Gloria Castellano

Sesquiterpene lactones from Artemisia herba-alba.

Abstract The aerial parts of Artemisia herba-alba subsp. valentine yielded, in addition to known compounds, a new germacranolide, six new eudesmanolides and ilicic acid methyl ester.

Quantitative Structure-Antioxidant Activity Models of Isoflavonoids: A Theoretical Study

Seventeen isoflavonoids from isoflavone, isoflavanone and isoflavan classes are selected from Dalbergia parviflora. The ChEMBL database is representative from these molecules, most of which result highly drug-like. Binary rules appear risky for the selection of compounds with high antioxidant capacity in complementary xanthine/xanthine oxidase, ORAC, and DPPH model assays. Isoflavonoid structure-activity analysis shows the most important properties (log P, log D, pKa, QED, PSA, NH + OH ≈ HBD, N + O ≈ HBA). Some descriptors (PSA, HBD) are detected as more important than others (size measure Mw, HBA). Linear and nonlinear models of antioxidant potency are obtained. Weak nonlinear relationships appear between log P, etc. and antioxidant activity. The different capacity trends for the three complementary assays are explained. Isoflavonoids potency depends on the chemical form that determines their solubility. Results from isoflavonoids analysis will be useful for activity prediction of new sets of flavones and to design drugs with antioxidant capacity, which will prove beneficial for health with implications for antiageing therapy.

Resonance in Interacting Induced-Dipole Polarizing Force Fields: Application to Force-Field Derivatives

The Silberstein model of the molecular polarizability of diatomic molecules, generalized by Applequist et al. for polyatomic molecules, is analyzed. The atoms are regarded as isotropically polarizable points located at their nuclei, interacting via the fields of their induced dipoles. The use of additive values for atom polarizabilities gives poor results, in some cases leading to artificial predictions of absorption bands. The molecular polarizability of methane and its derivative are computed. The agreement with experimental mean molecular polarizabilities is within 1–5%. A hypothesis is indispensable for a suitable representation of polarizability derivative.

Elementary Polarizability of Sc/Fullerene/Graphene Aggregates and Di/Graphene–Cation Interactions

Elementary Polarizability of Sc/Fullerene/Graphene Aggregates and Di/Graphene–Cation Interactions nInteracting induced-dipoles polarization in code POLAR allows molecular polarizability, which is tested with Scn/Cn [fullerene/ graphene (GR)]/Scn@Cm clusters. Polarizability sees clusters of unlike sizes, parting isomers. Bulk limit is estimated from Clausius– Mossotti relation. Clusters are more polarizable than the bulk. Theory yielded this for small Sin/Gen/GanAsm; however, experiment, reversely for larger Sin/GanAsm/GenTem. Smaller clusters need not act like middle: surface dangling bonds cause small-clusters polarizability that resembles metallic. Code AMYR models GR(2)– Mz+. A 24-atom plane models GR. Mz+ is placed on GR top (T)/ bridge (B)/hollow (H). GR–Mz+ stability decays: H>E>T. From H to T, stability drops 75%, 16%, 14%, 35%, 19% and 31% for Li+/Na+/ K+/M+ mean/Ca2+/average. In GR2–Mz+ from H to B to T, stability decays 4%/1%. Drops are smaller than GR–Mz+. Dispersion differs less than GR–Mz+. GR is more aware than GR2 to Mz+, M+/2+ swap and site.

Molecular Classification of Pesticides Including Persistent Organic Pollutants, Phenylurea and Sulphonylurea Herbicides

Pesticide residues in wine were analyzed by liquid chromatography–tandem mass spectrometry. Retentions are modelled by structure–property relationships. Bioplastic evolution is an evolutionary perspective conjugating effect of acquired characters and evolutionary indeterminacy–morphological determination–natural selection principles; its application to design co-ordination index barely improves correlations. Fractal dimensions and partition coefficient differentiate pesticides. Classification algorithms are based on information entropy and its production. Pesticides allow a structural classification by nonplanarity, and number of O, S, N and Cl atoms and cycles; different behaviours depend on number of cycles. The novelty of the approach is that the structural parameters are related to retentions. Classification algorithms are based on information entropy. When applying procedures to moderate-sized sets, excessive results appear compatible with data suffering a combinatorial explosion. However, equipartition conjecture selects criterion resulting from classification between hierarchical trees. Information entropy permits classifying compounds agreeing with principal component analyses. Periodic classification shows that pesticides in the same group present similar properties; those also in equal period, maximum resemblance. The advantage of the classification is to predict the retentions for molecules not included in the categorization. Classification extends to phenyl/sulphonylureas and the application will be to predict their retentions.

Protein negative/positively cooperative binding to zwitterionic/anionic vesicles.

The role of electrostatics is studied in the adsorption of cationic proteins to zwitterionic phosphatidylcholine (PC) and anionic mixed PC/phosphatidylglycerol (PG) small unilamellar vesicles (SUVs) [1]. For model proteins the interaction is monitored vs. PG content at low ionic strength [2]. The adsorption of lysozyme-myoglobin-bovine serum albumin (BSA) (isoelectric point, pI 5-11) is investigated in SUVs, along with changes of the fluorescence emission spectra of the proteins, via their adsorption on SUVs [3]. In the Gouy-Chapman formalism the activity coefficient goes with the square of charge number [4]. Deviations from the ideal model indicate asymmetric location of anionic phospholipid in the bilayer inner leaflet, in mixed zwitterionic/anionic SUVs for protein-PC/PG, in agreement with experiments-molecular dynamics simulations. Effective SUV charge stays constant. Myoglobin-, DNC-melittin- and melittin-zwitterionic associations are described by a partition model, modulated by electrostatic charging of membrane as protein accumulates at interface. Provisional conclusions follow. (1) In mixed zwitterionic/anionic vesicles the charge effect on the protein binding model was analyzed. For lysozyme-anionic enough vesicles and myoglobin the electrostatic repulsion between cationic ad proteins dominates over the electrostatic attraction between ad protein dipoles. (2) The salt effect on the protein binding model of mixed zwitterionic/anionic vesicles was analyzed. The cooperativity increases with ionic strength. The corresponding interpretation is that the electrostatic repulsion between cationic ad proteins decreases with increasing salt effect, and the electrostatic attraction between ad protein dipoles becomes dominant over the electrostatic repulsion between ad protein charges. (3) In anionic vesicles the effect of vesicle charge on protein binding shows that, with increasing anionic character of the vesicles, the protein-protein electrostatic repulsion is decreasingly important vs. the protein-vesicle attraction, and the electrostatic attraction between ad protein dipoles becomes dominant over the electrostatic repulsion between ad protein charges. (4) For lysozyme-mixed zwitterionic/anionic vesicles and myoglobin cooperativity increases with pH. With increasing pH and decreasing cationic character of the protein, the protein-protein electrostatic repulsion is decreasingly important against the protein-SUV attraction, and the electrostatic attraction between ad protein dipoles becomes dominant over the electrostatic repulsion between ad protein charges. Furthermore the opposed effect is observed for lysozyme-zwitterionic vesicles. (5) For protein-mixed zwitterionic/anionic vesicle binding there is more dispersion in the results, which could indicate asymmetric location of anionic phospholipid.