Chemical Engineering: In-Depth Description

Chemical engineering is an applied discipline that merges the principles of chemistry, physics, mathematics, and biology to design, optimize, and scale processes that transform raw materials into valuable products. Its primary goal is to safely, sustainably, and economically translate microscopic molecular reactions discovered in the laboratory into macroscopic, large-scale industrial manufacturing processes.

RhoBAST RNA Mechanism: Super-Resolution Live-Cell Imaging

Three-dimensional structure of RhoBAST RNA interacting with the fluorophore (yellow).
Image Credit: Christoph Mitteregger and Ronald Micura

Scientific Frontline: Extended "At a Glance" Summary: RhoBAST RNA

The Core Concept: RhoBAST is a small, specialized RNA molecule (a fluorescent light-up aptamer) that binds to and activates specific fluorescent dyes, allowing researchers to track individual RNA molecules inside living cells with high resolution.

Key Distinction/Mechanism: Unlike traditional tagging methods that require bulky protein fusions, RhoBAST functions through a simple "nucleotide flip." When the dye approaches, a single RNA building block (guanosine residue G38) flips outward, creating a pocket for the dye. This dynamic, localized movement enables rapid ligand exchange and fluorescence "blinking"—the key to super-resolution imaging. Background fluorescence remains low because the dye only emits strong light when bound to the RNA.

Major Frameworks/Components:

• Fluorescent Light-Up Aptamers (FLAPs): Short RNA sequences designed to bind small molecules and enhance their fluorescence.
• Inverted V-Shaped Structure: The specific three-dimensional conformation RhoBAST adopts to accommodate the dye between two RNA loops.
• Nucleotide Flipping: The critical structural rearrangement (specifically of the G38 residue) that allows dye binding and the characteristic "blinking" effect.
• Biophysical Assays: Techniques such as fluorescence spectroscopy, surface plasmon resonance (SPR), and 2-aminopurine kinetics used to verify the mechanism.

Smart Nanoparticles Reprogram Tumor Macrophages to Fight Cancer

Lipid Nanoparticles
Image Credit: Courtesy of Adelaide University

Scientific Frontline: Extended "At a Glance" Summary: Smart Nanoparticles Reprogram Tumor Microenvironments

The Core Concept: Researchers have engineered lipid nanoparticles that deliver mRNA technology to tumor-associated macrophages (TAMs), reprogramming these immune cells from tumor-supporting to cancer-fighting.

Key Distinction/Mechanism: Instead of attacking TAMs, which are large white blood cells that help tumors evade the immune system, the nanoparticles are coated with an antibody targeting the TREM2 protein on the macrophages. Once inside, they deliver mRNA to produce the CXCL9 chemical signal and Resiquimod, which collectively switch the macrophages' behavior and attract cancer-fighting T cells.

Major Frameworks/Components:

• Lipid Nanoparticles: Utilizes the same delivery mechanism as COVID-19 mRNA vaccines.
• Tumor-Associated Macrophages (TAMs): The specific immune cells targeted for reprogramming.
• TREM2 Protein: The target for the nanoparticle's antibody coating, allowing entry into the TAMs.
• mRNA & CXCL9: mRNA instructions prompt the production of CXCL9, a chemical beacon that attracts cancer-fighting CD8+ T cells.
• Resiquimod: A compound delivered alongside the mRNA that helps reverse the immune-suppressing behavior of the macrophages.

How Monkeypox Replicates: Viral Protein Mechanisms Explained

Colorized transmission electron micrograph of monkeypox virus particles (teal) in an infected cell (brown).
Image Credit: NIAID

Scientific Frontline: Extended "At a Glance" Summary: Monkeypox Virus Replication

The Core Concept: Researchers have discovered how two monkeypox virus proteins, helicase-primase and polymerase, change shape and bind together to initiate viral replication.

Key Distinction/Mechanism: The helicase-primase protein is mostly inactive on its own because its primase region blocks the DNA channel. However, when the polymerase protein binds to it, the primase region is pulled aside, opening the channel and allowing the newly formed "replisome" to unwind and replicate the viral DNA.

Origin/History: The monkeypox virus was first found in animals in 1958, with the first human case occurring in 1970. The detailed mechanism of its replication, published in Nature in September 2026, utilized cryo-electron microscopy and optical tweezers to visualize this process at a near-atomic level and in real time.

