Calixarene docks dimethyllysine on lysozyme

p-Sulfonatocalix[4]arene selectively encapsulates Lys116-Me2 on dimethylated lysozyme, mimicking an aromatic cage.

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What small-molecule receptor was co-crystallized?

p-Sulfonatocalix[4]arene (sclx4) with dimethylated lysozyme.

Which dimethyllysine is encapsulated?

Lys116-Me2, matching the NMR site.

What 1H NMR marker indicated binding?

NεMe of Lys116-Me2 near 2.92 ppm with a large upfield shift.

What resolution were the two structures?

1.9 and 2.2 Å, nearly identical.

What interaction is expected to dominate binding?

Cation–π interactions rather than salt bridges, plus the hydrophobic effect.

Did Lys116 conformation change much on binding?

Almost identical to unbound dimethylated lysozyme except Cδ–Cε rotation.

Why is Lys116 preferred over other Lys-Me2 sites?

Greater steric accessibility; neighbors Asn106, Arg112, Gly117.

How long were the MD runs per site?

Duplicate 10 ns simulations on each of six Lys-Me2 side chains.

What binding-distance range means deep encapsulation?

4–5 Å, enabling cation–π contacts.

Did ESI-MS show complete dimethylation?

Yes: 14,302.2 Da native vs 14,498.0 Da, all six lysines plus N-terminus.

What second crystal site was found?

Arg14, besides the Lys116-Me2 cage.