α-FeOOH exhibits high thermodynamic stability and is the most abundant iron hydroxide in soils and sediments, commonly found as a weathering product in various rocks. Under high pressure, it undergoes a phase transition to the high-pressure phase ϵ-FeOOH. This review discusses the structural, thermal, physical, and spectroscopic properties of α-FeOOH and ϵ-FeOOH. Through a combination of experimental observations and theoretical models, it has been demonstrated that ϵ-FeOOH can form stable solid solutions with δ-AlOOH and MgSiO4H2, thereby extending the stability range of these phases into the lower mantle. The key effects of phase transitions of α-FeOOH and ϵ-FeOOH, including hydrogen bond symmetrization and spin state changes, directly influence the physical properties of these minerals, such as bulk modulus, electrical conductivity, and elasticity. The ultrahigh-pressure phase Py-FeOOHX may decompose in rising mantle plumes, contributing sporadic oxygen sources for the Great Oxidation Event. The Great Oxidation Event, lasting from approximately 2.4 to 2.06 billion years ago, may have been triggered by a prolonged period of instability. Whether other hydrous minerals exhibit similar behaviours, potentially leading to an underestimation of sporadic deep sources, remains an open question for future research.

Spike proteins protrude from the SARS-CoV-2 viral envelope and are responsible for initiating fusion into human epithelial cells by binding Angiotensin-Converting Enzyme 2 receptors on the host cell surface. Due to their exposed location on the outside of the virion and their key role in infection, SARS-CoV-2 spike proteins are an important target for vaccine development and drug design. Over the last two years, many spike protein structures have been experimentally determined, providing essential details into the complex structural rearrangements that occur after receptor binding and during fusion of the virion with the host cell, as well as into the interactions of spike protein molecules with antibodies. SARS-CoV-2 variants, particularly those associated with reduced vaccine efficacy, are strongly associated with mutations in two domains of the SARS-CoV-2 spike protein, namely the receptor binding domain and the N-terminal domain, which have both been structurally characterized. This review provides a comprehensive overview of the structural knowledge acquired over the past four years on the SARS-CoV-2 spike protein and its critical role in viral infection.

Following infection, SARS-CoV-2’s leader protein nsp1 is the very first viral protein to be expressed. Its sequence is highly conserved among different SARS-CoV-2 strains, indicating its vital function that makes it a promising target for drugs and vaccination. Nsp1 takes over the host cell protein expression machinery to facilitate the production of SARS-CoV-2 virions by the host cell by binding to the ribosome and obstructing the expression of any but the viral proteins. To date, 28 structures obtained by cryo-electron microscopy and X-ray diffraction have been published, showing the protein’s structural features as well as a number of interactions with host ribosomes. Nsp1 has also been shown to interfere with immune response pathways and is connected to the cytokine storm causing organ damage and failure in COVID-19 patients.

Twinned crystals are the subject of intensive investigation since the dawn of crystallography, because of their peculiar, eye-catching morphology. The occurrence of twins affects the physical properties of materials and can be a serious hindrance to the solution and refinement of the crystal structure. In this review, we present basic definitions and terminology, a brief survey of the formation mechanism of twins, the reticular and structural approach to explain their occurrence and a few examples. The presence of a substructure shared by the twinned crystals is considered the key feature for the formation of twins. This common substructure can be found by determining first of all a common sublattice, and then by identifying those crystallographic orbits which possess, in their eigensymmetry, operations whose linear part coincide with the twin operation. The orientation and location of the composition surface play, however, a fundamental role in determining the degree of structural restoration which defines the common substructure. Examples in staurolite, feldspars and an organic co-crystal composed of N-iodosaccharin and pyridine, all taken from the literature, are presented.

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.

The main focus of drug development against COVID-19 is on the spike protein and proteases. However, such drugs can be problematic because of mutations (in the case of the spike protein) and harmful to cellular homologs (in case of the proteases). Here, we review a viral protein that due to its conserved and multifunctional nature may be an alternative drug target: SARS-CoV-2 nucleocapsid. This protein consists of two ordered and three disordered domains, all of which exhibit RNA binding activity and are important for ribonucleoprotein complex assembly. This complex protects the viral RNA and is important for viral replication. Nucleocapsid might also be connected to modulation of the host cell cycle, replication, translation, viral assembly, and other parts of the infection cycle. The two ordered domains, the RNA binding domain and the dimerization domain, mediate packaging of the RNA into the ribonucleoprotein complex and bind it to membrane proteins. The actual organization of this complex has not been conclusively verified yet, but the large SARS-CoV-2 RNA genome is efficiently packed yet is very flexible. A better understanding of this protein could lead to an efficient therapeutic measure against the virus and would improve our understanding of COVID-19.

“Everything we love about civilization is a product of intelligence, so amplifying our human intelligence with artificial intelligence has the potential of helping civilization flourish like never ...

After more than half a century of evolution, machine learning and artificial intelligence, in general, are entering a truly exciting era of broad application in commercial and research sectors. In X-ray crystallography, and its application to structural biology, machine learning is finding a home within expert and automated systems, is forecasting experiment and data analysis outcomes, is predicting whether crystals can be grown and even generating macromolecular structures. This review provides a historical perspective on AI and machine learning, offers an introduction and guide to its application in crystallography and concludes with topical examples of how it is currently influencing macromolecular crystallography.