A computational study of the substrate conversion and selective inhibition of aldosterone synthase

When a functional or structural impairment of cardiac output has occurred, the cardiovascular system will attempt to compensate for the reduced blood flow. Unfortunately, many of the resulting processes, such as the renin angiotensin aldosterone system, will progressively weaken the heart, resulting in the condition called heart failure. The renin angiotensin aldosterone regulatory system is currently targeted with medicine for heart failure. Many successes for the prolongation of patient age have been achieved by inhibition of angiotensin II synthesis and action. It has become apparent that this approach is suboptimal. Antagonists of aldosterone have provided better treatment options, however, side-effects are still observed. In the search for an alternative therapeutic application, we have studied a novel treatment involving the selective inhibition of aldosterone biosynthesis. The scope of this study has involved the in silico design and prediction of novel inhibitors, the synthesis of these inhibitors and analogues, and finally the in vitro measurement of their potency. The biosynthesis of aldosterone is performed by two cytochrome p450 enzymes, 11B1 and 11B2, denoted as CYP11B1 and CYP11B2, respectively. From these two family members, only CYP11B2 can perform the final synthesis step that converts 18-hydroxycorticosterone into aldosterone. CYP11B1 performs the synthesis of glucocorticoids that are responsible for metabolic, immunologic and homeostatic functions. Because these glucocorticoid actions should not be inhibited, the newly designed medicine must be CYP11B2 selective. Since CYP11B1 is highly homologous to CYP11B2, we have performed an in silico study that allows us to model the interactions of substrates and inhibitors in both the active sites of CYP11B1 and CYP11B2. Using comparative modelling, we have constructed models for the three dimensional architecture of both proteins. These models have been validated by investigating the torsional properties of the protein backbone and residue side chains, the overall protein packing and the dynamic behaviour of the protein models. Subsequently, the models have been used to evaluate the binding mechanisms and conversion mechanisms for the natural steroidal ligands of CYP11B1 and CYP11B2. A hypothetical binding mode has been proposed for 18-hydroxycorticosterone in CYP11B2, featuring the presence of stabilising hydrogen bonding interactions required for its conversion. Quantum mechanical analyses on the conversion of the steroids involved have shown a favourable conversion for this conformation, thereby supporting our hypothesis. In addition, the quantum mechanical analyses have provided insights on steroid conformations in the active sites during conversion. The suitability of the protein models for inhibitor design has been tested by subjecting the models to a case study with four known inhibitors of CYP11B1 and CYP11B2. Using molecular dynamics and molecular docking, the inhibitor potencies for CYP11B1 and CYP11B2 have been predicted, and their interactions with the proteins have been evaluated. The trends in inhibitor potency found by these computational methods have been confirmed by in vitro inhibition measurements. As a next step, the molecular docking study has been expanded to improve the confidence in the predictive power of the models. Using the protein states evaluated by the molecular dynamics study, the molecular docking results of inhibitor analogues have been investigated and the predictive power of the models has been qualitatively improved. In a final approach, we have performed a ligand-based investigation of the inhibitor analogues to determine which ligand characteristics are important for the potency for CYP11B1 and CYP11B2. To this end, we have conducted decision tree analyses on the physico-chemical properties of inhibitor substituents, resulting in a collection of descriptors that can be used for the prediction and design of novel inhibitors. We have shown that a combination of synthesis, molecular modelling and experimental measurements form a promising approach towards the design of potentially new inhibitors

Graphical Evolution of Spin Network States

The evolution of spin network states in loop quantum gravity can be described by introducing a time variable, defined by the surfaces of constant value of an auxiliary scalar field. We regulate the Hamiltonian, generating such an evolution, and evaluate its action both on edges and on vertices of the spin network states. The analytical computations are carried out completely to yield a finite, diffeomorphism invariant result. We use techniques from the recoupling theory of colored graphs with trivalent vertices to evaluate the graphical part of the Hamiltonian action. We show that the action on edges is equivalent to a diffeomorphism transformation, while the action on vertices adds new edges and re-routes the loops through the vertices.Comment: 24 pages, 21 PostScript figures, uses epsfig.sty, Minor corrections in the final formula in the main body of the paper and in the formula for the Tetrahedral net in the Appendi

Microstructural development during the quenching and partitioning process in a newly designed low-carbon steel

