Lipid droplet functions beyond energy storage.

Dynein and its cofactor dynactin form a highly processive microtubule motor in the presence of an activating adaptor, such as BICD2. Different adaptors link dynein and dynactin to distinct cargoes. Here we use electron microscopy and single-molecule studies to show that adaptors can recruit a second dynein to dynactin. Whereas BICD2 is biased towards recruiting a single dynein, the adaptors BICDR1 and HOOK3 predominantly recruit two dyneins. We find that the shift towards a double dynein complex increases both the force and speed of the microtubule motor. Our 3.5 A resolution cryo-electron microscopy reconstruction of a dynein tail–dynactin–BICDR1 complex reveals how dynactin can act as a scaffold to coordinate two dyneins side-by-side. Our work provides a structural basis for understanding how diverse adaptors recruit different numbers of dyneins and regulate the motile properties of the dynein–dynactin transport machine. Cryo-electron microscopy and single-molecule studies reveal that the adaptors BICDR1 and HOOK3 recruit two dynein molecules to dynactin and thereby increase the force and speed of the dynein–dynactin microtubule motor. In eukaryotic cells, the cytoplasmic protein dynein-1 (dynein) is the main transporter of cargoes towards the minus ends of microtubules—tube-like components of the cytoskeleton that, together with motor proteins, move material within the cell. Dynein is converted into a highly processive motor protein through binding both to its cofactor dynactin and to a cargo adaptor, such as BICD2, BICDR1 or HOOK3. BICD2 preferentially binds to one molecule of dynein and one molecule of dynactin. Using cryo-electron microscopy Andrew Carter and team show that, in contrast, BICDR1 and HOOK3 bind to a complex of two dyneins, which are brought together by a dynactin scaffold. The authors' single-molecule studies highlight that this configuration increases both the force and speed of the motor complex.

/pdf/cryo-em-shows-how-dynactin-recruits-two-dyneins-for-faster-skmhzmmu3w.pdf

Cryo-EM shows how dynactin recruits two dyneins for faster movement.

Lysosome trafficking and signaling in health and neurodegenerative diseases.

Dynein Clusters into Lipid Microdomains on Phagosomes to Drive Rapid Transport toward Lysosomes.

Autophagy is the main homeostatic pathway guiding cytosolic materials for degradation by the lysosome. Maturation of autophagosomes requires their transport towards the perinuclear region of the cell, with key factors underlying both processes still poorly understood. Here we show that transport and positioning of late autophagosomes depends on cholesterol by way of the cholesterol-sensing Rab7 effector ORP1L. ORP1L localizes to late autophagosomes and-under low-cholesterol conditions-contacts the ER protein VAP-A, forming ER-autophagosome contact sites, which prevent minus-end transport by the Rab7-RILP-dynein complex. ORP1L-mediated contact sites also inhibit localization of PLEKHM1 to Rab7. PLEKHM1, together with RILP, then recruits the homotypic fusion and vacuole protein-sorting (HOPS) complex for fusion of autophagosomes with late endosomes and lysosomes. Thus, ORP1L, via its liganding by lipids and the formation of contacts between autophagic vacuoles and the ER, governs the last steps in autophagy that lead to the lysosomal degradation of cytosolic material.

/pdf/cholesterol-and-orp1l-mediated-er-contact-sites-control-4cxew6iq3u.pdf

Cholesterol and ORP1L-mediated ER contact sites control autophagosome transport and fusion with the endocytic pathway

The effect of reduction in the terminal voltage of a grid-tied inverter together with minimization in total harmonic distortion (THD) of terminal voltage and current, in the presence of dead-band in the switching remains always challenging for the researchers. With high switching frequency, this issue increases by many folds. The grid-tied inverter used for harmonic compensation acts as a shunt active power filter (SAPF). The implementation of the dead-band elimination technique is based on output current polarity detection, suffers from multiple zero-crossing due to the generation of high frequency switching harmonics during SAPF operation. This paper deals with a dead band elimination methodology together with harmonic compensation using SAPF under non-linear and unbalanced loading conditions. Here, SAPF uses a dual fundamental component extraction (DFCE) scheme with modified complex coefficient filter (MCCF) to extract fundamental components for reference current generation to implement an indirect current control PWM scheme. MCCF extracts fundamental components even in the presence of dc offset and unbalancing at the input. For incorporating dead-band elimination in control, exact polarity detection is done separately through SAPF output current estimation using sensed load current, and modified CCF computed reference source current. Since the estimated SAPF output current contains no high-frequency switching harmonics, the dead-band elimination technique can be correctly implemented. To synchronize the zero-crossing of the estimated and actual SAPF current, an adaptive delay control is used. The proposed MCCF based control logic’s performance together with the dead-band elimination technique is validated for SAPF operating under non-linear, unbalance, and dynamic load conditions. The proposed dead-band elimination scheme based SAPF model is developed and simulated using MATLAB/ SIMULINK. The simulation results show a significant reduction in source current harmonics due to the elimination of odd harmonic injection into the system by incorporating dead-band elimination in SAPF operation. The real-time simulation of the proposed method is also validated using OPAL-RT OP4510 real-time platform.