Major Frameworks/Components:

• Helicase-Primase: The protein responsible for unzipping the virus's DNA double helix and attaching a chemical anchor for a new DNA strand.
• Polymerase: The protein that recruits and organizes building blocks to assemble the new DNA strand.
• Replisome: The fully functioning unit created when the helicase-primase and polymerase bind together.
• Cryo-Electron Microscopy (Cryo-EM): Imaging technology used to capture snapshots of the replisome interacting with DNA in near-atomic detail.
• Optical Tweezers: A tool used to observe the unwinding of the DNA double helix by the replisome in real time.

Novel AML Treatment Burns Out Cancer Cells

Photo Credit: Akram Huseyn

Scientific Frontline: Extended "At a Glance" Summary: Novel Treatment for Acute Myeloid Leukemia

The Core Concept: Researchers have developed a novel therapeutic approach that combats acute myeloid leukemia (AML) by forcing the cancer cells to maintain a state of high activity while simultaneously cutting off their energy supply, causing them to die from metabolic stress.

Key Distinction/Mechanism: Unlike traditional methods that focus on damaging DNA, this treatment targets cancer metabolism. A newly designed molecule called AcTor stimulates the mTor protein, a cellular control center, to promote continuous cell growth and activity. Concurrently, a standard anti-proliferative drug (Ixazomib) shuts down energy production in the mitochondria. This dual action—pushing the accelerator while applying the brake—induces fatal stress in the cancer cells without harming healthy blood cells or triggering drug resistance.

Major Frameworks/Components:

• AcTor: A newly designed molecule that inhibits a signaling protein to stimulate mTor.
• mTor Protein: A cellular control center regulating growth, maintenance, and rest.
• Mitochondria: The energy-producing structures within cells, targeted for shutdown by the treatment.
• Ixazomib (IXZ): An inhibitor used in combination with AcTor to block energy production.
• ADM2 Protein: Released during the treatment, potentially serving as a biomarker for clinical response.

Single-Atom Swap Speeds Up Drug Discovery

A group of chemists with the University of Chicago has shown a new way to make a single-atom edit to a molecule, without changing any of its other components.
Photo Credit: Rodolfo Clix

Scientific Frontline: Extended "At a Glance" Summary: Single-Atom Substitution for Pyrrole Synthesis

The Core Concept: University of Chicago chemists have developed a "skeletal editing" technique to swap a single oxygen atom for a carbon atom within a molecule, directly converting isoxazoles into pyrroles.

Key Distinction/Mechanism: Instead of synthesizing complex pyrrole molecules from scratch, this method uses a substitution reaction to attach a propargyl group (containing three carbons) to an isoxazole ring. The ring is then cut, and the oxygen atom is replaced with one of the new carbon atoms, completing the conversion in a single flask over one to two days.

Major Frameworks/Components:

• Pyrroles: A family of molecules foundational to life, forming the basis of heme in blood and chlorophyll in plants, but traditionally difficult and expensive to synthesize in the laboratory.
• Isoxazoles: Molecules structurally near-identical to pyrroles, differing by a single atom (oxygen instead of carbon), but significantly cheaper and easier to manufacture.
• Skeletal Editing: An approach to chemical synthesis that focuses on making targeted alterations to the core structure of existing molecules rather than building them entirely anew.
• Propargyl Group: A specific three-carbon atom group utilized in the substitution reaction to facilitate the oxygen-to-carbon swap.

Low-Temperature Graphene Growth for Sustainable Recycling

Acetylene molecules are converted into graphene on cerium oxide nanoparticles through low-temperature chemical vapor deposition.
Image Credit: © Mengxuan Zhang et al.

Scientific Frontline: Extended "At a Glance" Summary: Low-Temperature Graphene Growth

The Core Concept: Researchers have successfully synthesized graphene-based materials at temperatures as low as 300 °C using acetylene gas and a cerium oxide (CeO₂) catalyst.

Key Distinction/Mechanism: Conventional graphene production requires temperatures up to 900 °C, making structural control difficult. The new method utilizes cerium oxide, which easily forms oxygen vacancies, causing acetylene to decompose at 113 °C and acting as active catalytic sites for graphene growth at 300 °C. The structure of the graphene can be controlled simply by adjusting the temperature.

