Straits in the Russian Arctic

The issues surrounding the regimes of international straits, noninternational straits, and ice-covered areas are analyzed for the purpose of looking at Russian practices in its Arctic straits. It is concluded that the Russian practice exceeds that permitted to states bordering straits under the traditional regime for straits. Nevertheless, viewing the U.S. practice as a coastal state, as well as the coastal state practice of Canada, substantial similarities are found with the Russian practice. Conflicting claims and practices result in a confused Arctic legal regime. An international conference is recommended to discuss and perhaps settle the issues.     

UNCLOS III and conflict management in straits

Abstract

The legal regime articulated for international straits in the United Nations Convention of 1982 is a significant milestone in the reconciliation of competing interests attendant upon navigation in international straits. However, the author also submits that the refinement of respective rights and obligations of states in international straits can only be harmonized through the process of claim and counterclaim, a slow and somewhat tedious process. Extremely difficult, yet highly important questions deserve thoughtful analysis in the context of the 1982 Convention's territorial sea and straits provisions.     

Transit rights and U.S. security interests in international straits: The “straits debate”; revisited

Abstract

The issue of transit rights through international straits overlapped by an extension of territorial seas to 12nm was the focal point of intense debate between the United States and straits states during the formative stages of UNCLOS III. Even though the ICNT provisions on transit through straits reflect basic U.S. navigation and security interests, this paper argues that the issue of transit rights through straits is not a dead issue. Straits states may either refuse to ratify a LOS treaty incorporating ICNT provisions on transit passage, or the attempts to obtain a comprehensive LOS treaty may end in failure. In either case, the United States may be forced to accept a right of innocent passage through international straits. The conclusions of this paper are that the security of transit will be determined by political rather than legal considerations, and that U.S. security interests in straits are not undermined by a right of innocent passage.     

Transit Passage and Pollution Control in Straits under the 1982 Law of the Sea Convention

This contribution examines and points out the inadequacy of the provisions of Part III of the 1982 Law of the Sea (LOS) Convention to combat marine pollution in straits used for international navigation without infringing the right to transit passage of all user states. It stresses that it is the environmental obligation of all user and strait states to protect the marine environment of straits used for international navigation. To this end, this paper proposes that Part III of the 1982 LOS Convention be reconsidered and a "Guarantee of Freedom of Navigation--Environmental Impact Statement" be adopted by user and strait states.     

Enhancing Safety,Security, and Environmental Protection of the Straits of Malacca and Singapore: The Cooperative Mechanism

In November 2004, the International Maritime Organization, as part of its Protection of Vital Shipping Lanes Initiative, decided to convene a high-level conference to address the security of ships plying the Straits of Malacca and Singapore in collaboration with the three littoral states of Indonesia, Malaysia, and Singapore. Three meetings were held over the period 2005 to 2007. The outcome was the creation of a framework for cooperation between the users of the straits and the littoral states known as the Cooperative Mechanism, a historic breakthrough as Article 43 of the Law of the Sea Convention was implemented for the first time. This article outlines the decisions made at the three meetings, analyzes the responses of the various stakeholders during the meetings, explains the reasons for the success of the Cooperative Mechanism, and concludes by proposing ways in which the momentum of cooperation between the users and the littoral states could be sustained.     

The politics of Caribbean Straits

Abstract

For a variety of reasons the Caribbean basin has emerged as a particularly volatile region of the Third World with many potential sources of conflict. The expansion of some local navies and intensified competition between the Soviet Union and the United States further complicate a conflict‐prone situation. Many weak states with token navies, including most Caribbean straits states, are highly unstable, being vulnerable both to domestic strife and to international rivalry.

Superpower strategies toward Caribbean straits states have nonetheless remained fairly restrained, although U.S.‐U.S.S.R. competition in this area is intensifying. For example, the Reagan Administration has identified and reacted to alleged global implications of a Soviet bloc threat to Caribbean straits and sea lanes. It will not be easy to wind down this rhetoric, but evidence to the contrary may dissipate public anxiety and lead to cooperative measures to assist in the emergence of a more stable and mutually acceptable regional order, including the Caribbean straits. Constructive cooperation between Caribbean basin states, including their naval and maritime affairs, also could be increasingly important for limiting politicization and militarization of straits.     

