The MIFETM system 
for non-invasive measurement of specific fluxes in solution near living plant or animal tissue

UTas Biophysics Lab
Shabala Lab
MIFE Research Facility
MIFE user group

Membrane Transport & fluxes
MIFE Key Features
MIFE applications

MIFE theory
 ion flux theory
multivalent ion mobility
ionic mobility values
neutral molecule flux
Methodological isues
H+ flux in buffered media

System requirements
system components



Univ of Tas
Eppendorf NP2

MIFE Key Features  

There are are several major features that, taken together, provide a significant advantage of the MIFE approach over other techniques for flux measurements. These include:
1.    Non-destructiveness. In contrast to many other methods, the MIFE  system 
allows in situ measurements of net ion fluxes, in physiologically realistic conditions.
2.    High spatial resolution. The electrode tip is typically 2-3 m in diameter, which makes it possible to measure net ion fluxes from single cells (Babourina et al. 2000; Shabala et al. 2001b) or protoplasts derived from plant cells (Shabala et al. 1998; Tyerman et al. 2001). Moreover, for some ionophores with high signal-to-noise ratio (such as H+), the electrode tip diameter can be further reduced to 0.8-1.0 
m. As a result, the cell surface can be "mapped" (Shabala et al. 1998; Tegg et al. 2005), providing information about spatial distribution and functional expression of specific ion transporters.
3.    High temporal resolution. The "default" MIFE settings assume electrode movement with 10 sec period. This could be further reduced without difficulty to 2 or 3 sec in some cases. Such high temporal resolution is crucial in studying rapid signaling events at plant membranes. Most other non-invasive techniques operate on a time scale at least one order of magnitude slower. This gives the MIFE technique a unique opportunity to provide insights into very early (and fast) events associated with plant responses to environmental changes.
4.    Duration of measurements. There is essentially no limitation on how long fluxes could be measured from the cell or tissue. The technique is non-invasive, and its application is practically limited only by the lifetime of the ion-selective electrode (typically 15 to 20 h). Moreover, electrodes may be replaced
easily, and measurements resumed after only a few minutes' break. None of the other techniques of the same time resolution (e.g. patch-clamp or fluorescence imaging) provide this opportunity. Due to dye bleaching, fluorescence measurements are usually restricted to a limited number of images being taken. Maintaining a 'gigaseal' for several hours is also a big problem in every patch-clamp study. As for internal ion-selective microelectrodes, their application is limited by the likelihood of electrode being clogged by the dense cytosol after a certain period of time.
5.    Measurement of fluxes of neutral molecules can also be made if the appropriate micro-sensor is available. 
Pang et al. (2006) have used MIFE for this and other systems have also been used in Porterfield's lab (McLamore et al. 2011).
6.    Simultaneous measurements of several fluxes. The possibility of measuring kinetics of fluxes of several ions or neutrals simultaneously, and essentially at the same spot, is important in understanding the underlying ionic mechanisms of cell adaptive responses. By assessing stoichiometry ratios between various ions, valuable information about the membrane transporters involved can be gained. 

MIFE applications: summarised below:

             plant physiology (stress; adaptation; mineral nutrition; photosynthesis; long-distance transport; growth & development; water relations; osmoregulation; hormonal physiology, stomatal physiology, plant movements)

             cell biology (signaling; perception; elicitors)

             ecophysiology (plant responses to abiotic and biotic factors)

             biophysics (properties of ion channels and transporters)

             developmental biology (morpho- and embrio-genesis; polarity)

             functional genomics (in planta studies of specific gene functions; heterologous expression systems)

             agronomy and plant breeding (plant screening for environmental fitness)

             soil science (soil-root interface; heavy metal toxicity; remediation)

             marine biology (algae; phytoplankton; marine biofilms and mats; sediments)

             bryology (physiology and development)

             mycology (factors controlling growth and development)

             food microbiology (effect of food-related treatments on bacteria; food preservation studies; interrelation of pathogenic and probiotic bacteria; biofilms)

             medical microbiology (pathogenic bacteria; bacterial physiology an genetics; host-pathogen interactions)

             environmental microbiology (functional genomics; bioremediation; environmental physiology)

             medical research (screening of new drugs; physiology; pathology)

             human and animal physiology (receptors; signaling; homeostasis)

             toxicology (receptors; selectivity and action spectrum; molecular targets)



Maintained by Ian Newman. Date . University of Tasmania.