Ribonucleotide reductase (RNR) is an essential enzyme that converts ribonucleotides to
deoxyribonucleotides and is a promising antibiotic target, but few RNRs have been
structurally characterized. We present the use of the chameleon, a commercially-available
piezoelectric cryogenic electron microscopy plunger, to address complex denaturation in the
Neisseria gonorrhoeae class Ia RNR. Here, we characterize the extent of denaturation of the
ring-shaped complex following grid preparation using a traditional plunger and using a …

The chameleon (SPT Labtech; based on the NYSBC SpotItOn) utilizes a picoliter spraying
method to dispense a thin stripe of sample onto self-wicking cryo-electron microscopy (cryo-
EM) grids. This method allows for extremely fast (as fast as 54 ms) dispense-to-plunge (D2P)
times. The fast D2P timing, combined with the unique physics of spraying and wicking, has
opened a new pathway for difficult samples that display preferred orientation or complex
denaturation at the air/water interface. Here, we present a case study utilizing the …