Influences of Recycled Polyethylene Terephthalate Microplastic on the Hygrothermal and Mechanical Performance of Plasterboard with Polymethylhydrosiloxane Content

New composites produced with recycled waste are needed to manufacture more sustainable construction materials. This paper aimed to analyze the hygrothermal and mechanical performance of plasterboard with a polymethylhydrosiloxane (PMHS) content, incorporating recycled PET microplastic waste and varying factors such as PMHS dose, homogenization time, and drying temperature after setting. A cube-centered experimental design matrix was performed. The crystal morphology, porosity, fluidity, water absorption, flexural strength, and thermal conductivity of plasterboards were measured. The results showed that incorporating recycled PET microplastics does not produce a significant difference in the absorption and flexural strength of plasterboards. However, the addition of recycled PET reduced the thermal conductivity of plasterboards by around 10%.

Ionenes as Potential Phase Change Materials with Self-Healing Behavior

Ionenes are poly(ionic liquids) (PILs) comprising a polymer backbone with ionic groups along the structure. Ionenes as solid-solid phase change materials are a recent research field, and some studies have demonstrated their potential in thermal dissipation into electronic devices. Eight ionenes obtained through Menshutkin reactions were synthesized and characterized. The analysis of the thermal tests allowed understanding of how the thermal properties of the polymers depend on the aliphatic nature of the dihalogenated monomer and the carbon chain length. The TGA studies concluded that the ionenes were thermally stable with T10% above 420 °C. The DSC tests showed that the prepared ionenes presented solid-solid transitions, and no melting temperature was appreciated, which rules out the possibility of solid-liquid transitions. All ionenes were soluble in common polar aprotic solvents. The hydrophilicity of the synthesized ionenes was studied by the contact angle method, and their total surface energy was calculated. Self-healing behavior was preliminarily explored using a selected sample. Our studies show that the prepared ionenes exhibit properties that make them potential candidates for applications as solid-solid phase change materials.

Improvement of Plasterboard Properties by the Control of Polymethylhydrosiloxane Dosage, Stirring Time, and Drying Temperature Applied to the Calcium Sulfate Hemihydrate and Water Mixture

Plasterboard is an important building material in the construction industry because it allows for quick installation of walls, partitions, and ceilings. Although a common material, knowledge about its performance related to modern polymers and fabrication conditions is still lacking. The present work analyzes how some manufacturing factors applied during the plaster board fabrication impact on some plasterboard properties, including water absorption, flexural strength, and thermal conductivity. The manufacturing variables evaluated are the dose (D) of polymethylhydrosiloxane (PMHS), the agitation time of the mixture (H), and the drying temperature of the plaster boards after setting (T). The results suggest that factors D, H, and T induce changes in the porosity and the morphological structure of the calcium sulfate dihydrate crystals formed. Performance is evaluated at two levels of each factor following a statistical method of factorial experimental design centered on a cube. Morphological changes in the crystals of the resulting boards were evaluated with scanning electron microscopy (SEM) and the IMAGEJ image analysis program. Porosity changes were evaluated with X-ray microcomputed tomography (XMT) and 3D image analysis tools. The length-to-width ratio of the crystals decreases as it goes from low PMHS dosage to high dosage, favoring a better compaction of the plasterboard under the right stirring time and drying temperature. In contrast, the porosity generated by the incorporation of PMHS increases when going from low-level to high-level conditions and affects the maximum size of the pores being generated, with a maximum value achieved at 0.6% dosage, 40 s, and 140 °C conditions. The presence of an optimal PMHS dosage value that is approximately 0.6-1.0% is evidenced. In fact, when comparing trails without and with PMHS addition, a 10% decrease in thermal conductivity is achieved at high H (60 s) and high T (150 °C) level conditions. Water absorption decreases by more than 90% when PMHS is added, mainly due to the hydrophobic action of the PMHS. Minimum water absorption levels can be obtained at high drying temperatures. Finally, the resistance to flexion is not affected by the addition of PMHS because apparently there are two opposing forces acting: on one hand is the decrease in the length-width ratio giving more compactness, and on the other hand is the generation of pores. The maximum resistance to flexion was found around a dosage of 0.6% PMHS. In conclusion, the results suggest that the addition of PMHS, the correct agitation time of the mixture, and the drying temperature reduce the water absorption and the thermal conductivity of the gypsum boards, with no significant changes in the flexural resistance.

