NMR Relaxation Parameters Research Articles

ИССЛЕДОВАНИЕ АДСОРБЦИИ МОЛЕКУЛ ВОДЫ НА КАЛЬЦИЙСОДЕРЖАЩИХ МАТЕРИАЛАХ МЕТОДАМИ ФИЗИКО-ХИМИЧЕСКОГО АНАЛИЗА

Physico-chemical methods of analysis were used to study calcium-containing materials - water systems. Samples of calcium-containing materials - micromarble of RIF, Koelga, OMUA grades, as well as silicate glass - were studied. The structural characteristics of the studied materials were determined on the basis of the analysis of experimental isotherms of water vapour adsorption obtained by the isopiestic method at 298 K. It was found that the adsorption isotherms of water vapour adsorption on the studied materials have a shape intermediate between II and III type according to Brunauer's classification, which is characteristic of adsorption on non-porous and macroporous adsorbents. The analysis of adsorption isotherms showed that they are practically parallel to each other in a wide range (p/ps=0.05-0.85), in the region of high relative pressures of adsorbent a rise of adsorption isotherm for silicate glass is observed. The identical type of isotherms for micromarbles is explained by the similarity of chemical structure of samples, small differences in the values of adsorption indicate a small difference in the values of specific surface area and particle size of materials. It is shown that adsorption of water vapour on the surface of the samples occurs with the formation of complexes - clusters consisting of calcium carbonate molecules surrounded by adsorbate molecules due to the formation of hydrogen bonds between the surface oxygen and sorbed water molecules. In the framework of theoretical models, sorption and structural parameters of adsorbent and adsorbate were determined from linearised forms of Langmuir and BET equations linking sorption values and relative vapour pressures of adsorbate. NMR-relaxation parameters of sorbed water protons were measured on a spectrometer with a working frequency of 20 MHz. According to NMR data, the relationship between spin-spin and spin-lattice relaxation times and the state of adsorbed water molecules was established. The character of dependences of spin-spin (T2) and spin-lattice (T1) relaxation times of adsorbed water on the value of water sorption (W) indicates the influence of specific surface area and size of adsorbent particles on the mobility of adsorbed water molecules and confirms the mechanism of cluster formation during adsorption of water vapour on calcium-containing materials.

MD Simulations to Calculate NMR Relaxation Parameters of Vanadium(IV) Complexes: A Promising Diagnostic Tool for Cancer and Alzheimer's Disease.

Early phase diagnosis of human diseases has still been a challenge in the medicinal field, and one of the efficient non-invasive techniques that is vastly used for this purpose is magnetic resonance imaging (MRI). MRI is able to detect a wide range of diseases and conditions, including nervous system disorders and cancer, and uses the principles of NMR relaxation to generate detailed internal images of the body. For such investigation, different metal complexes have been studied as potential MRI contrast agents. With this in mind, this work aims to investigate two systems containing the vanadium complexes [VO(metf)2]·H2O (VC1) and [VO(bpy)2Cl]+ (VC2), being metformin and bipyridine ligands of the respective complexes, with the biological targets AMPK and ULK1. These biomolecules are involved in the progression of Alzheimer's disease and triple-negative breast cancer, respectively, and may act as promising spectroscopic probes for detection of these diseases. To initially evaluate the behavior of the studied ligands within the aforementioned protein active sites and aqueous environment, four classical molecular dynamics (MD) simulations including VC1 + H2O (1), VC2 + H2O (2), VC1 + AMPK + H2O (3), and VC2 + ULK1 + H2O (4) were performed. From this, it was obtained that for both systems containing VCs and water only, the theoretical calculations implied a higher efficiency when compared with DOTAREM, a famous commercially available contrast agent for MRI. This result is maintained when evaluating the system containing VC1 + AMPK + H2O. Nevertheless, for the system VC2 + ULK1 + H2O, there was observed a decrease in the vanadium complex efficiency due to the presence of a relevant steric hindrance. Despite that, due to the nature of the interaction between VC2 and ULK1, and the nature of its ligands, the study gives an insight that some modifications on VC2 structure might improve its efficiency as an MRI probe.

NMR Relaxation Experiments Probe Monomer-Fibril Interaction and Identify Critical Interacting Residues Responsible for Distinct Tau Fibril Morphologies.

