LR White Resin, Uncatalysed

C023 & C024

LR White resin is supplied uncatalysed; with the catalyst (Benzoyl Peroxide) supplied 9.9g in a separate tube. LR White (catalysed) should be kept at 4°C or lower. In our experience, the shelf-life of LR White is a minimum of one year @ 4°C, and up to 15 months if stored as low as -80°C. If the resin is frozen, allow it to thaw and reach room temperature prior to use. If the viscosity of the LR White resin changes (becomes thicker), stop and do not use it.

LR White can be polymerised by four different methods:

1. Heat: 60 – 65°C
2. UV irradiation (365nm wavelength)
3. Chemical with accelerator
4. Microwave

Mixing LR White Resin with Catalyst (Benzoyl Peroxide):

All of the catalyst should be added to resin at room temperature and the resin must be shaken vigorously for a couple of minutes. 

There have been incidents where a whole bottle hardened. It must be understood that much of the catalyst will dissolve within an hour, but if after initial shaking the bottle is left without occasional inverting, and then the catalyst settles and initiates an exothermic reaction. The heat further accelerates the reaction and an hour later the whole bottle may be very hot and solid. To avoid this:

• Manually invert the bottle frequently every few minutes at first, increasing to every ten minutes.
• Using a magnetic stirrer, but never use heat. Ensure that the magnet is stirring and not just sitting at the edge of the bottle.
• If a slow rotator or shaker is available (not in a hot room) squeeze most of the air from the bottle after the catalyst is added, lay the bottle on the side, then rotate for a couple of hours. 

Refrigerate the bottle after about three hours (two hours is sufficient if it had been mechanically agitated). Usually it takes 12 hours at room temperature and 12 hours in the refrigerator for catalyzed LR White resin to take effect prior to use. Do not attempt to heat the resin in order to speed the dissolution of the catalyst. Once mixed and fully dissolved the resin must be stored at 4°C to maintain its shelf life.

Freshly catalysed and thoroughly oxygenated resin may take a little longer than normal to polymerise. Following the addition of the catalyst, a test aliquot should be polymerised at 60°C for twenty-four hours as a quality control measure.

We do not advise catalysing less than 500g (one full bottle) of LR White resin as it can be difficult to accurately measure smaller quantities of the reagents. LR White resin with insufficient catalyst will normally polymerise by thermal curing eventually, though curing times may be protracted. Uncatalysed LR White with accelerator only added may only cure to a gel.

References

Fixation

• Ito, S. and Karnovsky, M.J. (1968) Formaldehyde/Glutaraldehyde fixative containing trinitro compounds. J. Cell Biol. 39, 168a :169a.
• McLean I.W. and Nakanem P.K. (1974) Peroxidaselysin paraformaldehyde fixative, a new fixative for immunoelectron microscopy. J. Histochem, 22, 1077: 1083
• Smogyi P. and Takagi H. (1982) A note on the use of picric acid/paraformaldehyde/glutaraldehyde fixative for correlate light and electron microscopic immunocytochemistry. Neurosciences, 7, 1779:1783
• Stefanini, M., De Martino, C and Zamboni, I. (1967) Fixation of ejaculated spermatozoa for electron microscopy. Nature 216, 173:174.

Fixation and Embedding in L.R. White

• Newman, G.R. Jasani, B. and Williams, E.D. (1982) The preservation of ultrastructure and antigenicity. J. Microscopy, 127, RP5:RP6.
• Newman, G.R. Jasani, B. and Williams, E.D. (1982) A simple post embedding system for the rapid demonstration of tissue antigens under the electron microscope. Histochem. J. In press.
• M.A. Hayat. Principles, Methods and applications, Volume 2. , ed. Academic Press, Inc. New York, pp. 38:71.
• J.N. Skepper and J.M. Powell. 2008a.Ultrastructural Immunochemistry (Immunostaining of London Resin(LR) White section for TEM). CSH Protocols doi:1101/pdb.top47 [Abstract/Free Full Text]

Immunostaining

De May, J., Moeremans, M., Geuens, G., Nuydens, R. and De Brabander, M, (1981). High resolution light and electron microscopic localization of tubulin with the IGS (Immuno gold staining) method. Cell Biol. Int. 5, 889 :899.

Hsu, S.M., Raine, L, and Fanger, H. (1981) The use of avidin-biotin-peroxidase complex (ABC) in immunoperoxidase techniques: a comparison between ABC and unlabelled antibody (PAP) procedures. J. Histochem. Cytochem. 29, 577 : 580.