Development of Novel Phase-Change Materials Derived from Methoxy Polyethylene Glycol and Aromatic Acyl Chlorides

In this research, novel, organic, solid-liquid phase-change materials (PCMs) derived from methoxy polyethylene glycol (MPEG) and aromatic acyl chlorides (ACs) were prepared through a condensation reaction. The MPEGs were used as phase-change functional chains with different molecular weights (350, 550, 750, 2000, and 5000 g/mol). The aromatic ACs, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC), were employed as bulky linker cores. Solubility tests demonstrated that this family of PCMs is soluble in protic polar solvents such as H₂O and MeOH, and insoluble in nonpolar solvents such as n-hexane. Fourier-ransform infrared spectroscopy (FT-IR UATR) and nuclear magnetic resonance (¹H, ¹³C, DEPT 135°, COSY, HMQC, and HMBC NMR) were used to confirm the bonding of MPEG chains to ACs. The crystalline morphology of the synthesized materials was examined using polarized optical microscopy (POM), revealing the formation of spherulites with Maltese-cross-extinction patterns. Furthermore, it was confirmed that PCMs with higher molecular weights were crystalline at room temperature and exhibited an increased average spherulite size compared to their precursors. Thermal stability tests conducted through thermogravimetric analysis (TGA) indicated decomposition temperatures close to 400 °C for all PCMs. The phase-change properties were characterized by differential scanning calorimetry (DSC), revealing that the novel PCMs melted and crystallized between -23.7 and 60.2 °C and -39.9 and 45.9 °C, respectively. Moreover, the heat absorbed and released by the PCMs ranged from 57.9 to 198.8 J/g and 48.6 to 195.6 J/g, respectively. Additionally, the PCMs exhibited thermal stability after undergoing thermal cycles of melting-crystallization, indicating that energy absorption and release occurred at nearly constant temperatures. This study presents a new family of high-performance organic PCMs and demonstrates that the orientation of substituent groups in the phenylene ring influences supercooling, transition temperatures, and thermal energy storage capacity depending on the MPEG molecular weight.

New Benzotriazole and Benzodithiophene-Based Conjugated Terpolymer Bearing a Fluorescein Derivative as Side-Group: In-Ternal Förster Resonance Energy Transfer to Improve Organic Solar Cells

A new benzodithiophene and benzotriazole-based terpolymer bearing a fluorescein derivative as a side group was synthesized and studied for organic solar cell (OSC) applications. This side group was covalently bounded to the backbone through an n-hexyl chain to induce the intramolecular Förster Resonance Energy Transfer (FRET) process and thus improve the photovoltaic performance of the polymeric material. The polymer exhibited good solubility in common organic chlorinated solvents as well as thermal stability (TDT10% > 360 °C). Photophysical measurements demonstrated the occurrence of the FRET phenomenon between the lateral group and the terpolymer. The terpolymer exhibited an absorption band centered at 501 nm, an optical bandgap of 2.02 eV, and HOMO and LUMO energy levels of −5.30 eV and −3.28 eV, respectively. A preliminary study on terpolymer-based OSC devices showed a low power-conversion efficiency (PCE) but a higher performance than devices based on an analogous polymer without the fluorescein derivative. These results mean that the design presented here is a promising strategy to improve the performance of polymers used in OSCs.

