Photo‐cidnp of the Amino Acids

Stob, S; Kaptein, Robert

doi:10.1111/j.1751-1097.1989.tb08425.x

Cited by 53 publications

(66 citation statements)

References 31 publications

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“…The reactivity of histidine residues appeared to be on average smaller than expected on the basis of the calculated accessibility. As already alluded to above, it has to be emphasised that the reactivity of histidine towards triplet flavin is two orders of magnitude lower than that of tyrosine or tryptophan (Heelis et al, 1979;Muszkat and Wismontski-Knittel, 1985;Stob and Kaptein, 1989). Moreover, deliberate pD titrations and CIDNPmonitoring can determine the actual share of His residues in the part of the spectrum which is characteristic for a His/Trp signal, as shown herein.…”

Section: Discussionmentioning

confidence: 99%

Involvement of Laser Photo‐CIDNP(Chemically Induced Dynamic Nuclear Polarization)‐Reactive Amino Acid Side Chains in Ligand Binding by Galactoside‐Specific Lectins in Solution

Sieber

Adar

Arango

et al. 1997

European Journal of Biochemistry

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For proteins in solution the validity of certain crystallographic parameters can be ascertained by a combination of molecular-dynamics (MD) simulations and NMR spectroscopy. Using the laser photo-CIDNP (chemically induced dynamic nuclear polarization) technique as a measure for surface accessibility of histidine, tyrosine and tryptophan, the spectra of bovine galectin-I and Erythrina corallodendron lectin (EcorL) are readily reconcilable with the crystallographic data for these two proteins. The results emphasise the role of Trp68/Trp69 for carbohydrate binding in bovine galectin-l/chicken galectins and of Trp194 in murine galectin-3. This feature derived from the crystal structure of' bovine galectin-I is maintained in solution for the prototype human homologue, two avian galectins and the chimera-type murine galectin-3, as the spectra corroborate the CIDNP-inferable spatial parameters of the four calculated models for binding-site architecture. In EcorL, Tyr106/Tyr108 are constituents of the extended combining pocket, which can be shielded in solution by ligand presence. Discrepancies between results from modelling and CIDNP measurements concern primarily the lack of reactivity of histidine residues for human and avian prototype galectins and of Tyr82lTyr229 of the plant lectin. Site-directed mutagenesis of EcorL is assumed to provide information on the role of a certain residue for functional aspects. When singlesite mutants of EcorL ([Alal06]EcorL, [Alal08]EcorL, [Ala229]EcorL) were subjected to moleculardynamics (MD) simulations, the apparent surface accessibilities even of spatially separated amino acid side chains could non-uniformly be affected. This conclusion is supported by the assessment of the spectra for the mutant proteins. On the basis of these CIDNP-results modelling of the binding-site architecture of the lectin indicates the occurrence of notable alterations in the orientation of Tyr106/Tyr108 phenyl rings. The implied potential effect of single-site mutations on conformational features of a protein will deserve attention for the interpretation of studies comparing wild-type and mutant proteins.Keywords: galectin ; lectin ; Erythrina agglutinin ; NMR; molecular modeling.X-ray crystallography of proteins provides detailed information on three-dimensional structure. The precision of the derived spatial parameters of the protein in the crystal, however, should not be considered as proof for the solution structure. Among other factors, the often applied non-physiological conditions to favour crystal growth and the intermolecular interactions during packaging may lead to deviations from the solution structure(s) especially for surface group features (Wagner et al., 1992;MacArthur et al., 1994). Consequently, it is desirable to employ a sensitive spectroscopic method which in combination with mo- lecular-dynamics (MD) simulations can verify the applicability of distinct properties determined by crystallographic analysis for the solution structure. With a focus on surface epitopes, whose mobility can...

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Section: Discussionmentioning

confidence: 99%

Involvement of Laser Photo‐CIDNP(Chemically Induced Dynamic Nuclear Polarization)‐Reactive Amino Acid Side Chains in Ligand Binding by Galactoside‐Specific Lectins in Solution

Sieber

Adar

Arango

et al. 1997

European Journal of Biochemistry

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“…Only one hyperpolarization technique – photo‐CIDNP – enables hyperpolarization of 19 F directly in pure water ,,. The effect is based on irradiation of light (usually by a laser) and induces reversible photochemical reactions due to excitation of a photosensitizer, leading finally to hyperpolarized nuclei via hyperfine interactions.…”