Major Frameworks/Components:

• Cerium Oxide (CeO₂) Catalyst: Generates oxygen vacancies that facilitate low-temperature decomposition of acetylene.
• Acetylene Gas: A highly reactive carbon source that can be extracted from industrial waste, biomass, or recycled plastics.
• Temperature-Controlled Chemical Vapor Deposition (CVD): Modulating the temperature yields different materials (e.g., 300 °C for graphene quantum dots, 450 °C for aggregated graphene, 600 °C for high-surface-area porous graphene).

Cut-to-Fuse Strategy for Molecular Skeletal Editing

Scientific Frontline: Extended "At a Glance" Summary: “Cut-to-Fuse” Strategy and Molecular Skeletal Editing

The Core Concept: A novel halogen-guided “cut-to-fuse” strategy enables the mild, transition-metal-free transformation of accessible hydroxycoumarins into valuable coumaranone scaffolds via carbonyl deletion.

Key Distinction/Mechanism: Unlike traditional methods that require harsh conditions to cleave resistant carbon-carbon and carbon-oxygen bonds in esters, this approach utilizes chlorine guidance (via N-chlorosuccinimide) to drive simultaneous bond cleavage and subsequent intramolecular cyclization at room temperature.

Major Frameworks/Components:

• Halogen-guided selective chlorination of hydroxycoumarin substrates using N-chlorosuccinimide (NCS).
• Decarbonylative reconstruction involving simultaneous C–C and C–O bond cleavage under near-neutral, transition-metal-free conditions.
• Broad substrate tolerance accommodating functional groups such as methoxy, halogens, azides, phenols, carboxylic acids, and boron-containing groups across diverse aromatic and aliphatic systems.

Ice Acts as Geochemical Reactor for Iron Minerals

Glacier at Briksdal, Norway
Photo Credit: Rob Barber

Scientific Frontline: Extended "At a Glance" Summary: Ice as a Geochemical Reactor for Iron Minerals

The Core Concept: A single freeze-thaw cycle radically alters the physical structure and chemical fate of ferrihydrite, demonstrating that ice functions as an active geochemical reactor rather than a passive storage medium.

Key Distinction/Mechanism: While unfrozen ferrihydrite typically ages into goethite (yellow-brown rust), a single freeze event strips away protective water layers and compresses the nanoparticles into much larger, stable aggregates that instead age into hematite (red rust).

Major Frameworks/Components:

• Ferrihydrite: A highly reactive, nanometer-scale iron oxide dominant in cold soils and glacial sediments.
• Microscopic Confinement: As water freezes, advancing ice fronts force nanoparticles into concentrated liquid pockets, mechanically altering their structure.
• Particle Aggregation: A single freeze at −20 °C increases ferrihydrite particle size by approximately thirty times, creating robust, micrometer-sized flakes.
• Mineral Trajectory Shift: Freezing prevents the formation of goethite and redirects the mineral's aging process toward hematite.

AI Material Design: MIT's CrysVCD Framework Explained

“You can plug this into any kind of model, not only existing diffusion models but also future models, where people can’t generate enough stable materials, and it can improve stability,” says Mingda Li. Image Credit: MIT News; iStock
(CC BY-NC-ND 3.0)

Scientific Frontline: Extended "At a Glance" Summary: AI in Material Design (CrysVCD)

The Core Concept: Researchers at MIT have developed a framework called CrysVCD (crystal generator with valence-constrained design) that uses artificial intelligence to generate chemically stable and highly functional material designs.

Key Distinction/Mechanism: Unlike current models that generate millions of materials and require massive computational power to retroactively screen out chemically unstable ones, CrysVCD applies the rules of chemistry regarding electron valences at the beginning of the generation process, vastly improving the stability rate (achieving high lattice-dynamics stability in nearly 70% of generations) and efficiency.

Major Frameworks/Components:

• Generative AI Models (Diffusion & Large Language Models): Utilized to reverse-engineer materials based on desired properties.
• Valence Constrained Design: A pre-generation filter ensuring chemical validity based on fundamental electron interactions.
• Two-Stage Process: A language model first produces valid chemical formulas; a diffusion model then generates the atomic structure.

