Assembly and Analysis of Cell-Scale Membrane Envelopes.

The march toward exascale computing will enable routine molecular simulation of larger and more complex systems, for example, simulation of entire viral particles, on the scale of approximately billions of atoms─a simulation size commensurate with a small bacterial cell. Anticipating the future hardware capabilities that will enable this type of research and paralleling advances in experimental structural biology, efforts are currently underway to develop software tools, procedures, and workflows for constructing cell-scale structures. Herein, we describe our efforts in developing and implementing an efficient and robust workflow for construction of cell-scale membrane envelopes and embedding membrane proteins into them. A new approach for construction of massive membrane structures that are stable during the simulations is built on implementing a subtractive assembly technique coupled with the development of a structure concatenation tool (fastmerge), which eliminates overlapping elements based on volumetric criteria rather than adding successive molecules to the simulation system. Using this approach, we have constructed two "protocells" consisting of MARTINI coarse-grained beads to represent cellular membranes, one the size of a cellular organelle and another the size of a small bacterial cell. The membrane envelopes constructed here remain whole during the molecular dynamics simulations performed and exhibit water flux only through specific proteins, demonstrating the success of our methodology in creating tight cell-like membrane compartments. Extended simulations of these cell-scale structures highlight the propensity for nonspecific interactions between adjacent membrane proteins leading to the formation of protein microclusters on the cell surface, an insight uniquely enabled by the scale of the simulations. We anticipate that the experiences and best practices presented here will form the basis for the next generation of cell-scale models, which will begin to address the addition of soluble proteins, nucleic acids, and small molecules essential to the function of a cell.

A membrane-embedded pathway delivers general anesthetics to two interacting binding sites in the Gloeobacter violaceus ion channel.

General anesthetics exert their effects on the central nervous system by acting on ion channels, most notably pentameric ligand-gated ion channels. Although numerous studies have focused on pentameric ligand-gated ion channels, the details of anesthetic binding and channel modulation are still debated. A better understanding of the anesthetic mechanism of action is necessary for the development of safer and more efficacious drugs. Herein, we present a computational study identifying two anesthetic binding sites in the transmembrane domain of the Gloeobacter violaceus ligand-gated ion channel (GLIC) channel, characterize the putative binding pathway, and observe structural changes associated with channel function. Molecular simulations of desflurane reveal a binding pathway to GLIC via a membrane-embedded tunnel using an intrasubunit protein lumen as the conduit, an observation that explains the Meyer-Overton hypothesis, or why the lipophilicity of an anesthetic and its potency are generally proportional. Moreover, employing high concentrations of ligand led to the identification of a second transmembrane site (TM2) that inhibits dissociation of anesthetic from the TM1 site and is consistent with the high concentrations of anesthetics required to achieve clinical effects. Finally, asymmetric binding patterns of anesthetic to the channel were found to promote an iris-like conformational change that constricts and dehydrates the ion pore, creating a 13.5 kcal/mol barrier to ion translocation. Together with previous studies, the simulations presented herein demonstrate a novel anesthetic binding site in GLIC that is accessed through a membrane-embedded tunnel and interacts with a previously known site, resulting in conformational changes that produce a non-conductive state of the channel.

A "cross-stitched" peptide with improved helicity and proteolytic stability.

A new computational approach to obtain quantitative energy profiles for helix folding was used in the design of orthogonal hydrocarbon and lactam bicyclic peptides. The proteolytically stable, "cross-stitched" peptide SRC2-BCP1 shows nanomolar affinity for estrogen receptor α and X-ray crystallography confirms a helical binding pose.

Surgery for recurrent stress urinary incontinence: the views of surgeons and women.

