Molecular Electrostatic Potentials and Chemical Reactivity

Fenamates and ibuprofen as foundational components in the synthesis of innovative, targeted COX-2 anti-inflammatory drugs, undergoing thorough biopharmacological assessments and in-silico computational studies

Cyclooxygenase-2 plays a vital role in inflammation by catalyzing arachidonic acid conversion toward prostaglandins, making it a prime therapeutic objective. Selective COX-2 inhibitors represent significant progress in anti-inflammatory therapy, offering improved efficacy and fewer side effects. This study describes the synthesis of novel anti-inflammatory compounds from established pharmaceutically marketed agents like fenamates III-V and ibuprofen VI. Through rigorous in vitro testing, compounds 7b-c, and 12a-b demonstrated substantial in vitro selective inhibition, with IC50 values of 0.07 to 0.09 μM, indicating potent pharmacological activity. In vivo assessment, particularly focusing on compound 7c, revealed significant anti-inflammatory effects. Markedly, it demonstrated the highest inhibition of paw thickness (58.62 %) at the 5-hr mark compared to the carrageenan group, indicating its potency in mitigating inflammation. Furthermore, it exhibited a rapid onset of action, with a 54.88 % inhibition observed at the 1-hr mark. Subsequent comprehensive evaluations encompassing analgesic efficacy, histological characteristics, and toxicological properties indicated that compound 7c did not induce gastric ulcers, in contrast to the ulcerogenic tendency associated with mefenamic acid. Moreover, compound 7c underwent additional investigations through in silico methodologies such as molecular modelling, field alignment, and density functional theory. These analyses underscored the therapeutic potential and safety profile of this novel compound, warranting further exploration and development in the realm of pharmaceutical research.

Insight into crystal structures and identification of potential styrylthieno[2,3-b]pyridine-2-carboxamidederivatives against COVID-19 Mpro through structure-guided modeling and simulation approach

Anti-SARS-CoV-2 drugs are urgently needed to prevent the pandemic and for immunization. Their protease inhibitor treatment for COVID-19 has been used in clinical trials. In Calu-3 and THP1 cells, 3CL SARS-CoV-2 Mpro protease is required for viral expression, replication, and the activation of the cytokines IL-1, IL-6, and TNF-. The Mpro structure was chosen for this investigation because of its activity as a chymotrypsin-like enzyme and the presence of a cysteine-containing catalytic domain. Thienopyridine derivatives increase the release of nitric oxide from coronary endothelial cells, which is an important cell signaling molecule with antibacterial activity against bacteria, protozoa, and some viruses. Using DFT calculations, global descriptors are computed from HOMO-LUMO orbitals; the molecular reactivity sites are analyzed from an electrostatic potential map. NLO properties are calculated, and topological analysis is also part of the QTAIM studies. Both compounds 1 and 2 were designed from the precursor molecule pyrimidine and exhibited binding energies (-14.6708 kcal/mol and -16.4521 kcal/mol). The binding mechanisms of molecule 1 towards SARS-COV-2 3CL Mpro exhibited strong hydrogen bonding as well as Vdw interaction. In contrast, derivative 2 was bound to the active site protein's active studied that several residues and positions, including (His41, Cys44, Asp48, Met49, Pro52, Tyr54, Phe140, Leu141, Ser144, His163, Ser144, Cys145, His164, Met165, Glu166, Leu167, Asp187, Gln189, Thr190, and GLn192) are critical for the maintenance of inhibitors inside the active pocket. Molecular docking and 100 ns MD simulation analysis revealed that Both compounds 1 and 2 with higher binding affinity and stability toward the SARS-COV-2 3CL Mpro protein. Binding free energy calculations and other MD parameters support the finding.Communicated by Ramaswamy H. Sarma.