What Is: Paleovirology and Permafrost Pathogens

Scientific Frontline: Extended "At a Glance" Summary: Paleovirology and Permafrost Pathogens

The Core Concept: Paleovirology within the context of the cryosphere involves the physical extraction, isolation, and resurrection of viable, ancient microorganisms—often referred to as "zombie viruses"—that have been preserved in a state of cryptobiosis within thawing permafrost for tens of thousands to over a million years.

Key Distinction/Mechanism: Unlike standard decay in temperate zones, the strictly anoxic, pH-neutral, and sub-zero environment of Yedoma permafrost, combined with the physical shielding provided by clay minerals, suspends the biological clock of extracellular viruses and bacteria, preventing enzymatic, oxidative, and metabolic degradation indefinitely.

Origin/History: The modern physical resurrection of ancient permafrost viruses was catalyzed by the 2003 characterization of giant viruses like Acanthamoeba polyphaga mimivirus, which led to the successful revival of Pithovirus sibericum in 2014, Mollivirus sibericum in 2015, and thirteen distinct prehistoric viruses in a landmark 2023 study.

Gut Bacteria Interactions Mapped in Comprehensive New Study

Bolor Buyanbadrakh, postdoctoral fellow at the Department of Chemistry
Photo Credit: Simon Jönsson

Scientific Frontline: Extended "At a Glance" Summary: Gut Microbiome Interactions

The Core Concept: Researchers have systematically mapped over 1,200 interactions among 36 representative human gut bacterial species to understand how they promote or inhibit each other's growth.

Key Distinction/Mechanism: The study reveals that negative (inhibitory) interactions dominate, largely due to bacteria altering their environment by increasing acidity (lowering pH); however, specific cooperative mechanisms were also identified, such as the use of extracellular vesicles or pH modification to support other species.

Major Frameworks/Components:

• Inhibitory Dominance: Most interactions are competitive, primarily driven by environmental acidification.
• Vesicle-Mediated Cooperation: Clostridium perfringens promotes the growth of Mediterraneibacter gnavus via the release of extracellular vesicles.
• pH Counteraction: Veillonella parvula increases environmental pH, counteracting acidification and enabling the growth of acid-sensitive species like Parabacteroides merdae.

Coconut Biofuel Powers Jet Engines with Lower Emissions

Coconut SAF as an alternative to jet fuel
Coconut oil is processed into SAF, which is chemically similar to the commonly used jet fuel JET A-1.
 Photo Credit: Osaka Metropolitan University

Scientific Frontline: Extended "At a Glance" Summary: Coconut Oil-Based Aviation Biofuel

The Core Concept: A novel aviation biofuel synthesized from discarded coconuts using a co-solvent method, which can be blended with conventional jet fuel (Jet A-1) without compromising engine performance.

Key Distinction/Mechanism: Unlike traditional jet fuels, this biofuel is produced under ambient temperature and pressure using a co-solvent method combining coconut oil extracts with acetone and alcohol, resulting in two potential biofuels (FAME and FAEE) that reduce hydrocarbon emissions.

Major Frameworks/Components:

• Co-solvent Method: Utilizes acetone and alcohol (methanol or ethanol) to process coconut oil extracts into biofuel under ambient conditions, conserving energy and maintaining purity.
• Biofuel Variants: Production of Fatty Acid Methyl Esters (FAME) using methanol and Fatty Acid Ethyl Esters (FAEE) using ethanol.
• Performance Metrics: Experimental data showing comparable thermal efficiency to Jet A-1, with reduced hydrocarbon emissions and no significant increase in CO₂ or NO emissions.

Recyclable Polymer Ink for Sustainable 3D Printing

Schematic representation of the metastable material (left): the molecular chain is held together by a single lock (orange). As soon as the right chemical key opens this lock, the entire chain breaks down into its constituent parts within seconds (images on the right).
Image Credit: © The Blasco group

Scientific Frontline: Extended "At a Glance" Summary: Light-Based 3D Printing and Metastable Polymers

The Core Concept: A novel metastable polymer material designed for light-based 3D printing that can be rapidly disassembled into its constituent molecular building blocks for reuse.

Key Distinction/Mechanism: Unlike traditional thermosets used in light-based 3D printing, which form irreversible networks, this material features a long molecular chain held together by a single predetermined breaking point. When exposed to a specific chemical trigger (the "key"), the entire chain rapidly disintegrates at room temperature, allowing the building blocks to be recovered and reused without loss of print quality or mechanical stability.

