Concordance and validity between versions of the ADHD Conners scale for Parents.

INTRODUCTION: The Conners Scale for Parents (CRS-P) is one of the reference tools for the diagnostic assessment of Attention Deficit and Hyperactivity Disorders (ADHD). It is commonly used in both research and clinical practice. The latest edition of the Conners Parents Scale Long Version (CRS-P3L) has undergone extensive modifications but has never been compared with the 2nd edition (CRS-P2L). We aim to study the concordance between the last two editions of the CRS-P, their internal consistency, and their validity against the criteria of the ADHD-RS. METHODS: The study population was a cohort of 30 children diagnosed with ADHD participating in a clinical trial. The parents of these children completed both editions of the CRS (P2L and P3L), as well as a DSM-IV ADHD Diagnostic Criteria Rating Scale (ADHD-RS). A linear regression model with the calculation of Lin's concordance coefficient (LCC) was used to study the concordance between the scales. Internal validity was estimated with Cronbach's alpha and inter-criteria validity with Spearman's correlation coefficient. RESULTS: The internal consistency found was "correct" to "good" for both editions (Cronbach alpha 0.85 and 0.77), their correlation with the ADHD-RS was medium to low (Spearman's coefficient 0.25 and 0.09). Concordance between the overall score and the sub-scores of the two editions of the same Conners scale (CRS-P2L and CRS-P3L) was fair to medium (LCC 0.29 to 0.69). CONCLUSIONS: The third edition of the long version of the CRS-P showed very poor concordance with the previous edition. The diagnostic profile of the children seems to have evolved with the new edition, which appears to affect the interpretation of the tests.

Molecular determinants of Hsp90 dependence of Src kinase revealed by deep mutational scanning.

Hsp90 is a molecular chaperone involved in the refolding and activation of numerous protein substrates referred to as clients. While the molecular determinants of Hsp90 client specificity are poorly understood and limited to a handful of client proteins, strong clients are thought to be destabilized and conformationally extended. Here, we measured the phosphotransferase activity of 3929 variants of the tyrosine kinase Src in both the presence and absence of an Hsp90 inhibitor. We identified 84 previously unknown functionally dependent client variants. Unexpectedly, many destabilized or extended variants were not functionally dependent on Hsp90. Instead, functionally dependent client variants were clustered in the αF pocket and ß1-ß2 strand regions of Src, which have yet to be described in driving Hsp90 dependence. Hsp90 dependence was also strongly correlated with kinase activity. We found that a combination of activation, global extension, and general conformational flexibility, primarily induced by variants at the αF pocket and ß1-ß2 strands, was necessary to render Src functionally dependent on Hsp90. Moreover, the degree of activation and flexibility required to transform Src into a functionally dependent client varied with variant location, suggesting that a combination of regulatory domain disengagement and catalytic domain flexibility are required for chaperone dependence. Thus, by studying the chaperone dependence of a massive number of variants, we highlight factors driving Hsp90 client specificity and propose a model of chaperone-kinase interactions.

An overview of the role of selpercatinib and pralsetinib in RET-fusion-positive non-small cell lung cancer (NSCLC).

OBJECTIVE: Selpercatinib and pralsetinib are new targeted therapies used to treat patients with non-small cell lung cancer (NSCLC) due to RET gene rearrangements. The objective of this article is to review selpercatinib and pralsetinib in the context of RET-fusion-positive NSCLC. DATA SOURCES: The pivotal LIBRETTO-001 and ARROW trials were evaluated regarding the use of selpercatinib and pralsetinib as treatment for RET-fusion-positive NSCLC. Comparative studies, review articles and current studies on selpercatinib and pralsetinib in RET-fusion-positive NSCLC were searched on pubmed.org and scholar.google.com using "selpercatinib," "pralsetinib," and "NSCLC" as keywords. Product monographs were searched on google.ca and uptodate.com using the keywords "selpercatinib," "pralsetinib," and/or "monograph." DATA SUMMARY: Selpercatinib and pralsetinib are orally administered highly selective RET inhibitors approved by the FDA following the accelerated approvals granted due to the pivotal LIBRETTO-001 and ARROW trials which evaluated selpercatinib and pralsetinib, respectively. Both drugs have shown efficacy for brain metastases and are primarily metabolized by CYP3A4 through hepatic metabolism. The most common grade 3 or 4 adverse effects of selpercatinib were hypertension, increased ALT level, and increased AST level while for pralsetinib, it was neutropenia, hypertension, and anemia. The safety profile shows similarities in severity and tolerability but additional monitoring for QT prolongation in patients on selpercatinib is recommended, compared to the risks of interstitial lung disease or pneumonitis for patients on pralsetinib. CONCLUSIONS: Overall, the increased use of selpercatinib and pralsetinib has led to the implementation of these drugs in the clinical practice of healthcare professionals such as pharmacists.

