Nuclear Magnetic Resonance Data Research Articles

A Branch-and-Bound Algorithm for the Molecular Ordered Covering Problem.

The Discretizable Molecular Distance Geometry Problem (DMDGP) plays a key role in the construction of three-dimensional molecular structures from interatomic distances acquired through nuclear magnetic resonance (NMR) spectroscopy, with the primary objective of validating a sequence of distance constraints related to NMR data. This article addresses the escalating complexity of the DMDGP encountered with larger and more flexible molecules by introducing a novel strategy via the Molecular Ordered Covering Problem, which optimizes the ordering of distance constraints to improve computational efficiency in DMDGP resolution. This approach utilizes a specialized Branch-and-Bound (BB) algorithm, tested on both synthetic and actual protein structures from the protein data bank. Our analysis demonstrates the efficacy of the previously proposed greedy heuristic in managing complex molecular scenarios, highlighting the BB algorithm's utility as a validation mechanism. This research contributes to ongoing efforts in molecular structure analysis, with possible implications for areas such as protein folding, drug design, and molecular modeling.

Influence of an Intrinsically Disordered Region on Protein Domains Revealed by NMR-Based Electrostatic Potential Measurements.

Many human proteins possess intrinsically disordered regions containing consecutive aspartate or glutamate residues ("D/E repeats"). Approximately half of them are DNA/RNA-binding proteins. In this study, using nuclear magnetic resonance (NMR) spectroscopy, we investigated the electrostatic properties of D/E repeats and their influence on folded domains within the same protein. Local electrostatic potentials were directly measured for the HMGB1 protein, its isolated D/E repeats, and DNA-binding domains by NMR. The data provide quantitative information about the electrostatic interactions between distinct segments of HMGB1. Due to the interactions between the D/E repeats and the DNA-binding domains, local electrostatic potentials of the DNA-binding domains within the full-length HMGB1 protein were largely negative despite the presence of many positively charged residues. Our NMR data on counterions and electrostatic potentials show that the D/E repeats and DNA have similar electrostatic properties and compete for the DNA-binding domains. The competition promotes dissociation of the protein-DNA complex and influences the molecular behavior of the HMGB1 protein. These effects may be general among the DNA/RNA-binding proteins with D/E repeats.

Characterization of the evolution of thermal maturity and pore structure of continental organic-rich shales

To clarify the evolution of thermal maturity and pore structure in continental organic-rich shales, calcareous shales of the Liaohe Basin (China) were pyrolyzed, and examined using Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nitrogen sorption isotherms, and nuclear magnetic resonance (NMR) spectroscopy. The increase in Raman G‒D band separation and decrease in Raman ID/IG ratio with increasing thermal maturity indicate that these parameters provide superior thermal maturity indicators. This is also confirmed by the good linear correlation of G‒D band shifts and ID/IG with vitrinite reflectance (VR) and maximum temperature (Tmax), respectively. The relative detection accuracy (DA), sampling requirements (SR), sample preparation (SP), detection time (DT), and equipment requirement (ER) of VR, G‒D band shifts, ID/IG, Tmax, FTIR, and XPS indicate that Raman analysis is a simple, quick, and robust method to evaluate thermal maturity. The moderate SR, complex SP, and long DT suggest that VR and Tmax are less widely applicable for characterizing thermal maturity. The FTIR and XPS techniques provide semi-quantitative maturity indicators with poor DA and high ER. Pores observed within organic matter and minerals under SEM indicate that an increase in thermal maturity not only affects the development of organic pores but is also beneficial for the formation of mineral dissolution pores, such as those formed during the transformation of Na0.95Ca0.16Al1.16Si2.84O8 to Na0.84Ca0.02Al1.02Si2.98O8, a process confirmed by XRD. The BET and NMR data also indicate that the development of pore structure is closely related to the evolution of thermal maturity in calcareous shale. During the initial stage, primary pores are filled by bitumen generated from kerogen; this leads to a decrease in transition pores, mesopores, and shale porosity, and reduced pore connectivity. Then, secondary nanoscale pores, transition pores, and mesopores increase with increasing thermal maturity. The peak in secondary porosity is consistent with the liquid hydrocarbon production rate peak, a process that increases shale porosity and leads to improved pore connectivity. The dissolution of minerals induced by organic acids may also contribute to this secondary porosity. With a further increase in thermal maturity, secondary porosity at the microscale is further developed, while transition pores and mesopores collapse, resulting in reduced pore connectivity. The poor pore connectivity that occurs at both low and high VR values may be more conducive to the preservation of shale oil and gas. This study is significant for research into the evolution of thermal maturity and pore structure in continental organic-rich shales.

