ER-SURF: Riding the Endoplasmic Reticulum Surface to Mitochondria

Most mitochondrial proteins are synthesized in the cytosol and targeted to the mitochondrial surface in a post-translational manner. The surface of the endoplasmic reticulum (ER) plays an active role in this targeting reaction. ER-associated chaperones interact with certain mitochondrial membrane protein precursors and transfer them onto receptor proteins of the mitochondrial surface in a process termed ER-SURF. ATP-driven proteins in the membranes of mitochondria (Msp1, ATAD1) and the ER (Spf1, P5A-ATPase) serve as extractors for the removal of mislocalized proteins. If the re-routing to mitochondria fails, precursors can be degraded by ER or mitochondria-associated degradation (ERAD or MAD respectively) in a proteasome-mediated reaction. This review summarizes the current knowledge about the cooperation of the ER and mitochondria in the targeting and quality control of mitochondrial precursor proteins.

Numerical study on hydrodynamic forces and course stability of a ship in surf-riding condition based on PMM tests

The theoretical method, or named the potential flow method, is most widely used in the research of maneuvering in waves. However, this approach used in previous studies is based on the assumption that maneuvering hydrodynamic derivatives in waves are the same as those in calm water. However, this assumption can be inaccurate, which makes the simulations inexact sometimes. Meanwhile, there are few experiments performed to investigate the hydrodynamic derivatives in waves considering the complexities of the experimental setup and data processing. There is even no systematic numerical simulation in this field. Considering the importance of the wave effect on the hydrodynamic derivatives and the advantages of the CFD method, in this study, the numerical simulations of the PMM tests on a containership S175 in regular waves are performed for the first time. The hydrodynamic derivatives in waves are obtained by simulations in the following waves, to be specific, the surf-riding condition. The surf-riding condition is chosen for separating the wave-induced component easily and researching the reason for the broaching-to phenomenon. The simulation results are validated by experimental data with satisfactory accuracy, which indicates the effectiveness of the numerical setup. The results reveal that the wave has a significant effect on hydrodynamic derivatives. The detailed changing trends and simulation methods of all hydrodynamic derivatives are proposed in this paper. Moreover, the course stability in waves is evaluated by the hydrodynamic derivatives in waves, which verifies the reason for the occurrence of the broaching-to phenomenon.

Surf-Riding Operational Measures for Fast Semidisplacement Naval Hull Form

Surf-riding/broaching failure mode is one of the Second Generation Intact Stability Criteria (SGISC) dealt by IMO. The SGISC are structured with a multi-tiered approach: Level 1, Level 2 and Direct Stability Assessment (DSA). When a ship does not verify one level, the next once must be applied, or the ship design must be modified. If ship changes are not feasible, Operational Measures (OM) can be provided to avoid dangerous situations and reduce the likelihood of stability failures. The OM are divided into Operational Limitations (OL) related to areas or routes and related to maximum significant wave heights and Operational Guidance (OG). The surf-riding criterion has been applied on the parent hull of the Systematic Series D, a fast semi-displacement naval hull with forms typically vulnerable to surf-riding phenomenon. The 90 m length ship results vulnerable to Level 1 and 2, therefore Operational Measures have been discussed and provided for a hypothetical route in the Mediterranean Sea (Area 26). Following the OL, in considered Area 26 the ship operations are limited when significant wave heights exceed 3.8 m. The simplified OG define critical ship speeds to be avoided for each considered sea state.