This review focuses on the pathway-dependent crystallization of the host–guest complexes based on the macrocyclic host molecules in aqueous media. The high degree of structural diversity from the same host and guest molecular building blocks can be achieved through simple manipulation of the crystallization conditions, such as pH, presence of additives, or cosolvents. The kinetic factors can also be crucial to determine the crystallization pathway and structure of the host–guest assemblies, especially in the case of macrocyclic hosts with constrictive binding. All these significantly broaden the host–guest crystal engineering landscape and accessibility of different crystal forms. The exciting perspectives encompass the on-demand obtaining of various crystal complexes with programmed structure and lifetime from the same host and guest components.

Calcium oxalate (CaOx) crystals, ubiquitous in numerous plant families, have emerged as fascinating and complex structures with far-reaching implications in plant physiology, ecology, and human health. This paper encapsulates a comprehensive exploration of CaOx crystals, beginning with their formation and physiological role within plants, to their larger ecological implications, and finally, their impact on human society. Recent research has elucidated key genes involved in CaOx crystal formation, as well as the crystals’ diverse physiological roles, including their function in calcium regulation, defense against herbivory, and potential contributions to carbon sequestration. We also highlight the ecological significance of CaOx crystals in nutrient cycling and plant-soil interactions, and the potential hazards posed by these crystals in human nutrition, particularly in the context of oxalate-rich diets and kidney stone formation. Despite significant advances, many aspects, particularly their ecological impacts and potential role in climate change mitigation, remain under-explored, necessitating future research.

After an introductory section providing some basic foundation, definitions, and terminology regarding space group symmetry in crystal structures, three particular examples are selected to demonstrate the information given for each space-group type in the standard reference book International Tables for Crystallography Volume A (current sixth edition). The format and layout of the information is explained, and the most important items of the content are described, together with some practical applications. This treatment should enable readers unfamiliar with the tables to use them confidently in understanding and interpreting crystal structures belonging to these and other space-group types.

SARS-CoV-2 nsp13 is a multifunctional helicase from helicase superfamily 1B. It unwinds the viral RNA genome for replication and is thought to play a role in 5’ mRNA capping to produce mature mRNA using its triphosphatase activity. The sequence and structure are highly conserved in nidovirales and the protein is essential to the viral infection cycle, acting as a standalone enzyme and in conjunction with other SARS-CoV-2 proteins, making SARS-CoV-2 helicase a promising target for structure-based drug design. By inhibiting helicase activity, phosphatase activity, or its interaction with the RNA-dependent RNA polymerase we could interrupt viral replication. A total of 72 structures of SARS-CoV-2 nsp13 have been published in the protein databank (PDB) to date, 56 monomers and 16 as part of a complex. The structure of nsp13 is made up of five conserved folds, from N- to C-terminus, a zinc-binding domain, stalk domain, beta barrel domain 1B, RecA-like subdomain 1A, and RecA-like subdomain 1B. This review summarizes the current structural and functional knowledge surrounding SARS-CoV-2 nsp13 and related helicases, as well as the structure-based drug design efforts to date, and other complementary knowledge to provide downstream users of SARS-CoV-2 structures with a solid foundation to better inform their work.

The structural proteins located on the SARS-CoV-2 envelope, namely the spike, membrane and envelope protein, play important roles during the entire viral infection cycle. For example, the interaction between the membrane protein and the other structural proteins results in the formation of new virions, while the envelope protein then mediates their secretion. The membrane protein and envelope protein are considered potential drug targets, driving future exploration of their structures and interactions. However, research efforts are complicated as both proteins are membrane-bound and have several functions depending on their tertiary and quaternary structure. Here we review data originating from different sources and explain what is known about the structure and function of these proteins to date.