Revealing Interaction of Fluorinated Propylamine Hydrochloride with Precursor and Defect States of Perovskite Films Toward Efficient Flexible Solar Cells

AbstractThe trap state at the surfaces and grain boundaries of perovskite is one of the major obstacles to the further commercialization of flexible perovskite solar cells (FPSCs). Herein, two innovative multifunctional fluorinated propylamine salt 2,2,3,3,3‐pentafluoropropylamine hydrochloride (PFPACl) and 3,3,3‐triflupropylamine hydrochloride (TFPACl) are in situ introduced onto the photo absorbing layer to improve the performance of the FPSCs. The nuclear magnetic resonance (NMR) spectroscopy indicates strong interactions of both PFPACl and TFPACl with the perovskite precursor components. For the first time, the structures of the supramolecular complexes formed by two additives with FAI are deduced from NOESY NMR data, thus pointing to the importance of the preorganization of the perovskite components in solution before film casting. The experiments and density functional theory（DFT) calculations reveal that PFPACl is likely dissociated more into the form of R‐NH3+‐Cl− due to the higher electronegativity of the fluoroalkyl tail. Therefore, PFPA+ binds more strongly to VFA defects than TFPA+, and anion Cl− has strong enough interaction with VFAI and uncoordinated Pb2+, leading to homogeneous coverage of PFPACl on the entire surface of the perovskite films and better energy alignment with the hole transport layer. Consequently, PFPACl‐treated FPSCs achieved a relatively high PCE of 23.59% with excellent mechanical robustness and operational stability.

Predicting the compressive strength of tight sandstone based on the low field NMR and pseudo-triaxial compression measurements

The compressive strength is very important for petroleum and other engineering studies. However, the effect of pore size and fluid distribution on the rock’s strength is not fully understood. We developed comprehensive research to study the controlling factors of the compressive strength based on low field nuclear magnetic resonance (NMR) measurements and pseudo-triaxial compression test for tight sandstones. The relationship between the compressive strength and the NMR obtained parameters are investigated completely, aiming for a better estimation of the compressive strength using the NMR data. The result shows that the rock’s strength is strongly controlled by the pore size distribution and the fluid existing state. Generally, the compressive strength is negatively correlated with the average transversal relaxation time, the movable water saturation, and the porosity, but positively correlated with the irreducible water saturation. The result reveals that the rock with larger pore radius and higher percentage of movable fluid is easier to reach the failure state. Further, the precision of the empirical model by multiple regression of the geometric mean of the relaxation time and the porosity is greatly improved compared with the model established by the brittle minerals, which is potentially to be use for geophysical prospecting when the NMR logging data is available.

Chemoreactome screening of aquacobalamin and heptamethyl ester of cyanoaquacobyrinic acid cytotoxic effects on tumor cells with experimental confirmation on BT-474 and A549 cell

