Static Retention Research Articles

Induction of Synaptic Plasticity in Flexible Organic Synaptic Transistors with Cross‐Linked Polymer Dielectric

AbstractControlled cross‐linking of polymer dielectric poly (4‐vinylphenol) (PVP) is demonstrated as an effective tool in enhancing the performance of flexible organic synaptic transistors (OSTs). Investigation of variation of concentration of the cross‐linking agent methylated poly (melamine‐co‐formaldehyde) (PMCF) in PVP in bilayer combination with high‐k hafnium oxide (HfO2) as gate dielectric in devices shows that the lower concentration of cross‐linking agent results in better memory performance. OSTs with 26% PMCF concentration in PVP (by mass) exhibit excellent memory performance with memory window > 4 V for VGS sweep of ±5 V, static retention of ≈104 s, dynamic retention for 500 cycles, and ≈125 continuous program/erase cycles. Pulse paired facilitation with relaxation time constants of 370 and 4670 ms respectively for slow and rapid phases with regulating modulation amplitude of ≈1 resemble a biological synapse. Through excitatory post synaptic current characteristics, spike timing dependant plasticity and spike voltage dependant plasticity are clearly observed, with low energy consumption per spike on the order of 10 pJ. Further, by leveraging the intricate interconnected data transfer and computation phenomenon, “AND” logic is effectively implemented using these OSTs. These exciting results may open up new directions toward the development of hardware for neuromorphic computing.

BART: A transferable liquid chromatography retention time library for bile acids

Identification of unknown bile acids, especially the distinguishment between isomers, requires retention times of a large number of reference standards, which are often not commercially available. Meanwhile, published retention information cannot be directly transferred across labs due to the differences between liquid chromatography (LC) systems, such as different extra column volume and dwell volume. To improve this situation, a transferrable retention time library for bile acids named BART was developed. BART was composed of isocratic retention models of 272 bile acids and a software tool to predict their gradient retention times on various LC systems. The isocratic retention times of bile acids were acquired on a Waters BEH C18 column with mobile phases of acidic ammonium acetate buffer and acetonitrile, and fit to the quadratic solvent strength model (QSSM). Segmented linear gradient retention times were calculated with holdup time (t0), dwell time (tD) and actual gradient profile corrected using 21 bile acid calibration standards. In addition to the reference system where the isocratic retention times were acquired, this approach has been validated on four other LC-MS systems in four labs with two gradient methods. Average root mean square errors (RMSE) between predicted and experimental retention times were 0.052 and 0.054 min for the two gradients tested, which were 9-fold more accurate than referring to a static retention time library. The library is freely available at https://bafinder.github.io/.

Development of Novel Nanodetectors in Drilling Fluids To Identify the Contribution of Different Producing Zones in Naturally Fractured Carbonate Reservoirs: From the Laboratory to Field-Level Implementation

The objective of this research was to develop and incorporate nanodetectors (NDs) in drilling fluids to identify the contribution of the different producing zones in naturally fractured carbonate reservoirs. The NDs were designed to interact with the crude oil and release the active compound that allows for fluorescence emission for surface detection. Novel nanocapsules based on carbon quantum dots (CQDs) were synthesized using various nanomaterials as the core and soy lecithin as the shell. Four CQDs were used: CQD green, CQD light blue, CQD red, and CQD dark blue. CQD red was discarded as a result of high retention in calcium carbonate, and encapsulation was performed with the others to form ND1, ND2, and ND4, respectively. The technology was assured through compatibility tests with reservoir fluids, static efficiency tests, and static retention. NDs had sizes smaller than 75 nm. Also, solubility tests showed that the active compound was released upon contact with oil-based systems. The characterization of the drilling fluids indicated that properties, such as the yield point and plastic viscosity, remained the same in the presence of the ND, which allows for its use under field conditions and secure wellbore stability. The technology was successfully implemented in a Colombian oil field. Filed results showed correlations between the gas profiles, brittleness of the zone, open fractures, and concentration of nanodetectors, which allows for the conclusion of the effectiveness of the nanostructures for the detection of naturally fractured zones of the evaluated wells.