INTRODUCTION AND HYPOTHESIS: The objectives were to explore the views of women with recurrent stress incontinence (SUI) with regard to treatment preferences and the acceptability of randomisation to a future trial, and to survey the views of UK specialists on treatment preferences and equipoise regarding different treatment alternatives. METHODS: An online survey of the British Society of Urogynaecology (BSUG) and British Society of Urological Surgeons (BAUS) was carried out. Qualitative semi-structured interviews with a purposive sample of surgeons and women suffering from recurrent SUI from three UK centres. RESULTS: Two hundred fifty-six survey replies were received (176 gynaecology; 80 urology). Comparing the treatments offered, urogynaecologists were more likely to offer pelvic floor exercises (p < 0.05), and repeat midurethral tape (MUT) (p < 0.001). From the Surgical Equipoise Scale (SES) responses, "no preference" was rarely the commonest response. Marked differences for several options existed; midurethral tape dominated responses whenever it appeared. Twenty-one clinicians were interviewed. Treatment preferences were complex, influenced by a range of factors (reason for failure, patient comorbidity, investigations, personal experience, training). A future trial was regarded as important. Eleven women were interviewed. Most had considered more than one option, but felt that decision-making was more a process of elimination rather than a positive process. Randomisation to a study was regarded as unacceptable by most. CONCLUSIONS: No consensus exists among surgeons about preferred treatment options for recurrent SUI, and personal experience and training dominate decision-making. For patients, choices were usually based on an elimination of options, including that of a repeat failed procedure. This contrasts with surgeons, who mostly preferred a repeat MUT above other options. Any future comparative study will be challenging.

The cellular membrane as a mediator for small molecule interaction with membrane proteins.

The cellular membrane constitutes the first element that encounters a wide variety of molecular species to which a cell might be exposed. Hosting a large number of structurally and functionally diverse proteins associated with this key metabolic compartment, the membrane not only directly controls the traffic of various molecules in and out of the cell, it also participates in such diverse and important processes as signal transduction and chemical processing of incoming molecular species. In this article, we present a number of cases where details of interaction of small molecular species such as drugs with the membrane, which are often experimentally inaccessible, have been studied using advanced molecular simulation techniques. We have selected systems in which partitioning of the small molecule with the membrane constitutes a key step for its final biological function, often binding to and interacting with a protein associated with the membrane. These examples demonstrate that membrane partitioning is not only important for the overall distribution of drugs and other small molecules into different compartments of the body, it may also play a key role in determining the efficiency and the mode of interaction of the drug with its target protein. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.

Patient factors associated with onabotulinum toxin A treatment outcome in women with detrusor overactivity.

OBJECTIVE: To evaluate potential predictors of non-response to treatment with 200U onabotulinum toxin A (onaBoNTA) in women with refractory detrusor overactivity (DO). SUBJECTS AND METHODS: A secondary analysis of a randomized trial of 200U onaBoNTA versus placebo in women with refractory DO analyzed baseline and 6 week follow-up data. Univariate and multivariate logistic regression were used to assess demographic factors and baseline clinical parameters on non-response to treatment defined as 20% or less improvement in urinary urgency and leakage episodes, 10% or less in voiding frequency, not achieving continence, and "no change" or worse on PGI-I score at 6 weeks. RESULTS: One Hundred and twenty-two women were included. Twenty-nine (23.8%), 24 (19.7%), and 19 (15.6%) were non-responders to treatment for urgency, voiding, and leakage episodes, respectively. Fifty-nine (48.4%) failed to achieve continence, and 28 (23%) were non-responders on the PGI-I scale. Smoking status (OR: 2.89 95%CI 1.08, 7.73, P = 0.034) predicted non-response in urgency episodes, and higher baseline leakage episodes (OR: 1.17 95%CI 1.04, 1.31, P = 0.007) predicted non-response in achieving continence. Increasing age (OR 1.04, 95%CI 1.0, 1.09, P = 0.063) and body mass index (BMI) (OR 1.07, 95%CI 1.0, 1.16, P = 0.065) showed marginal associations with non-response on the PGI-I scale. CONCLUSION: onaBoNTA is an effective treatment for refractory DO, but some fail to respond. For identification of women at risk, our data indicate smokers should be advised of a lesser chance of successful treatment. Older women, those with high BMI and with more severe leakage also have a higher risk of failure. Neurourol. Urodynam. 36:426-431, 2017. © 2016 Wiley Periodicals, Inc.

Comparison of the effectiveness of repeated injections of onabotulinum toxin A for refractory idiopathic detrusor overactivity: analysis of an open label extension of a randomized trial (the RELAX study).

