The semiempirical Atoms-in-a-Molecule (AIM) hardness matrix, η, is defined, using the usual finite difference formula, ηii = Ii – Ai, for diagonal AIM and Ohno ηij 1/(a2 + R)1/2, off-diagonal hardness. formula shown to exhibit correct asymptotic behavior satisfies relevant stability criterion. normal displacements in electron populations are examined pyrrole N-methyl pyrrole, their relation polarization channels briefly discussed. new matrix also tested by comparing predicted global...

A different localization scheme for the elongation method is developed based on regional molecular orbitals. This more efficient and accurate than previous one especially covalently bonded systems with strongly delocalized π electrons. Ab initio test calculations have been performed three model systems: water chains, polyglycine, cationic cyanine chains. The dependence size of starting clusters effect basis set are investigated. Our results compared conventional ab it found in all cases that...

We introduce a new tool (single exponential decay detector: SEDD) to extract information about bonding and localization in atoms, molecules, or molecular assemblies. The practical evaluation of SEDD does not require any explicit the orbitals. only quantity needed is electron density (calculated experimental) its derivatives up second order.

Interactions of the β-cyclodextrin (β-CD) ligand with Na+, Cu+, Mg2+, Zn2+, and Al3+ cations were investigated using density functional theory modeling. The objective this study was to give insight into mechanism cation complexation. Two groups conformers found. first group preserved initial orientation glucopyranose residues inside β-CD ligand. mutual strongly affected by in second conformers. system interaction energy decomposed electrostatic (ES), Pauli orbital contributions Ziegler–Rauk...

The charge-transfer energy in water dimer is analyzed. analysis based on self-consistent charge and configuration method for subsystems (SCCCMS). SCCCMS, as such, not restricted to any computational schemes can be applied at Hartree–Fock (HF), post-HF, density functional levels of theory. In our approach, the interaction decomposed into deformation (DEF), electrostatic (ES), polarization (P), transfer (CT), exchange (EX) [exchange–correlation (XC)] contributions. CT derived from surface...

Abstract The elongation method uses the concept of locality and works in a regionally localized molecular orbital basis set. In this system is partitioned into several frozen fragments an active one. If coupling between given fragment space small enough, one can develop cutoff scheme for effectively discarding former all further calculations. At Hartree–Fock level many two‐electron integrals are thereby eliminated, leading to reduction self‐consistent field computation time. test...

Literature data indicate that some calixarene derivatives with antimicrobial activities may be useful as drugs; one of the aspects biological activity different classes antibiotics concerns interactions lipid membranes. Here, possibility incorporation and/or translocation three amphiphilic p-tert-butylcalix[4]arene across membranes was studied using monolayers. The used have 6-aminopenicillanic acid or benzylpenicillin moieties grafted in alternate positions at lower rim;...

In the present study, nucleophilic properties of adenine and guanine are examined by means density functional theory. H+ is used as a model electrophile. Two modes attack on bases considered: neutral molecule anion. Solvent effects modeled polarizable continuum model. Regioselectivity studied analyzing two contributions. The first one energetic ordering tautomers. second relative inherent reactivity sites in bases. Atomic softnesses calculated charge sensitivity analysis employed for this...

Doxorubicin (DOX) is a commonly used chemotherapeutic drug, from the anthracycline class, which genotoxic to neoplastic cells via DNA intercalation mechanism. It effective and universal; however, it also causes numerous side effects. The most serious of them are cardiotoxicity decrease in number myeloid cells. For this reason, targeted DOX delivery systems desirable, since they would allow lowering drug dose therefore limiting systemic Recently, synthetic dyes, particular Congo red (CR),...

The reactions of methane and hydrofluoromethanes (CH4-nFn, n = 0, 1, 2, or 3) with a hydroxyl radical have been investigated by modified GAUSSIAN-2 (G2M) method. Reaction enthalpies compared to those obtained original G2 G2MP2 schemes. average absolute error for the reaction calculated G2M method was smaller than were chemical accuracy. Moreover, selected MP2 schemes (those smallest errors in calculations enthalpies) used compute classical barrier heights. According transition state theory,...

Abstract Elongation and cutoff elongation methods are described at the restricted open‐shell Hartree–Fock (ROHF) level of theory. Test calculations performed for polyethylene radicals CH 3 ‐(CH 2 ) N −1 ( = 8, 10, 12, … 40), using minimal (STO‐3G) valence double‐ζ (6‐31G) basis sets. It is demonstrated that process diminishing variational space in method does not introduce a large error, error can be controlled by size starting radical. Implementation technique to leads distinct time savings...

Current state of development the elongation method originally proposed by Imamura is presented. Recent progress in methodology, including geometry optimization and employment fast multiple method, highlighted. The accuracy efficiency as compared to exact canonical Hartree-Fock Kohn-Sham approaches are discussed. Potential applications illustrated wide range calculations for model systems. demonstrated be much more efficient conventional ones with high maintained. CPU time shown linear or...

Meloxicam, a nonsteroidal anti-inflammatory drug (NSAID), is known as selective cyclooxygenase-2 inhibitor. Cyclooxygenase-2 membrane protein, functionally coupled to an interfacial enzyme, phospholipase A2. Consequently, it may be supposed that the interactions of NSAIDs with lipid membranes play role in process. In order investigate mechanism this process, Langmuir films formed 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dilauroyl-sn-glycero-3-phosphocholine,...

Abstract The group electronegativities ( GE ) of molecular fragments, including the environmental contributions due to both electrostatic interactions and electron distribution relaxation, Fukui function FF indices charge sensitivity analysis CSA are correlated with known substituent effects in systems. semiempirical atoms‐in‐molecules AIM resolution has been applied substituted benzenes square platinum complexes treated as illustrative examples. calculated shown constitute adequate...

A linear-scaling implementation of the elongation cutoff technique (ELG/C) that speeds up Hartree-Fock (HF) self-consistent field calculations is presented. The method avoids known bottleneck conventional HF scheme, is, diagonalization, because it operates within low dimension subspace whole atomic orbital space. efficiency ELG/C illustrated for two model systems. obtained results indicate a very efficient sparse matrix algebra scheme.

The two new p-tert-butylcalix[4]arene derivatives described here bear one or nalidixic acid arms linked to the lower calixarene rim via quinolone carboxylate moiety. These were synthesized in order investigate important features of molecules conceived as potential antibiotics, namely, metal cation complexation and interfacial properties, way which they interrelate. properties studied monomolecular films spread on pure water aqueous subphases containing biologically relevant mono- divalent...

Behavior of cationic tetra-p-guanidinoethylcalix[4]arene (CX1) and its building block, p-guanidinoethylphenol (mCX1) in model monolayer lipid membranes was investigated using all atom molecular dynamics simulations surface pressure measurements. Members two classes lipids were taken into account: zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) anionic 1,2-dimyristoyl-sn-glycero-3-phospho-l-serine sodium salt (DMPS) as models eukaryotic bacterial cell membranes, respectively....

Abstract By reducing the surface tension of air–water interface in alveoli, lung surfactant (LS) is crucial for proper functioning lungs. It also forms first barrier against inhaled pathogens. In this study we inspect interactions LS models with a dangerous air pollutant, benzo[a]pyrene (BaP). Dipalmitoylphosphatidylcholine (DPPC), 1‐palmitoyl‐2‐oleoylphosphatidylcholine, and their 1:1 mixture are used as models. Pressure‐area isotherms employed to macroscopic properties monolayers. We find...