Pressure dependence of weak acid ionization in aqueous buffers

Neuman, Robert C.; Kauzmann, Walter; Zipp, Adam

doi:10.1021/j100640a025

Cited by 356 publications

(199 citation statements)

References 4 publications

Supporting

Mentioning

193

Contrasting

Order By: Relevance

“…The Tris concentration was 0.05 M or 0.1 M, as specified. Tris salt was chosen for this study since its ionization constant is not altered by pressure [16]. Pressure-induced changes in the ionization states of the protein arise as a direct result of pressure on the protein and do not involve the surrounding solvent, since Tris, regardless of its buffering power, is insensitive to pressure.…”

Section: Methodsmentioning

confidence: 99%

An infrared study of ²H‐bond variation in myoglobin revealed by high pressure

Tilly

Sire

Alpert

et al. 1992

European Journal of Biochemistry

View full text Add to dashboard Cite

A high-pressure Fourier-transform infrared technique was used to probe the evolution of 'H bonds inside the helical segments of myoglobin in relation to p2H, Tris concentration in the medium and iron-ligand nature. The analysis was focused on changes in the conformation-sensitive amide-I' band, reflecting the peptide C = 0 group stretching vibrations coupled to the in-plane N-2H bending and C = N stretching modes. From data obtained under high pressure, the strength of 2H bonds, inside the a-helical segments of the protein at atmospheric pressure, is not simply a function of p2H and salt concentration. At low Tris concentration (50 mM), the strength of these 2H bonds increases with p'H, whereas for a higher Tris concentration (100 mM) this strength is lower at p2H 7 than at p'H 6.0 or 8.5. It is also observed that the azidometmyoglobin molecule exhibits tighter intrahelical interactions and lower sensitivity to pressure than aquametmyoglobin. Information is also presented regarding interhelical interactions in relation to the solvent.Hydrogen bonds play a key role in protein stability [l] and protein dynamics [2, 31. However, in comparison with current knowledge about hydrogen bonds in gases, liquids or crystal lattices, little is known about hydrogen bonds inside proteins. The problem of assignment of collective modes of hydrogen bonds in proteins [4], the factors determining the intra-helical structure with weak or strong hydrogen bonds [5] are difficult to classify. Notable successes among the few high-pressure Fourier-transform infrared studies were performed using the conformation-sensitive amide-I' band [6 -81. This hand represents the C = 0-stretching vibration of the amide groups coupled to the in-plane N-H bending and C = N-stretching modes [9]. The energy of the C = O stretching vibration is primarily determined by the particular structure adopted by the peptide chains. In the case of the myoglobin molecule, the amide-I' band comprises a main helix band near 1650 cm-'and minor bands at 1627-1638 cm-' and 1671 -1675 cmreflecting the interhelical interactions [4].Since H bonds are basically dipoles, it is interesting to study whether or not the H bonds, inside a monomeric molecule such as myoglobin, are an invariant parameter not affected by the pH of the solvent. Investigating the hydrogen-bond network in this protein in solution is of importance, since most of our knowledge about such interactions derives from the crystallized protein. changes in the heme macrocycle [ l l , 121, whereas the crystal structure remains unaltered [13]. Possible 'H-bond-strength variation could accompany ligand binding, whereas the protein conformation would remain roughly unaltered. Extreme pressure, by reducing intermolecular distance, allows the estimation of variation in 'H-bond strength and emphasizes the relationships between protein residues and solvent molecules [7, 141. The relative strength of the 'H-bond interactions in the helical protein segments at atmospheric pressure can be estimated from the relative magni...

show abstract

Section: Methodsmentioning

confidence: 99%

An infrared study of ²H‐bond variation in myoglobin revealed by high pressure

Tilly

Sire

Alpert

et al. 1992

European Journal of Biochemistry

View full text Add to dashboard Cite

show abstract

“…Tris/HCl was chosen as buffer since the concentration of hydrogen ions in this system is almost independent of pressure [14]. The actual paH in 40% ethylene glycol was estimated according to procedures published elsewhere [15].…”

Section: Enzyme and Buffermentioning

confidence: 99%

Effect of solvent, pressure and temperature on reaction rates of the multiheme hydroxylamine oxidoreductase

