Reconstitution of bacterial cytokinesis: the Z-ring

Prokaryotic cell division is one of the most fundamental processes in biology, but the dynamics and mechanics are far from being understood. In many bacteria, FtsZ, a tubulin homologue assembles into a ring-like structure – Z-ring at precisely the middle of the cell. This accurate site selection is dependent on the Min proteins. Min D and MinE self-organise into waves in vitro, and oscillate pole to pole in vivo. MinC is thought to couple the Min oscillations to FtsZ by direct interaction. The mechanism of inhibitory action of MinC on FtsZ assembly is not known. Critical to the understanding of regulation of FtsZ by MinC and other proteins and its probable role in force generation is the organisation, structure and the dynamics of the Z-ring. Current models of the FtsZ filament organization in the Z-ring argue between two different structures – (i) short overlapping protofilaments with lateral interactions and (ii) few long annealed protofilaments with or without lateral contacts. Our observations of the characteristics of polymerization and turnover studies using fluorescence microscopy suggest that the FtsZ filament is a continuous and irresolute bundle. The results are consistent with a structure where the turnover happens throughout, and any specialised structure resulting in a GTP cap like structure can be ruled out. We show that the turnover rates and hydrolysis rates are similar arguing for a model in which subunit leaves as soon as it hydrolyses GTP. On the basis of crystal structures, we cloned the N-terminal of FtsZ, which acts as a C-terminal end capping fragment and is able to interact with monomers. The end-capping fragment, NZ can disassemble the FtsZ polymers, without influencing the GTPase activity, offering a comparable standard for the activity of MinC. On the basis of our observations, we propose a model on how MinC can disassemble FtsZ polymers. Furthermore, our data shows that the Min CDE system is sufficient to cause spatial regulation of FtsZ provided FtsZ is dynamic. How the Z-ring takes the form of a functional helical or ring-like structure remains unclear. Extensive modelling approaches have tried to explain the ring formation and force generation. Previous studies have qualitatively shown bending of liposome membranes by FtsZ filaments. We hypothesised that the presumably intrinsically curved filaments should respond to pre-curved substrates, and the alignment should be quantifiable. This should ascertain whether or not FtsZ has intrinsic curvature and/or actively induces any force. Thus, we investigated how FtsZ filaments respond to a range of curvatures, which mimic different stages of the division process. Our results show that the FtsZ filaments possess intrinsic curvatures as well as spontaneous twist. This facilitates the formation of Z-ring by utilizing geometrical cues. Our results are in agreement with consistent helical FtsZ polymers observed in vivo by Cryo-EM or super resolution microscopy. The alignment of filaments over a range of curvature suggests that the filaments have considerable flexibility, which strongly suggests reconsidering possible mechanisms of force generation. Moreover, the developed assay constitutes a valuable platform to further study proteins involved in modifying curvature of FtsZ filaments. In summary, by reconstituting the FtsZ filament in vitro, we have elucidated the nature of FtsZ filaments. The dynamics of FtsZ filaments allows them to be inhibited by MinC, thus cooperating with the Min waves. The presence of intrinsic curvature and twist facilitates their formation into a ring necessary for the cell to carry out cytokinesis