Major Frameworks/Components:

• Metastable Polymers: Materials engineered to be stable under normal conditions but capable of rapid, controlled degradation when a specific activation energy barrier is overcome.
• Digital Light Processing (DLP): A high-precision additive manufacturing method that uses light to cure liquid "inks" into solid structures.
• Chemical Triggers: A specific chemical agent that targets a predetermined breaking point within the polymer chain, initiating depolymerization.
• Chemical Circularity: A closed-loop material cycle where products are broken down into their fundamental chemical components and synthesized back into new, identical materials.

Green Hydrazine Production from Urea

Photo Credit: Vasanth Rajasekaran

Scientific Frontline: Extended "At a Glance" Summary: Urea-to-Hydrazine Electrochemical Conversion

The Core Concept: Researchers have developed an electrochemical strategy to convert urea into hydrazine, a critical chemical used in energy storage and pharmaceuticals.

Key Distinction/Mechanism: Unlike conventional methods that rely on hazardous chemicals and high energy consumption, this new approach uses electricity and sodium chloride to facilitate the conversion, generating adsorbed chlorine species on the electrode surface that react with urea to form N-chlorourea, which then undergoes hydrolysis to become hydrazine.

Major Frameworks/Components:

• Electrochemical synthesis using sodium chloride to drive the reaction.
• Formation of intermediate N-chlorourea through reaction with adsorbed chlorine species.
• Final conversion to hydrazine via hydrolysis.

Protein-Foldamer Blocks for Complex Nanostructures

Self-assembly of a foldamer-protein 1D polymer

Video Credit: ©Johannes Sigl, LMU

Scientific Frontline: Extended "At a Glance" Summary: Protein-Foldamer Supramolecular Synthons

The Core Concept: Researchers have developed a molecular building block that utilizes an artificial protein-foldamer pair to combine proteins and synthetic molecules with high structural precision, forming complex nanostructures.

Key Distinction/Mechanism: Unlike previous protein-foldamer complexes that were less stable or required flexible connectors, this new system uses a specific protein variant (Nanofitin C10) that binds to an artificial foldamer (a stable, helical molecule) with high affinity over a large, well-defined contact surface. It selectively binds the right-handed P-helix of the foldamer, but not the left-handed M-helix.

Major Frameworks/Components:

• Foldamer: An artificial molecule that folds into a stable shape (a helix).
• Nanofitin C10: A protein scaffold variant identified through ribosome display.
• Ribosome Display: A biochemical method used to identify protein-protein (and in this case, foldamer-protein) interactions from hundreds of billions of variants.
• Analytical Techniques: Nuclear magnetic resonance (NMR) spectroscopy, X-ray crystallography, and mass spectrometry were used to analyze the structural fit and larger complexes.

Synthetic Sugar Fights Drug-Resistant Candida auris Fungus

Candida Auris
Image Credit: Scientific Frontline / stock image

Scientific Frontline: Extended "At a Glance" Summary: Synthetic Sugar Molecule against Candida auris

The Core Concept: Researchers have synthesized a specific sugar molecule, a β-mannan tetrasaccharide, that mimics a natural component of the cell wall of the multidrug-resistant fungus Candida auris, to trigger a targeted immune response.

Key Distinction/Mechanism: Instead of purifying complex and variable sugar structures directly from the fungal cell wall, scientists chemically synthesized a precise four-block sugar structure in the laboratory. By linking this synthetic sugar to a carrier protein (creating a glycoconjugate), they successfully directed the immune system to recognize and attack the fungus.

Major Frameworks/Components:

• Chemical Synthesis: Laboratory creation of a precise β-mannan tetrasaccharide to ensure a defined composition, avoiding the variability of natural fungal cell walls.
• Glycoconjugation: Linking the synthetic sugar molecule to a carrier protein to enhance the immune system's ability to recognize the sugar and mount a response.
• Passive Immunization: Developing specific antibodies that recognize the sugar structure to neutralize the pathogen directly.
• Diagnostic Application: Utilizing the generated antibodies to create a rapid lateral flow test (similar to a COVID-19 or pregnancy test) for quick detection of the fungus.