CO2 transport and carbonate precipitation in the coupled diffusion-reaction process during CO2 storage

During geological CO2 storage and utilization, CO2 plume migration forms widespread static retention regions including the dead-end fractures and pores in the host rock, where the mass transfer is dominated by diffusion. A series of packed column experiments with natural olivine were conducted to investigate how the coupled CO2 diffusion–reaction process influences the CO2 transport and the temporal-spatial evolution of carbonate precipitation in diffusion-limited zones. The carbonate precipitations were mainly magnesite, and some dolomite due to the combined effect of carbonate precipitation kinetics and the low Ca content of the solution with Mg enrichment. Compared with the pure diffusion in porous media, the geochemical gradients in the pore solution resulting from the coupled diffusion–reaction interaction promoted mass transfer and broad migration, which led to an increase in effective diffusion coefficients of CO2 by approximately-one order of magnitude. The free water layer and pressure mode could affect the distribution of carbonate precipitation and the overall sequestration capacity. In particular, the coupled CO2 diffusion–reaction interaction under pressure decay mode could accelerate the carbonation in the deep region in the water-saturated column. This study advances the fundamental understanding on the transport and reaction of injected CO2 for mafic and ultramafic formations.

A 1‐GHz GC‐eDRAM in 7‐nm FinFET with static retention time at 700 mV for ultra‐low power on‐chip memory applications

AbstractConventional static random‐access memory (SRAM) suffers from high leakage power in advanced complementary metal‐oxide‐semiconductor nodes. Meanwhile, gain‐cell embedded dynamic random‐access memory (GC‐eDRAM) is an area‐efficient alternative to SRAM, although it requires periodic refresh cycles. In this regard, this study proposes a fin field‐effect transistor (FinFET)‐based 5T GC‐eDRAM bitcell that addresses the leakage power issue of SRAM while avoiding the bandwidth‐consuming refreshes of GC‐eDRAM. Furthermore, for the feasibility of scaling down transistors, the gain‐cell design is based on the FinFET, which overcomes short‐channel problems. The proposed 5T bitcell provides additional internal feedback relative to the 4T all‐nMOS fully depleted‐silicon on insulator (FD‐SOI) gain cell to ensure the static retention of both “1” and “0” data. The 2‐kB array was simulated by employing a 7‐nm FinFET predictive technology model (PTM) using HSPICE. The simulation results show that the proposed 5T bitcell (at 0.7 V) enables over 13× smaller data retention power and 10× area reduction compared to the 4T all‐nMOS GC‐eDRAM cell in a 28‐nm FD‐SOI technology.

Dynamic deuterium retention properties of tungsten measured using laser-induced breakdown spectroscopy

Dynamic deuterium (D) retention properties of tungsten (W) are investigated under steady-state D plasma exposure in the PISCES-A linear plasma device. In contrast to static retention, dynamic retention is quickly released from the material at the termination of the incident plasma flux, and thus in-operando laser-induced breakdown spectroscopy (LIBS) measurements have been conducted during steady-state D plasma exposure. A procedure is, first, established to extract the dynamic retention component from the in-operando LIBS D I 656.1 nm line intensity, which can contain contributions from dynamic and static retention as well as background D/D2 gas, excited by both steady-state and laser-induced plasmas. Using the developed procedure, the dynamic D retention in W is systematically examined while scanning the following plasma exposure parameters: incident ion energy, E i, sample temperature, T s, incident ion flux, Γi. No clear E i dependence is seen in the range of E i ∼ 45–175 eV, as expected from a small variation in the average implantation depth (∼3–6 nm) of D in W. The dynamic retention is found to monotonously decrease with increasing T s from 348 to 573 K, while the total static retention is reported to peak at T s ∼ 500–600 K. It is revealed that the dynamic retention linearly increases with increasing Γi, and then saturates at Γi ⩾ 0.75 × 1021 m−2 s−1. Possible physical mechanisms for the observed dependence of the dynamic retention on T s and Γi are discussed. Furthermore, sequential pure He, followed by pure D, plasma exposures show that the dynamic D retention is not strongly affected by He bubbles in the near-surface region.

A new approach for quantitative mapping of retention mechanisms of associative polymers in porous media

