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Introduction I. The Legislative and Constitutional Framework: of the Special Advocate System A. Secret Hearings and the Right to a Fair Trial B. The Special Advocate System in Canada C. [...], In today's society, the open court principle can sometimes clash with the need for secrecy on national security, national defence, and other grounds. Governments have had to devise solutions to uphold the rule of law while keeping in mind those concerns. Drawing on the experience of the United Kingdom, Canada has set up a system of secret hearings under the security certificate system, while providing security-cleared Special Advocates for affected individuals, who can access sensitive information and protect the interests of those individuals. The authors seek to shed some light on two questions: how do secret hearings work and to what extent do they abide by the rule of law? Through analysis of the major Canadian cases on secret hearings under the security certificate system--Almrei, Charkaoui, Mahjoub, Harkat, and Jaballah--and interviews with practitioners involved in the Special Advocate system, the authors provide insights on what the system looks like, and how it fits within the rule of law. In particular, the authors explore the Federal Court's development of procedural norms and the concerns these uncodified norms raise for the rule of law. While the Special Advocate system has produced high-quality legal work, there is reason to be skeptical of the extent to which it is able to constrain arbitrary decision making in secret hearings.

Canadian cities pledge to provide access to municipal services to non‐status migrants and withhold information identifying non‐status migrants from federal immigration authorities. Despite these promises, local police continue to cooperate with the Canada Border Services Agency, which raises questions about the capacity of cities to honour their promises. An empirical study involved interviews with high‐ranking police officers in eight local jurisdictions in Ontario about police perceptions regarding their role in the enforcement of federal immigration law and their obligations to honour sanctuary‐city policies. The results show that many police officers believe they possess legal authority to report non‐status migrants to federal authorities. We suggest that this belief rests on misconceptions about the relationship between criminal law and immigration law, claims of jurisdictional immunity from municipal government, and distortions of the principles of policing in Canada. Rescaling of sanctuary policies to the provincial level may offer solutions. [ABSTRACT FROM AUTHOR]

The officers of the Canada Border Services Agency (CBSA) play pivotal roles at various stages in Canada's refugee system, making decisions that are life-changing for asylum seekers. This article examines the evolving institutional setting and processes that define the CBSA's enforcement policy and its consequences for asylum seekers in Canada. Drawing on the findings of field-research, conducted between October 2015 and May 2018 in three Canadian provinces (Ontario, British Columbia, and Quebec), it argues that the Agency operates in a specific social universe heavily shaped by the post-9/11 geopolitical context of the criminalization of migration. This situation has been exacerbated by the major overhaul of Canada's refugee system, undertaken by the previous Conservative government in 2012. The article further contends that the way the CBSA has been involved in refugee status determination turns Canada's refugee system into an adversarial and unfair process for some groups of asylum seekers. To that end, it highlights the CBSA's policies in three areas: eligibility determination, front-end security screening of refugee claimants, and ministerial interventions at the Immigration and Refugee Board of Canada. [ABSTRACT FROM AUTHOR]

Graphical abstract The threat of antibiotic resistant bacterial infections continues to underscore the need for new treatment options. Historically, small molecule metabolites from microbes have provided a rich source of antibiotic compounds, and as a result, significant effort has been invested in engineering the responsible biosynthetic pathways to generate novel analogs with attractive pharmacological properties. Unfortunately, biosynthetic stringency has limited the capacity of non-ribosomal peptide synthetases and polyketide synthases from producing substantially different analogs in large numbers. Another class of natural products, the ribosomally synthesized and post-translationally modified peptides (RiPPs), have rapidly expanded in recent years with many natively displaying potent antibiotic activity. RiPP biosynthetic pathways are modular and intrinsically tolerant to alternative substrates. Several prominent RiPPs with antibiotic activity will be covered in this review with a focus on their biosynthetic plasticity. While only a few RiPP enzymes have been thoroughly investigated mechanistically, this knowledge has already been harnessed to generate new-to-nature compounds. Through the use of synthetic biology approaches, on-going efforts in RiPP engineering hold great promise in unlocking the potential of this natural product class. [ABSTRACT FROM AUTHOR]

Digital image capture, processing, storage, transmission, and display are now taken for granted as part of the technology of modern everyday life. Digital image compression is one of the enabling technologies of the present multimedia world. The image compression technique used for application as diverse as photography, web pages, medical imaging, and public records is JPEG, named after the ISO/CCITT "joint photographic experts group," established in 1986, which developed the technique in the late 1980s and produced the international standard in the early '90s. ITU-T T.81|ISO/IEC 10918-1, also called "JPEG-1" has become one of the most successful standards in information and communication technologies (ICT) history. The authors of this paper -- all members of the original JPEG development team -- were all intimately involved in image-coding research and JPEG in particular. The paper goes behind the scenes explaining why and how JPEG came about and looks under the bonnet of the technique explaining the different components that give the standard of its efficiency, versatility, and robustness that have made a technique that has stood the test of time and evolved to cover applications beyond its original scope. In addition, the authors give a short outlook of the main milestones in coding schemes of still images since "JPEG-1." [ABSTRACT FROM AUTHOR]