Background. The search for an effective and safe pharmacotherapy for tumor diseases includes the evaluation of the action of candidate molecules on various types of tumor cells. Vitamin B12 and its derivatives are promising molecules whose properties can be controlled through chemical modifications.Objective: conducting in silico chemoreactom screening and in vitro experimental study of aquacobalamin and heptamethyl ester of cyanoaquacobyrinic acid (HECСA).Material and methods. Chemoreactome screening was carried out on the basis of a problem-oriented theory of chemograph isomorphism analysis, which is an extension of the algebraic approach to machine learning and recognition problems. Trainable algorithms for calculating chemical distances between molecules were used, on the basis of which the values of half-maximal inhibitory concentration (IC50) were calculated. Screening was carried out for 470 cultures of human tumor cells, including SNB19 (astrocytoma), HCT116 (colon cancer), HeLa (cervical carcinoma), BT-474 (breast duct carcinoma), and A549 (lung carcinoma) cell lines. Dicyanocobyric acid heptamethyl ester ((CN)2Cby(OCH3)7) was obtained by boiling a solution of vitamin B12 in methanol with sulfuric acid (1.0 M) for 4 days. HECСA ((CN)(H2O)Cby(OCH3)7) was obtained by vacuum drying an aqueous solution of (CN)2Cby(OCH3)7 (pH 4.0 and 25 °С). The ester structure and purity were confirmed by 1H nuclear magnetic resonance data, elemental analysis, and MALDI-ToF (matrix-assisted laser desorption/ionization time of flight) mass spectroscopy. Experimental studies of tumor cell cultures were carried out using the MTT testwith aquacobalamin and HECСA on cell lines of immortalized (telomerized) fibroblasts (Fb-hTERT), lung carcinoma (A549), and breast duct cancer (BT-474).Results. Chemoreactome screening of the effects of molecules on tumor cells made it possible to obtain estimates of cell growth IC50 for 470 tumor cell lines. Depending on cell line and vitamin B12 derivative molecule, IC50 values varied in a fairly wide range: from 15 to 2000 nM. In vitro studies on cultures of two human tumor cell lines (BT-474 and A549) and telomerized Fb-hTERT fibroblasts confirmed the cytotoxic effect of aquacobalamin and its hydrophobic derivative HECСA. It was shown that aquacobalamin had weak cytotoxic properties in the concentration range of 3.125–200 µg/l (IC50 > 200 nM), and HECСA significantly reduces the survival of BT-474 and A549 tumor cell lines at high concentrations (100–200 µg/l, IC50 about 100 nM).Conclusion. Correspondence was shown between the results of in silico chemoreactome screening and in vitro cell culture studies: IC50 values for HECСA were significantly lower than for aquacobalamin, and the conversion factor from chemoreactome estimates to experimental ones was almost the same (2.64 for BT-474, and 2.63 for A549). The results of chemoreactome screening for other tumor cell lines can be used to plan further cell experiments with vitamin B12 derivatives.

Investigation of carbon-based nanofluid imbibition processes in low-permeability reservoirs using nuclear magnetic resonance

Spontaneous imbibition has been demonstrated to be an important approach to enhance the oil recovery of unconventional reservoirs after hydraulic fracturing. Adding chemical agents to modulate the properties of the oil-water and oil-rock interfaces is a common method to enhance imbibition. Carbon-based nanofluid showed excellent ability to reduce interfacial tension and alter wettability due to their distinct surface properties and ultra-small particle size. However, there are few systemic studies on the imbibition process of carbon-based nanofluid and the unclear mechanism of the enhanced oil recovery (EOR) restricts their oilfield application. In this study, the carbon-based nanofluid was prepared by dispersing carbon nitride quantum dots (CNQDs) of 2.34 ± 0.34nm synthesized by citric acid and urea in deionized water. The spontaneous imbibition process of nanofluids was monitored by nuclear magnetic resonance (NMR) technology. The T2 relaxation distribution results suggested that the oil recovery of CNQDS nanofluid by spontaneous imbibition was 24.6%, which was 5% higher than that of nano-SiO2 nanofluid. Moreover, the variations of oil saturation profiles analyzed based on NMR data indicated that the maximum imbibition distance of the carbon-based nanofluid was about 20.34mm which is also larger than that of the nano-SiO2 nanofluid of 16.02mm. The oil saturation variations of saturated oil cores imbibed in carbon-based nanofluid was also significantly improved compared with nano-SiO2 nanofluid. This finding was attributed to the fact that compared with nano-SiO2 nanofluid, the CNQDs nanofluid can not only promote the fluid to enter deeper matrix, but also effectively reduce the residual oil saturation in the area that the nanofluid accesses to. The interfacial tension and contact angle measurements were conducted to reveal the underlying EOR mechanisms of CNQDs nanofluid. This study provides vital insights into the prospective application of carbon-based nanofluid in low-permeability reservoirs.

