Enzymatic-assisted polymerization of the lignin obtained from a macroalgae consortium, using an extracellular laccase-like enzyme (Tg-laccase) from Tetraselmis gracilis.

In the past decade, Mexican coasts have received an enormous influx of macroalgae species, producing serious environmental and public health concerns. Here, we developed a green methodology to generate a new polymer from the lignin contained in the macroalgae. The methodology consists in lignin extraction-by-boiling and its subsequent polymerization with a laccase-like enzyme from the green algae Tetraselmis gracilis (Tg-laccase). Mass spectrometry revealed the presence of guaiacyl (G), p-hydroxyphenyl (H), and sinapyl alcohol as the main monolignols in the lignin from Sargassum sp. On the other hand, MALDI-TOF spectra shows an increase in the size of the lignin chain after enzymatic polymerization process with Tg-laccase. Besides, the characterization of the novel polymer -using 1H NMR, FTIR, SEC-FPLC, and UV/Vis- allowed establishing that during the polymerization process there is a decrease in the number of phenolic groups as well as loss of aromatic protons, which allowed proposing a polimerizacion mechanism. This methodology could be promising in the development of a new lignin-based polymer and would open a new direction for the environmental management of the macroalgae on the Mexican beaches.

The Peptide AmPep1 Derived from Amaranth Recognizes the Replication Hairpin of TYLCV Disturbing Its Replication Process in Host Plants.

Antiviral compounds targeting viral replicative processes have been studied as an alternative for the control of begomoviruses. Previously, we have reported that the peptide AmPep1 has strong affinity binding to the replication origin sequence of tomato yellow leaf curl virus (TYLCV). In this study, we describe the mechanism of action of this peptide as a novel alternative for control of plant-infecting DNA viruses. When AmPep1 was applied exogenously to tomato and Nicotiana benthamiana plants infected with TYLCV, a decrease in the synthesis of the two viral DNA strands (CS and VS) was observed, with a consequent delay in the development of disease progress in treated plants. The chemical mechanism of action of AmPep1 was deduced using Raman spectroscopy and molecular modeling showing the formation of chemical interactions such as H bonds and electrostatic interactions and the formation of π-π interactions between both biomolecules contributing to tampering with the viral replication.

Full Structural Characterization of Homoleptic Complexes of Diacetylcurcumin with Mg, Zn, Cu, and Mn: Cisplatin-level Cytotoxicity in Vitro with Minimal Acute Toxicity in Vivo.

At the present time, scientists place a great deal of effort worldwide trying to improve the therapeutic potential of metal complexes of curcumin and curcuminoids. Herein, the synthesis of four homoleptic metal complexes with diacetylcurcumin (DAC), using a ligand designed to prevent the interaction of phenolic groups, rendering metal complexes through the ß-diketone functionality, is reported. Due to their physiological relevance, we used bivalent magnesium, zinc, copper, and manganese for complexation with DAC. The resulting products were characterized by ultraviolet-visible (UV-Vis), fluorescence spectroscopy, infrared spectroscopy (IR), liquid and solid-state nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), magnetic moment, mass spectrometry (MS), single crystal, and powder X-ray diffraction (SCXRD and PXRD). Crystallization was achieved in dimethylsulfoxide (DMSO) or N,N-dimethylformamide (DMF) as triclinic systems with space group P-1, showing the metal bound to the ß-diketone function, while the 1H-NMR confirmed the preference of the enolic form of the ligand. Single crystal data demonstrated a 1:2 metal:ligand ratio. The inhibition of lipid peroxidation was evaluated using the thiobarbituric acid reactive substance assay (TBARS). All four metal complexes (Mg, Zn, Cu, and Mn) exhibited good antioxidant effect (IC50 = 2.03 ± 0.27, 1.58 ± 0.07, 1.58 ± 0.15 and 1.24 ± 0.10 µM respectively) compared with butylated hydroxytoluene (BHT) and α-tocopherol. The cytotoxic activity in human cancer cell lines against colon adenocarcinoma (HCT-15), mammary adenocarcinoma (MCF-7), and lung adenocarcinoma (SKLU-1) was found comparable ((DAC)2Mg), or ca. 2-fold higher ((DAC)2Zn) than cisplatin. The acute toxicity assays indicate class 5 toxicity, according to the Organization for Economic Co-operation and Development (OECD) guidelines at doses of 3 g/kg for all complexes. No mortality or changes in the behavior of animals in any of the treated groups was observed. A therapeutic potential can be envisaged from the relevant cytotoxic activity upon human cancer cell lines in vitro and the undetected in vivo acute toxicity of these compounds.

A New Family of Homoleptic Copper Complexes of Curcuminoids: Synthesis, Characterization and Biological Properties.

