increasing radiology residents' sense of ownership.

Perceptions and Attitudes Related to Driving after Cannabis Use in Canadian and US Adults.

BACKGROUND: This study examined the risk perceptions related to driving after cannabis use (DACU) among Canadian and US adults who used cannabis in the past six months. METHODS: Perceptions of danger, normative beliefs, perceived likelihood of negative consequences, and other driving-related variables were collected via online surveys in Canadian (n = 158; 50.0% female, 84.8% White, mean age = 32.73 years [SD = 10.61]) and US participants (n = 678; 50.9% female, 73.6% White, mean age = 33.85 years [SD = 10.12]). Driving cognitions and DACU quantity/frequency were compared between samples using univariate analyses of variance, and Spearman's (ρ) correlations were performed to examine associations between driving cognitions and DACU quantity/frequency. RESULTS: The two samples did not significantly differ in self-reported level of cannabis use, lifetime quantity of DACU, or the number of times they drove within two hours of cannabis use in the past three months (Ps > .12). Compared to US participants, Canadians perceived driving within two hours of cannabis use as more dangerous (P < 0.001, ηp2 = 0.013) and reported more of their friends would disapprove of DACU (P = 0.03, ηp2 = 0.006). There were no differences in the number of friends who would refuse to ride with a driver who had used cannabis (P = 0.15) or the perceived likelihood of negative consequences (Ps > 0.07). More favorable perceptions were significantly correlated with greater lifetime DACU and driving within two hours of use (ρ = 0.25-0.53, Ps < 0.01). CONCLUSIONS: These findings reveal differences in distal risk factors for DACU between Canada and the US and may inform prevention efforts focusing on perceptions of risk and social acceptance of DACU.

Applications of SPECT/CT in the Evaluation of Spinal Pathology: A Review.

BACKGROUND: Accurate identification of pain generators in the context of low back and spine-related pain is crucial for effective treatment. This review aims to evaluate the potential usefulness of single photon emission computed tomography with computed tomography (SPECT/CT) as an imaging modality in guiding clinical decision-making. METHODS: A broad scoping literature review was conducted to identify relevant studies evaluating the use of SPECT/CT in patients with spine-related pain. Studies were reviewed for their methodology and results. RESULTS: SPECT/CT appears to have advantages over traditional modalities, such as magnetic resonance imaging and CT, in certain clinical scenarios. It may offer additional information to clinicians and improve the specificity of diagnosis. However, further studies are needed to fully assess its diagnostic accuracy and clinical utility. CONCLUSIONS: SPECT/CT is a promising imaging modality in the evaluation of low back pain, particularly in cases where magnetic resonance imaging and CT are inconclusive or equivocal. However, the current level of evidence is limited, and additional research is needed to determine its overall clinical relevance. CLINICAL RELEVANCE: SPECT/CT may have a significant impact on clinical decision-making, particularly in cases in which traditional imaging modalities fail to provide a clear diagnosis. Its ability to improve specificity could lead to more targeted and effective treatment for patients with spinal pathology.

Barber Knowledge and Recommendations for Pseudofolliculitis Barbae.

This survey study describes an opportunity for a partnership between barbers and dermatologists to identify, evaluate, and treat pseudofolliculitis barbae in the Black male population.

Interventional Treatment of Symptomatic Vasospasm in the Setting of Traumatic Brain Injury: A Systematic Review of Reported Cases.

Traumatic subarachnoid hemorrhage (tSAH) is frequently comorbid with traumatic brain injury (TBI) and may induce secondary injury through vascular changes such as vasospasm and subsequent delayed cerebral ischemia (DCI). While aneurysmal SAH is well studied regarding vasospasm and DCI, less is known regarding tSAH and the prevalence of vasospasm and DCI, the consequences of vasospasm in this setting, when treatment is indicated, and which management strategies should be implemented. In this article, a systematic review of the literature that was conducted for cases of symptomatic vasospasm in patients with TBI is reported, association with tSAH is reported, risk factors for vasospasm and DCI are summarized, and commonalities in diagnosis and management are discussed. Clinical characteristics and treatment outcomes of 38 cases across 20 studies were identified in which patients with TBI with vasospasm underwent medical or endovascular management. Of the patients with data available for each category, the average age was 48.7 ± 20.3 years (n = 31), the Glasgow Coma Scale score at presentation was 10.6 ± 4.5 (n = 35), and 100% had tSAH (n = 29). Symptomatic vasospasm indicative of DCI was diagnosed on average at postinjury day 8.4 ± 3.0 days (n = 30). Of the patients, 56.6% (n = 30) had a new ischemic change associated with vasospasm confirming DCI. Treatment strategies are discussed, with 11 of 12 endovascularly treated and 19 of 26 medically treated patients surviving to discharge. tSAH is associated with vasospasm and DCI in moderate and severe TBI, and patients with clinical and radiographic evidence of symptomatic vasospasm and subsequent DCI may benefit from endovascular or medical management strategies.

The Relationship Between Postoperative Patient-Reported Psychological Outcomes and Preoperative Pain Characteristics in Patients Who Underwent Periacetabular Osteotomy.