A synergistic investigation of azo-thiazole derivatives incorporating thiazole moieties: a comprehensive exploration of their synthesis, characterization, computational insights, solvatochromism, and multimodal biological activity assessment

In the present study, a novel series of azo-thiazole derivatives (3a-c) containing a thiazole moiety was successfully synthesized. The structure of these derivatives was examined by spectroscopic techniques, including 1H NMR, 13C NMR, FT-IR, and HRMS. Further, the novel synthesized compounds were evaluated for their in vitro biological activities, such as antibacterial and anti-inflammatory activities, and an in silico study was performed. The antibacterial results demonstrated that compounds 3a and 3c (MIC = 10 μg mL-1) have a notable potency against Staphylococcus aureus compared to azithromycin (MIC = 40 μg mL-1). Alternatively, compound 3b displayed a four-fold higher potency (24 recovery days, 1.83 mg day-1) than Hamazine (28 recovery days, 4.14 mg day-1) in promoting burn wound healing, and it also exhibited a comparable inhibitory activity against screened bacterial pathogens compared to the reference drug. Docking on 1KZN, considering the excellent impact of compounds on the crystal structure of E. coli1KZN, a 24 kDa domain, in complex with clorobiocin, indicated the close binding of compounds 3a-c with the active site of the 1KZN protein, which is consistent with their observed biological activity. Additionally, we conducted molecular dynamics simulations on the docked complexes of compounds 3a-c with 1KZN retrieved from the PDB to assess their stability and molecular interactions. Furthermore, we assessed their electrochemical characteristics via DFT calculations. Employing PASS and pkCSM platforms, we gained insights into controlling the bioactivity and physicochemical features of these compounds, highlighting their potential as new active agents.

Theoretical Study on the Coordination and Separation Capacity of Macrocyclic N-Donor Extractants for Am(III)/Eu(III)

Designing ligands that can effectively separate actinide An(III)/lanthanide Ln(III) in the solvent extraction process remains one of the key issues in the treatment of accumulated spent nuclear fuel. Nitrogen donor ligands are considered as promising extractants for the separation of An(III) and Ln(III) due to their environmental friendliness. Four new macrocyclic N-donor hexadentate extractants were designed and their coordination with Am(III) and Eu(III), as well as their extraction selectivity and separation performance for Am(III) and Eu(III), were investigated by scalar relativistic density functional theory. A variety of theoretical methods have been used to evaluate the properties of the four ligands and the coordination structures, bonding properties, and thermodynamic properties of the complexes formed by the four ligands with Am(III) and Eu(III). The results of various wavefunction analysis methods including NBO analysis, quantum theory of atoms in molecules (QTAIM) analysis, and so on show that Am(III) has a stronger coordination ability with the ligands than Eu(III) due to the Am 5f orbitals more involved in bonding with the ligands than the Eu 4f orbitals, and the bonding environment of the N-donor in the ligand has a significant effect on its coordination ability of the metal ions. Thermodynamic analysis of the solvent extraction process shows that all of the four N-containing macrocyclic ligands have good extraction selectivity and separation performance for Am(III) and Eu(III). This study provides theoretical support for designing potential nitrogen-containing macrocyclic extractants with excellent separation performance.

σ versus π-radical: Tuning the electronic nature of neutral carbon (I) compounds with three non-bonding electrons

The bonding and reactivity of the hypo-coordinated compounds with one, two, and four non-bonding electrons namely, carbon-centered free radical, carbenes, and carbones were well earlier established. Here, we report stability, bonding and reactivity of compounds RCL, where R is one-electron donor group (R = CH₃ (a), CHO (b), and NO₂ (c)) and L is two-electron donor ligand (L = cAAC (1), CO (2), NHC (3) and PMe₃ (4)), having three non-bonding electrons. The ground states of molecules exist in a doublet with a lone pair of electrons and an unpaired electron at the central carbon atom (C1). The spin hops over from π- to σ-type orbitals is observed as the π-acceptor strength of the donor ligand increases. The replacement of the methyl group by CHO and NO₂ indicate that the cAAC and CHO substituted compounds gives a σ-radical except in compound 2c. These molecules show very high proton affinity and exothermic reaction energy for the hydrogen atom addition indicating dual reactivity namely, radical and lone pair reactivity.

Theoretical Probing of Size-Selective Crown Ether Macrocycle Ligands for Transplutonium Element Separation