Pregnancy outcomes in women with primary systemic vasculitis: a retrospective study.

BACKGROUND/AIMS: Pregnancies in women with systemic vasculitis constitute high-risk pregnancies, and outcomes vary based on the size of the affected blood vessels. Currently, there is limited data describing pregnancy outcomes in these women. The aim of this paper is to evaluate pregnancy outcomes in women with large, medium, or small vessel vasculitis to aid preconceptional counseling and inform antepartum and intrapartum care. METHODS: We included all women with large-, medium-, or small-vessel vasculitis and documented pregnancies attending high-risk pregnancy clinics at Mount Sinai Hospital, Toronto, Canada between 2001 and 2016. Pregnancy characteristics and outcomes were reported as proportions. Maternal, fetal/neonatal, and obstetric outcomes, stratified by type of vasculitis, were the main outcomes measured. RESULTS: We identified 60 pregnancies in 50 women with systemic vasculitis. These included large-vessel (n = 10), medium-vessel (n = 5), small-vessel [n = 30, of which 16 were AntiNeutrophil Cytoplasmic Autoantibody (ANCA)-associated and 14 were immune-complex mediated], central nervous system (n = 3), and retinal (n = 2). Although vasculitis flares occurred with large-vessel (3/12), small-vessel (13/36), and retinal (2/3) vasculitis, only one was severe and involved hemoptysis requiring blood transfusion in a woman with ANCA-associated vasculitis. Preeclampsia complicated two pregnancies each with large- (25%) and small- (6%) vessel vasculitis. Intrauterine growth restriction (IUGR) only occurred with small-vessel vasculitis (10, 29.4%). Although seven (26.4%) viable pregnancies resulted in preterm birth, the mean gestational age was over 35 weeks. CONCLUSION: Although women with systemic vasculitis can have successful pregnancies, they are at increased risk for late preterm birth. In addition, those with small-vessel vasculitis are at increased risk for IUGR and vasculitis flares.

Retrospective case analysis of antiviral therapies for HHV-6 encephalitis after hematopoietic stem cell transplantation.

Human herpesvirus 6 (HHV-6) is one of the most common causes of encephalitis in allogeneic hematopoietic stem cell transplant (HCT) recipients and is associated with significant morbidity and mortality. There are no FDA-approved treatments specifically for HHV-6 encephalitis; HHV-6 disease is typically treated with CMV antivirals. A review of antiviral medications used to treat HHV-6 encephalitis was conducted by aggregating data from case reports found on PubMed. Articles were included if they examined at least one HCT patient diagnosed with HHV-6 encephalitis and described their treatment course and outcome. Key data were abstracted from 123 cases described in 52 studies. The proportion of patients with encephalitis who died or developed sequelae was 63.6% among ganciclovir monotherapy recipients (n = 44), 55.3% among foscarnet monotherapy recipients (n = 47), and 37.5% among recipients of combination therapy with foscarnet and ganciclovir (n = 32). Logistic regression revealed that recipients of foscarnet (OR 4.286, 95% CI 1.235-14.877, P = .022) and ganciclovir (OR 5.625, 95% CI 1.584-19.975, P = .008) monotherapies were more likely to develop sequelae compared to recipients of combination therapy, respectively. In multivariate analyses, non-cord blood transplant was identified as an independent risk factor for developing sequelae after receiving ganciclovir monotherapy (OR 5.999, 95% CI 1.274-28.254, P = .023). There was no difference in mortality between patients who received combination therapy and those who received monotherapy. In conclusion, combination therapy with foscarnet and ganciclovir may reduce sequelae, but not mortality, secondary to HHV-6 encephalitis.

Pregnancy and Neuromyelitis Optica Spectrum Disorder - Reciprocal Effects and Practical Recommendations: A Systematic Review.