Cumulative Data of 1H and 13C NMR Signals and Specific Rotations of Eremophilane Sesquiterpenoids. 4. 10H-3-O-Furanoeremophilanes

1H and 13C nuclear magnetic resonance (NMR) data and specific rotations of eremophilane sesquiterpenoids are cumulated as a series of review articles. This fourth chapter focuses on furanoeremophilanes bearing 10H with C-3 oxygen functionality, and 175 10H-furanoeremophilanes with 3-O functionality are listed in 38 tables. Those with 15,6-lactones and 6,15-ethers are included in this chapter. Dihydrofurans, lactols, dimers, nor- and seco-compounds, and other related compounds, are not included in this chapter. These data may help chemists working in the area of natural products chemistry and synthetic scientists as well as computational chemists.

Highly Condensed and Super-Incompressible Be2PN3.

Although beryllium and its compounds show outstanding properties, owing to its toxic potential and extreme reaction conditions the chemistry of Be under high-pressure conditions has only been investigated sparsely. Herein, we report on the highly condensed wurtzite-type Be2PN3, which was synthesized from Be3N2 and P3N5 in a high-pressure high-temperature approach at 9 GPa and 1500 °C. It is the missing member in the row of formula type M2PN3 (M = Mg, Zn). The structure was elucidated by powder X-ray diffraction (PXRD), revealing that Be2PN3 is a double nitride, rather than a nitridophosphate. The structural model was further corroborated by 9Be and 31P solid-state nuclear magnetic resonance (NMR) spectroscopy. We present 9Be NMR data for tetrahedral nitride coordination for the first time. Infrared and energy-dispersive X-ray spectroscopy (FTIR and EDX), as well as temperature dependent PXRD complement the analytical characterization. Density functional theory (DFT) calculations reveal super-incompressible behavior and the remarkable hardness of this low-density material. The formation of Be2PN3 through a high-pressure high-temperature approach expands the synthetic access to Be-containing compounds and may open access to various multinary beryllium nitrides.

Highly Condensed and Super‐Incompressible Be2PN3

Although beryllium and its compounds show outstanding properties, owing to its toxic potential and extreme reaction conditions the chemistry of Be under high‐pressure conditions has only been investigated sparsely. Herein, we report on the highly condensed wurtzite‐type Be2PN3, which was synthesized from Be3N2 and P3N5 in a high‐pressure high‐temperature approach at 9 GPa and 1500 °C. It is the missing member in the row of formula type M2PN3 (M = Mg, Zn). The structure was elucidated by powder X‐ray diffraction (PXRD), revealing that Be2PN3 is a double nitride, rather than a nitridophosphate. The structural model was further corroborated by 9Be and 31P solid‐state nuclear magnetic resonance (NMR) spectroscopy. We present 9Be NMR data for tetrahedral nitride coordination for the first time. Infrared and energy‐dispersive X‐ray spectroscopy (FTIR and EDX), as well as temperature dependent PXRD complement the analytical characterization. Density functional theory (DFT) calculations reveal super‐incompressible behavior and the remarkable hardness of this low‐density material. The formation of Be2PN3 through a high‐pressure high‐temperature approach expands the synthetic access to Be‐containing compounds and may open access to various multinary beryllium nitrides.

A Semiflexible Tetrahydrazone Macrocycle for Binding of Pyrophosphate and Smaller Anions.

Macrocyclization has proven to be a useful design strategy in the development of efficient anion receptors. In addition to the ring size, the overall preorganization due to structural rigidity is key. To explore this in the context of developing an efficient pyrophosphate receptor, three macrocycles featuring a 26-membered interior ring size and similar H-bonding motifs have been synthesized, and their anion binding ability has been investigated. Computational studies and nuclear magnetic resonance (NMR) data showed different degrees of preorganization as a result of differences in flexibility. The interaction of the three macrocycles with chloride, dihydrogen phosphate, and dihydrogen pyrophosphate was investigated in solution by NMR and ultraviolet-visible spectroscopy and in the solid state by X-ray crystallography. The tetrahydrazone-based macrocycle featuring intermediate flexibility exhibited the best affinity for all three anions investigated. Our results suggest that in addition to the proper preorganization of binding groups in a macrocycle a certain degree of flexibility is also required for an optimal affinity with the target guest.