Effective separation and recovery of chemically similar transplutonium elements from adjacent actinides is extremely challenging in spent fuel reprocessing. Deep comprehension of the complexation of transplutonium elements and ligands is significant for the design and development of ligands for the in-group separation of transplutonium elements. Because of experimental difficulties of transplutonium elements, theoretical calculation has become an effective means of exploring transplutonium complexes. In this work, we systematically investigated the coordination mechanism between transplutonium elements (An = Am, Cm, Bk, Cf) and two crown ether macrocyclic ligands [N,N'- bis[(6-carboxy-2-pyridyl)methyl]-1,10-diaza-18-crown-6 (H₂bp18c6) and N,N'-bis[(6-methylphosphinic-2-pyridyl)methyl]-1,10-diaza-18-crown-6 (H₂bpp18c6)] through quasi-relativistic density functional theory. The extraction complexes of [Anbp18c6]⁺ and [Anbpp18c6]⁺ possess similar geometrical structures with actinide atoms located in the cavity of the ligands. Bonding nature analysis indicates that the coordination ability of the coordinating atoms in pendent arms is stronger than that in the crown ether macrocycle because of the limitation of the macrocycle. Most of the coordination atoms of the H₂bp18c6 ligand have a stronger ability to coordinate with metal ions than those of the H₂bpp18c6 ligand. In addition, the bonding strength between the metal ions and ligands gradually weakens from Am to Cf, which is mainly attributed to the size selectivity of the ligands. Thermodynamic analysis shows that the H₂bp18c6 ligand has a stronger extraction capacity than the H₂bpp18c6 ligand, while the H₂bpp18c6 ligand is superior in terms of the in-group separation ability. The extraction capacity of the two ligands for metal ions gradually decreases across the actinide series, indicating that these crown ether macrocycle ligands have size selectivity for these actinide cations as a result of steric constraint of the crown ether ring. We hope that these results offer theoretical clues for the development of macrocycle ligands for in-group transplutonium separation.

Bifunctional Fe for Induced Graphitization and Catalytic Ozonation Based on a Fe/N-Doped Carbon-Al2O3 Framework: Theoretical Calculations Guided Catalyst Design and Optimization

Heterogeneous catalytic ozonation is regarded as a feasible technology in advanced wastewater treatment. Catalytic performance, mass transfer, and mechanical strength are the key elements for large-scale applications of catalysts. To optimize those elements, Fe was selected for its dual role in graphitization and catalytic ozonation. A Fe/N-doped micron-scale carbon-Al2O3 framework (CAF) was designed and applied to a fluidized catalytic process for the treatment of secondary effluent from coal gasification. The chemical oxygen demand removal rate constant and the hydroxyl radical generation efficiency (Rct) of the Fe/N-doped CAF were 190% and 429% higher than those of pure ozone, respectively. Theoretical calculations revealed that higher Fe valence promoted ozone decomposition, which implied increasing FeIII content for further catalyst optimization. The rate constant and Rct with a higher FeIII-proportion catalyst were increased by 13% and 16%, respectively, compared to those with the lower one. Molecular dynamics and density functional theory calculations were performed to analyze the reaction kinetics qualitatively and quantitatively. The energy barrier corresponding to FeIII configuration was 1.32 kcal mol-1, 27% lower than that for FeII configuration. These theoretical calculations guided the catalyst optimization and provided a novel solution for designing ozonation catalysts. The Fe/N-doped CAF demonstrated a great potential for practical applications.

15.3% Efficiency All-Small-Molecule Organic Solar Cells Achieved by a Locally Asymmetric F, Cl Disubstitution Strategy

Single junction binary all-small-molecule (ASM) organic solar cells (OSCs) with power conversion efficiency (PCE) beyond 14% are achieved by using non-fullerene acceptor Y6 as the electron acceptor, but still lag behind that of polymer OSCs. Herein, an asymmetric Y6-like acceptor, BTP-FCl-FCl, is designed and synthesized to match the recently reported high performance small molecule donor BTR-Cl, and a record efficiency of 15.3% for single-junction binary ASM OSCs is achieved. BTP-FCl-FCl features a F,Cl disubstitution on the same end group affording locally asymmetric structures, and so has a lower total dipole moment, larger average electronic static potential, and lower distribution disorder than those of the globally asymmetric isomer BTP-2F-2Cl, resulting in improved charge generation and extraction. In addition, BTP-FCl-FCl based active layer presents more favorable domain size and finer phase separation contributing to the faster charge extraction, longer charge carrier lifetime, and much lower recombination rate. Therefore, compared with BTP-2F-2Cl, BTP-FCl-FCl based devices provide better performance with FF enhanced from 71.41% to 75.36% and J sc increased from 22.35 to 24.58 mA cm-2, leading to a higher PCE of 15.3%. The locally asymmetric F, Cl disubstitution on the same end group is a new strategy to achieve high performance ASM OSCs.