Introduction: Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disorder of the central nervous system characterized by severe, antibody-mediated astrocyte loss with secondary demyelination and axonal damage, predominantly targeting optic nerves and the spinal cord. Recent publications have alluded to increased disease activity during pregnancy, and adverse maternal and fetal outcomes in patients with NMOSD. Our objective was to systematically review published literature to help counsel and manage women with NMOSD contemplating pregnancy. Methods: We searched five databases including MEDLINE and EMBASE, for English-language publications describing pregnancies in women with NMOSD. Article selection, data extraction, and risk-of-bias assessment using Joanna Briggs' critical appraisal tool for case reports and case series, were performed in duplicate. Pooled incidences were calculated where possible, and a narrative summary was provided. Results: Of 2,118 identified titles, 22 case reports and seven case series, representing 595 pregnancies in 389 women, were included. The mean maternal age was 28.12 ± 5.19 years. At least 20% of cases were first diagnosed during pregnancy. There were no maternal deaths. Pooled estimates for clinical outcomes could not be obtained due to inadequate reporting. NMOSD-related disability and relapses increased considerably during pregnancy and especially in the immediate postpartum period. Although a high proportion of early pregnancy losses were reported, an association with disease activity or therapeutic interventions could not be established. Apart from one publication which reported an increased risk of preeclampsia, there was no increase in adverse obstetric outcomes including preterm birth, fetal growth restriction or congenital malformations. Initial attacks and relapses were successfully managed with oral or intravenous corticosteroids and immunosuppressants, and refractory cases with immunoglobulin, plasma exchange and immunoadsorption. Conclusion: Increased NMOSD-related disability and relapses during pregnancy the postpartum period may respond to aggressive management with corticosteroids and immunosuppressants such as azathioprine, which are safely administered during pregnancy and lactation. Emerging safety data on monoclonal antibodies during pregnancy, make these attractive options, while intravenous immunoglobulin, plasma exchange and immunoadsorption can be safely used to treat severe relapses. The complex interplay between NMOSD and pregnancy outcomes would be best understood through prospective analysis of data collected through an international registry. Disclosure: Dalia Rotstein has served as a consultant or speaker for Alexion and Roche. She has received research support from Roche Canada. Rohan D'Souza has served as a consultant and speaker for Ferring Canada Inc and Ferring Global Inc, on topics unrelated to this manuscript. The other authors have no relevant relationships to disclose.

pH-responsive high stability polymeric nanoparticles for targeted delivery of anticancer therapeutics.

The practical application of nanoparticles (NPs) as chemotherapeutic drug delivery systems is often hampered by issues such as poor circulation stability and targeting inefficiency. Here, we have utilized a simple approach to prepare biocompatible and biodegradable pH-responsive hybrid NPs that overcome these issues. The NPs consist of a drug-loaded polylactic-co-glycolic acid (PLGA) core covalently 'wrapped' with a crosslinked bovine serum albumin (BSA) shell designed to minimize interactions with serum proteins and macrophages that inhibit target recognition. The shell is functionalized with the acidity-triggered rational membrane (ATRAM) peptide to facilitate internalization specifically into cancer cells within the acidic tumor microenvironment. Following uptake, the unique intracellular conditions of cancer cells degrade the NPs, thereby releasing the chemotherapeutic cargo. The drug-loaded NPs showed potent anticancer activity in vitro and in vivo while exhibiting no toxicity to healthy tissue. Our results demonstrate that the ATRAM-BSA-PLGA NPs are a promising targeted cancer drug delivery platform.

Using Socioenvironmental Report Cards as a Tool for Transdisciplinary Collaboration.

The process of developing a socioenvironmental report card through transdisciplinary collaboration can be used in any system and can provide the foundation for collaborative solutions for sustainable resource management by creating a holistic assessment that balances environmental, economic, and social concerns that incorporates multiple perspectives from multisectoral actors. We demonstrated this in the Mississippi River watershed, USA with the ultimate goal of promoting holistic management of the region's natural resources. But working at the scale of the Mississippi River watershed presents the challenge of working across geographical, organizational, and disciplinary boundaries. The development of a socioenvironmental report card served as the focus for efforts to foster a shared vision among diverse stakeholders in the watershed and to promote transdisciplinary collaboration. The process engaged more than 700 participants from environment, flood control, transportation, water supply, economy, and recreation sectors, from more than 400 organizations representing local, state, and federal government agencies, businesses and trade associations, and private, nonprofit, and academic institutions. This broad engagement in the selection of important themes, indicators, measures, and assessment methods as part of the cocreation of boundary objects aimed to foster social and mutual learning and to develop common understanding and shared visioning among stakeholders with differing perspectives. The process was facilitated by boundary-spanning organizations, creating an atmosphere of trust by utilizing "third places" for knowledge exchange and integration. This transdisciplinary process also led to collective action through collaboration and selection of restoration and management activities that could improve conditions for multiple sectors simultaneously and/or recognize potential tradeoffs for informed decision making. Integr Environ Assess Manag 2020;16:494-507. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