We report herein the synthesis and crystal structures of five new homoleptic copper complexes of curcuminoids. The scarcity of reports of homoleptic complex structures of curcuminoids is attributed to the lack of crystallinity of such derivatives, and therefore, their characterization by single crystal X-ray diffraction is rare. The ligand design suppressing the phenolic interaction by esterification or etherification has afforded a significant increase in the number of known crystal structures of homoleptic metal complexes of curcuminoids revealing more favorable crystallinity. The crystal structures of the present new copper complexes show four-fold coordination with a square planar geometry. Two polymorphs were found for DiBncOC-Cu when crystallized from DMF. The characterization of these new complexes was carried out using infrared radiation (IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and single crystal X-ray diffraction (SCXRD) and the antioxidant and cytotoxic activity of the obtained complexes was evaluated.

Resistance-modifying Activity in Vinblastine-resistant Human Breast Cancer Cells by Oligosaccharides Obtained from Mucilage of Chia Seeds (Salvia hispanica).

The multidrug resistance (MDR) phenotype is considered as a major cause of the failure in cancer chemotherapy. The acquisition of MDR is usually mediated by the overexpression of drug efflux pumps of a P-glycoprotein. The development of compounds that mitigate the MDR phenotype by modulating the activity of these transport proteins is an important yet elusive target. Here, we screened the saponification and enzymatic degradation products from Salvia hispanica seed's mucilage to discover modulating compounds of the acquired resistance to chemotherapeutic in breast cancer cells. Preparative-scale recycling HPLC was used to purify the hydrolysis degradation products. All compounds were tested in eight different cancer cell lines and Vero cells. All compounds were noncytotoxic at the concentration tested against the drug-sensitive and multidrug-resistant cells (IC50  > 29.2 µM). For the all products, a moderate vinblastine-enhancing activity from 4.55-fold to 6.82-fold was observed. That could be significant from a therapeutic perspective. Copyright © 2017 John Wiley & Sons, Ltd.

Retro-Curcuminoids as Mimics of Dehydrozingerone and Curcumin: Synthesis, NMR, X-ray, and Cytotoxic Activity.

Curcumin and its derivatives have been extensively studied for their remarkable medicinal properties, and their chemical synthesis has been an important step in the optimization of well-controlled laboratory production. A family of new compounds that mimic the structure of curcumin and curcuminoids, here named retro-curcuminoids (7-14), was synthesized and characterized using 1D ¹H- and 13C-NMR, IR, and mass spectrometry; the X-ray structure of 7, 8, 9, 10, 12, 13, and 14 are reported here for the first time. The main structural feature of these compounds is the reverse linkage of the two aromatic moieties, where the acid chloride moiety is linked to the phenolic group while preserving α, ß-unsaturated ketone functionality. The cytotoxic screening of 7, 8, 9, and 10 at 50 and 10 µg/mL was carried out with human cancer cell lines K562, MCF-7, and SKLU-1. Lipid peroxidation on rat brain was also tested for compounds 7 and 10. Compounds 7, 8, and 10 showed relevant cytotoxic activity against these cancer cell lines, and 10 showed a protective effect against lipid peroxidation. The molecular resemblance to curcuminoids and analogs with ortho substituents suggests a potential source of useful bioactive compounds.

Structural analysis as an alternative to identify and determine mode of action of antimicrobial peptides: proposition of a kinetic model based on molecular dynamics studies.

Antimicrobial peptides (AMPs) constitute an important alternative in the search for new treatments against pathogens. We analyzed the sequence variability in cytokine and chemokine proteins to investigate whether these molecules contain a sequence useful in the development of new AMPs. Cluster analysis allowed the identification of tracts, grouped in five categories showing structure and sequence homology. The structure and function relationship among these groups, was analyzed using physicochemical parameters such as length, sequence, charge, hydrophobicity and helicity, which allowed the selection of a candidate that could constitute an AMP. This peptide comprises the C-terminal alpha-helix of chemokines CXCL4/PF-457-70. Far-UV CD spectroscopy showed that this molecule adopts a random conformation in aqueous solution and the addition of 2, 2, 2 trifluoroethanol (TFE) is required to induce a helical secondary structure. The CXCL4/PF-457-70 peptide was found to have antimicrobial activity and very limited hemolytic activity. The mechanism of action was analyzed using model kinetics and molecular dynamics. The kinetic model led to a reasonable assumption about a rate constant and regulatory step on its mechanism of action. Using molecular dynamics simulations, the structural properties the CXCL4/PF-457-70 have been examined in a membrane environment. Our results show that this peptide has a strong preference for binding to the lipid head groups, consequently, increasing the surface density and decreasing the lateral mobility of the lipids alters its functionality.

Experimental and computational studies on the inhibition of acetylcholinesterase by curcumin and some of its derivatives.

