Triplet state of tryptophan in proteins: the nature of the optically detected magnetic resonance lines

Abstract

Optical detection of magnetic resonance (ODMR) has been employed to examine the homogeneity of the tryptophan environment, both of the isolated residue in solvent, and of tryptophan in glucagon and lysozyme and azurin B (Pseudomonas aeruginosa). From the shifts in the zero-field splittings, we can safely conclude that tryptophan in lysozyme, azurin B, or glucagon does not have the same type of solvent interaction as the free residue. However, by "burning holes" in the OSMR lines, it is evident that the lines in these cases are inhomogeneously broadened. From the relative line widths and hole widths, it appears that ODMR can be used to examine the relative diversity of interactions for a luminescent amino acid in a protein. We have followed the ODMR line characteristics in a progression from free N-acetyl-L-tryptophanamide, to tryptophan in lysozyme, to "denatured" lysozyme, and present evidence that the line widths narrow as the tryptophan residues become less solvent accessible.

Optically detected magnetic resonance of tryptophan triplet states in native and urea-denatured proteins and polypeptides

“…It is not clear from these results whether the tryptophan residue itself plays an essential role in the folding process. However, we were able to ascertain that the tryptophan triplet state zfs and phosphorescence are sensitive to changes in the local structure of polypeptides and proteins and that the widths of the optically detected magnetic resonance (ODMR) lines in the tryptophan triplet state depend intimately upon the local environment of the residue (Rousslang et al, 1978;Deranleau et al, 1978). We also examined the effect of guanidine hydrochloride denaturation upon lysozyme, an enzyme with six tryptophan residues (Rousslang et al, 1978).…”

Long-lived spin-polarized intermolecular exciplex states in thermally activated delayed fluorescence-based organic light-emitting diodes

“…The width of the dip is associated to the energetic span of the sublevels in the energy diagram (Fig. 2A) (26,27,(30)(31)(32)(33)(34)(35). In Fig.…”

“…For this purpose, a two-frequency hole-burning experiment is used, which pumps and saturates the spin system at a fixed frequency during the second probe frequency sweep (26)(27)(28)(29). This pump-probe method allows not only the separation and addressing of individual spin packets in the inhomogeneously broadened ELDMR spectrum but also the observation of coherent population oscillations (CPOs), which are observed as spikes with a very narrow linewidth (26)(27)(28)(29)(30)(31)(32)(33)(34)(35). The hole-burning effect is caused by decoupling of the triplet exciplex spin state from the heterogeneous molecular environment, while the CPO can be described as a two-level quantum system oscillating with the beat frequency between pump and probe.…”

Near Uv‐induced Free Radicals in Ocular Lens, Studied by Esr and Spin Trapping

“…Although the X-ray structural analysis of gamma-I1 crystallin is now available (Wistow et ul., 1983), it is too early to postulate the exact mechanism of the free radical production in UV-irradiated lens. According to Wistow et al (1983) environment for the individual tryptophans in gamma-I1 crystallin are different from each other; therefore (i) the characteristics of the tryptophan triplet state must be dissimilar, as already shown with the other proteins by optically detected magnetic resonance at low temperature (Zuclich et ai., 1973;Rousslang et al, 1978) and by life time measurement at room temperature (Kai and Imakubo, 1979;Vanderkooi ef al., 1987); and (ii) among four tryptophan residues of gamma-I1 crystallin, for example, some can interact directly with cysteine residues but others cannot.…”