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Joined 2026-09-21 Message
Incoming links: Covalent bond
Sigma bond 2026-10-20
A covalent bond with bonding electron density of cylindrical symmetry around the internuclear axis; end-on orbital overlap is a common localized construction.
Journal of Chemical Physics 98, 3564–3567. Neutral helium dimers inferred from ionization of a cold expansion; supports the distinction between no ordinary covalent bond and no bound dimer. Author-deposited record: scholarworks.gvsu.edu/chm_articles/6/
Type IV collagen 2026-11-05
Type IV collagen is a network-forming collagen of the basement membrane, the specialized extracellular matrix underlying an epithelium and supporting other tissue interfaces. Triple-helical molecular units associate into a sheet-like scaffold and are reinforced by intermolecular covalent bonds.[ref]
A Sulfilimine Bond Identified in Collagen IV by Roberto Vanacore and others. 2009, abstract and Fig.3, basement-membrane network architecture
The chemistry of that reinforcement was identified using mass spectrometry and nuclear magnetic resonance. Researchers isolated linked peptides from adjoining units and identified a sulfilimine bond between a methionine residue and a hydroxylysine residue. Chemical reduction broke the linkage and recovered the constituent peptides, supplying a further test of the proposed bond.[ref]
The example connects three scales: the identity of an amino acid side chain, a chemical link between proteins, and stabilization of a supporting tissue network. Knowing only that a specimen contains collagen leaves these structural and chemical distinctions unresolved.
Vladimir E. Bondybey Created 2026-10-20 Updated 2026-11-05
Vladimir E. Bondybey coauthored research on beryllium dimer.[ref]
Beryllium dimer caught in the act of bonding by Jeremy M. Merritt and colleagues. publication title and author list
The neutral molecule Be-two. Its simplest filled sigma-two-s/bonding and antibonding description gives zero bond order, but mixing of accessible two-p configurations and electron correlation produce a weak covalent bond. Resolved vibrational levels establish a bound ground-state potential.
W. Ronald Gentry Created 2026-10-20 Updated 2026-11-05
W. Ronald Gentry coauthored research on helium dimer.[ref]
The weakest bond: experimental observation of helium dimer by Fei Luo and colleagues. publication title and author list
A very weakly bound van der Waals molecule, observed in cold helium expansions. The absence of an ordinary covalent bond in the elementary molecular orbital model must not be confused with absence of every possible bound dimer.