Free energy calculations shed light on the nuclear pore complex’s selective barrier nature

The nuclear pore complex (NPC) is the exclusive gateway for traffic control across the nuclear envelope. Although smaller cargoes (less than 5–9 nm in size) can freely diffuse through the NPC, the passage of larger cargoes is restricted to those accompanied by nuclear transport receptors (NTRs). This selective barrier nature of the NPC is putatively associated with the intrinsically disordered, phenylalanine-glycine repeat-domains containing nucleoporins, termed FG-Nups. The precise mechanism underlying how FG-Nups carry out such an exquisite task at high throughputs has, however, remained elusive and the subject of various hypotheses. From the thermodynamics perspective, free energy analysis can be a way to determine cargo’s transportability because the traffic through the NPC must be in the direction of reducing the free energy. In this study, we developed a computational model to evaluate the free energy composed of the conformational entropy of FG-Nups and the energetic gain associated with binding interactions between FG-Nups and NTRs and investigated whether these physical features can be the basis of NPC’s selectivity. Our results showed that the reduction in conformational entropy by inserting a cargo into the NPC increased the free energy by an amount substantially greater than the thermal energy (≫k_BT), whereas the free energy change was negligible (<k_BT) for small cargoes (less than ~6 nm in size), indicating the size-dependent selectivity emerges from the entropic effect. Our models suggested that the entropy-induced selectivity of the NPC depends sensitively upon the physical parameters such as the flexibility and the length of FG-Nups. On the other hand, the energetic gain via binding interactions effectively counteracted the entropic reduction, increasing the size limit of transportable cargoes up to the nuclear pore size. We further investigated the geometric effect of the binding spot spatial distribution and found that the clustered binding spot distribution decreased the free energy more efficiently as compared to the scattered distribution.     

Free energy calculations shed light on the nuclear pore complex’s selective barrier nature

The nuclear pore complex (NPC) is the exclusive gateway for traffic control across the nuclear envelope. Although smaller cargoes (less than 5–9 nm in size) can freely diffuse through the NPC, the passage of larger cargoes is restricted to those accompanied by nuclear transport receptors (NTRs). This selective barrier nature of the NPC is putatively associated with the intrinsically disordered, phenylalanine-glycine repeat-domains containing nucleoporins, termed FG-Nups. The precise mechanism underlying how FG-Nups carry out such an exquisite task at high throughputs has, however, remained elusive and the subject of various hypotheses. From the thermodynamics perspective, free energy analysis can be a way to determine cargo’s transportability because the traffic through the NPC must be in the direction of reducing the free energy. In this study, we developed a computational model to evaluate the free energy composed of the conformational entropy of FG-Nups and the energetic gain associated with binding interactions between FG-Nups and NTRs and investigated whether these physical features can be the basis of NPC’s selectivity. Our results showed that the reduction in conformational entropy by inserting a cargo into the NPC increased the free energy by an amount substantially greater than the thermal energy (≫k_BT), whereas the free energy change was negligible (<k_BT) for small cargoes (less than ~6 nm in size), indicating the size-dependent selectivity emerges from the entropic effect. Our models suggested that the entropy-induced selectivity of the NPC depends sensitively upon the physical parameters such as the flexibility and the length of FG-Nups. On the other hand, the energetic gain via binding interactions effectively counteracted the entropic reduction, increasing the size limit of transportable cargoes up to the nuclear pore size. We further investigated the geometric effect of the binding spot spatial distribution and found that the clustered binding spot distribution decreased the free energy more efficiently as compared to the scattered distribution.     