Modelling the structural and reactivity landscapes of tucatinib with special reference to its wavefunction-dependent properties and screening for potential antiviral activity

HER-2 type breast cancer is one of the most aggressive malignancies found in women. Tucatinib is recently developed and approved as a potential medicine to fight this disease. In this manuscript, we present the gross structural features of this compound and its reactivity and wave function properties using computational simulations. Density functional theory was used to optimise the ground state geometry of the molecule and molecular docking was used to predict biological activity. As the electrons interact with electromagnetic radiations, electronic excitations between different energy levels are analysed in detail using time-dependent density functional theory. Various intermolecular and intermolecular interactions are analysed and reaction sites for attacking electrophiles and nucleophiles identified. Information entropy calculations show that the compound is inherently stable. Docking with COVID-19 proteins show docking score of − 9.42, − 8.93, − 8.45 and − 8.32 kcal/mol respectively indicating high interaction between the drug and proteins. Hence, this is an ideal candidate to study repurposing of existing drugs to combat the pandemic.

Controlling the outcome of SN2 reactions in ionic liquids: from rational data set design to predictive linear regression models

Rate constants for a bimolecular nucleophilic substitution (SN2) process in a range of ionic liquids are correlated with calculated parameters associated with the charge localisation on the cation of the ionic liquid (including the molecular electrostatic potential). Simple linear regression models proved effective, though the interdependency of the descriptors needs to be taken into account when considering generality. A series of ionic liquids were then prepared and evaluated as solvents for the same process; this data set was rationally chosen to incorporate homologous series (to evaluate systematic variation) and functionalities not available in the original data set. These new data were used to evaluate and refine the original models, which were expanded to include simple artificial neural networks. Along with showing the importance of an appropriate data set and the perils of overfitting, the work demonstrates that such models can be used to reliably predict ionic liquid solvent effects on an organic process, within the limits of the data set.

Optimization of structures, biochemical properties of ketorolac and its degradation products based on computational studies

BACKGROUND

Ketorolac (KTR) is used as an analgesic drug with an efficacy close to that of the opioid family. It is mainly used for the short term treatment of post-operative pain. It can inhibit the prostaglandin synthesis by blocking cyclooxygenase (COX).

METHODS

In this investigation, the inherent stability and biochemical interaction of Ketorolac (KTR) and its degradation products have been studiedon the basis of quantum mechanical approaches. Density functional theory (DFT) with B3LYP/ 6-31G (d) has been employed to optimize the structures. Thermodynamic properties, frontier molecular orbital features, dipole moment, electrostatic potential, equilibrium geometry, vibrational frequencies and atomic partial charges of these optimized structureswere investigated. Molecular docking has been performed against prostaglandin H2 (PGH2) synthase protein 5F19 to search the binding affinity and mode(s). ADMET prediction has performed to evaluate the absorption, metabolism and carcinogenic properties.

RESULTS

The equilibrium geometry calculations support the optimized structures. Thermodynamic results disclosed the thermal stability of all structures. From molecular orbital data, all the degradents are chemically more reactive than parent drug (except K3). However, the substitution of carboxymethyl radicalin K4 improved the physicochemical properties and binding affinity. ADMET calculations predict the improved pharmacokinetic and non-carcinogenic properties of all degradents.

CONCLUSION

Based on physicochemical, molecular docking, and ADMET calculation, this study can be helpful to understand the biochemical activities of Ketorolac and its degradents and to design a potent analgesic drug.

Close contacts and noncovalent interactions in crystals

Close contacts, defined as interatomic separations less than the sum of the respective van der Waals radii, are commonly invoked to identify attractive nonbonded interactions in crystal lattices. While this is often effective, it can also be misleading because (a) there are significant uncertainties associated with van der Waals radii, and (b) it may not be valid to attribute the interactions solely to specific pairs of atoms. The interactions within crystal lattices are Coulombic, and the strongest positive and/or negative regions do not always correspond to the positions of atoms; they are sometimes located between atoms. Examples of both types are given and discussed, focusing in particular upon σ-hole interactions.

Design of ultrathin hybrid membranes with improved retention efficiency of molecular dyes

Nanocellulose–graphene oxide ultrathin coatings for water purification membranes with excellent swelling resistance, permeability and dyes retention are presented.