Modified CCF Based Shunt Active Power Filter Operation With Dead-Band Elimination for Effective Harmonic and Unbalance Compensation in 3-Phase 3-Wire System

Microtubule (MT)-based motor proteins transport many cellular factors to their functionally relevant locations within cells, and defects in transport are linked to human disease. Understanding the mechanism and regulation of this transport process in living cells is difficult because of the complex in vivo environment and limited means to manipulate the system. On the other hand, in vitro motility assays using purified motors attached to beads does not recapitulate the full complexity of cargo transport in vivo. Assaying motility of organelles in cell extracts is therefore attractive, as natural cargoes are being examined, but in an environment that is more amenable to manipulation. Here, we describe the purification and in vitro MT-based motility of phagosomes from Dictyostelium and lipid droplets from rat liver. These assays have the potential to address diverse questions related to endosome/phagosome maturation, fatty acid regulation, and could also serve as a starting point for reconstituting the motility of other types of organelles.

Reconstitution of microtubule-dependent organelle transport.

The presence of non-linear load majorly affects the power quality in the system. The most common non-linear loading observed is the rectifier load. Across the rectifier, the load can be current fed (series R-L) and voltage fed (parallel R-C). With the series R-L load, current harmonics can be compensated with a conventional shunt active power filter. Current harmonics compensation with rectifier-connected parallel RC load is complicated using conventional shunt active power filter. To solve this issue, shunt active power filter is operated with dual fundamental component extraction (DFCE) scheme, where filtering is performed using reduced order generalized integrator (ROGI) and a choke is added at the point of the common coupling side with the load. The SAPF performance is simulated using MATLAB2020a platform, under current and voltage fed non-linear loading conditions for the shake of comparative analysis. 

Comparative Analysis of ROGI based Shunt Active Power Filter under Current Fed and Voltage Fed Type Non-Linear Loading Condition

Power generation with photovoltaic technology is growing expeditiously. With the high penetration of solar-based generation, a concern of islanding detection is always by the distributors due to grid side faults and abnormality. It is the demand of the situation to equip the PV-connected inverter with an islanding detection mechanism to avoid any catastrophe. In the present work, an active islanding detection technique utilizing a smaller magnitude current injection through <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> -axis current controller of grid side voltage source converter (VSC) is proposed. Due to injection of current through VSC, point of common coupling (PCC) voltage is having different harmonic component in the grid connected and islanded mode. In the proposed detection method, the sensed PCC voltage is used to derive the three signals i.e. AVVM(absolute <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$v_{mag}$</tex-math></inline-formula> variation mean), AMSVV(absolute mean of square variation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$v_{mag}$</tex-math></inline-formula> ), & FAVVM(Frequency of absolute <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$v_{mag}$</tex-math></inline-formula> variation mean). These three derived signals is used to take the decision for islanding detection. Further, Complex Co-efficient Filter-Second Order Frequency Locked Loop (CCF-SOFLL) is proposed for three phase grid synchronization and frequency estimation. The proposed Strategy is tested under high impedance fault, phase failure and unbalanced loading conditions. It is found that the proposed work clearly differentiates the islanding and faults condition. The Non- detection zone (NDZ) of the proposed strategy is verified under different quality factors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q_{f}$</tex-math></inline-formula> ) of the load. To evaluate the effectiveness of the suggested strategy, MATLAB Simulation and experimental validation is performed. The obtained islanding detection time is within the IEEE-1547 standard. 

Robust Adaptive Active Islanding Detection With $\alpha$- Axis Disturbance Injection Under High Impedance Fault, Unbalanced Loading & Phase Failure in Grid Tied PV System

Alok Kumar Dubey

Papers

Dynein Clusters into Lipid Microdomains on Phagosomes to Drive Rapid Transport toward Lysosomes.

Modified CCF Based Shunt Active Power Filter Operation With Dead-Band Elimination for Effective Harmonic and Unbalance Compensation in 3-Phase 3-Wire System

Reconstitution of microtubule-dependent organelle transport.

Comparative Analysis of ROGI based Shunt Active Power Filter under Current Fed and Voltage Fed Type Non-Linear Loading Condition

Robust Adaptive Active Islanding Detection With $\alpha$- Axis Disturbance Injection Under High Impedance Fault, Unbalanced Loading & Phase Failure in Grid Tied PV System