8 research outputs found
Twin-plate Ice Nucleation Assay (TINA) with infrared detection for high-throughput droplet freezing experiments with biological ice nuclei in laboratory and field samples
For efficient analysis and characterization of biological ice nuclei under
immersion freezing conditions, we developed the Twin-plate Ice Nucleation Assay
(TINA) for high-throughput
droplet freezing experiments, in which the temperature profile and freezing
of each droplet is tracked by an infrared detector. In the fully automated
setup, a couple of independently cooled aluminum blocks carrying two 96-well
plates and two 384-well plates, respectively, are available to study ice
nucleation and freezing events simultaneously in hundreds of microliter-range
droplets (0.1â40 ”L). A cooling system with two refrigerant
circulation loops is used for high-precision temperature control (uncertainty
â<â0.2 K), enabling measurements over a wide range of temperatures
(ââŒâ 272â233 K) at variable cooling rates (up to 10 K minâ1).The TINA instrument was tested and characterized in experiments with
bacterial and fungal ice nuclei (IN) from Pseudomonas syringae (SnomaxÂź) and Mortierella alpina, exhibiting freezing curves in good agreement with literature
data. Moreover, TINA was applied to investigate the influence of chemical
processing on the activity of biological IN, in particular the effects of
oxidation and nitration reactions. Upon exposure of
SnomaxÂź to O3 and NO2, the cumulative
number of IN active at 270â266 K decreased by more than 1Â order of
magnitude. Furthermore, TINA was used to study aqueous extracts of
atmospheric aerosols, simultaneously investigating a multitude of samples
that were pre-treated in different ways to distinguish different kinds of
IN. For example, heat treatment and filtration indicated that most
biological IN were larger than 5 ”m. The results confirm that TINA is
suitable for high-throughput experiments and efficient analysis of
biological IN in laboratory and field samples.</p