Biology subjects

Lundholm, I.

Publications and source records attributed to Lundholm, I..

2 recordsLinked to original sources

bioRxiv2018

Patterns of anisotropic temperature factors in bovine trypsin crystals with and without 0.5 THz irradiation

Vibrational oscillations in amide and side chain groups are well studied in proteins, but these are not occupied at ambient temperatures and they have a short lifespan when infrared radiation is present. Active vibrational modes in proteins lie in the terahertz (THz) range at physiological temperatures, and their experimental descriptions of them in this range are lacking. In this paper, we present the effect of 0.5 THz irradiation on atomic displacement parameters (ADP) in bovine trypsin. The crystals were subjected to terahertz radiation in an alternating manner and two states of the crystals were recovered using X-ray crystallography. The clustering of ADPs uniquely identified atoms from the different crystals. The ADP similarities tended to develop between chemically similar atoms and between atoms of the catalytic triad. This pattern of ADP similarity is likely created by delocalized polar vibration modes rather than, as frequently assumed, elastic and rigid-body motions.

biophysics↗

bioRxiv2018

Electrospray sample injection for single-particle imaging with X-ray lasers

The possibility of imaging single proteins constitutes an exciting challenge for X-ray lasers. Despite encouraging results on large particles, imaging small particles has proven to be difficult for two reasons: not quite high enough pulse intensity from currently available X-ray lasers and, as we demonstrate here, contamination of the aerosolised molecules by non-volatile contaminants in the solution. The amount of contamination on the sample depends on the initial droplet-size during aerosolisation. Here we show that with our electrospray injector we can decrease the size of aerosol droplets and demonstrate virtually contaminant-free sample delivery of organelles, small virions, and proteins. The results presented here, together with the increased performance of next generation X-ray lasers, constitute an important stepping stone towards the ultimate goal of protein structure determination from imaging at room temperature and high temporal resolution.

biophysics↗