PIPES has two pKa values. One pKa (6.76 at 25°C) is near the physiological pH which makes it useful in cell culture work. Its effective buffering range is 6.1-7.5 at 25° C. The second pKa value is at 2.67 with a buffer range of from 1.5 - 3.5. PIPES has been documented minimizing lipid loss when buffering glutaraldehyde histology in plant and animal tissues. Fungal zoospore fixation for fluorescence microscopy and electron microscopy were optimized with a combination of glutaraldehyde and formaldehyde in PIPES buffer. It has a negligible capacity to bind divalent ions.
Mild detergent extraction of chick brain synaptic plasma membranes followed by gel electrophoresis suggests that synaptic plasma membrane tubulin is an integral component. Although some of the synaptic plasma membrane tubulin might be aggregates, that possibility is not supported by the observation that tubulin aggregates that are added to synaptosomes before synaptic subfractionation do not partition with synaptic plasma membranes during membrane isolation.