Balny

Hooper

1988

European Journal of Biochemistry

View full text Add to dashboard Cite

Hydroxylamine oxidoreductase (HAO) of the ammonia-oxidizing bacterium Nitrosomonas catalyzes the oxidation: N H 2 0 H + H 2 0 + HNOz + 2e-+ 2 H'. The heme-like chromophore P460 is part of a site which binds substrate, extracts electrons and then passes them to the many c hemes of the enzyme. Reduction of the c hemes by hydroxylamine is biphasic with apparent first-order rate constants kl and k z . CO binds to ferrous P460 with apparent first-order rate constants, kl,co. In this work we have measured the binding of CO to ferrous P460 of hydroxylamine oxidoreductase and the reduction by substrate of some of the 24 c hemes of the ferric enzyme. These reactions have been studied in water and 40% ethylene glycol, at temperatures ranging from -15°C to 2 0 . 7 T and at hydrostatic pressures ranging over 0.1 -80 MPa. From the measurements, thermodynamic parameters A V* (activation volume), AG*, AH', and AS* have been calculated.CO binding. Binding of CO to ferrous P460 was similar to the binding of CO to ferrous horseradish peroxidase. The change of solvent had only a limited effect on A V* (-30 ml . mol-I), AG", AH* or AS* and did not cause an inflection in the Arrhenius plot or downward displacement of the linear relationship between In kl,co and P at a critical temperature. Binding was exothermic at high temperatures. The response of the binding of CO to solvent, temperature and pressure suggested that the CO binding site had little access to solvent and was not susceptible to change in protein conformation.Fast phase of reduelion of c hemes. Changing the solvent from water to 40% ethylene glycol resulted in a decrease from 90% to 50% in the relative number of c hemes reduced during the fast phase, an increase in activation volume from -3.6 ml . mol-' to 57 ml . mol-' and changes in other thermodynamic parameters. The activation volume increased with decreasing temperature. The Arrhenius plot had a downward inflection at about 0°C and, in water or ethylene glycol, the linear dependence of In kl on P was displaced downwards as the temperature changed from 3.5"C to -15°C.Slow phase of reduction of c hemes. Changing the solvent from water to 40% ethylene glycol resulted in an increase in the relative number of c hemes reduced during the slow phase from 10% to 50%. The activation volume, which was not measurable in water because of the low absorbance change, was -30 ml . mo1-l in ethylene glycol. The activation volume increased with increasing temperature. The Arrhenius plot had a downward inflection at about 0 "C yet the linear dependence of In k2 on P had no downward displacement in this temperature range. At high pressure and low temperatures the rate of heme reduction increased with decreasing temperature. In contrast to the reaction of CO with the substrate site, the results suggested that changes in enzyme conformation imposed by changes in solvent, temperature or pressure affected the rates of intramolecular electron transfer from the substrate site to c hemes.Hydroxylamine oxidoreductase from the ammonia-oxidizin...

show abstract

“…The seed crystals were prepared as follows. A suspension of GI crystals (Hampton Research Co., Ltd., HR7-100), containing 0.91 M ammonium sulfate and 1 mM magnesium sulfate in 6 mM tris hydrochloride buffer (pH = 7.0) (Tris-HCl is known as the most insensitive buffer to pressure) (Neuman et al, 1973), was dissolved (~ 33 mg mL -1 ) and filtered (Suzuki et al, 2002b). Then the filtrate was transferred onto the sapphire window and sealed with an o-ring and a glass slide.…”

Section: Methodsmentioning

confidence: 99%

Protein Crystal Growth Under High Pressure

Suzuki¹

2012

Modern Aspects of Bulk Crystal and Thin Film Preparation

View full text Add to dashboard Cite

Pressure dependence of weak acid ionization in aqueous buffers

Cited by 356 publications

References 4 publications

An infrared study of ²H‐bond variation in myoglobin revealed by high pressure

An infrared study of ²H‐bond variation in myoglobin revealed by high pressure

Effect of solvent, pressure and temperature on reaction rates of the multiheme hydroxylamine oxidoreductase

Protein Crystal Growth Under High Pressure

Contact Info

Product

Resources

About

Pressure dependence of weak acid ionization in aqueous buffers

Cited by 356 publications

References 4 publications

An infrared study of 2H‐bond variation in myoglobin revealed by high pressure

An infrared study of 2H‐bond variation in myoglobin revealed by high pressure

Effect of solvent, pressure and temperature on reaction rates of the multiheme hydroxylamine oxidoreductase

Protein Crystal Growth Under High Pressure

Contact Info

Product

Resources

About

An infrared study of ²H‐bond variation in myoglobin revealed by high pressure

An infrared study of ²H‐bond variation in myoglobin revealed by high pressure