Tau aggregation is governed by secondary processes, a major pathological pathway for tau protein fibril propagation, yet its molecular mechanism remains unknown. This work uses saturation transfer and lifetime line-broadening experiments to identify the critical residues involved in these secondary processes. Distinct residue-specific NMR relaxation parameters were obtained for the truncated three repeat tau construct (K19) in equilibrium with structurally different, self-aggregated (saK19) or heparin-induced (hK19) fibrils. The interacting residues are restricted to R3 repeat for hK19 and to R3, R4, and R' repeats for saK19 fibrils. Furthermore, the relaxation profiles of tau monomers in equilibrium with the structurally comparable, in vitro pathological fibrils (tauAD and tauCTE) were similar but distinct from hK19 or saK19 fibrils. Thus, residue-specific relaxation identifies the important residues involved in the binding of monomers to the fibrils. The relaxation profile of the monomers in equilibrium with the NMR invisible fibril seeds potentially distinguishes the distinct structures of tau fibrils.

Unraveling Water-Mediated 31P Relaxation in Bone Mineral.

Bone is a dynamic tissue composed of organic proteins (mainly type I collagen), inorganic components (hydroxyapatite), lipids, and water that undergoes a continuous rebuilding process over the lifespan of human beings. Bone mineral is mainly composed of a crystalline apatitic core surrounded by an amorphous surface layer. The supramolecular arrangement of different constituents gives rise to its unique mechanical properties, which become altered in various bone-related disease conditions. Many of the interactions among the different components are poorly understood. Recently, solid-state nuclear magnetic resonance (ssNMR) has become a popular spectroscopic tool for studying bone. In this article, we present a study probing the interaction of water molecules with amorphous and crystalline parts of the bone mineral through 31P ssNMR relaxation parameters (T1 and T2) and dynamics (correlation time). The method was developed to selectively measure the 31P NMR relaxation parameters and dynamics of the crystalline apatitic core and the amorphous surface layer of the bone mineral. The measured 31P correlation times (in the range of 10–6–10–7 s) indicated the different dynamic behaviors of both the mineral components. Additionally, we observed that dehydration affected the apatitic core region more significantly, while H–D exchange showed changes in the amorphous surface layer to a greater extent. Overall, the present work provides a significant understanding of the relaxation and dynamics of bone mineral components inside the bone matrix.

How Much Entropy Is Contained in NMR Relaxation Parameters?

Solution-state NMR relaxation experiments are the cornerstone to study internal protein dynamics at an atomic resolution on time scales that are faster than the overall rotational tumbling time τR. Since the motions described by NMR relaxation parameters are connected to thermodynamic quantities like conformational entropies, the question arises how much of the total entropy is contained within this tumbling time. Using all-atom molecular dynamics simulations of the T4 lysozyme, we found that entropy buildup is rather fast for the backbone, such that the majority of the entropy is indeed contained in the short-time dynamics. In contrast, the contribution of the slow dynamics of side chains on time scales beyond τR on the side-chain conformational entropy is significant and should be taken into account for the extraction of accurate thermodynamic properties.

Stochastic Modelling of 13C NMR Spin Relaxation Experiments in Oligosaccharides.

A framework for the stochastic description of relaxation processes in flexible macromolecules including dissipative effects has been recently introduced, starting from an atomistic view, describing the joint relaxation of internal coordinates and global degrees of freedom, and depending on parameters recoverable from classic force fields (energetics) and medium modelling at the continuum level (friction tensors). The new approach provides a rational context for the interpretation of magnetic resonance relaxation experiments. In its simplest formulation, the semi-flexible Brownian (SFB) model has been until now shown to reproduce correctly correlation functions and spectral densities related to orientational properties obtained by direct molecular dynamics simulations of peptides. Here, for the first time, we applied directly the SFB approach to the practical evaluation of high-quality 13C nuclear magnetic resonance relaxation parameters, and , and the heteronuclear NOE of several oligosaccharides, which were previously interpreted on the basis of refined ad hoc modelling. The calculated NMR relaxation parameters were in agreement with the experimental data, showing that this general approach can be applied to diverse classes of molecular systems, with the minimal usage of adjustable parameters.