The Effect of Phosphatidylserine on a pH-Responsive Peptide Is Defined by Its Noninserting End.

The acidity-triggered rational membrane (ATRAM) peptide was designed to target acidic diseases such as cancer. An acidic extracellular medium, such as that found in aggressive tumors, drives the protonation of the glutamic acids in ATRAM, leading to the membrane translocation of its C-terminus and the formation of a transmembrane helix. Compared to healthy cells, cancerous cells often increase exposure of the negatively charged phosphatidylserine (PS) on the outer leaflet of the plasma membrane. Here we use a reconstituted vesicle system to explore how PS influences the interaction of ATRAM with membranes. To explore this, we used two new variants of ATRAM, termed K2-ATRAM and Y-ATRAM, with small modifications at the noninserting N-terminus. We observed that the effect of PS on the membrane insertion pK and lipid partitioning hinged on the sequence of the noninserting end. Our data additionally indicate that the effect of PS on the insertion pK does not merely depend on electrostatics, but it is multifactorial. Here we show how small sequence changes can impact the interaction of a peptide with membranes of mixed lipid composition. These data illustrate how model studies using neutral bilayers, which do not mimic the negative charge found in the plasma membrane of cancer cells, may fail to capture important aspects of the interaction of anticancer peptides with tumor cells. This information can guide the design of therapeutic peptides that target the acidic environments of different diseased tissues.

Mechanistic insights into the pH-dependent membrane peptide ATRAM.

pH-responsive peptides are promising therapeutic molecules that can specifically target the plasma membrane in the acidified extracellular medium that bathes cells in tumors. We designed the acidity-triggered rational membrane (ATRAM) peptide to have a pH-responsive membrane interaction. At physiological pH, ATRAM binds to the membrane surface in a largely unstructured conformation, while in acidic conditions it inserts into lipid bilayers forming a transmembrane helix. However, the molecular mechanism ATRAM uses to target and insert into tumor cells remains poorly understood. Here, we determined that ATRAM inserts into cancer cells with a preferential membrane orientation, where the C-terminus of the peptide traverses the plasma membrane and explores the cytoplasm. Using biophysical techniques, we determined that the membrane interaction of ATRAM is contingent on the concentration of the peptide. Kinetic studies showed that membrane insertion occurs in at least three steps, where only the first step was affected by the membrane density of ATRAM. These observations, combined with membrane binding and leakage data, indicate that the interaction of ATRAM with lipid membranes is dependent on its oligomerization state. SPECT/CT imaging in mice revealed that ATRAM accumulates in the blood pool, where it has a prolonged circulation time (> 4 h). Since fast peptide clearance and degradation in circulation are major problems for clinical development, we studied the mechanism ATRAM uses to remain in the blood stream. Using binding and transfer assays, we determined that ATRAM binds reversibly to human serum albumin. We propose that ATRAM uses albumin as a carrier in the blood stream to evade clearance and proteolysis before interacting with the plasma membrane of cancer cells. We also show that ATRAM is able to be deliver liposomes to cells in a pH dependent way. Our data highlight the potential of ATRAM as a specific therapeutic agent for diseases that lead to acidic tissues, including cancer.

Anecdote or Reality: Are People From the South and/or Rural Areas of the USA More Empathetic?