AIMS: To assess effects of repeat treatment with onabotulinumtoxin A (onaBoNT-A) in women with refractory idiopathic detrusor overactivity (DO). METHODS: Analysis of an open-label extension study of a large randomized placebo controlled trial of onaBoNT-A. Participants had been randomized to receive 200 IU onaBoNTA or placebo and were offered up to two further onaBoNTA injections over a 5-year period. For this analysis, the primary outcome was duration of treatment effect by patient-reported symptom return. Weibull proportional hazards regression models were fitted in a Bayesian framework to estimate missing times. Multivariable hazard regression analysis (hazard ratio, 95% credible intervals (HR, 95% CrI) compared repeated injections adjusting for differences in baseline symptom severity. Secondary outcomes included inter-injection interval, incontinence, urgency, and voiding episodes 6 weeks after injection. RESULTS: Four hundred and forty-two active injections were administered: 228 patients had one, 155 had two, and 59 had three injections. Time to symptom return for injection number 1 and 2 was 84 (95%CI: 63, 112) and 180 (95%CI: 135, 223) days, respectively. Median inter-injection intervals for receiving second and third injection were 266 days (range: 130, 1400) and 372 days (range: 134, 1283). No statistically significant differences in symptom outcomes or time to symptom return (HR 0.88, 95% CrI 0.37, 2.07 for injection 2, HR 0.33, 95% CrI 0.09, 1.03 for injection 3) were observed. CONCLUSIONS: Repeated onaBoNT-A injections have consistent efficacy and duration of action. There appears to be long-term placebo effects in both groups of randomized patients, with implications for open-label extension studies.

Enhancing Mn(II)-Binding and Manganese Peroxidase Activity in a Designed Cytochrome c Peroxidase through Fine-Tuning Secondary-Sphere Interactions.

Noncovalent second-shell interactions are important in controlling metal-binding affinity and activity in metalloenzymes, but fine-tuning these interactions in designed metalloenzymes has not been fully explored. As a result, most designed metalloenzymes have low metal-binding affinity and activity. Here we identified three mutations in the second coordination shell of an engineered Mn(II)-binding site in cytochrome c peroxidase (called MnCcP.1, containing Glu45, Glu37, and Glu181 ligands) that mimics the native manganese peroxidase (MnP), and explored their effects on both Mn(II)-binding affinity and MnP activity. First, removing a hydrogen bond to Glu45 through Tyr36Phe mutation enhanced Mn(II)-binding affinity, as evidenced by a 2.8-fold decrease in the KM of Mn(II) oxidation. Second, introducing a salt bridge through Lys179Arg mutation improved Glu35 and Glu181 coordination to Mn(II), decreasing KM 2.6-fold. Third, eliminating a steric clash that prevented Glu37 from orienting toward Mn(II) resulted in an 8.6-fold increase in kcat/KM, arising primarily from a 3.6-fold decrease in KM, with a KM value comparable to that of the native enzyme (0.28 mM vs 0.19 mM for Pleurotus eryngii MnP PS3). We further demonstrated that while the effects of Tyr36Phe and Lys179Arg mutations are additive, because involved in secondary-shell interactions to different ligands, other combinations of mutations were antagonistic because they act on different aspects of the Mn(II) coordination at the same residues. Finally, we showed that these MnCcP variants are functional models of MnP that mimic its activity in both Mn(II) oxidation and degradation of a phenolic lignin model compound and kraft lignin. In addition to achieving KM in a designed protein that is similar to the that of native enzyme, our results offer molecular insight into the role of noncovalent interactions around metal-binding sites for improving metal binding and overall activity; such insight can be applied to rationally enhance these properties in other metalloenzymes and their models.

Flexibility Coexists with Shape-Persistence in Cyanostar Macrocycles.