The retention of associative polymer molecules poses a significant challenge for its transport in porous media, and this arises due to the hydrophobic interactions that exists between the retained molecules. The known experimental approach in literature for quantifying polymer retention under static or dynamic conditions reports a generalized outcome without adequate estimates for each type of retention mechanisms. Thus, an accurate quantitative description of the various retention mechanisms (monolayer adsorption, multilayer adsorption and entrapment) attributable to associative polymers is crucial for proper optimization of its transport in porous media. In this work, a novel predictive approach was developed for quantitative mapping of the various retention mechanisms connected with associative polymers. The basis was a first-principles method adopted in mapping static to dynamic retention. This novel approach was achieved by relating the characteristic time scale for static and dynamic retention to the variation in polymer and reservoir properties, thus making it possible to correlate static retention results to large-scale dynamic retention with minimal fitting parameters. Furthermore, the mapping of the static to dynamic retention ensured an accurate quantification of the different retention mechanisms attributable to associative polymers. In this model, the in-situ entrapment was linked to the effective pore radius and the hydrodynamic size of the polymer molecules. Entrapment of polymer molecular aggregates was predicted based on the assumption that this occurs when the hydrodynamic size of the molecules becomes equal/greater than the effective pore size in the porous media. In addition, a threshold concentration value was estimated from which mechanical entrapment of polymer molecules would occur in a porous media alongside adsorption on pore surface. Similarly, a concentration value was estimated at which entrapment of polymer molecules becomes the dominant retention mechanism in the porous media.

Effect of Buffer Layer Capacitance on the Electrical Characteristics of Ferroelectric Polymer Capacitors and Field Effect Transistors.

We demonstrated the effect of a buffer layer on the electrical characteristics of ferroelectric polymer capacitors and field-effect transistors. Various polymer materials with a dielectric constant between 2 and 42 were used to form buffer layers with a similar thicknesses, but with different capacitances. In order to evaluate the characteristics of the ferroelectrics with a buffer layer, the polarization–voltage characteristics of the capacitor, the transfer characteristics, and the retention characteristics of the transistors were investigated. As the capacitance of the buffer layer increased, high remnant polarization (Pr), high hysteresis, and long retention times were observed. Exceptionally, when poly(methylmethacrylate) and rigid poly(aryl ether) (poly(9,9-bis(4-hydroxyphenyl)fluorene-co-decafluorobiphenyl)) were used as the buffer layer, Pr had a value close to 0 in the dynamic measurement polarization–voltage (P–V) characteristic, but the quasi-static measurement transfer characteristic and the static measurement retention characteristic showed relatively high hysteresis and long retention times. Our study provides a scientific and technical basis for the design of ferroelectric memory and neuromorphic devices.

Heterotypic endosomal fusion as an initial trigger for insulin-induced glucose transporter 4 (GLUT4) translocation in skeletal muscle.

Comprehensive imaging analyses of glucose transporter 4 (GLUT4) behaviour in mouse skeletal muscle was conducted. Quantum dot-based single molecule nanometry revealed that GLUT4 molecules in skeletal myofibres are governed by regulatory systems involving 'static retention' and 'stimulus-dependent liberation'. Vital imaging analyses and super-resolution microscopy-based morphometry demonstrated that insulin liberates the GLUT4 molecule from its static state by triggering acute heterotypic endomembrane fusion arising from the very small GLUT4-containing vesicles in skeletal myofibres. Prior exposure to exercise-mimetic stimuli potentiated this insulin-responsive endomembrane fusion event involving GLUT4-containing vesicles, suggesting that this endomembranous regulation process is a potential site related to the effects of exercise. Skeletal muscle is the major systemic glucose disposal site. Both insulin and exercise facilitate translocation of the glucose transporter glucose transporter 4 (GLUT4) via distinct signalling pathways and exercise also enhances insulin sensitivity. However, the trafficking mechanisms controlling GLUT4 mobilization in skeletal muscle remain poorly understood as a resuly of technical limitations. In the present study, which employs various imaging techniques on isolated skeletal myofibres, we show that one of the initial triggers of insulin-induced GLUT4 translocation is heterotypic endomembrane fusion arising from very small static GLUT4-containing vesicles with a subset of transferrin receptor-containing endosomes. Importantly, pretreatment with exercise-mimetic stimuli potentiated the susceptibility to insulin responsiveness, as indicated by these acute endomembranous activities. We also found that AS160 exhibited stripe-like localization close to sarcomeric α-actinin and that insulin induced a reduction of the stripe-like localization accompanying changes in its detergent solubility. The results of the present study thus provide a conceptual framework indicating that GLUT4 protein trafficking via heterotypic fusion is a critical feature of GLUT4 translocation in skeletal muscles and also suggest that the efficacy of the endomembranous fusion process in response to insulin is involved in the benefits of exercise.