Although numerous studies have analyzed empathy scores of allopathic and osteopathic medical students and how these scores fluctuate throughout undergraduate medical education, little is known about whether demographics have an impact on medical students' empathy scores. Using the Balanced Emotional Empathy Scale (BEES) and Jefferson Scale of Empathy (JSE) surveys to measure affective and cognitive empathy, respectively, this present study examined the relationship between empathy scores with the following demographic data from first and second year students at a southeastern US osteopathic medical school: the classification of whether students came from a rural or urban background, the region of the US students lived in prior to matriculation to medical school, and the town/city size of where they were currently living at the time of applying to medical school. Data analyses showed only one statistically significant data point (p < 0.04) that revealed first year osteopathic medical students (OMS-I) from towns with < 10,000 occupants had higher JSE scores in comparison to students coming from towns with 50,000-99,999 occupants. However, trends could be established. For example, anecdotally, it is often presumed people from the southern United States tend to be friendlier than those from the northern states; however, contrary to this, the data revealed OMS-I students from the southern United States had a slightly lower BEES scores than OMS-I students from the northeastern states. JSE scores were nearly identical across all four US census bureau regions. Additionally, OMS-I students coming from an urban background had a higher BEES scores than those coming from a rural background. Compared to population norms, combined male and female BEES scores for OMS-I and -II students were within ± 0.5 s.d. of the norm and are considered to be "average" scores. Combined OMS-I JSE scores were below the population norm at the 37th percentile, and combined OMS-II JSE scores were also at the 37th percentile, except for students from the western region at the 44th percentile.

Devic syndrome and pregnancy: A case series.

BACKGROUND: Devic syndrome or neuromyelitis optica is an autoimmune neurological condition characterized by relapsing symptoms of optic neuritis and transverse myelitis. Women with neuromyelitis optica suffer from adverse pregnancy outcomes and high relapse rates during pregnancy and the postpartum period. METHODS: This case series describes 13 pregnancies in four women with neuromyelitis optica managed at a tertiary hospital in Toronto, Canada. RESULTS: In most cases, neurologic symptoms either worsened or developed for the first time during pregnancy or the postpartum period, and often responded to a combination of steroids, immunosuppressant medications, plasma exchange and intravenous immunoglobulin. The 13 pregnancies resulted in two miscarriages, three preterm and eight term births. One fetus whose mother was on gabapentin, prednisone and spironolactone, had congenital malformations (aplastic lung and fused fingers). CONCLUSIONS: Despite high frequency of relapses in pregnancy and the postpartum period, with multidisciplinary team management, outcomes for women with neuromyelitis optica are encouraging.

A novel pH-dependent membrane peptide that binds to EphA2 and inhibits cell migration.

Misregulation of the signaling axis formed by the receptor tyrosine kinase (RTK) EphA2 and its ligand, ephrinA1, causes aberrant cell-cell contacts that contribute to metastasis. Solid tumors are characterized by an acidic extracellular medium. We intend to take advantage of this tumor feature to design new molecules that specifically target tumors. We created a novel pH-dependent transmembrane peptide, TYPE7, by altering the sequence of the transmembrane domain of EphA2. TYPE7 is highly soluble and interacts with the surface of lipid membranes at neutral pH, while acidity triggers transmembrane insertion. TYPE7 binds to endogenous EphA2 and reduces Akt phosphorylation and cell migration as effectively as ephrinA1. Interestingly, we found large differences in juxtamembrane tyrosine phosphorylation and the extent of EphA2 clustering when comparing TYPE7 with activation by ephrinA1. This work shows that it is possible to design new pH-triggered membrane peptides to activate RTK and gain insights on its activation mechanism.

Membrane Bending Moduli of Coexisting Liquid Phases Containing Transmembrane Peptide.

A number of highly curved membranes in vivo, such as epithelial cell microvilli, have the relatively high sphingolipid content associated with "raft-like" composition. Given the much lower bending energy measured for bilayers with "nonraft" low sphingomyelin and low cholesterol content, observing high curvature for presumably more rigid compositions seems counterintuitive. To understand this behavior, we measured membrane rigidity by fluctuation analysis of giant unilamellar vesicles. We found that including a transmembrane helical GWALP peptide increases the membrane bending modulus of the liquid-disordered (Ld) phase. We observed this increase at both low-cholesterol fraction and higher, more physiological cholesterol fraction. We find that simplified, commonly used Ld and liquid-ordered (Lo) phases are not representative of those that coexist. When Ld and Lo phases coexist, GWALP peptide favors the Ld phase with a partition coefficient of 3-10 depending on mixture composition. In model membranes at high cholesterol fractions, Ld phases with GWALP have greater bending moduli than the Lo phase that would coexist.

Computational design of self-assembling cyclic protein homo-oligomers.