Shape-persistent macrocycles are attractive functional targets for synthesis, molecular recognition, and hierarchical self-assembly. Such macrocycles are noncollapsible and geometrically well-defined, and they are traditionally characterized by having repeat units and low conformational flexibility. Here, we find it necessary to refine these ideas in the face of highly flexible yet shape-persistent macrocycles. A molecule is shape-persistent if it has a small change in shape when perturbed by external stimuli (e.g., heat, light, and redox chemistry). In support of this idea, we provide the first examination of the relationships between a macrocycle's shape persistence, its conformational space, and the resulting functions. We do this with a star-shaped macrocycle called cyanostar that is flexible as well as being shape-persistent. We employed molecular dynamics (MD), density functional theory (DFT), and NMR experiments. Considering a thermal bath as a stimulus, we found a single macrocycle has 332 accessible conformers with olefins undergoing rapid interconversion by up-down and in-out motions on short time scales (0.2 ns). These many interconverting conformations classify single cyanostars as flexible. To determine and confirm that cyanostars are shape-persistent, we show that they have a high 87% shape similarity across these conformations. To further test the idea, we use the binding of diglyme to the single macrocycle as guest-induced stimulation. This guest has almost no effect on the conformational space. However, formation of a 2:1 sandwich complex involving two macrocycles enhances rigidity and dramatically shifts the conformer distribution toward perfect bowls. Overall, the present study expands the scope of shape-persistent macrocycles to include flexible macrocycles if, and only if, their conformers have similar shapes.

Stapled Peptides with γ-Methylated Hydrocarbon Chains for the Estrogen Receptor/Coactivator Interaction.

"Stapled" peptides are typically designed to replace two non-interacting residues with a constraining, olefinic staple. To mimic interacting leucine and isoleucine residues, we have created new amino acids that incorporate a methyl group in the γ-position of the stapling amino acid S5. We have incorporated them into a sequence derived from steroid receptor coactivator 2, which interacts with estrogen receptor α. The best peptide (IC50 =89 nm) replaces isoleucine 689 with an S-γ-methyl stapled amino acid, and has significantly higher affinity than unsubstituted peptides (390 and 760 nm). Through X-ray crystallography and molecular dynamics studies, we show that the conformation taken up by the S-γ-methyl peptide minimizes the syn-pentane interactions between the α- and γ-methyl groups.

Macromolecular Crystallography for Synthetic Abiological Molecules: Combining xMDFF and PHENIX for Structure Determination of Cyanostar Macrocycles.

Crystal structure determination has long provided insight into structure and bonding of small molecules. When those same small molecules are designed to come together in multimolecular assemblies, such as in coordination cages, supramolecular architectures and organic-based frameworks, their crystallographic characteristics closely resemble biological macromolecules. This resemblance suggests that biomacromolecular refinement approaches be used for structure determination of abiological molecular complexes that arise in an aggregate state. Following this suggestion we investigated the crystal structure of a pentagonal macrocycle, cyanostar, by means of biological structure analysis methods and compared results to traditional small molecule methods. Cyanostar presents difficulties seen in supramolecular crystallography including whole molecule disorder and highly flexible solvent molecules sitting in macrocyclic and intermolecule void spaces. We used the force-field assisted refinement method, molecular dynamics flexible fitting algorithm for X-ray crystallography (xMDFF), along with tools from the macromolecular structure determination suite PHENIX. We found that a standard implementation of PHENIX, namely one without xMDFF, either fails to produce a solution by molecular replacement alone or produces an inaccurate structure when using generic geometry restraints, even at a very high diffraction data resolution of 0.84 Å. The problems disappear when taking advantage of xMDFF, which applies an optimized force field to realign molecular models during phasing by providing accurate restraints. The structure determination for this model system shows excellent agreement with the small-molecule methods. Therefore, the joint xMDFF-PHENIX refinement protocol provides a new strategy that uses macromolecule methods for structure determination of small molecules and their assemblies.

Ligand Accessibility and Bioactivity of a Hormone-Dendrimer Conjugate Depend on pH and pH History.