This paper presents a detailed characterization of the microstructural development of a new quenching and partitioning (Q&P) steel. Q&P treatments, starting from full austenitization, were applied to the developed steel, leading to microstructures containing volume fractions of retained austenite of up to 0.15. The austenite was distributed as films in between the martensite laths. Analysis demonstrates that, in this material, stabilization of austenite can be achieved at significantly shorter time scales via the Q&P route than is possible via a bainitic isothermal holding. The results showed that the thermal stabilization of austenite during the partitioning step is not necessarily accompanied by a significant expansion of the material. This implies that the process of carbon partitioning from martensite to austenite occurs across low-mobility martensite–austenite interfaces. The amount of martensite formed during the first quench has been quantified. Unlike martensite formed in the final quench, this martensite was found to be tempered during partitioning. Measured volume fractions of retained austenite after different treatments were compared with simulations using model descriptions for carbon partitioning from martensite to austenite. Simulation results confirmed that the carbon partitioning takes place at low-mobility martensite–austenite interfaces.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.OLD Metals Processing, Microstructures and PropertiesOLD Surface and Interface Engineerin

Regularization of the Hamiltonian constraint and the closure of the constraint algebra

In the paper we discuss the process of regularization of the Hamiltonian constraint in the Ashtekar approach to quantizing gravity. We show in detail the calculation of the action of the regulated Hamiltonian constraint on Wilson loops. An important issue considered in the paper is the closure of the constraint algebra. The main result we obtain is that the Poisson bracket between the regulated Hamiltonian constraint and the Diffeomorphism constraint is equal to a sum of regulated Hamiltonian constraints with appropriately redefined regulating functions.Comment: 23 pages, epsfig.st

A Comparison of the Ovulation Method With the CUE Ovulation Predictor in Determining the Fertile Period

The purpose of this study was to compare the CUE Ovulation Predictor with the ovulation method in determining the fertile period. Eleven regularly ovulating women measured their salivary and vaginal electrical resistance (ER) with the CUE, observed their cervical-vaginal mucus, and measured their urine for a luteinizing hormone (LH) surge on a daily basis. Data from 21 menstrual cycles showed no statistical difference (T= 0.33, p= 0.63) between the CUE fertile period, which ranged from 5 to 10 days (mean = 6.7 days, SD = 1.6), and the fertile period of the ovulation method, which ranged from 4 to 9 days (mean = 6.5 days, SD = 2.0). The CUE has potential as an adjunctive device in the learning and use of natural family planning methods

Case report: Use of granulocyte-colony stimulating factor as an immunomodulatory therapy in a patient with neuromyelitis optica spectrum disorder and comorbid immunodeficiency

BackgroundAutoimmune diseases can coexist with immunodeficiency. We describe a treatment approach in which granulocyte-colony stimulating factor (G-CSF) is used to restore immune competence without worsening autoimmunity. G-CSF is a polyfunctional cytokine that influences survival, proliferation, and differentiation of hematopoietic stem cells, and has immunomodulatory effects on the innate and adaptive immune systems.ObjectiveTo report a case of neuromyelitis optica spectrum disorder (NMOSD) with comorbid immunodeficiency and frequent infections.MethodsCase report and review of literature.ResultsA 23 years-old man presented with a focal onset seizure with impaired awareness at age 12. At age 18, he developed headaches, recurrent multifocal seizures, and non-convulsive status epilepticus. Brain magnetic resonance imaging (MRI) showed extensive T2 hyperintense and gadolinium-enhancing periventricular and corpus callosum lesions. Serum aquaporin 4 antibody was positive 1:10,000 (normal value <1.5 titer), hence he was diagnosed with NMOSD. As a complication, patient developed mucormycotic pneumonia with cavitation, requiring thoracotomy precluding use of immunosuppressants. Gene testing demonstrated a mutation in MT-ND4 gene encoding for NADH dehydrogenase 4 in mitochondrial complex 1. Eventually, he began a treatment with filgrastim, a G-CSF analog, in addition to intravenous immunoglobulins and prednisone. Patient’s NMOSD has been in remission without relapses, or coexistent infections ever since.ConclusionG-CSF is a polyfunctional cytokine with important immunomodulatory effects, which makes it an interesting therapeutic option when autoimmunity coexists with immunodeficiency and was used successfully in this case

Linear Contraction Behavior of Low-Carbon, Low-Alloy Steels During and After Solidification Using Real-Time Measurements

A technique for measuring the linear contraction during and after solidification of low-alloy steel was developed and used for examination of two commercial low-carbon and low-alloy steel grades. The effects of several experimental parameters on the contraction were studied. The solidification contraction behavior was described using the concept of rigidity in a solidifying alloy, evolution of the solid fraction, and the microstructure development during solidification. A correlation between the linear contraction properties in the solidification range and the hot crack susceptibility was proposed and used for the estimation of hot cracking susceptibility for two studied alloys and verified with the real casting practice. The technique allows estimation of the contraction coefficient of commercial steels in a wide range of temperatures and could be helpful for computer simulation and process optimization during continuous casting. © 2013 The Minerals, Metals & Materials Society and ASM International