Six new polyphenolic metabolites isolated from the Suillus granulatus and their cytotoxicity against HepG2 cells.

Edible mushrooms are an important source of nutraceuticals and for the discovery of bioactive metabolites as pharmaceuticals. In this work, six new polyphenolic metabolites suillusol A-D (1-4), suillusinoic acid (5), ethyl suillusinoate (6), were isolated from the Suillus granulatus. The structures of new compounds were elucidated using high-resolution electrospray ionization mass spectroscopy, nuclear magnetic resonance data, and single-crystal X-ray diffraction analysis. As far as we know, compound 1 represents an unprecedented type of natural product and compound 3 represents a new type of polyphenol fungal pigment, which may be biosynthetically related to thelephoric acid. The cytotoxicity against HepG2 cells of the new compounds were also evaluated. Compound 2 demonstrate significant inhibitory activity against HepG2 cells with IC50 values of 10.85 μM, surpassing that of positive control cisplatin. Moreover, compound 1 and 3 also exhibited moderate cytotoxic activity with their IC50 values measured at 35.60 and 32.62 μM, respectively. Our results indicate that S. granulatus is a rich source of chemical constituents that may provide new lead compounds for the development of anticancer agents.

Fabrication, structure, characterization and emulsion application of citrate agar

In this study, citric acid successfully reacted with agar through the dry heat method, and citrate agar (CA) gel was used to stabilize O/W emulsions. The mechanisms of the CA structure and emulsion pH that affected emulsion stabilization were analyzed, and the application of CA gel emulsion (CAGE) was explored. Compared with native agar (NA), CA showed lower gel strength, higher transparency, and higher water contact angle. These changes indicate that a cross-linking reaction occurred, and it was demonstrated via FTIR and NMR. The emulsion properties were evaluated using particle size, ζ-potential, and the emulsification activity index. Results showed that CAGEs had a smaller particle size and lower ζ-potential than the native agar gel emulsion (NAGE). Meanwhile, confocal laser scanning microscopy confirmed that the CA gels stabilized the emulsions by forming a protective film around the oil droplets. Stability experiments revealed that CAGE (prepared with CA gel [DS = 0.145]) exhibited better stability than NAGE in the pH range of 3–11, and the rheological results further confirmed that the stability of the emulsions was influenced by the network structure and oil droplet interaction forces. Afterward, the application prospect of CAGE was evaluated by encapsulating vitamin D3 and curcumin.

Merging total synthesis and NMR technology for deciphering the realistic structure of natural 2,6-dideoxyglycosides.

The structural identification and efficient synthesis of bioactive 2,6-dideoxyglycosides are daunting challenges. Here, we report the total synthesis and structural revision of a series of 2,6-dideoxyglycosides from folk medicinal plants Ecdysanthera rosea and Chonemorpha megacalyx, which feature pregnane steroidal aglycones bearing an 18,20-lactone and glycans consisting of 2,6-dideoxy-3-O-methyl-β-pyranose residues, including ecdysosides A, B, and F and ecdysantheroside A. All the eight possible 2,6-dideoxy-3-O-methyl-β-pyranoside stereoisomers (of the proposed ecdysantheroside A) have been synthesized that testify the effective gold(I)-catalyzed glycosylation methods for the synthesis of various 2-deoxy-β-pyranosidic linkages and lays a foundation via nuclear magnetic resonance data mapping to identify these sugar units which occur promiscuously in the present and other natural glycosides. Moreover, some synthetic natural compounds and their isomers have shown promising anticancer, immunosuppressive, anti-inflammatory, and anti-Zika virus activities.

Genomic and Metabolomic Analyses of Nocardiopsis maritima YSL2 as the Mycorrhizosphere Bacterium of Suaeda maritima (L.) Dumort.