Novel Polyelectrolytes Obtained by Direct Alkylation and Ion Replacement of a New Aromatic Polyamide Copolymer Bearing Pyridinyl Pendant Groups

The following work shows, for the first time, the synthesis and characterization of a new family of polyelectrolytes, along with their preliminary assessments in terms of desalin water treatment. These materials fall into the category of aromatic co-polyamides, which are obtained by the direct condensation of monomers 4,4′-oxydianiline (ODA), isophthaloyl chloride, and 3,5-diamino-N-(pyridin-4-ylmethyl)benzamide (PyMDA). Thereby, the charged nature exhibited by these materials was achieved through the quaternization of PyMDA moieties using linear iodoalkanes of different lengths (C_nI with n = 1, 2, 4, and 6). After completing the quaternization process, polyelectrolytes were subjected to a one-step anion substitution process, where iodide counterions were replaced by bis(trifluoromethane)sulfonamide entities. For all the obtained materials, solubility tests were carried out, showing that those alkylated with methyl and ethyl chains exhibit high solubility in rutinary aprotic polar solvents, while those containing n-butyl and n-hexyl units resulted in the formation of insoluble gels. Due to the above, the latest were discarded from this study early on. The structural characterization of the initial neutral co-polyamide was carried out by means of infrared spectroscopy (FT-IR), nuclear magnetic resonance (¹H, ¹³C-NMR), and size-exclusion chromatography (SEC), while the structure of methylated and ethylated polyelectrolytes was successfully confirmed through FT-IR, ¹H, ¹³C, and ¹⁹F-NMR. Additionally, the thermal behavior of these materials was analyzed in terms of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), showing thermal degradation temperatures above 300 °C and glass transition temperatures (Tg) above 200 °C, resulting in polymers with outstanding thermal properties for water treatment applications. On the other hand, through the solvent-casting method, both neutral and charged polymers were found to be easily prepared into films, exhibiting a remarkably flexibility. The mechanical properties of the films were analyzed using the traction test, from which tensile strength values ranging between 83.5 and 87.9 Mpa, along with Young’s modulus values between 2.4 and 2.5 Gpa were obtained. Moreover, through contact angle measurements and absorption analysis by immersion, polyelectrolytes showed important changes in terms of affinity against polar and polar substances (water, n-heptane, and benzene), exhibiting a higher rejection regarding the neutral polymer. Finally, as a preliminary test against the seepage of saline waters, thin polymer films (from 11.4 to 17.1 µm) were deposited on top of commercial filter discs and tested as filters of saline solutions ([NaCl] = 1000 and 2000 ppm). These tests revealed a decrease of the salt concentration in the obtained filtrates, with retention values ranging between 6.2 and 20.3%, depending on the concentration of the former solution and the polymer used.

PVDF Composite Membranes with Hydrophobically-Capped CuONPs for Direct-Contact Membrane Distillation

Water scarcity is an imminent problem that humanity is beginning to attempt to solve. Among the several technologies that have been developed to mitigate water scarcity, membrane distillation is of particular note. In the present work, CuO nanoparticles capped with 1-octanethiol (CuONPs@CH) or 1H,1H,2H,2H-perfluorodecanethiol (CuONPs@CF) are prepared. The nanoparticles are characterized by FT-IR and TGA methods. Two weight losses are observed in both cases, with the decomposition of the organic fragments beginning at 158 °C and 230 °C for CuONPs@CF and CuONPs@CH, respectively. Flat sheet PVDF composite membranes containing nanoparticles are prepared by the casting solution method using nanoparticle concentrations that ranged between 2-20% with a non-woven polyester fabric as support. The obtained membranes showed a thickness of 240 ± 40 μm. According to water contact angle (87° for CuONPs@CH and 95° for CuONPs@CF, both at 10% w.t) and roughness (12 pixel for CuONPs@CH and 14 pixels for CuONPs@CF, both at 10% w.t) determinations, the hydrophobicity of membranes changed due to a decrease in surface energy, while, for naked CuONPs, the roughness factor represents the main role. Membranes prepared with capped nanoparticles showed similar porosity (60-64%). SEM micrographs show asymmetric porous membranes with a 200-nm surface pore diameter. The largest finger-like pores in the membranes prepared with CuONPs, CuONPs@CH and CuONPs@CF had values of 63 ± 10 μm, 32 ± 8 μm, and 45 ± 10 μm, respectively. These membranes were submitted to a direct contact membrane distillation module and flux values of 1.8, 2.7, and 3.9 kg(m2·h)-1 at ΔT = 30 °C were obtained for the CuONPs, CuONPs@CH, and CuONPs@CF, respectively. The membranes showed 100% salt rejection during the testing time (240 min).