Reconstitution of bacterial cytokinesis: the Z-ring

Prokaryotic cell division is one of the most fundamental processes in biology, but the dynamics and mechanics are far from being understood. In many bacteria, FtsZ, a tubulin homologue assembles into a ring-like structure – Z-ring at precisely the middle of the cell. This accurate site selection is dependent on the Min proteins. Min D and MinE self-organise into waves in vitro, and oscillate pole to pole in vivo. MinC is thought to couple the Min oscillations to FtsZ by direct interaction. The mechanism of inhibitory action of MinC on FtsZ assembly is not known. Critical to the understanding of regulation of FtsZ by MinC and other proteins and its probable role in force generation is the organisation, structure and the dynamics of the Z-ring. Current models of the FtsZ filament organization in the Z-ring argue between two different structures – (i) short overlapping protofilaments with lateral interactions and (ii) few long annealed protofilaments with or without lateral contacts. Our observations of the characteristics of polymerization and turnover studies using fluorescence microscopy suggest that the FtsZ filament is a continuous and irresolute bundle. The results are consistent with a structure where the turnover happens throughout, and any specialised structure resulting in a GTP cap like structure can be ruled out. We show that the turnover rates and hydrolysis rates are similar arguing for a model in which subunit leaves as soon as it hydrolyses GTP. On the basis of crystal structures, we cloned the N-terminal of FtsZ, which acts as a C-terminal end capping fragment and is able to interact with monomers. The end-capping fragment, NZ can disassemble the FtsZ polymers, without influencing the GTPase activity, offering a comparable standard for the activity of MinC. On the basis of our observations, we propose a model on how MinC can disassemble FtsZ polymers. Furthermore, our data shows that the Min CDE system is sufficient to cause spatial regulation of FtsZ provided FtsZ is dynamic. How the Z-ring takes the form of a functional helical or ring-like structure remains unclear. Extensive modelling approaches have tried to explain the ring formation and force generation. Previous studies have qualitatively shown bending of liposome membranes by FtsZ filaments. We hypothesised that the presumably intrinsically curved filaments should respond to pre-curved substrates, and the alignment should be quantifiable. This should ascertain whether or not FtsZ has intrinsic curvature and/or actively induces any force. Thus, we investigated how FtsZ filaments respond to a range of curvatures, which mimic different stages of the division process. Our results show that the FtsZ filaments possess intrinsic curvatures as well as spontaneous twist. This facilitates the formation of Z-ring by utilizing geometrical cues. Our results are in agreement with consistent helical FtsZ polymers observed in vivo by Cryo-EM or super resolution microscopy. The alignment of filaments over a range of curvature suggests that the filaments have considerable flexibility, which strongly suggests reconsidering possible mechanisms of force generation. Moreover, the developed assay constitutes a valuable platform to further study proteins involved in modifying curvature of FtsZ filaments. In summary, by reconstituting the FtsZ filament in vitro, we have elucidated the nature of FtsZ filaments. The dynamics of FtsZ filaments allows them to be inhibited by MinC, thus cooperating with the Min waves. The presence of intrinsic curvature and twist facilitates their formation into a ring necessary for the cell to carry out cytokinesis

Ureteral endometriosis following panhysterectomy a case report

Ureteral endometriosis is a rare form of endometriotic lesion. It can be intrinsic or extrinsic, intrinsic being more rare than extrinsic. Extrinsic ureteral involvement can lead to silent damage to the kidneys. It is commonly seen in women with rectovaginal endometriosis. They present with a variety of symptoms from flank pain to hematuria. Though it responds to medical management, it will require definitive surgical intervention such as a simple cyst excision to the extent of ureteric resection and reanastamosis

A concise enantioselective synthesis of (R)-(+)-goniothalamin oxide, a trypanocidal active agent via L-prolinol catalyzed asymmetric epoxidation of cinnamaldehyde

393-398A short and straight-forward enantioselective synthesis of (R)-(+)-goniothalamin oxide 2 has been achieved with an overall yield of 39% and 99% ee. The synthetic approach involves l-prolinol catalyzed asymmetric epoxidation of cinnamaldehyde followed by Lewis acid-mediated diastereoselective allylation of epoxy aldehyde as the key chiral-inducing steps

Particle Swarm Optimization with Various Inertia Weight Variants for Optimal Power Flow Solution

This paper proposes an efficient method to solve the optimal power flow problem in power systems using Particle Swarm Optimization (PSO). The objective of the proposed method is to find the steady-state operating point which minimizes the fuel cost, while maintaining an acceptable system performance in terms of limits on generator power, line flow, and voltage. Three different inertia weights, a constant inertia weight (CIW), a time-varying inertia weight (TVIW), and global-local best inertia weight (GLbestIW), are considered with the particle swarm optimization algorithm to analyze the impact of inertia weight on the performance of PSO algorithm. The PSO algorithm is simulated for each of the method individually. It is observed that the PSO algorithm with the proposed inertia weight yields better results, both in terms of optimal solution and faster convergence. The proposed method has been tested on the standard IEEE 30 bus test system to prove its efficacy. The algorithm is computationally faster, in terms of the number of load flows executed, and provides better results than other heuristic techniques