Self-assembling cyclic protein homo-oligomers play important roles in biology, and the ability to generate custom homo-oligomeric structures could enable new approaches to probe biological function. Here we report a general approach to design cyclic homo-oligomers that employs a new residue-pair-transform method to assess the designability of a protein-protein interface. This method is sufficiently rapid to enable the systematic enumeration of cyclically docked arrangements of a monomer followed by sequence design of the newly formed interfaces. We use this method to design interfaces onto idealized repeat proteins that direct their assembly into complexes that possess cyclic symmetry. Of 96 designs that were characterized experimentally, 21 were found to form stable monodisperse homo-oligomers in solution, and 15 (four homodimers, six homotrimers, six homotetramers and one homopentamer) had solution small-angle X-ray scattering data consistent with the design models. X-ray crystal structures were obtained for five of the designs and each is very close to their corresponding computational model.

Theoretical study of the interactions between the first transmembrane segment of NS2 protein and a POPC lipid bilayer.

Non-structural protein 2 (NS2) plays a crucial role in the hepatitis C virus (HCV) assembly. NS2 was predicted to be composed of three transmembrane (TM) segments. However, the mechanism of interactions between TM segments of NS2 and surrounding lipid environment remains unclear. Molecular dynamics simulations were applied to investigate the conformation and orientation of the first transmembrane segment (TM1) as well as the interactions of TM1 with a zwitterionic POPC lipid bilayer which identifies several key residues that stabilize the position of TM1 within the membrane. Along with the charged residues R3 and K27, the S23 and H25 were found to be the key elements in establishing the conformation of TM1 inside the membrane. The peptide forms a stable α-helix (the sequence 12-21) connected to N-terminal haft in POPC bilayer. The results also reveal that TM1 induces the ordering of lipid and does not destabilize the lipid bilayer system. The hydrophobic mismatch in which the segment tilts an angle along the membrane normal was observed in this system. The binding free energy profile of TM1 to the membrane was also estimated using umbrella sampling.

A Novel Soluble Peptide with pH-Responsive Membrane Insertion.

Several diseases, such as cancer, are characterized by acidification of the extracellular environment. Acidosis can be employed as a target to specifically direct therapies to the diseased tissue. We have used first principles to design an acidity-triggered rational membrane (ATRAM) peptide with high solubility in solution that is able to interact with lipid membranes in a pH-dependent fashion. Biophysical studies show that the ATRAM peptide binds to the surface of lipid membranes at pH 8.0. However, acidification leads to the peptide inserting into the lipid bilayer as a transmembrane α-helix. The insertion of ATRAM into membranes occurs at a moderately acidic pH (with a pK of 6.5), similar to the extracellular pH found in solid tumors. Studies with human cell lines showed a highly efficient pH-dependent membrane targeting, without causing toxicity. Here we show that it is possible to rationally design a soluble peptide that selectively targets cell membranes in acidic environments.

The negative charge of the membrane has opposite effects on the membrane entry and exit of pH-low insertion peptide.

The pH-low insertion peptide (pHLIP) targets acidic diseases such as cancer. The acidity of the environment causes key aspartic acids in pHLIP to become protonated, causing the peptide to insert into membranes. Here we investigate how the negative charge of the membrane influences how pHLIP enters and exits the lipid bilayer. We found that electrostatic repulsion affected differently the membrane entry and exit of pHLIP for negatively charged membranes. As a consequence, a large hysteresis was observed. We propose this is not a consequence of structural changes but results from local changes in the environment of aspartic acids, shifting their pK values.

Antimicrobial activity of water-soluble triazole phenazine clickamers against E. coli.

The antimicrobial potency of phenazine derivatives is attenuated by their inherently hydrophobic nature, complicating their use as antibiotic drugs. We have analyzed the cytotoxicity and mode of action of water-soluble bis-triazolyl phenazines against E. coli and a human epithelial (HaCat) cell line. We observed complete inhibition of bacterial growth over concentration ranges that do not affect the viability of human epithelial cells. Confocal fluorescence microscopy revealed a high degree of interaction between the phenazine compounds and E. coli, as well as evidence of membrane damage in phenazine-treated E. coli. Additional data suggests that the potency of these particular water-soluble phenazine compounds does not result from the production of reactive oxygen species, but rather from cytotoxic interference with metabolic electron-transfer cascades.