Nine bacteria were isolated from the episphere of Suaeda maritima (L.) Dumort. Among them, the bacterial strain YSL2 displayed the highest antimicrobial activity on agar plates and exhibited significant novelty compared with other bacteria based on 16S rRNA analysis. Consequently, Nocardiopsis maritima YSL2T was subjected to phenotypic characterization and whole-genome sequencing. Phylogenetic analysis revealed its close association with Nocardiopsis aegyptia SNG49T. Furthermore, genomic analysis of strain YSL2T revealed the presence of various gene clusters, indicating its potential for producing antimicrobial secondary metabolites. Upon cultivation on a large scale, maritiamides A and B (1 and 2) were isolated and characterized as cyclic hexapeptides based on nuclear magnetic resonance, ultraviolet, infrared, and mass spectrometric data. The absolute configurations of the amino acid residues in the maritiamides were determined through chiral derivatization, utilizing FDAA and GITC. Maritiamides 1 and 2 exhibited promising antibacterial activities against Staphylococcus epidermidis and weakly inhibited the growth of Escherichia coli and Pseudomonas fluorescens.

Core Analysis Using Nuclear Magnetic Resonance

Core analysis is critical for oil and gas exploration and recovery. Nuclear magnetic resonance (NMR) has been widely applied to the petroleum industry for many years, and NMR core analysis plays an important role in supporting borehole NMR formation evaluation and understanding the mechanisms of petrophysics and petrochemistry. It’s unfortunate, however, that there has been a lack of commented descriptions of the basic procedures for NMR rock core analysis in the literature, which has led to issues of comparability and repeatability of NMR measurements between different laboratories. In this paper, we present a brief guideline for NMR rock core analysis of conventional T2, T1, T1-T2, and D-T2 measurements. As an established procedure in daily laboratory work, NMR core analysis includes three sophisticated steps: rock sample preparation, an NMR experiment, and data analysis. The acquisition and saturation of rock samples are described, and corresponding solutions are also considered. Detailed NMR experimental measurements, data setting, and calibration are addressed. Laplace inversion for different NMR experiments and models for estimation of porosity, irreducible water, permeability, pore structure, and oil saturation are included. The aim of this paper is to try to standardize general NMR experiments for rock core analysis.

Measurements of nematic susceptibility with phase sensitive nuclear magnetic resonance in pulsed strain fields.

We present nuclear magnetic resonance data in BaFe2As2 in the presence of pulsed strain fields that are interleaved in time with the radio frequency excitation pulses. In this approach, the preceding nuclear magnetization acquires a phase shift that is proportional to the strain and pulse time. The sensitivity of this approach is limited by the homogeneous decoherence time, T2, rather than the inhomogeneous linewidth. We measure the nematic susceptibility as a function of temperature and demonstrate a three orders of magnitude improvement in sensitivity. This approach will enable studies of the strain response in a broad range of materials that previously were inaccessible due to inhomogeneous broadening.

Illegal products containing selective androgen receptor modulators purchased online from Italy: health risks for consumers.