This study sought to investigate the relationship between multiple preoperative characteristics of pain (maximum pain severity location, the presence of pain in certain locations, the highest level of pain, and the number of pain locations) and psychological outcome measures as reported by patients. Fifty-four hips (50 patients) that underwent periacetabular osteotomy to treat acetabular dysplasia between February 2017 and July 2020 were reviewed using the Depression, Anxiety, and Stress Scale-21 (DASS21), Hospital Anxiety and Depression Scale (HADS), and Pain Catastrophizing Scale (PCS), radiographic analysis, and questionnaires concerning pain severity/location. Twenty-six hips had their worst pain in the groin, whereas 28 hips had greater or equal levels of pain at another location. There was no significant difference between these two locations on any of the postoperative psychological outcomes (HADS, P=.53; DASS21, P=.85; PCS, P=.97). Additionally, there was not a significant relationship between pain in any location other than the groin and any postoperative psychological outcomes (P≥.08). Finally, the highest level of preoperative pain and the number of locations of pain demonstrated no significant relationship with postoperative psychological outcomes (maximum severity: HADS, P=.28; DASS21, P=.49; PCS, P=.57; number of pain locations: HADS, P=.47; DASS21, P=.60; PCS, P=.35). Variance in preoperative pain location, severity, and number of pain locations seemingly does not result in any significant effect on postoperative psychological outcomes. Thus, a large range of patients with acetabular dysplasia may experience similar, favorable psychological outcomes from treatment with periacetabular osteotomy notwithstanding the characteristics of preoperative pain. [Orthopedics. 2024;47(1):28-33.].

Fourth Chromosome Resource Project: a comprehensive resource for genetic analysis in Drosophila that includes humanized stocks.

The fourth chromosome is the final frontier for genetic analysis in Drosophila. Small, heterochromatic, and devoid of recombination the fourth has long been ignored. Nevertheless, its long arm contains 79 protein-coding genes. The Fourth Chromosome Resource Project (FCRP) has a goal of facilitating the investigation of genes on this neglected chromosome. The project has 446 stocks publicly available at the Bloomington and Kyoto stock centers with phenotypic data curated by the FlyBase and FlyPush resources. Four of the five stock sets are nearly complete: (1) UAS.fly cDNAs, (2) UAS.human homolog cDNAs, (3) gene trap mutants and protein traps, and (4) stocks promoting meiotic and mitotic recombination on the fourth. Ongoing is mutagenesis of each fourth gene on a new FRT-bearing chromosome for marked single-cell clones. Beyond flies, FCRP facilitates the creation and analysis of humanized fly stocks. These provide opportunities to apply Drosophila genetics to the analysis of human gene interaction and function. In addition, the FCRP provides investigators with confidence through stock validation and an incentive via phenotyping to tackle genes on the fourth that have never been studied. Taken together, FCRP stocks will facilitate all manner of genetic and molecular studies. The resource is readily available to researchers to enhance our understanding of metazoan biology, including conserved molecular mechanisms underlying health and disease.

Adaptation of commodity purchase tasks to identify substitutable substance-free alternative activities for alcohol use.

Behavioral economic frameworks emphasize the importance of contextual influences on alcohol use; therefore, identifying relative demand for alcohol versus other commodities is of importance. Cross-commodity purchase tasks allow participants to make choices across multiple concurrently available commodities and can thereby pinpoint interactions among those commodities. These tasks may help identify relevant substance-free alternative activities to target in alcohol treatment by determining whether the activity functions as a substitute for alcohol use. While substance-free activity promotion is a promising behavioral component of alcohol interventions, no research to-date has used behavioral economic methods to assess the substitutability of alternative activities for alcohol use. The present studies were preliminary assessments of novel single- and cross-commodity purchase tasks of various alternative activities (e.g., exercise, hobbies, civic involvement). Participants in Study 1 recruited from Amazon's Mechanical Turk (n = 110) were administered a series of novel activity purchase tasks and an alcohol purchase task. Results showed excellent fit of the exponential demand equation to activity purchase task data and provided initial support for adaptation of purchase task methodology to alternative activity demand. In Study 2, participants recruited from Amazon's Mechanical Turk (n = 108) were administered both single-commodity and cross-commodity purchase tasks of alcohol and exercise. While most participants demonstrate independent consumption of alcohol and exercise, a subset of participants substituted exercise for alcohol as indicated by quantitative cross-price elasticity indices. These response patterns highlight the importance of individual differences and hold implications for recovery efforts that promote alternative activity engagement and public policy. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Conformational changes in a Photosystem II hydrogen bond network stabilize the oxygen-evolving complex.

The Mn4CaO5 oxygen-evolving complex (OEC) in Photosystem II (PSII) is assembled in situ and catalyzes water oxidation. After OEC assembly, the PsbO extrinsic subunit docks to the lumenal face of PSII and both stabilizes the OEC and facilitates efficient proton transfer to the lumen. D1 residue R334 is part of a hydrogen bond network involved in proton release during catalysis and interacts directly with PsbO. D1-R334 has recently been observed in different conformations in apo- and holo-OEC PSII structures. We generated a D1-R334G point mutant in Synechocystis sp. PCC 6803 to better understand this residue's function. D1-R334G PSII is active under continuous light, but the OEC is unstable in darkness. Isolated D1-R334G core complexes have little bound PsbO and less manganese as the wild type control. The S2 intermediate is stabilized in D1-R334G indicating that the local environment around the OEC has been altered. These results suggest that the hydrogen bond network that includes D1-R334 exists in a different functional conformation during PSII biogenesis in the absence of PsbO.