Solid-state NMR of unlabeled plant cell walls: high-resolution structural analysis without isotopic enrichment

BackgroundMultidimensional solid-state nuclear magnetic resonance (ssNMR) spectroscopy has emerged as an indispensable technique for resolving polymer structure and intermolecular packing in primary and secondary plant cell walls. Isotope (13C) enrichment provides feasible sensitivity for measuring 2D/3D correlation spectra, but this time-consuming procedure and its associated expenses have restricted the application of ssNMR in lignocellulose analysis.ResultsHere, we present a method that relies on the sensitivity-enhancing technique Dynamic Nuclear Polarization (DNP) to eliminate the need for 13C-labeling. With a 26-fold sensitivity enhancement, a series of 2D 13C–13C correlation spectra were successfully collected using the unlabeled stems of wild-type Oryza sativa (rice). The atomic resolution allows us to observe a large number of intramolecular cross peaks for fully revealing the polymorphic structure of cellulose and xylan. NMR relaxation and dipolar order parameters further suggest a sophisticated change of molecular motions in a ctl1 ctl2 double mutant: both cellulose and xylan have become more dynamic on the nanosecond and microsecond timescale, but the motional amplitudes are uniformly small for both polysaccharides.ConclusionsBy skipping isotopic labeling, the DNP strategy demonstrated here is universally extendable to all lignocellulose materials. This time-efficient method has landed the technical foundation for understanding polysaccharide structure and cell wall assembly in a large variety of plant tissues and species.

NMR Studies of Bicontinuous Liquid Crystalline Phases of Cubic Symmetry: Interpretation of Frequency-Dependent Relaxation Rates.

Extensive deuterium NMR relaxation data are presented for two specifically deuterium labeled surfactants forming bicontinuous cubic phases with water. 2H spin-lattice (R1) and spin-spin (R2) relaxation rates were measured over an extended frequency range from 2 to 60 MHz. The data are interpreted with an existing theoretical framework for spin relaxation in bicontinuous cubic phases, which takes its starting point in the description of bicontinuous phases using periodic minimal surfaces. We show that the theory succeeds in accounting for the data and that the defining parameters of the theory, correlation times and order parameters, are in agreement with related data in other surfactant phase situations. Specifically, we obtain the surfactant self-diffusion coefficient over the minimal surface in one unit cell and show that it is in agreement with the corresponding macroscopic NMR diffusion data. By measuring two additional NMR relaxation parameters for each carbon on the surfactant hydrocarbon tail, we demonstrate how order parameter and correlation time profiles can be obtained. Finally, we analyze published molecular dynamics trajectories for a bicontinuous cubic phase. The analysis provides further support for the theoretical framework used to interpret relaxation data.

Choice of Force Field for Proteins Containing Structured and Intrinsically Disordered Regions

Biomolecular force fields optimized for globular proteins fail to properly reproduce properties of intrinsically disordered proteins. In particular, parameters of the water model need to be modified to improve applicability of the force fields to both ordered and disordered proteins. Here, we compared performance of force fields recommended for intrinsically disordered proteins in molecular dynamics simulations of three proteins differing in the content of ordered and disordered regions (two proteins consisting of a well-structured domain and of a disordered region with and without a transient helical motif and one disordered protein containing a region of increased helical propensity). The obtained molecular dynamics trajectories were used to predict measurable parameters, including radii of gyration of the proteins and chemical shifts, residual dipolar couplings, paramagnetic relaxation enhancement, and NMR relaxation data of their individual residues. The predicted quantities were compared with experimental data obtained within this study or published previously. The results showed that the NMR relaxation parameters, rarely used for benchmarking, are particularly sensitive to the choice of force-field parameters, especially those defining the water model. Interestingly, the TIP3P water model, leading to an artificial structural collapse, also resulted in unrealistic relaxation properties. The TIP4P-D water model, combined with three biomolecular force-field parameters for the protein part, significantly improved reliability of the simulations. Additional analysis revealed only one particular force field capable of retaining the transient helical motif observed in NMR experiments. The benchmarking protocol used in our study, being more sensitive to imperfections than the commonly used tests, is well suited to evaluate the performance of newly developed force fields.

Correlation of Physicochemical Properties of Bach Ho Oils with Proton NMR Relaxation Parameters and Their Temperature Dependence

The physicochemical properties of crude oils (density, viscosity, asphaltene concentrations) from the Bach Ho oilfield (Vietnam) have been correlated with 1H NMR relaxation parameters (spin–lattice and spin–spin relaxation times T1i and T2i, respectively), and their temperature dependence has been studied. The results are discussed in terms of the concept of the formation of structural units (SU) in oils. The standard “alkane line”—the conventional correlation ηТ1,2 = const/Т for viscous oils—has been refined. The temperature dependences of T1,2i have been obtained, which manifest ordering processes in the test oils.