Construction of Heteroatom-Doped Porous Carbon Architectures for Energy and Sensing Applications

In this chapter, we have concentrated on the main electrocatalytic oxygen processes, oxygen reduction reaction (ORR) and water splitting oxygen evolution reaction (OER), and biosensors based on porous carbon architectures, which are more important areas of research because of the rise in demand for energy management, supply, and disease diagnosis. Heteroatom-doped carbon hollow spheres are very useful because they have a large surface area, mesoporosity, spherical wall thicknesses, edge plane defect sites, catalytic active sites, and fast heterogeneous electron-transfer rates. These properties are very important for making commercial devices. This chapter provides an overview of hollow carbon nanospheres that are doped with single and double heteroatoms, as well as cobalt oxide. These carbon compounds function as dual catalysts for OER and ORR, as well as an effective electrocatalyst for the oxygen reduction process in both acidic and alkaline media. Electrocatalytically, heteroatom-doped carbon sphere-modified electrodes can simultaneously and specifically identify and determine the analytes, while also validating the target species in real samples. N-doped hollow carbon spheres coated-Co3O4 functioned as an efficient dual-function oxygen electrocatalyst for oxygen evolution and oxygen reduction processes and also as a biosensor for highly effective electrochemical sensing of acetaminophen. A symmetric supercapacitor using dual heteroatom-doped and SBA-15 templated porous carbon was also discussed

Preparation of 3D spherical Ni/Al LDHs with significantly enhanced electrochemical performance as a superior cathode material for Ni/MH batteries.

Nickel-based hydroxides with excellent electrochemical performance have been considered as cathode materials for Ni/MH batteries. In this paper, a Ni/Al layered double hydroxides (Ni/Al LDHs) material with three-dimensional (3D) spherical structure is synthesized by a facile stable dual complexation-precipitation method. SEM images show that the obtained Ni/Al LDHs possess 3D spherical structure composed of nanosheets. XRD and CV tests indicate that doping of Al increases the distance between Ni-Al layers, greatly improving the specific capacity of the obtained materials. The electrochemical tests show that the specific capacity of the obtained material with 18% Al is up to 383.4 mAh g-1 at a current density of 1 A g-1. In addition, when the current density is further increased to 10 and 20 A g-1, the specific capacity of this material still maintains 345.0 mAh g-1 and 307.9 mAh g-1, respectively, which implies that this cathode material can provide remarkable power densities. Moreover, the material composed of Ni/Al LDHs keeps 97.6% initial capacity after 5000 cycles at a current density of 10 A g-1, showing an excellent cycling stability and durability

A Retrospective Study of Cochlear Re-Implantations - Experience from a Large Centre in India

Objective: Cochlear re-implantation (CRI) is becoming increasingly common throughout the world. However, studies regarding CRI incidence and etiology are lacking from developing countries like ours. The aim of this study was to present the Indian experience with CRI based on our experience. Objectives were to determine the incidence and the indications of CRI and the cumulative survival rate (CSR) of cochlear implantation (CI).Methods: Our study was a retrospective one, conducted at a tertiary care centre in southern India. 1,500 consecutive cochlear implanted ears from 1997 to 2016 were studied. All patients who underwent CRI during this period were included in the study.Results: There were a total of 53 ears (31 male and 22 female ears) who underwent CRI. This gives an incidence of 3.53%. The most common indication of CRI was device failure in 39 ears contributing to 73.6% of the total CRI. The overall CSR of CI in pediatric population was 96.5% over a 20-year period.Conclusion:The CRI incidence and etiology at our centre appears to reflect the findings of the literature. Cochlear implant centres across the world should report the CSR of devices used at their respective centres so that it can be made an important criterion in choice of implant