The International Tribunal for the Law of the Sea on Maritime Delimitation: The Bangladesh v. Myanmar Case

This article uses the Northwest Passage as a case for study of one issue relating to the regime of international straits: whether a strait formed geographically and functionally by means of artificial aids for navigation may be regarded as an artificial waterway to which the regime of international straits does not apply. The article suggests that the Northwest Passage could be subject to a bilateral treaty regime between Canada and the United States, largely akin to that which applies to artificial waterways such as the Panama Canal. This solution would guarantee both Canadian sovereignty over the Passage and the interests of international shipping in having a route open and secure.     

International Straits and Trans-Arctic Navigation

The Arctic Ocean is increasingly becoming accessible to international shipping as a result of the reduction in Arctic sea ice. Commercial shipping may seek to transit the Arctic Ocean from either the Pacific or Atlantic Ocean and, as a result, the legal regime of straits has significance for trans-Arctic navigation. In this article, current developments in Arctic shipping are assessed and consideration is given to certain Arctic straits that could prove to be pivotal in future Arctic navigation and shipping. These straits include the Bering Strait, Nares Strait, Davis Strait, Fram Strait, and Denmark Strait.     

Identification of Cargo Proteins Specific for Importin-β with Importin-α Applying a Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC)-based in Vitro Transport System

The human importin (Imp)-β family consists of 21 nucleocytoplasmic transport carrier proteins, which transport thousands of proteins (cargoes) across the nuclear envelope through nuclear pores in specific directions. To understand the nucleocytoplasmic transport in a physiological context, the specificity of cargoes for their cognate carriers should be determined; however, only a limited number of nuclear proteins have been linked to specific carriers. To address this biological question, we recently developed a novel method to identify carrier-specific cargoes. This method includes the following three steps: (i) the cells are labeled by stable isotope labeling by amino acids in cell culture (SILAC); (ii) the labeled cells are permeabilized, and proteins in the unlabeled cell extracts are transported into the nuclei of the permeabilized cells by a particular carrier; and (iii) the proteins in the nuclei are quantitatively identified by LC-MS/MS. The effectiveness of this method was demonstrated by the identification of transportin (Trn)-specific cargoes. Here, we applied this method to identify cargo proteins specific for Imp-β, which is a predominant carrier that exclusively utilizes Imp-α as an adapter for cargo binding. We identified candidate cargoes, which included previously reported and potentially novel Imp-β cargoes. In in vitro binding assays, most of the candidate cargoes bound to Imp-β in one of three binding modes: directly, via Imp-α, or via other cargoes. Thus, our method is effective for identifying a variety of Imp-β cargoes. The identified Imp-β and Trn cargoes were compared, ensuring the carrier specificity of the method and illustrating the complexity of these transport pathways.     

Energetics of Transport through the Nuclear Pore Complex

Molecular transport across the nuclear envelope in eukaryotic cells is solely controlled by the nuclear pore complex (NPC). The NPC provides two types of nucleocytoplasmic transport: passive diffusion of small molecules and active chaperon-mediated translocation of large molecules. It has been shown that the interaction between intrinsically disordered proteins that line the central channel of the NPC and the transporting cargoes is the determining factor, but the exact mechanism of transport is yet unknown. Here, we use coarse-grained molecular dynamics simulations to quantify the energy barrier that has to be overcome for molecules to pass through the NPC. We focus on two aspects of transport. First, the passive transport of model cargo molecules with different sizes is studied and the size selectivity feature of the NPC is investigated. Our results show that the transport probability of cargoes is significantly reduced when they are larger than ∼5 nm in diameter. Secondly, we show that incorporating hydrophobic binding spots on the surface of the cargo effectively decreases the energy barrier of the pore. Finally, a simple transport model is proposed which characterizes the energy barrier of the NPC as a function of diameter and hydrophobicity of the transporting particles.     