Возможности протонного магнитного резонанса в определении степени кристалличности целлюлозы

A layered model of the structural organization of macrofibrils of native cellulose, consisting of microfibrils, which include elementary fibrils, has been developed. A feature of the proposed model is the presence of slit-like pores between the crystalline elements of cellulose. It was found that, on average, each water molecule interacts with one glucose residue of the surface chains of cellulose with the formation of hydrogen bonds in the framework of monolayer adsorption. This allows to establish a correlation between the cellulose crystallinity and the capacity of the adsorption water monolayer on its active surface. Based on the condition of rapid molecular exchange between the adsorption water layers in the framework of the Bloembergen-Purcell-Pound theory, an approach is proposed for determination the capacity of water monolayer. The obtained values are consistent with the results of solving the Brunauer-Emmett-Teller equation for the adsorption isotherm of water on the active surface of cellulose. The Fourier transform of the free induction decay signal of cellulose allows to estimate its crystallinity at various moisture contents. Methods have been developed for assessing the crystallinity of different types of dry cellulose based on NMR relaxation parameters — spin-lattice relaxation time and spin-spin relaxation time. Using the method of deuteration of cellulose, the relaxation times of its crystalline regions were determined. The results of preliminary studies showed that the crystallinity of cotton cellulose is higher in comparison with the same parameter of woody types of cellulose. A comparison of the literature and the data we obtained using 1H-NMR relaxation confirmed the possibility of utilizing the developed methods to solve the tasks of scientific research and conducting quality control of cellulosic materials at specialized enterprises.

Crystal structure of the N domain of Lon protease from Mycobacterium avium complex.

Lon protease is evolutionarily conserved in prokaryotes and eukaryotic organelles. The primary function of Lon is to selectively degrade abnormal and certain regulatory proteins to maintain the homeostasis in vivo. Lon mainly consists of three functional domains and the N-terminal domain is required for the substrate selection and recognition. However, the precise contribution of the N-terminal domain remains elusive. Here, we determined the crystal structure of the N-terminal 192-residue construct of Lon protease from Mycobacterium avium complex at 2.4 å resolution，and measured NMR-relaxation parameters of backbones. This structure consists of two subdomains, the β-strand rich N-terminal subdomain and the five-helix bundle of C-terminal subdomain, connected by a flexible linker，and is similar to the overall structure of the N domain of Escherichia coli Lon even though their sequence identity is only 26%. The obtained NMR-relaxation parameters reveal two stabilized loops involved in the structural packing of the compact N domain and a turn structure formation. The performed homology comparison suggests that structural and sequence variations in the N domain may be closely related to the substrate selectivity of Lon variants. Our results provide the structure and dynamics characterization of a new Lon N domain, and will help to define the precise contribution of the Lon N-terminal domain to the substrate recognition.

NMR relaxation and relaxivity parameters of MRI probes revealed by optimal wavelet signal compression of molecular dynamics simulations

The MRI contrast agents (CAs) have been routinely used for detecting tumors at early stages. Currently, the most used CAs in MRI are gadolinium (Gd3+) complexes. However, these CAs can be toxic to the body. Thus, this work proposes Ni2+ complexes ([Ni(ACAC)2(H2O)2], [Ni(TEA)]2+) as promising CAs. For the theoretical prediction, molecular dynamics simulations were carried out and the conformations were selected by the optimal wavelet signal compression algorithm method. The T1 and T2 values were obtained directly by means of the spectral density. Our findings showed that the Ni2+ complexes can be promising CAs in MRI.

The Singular NMR Fingerprint of a Polyproline II Helical Bundle.