Selective androgen receptor modulators (SARMs) are small synthetic drug molecules that are still not approved as medicine in Europe or the United States but are sold on illegal websites to improve sport performance, particularly bodybuilding. To address the quality issues of illegal SARM products and their increasing diffusion in Italy with their potential health risks for consumers. Web-based tools were used to investigate retail websites, trending searches, and information exchange via social media. Thirteen SARM products, purchased on retail websites accessible from Italy, were subject to visual inspection and chemical analysis by mass spectrometry and quantitative nuclear magnetic resonance. The primary outcome was demonstration of additional health risks due to the illicit presence of other active ingredients, contamination, and misdosage in SARM products sold on the internet. The secondary outcome was to show the increasing trend of interest in Italy for these products. Most websites reported misleading information; specifically, the statement "for research only" was reported notwithstanding indications on dosage and training phases. The trending search showed that interest toward SARMs increased in Italy in the last years. The use of these products is clearly encouraged by the emerging phenomenon of "broscience" as revealed in socials. Visual inspection evidenced nonconform labeling. Qualitative analysis confirmed the presence of the stated SARM in about 70% of samples. In 23% of samples, the expected SARM was not detected but a different one instead, and in 1 sample, no SARMs were detected. Other undeclared pharmaceutical substances (tamoxifen, clomifene, testosterone, epimethandienone, tadalafil) were measured in 30% of samples. The copresence of >1 active substance was observed in >60% of samples. Quantitative nuclear magnetic resonance data showed nonuniform content ranging from 30% to 90% of the label claim. The use of SARMs, in the presence of unexpected life-threatening reactions in persons using the products to increase sport performance, should be assessed. This investigation involved an integrated approach to study SARM products and related sociologic aspects. The main shortcomings are the limited number of samples and retail websites in the clear web investigated. SARMs sold online as food supplement-like products represent a health hazard due to the presence of unapproved and undeclared active substances. The presence of contaminants clearly indicates the absence of good manufacturing practices in the production, which increases the health risks.

From NMR to AI: Designing a Novel Chemical Representation to Enhance Machine Learning Predictions of Physicochemical Properties.

A novel approach to the utilization of nuclear magnetic resonance (NMR) spectroscopy data in the prediction of logD through machine learning algorithms is shown. In the analysis, a data set of 754 chemical compounds, organized into 30 clusters, was evaluated using advanced machine learning models, such as Support Vector Regression (SVR), Gradient Boosting, and AdaBoost, and comprehensive validation and testing methods were employed, including 10-fold cross-validation, bootstrapping, and leave-one-out. The study revealed the superior performance of the Bucket Integration method for dimensionality reduction, consistently yielding the lowest root mean square error (RMSE) across all data sets and normalization schemes. The SVR prediction models demonstrated remarkable computational efficiency and low cost, with the best RMSE value reaching 0.66. Our best model outperformed existing tools like JChem Suite's logD Predictor (0.91) and CplogD (1.27), and a comparison with traditional molecular representations yielded a comparable RMSE (0.50), emphasizing the robustness of our NMR data integration. The widespread availability of NMR data in pharmaceutical and industrial research presents an untapped resource for predictive modeling, highlighting the need for accessible methodologies like ours that complement the analytical toolbox beyond conventional 2D approaches. Our approach, designed to leverage the rich spatial data from NMR spectroscopy, provides additional insights and enriches drug discovery and computational chemistry with a freely accessible tool.

Bayesian NMR petrophysical characterization

Identification of reservoir rock types is necessary for the exploration and recovery of oil and gas. It involves determining the petrophysical properties of rocks such as porosity and permeability which play a significant role in developing reservoir models, estimating the volumes of oil and gas reserves, and planning production methods. Nuclear magnetic resonance (NMR) technology is a fast and accurate tool for petrophysical rock characterization. The distributions of relaxation times (T2 distributions) offer valuable insights into the distribution of pore sizes in rocks, and these distributions are closely linked to important petrophysical parameters like porosity, permeability, and bound fluid volume (BFV).This work introduces a Bayesian estimation method for analyzing NMR data. The Bayesian approach uses prior knowledge of T2 distributions in the form of the prior mean and covariance. The Bayesian approach combines prior knowledge with observed data to obtain improved estimation. We use the Bayesian estimation method where prior information regarding the rock sample type, for example shale, is available.The estimators were evaluated on decay data simulated from synthesized distributions that replicate the features of experimental T2 distributions of three types of reservoir rocks. We compared the performance of the Bayesian method with two existing methods using porosity, bound fluid volume (BFV) geometric mean (T2LM) and root mean square error (RMSE) of the estimated T2 distribution as evaluation criteria. Additional experiments were carried out using experimental T2 distributions to validate the results.The performance of the Bayesian methods was also tested using mismatched priors.The experimental results illustrate that the Bayesian estimator outperforms other estimators in estimating the T2 distribution. The Bayesian method also outperforms the ILT method in estimating derived petrophysical properties except in cases where the noise level is below 0.1 and the T2 distributions are associated with short relaxation times.