New Hybrid Copper Nanoparticles/Conjugated Polyelectrolyte Composite with Antibacterial Activity

In the search for new materials to fight against antibiotic-resistant bacteria, a hybrid composite from metallic copper nanoparticles (CuNPs) and a novel cationic π-conjugated polyelectrolyte (CPE) were designed, synthesized, and characterized. The CuNPs were prepared by chemical reduction in the presence of CPE, which acts as a stabilizing agent. Spectroscopic analysis and electron microscopy showed the distinctive band of the metallic CuNP surface plasmon and their random distribution on the CPE laminar surface, respectively. Theoretical calculations on CuNP/CPE deposits suggest that the interaction between both materials occurs through polyelectrolyte side chains, with a small contribution of its backbone electron density. The CuNP/CPE composite showed antibacterial activity against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative (Escherichia coli and Salmonella enteritidis) bacteria, mainly attributed to the CuNPs’ effect and, to a lesser extent, to the cationic CPE.

Synthesis and Characterization of a 2,3-Dialkoxynaphthalene-Based Conjugated Copolymer via Direct Arylation Polymerization (DAP) for Organic Electronics

Poly[(5,5'-(2,3-bis(2-ethylhexyloxy)naphthalene-1,4-diyl)bis(thiophene-2,2'-diyl))-alt-(2,1,3-benzothiadiazole-4,7-diyl)] (PEHONDTBT) was synthesized for the first time and through direct arylation polymerization (DAP) for use as p-donor material in organic solar cells. Optimized reaction protocol leads to a donor-acceptor conjugated polymer in good yield, with less structural defects than its analog obtained from Suzuki polycondensation, and with similar or even higher molecular weight than other previously reported polymers based on the 2,3-dialkoxynaphthalene monomer. The batch-to-batch repeatability of the optimized DAP conditions for the synthesis of PEHONDTBT was proved, showing the robustness of the synthetic strategy. The structure of PEHONDTBT was corroborated by NMR, exhibiting good solubility in common organic solvents, good film-forming ability, and thermal stability. PEHONDTBT film presented an absorption band centered at 498 nm, a band gap of 2.15 eV, and HOMO and LUMO energy levels of -5.31 eV and -3.17 eV, respectively. Theoretical calculations were performed to understand the regioselectivity in the synthesis of PEHONDTBT and to rationalize its optoelectronic properties. Bilayer heterojunction organic photovoltaic devices with PEHONDTBT as the donor layer were fabricated to test their photovoltaic performance, affording low power-conversion efficiency in the preliminary studies.

New Triphenylamine-Based Oligomeric Schiff Bases Containing Tetraphenylsilane Moieties in the Backbone

Three new triphenylamine-based oligomeric Schiff bases (polySB1, polySB2 and polySB3) containing tetraphenylsilane core (TPS-core) in the main chain were obtained from TPS-core-based diamines and bis(4-formylphenyl)phenylamine by a high-temperature polycondensation reaction. These new oligomers were structurally characterized by FT-IR, NMR and elemental analysis. All polySBs were highly soluble in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene. Samples showed moderate molecular average molecular weight (Mw) and a high thermal stability above 410 °C. Likewise, polySBs showed absorption near 400 nm in the UV-vis range and photoluminescence. The HOMO levels and band-gap values were found in the ranges of -6.06 to -6.18 eV and 2.65⁻2.72 eV, respectively. The lowest band-gap value was observed for polySB2, which could be attributed to a more effective π-conjugation across the main chain. The results suggest that silicon-containing polySBs are promising wide-band-gap semiconductors materials for optoelectronic applications.

