✦ LIBER ✦

Correlation of exchangeable (NH) and nonexchangeable (C2H) histidine resonances in the proton nmr spectrum of ribonuclease A in aqueous solution

✍ Scribed by Dinshaw J. Patel; Clare Woodward; Lita L. Canuel; F. A. Bovey

Publisher: Wiley (John Wiley & Sons)
Year: 1975
Tongue: English
Weight: 539 KB
Volume: 14
Category: Article
ISSN: 0006-3525
DOI: 10.1002/bip.1975.360140507

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✦ Synopsis

The ionization characteristics of the hydrogen-bonded His 12 AT1 proton observed to titrate between 11 to 13 ppm in the nnir spectrum of ribonuclease A in He0 solution are compared with the ionization characteristics of the four histidine CZ protons in the enzyme. Comparison of the pK,'s of the enzyme in HzO and DzO in the absence and presence of cytidine monophosphate (-.5' , -3', and -2') inhibitors, line widths in the presence of Cu I1 at pH 3.6 and 3.6, and chemical shifts in the presence of AgN03 permit a correlation of the exchangeable His 12 N1 proton with the active site histidine Ct proton exhibiting the lower ionization pK,. The histidines with pK. of 5.1 and 5.6 in ribonuclease A in the absence of salt are assigned in this study t o His 12 and His 119, respectively .

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Assignment of the histidine 12-threonine

Assignment of the histidine 12-threonine 45 hydrogen-bonded proton in the nmr spectrum of ribonuclease A in H2O

✍ Dinshaw J. Patel; Lita L. Canuel; Clare Woodward; Frank A. Bovey 📂 Article 📅 1975 🏛 Wiley (John Wiley & Sons) 🌐 English ⚖ 588 KB

## Synopsis Described herein are proton nmr experiments on chemically modified derivatives of riboniiclease A designed to elucidate the origin of an exchangeable resonance, assigned previously to a histidine ring N proton that titrates between 11 to 13 ppm with a pK, of 6.1 in HzO solution. Histid