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Controlling the identity of the tip-terminating atom or molecule in low-temperature atomic force microscopy has led to ground breaking progress in surface chemistry and nanotechnology. Lacking a comparative tip-performance assessment, a profound standardization in such experiments is highly desirable. Here we directly compare the imaging and force-spectroscopy capabilities of four atomically defined tips, namely Cu-, Xe-, CO-, and O-terminated Cu-tips (CuOx-tips). Using a nanostructured copper-oxide surface as benchmark system, we found that Cu-tips react with surface oxygen, while chemically inert Xe- and CO-tips allow entering the repulsive force regime enabling increased resolution. However, their high flexibility leads to imaging artifacts and their strong passivation suppresses the chemical contrast. The higher rigidity and selectively increased chemical reactivity of CuOx-tips prevent tip-bending artifacts and generate a distinct chemical contrast. This result is particularly promising in view of future studies on other metal-oxide surfaces.
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http://dx.doi.org/10.1039/d1nr04080d | DOI Listing |
Nat Rev Mol Cell Biol
September 2025
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA.
The defining property of eukaryotic cells is the storage of heritable genetic material in a nuclear compartment. For eukaryotic cells to carry out the myriad biochemical processes necessary for their function, macromolecules must be efficiently exchanged between the nucleus and cytoplasm. The nuclear pore complex (NPC) - which is a massive assembly of ~35 different proteins present in multiple copies totalling ~1,000 protein subunits and architecturally conserved across eukaryotes - establishes a size-selective channel for regulated bidirectional transport of folded macromolecules and macromolecular assemblies across the nuclear envelope.
View Article and Find Full Text PDFJ Chem Theory Comput
September 2025
Department of Chemistry, Aarhus University, DK-8000 Aarhus, Denmark.
The minimal basis iterative Stockholder (MBIS) decomposition of molecular electron densities into atomic contributions is extended from spherical to ellipsoidal atomic basins. Despite the more flexible parametrization, the derived atomic multipole moments do not systematically improve the reproduction of molecular multipole moments and electrostatic potentials relative to a decomposition into spherical atomic densities. The decomposition can be constrained to exactly reproduce molecular multipole moments, in the present work extended up to hexadecapole moments, and this slightly improves the ability to reproduce the electrostatic potential.
View Article and Find Full Text PDFJ Am Chem Soc
September 2025
Department of Chemistry, National Taiwan University, Taipei 106319, Taiwan.
The exclusive formation of artificial multicomponent assemblies remains a significant challenge, in contrast to the well-established organization observed in natural systems, due to intrinsic entropic constraints. To overcome this limitation, recent efforts have been focused on developing precision self-assembly strategies for the rational construction of such architectures. Here, we construct an ideal complementary pair of 2,2':6',2″-terpyridine (tpy)-based ligands by fine-tuning the substituent bulkiness, which enables the quantitative formation of robust nested cages through efficient dynamic heteroleptic complexation with multivalent coordination.
View Article and Find Full Text PDFPLoS Comput Biol
September 2025
University of Chinese Academy of Sciences, Beijing, China.
The divergence in folding pathways between RNA co-transcriptional folding (CTF) and free folding (FF) is crucial for understanding dynamic functional regulation of RNAs. Here, we developed a simplified all-atom molecular dynamics framework to systematically compare the folding kinetics of an RNA hairpin (PDB:1ZIH) under CTF and FF conditions. By analyzing over 800 microseconds of simulated trajectory, we found that despite convergence to identical native conformations across CTF simulations (with varied transcription rates) and FF simulations, they exhibit distinct preferences for the folding pathways defined by the order of base-pair formation.
View Article and Find Full Text PDFAdv Mater
September 2025
KU-KIST Graduate School of Converging Science and Technology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea.
Metal-nitrogen-carbon (M-N-C) catalysts display considerable potential as cost-effective alternatives to noble metals in oxygen electrocatalysis. However, uncontrolled atomic migration and random structural rearrangement during pyrolysis often lead to disordered coordination environments and sparse active sites, fundamentally limiting their intrinsic catalytic activities and long-term durability. Herein, a novel strategy is reported for use in directionally regulating atomic migration pathways via the incorporation of a foreign metal (La).
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