Molecular Electrostatic Potential: A New Tool to Predict the Lithiation Process of Organic Battery Materials

This work is pioneering to introduce molecular electrostatic potential (MESP) to investigate the interaction between lithium ions and organic electrode molecules. The electrostatic potential on the van der Waals surface of the electrode molecule is calculated, and then the coordinates and relative values of the local minima of MESP can be correlated to the Li binding sites and sequence on an organic small molecule, respectively. This suggests a gradual lithiation process. Similar calculations are extended to polymers and even organic crystals. The operation process of MESP for these systems is explained in detail. Through providing accurate and visualizable lithium binding sites, MESP can give precise prediction of the lithiated structures and reaction mechanism of organic electrode materials. It will become a new theoretical tool for determining the feasibility of organic electrode materials for alkali metal ion batteries.

N-H bond cleavage of ammonia on graphene-like B36 borophene: DFT studies

Ammonia N-H bond cleavage at metal-free substrates has attracted great attention because of its industrial importance. Here, we investigate the dissociative adsorption of ammonia onto the surface of a B36 borophene sheet by means of density functional theory calculations. We show that the N-H bond may be broken at the edges of B36 even at room temperature, regarding the small energy barrier of 14.1-19.3 kcal mol(-1) at different levels of theory, and more negative Gibbs free energy change. Unlike basis set size, the kind of exchange correlation functional significantly affects the electronic properties of the studied systems. Also, by increasing the percentage of Hartree Fock (HF) exchange of density functionals, the activation and adsorption energies are lowered. A linear relationship between the highest occupied molecular orbital or lowest unoccupied molecular orbital of B36 borophene and the %HF exchange of functionals is predicted. Our work reveals that pure whole boron nanosheets may be promising metal-free materials in N-H bond cleavage, which would raise the potential application of these sheets.

FT-IR, FT-Raman, UV/Vis spectra and fluorescence imaging studies on 2-(bromoacetyl)benzo(b)furan by ab initio DFT calculations

The vibrational and electronic properties of 2-(bromoacetyl)benzo(b)furan have been studied in the ground state using experimental techniques (FT-IR, FT-Raman and UV) and density functional theory (DFT) employing B3LYP exchange correlation with the 6-31G(d,p) basis set. The theoretically calculated optimized parameters, vibrational frequencies etc., were compared with the experimental values, which yield good agreement between the observed and calculated values. The complete assignments of fundamental modes were performed on the basis of the potential energy distribution (PED). UV-visible spectrum of the compound was recorded in the region 300-600 nm and compared with the theoretical spectrum obtained from SAC-CI calculations. A good agreement is observed between the experimental and theoretical spectra. Fluorescence microscopic imaging studies proved that the compound can be used as one of the potential light sources in the yellow region with suitable excitation. Further, the predicted electronic transitions between the MOs 47→64, 52→62, 56→65, 56→72, 56→77 of the compound show a strong line at 569.8 nm.

Modeling biophysical and biological properties from the characteristics of the molecular electron density, electron localization and delocalization matrices, and the electrostatic potential

The electron density and the electrostatic potential are fundamentally related to the molecular hamiltonian, and hence are the ultimate source of all properties in the ground- and excited-states. The advantages of using molecular descriptors derived from these fundamental scalar fields, both accessible from theory and from experiment, in the formulation of quantitative structure-to-activity and structure-to-property relationships, collectively abbreviated as QSAR, are discussed. A few such descriptors encode for a wide variety of properties including, for example, electronic transition energies, pK(a)'s, rates of ester hydrolysis, NMR chemical shifts, DNA dimers binding energies, π-stacking energies, toxicological indices, cytotoxicities, hepatotoxicities, carcinogenicities, partial molar volumes, partition coefficients (log P), hydrogen bond donor capacities, enzyme-substrate complementarities, bioisosterism, and regularities in the genetic code. Electronic fingerprinting from the topological analysis of the electron density is shown to be comparable and possibly superior to Hammett constants and can be used in conjunction with traditional bulk and liposolubility descriptors to accurately predict biological activities. A new class of descriptors obtained from the quantum theory of atoms in molecules' (QTAIM) localization and delocalization indices and bond properties, cast in matrix format, is shown to quantify transferability and molecular similarity meaningfully. Properties such as "interacting quantum atoms (IQA)" energies which are expressible into an interaction matrix of two body terms (and diagonal one body "self" terms, as IQA energies) can be used in the same manner. The proposed QSAR-type studies based on similarity distances derived from such matrix representatives of molecular structure necessitate extensive investigation before their utility is unequivocally established.