Correlation between static random access memory power-up state and transistor variation

The correlation between the static random access memory (SRAM) power-up state (i.e., state 0 or 1 immediately after the power supply is turned on) and cell transistor variation is systematically studied by circuit simulations and mismatch space partitioning. It is revealed that, while both the mismatches of pFETs (pull-up) and nFETs (pull-down and access) contribute, their relative importance changes depending on the voltage ramping speed. The static retention noise margin well correlates with the power-up state only if the ramping speed is sufficiently low. Otherwise, pull-up transistor mismatch dominates the power-up state determination owing to the interference of capacitive current and asymmetrical capacitive coupling of the storage nodes to the ground and power supply.

Is Polymer Retention Different Under Anaerobic vs. Aerobic Conditions?

Summary This paper examines whether retention of partially hydrolyzed polyacrylamide (HPAM) is different under anaerobic vs. aerobic conditions. Both static (mixing with loose sand) and dynamic methods (corefloods) were used to determine HPAM retention. There are both advantages and disadvantages associated with determining polymer retention with static tests vs. dynamic tests and with aerobic vs. anaerobic conditions. From static-retention measurements, polymer-adsorption values on pure silica sand or Berea sandstone were small, and they showed little difference between experiments conducted aerobically or anaerobically. For both aerobic and anaerobic conditions, HPAM retention increased significantly with increased pyrite or siderite content. Static retention under anaerobic conditions ranged from 45 to 75 µg/g with 1% of either pyrite or siderite to 137–174 µg/g for 10% pyrite or siderite to 1161–1249 µg/g for 100% pyrite or siderite. If iron minerals are present, the most representative polymer-retention results are obtained (for both static and dynamic tests) if conditions are anaerobic. Retention values (from static measurements) under aerobic conditions were commonly twice those determined under anaerobic conditions. If iron minerals are present and retention tests are performed under aerobic conditions, total organic carbon (TOC) or some similar method should be used for polymer detection. Viscosity detection of polymer may provide retention values that are too high (because oxidative degradation can be misinterpreted as polymer retention). For a broad range of siderite content, retention from static tests did not depend on whether dissolved oxygen was present. However, for a broad range of pyrite content, HPAM retention was significantly lower in the absence of dissolved oxygen than under aerobic conditions. These results may be tied to iron solubility. When polymer solutions were mixed with 100% pyrite over the course of 12 hours, 360–480 ppm of iron dissolved into polymer solutions under both aerobic and anaerobic conditions, whereas with 100% siderite, only 0.0–0.6 ppm of iron dissolved. If dynamic methods (i.e., corefloods) are used to determine polymer retention under aerobic conditions, flow rates should be representative of the field application. Rates that are too high lead to underestimation of polymer retention. With 10% pyrite, dynamic retention was 211 µg/g at 6 ft/D vs. 43.2 µg/g at 30 ft/D. In contrast, retention values were fairly consistent (40.6–47.8 µg/g) between 6 and 33 ft/D under anaerobic conditions.

Lean Hospital; The Kanban System at Kemang Medical Care; An Improvement Approach for Reducing Lost Customer of Delivery Birth

Introduction – Kanban system is a card system that becomes markers. During its development, the kanban system experiences a number of variations. In the context of delivery system in hospital, delivery pack can be considered as a kanban. Delivery packs have complete data of patient information. They serve to monitor pregnant women in labor, childbirth, and the implementation of exclusive breastfeeding. By looking at the delivery packs, the doctor or midwife can determine the condition of mothers who give birth. Each card is stored in a pack in accordance with the estimated labor. This way, the doctor, midwife and mother can know the condition of pregnancy from time to time, including the danger signs of pregnancy and the risk of complications. the study sought to examine the performance of the delivery packs in customer retention in RSIA Kemang/Kemang Medical Care. Method – Researchers examined data on the number of patients maternity (SC and normal deliveries) in accordance with the estimated delivery using document analysis and report of medical record and audit results of kanban (delivery packs). The research sample was acquired in 6 (six) months from January to June 2015. The analysis was done by descriptive analytical design.Result – This study shows that the highest number of patients who gave birth happened in June 2015. In that month, there were 105 births, 19 of them did not have delivery packs. Even so, there were 96 patients who had delivery packs. It means that there are 10 patients with obstructed labor that did not have delivery records in the KMC. The evidence by the percentage of retention failures that goes up and down in the range of 6%-17%. There is failed retention as much as 11% every month. It means that in year 2015 and probably the year 2016, there are approximately 11% of patients KMC who do not want to give birth at the hospital, despite having the complete data of delivery packs.Discussion – The reasons which cause static retention may vary. They do not have to because of the low quality of services at KMC. They can be caused by KMC location which is far away from the patient when the patient is about to give birth. Indeed, KMC still have to improve the quality of service because if the consumer retention is seen as an indicator of quality of service. Conclusion - The use of delivery packs as a measuring tool of consumer retention shows the alternative benefits of kanban on hospital quality management system. This article gives examples of its use in hospitals KMC in Jakarta.

