Nucleation, ice

There are aspects of cell membranes other than their permeability to water and solutes that also play a critical role in the responses of cells to freezing. The structure of the plasma membrane allows cells to supercool and probably determines their ice-nucleation temperature. The nucleation temperature along with the permeability of membranes to water are the chief determinants of whether cells cooled at... 

Rail, W.F., Mazur, P., McGrath, J.J. (1983). Depression of the ice-nucleation temperature of rapidly cooled mouse embryos by glycerol and dimethyl sulfoxide. Biophys. J. 41, 1-12. 

A new approach to study root exudation of distinct compounds in soil-grown plants uses inoculation of roots with genetically engineered reporter bacteria, which are able to indicate the presence of particular compounds by indicator reactions, such as production of ice-nucleation proteins. This technique has been employed to detect the release of amino acids from roots of soil-grown A vena harbata (56). 

Recent studies have further examined the iron stress response of pseudomonads using an iron-regulated, ice-nucleation gene reporter (inaZ) for induction of the iron stress response (17,18,84). This particular reporter system was developed by Loper and Lindow (85) for study of microbial iron stress on plant surfaces but was later employed in soil assays. In initial. studies, cells of Pseudomonas fluorescens and P. syringae that contained the pvd-inaZ fusion were shown to express iron-responsive ice-nucleation activity in the bean rhizosphere and phyllosphere. Addition of iron to leaves or soil reduced the apparent transcription of the pvd-inaZ reporter gene, as shown by a reduction in the number of ice nuclei produced. 

In concurrent research involving a longer-term study, the P. fluorescens Pf-5 strain was inoculated into soil used to grow lupine (Lupinus aihus) and barley Hordeum vulgare L.) over a several-week, period (17). It was shown that iron stress was greatest in the zone behind the root tips as compared to older root zones and in the bulk soil. Calibration of the ice-nucleation reporter activity... 

J. E. Loper and M. D. Henkels, Availability of iron to Pseudomonas fliiorescens in rhizosphere and bulk soil evaluated with an ice nucleation reporter gene. Appl. Environ. Microbiol. 63 99 (1997). 

A technique utilizing genetically modified bacteria to report the presence of particular compounds in soil has also been developed (37). These bacteria respond to the presence of specific compounds in their environment by producing ice-nucleation proteins that enter into cell membranes, enabling cells to be detected by means of a droplet freezing assay. The presence of trytophan in 1-10 i molar concentrations has been detected using reporter bacteria in a study examining loss of amino acids from roots of Avena barbata into soil (38). 

How does the presence of ice-nucleating protein affect the freezing point of water ... 

Compare the freezing points of distilled water and distilled water containing ice-nucleating bacteria. 

Form a hypothesis about the effect an ice-nucleating protein will have on the freezing temperature of water. Record your hypothesis on page 98. 

Pour 10 mL of distilled water into the test tube and then use a spatula to add 4 or 5 granules of ice-nucleating protein to the water. 

Jung, H.C., Lebeault, J.M. and Pan, J.G. (1998) Surface display of Zymomonas mobilis levansucrase by using the ice-nucleation protein of Pseudomonas syringae. Nature Biotechnology, 16, 576-580. 

Jung, H.C., Park, J.H., Park, S.H. et al. (1998) Expression of carboxymethylcellulaseonthe surface of Escherichia coli using Pseudomonas syringae ice nucleation protein. Enzyme and Microbial Technology, 22, 348-354. 

Shimazu, M., Mulchandani, A. and Chen, W. (2001) Cell surface display of organophosphorus hydrolase using ice nucleation protein. Biotechnology Progress, 17, 76-80. 

Burke, M. Lindow, S. E. Surface properties and size of the ice nucleation of active bacteria Theoretical considerations. Cryobiology 27, p. 80-84, Copyright 1990 by Academic Press Inc. 1990... 

Conformations of Five- and Six-Membered Ring Forms 191 Box4-D Antifreeze and Ice-Nucleation Proteins... 

Bis(acetylacetonato)copper has been used as a source of copper in copper-vapour lasers,97 and it has been investigated as a substitute for silver iodide as an ice-nucleating agent for the initiation of rainfall.98... 

When ice cream starts to freeze, ice nucleation begins and water will freeze out of the solution in the form of pure crystals. As water is removed from the mix in the form of ice, the concentration of dissolved solids in solution increases. The unfrozen portion of the mix becomes increasingly concentrated as freezing continues, and contains dissolved sugars, milk... 

Zachariassen, K.E., Ice Nucleating Agents in Cold-Hardy Insects, Springer-Verlag, Berlin (1982). 

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