Measurement of the pH of Frozen Buffer Solutions by Using pH Indicators

Orii, Yutaka; Morita, Masayuki

doi:10.1093/oxfordjournals.jbchem.a131431

Cited by 95 publications

(58 citation statements)

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“…In this latter study, it was shown that the pH upon freezing of a citrate buffer increased slightly from 6 to 6.4 [27]. Similar findings were observed with a pH indicator study, which showed no pH change for citric acid/ sodium citrate pH 5.5 during freezing [34]. Lastly, a concentration study from 0.1 to 0.6 molal showed no significant change in pH for citrate buffers at pH 6 and 4.4 [5].…”

Section: Carboxylic Acid Bufferssupporting

confidence: 76%

“…Indirect methods can be divided into two categories, one is based on detecting crystallization of buffer components (low-temperature X-ray diffractometry (XRD) [8,17,38], sub-ambient thermal analysis [10], differential scanning calorimetry (DSC) [32], scanning electron microscopy [33]), and the other monitoring changes in the ionization of ionizable groups (e.g., using pH indicators as probe molecules [34] and measuring the extent of proton transfer either in probe molecules by visible diffuse reflectance spectroscopy or in a buffer itself by Raman spectroscopy [28]). …”

Section: Characterization Methodsmentioning

confidence: 99%

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Advance Understanding of Buffer Behavior during Lyophilization

Shamblin

Varshney³

et al. 2015

Lyophilized Biologics and Vaccines

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Section: Carboxylic Acid Bufferssupporting

confidence: 76%

Section: Characterization Methodsmentioning

confidence: 99%

Advance Understanding of Buffer Behavior during Lyophilization

Shamblin

Varshney³

et al. 2015

Lyophilized Biologics and Vaccines

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“…18 Consideration must always be taken to separate low temperature effects on the probe itself from those inferred as pH changes.…”

mentioning

confidence: 99%

A temperature independent pH (TIP) buffer for biomedical biophysical applications at low temperatures

et al. 2008

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A temperature independent pH buffer has been develeloped from combination of buffers of oppositesign temperature coefficients, and utility in low temperature spectroscopy and storage of pH sensitive compounds is demonstrated.Storage and analysis of samples at low and cryogenic temperatures has become a routine practice in modern research, as these temperatures can preserve integrity of precious samples, and allow modern biophysical and bioanalytical techniques to provide information on biomolecules at an unprecedented level. [1][2][3][4][5][6][7] Buffers are invariably used in the sample storage and analysis process. It is widely known that the pH of a buffer solution can change at low temperatures, and this has been ascribed to enthalpic effects on the proton equilibrium as well as selective precipitation of buffer components upon cooling. [8][9][10][11] If left unaccounted for, these pH changes could lead to demage to the samples and erroneous conclusions about biomolecular structures and dynamics at physiological temperature.About 75 years ago, Finn and coworkers reported the denaturation of proteins contained in muscle juice due to the variation in hydrogen ion and salt concentrations upon freezing. 12 Thereafter, activity loss of aldolase, phosphofructokinase and several dehydrogenases in sodium and potassium phosphate buffer at lower temperatures has been observed and ascribed to pH effects. 13,14 Several strategies have been applied to measure the temperature-dependent pH characteristics, such as the measurement of electromotive force (emf) to determine temperature dependence of pK a values, or the use of pH-sensitive dyes to probe protonic activity at low temperatures. [15][16][17][18] It was reported that EPR (electron paramagnetic resonance) based estimates of apparent pH change from the observation of several pH-sensitive systems (such as the flavin adenine dinucleotide semiquinone radical (FADH•) in xanthine oxidase) coincide well with estimates based on indicator dye optical changes. 19 Despite broad awareness, and extensive research into the relevance and merits of cryotemperature studies on biological systems, 20, 21 no reports of strategies to obtain buffers that resist temperature-dependent pH changes have appeared in the literature. Here we address this long standing problem through combination of buffers exhibiting an increase in pH upon freezing with those exhibiting a decrease. The utility of these temperature-independent-pH (TIP) buffers in preserving the sample integrity upon freezing of pH-sensitive pharmaceutical drugs, and in spectroscopic studies of human methemoglobin (met-Hb) is also demonstrated. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptTo obtain the TIP buffer, the apparent pH changes of the two commonly used buffers, (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and potassium phosphate) and mixtures thereof were first measured at low temperature via ratiometric absorption spectroscopy. A 1:1 mixture of two pH-indicator dyes (b...

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“…There is evidence indicating that some buffer solutions have a pH change upon freezing. 7 ) Although no direct evidence to prove such a pH change was obtained in this case, there is a possibility that the pH change in the liquid regions in ice may also be involved in the acceleration of the transhydrogenation between the nucleotides in the frozen state. This is under investigation to elucidate the mechanism of this reaction.…”

mentioning

confidence: 78%