Hydrogen-deuterium exchange of lysozyme. I. Rate constants and pH dependence

Automatic Determination of the Sequential Order of Dynamic Data and Its Application to Vibrational Spectroscopy

For over the past 30 years, generalized two-dimensional correlation spectroscopy has formed an active and widespread research area. One of the most attractive properties of this method is that one can determine the sequential order of signal changes. But the determination of the sequential order has only been done manually for several arbitrarily chosen bands. In this paper, we develop a method to automatically determine the sequential order of all of the band intensity changes, and we applied this method to band changes of vibration spectra. This method will open a door to analyze more complicated signals often seen in life phenomena.

Bottom-up hydrogen deuterium exchange mass spectrometry: data analysis and interpretation

A tutorial review on the fundamentals of HDX-MS with an emphasis on data analysis and interpretation.

Analysis of proton exchange kinetics with time-dependent exchange rate

Mass spectrometry is used to probe the kinetics of hydrogen-deuterium exchange in lysozyme in pH 5, 6 and 7.4. An analysis based on a Verhulst growth model is proposed and effectively applied to the kinetics of the hydrogen exchange. The data are described by a power-like function which is based on a time-dependence of the exchange rate. Experimental data ranging over many time scales is considered and accurate fits of a power-like function are obtained. Results of fittings show correlation between faster hydrogen-deuterium exchange and increase of pH. Furthermore a model is presented that discriminates between easily exchangeable hydrogens (located in close proximity to the protein surface) and those protected from the exchange (located in the protein interior). A possible interpretation of the model and its biological significance are discussed.

The influence of methanol on the interactions of calcium with the pyridine nucleotides

The interactions of calcium with NAD+, NADH, NADP+ and NADPH in a 50% (by volume) methanol/water mixture (pH 7, 25 degrees C) were studied by calorimetry. The association constants for 1:1 complex formation were found to be 6.6 +/- 0.2, 270 +/- 76, 18 +/- 3 and 98 +/- 10 for NAD+, NADH, NADP+ and NADPH, respectively. Comparing these to the association constants for an aqueous system reveals that as the polarity of the solvent system is decreased the interactions involving NAD+, NADP+ and NADPH are all decreased. In contrast, the interaction involving NADH is markedly increased. All the interactions were found to be endothermic.

Water catalysis of peptide hydrogen isotope exchange

The temperature dependence of the hydrogen-tritium and deuterium-hydrogen exchange reactions in poly(DL-alanine) has been reexamined. The results indicate a significant contribution to the observed exchange rates from the water-catalyzed reaction at pD values near pDmin. The activation enthalpy for water-catalyzed deuterium-hydrogen exchange in poly(DL-alanine) is found to be 21 kcal mol-1. As a result, the contribution to the observed exchange rate from the water-catalyzed reaction increases with increasing temperature which in turn leads to broad, shallow pD minima and the appearance of apparent reaction orders with respect to [D+] and [OD-] that are substantially less than first order over an extended range of pD values. The importance of water catalysis in protein hydrogen exchange is demonstrated by a reanalysis of data for the exchange of single protons in bovine pancreatic trypsin inhibitor [Hilton, B.D., & Woodward, C. K. (1979) Biochemistry 18, 5834; Richarz, R., Sehr, P., Wagner, G., & Wüthrich, K. (1979) J. Mol. Biol. 130, 19]. The pD dependence of these protons can be explained in terms of an increased contribution from water catalysis.

A selected bibliography of biomedical and environmental applications of stable isotopes. I--Deuterium 1971-1976

A compilation of selected references to the use of deuterium in biochemical, pharmacological, clinical and environmental applications for the period 1971-1976 is presented. As a further aid, author and subject indices have been compiled.