Tyrosine doublet

As well as providing a means of measuring 1 H/2H-exchange in proteins, NMR is a most powerful technique for studying the mobility of individual amino acids. For example, the rotational freedom of the aromatic side chains of tyrosine and phenylalanine about the C 3—Cy bond is readily studied by various NMR methods. ]H NMR can detect whether or not the aromatic ring is constrained in an anisotropic environment. In an isotropic environment or where there is rapid rotation on the NMR time scale, the 3 and 5 protons of phenylalanine and tyrosine are symmetrically related, as are the 2 and 6 (structures 1.12). The resultant spectrum is of the AA BB type, containing two pairs of closely separated doublets. But if there is slow rotation in an anisotropic environment, the symmetry breaks down to give four separate resonances (an ABCD spectrum), since the 5 and 6 protons are in different states from the 2 and 3. At an intermediate time... 

In contrast to aging, lens opacification (cataract formation) is characterized by (1) the intensity increase of the v(OH) at 3,390 cm-1, and (2) the change in relative intensity of the tyrosine (Tyr) doublet near 840 cm-1. (1) is a better marker of opacification because the change is larger and observable even in precataractous stage (38). 

Using the 830/850 cm doublet as a measure of the negative state of phenolic oxygen and of the tyrosine environment. Van Dael et al. (1987) studied the effect of low pH on bovine a-lactalbumin Tyr groups. They also examined the stabilizing role of Ca(II) and Na(I) on the structure and the change in state of Trp residues as the molecule unfolds. 

Figure 14 Signal improvement by multi-flash CIDNP experiments with storage and accumulation in the spin system. Delay At (see, Figure 13) between laser flash and sampling rf pulse, 0 jis. Bottom trace absorptive doublet and emissive AB spin system of 3-fluoro-DL-tyrosine. Top trace multiplet effect in S-NADH. The number of flashes accumulated before one acquisition is given at the upper spectra, 1 denoting the control experiment with the standard sequence of Figure 9. It is seen that neither multiplet signals nor CIDNP multiplet effects are distorted by the method. Further explanation, see text. Adapted from Ref. 75 with permission copyright (2006) Taylor Francis Ltd, http / www.tandfco.uk/journals.

Grangeasse, C. Doublet, R Cozzone, A.J. Tyrosine phosphorylation of protein kinase Wzc from Escherichia coli K12 occurs through a two-step process. J. Biol. Chem., 277, 7127-7135 (2002)... 

Vincent, C. Doublet, P. Grangeasse, C. Vaganay, E. Cozzone, A.J. Duclos, B. Cells of Escherichia coli contain a protein-tyrosine kinase, Wzc, and a phosphotyrosine-protein phosphatase, Wzb. J. BacterioL, 181, 3472-3477 (1999)... 

The contribution of the methylene protons will dominate the spectrum of the 3,5 deuterated tyrosine radical (Figure 2C, Figure 3C). In both the in vivo and the in vitro case, we observe a doublet spectrum, indicating that, in each case, only one methylene proton has a large hyperfine coupling. The in vivo spectrum is a poorly-resolved doublet with a 16G total linewidth in the in vitro case, the width of the well-resolved doublet is 21G. Simulations of these spectra are in progress. By contrast, the doublet observed when 3,5 deuterated tyrosine is substituted into RDPR has a linewidth of 406 (14,15). 

Figure 6. (a) Aromatic region of the 360 MHz nmr spectrum of 1 5 X 10 N rlbonuclease A In P2O, pH = 7.0, 38 0, 2000 pulses. The resolution Is Increased by multiplication of the FID by a sine bell, (b) photo-CIWP difference spectrum of BNase A (25 pulses), (c) photo-CIDNP difference spectrum of BNase S (same conditions). Pairs of doublets Indicated by Yl, Y2 and Y3 belong to tyrosines. 

Figure 6a shows the aromatic part of the 360 MHz spectrum of bovine pancreatic rlbonuclease A (1.5 idH In D2O, pH 7.0, 38%). The spectral resolution was artificially enhanced by multiplication of the FID by a sine bell (HOthrlch et al., 1977). The spectrum of RNase S Is very similar. The doublet resonances of three of the six tyrosine residues Indicated by Yl, Y2, and Y3 have been Indentlfled by double resonance methodes (Lenstra et al., 1978). The photo-CIDNP difference spectra of RNase A and RNase S taken under the same conditions are shown In Figure 6b and 6c. Positively enhanced lines at 7.92 ppm and 6.71 ppm belong to the C-2 and C-4 protons of His 119. This active site residue Is also the most exposed of the four histidines as judged from the X-ray structure (Richards and Wyckoff, 1971) For RNase A (figure 6b)... 

Figure 3. Changes in the normalized intensity of bands in the Raman spectra of 15% a-lactalbumin in deuterium oxide containing 20 mM NaCl (pD pp = 6.8) upon formation of transparent gels as a function of heating time at 90°C. The bands are assigned to vibrational motions of amino acid side chains as follows (a) 508 cm (S-S) (b) 760 cm band (tryptophan) (c) 850 cm /830 cm doublet (tyrosine). Error bars represent the standard deviation for three replicate samples, with 8 spectral scans averaged per replicate. (Adapted from Nonaka et al, 1993).

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