The importin β binding domain as a master regulator of nucleocytoplasmic transport

Specific and efficient recognition of import cargoes is essential to ensure nucleocytoplasmic transport. To this end, the prototypical karyopherin importin β associates with import cargoes directly or, more commonly, through import adaptors, such as importin α and snurportin. Adaptor proteins bind the nuclear localization sequence (NLS) of import cargoes while recruiting importin β via an N-terminal importin β binding (IBB) domain. The use of adaptors greatly expands and amplifies the repertoire of cellular cargoes that importin β can efficiently import into the cell nucleus and allows for fine regulation of nuclear import. Accordingly, the IBB domain is a dedicated NLS, unique to adaptor proteins that functions as a molecular liaison between importin β and import cargoes. This review provides an overview of the molecular role played by the IBB domain in orchestrating nucleocytoplasmic transport. Recent work has determined that the IBB domain has specialized functions at every step of the import and export pathway. Unexpectedly, this stretch of ~ 40 amino acids plays an essential role in regulating processes such as formation of the import complex, docking and translocation through the nuclear pore complex (NPC), release of import cargoes into the cell nucleus and finally recycling of import adaptors and importin β into the cytoplasm. Thus, the IBB domain is a master regulator of nucleocytoplasmic transport, whose complex molecular function is only recently beginning to emerge. This article is part of a Special Issue entitled: Regulation of Signaling and Cellular Fate through Modulation of Nuclear Protein Import.     

Nucleocytoplasmic transport of proteins

In eukaryotic cells, the movement of macromolecules between the nucleus and cytoplasm occurs through the nuclear pore complex (NPC)--a large protein complex spanning the nuclear envelope. The nuclear transport of proteins is usually mediated by a family of transport receptors known as karyopherins. Karyopherins bind to their cargoes via recognition of nuclear localization signal (NLS) for nuclear import or nuclear export signal (NES) for export to form a transport complex. Its transport through NPC is facilitated by transient interactions between the karyopherins and NPC components. The interactions of karyopherins with their cargoes are regulated by GTPase Ran. In the current review, we describe the NPC structure, NLS, and NES, as well as the model of classic Ran-dependent transport, with special emphasis on existing alternative mechanisms; we also propose a classification of the basic mechanisms of protein transport regulation.     

The Legal Regime Governing Sea Transport of Ultrahazardous Radioactive Materials

Although the international community has taken some steps to address the risks created by the movements of ultrahazardous radioactive cargoes, important gaps still exist in the legal regime governing these activities. An apparent consensus has been reached at the International Maritime Organization (IMO) to make the Code for the Safe Carriage of Irradiated Nuclear Fuel, Plutonium, and High-Level Radioactive Wastes in Flasks Aboard Ships (the INF Code) mandatory and to seek some clarification of the standards governing shipboard safety. But still lacking are agreements regarding salvage responsibilities, liability of shippers for damages, revision of transport cask safety standards to meet maritime accident conditions, obligations to consult regarding the best routes and to provide advance notification to concerned coastal states, the preparation of environmental assessments, and contingency planning to handle shore emergencies and salvage responsibilities. Until agreements are reached on these important matters, the shipment of these extremely dangerous or "ultrahazardous" materials will continue to violate fundamental norms of international law and comity because they place coastal nations that receive no benefit from the shipments at grave risk of environmental disaster without any legal protections. Because the shipments of ultrahazardous radioactive cargoes are increasing, it is highly advisable for concerned nations to negotiate regional protocols delineating the legal regime that applies to these maritime transports. A draft model protocol is attached at the end of this article which may provide guidance on this effort. It is also appropriate for concerned nations to consider bringing a claim against the shipping nations under the dispute resolution mechanisms established by the 1982 United Nations Law of the Sea Convention. Such a claim would be based on the failure of the shipping nations to comply with their obligations under the convention to prepare and distribute environmental impact assessments, consult with affected nations, prepare emergency contingency plans, and agree to an effective liability regime in the event of an accident. Because of the grave potential risks created by these shipments and because of the failure of the shippers to meet their obligations to protect coastal nations from these risks, coastal nations may be justified under international law to take unilateral or regional action to block future shipments.     