High-performance a MoS2 nanosheet-based nonvolatile memory transistor with a ferroelectric polymer and graphene source-drain electrode

Two-dimensional (2D) van der Waals (vdWs) materials are a class of new materials due to their unique physical properties. Of the many 2D vdWs materials, molybdenum disulfide (MoS2) is a representative n-type transition-metal dichalcogenide (TMD) semiconductor. Here, we report on a high-performance MoS2 nanosheet-based nonvolatile memory transistor with a poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric top gate insulator. In order to enhance the ohmic contact property, we use graphene flakes as source/drain electrodes prepared by using the direct imprinting method with an elastomer stamp. The MoS2 ferroelectric field-effect transistor (FeFET) shows the highest linear electron mobility value of 175 cm2/Vs with a high on/off current ratio of more than 107, and a very clear memory window of more than 15 V. The program and erase dynamics and the static retention properties are also well demonstrated.

Dynamical concentration and static retention of deuterium in tungsten foil studied by low energy D(d,p)T reaction and elastic recoil detection

The deposition behavior of hydrogen isotopes in tungsten is essential in fusion material research. A tungsten (W) foil was pre-implanted by deuterium ions (D3+) with an energy of 20keV/D and flux of 3.0×1014D/(cm2s) at room temperature until saturation state was confirmed by the proton yield of D(d,p)T reaction. The changes of D-concentration in surface layer have been obtained by D–D reaction analysis with low flux (0.6μA) and high energy (75keV) D+ beam at several storage time after the implantation terminated. Furthermore, the static D-retention in this sample was also measured by elastic recoil detection analysis one year later. The saturated value of nD/nW in surface layer of W foil is (42±3) at.% at fluence of 1.5×1018D/cm2. After beam stopped, the D-concentration decreased, and a static D-retention of about 3at.% was found one year later. These results showed that more than 92% of deuterium precipitated in tungsten metal at saturated state was unstable.

Influence of drainage system maintenance on storm runoff from a reforested, waterlogged mountain catchment

The maintenance of a drainage system in a waterlogged mountain catchment impacted by earlier harvesting operations was assessed on the basis of a hydrological analysis (hydrological balance, three linear reservoirs method). To restore pre-harvest hydrological conditions, the water-saturated localities were experimentally drained both by restoration of existing ditches and digging of additional open ditches. The rainwater retention of the soil was illustrated by two comparable storm flow events occurring before and after the draining treatment. Pedohydrological analysis revealed the important involvement of static retention in capillary pores in the rainfall-runoff process during rainstorm events. Restoration and addition of the drainage system yield more favourable generation and better proportioned distribution of storm flow discharge. There would be no danger of water depletion in the catchment during dry periods in connection with the draining treatment. In comparison with the state before drainage system maintenance, the static retention after draining treatment became greater than zero. Both the dynamic retention (detention) and static retention helped balancing storm flows in terms of flood and drought control. The successive drop of the raised water table level following drainage system maintenance resulted in changes of actual retention and subsequent runoff. The drainage procedure proved its positive influence on reforestation and the environment, as no negative impact on soil and stream hydrology was found.

Influence of Landscape Retention Capacity Upon Flood Processes in Jičínka River Basin

In a survey of landscape retention capability results of measurements obtained during the disastrous flood in June 2009 were used. The original method based on the balance among the daily precipitation fallen on the basin with discharges in the final profile was used on the analogy with transformation of the flood discharge through a reservoir. Following basin retention are defined: dynamic Rd, static Rs including the underground retention Rug and evaporation E, and total Rt. Main principal criteria were the effective static retention of the basin Rsef and a coefficient of the effective static basin retention ρsef (3). The coefficient of reducing flood culmination λcul (4) was calculated, too. Also investigated factors having the most influence on a retention capacity of a basin are introduced. Summary of results are shown in the Tab. I. Values of the most important criterion quantities are marked in shadow colour. The results show, for example, that the found out coefficient ρsef is 0.52. It means that the soil (and slightly a vapour, too) in the basin caught 52% of volume of wave in the time of culmination discharge in a basin. Also some further interested findings are introduced in the results and conclusions.

