New buffer resists pH change, even as temperature drops

Jan 14, 2008

Researchers at the University of Illinois have found a simple solution to a problem that has plagued scientists for decades: the tendency of chemical buffers used to maintain the pH of laboratory samples to lose their efficacy as the samples are cooled. The research team, headed by chemistry professor Yi Lu, developed a method to formulate a buffer that maintains a desired pH at a range of low temperatures.

The study appears this month in Chemical Communications. Scientists have known since the 1930s that the pH of chemical buffers that are used to maintain the pH of lab samples can change as those samples are cooled, with some buffers raising and others lowering pH in the cooling process.

Freezing is a standard method for extending the shelf life of biological specimens and pharmaceuticals, and biological samples are routinely cooled to slow chemical reactions in some experiments. Even tiny changes in the acidity or alkalinity of a sample can influence its properties, Lu said.

“We like to freeze proteins, nucleic acids, pharmaceutical drugs and other biomolecules to keep them a long time and to study them more readily under very low temperatures using different spectroscopic techniques and X-ray crystallography,” Lu said. “But when the pH changes at low temperature, the sample integrity can change.”

Graduate student Nathan Sieracki demonstrated this by repeatedly freezing and thawing oxacillin, a penicillin analog used to treat infections.

“After one freeze-thaw 50 percent of the drug was dead in several of the buffers investigated,” Sieracki said.

Sieracki was able to demonstrate that the loss of activity was due to changes in pH and not a result of the temperature changes.

To find a buffer that would maintain a stable pH at varying temperatures, Sieracki first evaluated the behavior of several commonly used buffers over a range of temperatures. He saw that some buffers became more alkaline at lower temperatures while others grew more acidic.

These observations led to an obvious methodology: “Why don’t we just mix them together"” Sieracki said.

Little by little, he varied the proportions of the combined buffers until he found a formula that exhibited minimal pH changes at a variety of temperatures. Instead of registering changes of 2 or more pH units while cooling, which was typical of some standard buffers, the new formula changed less than 0.2 pH units during cooling, he said.

“We’re canceling out 100-fold changes in proton concentration and bringing them down within an order of magnitude,” Sieracki said.

The creation of a temperature-independent pH (TIP) buffer could have broad implications for new – and previously published – research, Lu said.

“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.”

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.

Source: University of Illinois at Urbana-Champaign

Explore further: New imaging technique finds formation of aluminum alloys to blame for next-gen battery failures

add to favorites email to friend print save as pdf

Related Stories

Living in the genetic comfort zone

Feb 26, 2015

The information encoded in the DNA of an organism is not sufficient to determine the expression pattern of genes. This fact has been known even before the discovery of epigenetics, which refers to external ...

Eero Wi-Fi system aims to conquer dead zones, buffering

Feb 04, 2015

The makers of a sleek-looking white box called Eero are pointing out that this is no router—it's a Wi-Fi system with features that are capable of blanketing every inch of your home with speedy coverage. ...

Predicting plant responses to drought

Feb 10, 2015

A new U.S. Geological Survey study shows how plants' vulnerability to drought varies across the landscape; factors such as plant structure and soil type where the plant is growing can either make them more vulnerable or protect ...

Recommended for you

Understanding nickel catalysis

4 hours ago

Catalysis is a chemical phenomenon that increases the rate of a chemical reaction by spending only a tiny amount of additional substance, called a catalyst. Around 90 percent of all commercially manufactured ...

Video: What does space smell like?

17 hours ago

You can see it through a telescope, or watch a documentary about it, but you can't stick your nose out and take a whiff.

Solar cells get growth boost

22 hours ago

Researchers at the Okinawa Institute of Science and Technology Graduate University's (OIST) Energy Materials and Surface Sciences Unit have found that growing a type of film used to manufacture solar cells ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Graeme
not rated yet Jan 14, 2008
But what is the combination?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.