Avoiding Interferences from Good's Buffers: A Contiguous Series of Noncomplexing Tertiary Amine Buffers Covering the Entire Range of pH 3–11

Yu, Qiuyue; Kandegedara, Ashoka; Xu, Yang; Rorabacher, D. B.

doi:10.1006/abio.1997.2349

Cited by 174 publications

(136 citation statements)

References 35 publications

(3 reference statements)

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“…When Tris was replaced by 50 m m MOPS, cleavage of PFHSPAY still took place although the rate was reduced by approximately 18%. MOPS is a goods buffer and is noted for not forming metal complexes (Yu et al ., 1997). …”

Section: Resultsmentioning

confidence: 99%

Spontaneous cleavage of proteins at serine and threonine is facilitated by zinc

2016

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SummaryOld proteins are widely distributed in the body. Over time, they deteriorate and many spontaneous reactions, for example isomerisation of Asp and Asn, can be replicated by incubation of peptides under physiological conditions. One of the signatures of long‐lived proteins that has proven to be difficult to replicate in vitro is cleavage on the N‐terminal side of Ser residues, and this is important since cleavage at Ser, and also Thr, has been observed in a number of human proteins. In this study, the autolysis of Ser‐ and Thr‐containing peptides was investigated with particular reference to discovering factors that promote cleavage adjacent to Ser/Thr at neutral pH. It was found that zinc catalyses cleavage of the peptide bond on the N‐terminal side of Ser residues and further that this process is markedly accelerated if a His residue is adjacent to the Ser. NMR analysis indicated that the imidazole group co‐ordinates zinc and that once zinc is co‐ordinated, it can polarize the carbonyl group of the peptide bond in a manner analogous to that observed in the active site of the metalloexopeptidase, carboxypeptidase A. The hydroxyl side chain of Ser/Thr is then able to cleave the adjacent peptide bond. These observations enable an understanding of the origin of common truncations observed in long‐lived proteins, for example truncation on the N‐terminal side of Ser 8 in Abeta, Ser 19 in alpha B crystallin and Ser 66 in alpha A crystallin. The presence of zinc may therefore significantly affect the long‐term stability of cellular proteins.

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Section: Resultsmentioning

confidence: 99%

Spontaneous cleavage of proteins at serine and threonine is facilitated by zinc

2016

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“…Tris forms coordination complexes with transition metal ions with equilibrium constants in the range of 100 -10,000 (40), and sulfhydryls are well known to coordinate metal ions strongly (47). In contrast, MOPS buffer does not form stable metal ion complexes (48,49).…”

Section: Discussionmentioning

confidence: 99%

Metal Ion Substrate Inhibition of Ferrochelatase

Hunter

Sampson

Ferreira

2008

Journal of Biological Chemistry

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Ferrochelatase catalyzes the insertion of ferrous iron into protoporphyrin IX to form heme. Robust kinetic analyses of the reaction mechanism are complicated by the instability of ferrous iron in aqueous solution, particularly at alkaline pH values. At pH 7.00 the half-life for spontaneous oxidation of ferrous ion is approximately 2 min in the absence of metal complexing additives, which is sufficient for direct comparisons of alternative metal ion substrates with iron. These analyses reveal that purified recombinant ferrochelatase from both murine and yeast sources inserts not only ferrous iron but also divalent cobalt, zinc, nickel, and copper into protoporphyrin IX to form the corresponding metalloporphyrins but with considerable mechanistic variability. Ferrous iron is the preferred metal ion substrate in terms of apparent k cat and is also the only metal ion substrate not subject to severe substrate inhibition. Substrate inhibition occurs in the order Cu 2؉ > Zn 2؉ > Co 2؉ > Ni 2؉ and can be alleviated by the addition of metal complexing agents such as ␤-mercaptoethanol or imidazole to the reaction buffer. These data indicate the presence of two catalytically significant metal ion binding sites that may coordinately regulate a selective processivity for the various potential metal ion substrates.

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“…These buffers do not reveal an affinity towards the copper(II) ions [22][23][24]; therefore, they do not affect the copper(II)-ligand binding constant. For this reason, K ITC is not conditioned by the buffer competition with the ligand (bicine) for the metal (Cu 2? )…”

Section: Resultsmentioning

confidence: 99%

Buffer contribution to formation enthalpy of copper(II)–bicine complex determined by isothermal titration calorimetry method

Tesmar

Wyrzykowski

Jacewicz

et al. 2016

J Therm Anal Calorim

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The isothermal titration calorimetry (ITC) technique supported by potentiometric titration data was used to study a buffer contribution to the formation enthalpy of copper(II)-bicine complex obtained directly from the ITC experiments. The calorimetric measurements were carried out at 298.15 K in 100 mM buffer solutions with a pH of 6. In experiments two biologically relevant pH buffers were used, namely Mes and Caco. These buffers do not bind copper(II) ions and thus do not affect the binding constant. However, due to their different ionization enthalpy, they affect the conditional (observed) enthalpy of binding of the metal ion to a ligand owing to the proton transfer during the interactions. To calculate the conditional-independent binding enthalpy DH, the equation based on the Hess's law was used. Furthermore, pH-independent and buffer-independent parameters (K, DG and DS) of the interactions were calculated as well. The relationship between the ionization enthalpy of the buffer components and the thermodynamic parameters has been discussed.

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Avoiding Interferences from Good's Buffers: A Contiguous Series of Noncomplexing Tertiary Amine Buffers Covering the Entire Range of pH 3–11

Cited by 174 publications

References 35 publications

Spontaneous cleavage of proteins at serine and threonine is facilitated by zinc

Spontaneous cleavage of proteins at serine and threonine is facilitated by zinc

Metal Ion Substrate Inhibition of Ferrochelatase

Buffer contribution to formation enthalpy of copper(II)–bicine complex determined by isothermal titration calorimetry method

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