A New Method for Measuring the Soil-Water Retention Curve of Red Clay

Red clay is normally used in the area of Guangxi for roadbed filling and slope overburden. The engineering properties of red clay are closely related with the hydraulic characteristics. A new rapid method is adopted for measuring the soil-water retention curve of the red clay based on the dynamic multi-step outflow tests. The static soil-water retention curve is obtained through the non-equilibrium changes of soil-water under each step of matric suction. Compared with the traditional measured methods, the new method can save much time for determining the hydraulic characteristic functions, especially for clay soils. Several experiments are done under different suction steps and load time on the same red clay sample for verifying the effectiveness of the new rapid method. The experimental results show that the static soil-water data are largely dependent on the initial several suction steps and load time in the dynamic multi-step outflow tests. If the suitable loading scheme is adopted in the dynamic multi-step outflow method, the time can be saved greatly for obtaining the soil-water characteristic curve and hydraulic conductivity function of red clay. The significance of the rapid method will great for the engineering design and evaluation related with unsaturated red clay.

Novel Field Effect Diode Type Vertical Capacitorless One Transistor Dynamic Random Access Memory Cell with Negative Hold Bit Line Bias Scheme for Improving the Hold Characteristics

In this paper, the novel field effect diode (FED) type vertical capacitorless one transistor dynamic random access memory (1T-DRAM) cell with negative hold bit line (BL) voltage (VBL) scheme is proposed. In comparison with the conventional planar type, the proposed vertical type with negative hold VBL scheme shows excellent static and disturb retention time. The proposed vertical type memory cell with negative hold VBL scheme achieves 1,000 times longer static retention time and 104 times longer BL disturb retention time at 85 °C than that of the conventional planar type. Furthermore, the proposed vertical type memory cell has a small cell size of 4F2 due to its stacked vertical structure. The proposed FED type vertical capacitorless 1T-DRAM cell with negative hold VBL scheme is shown to be an excellent candidate for stand-alone and embedded memory applications and extends scaling limitations.

Molecular Basis of Insulin‐Responsive GLUT4 Trafficking Systems Revealed by Single Molecule Imaging

Development of a 'static retention' property of GLUT4, the insulin-responsive glucose transporter, has emerged as being essential for achieving its maximal insulin-induced surface exposure. Herein, employing quantum-dot-based nanometrology of intracellular GLUT4 behavior, we reveal the molecular basis of its systematization endowed upon adipogenic differentiation of 3T3L1 cells. Specifically, (i) the endosomes-to-trans-Golgi network (TGN) retrieval system specialized for GLUT4 develops in response to sortilin expression, which requires an intricately balanced interplay among retromers, golgin-97 and syntaxin-6, the housekeeping vesicle trafficking machinery. (ii) The Golgin-97-localizing subdomain of the differentiated TGN apparently serves as an intermediate transit route by which GLUT4 can further proceed to the stationary GLUT4 storage compartment. (iii) AS160/Tbc1d4 then renders the 'static retention' property insulin responsive, i.e. insulin liberates GLUT4 from the static state only in the presence of functional AS160/Tbc1d4. (iv) Moreover, sortilin malfunction and the resulting GLUT4 sorting defects along with retarded TGN function might be etiologically related to insulin resistance. Together, these observations provide a conceptual framework for understanding maturation/retardation of the insulin-responsive GLUT4 trafficking system that relies on the specialized subdomain of differentiated TGN.

Static retention of the lumenal monotopic membrane protein torsinA in the endoplasmic reticulum

TorsinA is a membrane-associated enzyme in the endoplasmic reticulum (ER) lumen that is mutated in DYT1 dystonia. How it remains in the ER has been unclear. We report that a hydrophobic N-terminal domain (NTD) directs static retention of torsinA within the ER by excluding it from ER exit sites, as has been previously reported for short transmembrane domains (TMDs). We show that despite the NTD's physicochemical similarity to TMDs, it does not traverse the membrane, defining torsinA as a lumenal monotopic membrane protein and requiring a new paradigm to explain retention. ER retention and membrane association are perturbed by a subset of nonconservative mutations to the NTD, suggesting that a helical structure with defined orientation in the membrane is required. TorsinA preferentially enriches in ER sheets, as might be expected for a lumenal monotopic membrane protein. We propose that the principle of membrane-based protein sorting extends to monotopic membrane proteins, and identify other proteins including the monotopic lumenal enzyme cyclooxygenase 1 (prostaglandin H synthase 1) that share this mechanism of retention with torsinA.