•  
  •  
 

TESTING A NEW HANGING DROP OSMOMETER**

Abstract

We updated Weatherley's 1960 hanging drop osmometer design for measuring osmolarities of small volume, botanical samples. An osmometer is used for measuring effective solute concentrations and can be used to indirectly quantify interactions between solutes.  We built a functional prototype of the osmometer we designed last year. It is constructed from gas-tight syringes, glass capillary tubing, 3D printed supports, microcentrifuge vials, and parafilm. A smart phone camera and ImageJ software were used to measure solution volumes. We have measured the evaporation of water under different experimental conditions. Our initial findings indicate a precision of volume measurements of less than 70 nL (<0.7% uncertainty). Since this osmometer does not reach equilibrium, osmolarity is determined by kinetic measurements of change in drop size. We are working to generate calibration curves for solutions of known osmolarity. Upon successful calibration of the osmometer, we hope to be able to measure interactions between osmolytes and native proteins and nucleic acids. Few similar measurements have been published. Measurements with commercial instruments are limited in solute choice and concentration. Further, osmolarity is determined either at the freezing point, or on a paper support substrate. This instrument avoids the commercial instrument limitations, allowing for measurements over a wide range of solutes and concentrations uncomplicated by freezing or interactions with the support. After reproducing published osmolyte-biopolymer results, we plan to measure osmolyte-lipid vesicle interactions. Similar measurements have yet to be reported. Another line of exploration may be possible through placing the instrument in a temperature controlled box, measuring interactions over a range of temperatures. The intent of these measurements is to extend and improve predictive and analytical models of osmolyte effects used to help answer many biochemical questions.

Acknowledgements

Middle Georgia State University Department of Natural Sciences and Faculty Develepment Funds

This document is currently not available here.

Share

COinS