Estrogen conjugates with a polyamidoamine (PAMAM) dendrimer have shown remarkably selective regulation of the nongenomic actions of estrogens in target cells. In response to pH changes, however, these estrogen-dendrimer conjugates (EDCs) display a major morphological transition that alters the accessibility of the estrogen ligands that compromises the bioactivity of the EDC. A sharp break in dynamic behavior near pH 7 occurs for three different ligands on the surface of a PAMAM-G6 dendrimer: a fluorophore (tetramethylrhodamine [TMR]) and two estrogens (17α-ethynylestradiol and diphenolic acid). Collisional quenching and time-resolved fluorescence anisotropy experiments with TMR-PAMAM revealed high ligand shielding above pH 7 and low shielding below pH 7. Furthermore, when the pH was cycled from 8.5 (conditions of ligand-PAMAM conjugation) to 4.5 (e.g., endosome/lysosome) and through 6.5 (e.g., hypoxic environment) back to pH 8.5, the 17α-ethynylestradiol- and diphenolic acid-PAMAM conjugates experienced a dramatic, irreversible loss in cell stimulatory activity; dynamic NMR studies indicated that the hormonal ligands had become occluded within the more hydrophobic core of the PAMAM dendrimer. Thus, the active state of these estrogen-dendrimer conjugates appears to be metastable. This pH-dependent irreversible masking of activity is of considerable relevance to the design of drug conjugates with amine-bearing PAMAM dendrimers.

Neural-Network Scoring Functions Identify Structurally Novel Estrogen-Receptor Ligands.

The magnitude of the investment required to bring a drug to the market hinders medical progress, requiring hundreds of millions of dollars and years of research and development. Any innovation that improves the efficiency of the drug-discovery process has the potential to accelerate the delivery of new treatments to countless patients in need. "Virtual screening," wherein molecules are first tested in silico in order to prioritize compounds for subsequent experimental testing, is one such innovation. Although the traditional scoring functions used in virtual screens have proven useful, improved accuracy requires novel approaches. In the current work, we use the estrogen receptor to demonstrate that neural networks are adept at identifying structurally novel small molecules that bind to a selected drug target, ultimately allowing experimentalists to test fewer compounds in the earliest stages of lead identification while obtaining higher hit rates. We describe 39 novel estrogen-receptor ligands identified in silico with experimentally determined Ki values ranging from 460 nM to 20 µM, presented here for the first time.

Rapid parameterization of small molecules using the Force Field Toolkit.

The inability to rapidly generate accurate and robust parameters for novel chemical matter continues to severely limit the application of molecular dynamics simulations to many biological systems of interest, especially in fields such as drug discovery. Although the release of generalized versions of common classical force fields, for example, General Amber Force Field and CHARMM General Force Field, have posited guidelines for parameterization of small molecules, many technical challenges remain that have hampered their wide-scale extension. The Force Field Toolkit (ffTK), described herein, minimizes common barriers to ligand parameterization through algorithm and method development, automation of tedious and error-prone tasks, and graphical user interface design. Distributed as a VMD plugin, ffTK facilitates the traversal of a clear and organized workflow resulting in a complete set of CHARMM-compatible parameters. A variety of tools are provided to generate quantum mechanical target data, setup multidimensional optimization routines, and analyze parameter performance. Parameters developed for a small test set of molecules using ffTK were comparable to existing CGenFF parameters in their ability to reproduce experimentally measured values for pure-solvent properties (<15% error from experiment) and free energy of solvation (±0.5 kcal/mol from experiment).

Analysis of the surgical learning curve using the cumulative sum (CUSUM) method.

AIMS: The concept of the "learning curve" is a term that has become increasingly prevalent in medical literature. Using a unique Female Urology fellowship program running over the last 3 years, we set out to better define the learning process for mid-urethral slings. METHODS: We examined surgical outcomes for six urology trainees who participated in the 6-month program from 2006 to 2011. We identified all retropubic mid-urethral sling procedures they had performed. Demographics included age, BMI, and smoking status. Outcomes focused on complication rates, as well as a subjective patient assessment. Analysis was by the cumulative sum method. RESULTS: Six trainees performed 187 retropubic slings during their fellowships. Mean age was 54 (SD ± 12.7), mean BMI was 29.5 (SD ± 5.5). One hundred sixty-five (88%) patients only underwent a mid-urethral tape with 22 (12%) undergoing a concomitant procedure. There were 5 cases of bladder perforation, 1 case of urethral injury, 25 cases of voiding dysfunction, and 8 cases of mesh exposure. One hundred sixty-seven out of 180 patients reported a cure or improvement. All complications occurred in the first 4 months of training. CUSUM analysis of voiding dysfunction showed that four out of six trainees did not reach the expected incidence of voiding dysfunction within the completed fellowship. Bladder perforation showed a similar trend. CONCLUSION: CUSUM analysis is an underused tool for the analysis of surgical competence. The learning curve for retropubic sling surgery is variable and may be longer than is often acknowledged. We suggest the focus of surgical training should move away from absolute numbers to look at training in an individualized manner.