Polyproline II (PPII) helices play vital roles in biochemical recognition events and structures like collagen and form part of the conformational landscapes of intrinsically disordered proteins (IDPs). Nevertheless, this structure is generally hard to detect and quantify. Here, we report the first thorough NMR characterization of a PPII helical bundle protein, the Hypogastrura harveyi "snow flea" antifreeze protein (sfAFP). J-couplings and nuclear Overhauser enhancement spectroscopy confirm a natively folded structure consisting of six PPII helices. NMR spectral analyses reveal quite distinct Hα2 versus Hα3 chemical shifts for 28 Gly residues as well as 13Cα, 15N, and 1HN conformational chemical shifts (Δδ) unique to PPII helical bundles. The 15N Δδ and 1HN Δδ values and small negative 1HN temperature coefficients evince hydrogen-bond formation. 1H-15N relaxation measurements reveal that the backbone structure is generally highly rigid on ps-ns time scales. NMR relaxation parameters and biophysical characterization reveal that sfAFP is chiefly a dimer. For it, a structural model featuring the packing of long, flat hydrophobic faces at the dimer interface is advanced. The conformational stability, measured by amide H/D exchange to be 6.24 ± 0.2 kcal·mol-1, is elevated. These are extraordinary findings considering the great entropic cost of fixing Gly residues and, together with the remarkable upfield chemical shifts of 28 Gly 1Hα, evidence significant stabilizing contributions from CαHα ||| O═C hydrogen bonds. These stabilizing interactions are corroborated by density functional theory calculations and natural bonding orbital analysis. The singular conformational chemical shifts, J-couplings, high hNOE ratios, small negative temperature coefficients, and slowed H/D exchange constitute a unique set of fingerprints to identify PPII helical bundles, which may be formed by hundreds of Gly-rich motifs detected in sequence databases. These results should aid the quantification of PPII helices in IDPs, the development of improved antifreeze proteins, and the incorporation of PPII helices into novel designed proteins.

Differential Conformational Dynamics Encoded by the Linker between Quasi RNA Recognition Motifs of Heterogeneous Nuclear Ribonucleoprotein H.

Members of the heterogeneous nuclear ribonucleoprotein (hnRNP) F/H family are multipurpose RNA binding proteins that participate in most stages of RNA metabolism. Despite having similar RNA sequence preferences, hnRNP F/H proteins function in overlapping and, in some cases, distinct cellular processes. The domain organization of hnRNP F/H proteins is modular, consisting of N-terminal tandem quasi-RNA recognition motifs (F/HqRRM1,2) and a third C-terminal qRRM3 embedded between glycine-rich repeats. The tandem qRRMs are connected through a 10-residue linker, with several amino acids strictly conserved between hnRNP H and F. A significant difference occurs at position 105 of the linker, where hnRNP H contains a proline and hnRNP F an alanine. To investigate the influence of P105 on the conformational properties of hnRNP H, we probed the structural dynamics of its HqRRM1,2 domain with X-ray crystallography, NMR spectroscopy, and small-angle X-ray scattering. The collective results best describe that HqRRM1,2 exists in a conformational equilibrium between compact and extended structures. The compact structure displays an electropositive surface formed at the qRRM1–qRRM2 interface. Comparison of NMR relaxation parameters, including Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion, between HqRRM1,2 and FqRRM1,2 indicates that FqRRM1,2 primarily adopts a more extended and flexible conformation. Introducing the P105A mutation into HqRRM1,2 alters its conformational dynamics to favor an extended structure. Thus, our work demonstrates that the linker compositions confer different structural properties between hnRNP F/H family members that might contribute to their functional diversity.

Stability, lability, spectral parameters and structure of complexes and stereoselective effects in the nickel(II) – l/d/dl-histidine – l/d/dl-methionine systems

Abstract The equilibrium constants, spectral characteristics of complexes, formation thermodynamic parameters and constants of the chemical exchange reactions in the nickel(II) – l / d / dl -histidine (HisH) – l / d / dl -methionine (MetH) systems (25 °C, 1.0 mol dm−3 KNO3) over wide ranges of pH and ligands to metal ratio were calculated from the pH-potentiometry, multi-wavelength electronic spectroscopy, calorimetry and NMR relaxation data. Based on the DFT computation the structures of some complexes have been proposed. Significant enantioselective effects are exhibited in the formation constants and in some electronic spectra and NMR relaxation parameters of a number of complexes with the meso-forms domination. For the Ni(His)2 complex the process of alkaline catalysis of proton exchange with the short-time N-H proton removal from the coordinated imidazole fragment was characterized. It was shown that in the ligand exchange reaction between Ni(His)2 and His− the Ni(His)3− complex participates as an intermediate. It was found that the Met− thiomethyl group is not bounded in the Ni(Met)+ and Ni(Met)2 complexes but coordinated in the Ni(His)(Met) form. Main factors determining stereoselectivity in the complex formation processes and ligand exchange reactions in the systems studied were identified as trans effect, solvation effect and a new type of interligand thiomethyl group–imidazole ring weak interaction.

Differential Dynamics at Glycosidic Linkages of an Oligosaccharide as Revealed by 13C NMR Spin Relaxation and Stochastic Modeling.