In-Situ Preparation of CdTe Quantum Dots Capped with a β-Cyclodextrin-Epichlorohydrin Polymer: Polymer Influence on the Nanocrystal's Optical Properties

β-Cyclodextrin (βCD), the less water soluble of the cyclodextrins, has been used as a capping agent in the preparation of semiconductor nanocrystals or quantum dots (QDs). Nevertheless, no reports have been found in the use of the highly water-soluble polymer of this, prepared by the crosslinking of the βCD units with epichlorohydrin in basic medium (βCDP). This polymer, besides to overcome the low solubility of the βCD, increases the inclusion constant of the guest; two parameters that deserve its use as capping agent, instead of the native cyclodextrin. In the present manuscript, we afforded the in-situ aqueous preparation of cadmium telluride (CdTe) QDs capped with βCDP. The polymer influence on the photoluminescent properties of the nanocrystals was analyzed. The βCDP controls the nanocrystals growth during the Oswald ripening stage. Consequently, the CdTe capped βCDP QDs showed lower Stokes-shift values, higher photoluminescent efficiency, and narrower size distribution than for nanocrystals obtained in the absence of polymer. Transmission electron microscopy (TEM) micrographs and energy dispersive X-ray spectroscopy (EDS) analysis revealed the composition and crystallinity of the CdTe QDs. This βCDP capped CdTe QDs is a potential scaffold for the supramolecular modification of QDs surface.

Preparation of CuONPs@PVDF/Non-Woven Polyester Composite Membrane: Structural Influence of Nanoparticle Addition

Membrane distillation techniques have appeared as promising options for guaranteeing the availability of potable water in times of scarcity of this essential resource. For membrane preparation, polyvinylidene fluoride (PVDF) is preferred due to the easier synthesis procedures, with respect to other fluorine-based polymers. In this work, copper oxide nanoparticles (CuONPs) of different weight percent (wt %) embedded in PVDF membranes supported on non-woven polyester fabric (NWPET) were prepared by the phase inversion method, and characterized by spectroscopy (ATR-FTIR, Raman) and electron microscopy techniques (SEM). The PVDF deposited onto the NWPET was mostly composed of its polar β-phase (F(β) = 53%), which was determined from the ATR-FTIR spectrum. The F(β) value remained constant throughout the whole range of added CuONP concentrations (2–10 wt %), as was determined from the ATR-FTIR spectrum. The absence of signals corresponding to CuONPs in the ATR-FTIR spectra and the appearance of peaks at 297, 360, and 630 cm⁻¹ in the Raman spectra of the membranes suggest that the CuONPs are preferably located in the inner PVDF membrane, but not on its surface. The membrane morphologies were characterized by SEM. From the obtained SEM micrographs, a decrease and increase in the amount of micropores and nanopores, respectively, near the surface and intercalated in the finger-like layer were observed. As a result of the CuONP addition, the nanopores in the sponge-like layer decreased in size. The values of water contact angle (WCA) measurements showed a decreasing trend, from 94° to 80°, upon the addition of CuONPs (2–10 wt %), indicating a diminishment in the hydrophobicity degree of the membranes. Apparently, the increase in the amount of nanopores near the surface decreased the membrane roughness, so it became less hydrophobic.