Identification of Small Molecule Inhibitors and Ligand Directed Degraders of Calcium/Calmodulin Dependent Protein Kinase Kinase 1 and 2 (CaMKK1/2).

CaMKK2 signals through AMPK-dependent and AMPK-independent pathways to trigger cellular outputs including proliferation, differentiation, and migration, resulting in changes to metabolism, bone mass accrual, neuronal function, hematopoiesis, and immunity. CAMKK2 is upregulated in tumors including hepatocellular carcinoma, prostate, breast, and gastric cancer, and genetic deletion in myeloid cells results in increased antitumor immunity in several syngeneic models. Validation of the biological roles of CaMKK2 has relied on genetic deletion or small molecule inhibitors with activity against several biological targets. We sought to generate selective inhibitors and degraders to understand the biological impact of inhibiting catalytic activity and scaffolding and the potential therapeutic benefits of targeting CaMKK2. We report herein selective, ligand-efficient inhibitors and ligand-directed degraders of CaMKK2 that were used to probe immune and tumor intrinsic biology. These molecules provide two distinct strategies for ablating CaMKK2 signaling in vitro and in vivo.

1,25-Dihydroxyvitamin D3 acts directly on the T lymphocyte vitamin D receptor to inhibit experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) is an incurable autoimmune neurodegenerative disease. Environmental factors may be key to MS prevention and treatment. MS prevalence and severity decrease with increasing sunlight exposure and vitamin D(3) supplies, supporting our hypothesis that the sunlight-dependent hormone, 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2) D(3) ), inhibits autoimmune T-cell responses in MS. Moreover, 1,25-(OH)(2) D(3) inhibits and reverses experimental autoimmune encephalomyelitis (EAE), an MS model. Here, we investigated whether 1,25-(OH)(2) D(3) inhibits EAE via the vitamin D receptor (VDR) in T lymphocytes. Using bone marrow chimeric mice with a disrupted VDR only in radio-sensitive hematopoietic cells or radio-resistant non-hematopoietic cells, we found that hematopoietic cell VDR function was necessary for 1,25-(OH)(2) D(3) to inhibit EAE. Furthermore, conditional targeting experiments showed that VDR function in T cells was necessary. Neither 1,25-(OH)(2) D(3) nor T-cell-specific VDR targeting influenced CD4(+) Foxp3(+) T-cell proportions in the periphery or the CNS in these studies. These data support a model wherein 1,25-(OH)(2) D(3) acts directly on pathogenic CD4(+) T cells to inhibit EAE.

Randomized trial of tension-free vaginal tape and tension-free vaginal tape-obturator for urodynamic stress incontinence in women.