Among biomolecules, carbohydrates are unique in that not only can linkages be formed through different positions, but the structures may also be branched. The trisaccharide β-d-Glcp-(1→3)[β-d-Glcp-(1→2)]-α-d-Manp-OMe represents a model of a branched vicinally disubstituted structure. A 13C site-specific isotopologue, with labeling in each of the two terminal glucosyl residues, enabled the acquisition of high-quality 13C NMR relaxation parameters, T1 and T2, and heteronuclear NOE, with standard deviations of ≤0.5%. For interpretation of the experimental NMR data, a diffusive chain model was used, in which the dynamics of the glycosidic linkages is coupled to the global reorientation motion of the trisaccharide. Brownian dynamics simulations relying on the potential of mean force at the glycosidic linkages were employed to evaluate spectral densities of the spin probes. Calculated NMR relaxation parameters showed a very good agreement with experimental data, deviating <3%. The resulting dynamics are described by correlation times of 196 and 174 ps for the β-(1→2)- and β-(1→3)-linked glucosyl residues, respectively, i.e., different and linkage dependent. Notably, the devised computational protocol was performed without any fitting of parameters.

Structure and Conformational Dynamics of the Splicing Factor hnRNP H

Members of the heterogeneous nuclear ribonucleoprotein (hnRNP) H/F family are multi purpose RNA binding proteins that participate in most stages of RNA metabolism. Despite having similar RNA sequence preferences, hnRNP H/F proteins function in overlapping but distinct cellular processes. The domain organization of hnRNP H/F proteins is modular consisting of N-terminal tandem quasi-RNA Recognition Motifs (H/FqRRM12) and a third C-terminal qRRM3 embedded within glycine-rich repeats. The tandem qRRMs are connected through a 10-residue linker with most of the amino acids strictly conserved between hnRNP H and F. A significant difference occurs at position 99 of the linker where hnRNP H contains a proline and hnRNP F an alanine. To investigate the influence of P99 on the conformational properties of hnRNP H, we probed the structural dynamics of its HqRRM12 domain with x-ray crystallography, NMR spectroscopy, and Small Angle X-ray Scattering (SAXS). We observed in the HqRRM12 contains multiple structures in solution by SAXS. These exchangeable conformations that located on the linker region and RNA recognition sites reach certain equilibrium in different temperature by NMR relaxation dispersion. The collective results best describe that HqRRM12 exists in a conformational equilibrium between compact and extended structures. The compact structure displays an electropositive surface formed at the qRRM1-qRRM2 interface; the surface is abrogated within the extended structure. Comparison of NMR relaxation parameters between HqRRM12 and FqRRM12 indicate that FqRRM12 primarily adopts an extended conformation. Introducing the P99A mutation into HqRRM12 alters its conformational dynamics to favor the more extended structure. Thus, our work demonstrates that the linker compositions confer different structural properties between hnRNP H/F family members that might contribute to their functional diversity.

Viscosity Correlations with Nuclear (Proton) Magnetic Resonance Relaxation in Oil Disperse Systems

Using nuclear (proton) magnetic resonance relaxometry (NMRR) was studied oil disperse systems. Dependences of NMR–relaxation parameters—spin–lattice T1i, spin–spin T2i relaxation times, proton populations P1i and P2i, and petrophysical correlations were received for light and heavy oils. Experimental results are interpreted on the base of structure-dynamical ordering of oil molecules with structure unit formation.

NMR relaxation parameters of methyl groups as a tool to map the interfaces of helix-helix interactions in membrane proteins.

In the case of soluble proteins, chemical shift mapping is used to identify the intermolecular interfaces when the NOE-based calculations of spatial structure of the molecular assembly are impossible or impracticable. However, the reliability of the membrane protein interface mapping based on chemical shifts or other relevant parameters was never assessed. In the present work, we investigate the predictive power of various NMR parameters that can be used for mapping of helix-helix interfaces in dimeric TM domains. These parameters are studied on a dataset containing three structures of helical dimers obtained for two different proteins in various membrane mimetics. We conclude that the amide chemical shifts have very little predictive value, while the methyl chemical shifts could be used to predict interfaces, though with great care. We suggest an approach based on conversion of the carbon NMR relaxation parameters of methyl groups into parameters of motion, and one of such values, the characteristic time of methyl rotation, appears to be a reliable sensor of interhelix contacts in transmembrane domains. The carbon NMR relaxation parameters of methyl groups can be measured accurately and with high sensitivity and resolution, making the proposed parameter a useful tool for investigation of protein-protein interfaces even in large membrane proteins. An approach to build the models of transmembrane dimers based on perturbations of methyl parameters and TMDOCK software is suggested.