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Two-dimensional measurement of proton T1rho relaxation in unlabeled proteins: mobility changes in alpha-bungarotoxin upon binding of an acetylcholine receptor peptide.

ABSTRACT: A method for the measurement of proton T(1)(rho) relaxation times in unlabeled proteins is described using a variable spin-lock pulse after the initial nonselective 90 degrees excitation in a HOHAHA pulse sequence. The experiment is applied to alpha-bungarotoxin (alpha-BTX) and its complex with a 25-residue peptide derived from the acetylcholine receptor (AChR) alpha-subunit. A good correlation between high T(1)(rho) values and increased local motion is revealed. In the free form, toxin residues associated with receptor binding according to the NMR structure of the alpha-BTX complex with an AChR peptide and the model for alpha-BTX with the AChR [Samson, A. O., et al. (2002) Neuron 35, 319-332] display high mobility. When the AChR peptide binds, a decrease in the relaxation times and the level of motion of residues involved in binding of the receptor alpha-subunit is exhibited, while residues implicated in binding gamma- and delta-subunits retain their mobility. In addition, the quantitative T(1)(rho) measurements enable us to corroborate the mapping of boundaries of the AChR determinant strongly interacting with the toxin [Samson, A. O., et al. (2001) Biochemistry 40, 5464-5473] and can similarly be applied to other protein complexes in which peptides represent one of the two interacting proteins. The presented method is advantageous because of its simplicity, generality, and time efficiency and paves the way for future investigation of proton relaxation rates in small unlabeled proteins.

SUBMITTER: Samson AO

PROVIDER: S-EPMC2597414 | biostudies-literature | 2005 Aug

REPOSITORIES: biostudies-literature

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Two-dimensional measurement of proton T1rho relaxation in unlabeled proteins: mobility changes in alpha-bungarotoxin upon binding of an acetylcholine receptor peptide.

Samson Abraham O AO Chill Jordan H JH Anglister Jacob J

Biochemistry 20050801 32

A method for the measurement of proton T(1)(rho) relaxation times in unlabeled proteins is described using a variable spin-lock pulse after the initial nonselective 90 degrees excitation in a HOHAHA pulse sequence. The experiment is applied to alpha-bungarotoxin (alpha-BTX) and its complex with a 25-residue peptide derived from the acetylcholine receptor (AChR) alpha-subunit. A good correlation between high T(1)(rho) values and increased local motion is revealed. In the free form, toxin residues ...[more]

PMID: 16086595

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Project description:In pre-clinical models of brain gliomas, Relaxation Along a Fictitious Field in second rotating frame (TRAFF2), continues wave T1rho (T1ρcw), adiabatic T1rho (T1ρadiab), and adiabatic T2rho (T2ρadiab) relaxation time mappings have demonstrated potential to non-invasively characterize brain gliomas. Our aim was to evaluate the feasibility and potential of 4 different spin lock methods at 3T to characterize primary brain glioma. 22 patients (26-72 years) with suspected primary glioma. T1ρcw was performed using pulse peak amplitude of 500Hz and pulse train durations of 40 and 80 ms while the corresponding values for T1ρadiab, T2ρadiab, TRAFF2 were 500/500/500Hz and 48 and 96, 64 and 112, 45 and 90 ms, respectively. The parametric maps were calculated using a monoexponential model. Molecular profiles were evaluated from tissue specimens obtained during the resection. The lesion regions-of-interest were segmented from high intensity FLAIR using automatic segmentation with manual refinement. Statistical descriptors from the voxel intensity values inside each lesion and radiomic features (Pyrad MRC package) were calculated. From extracted radiomics, mRMRe R package version 2.1.0 was used to select 3 features in each modality for statistical comparisons. Of the 22 patients, 10 were found to have IDH-mutant gliomas and of those 5 patients had 1p/19q codeletion group comparisons. Following correction for effects of age and gender, at least one statistical descriptor was able to differentiate between IDH and 1p/19q codeletion status for all the parametric maps. In the radiomic analysis, corner-edge detector features with Harris-Stephens filtered signal showed significant group differences in IDH and 1p/19q codeletion groups. Spin lock imaging at 3T of human glioma was feasible and various qualitative parameters derived from the parametric maps were found to have potential to differentiate IDH and 1p19q codeletion status. Future larger prospective clinical trials are warranted to evaluate these methods further.

Dataset Information

Two-dimensional measurement of proton T1rho relaxation in unlabeled proteins: mobility changes in alpha-bungarotoxin upon binding of an acetylcholine receptor peptide.

Publications

Two-dimensional measurement of proton T1rho relaxation in unlabeled proteins: mobility changes in alpha-bungarotoxin upon binding of an acetylcholine receptor peptide.

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