Section: Figurementioning

confidence: 99%

Low‐cost LED‐based Photo‐CIDNP Enables Biocompatible Hyperpolarization of ¹⁹F for NMR and MRI at 7 T and 4.7 T

et al. 2018

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Substrates containing 19F can serve as background‐free reporter molecules for NMR and MRI. However, in vivo applications are still limited due to the lower signal‐to‐noise ratio (SNR) when compared with 1H NMR. Although hyperpolarization can increase the SNR, to date, only photo‐chemically induced dynamic nuclear polarization (photo‐CIDNP) allows for hyperpolarization without harmful metal catalysts. Photo‐CIDNP was shown to significantly enhance 19F NMR signals of 3‐fluoro‐DL‐tyrosine in aqueous solution using flavins as photosensitizers. However, lasers were used for photoexcitation, which is expensive and requires appropriate protection procedures in a medical or lab environment. Herein, we report 19F MR hyperpolarization at 4.7 T and 7 T with a biocompatible system using a low‐cost and easy‐to‐handle LED‐based set‐up. First hyperpolarized 19F MR images could be acquired, because photo‐CIDNP enabled repetitive hyperpolarization without adding new substrates.

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“…For the purposes of photo-CIDNP spectroscopy, mixtures of amino acids have been used to model a random-coil protein (Vogel, 1983). Such experiments must be performed above pH 4 to ensure that the rapid degenerate electron-transfer reaction between tryptophan and its radical cation (an intermediate in the chemical reactions that generate CIDNP) does not destroy the tryptophan polarization (Kaptein, 1982;Stob & Kaptein, 1989). This is not a problem in lysozyme itself because of the much smaller rate of electron transfer resulting from the slower translational diffusion of the protein.…”

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A photochemically induced dynamic nuclear polarization study of denatured state of lysozyme

Broadhurst

Dobson²,

Hore³

et al. 1991

Biochemistry

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Photochemically induced dynamic nuclear polarization (photo-CIDNP) techniques have been used to examine denatured states of lysozyme produced under a variety of conditions. 1H CIDNP difference spectra of lysozyme denatured thermally, by the addition of 10 M urea, or by the complete reduction of its four disulfide bonds were found to differ substantially not only from the spectrum of the native protein but also from that expected for a completely unstructured polypeptide chain. Specifically, denatured lysozyme showed a much reduced enhancement of tryptophan relative to tyrosine than did a mixture of blocked amino acids with the same composition as the intact protein. By contrast, the CIDNP spectrum of lysozyme denatured in dimethyl sulfoxide solution was found to be similar to that expected for a random coil. It is proposed that nonrandom hydrophobic interactions are present within the denatured states of lysozyme in aqueous solution and that these reduce the reactivity of tryptophan residues relative to tyrosine residues. Characterization of such interactions is likely to be of considerable significance for an understanding of the process of protein folding.

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Photo‐cidnp of the Amino Acids

Cited by 53 publications

References 31 publications

Involvement of Laser Photo‐CIDNP(Chemically Induced Dynamic Nuclear Polarization)‐Reactive Amino Acid Side Chains in Ligand Binding by Galactoside‐Specific Lectins in Solution

Involvement of Laser Photo‐CIDNP(Chemically Induced Dynamic Nuclear Polarization)‐Reactive Amino Acid Side Chains in Ligand Binding by Galactoside‐Specific Lectins in Solution

Low‐cost LED‐based Photo‐CIDNP Enables Biocompatible Hyperpolarization of ¹⁹F for NMR and MRI at 7 T and 4.7 T

A photochemically induced dynamic nuclear polarization study of denatured state of lysozyme

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Photo‐cidnp of the Amino Acids

Cited by 53 publications

References 31 publications

Involvement of Laser Photo‐CIDNP(Chemically Induced Dynamic Nuclear Polarization)‐Reactive Amino Acid Side Chains in Ligand Binding by Galactoside‐Specific Lectins in Solution

Involvement of Laser Photo‐CIDNP(Chemically Induced Dynamic Nuclear Polarization)‐Reactive Amino Acid Side Chains in Ligand Binding by Galactoside‐Specific Lectins in Solution

Low‐cost LED‐based Photo‐CIDNP Enables Biocompatible Hyperpolarization of 19F for NMR and MRI at 7 T and 4.7 T

A photochemically induced dynamic nuclear polarization study of denatured state of lysozyme

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Low‐cost LED‐based Photo‐CIDNP Enables Biocompatible Hyperpolarization of ¹⁹F for NMR and MRI at 7 T and 4.7 T