PANI Branches onto Donor-Acceptor Copolymers: Synthesis, Characterization and Electroluminescent Properties of New 2D-Materials

A new series of two-dimensional statistical conjugated polymers based on aniline and 9,9-dihexylfluorene as donor units and benzo- or naphtho-quinoxaline/thiadiazole derivatives as acceptor moieties, possessing PANI segments as side chains, were designed and synthesized. To investigate the effects of the perpendicular PANI branches on the properties of the main chain, the optical, electrochemical, morphological and electroluminescence properties were studied. The 2D materials tend to possess lower molecular weights and to absorb and to emit light red-shifted compared to the trunk 1D-polymers, in the yellow-red region of the visible spectrum. The 1D- and 2D-conjugated polymers present optical band gaps ranging from 2.15⁻2.55 eV, HOMO energy levels between -5.37 and -5.60 eV and LUMO energy levels between -3.02 and -3.29 eV. OLED devices based on these copolymers were fabricated. Although the performances were far from optimal due to the high turn-on voltages for which electroluminescence phenomena occur, a maximum luminescence of 55,100 cd/m² together with a current density of 65 mA/cm² at 18.5 V were recorded for a 2D-copolymer, PAFC6TBQ-PANI.

Silylated oligomeric poly(ether-azomethine)s from monomers containing biphenyl moieties: synthesis and characterization

In this study, four new silicon-containing poly(ether-azomethine)s with linear structures were prepared using original silicon and biphenyl moiety-containing monomers: two diamines and two dialdehydes. The oligomeric natures of the samples were established by GPC analysis, which showed chains containing 3 to 5 repetitive units. The monomers and the oligomeric samples were structurally characterized by NMR and FT-IR spectroscopy. The solubilities of the samples in common organic solvents and their thermal behavior enable improvement of their industrial and technological processability. The optical band gaps of the oligomeric samples were estimated from optical measurements (UV-vis), and their electrical behavior in films was determined using the four-point method. The surface arrangements and morphological characteristics of the films were determined via atomic force microscopy measurements. The roughness, area increase percentage and layer stiffness of the films were also measured using this technique.

In this study, four new silicon-containing poly(ether-azomethine)s with linear structures were prepared using original silicon and biphenyl moiety-containing monomers: two diamines and two dialdehydes.

Synthesis and characterization of aromatic poly(ether-imide)s based on bis(4-(3,4-dicarboxyphenoxy)phenyl)-R,R-silane anhydrides (R = Me, Ph) – spontaneous formation of surface micropores from THF solutions

Poly(ether-amide)s derived from two new silylated-dianhydrides were prepared and characterized. By FE-SEM and AFM morphological studies were developed.

Silarylene-containing oligo(ether-amide)s based on bis(4-(4-amino phenoxy)phenyl)dimethylsilane. Effect of the dicarboxylic acid structure on some properties

Inherent viscosity and MALDI-TOF analyses suggest the formation of oligomeric chains with sequences A–B, (A–B)₂ and (A–B)₃. The properties and therefore the eventual applications of these materials are modulated by the flexibility and the aromatic content of the chains.

Synthesis and characterization of aromatic poly(amides) based on 3,5-diamino-N-cyclopropylbenzamide

Three aromatic poly(amides) (PAs) were prepared, one of them containing a dimethyldiphenylsilane unit from a new aromatic diamine monomer with a bulky pendant polar group.

Novel aromatic polyimides derived from 2,8-di(3-aminophenyl)dibenzofuran. Synthesis, characterization and evaluation of properties

Three aromatic polyimides (PIs) were prepared from a new aromatic diamine monomer derived from the rigid ring dibenzofuran.

Silicon-containing poly(esters) with halogenated bulky side groups. Synthesis, characterization and thermal studies

Synthesis of poly(esters) X-PE-(a-c) and poly(esters) X-PE.

