Buffer cocktail maintains pH when freezing
stay at the right pH, even when frozen and the discovery could
bring into doubt previously published research.
Professor Li Yu and his team at the University of Illinois developed a method of formulating a buffer that retains its efficacy at low temperatures.
Normally, the pH of the buffer itself changes up or down when temperature drops, which can ruin a carefully prepared sample.
Freezing is often used to extend the shelf life of both biological specimens and pharmaceuticals.
This then enables the researchers to more readily study them using different spectroscopic techniques and X-ray crystallography.
However, as Prof. Yu explained, even tiny changes in the acidity or alkalinity of a sample can influence its properties, and this, in turn, could lead to misleading results.
"We're not in the business of looking at the literature and correcting other mistakes," he said.
"But some of the conclusions from previous studies could be on shaky ground if a buffer was used that changed pH dramatically at low temperatures."
One of the members of the lab, graduate student Nathan Sieracki, set out to show just how big an effect a poor buffer can have in experiments where temperature is changed.
He froze and then thawed a sample of oxacillin, a penicillin analogue used to treat infections, and observed that half the drug was destroyed in several of the buffers investigated.
Sieracki realised that during cooling, some buffers become more alkaline and some become more acidic.
He then asked himself the obvious question: "Why don't we just mix them together?"
By varying the proportions in a buffer cocktail, he eventually found one that changed less than 0.2 pH units during cooling, rather than a change of two or more pH units seen with a single buffer alone.
"We're cancelling out 100-fold changes in proton concentration and bringing them down within an order of magnitude," Sieracki said.
The new buffer is immediately useful for biological research, and Sieracki said he is confident that a similar buffer could be made for use in many fields, such as biochemistry, biophysics, chemical biology and biomedical research.
Their technique is described in the latest edition of the Chemical Communications journal.