The bottromycins belong to the ribosomally synthesized and posttranslationally modified peptide (RiPP) family of natural products. Bottromycins exhibit unique structural features, including a hallmark macrolactamidine ring and thiazole heterocycle for which divergent members of the YcaO superfamily have been biosynthetically implicated. Here we report the in vitro reconstitution of two YcaO proteins, BmbD and BmbE, responsible for the ATP-dependent cyclodehydration reactions that yield thiazoline- and macrolactamidine-functionalized products, respectively. We also establish the substrate tolerance for BmbD and BmbE and systematically dissect the role of the follower peptide, which we show serves a purpose similar to canonical leader peptides in directing the biosynthetic enzymes to the substrate. Lastly, we leverage the expanded capabilities of YcaO proteins to conduct an extensive bioinformatic survey to classify known YcaO chemistry. This analysis predicts new functions remain to be uncovered within the superfamily. [ABSTRACT FROM AUTHOR]

The [4+2] cycloaddition reaction is an enabling transformation in modern synthetic organic chemistry, but there are only limited examples of dedicated natural enzymes that can catalyze this transformation. Thiopeptides (or more formally thiazolyl peptides) are a class of thiazole-containing, highly modified, macrocyclic secondary metabolites made from ribosomally synthesized precursor peptides. The characteristic feature of these natural products is a six-membered nitrogenous heterocycle that is assembled via a formal [4+2] cycloaddition between two dehydroalanine (Dha) residues. This heteroannulation is entirely contingent on enzyme activity, although the mechanism of the requisite pyridine/dehydropiperidine synthase remains to be elucidated. The unusual aza-cylic product is distinct from the more common carbocyclic products of synthetic and biosynthetic [4+2] cycloaddition reactions. To elucidate the mechanism of cycloaddition, we have determined atomic resolution structures of the pyridine synthases involved in the biosynthesis of the thiopeptides thiomuracin (TbtD) and GE2270A (PbtD), in complex with substrates and product analogs. Structure-guided biochemical, mutational, computational, and binding studies elucidate active-site features that explain how orthologs can generate rigid macrocyclic scaffolds of different sizes. Notably, the pyridine synthases show structural similarity to the elimination domain of lanthipeptide dehydratases, wherein insertions of secondary structural elements result in the formation of a distinct active site that catalyzes different chemistry. Comparative analysis identifies other catalysts that contain a shared core protein fold but whose active sites are located in entirely different regions, illustrating a principle predicted from efforts in de novo protein design. [ABSTRACT FROM AUTHOR]

JPEG is celebrating the 25th anniversary of its approval as a standard this year. Where did JPEG come from, and what are the fundamental components that have given it longevity? [ABSTRACT FROM PUBLISHER]

The biosynthesis of the thiopeptide thiomuracin is a well-orchestrated process involving a multitude of posttranslational modifications. We show that six Cys residues of a precursor peptide are first cyclodehydrated and oxidized to thiazoles in an ordered, but nonlinear fashion that is leader-peptide-dependent. Then four alcohols are glutamylated and converted to alkenes in a C-to-N terminal directional process that is leader-peptide-independent. Finally, two of these alkenes undergo a formal [4 + 2] cycloaddition to form a trithiazole-substituted pyridine macrocycle. We describe here the factors that govern the substrate specificity and order of biosynthetic events that turn a ribosomal peptide into a powerful antibiotic. [ABSTRACT FROM AUTHOR]

Thiopeptides are potent antibiotics that inhibit protein synthesis. They are made by a remarkable post-translational modification process that transforms a linear peptide into a polycyclic structure. We present here the in vitro biosynthesis of the core scaffold of thiomuracin catalyzed by six proteins. We show that cyclodehydration precedes dehydration, and that dehydration is catalyzed by two proteins in a tRNAGlu-dependent manner. The enzyme that generates the pyridine core from two dehydroalanines ejects the leader peptide as a C-terminal carboxamide. Mutagenesis studies of the enzyme TbtD identified important residues for a formal [4+2] cycloaddition process. The core structure of thiomuracin exhibits similar antimicrobial activity to other known congeners, illustrating that in vitro biosynthesis is a viable route to potent antibiotics that can be explored for the rapid and renewable generation of analogues. [ABSTRACT FROM AUTHOR]

Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a rapidly growing class of natural products. RiPP precursor peptides can undergo extensive enzymatic tailoring to yield structurally and functionally diverse products, and their biosynthetic logic makes them attractive bioengineering targets. Recent work suggests that unrelated RiPP-modifying enzymes contain structurally similar precursor peptide-binding domains. Using profile hidden Markov model comparisons, we discovered related and previously unrecognized peptide-binding domains in proteins spanning the majority of known prokaryotic RiPP classes, and we named this conserved domain the RiPP precursor peptide recognition element (RRE). Through binding studies we verified RRE's roles for three distinct RiPP classes: linear azole-containing peptides, thiopeptides and lasso peptides. Because numerous RiPP biosynthetic enzymes act on peptide substrates, our findings have powerful predictive value as to which protein(s) drive substrate binding, thereby laying a foundation for further characterization of RiPP biosynthetic pathways and the rational engineering of new peptide-binding activities. [ABSTRACT FROM AUTHOR]

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