PURPOSE: We compared the efficacy and complications of tension-free vaginal tape and tension-free vaginal tape-obturator. MATERIALS AND METHODS: Women with pure urodynamic stress incontinence undergoing only primary continence surgery were randomized to tension-free vaginal tape or tension-free vaginal tape-obturator at 2 centers between March 2005 and March 2007. Primary outcome was objective cure rate at 6 months, defined by a 24-hour pad test of less than 5 gm. Secondary outcomes were the subjective cure rate on the Patient Global Impression of Improvement, quality of life on the King's Healthcare Questionnaire and symptom severity scores on the International Consultation on Incontinence Questionnaire. RESULTS: A total of 127 women were recruited. The study was stopped early due to excess leg pain in the tension-free vaginal tape-obturator group. Of the women 66 were randomized to tension-free vaginal tape and 61 were randomized to tension-free vaginal tape-obturator. Analysis was done by intent to treat. The objective and subjective cure rate at 6 months for tension-free vaginal tape vs tension-free vaginal tape-obturator was 69.7% vs 72.1% and 72.7% vs 67.2% (p = 0.76 and 0.49, respectively). Cure rates at 1 year were similar but loss to followup was high. Objective and subjective cure rates at 1 year for tension-free vaginal tape vs tension-free vaginal tape-obturator were 50% vs 41% and 53% vs 42.6% (p = 0.31 and 0.24, respectively). More women complained of leg pain after receiving a tension-free vaginal tape-obturator (26.4% vs 1.7%, p = 0.0001). The incidence of perioperative complications was low and similar between the groups. Time to discharge home and time to normal activity were not significantly different. CONCLUSIONS: Short-term cure rates at 6 months were similar. Tension-free vaginal tape-obturator caused more transient leg pain. Each procedure achieved a high cure rate and a low complication rate.

Clinicians' views on the feasibility of surgical randomized trials in urogynecology: results of a questionnaire survey.

AIMS: To survey the views of clinicians (urologists and gynecologists) about a proposed randomized surgical trial comparing two approaches for the treatment of women with urinary incontinence and vaginal prolapse. METHODS: A questionnaire survey nested within a pilot randomized controlled trial of colposuspension versus anterior repair plus TVT (CARPET1) for women with incontinence and anterior vaginal prolapse. Members of the UK Continence Society, British Society of Urogynaecology, and International Continence Society were sent a single electronic mailing of semi-structured questionnaires containing closed and open questions and free text response boxes. Free text responses were analyzed using a thematic qualitative analysis. RESULTS: One hundred fifty-seven questionnaires were returned, from a potential total of 400 from UK and 1,700 international respondents. Fifty-eight percent thought the trial ethical, 44% desirable, and 47% feasible. Thirty-three percent would recruit to the full study, and 22% would enroll themselves or their partner. Analysis of free text responses identified three themes impacting participation: issues of patient choice and consent; clinicians' views of perceived benefit and complications of the two arms; and issues about the chosen trial design. CONCLUSIONS: This study highlights the difference between collective and individual equipoise and their impact upon surgical trials. Clinicians held strong views preventing them from regarding the study favorably. Difficulty with relinquishing control over choice of procedure appeared central. These findings support the growing evidence in favor of detailed qualitative pilot work for surgical trials. The role of expertise-based randomization deserves further consideration.

Defining the Energetic Basis for a Conformational Switch Mediating Ligand-Independent Activation of Mutant Estrogen Receptors in Breast Cancer.

Although most primary estrogen receptor (ER)-positive breast cancers respond well to endocrine therapies, many relapse later as metastatic disease due to endocrine therapy resistance. Over one third of these are associated with mutations in the ligand-binding domain (LBD) that activate the receptor independent of ligand. We have used an array of advanced computational techniques rooted in molecular dynamics simulations, in concert with and validated by experiments, to characterize the molecular mechanisms by which specific acquired somatic point mutations give rise to ER constitutive activation. By comparing structural and energetic features of constitutively active mutants and ligand-bound forms of ER-LBD with unliganded wild-type (WT) ER, we characterize a spring force originating from strain in the Helix 11-12 loop of WT-ER, opposing folding of Helix 12 into the active conformation and keeping WT-ER off and disordered, with the ligand-binding pocket open for rapid ligand binding. We quantify ways in which this spring force is abrogated by activating mutations that latch (Y537S) or relax (D538G) the folded form of the loop, enabling formation of the active conformation without ligand binding. We also identify a new ligand-mediated hydrogen-bonding network that stabilizes the active, ligand-bound conformation of WT-ER LBD, and similarly stabilizes the active conformation of the ER mutants in the hormone-free state. IMPLICATIONS: Our investigations provide deep insight into the energetic basis for the structural mechanisms of receptor activation through mutation, exemplified here with ER in endocrine-resistant metastatic breast cancers, with potential application to other dysregulated receptor signaling due to driver mutations.