Martian Meteorite Water Discovery via Tomography

“Black Beauty,” the Martian meteorite weighs approximately 11 ounces (320 grams).
Photo Credit: NASA

Scientific Frontline: Extended "At a Glance" Summary: Water in Martian Meteorite NWA 7034

The Core Concept: By utilizing a combination of neutron and X-ray tomography, scientists have successfully identified macroscopic, hydrogen-rich regions within the ancient Martian meteorite NWA 7034, providing concrete evidence of early water-rock interactions on Mars.

Key Distinction/Mechanism: While previous studies relied on destructive heating or examining micrometer-thin sections to estimate bulk water content, this dual-tomography approach allows for the three-dimensional, non-destructive visualization of hydrated minerals distributed throughout an intact rock sample. X-rays map heavier elements, while neutrons detect light elements like hydrogen.

Origin/History: The meteorite fragment, colloquially known as "Black Beauty," weighs approximately 320 grams, contains material up to 4.48 billion years old, and landed in the Moroccan Sahara after being ejected from the Martian crust by a powerful impact.

Major Frameworks/Components:

• Neutron Tomography: Deployed to detect light elements, specifically hydrogen, which are highly sensitive to neutrons but otherwise invisible in dense rock.
• X-ray Tomography: Used to map the distribution of heavier elements, such as silicon and iron, and to define the structural cavities within the rock matrix.
• Geological Breccia: The meteorite's structure consists of debris from various geological periods fused together by high-energy impact events, acting as a complex, stratified time capsule.
• Hydrated Minerals: Chemical traces preserved as concentrated hotspots, indicating where early Martian water reacted with the planet's young crust.

Thorium Clusters Reveal New Form of Metal Aromaticity

Magnetic Mystery
Image Credit: Courtesy of University of Manchester

Scientific Frontline: Extended "At a Glance" Summary: Magnetic Mysteries in Thorium Clusters

The Core Concept: Researchers have discovered that clusters of three thorium atoms exhibit an unusual, field-induced non-linear magnetic response, behaving as aromatic "superatoms" only when exposed to an external magnetic field.

Key Distinction/Mechanism: Unlike conventional organic aromatic compounds (like benzene) that show immediate, linear diamagnetism, thorium clusters initially display weak paramagnetism before reorganizing their electrons to achieve strong diamagnetism and Jellium aromaticity as the magnetic field increases.

Major Frameworks/Components:

• Jellium Aromaticity: A specific form of electron delocalization found in metal clusters, rather than traditional carbon rings.
• Non-linear Magnetic Response: The requirement of an external magnetic field to trigger the necessary electronic reorganization for aromatic behavior.
• Heavy Element Chemistry: The unique bonding and electron behavior inherent in actinide series elements like thorium.

Clean Rare Earth Element Separation

(From left) Former University of Chicago Pritzker School of Molecular Engineering (UChicago PME) Ph.D. student Siqi Zou and Assoc. Prof. Chong Liu led a team of researchers from UChicago PME and Northwestern University that developed a cleaner method to separate rare earth elements from each other, which could affect technology manufacturing.
Photo Credit: John Zich

Scientific Frontline: Extended "At a Glance" Summary: Electrochemical Separation of Rare Earth Elements

The Core Concept: A novel, water-based processing method that purifies rare earth elements without the use of organic solvents by utilizing electrochemical intercalation to separate similar lanthanides based on the size of their hydration shells.

Key Distinction/Mechanism: Traditional extraction relies on custom molecules and copious amounts of toxic acid to separate chemically similar elements. In contrast, this new mechanism forces raw mixtures into angstrom-sized channels within layered manganese oxide, using a magnesium ion scaffold to "pin" the channel spacing and differentiate elements based on the exact size of the water shell surrounding each dissolved ion.

Major Frameworks/Components:

• Electrochemical Intercalation: Squeezing specific ions into the layered mineral matrix using an electric current.
• Hydration Shells: The layers of water molecules naturally enveloping dissolved rare earth ions, which dictate the effective physical size of each element in a solution.
• Manganese Oxide Channeling: Engineered mineral structures featuring precisely spaced gaps to filter elements by minute differences in atomic behavior.
• Magnesium Pinning: The strategic introduction of magnesium ions to serve as a rigid scaffold, preventing the mineral channels from expanding and forcing a higher binding selectivity between nearly identical elements.
• Density Functional Theory: Quantum mechanical simulations used to predict atomic arrangements and validate how rare earth elements position their hydration shells inside the confined channels.