3D-QSAR modeling of non-peptide antagonists for the human luteinizing hormone-releasing hormone receptor

The application of ligand-based drug design methods such as quantitative structure-activity relationship (QSAR) is a mandatory issue in the design of luteinizing hormone-releasing hormone (LHRH) receptor antagonists because the lack of information on the molecular structure for this target protein. The relationship between the structures and the antagonistic activities of 128 non-peptide antagonists for the LHRH receptor were modeled by using the classic QSAR methods comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). The best model included CoMSIA steric, electrostatic, hydrophobic and hydrogen bond donor fields, had a Q2 value of 0.780 and predicted adequately the activity of external compounds. The tridimensional contour maps generated were used to identify the key structural requirements responsible for a high biological activity of the compounds. These features should represent the ligand features involved in interactions with the target protein that modulate their potency as antagonists.

Silicon-containing oligomeric poly(imido-amides) with amino moieties. Synthesis, characterization and thermal studies

Silicon-containing oligomeric poly(imido-amides) (PIAs) were synthesized from dicarboxylic imido-acids containing a Si atom, which were obtained from dianhydrides, amino acids and p-aminobenzoic acid, were polymerized with the diamine bis(4-aminophenyl)diphenylsilane.

Linear and nonlinear QSAR study of N-hydroxy-2-[(phenylsulfonyl)amino]acetamide derivatives as matrix metalloproteinase inhibitors

The inhibitory activity (IC50) toward matrix metalloproteinases (MMP-1, MMP-2, MMP-3, MMP-9, and MMP-13) of N-hydroxy-2-[(phenylsulfonyl)amino]acetamide derivatives (HPSAAs) has been successfully modeled using 2D autocorrelation descriptors. The relevant molecular descriptors were selected by linear and nonlinear genetic algorithm (GA) feature selection using multiple linear regression (MLR) and Bayesian-regularized neural network (BRANN) approaches, respectively. The quality of the models was evaluated by means of cross-validation experiments and the best results correspond to nonlinear ones (Q2>0.7 for all models). Despite the high correlation between the studied compound IC50 values, the 2D autocorrelation space brings different descriptors for each MMP inhibition. On the basis of these results, these models contain useful molecular information about the ligand specificity for MMP S'1, S1, and S'2 pockets.

Modeling of farnesyltransferase inhibition by some thiol and non-thiol peptidomimetic inhibitors using genetic neural networks and RDF approaches

Inhibition of farnesyltransferase (FT) enzyme by a set of 78 thiol and non-thiol peptidomimetic inhibitors was successfully modeled by a genetic neural network (GNN) approach, using radial distribution function descriptors. A linear model was unable to successfully fit the whole data set; however, the optimum Bayesian regularized neural network model described about 87% inhibitory activity variance with a relevant predictive power measured by q2 values of leave-one-out and leave-group-out cross-validations of about 0.7. According to their activity levels, thiol and non-thiol inhibitors were well-distributed in a topological map, built with the inputs of the optimum non-linear predictor. Furthermore, descriptors in the GNN model suggested the occurrence of a strong dependence of FT inhibition on the molecular shape and size rather than on electronegativity or polarizability characteristics of the studied compounds.

Modeling of Cyclin-Dependent Kinase Inhibition by 1H-Pyrazolo[3,4-d]Pyrimidine Derivatives Using Artificial Neural Network Ensembles

Artificial neural network ensembles were used for modeling the cyclin-dependent kinase inhibition of 1H-pyrazolo[3,4-d]pyrimidine derivatives. The structural characteristics of these inhibitors were encoded in relevant 3D-spatial descriptors extracted by genetic algorithm feature selection. Bayesian-regularized multilayer neural networks, trained by the back-propagation algorithm, were developed using these variables as inputs. The predictive power of the model was tested by leave-one-out cross validation. In addition, for a more rigorous measure of the predictive capacity, multiple validation sets were randomly generated as members of neural network ensembles, which makes doing averaged predictions feasible. In this way, the predictive power was analyzed accounting for the averaged test set R values and test set mean-square errors. Otherwise, Kohonen self-organizing maps were used as an additional tool for the same modeling. The location of the inhibitors in a map facilitates the analysis of the connection between compounds and serves as a useful tool for qualitative predictions.