Molecular conformational analysis, vibrational spectra and normal coordinate analysis of trans-1,2-bis(3,5-dimethoxy phenyl)-ethene based on density functional theory calculations

The conformational behavior and structural stability of trans-1,2-bis(3,5-dimethoxy phenyl)-ethene (TDBE) were investigated by using density functional theory (DFT) method with the B3LYP/6-311++G(d,p) basis set combination. The vibrational wavenumbers of TDBE were computed at DFT level and complete vibrational assignments were made on the basis of normal coordinate analysis calculations (NCA). The DFT force field transformed to natural internal coordinates was corrected by a well-established set of scale factors that were found to be transferable to the title compound. The infrared and Raman spectra were also predicted from the calculated intensities. The observed Fourier transform infrared (FTIR) and Fourier transform (FT) Raman vibrational wavenumbers were analyzed and compared with the theoretically predicted vibrational spectra. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP).

Vibrational and electronic spectra of 5-Acetyluracil - an experimental and theoretical study

The vibrational and electronic properties of 5-Acetyluracil have been investigated in the ground state using experimental techniques (FT-IR, FT-Raman and UV spectra) and density functional theory (DFT) employing B3LYP exchange correlation with the 6-31G(d,p) basis set. The theoretically calculated optimized parameters, vibrational frequencies, etc., were compared with the experimental values, which yield good agreement between the observed and calculated values. The complete assignments of fundamental modes were performed on the basis of the potential energy distribution (PED). UV-vis spectrum of the compound was recorded in the region of 300-700 nm and compared with the theoretical spectrum obtained from time-dependent DFT(TD-DFT). Fluorescence microscopic imaging studies proved that the compound can be used as one of the potential light sources in the green region.

Electron-density descriptors as predictors in quantitative structure--activity/property relationships and drug design

The use of electron density-based molecular descriptors in drug research, particularly in quantitative structure--activity relationships/quantitative structure--property relationships studies, is reviewed. The exposition starts by a discussion of molecular similarity and transferability in terms of the underlying electron density, which leads to a qualitative introduction to the quantum theory of atoms in molecules (QTAIM). The starting point of QTAIM is the topological analysis of the molecular electron-density distributions to extract atomic and bond properties that characterize every atom and bond in the molecule. These atomic and bond properties have considerable potential as bases for the construction of robust quantitative structure--activity/property relationships models as shown by selected examples in this review. QTAIM is applicable to the electron density calculated from quantum-chemical calculations and/or that obtained from ultra-high resolution x-ray diffraction experiments followed by nonspherical refinement. Atomic and bond properties are introduced followed by examples of application of each of these two families of descriptors. The review ends with a study whereby the molecular electrostatic potential, uniquely determined by the density, is used in conjunction with atomic properties to elucidate the reasons for the biological similarity of bioisosteres.

Characterization of "mini-nucleotides" as P2X receptor agonists in rat cardiomyocyte cultures. An integrated synthetic, biochemical, and theoretical study

The design and synthesis of "mini-nucleotides", based on a xanthine-alkyl phosphate scaffold, are described. The physiological effects of the new compounds were evaluated in rat cardiac cell culture regarding Ca(2+) elevation and contractility. The results indicate biochemical and physiological profiles similar to those of ATP, although at higher concentrations. The biological target molecules of these "mini-nucleotides" were identified by using selective P2-R and A(1)-R antagonists and P2-R subtype selective agonists. On the basis of these results and of experiments in Ca(2+) free medium, in which [Ca(2+)](i) elevation was not observed, we concluded that interaction of the analogues is likely with P2X receptor subtypes, which causes Ca(2+) influx. Theoretical calculations analyzing electronic effects within the series of xanthine-alkyl phosphates were performed on reduced models at quantum mechanical levels. Calculated dipole moment vectors, electrostatic potential maps, and volume parameters suggest an explanation for the activity or inactivity of the synthesized derivatives and predict a putative binding site environment for the active agonists. Xanthine-alkyl phosphate analogues proved to be selective agents for activation of P2X-R subtypes, whereas ATP activated all P2-R subtypes in cardiac cells. Therefore, these analogues may serve as prototypes of selective drugs aiming at cardiac disorders mediated through P2X receptors.