The new law of the sea: Rethinking the implications for sovereign jurisdiction and freedom of action

This article examines the effects of the 1982 UN Convention on the Law of the Sea on sovereign jurisdiction and freedom of action in key sea zones covered under this Convention for coastal, noncoastal, and landlocked states pursuant to the modifications contained in the 1994 Implementation Agreement. In order to determine whether or not the treaty increases, decreases, or has no effect on state sovereign‐jurisdiction and freedom of action in the territorial sea, the contiguous zone, the exclusive economic zone, the continental shelf, the archipelagic regime, international straits, the high seas, and the deep seabed, the rights and duties of states set forth in this Convention are compared with those previously recognized in the 1958 Geneva Law of the Sea Conventions, state practice, and other sources of international law.     

驱动蛋白结构与运动机制

驱动蛋白是一类能够利用ATP水解释放的化学能驱动其所携带的“货物”分子沿着微管（microtubule,MT）定向运动的分子马达,在细胞器运输、有丝分裂、轴突运输等方面有着重要的生理作用。随着驱动蛋白结合ADP、ATP和未结合核苷酸（APO）三种特征状态的晶体结构的解析,驱动蛋白构象变化的研究得到了进一步发展,而在力产生机制和运动模型方面仍然存在较大争议。本文以kinesin-1家族为例,分析了驱动蛋白三种特征状态结构的特点、状态结构间的构象转变,论述了驱动蛋白的力产生机制和整个迈步过程。并探讨了驱动蛋白的运动模型,同时采用分子动力学模拟比较了驱动蛋白的两种迈步方式,为深入研究驱动蛋白提供了一定的理论计算。最后,基于本课题组对复杂体系的研究,对驱动蛋白体系的控制机制提出了新的假设,并对未来的研究方向进行了展望。     

International Regulation on Low-Carbon Shipping for Climate Change Mitigation: Development,Challenges, and Prospects

This article outlines the contribution of international shipping to climate change and examines different approaches to regulate international shipping activities to reduce greenhouse gas (GHG) emissions. It considers challenges such as the allocation of GHG emissions to individual states, the selection of the most effective mitigation and regulatory measures, the potential for a disproportionate burden to fall upon developing states, and the debate about whether the United Nations (UN) or the International Maritime Organization (IMO) is the appropriate international authority to regulate emissions from international shipping.     

Transport of macromolecules between the nucleus and the cytoplasm.

Nuclear transport is an energy-dependent process mediated by saturable receptors. Import and export receptors are thought to recognize and bind to nuclear localization signals or nuclear export signals, respectively, in the transported molecules. The receptor-substrate interaction can be direct or mediated by an additional adapter protein. The transport receptors dock their cargoes to the nuclear pore complexes (NPC) and facilitate their translocation through the NPC. After delivering their cargoes, the receptors are recycled to initiate additional rounds of transport. Because a transport event for a cargo molecule is unidirectional, the transport receptors engage in asymmetric cycles of translocation across the NPC. The GTPase Ran acts as a molecular switch for receptor-cargo interaction and imparts directionality to the transport process. Recently, the combined use of different in vitro and in vivo approaches has led to the characterization of novel import and export signals and to the identification of the first nuclear import and export receptors.     

Cryo-electron tomography provides novel insights into nuclear pore architecture: implications for nucleocytoplasmic transport

To go beyond the current structural consensus model of the nuclear pore complex (NPC), we performed cryo-electron tomography of fully native NPCs from Xenopus oocyte nuclear envelopes (NEs). The cytoplasmic face of the NPC revealed distinct anchoring sites for the cytoplasmic filaments, whereas the nuclear face was topped with a massive distal ring positioned above the central pore with indications of the anchoring sites for the nuclear basket filaments and putative intranuclear filaments. The rather "spongy" central framework of the NPC was perforated by an elaborate channel and void system, and at the membrane pore interface it exhibited distinct "handles" protruding into the lumen of the NE. The most variable structural moiety of the NPC was a rather tenuous central plug partially obstructing the central pore. Its mobile character was documented by time-lapse atomic force microscopy. Taken together, the new insights we gained into NPC structure support the notion that the NPC acts as a constrained diffusion pore for molecules and particles without retention signal and as an affinity gate for signal-bearing cargoes.