Recent studies have demonstrated several biological activities of curcumin with therapeutic potential against Alzheimer's disease, among them the inhibition of the enzyme acetylcholinesterase (AChE). Aiming at identifying the chemical features relevant for this activity, the inhibition of curcumin and a set of 7 derivatives against AChE of E. electricus was measured. These derivatives presented lower activity than curcumin, allowing for the identification of possible unfavorable enzyme-inhibitor interactions. Our computational approach was to dock the molecules to the active site of AChE, followed by an analysis of hydrogen bonds and close contacts to relevant aromatic amino acid residues. To account for inhibitory activity, we sought to define the common structural features between known acetylcholinesterase inhibitors and the tested derivatives. A pharmacophore model was generated, which consisted of two hydrophobic, one aromatic and one hydrogen bond acceptor features. We conclude that the presence of two aromatic rings and the distance between them, allows curcumin and its derivatives to favorably interact with both the quaternary and peripheral sites of AChE. Hydrogen bonds can be formed with the quaternary and acyl sites, which should further stabilize the complex. The acylation of the hydroxyl groups and the reduction of the conjugated double bonds lowered the inhibitory activity, pointing to the modification of the keto-enol moiety as the best alternative for the design of more potent curcumin derivatives as acetylcholinesterase inhibitors.

Structural determinants of gating in the TRPV1 channel.

Transient receptor potential vanilloid 1 (TRPV1) channels mediate several types of physiological responses. Despite the importance of these channels in pain detection and inflammation, little is known about how their structural components convert different types of stimuli into channel activity. To localize the activation gate of these channels, we inserted cysteines along the S6 segment of mutant TRPV1 channels and assessed their accessibility to thiol-modifying agents. We show that access to the pore of TRPV1 is gated by S6 in response to both capsaicin binding and increases in temperature, that the pore-forming S6 segments are helical structures and that two constrictions are present in the pore: one that impedes the access of large molecules and the other that hampers the access of smaller ions and constitutes an activation gate of these channels.

catena-Poly[[[aqua[3-(2-pyridylsulfanyl)propionato N-oxide-kappaO1]copper(II)]-mu-[3-(2-pyridylsulfanyl)propionato N-oxide-kappa3O3:O1,O1'] dihydrate].

In the title complex, {[Cu(C8H8NO3S)2(H2O)] x 2 H2O}n, the Cu(II) cation has a distorted square-pyramidal coordination environment consisting of five O atoms, one from a water molecule, one from an N-O group and the other three from the carboxylate groups of two 3-(2-pyridylsulfanyl)propionate N-oxide anions. The aqua[3-(2-pyridylsulfanyl)propionato N-oxide]copper(II) moieties are bridged by 3-(2-pyridylsulfanyl)propionate N-oxide anions to form an infinite three-dimensional coordination polymer with a zigzag chain structure. The crystal structure is stabilized by hydrogen bonds.

Characterization of the gating brake in the I-II loop of Ca(v)3.2 T-type Ca(2+) channels.

Mutations in the I-II loop of Ca(v)3.2 channels were discovered in patients with childhood absence epilepsy. All of these mutations increased the surface expression of the channel, whereas some mutations, and in particular C456S, altered the biophysical properties of channels. Deletions around C456S were found to produce channels that opened at even more negative potentials than control, suggesting the presence of a gating brake that normally prevents channel opening. The goal of the present study was to identify the minimal sequence of this brake and to provide insights into its structure. A peptide fragment of the I-II loop was purified from bacteria, and its structure was analyzed by circular dichroism. These results indicated that the peptide had a high alpha-helical content, as predicted from secondary structure algorithms. Based on homology modeling, we hypothesized that the proximal region of the I-II loop may form a helix-loop-helix structure. This model was tested by mutagenesis followed by electrophysiological measurement of channel gating. Mutations that disrupted the helices, or the loop region, had profound effects on channel gating, shifting both steady state activation and inactivation curves, as well as accelerating channel kinetics. Mutations designed to preserve the helical structure had more modest effects. Taken together, these studies showed that any mutations in the brake, including C456S, disrupted the structural integrity of the brake and its function to maintain these low voltage-activated channels closed at resting membrane potentials.

Synthesis and anti-inflammatory activity evaluation of unsymmetrical selenides.

The alkylation reaction of 2,2'-diseleno and 4,4'-diseleno-bis(benzoic acid) derivatives in the presence of sodium borohydride and alkyl halides allowed the synthesis of various new o- and p-alkylselenenylated benzoic acid derivatives in good yields. The anti-inflammatory activity of selected selenide derivatives on granuloma induced by subcutaneous implantation of cotton pellets in Wistar rats was examined. Selenium derivatives 2a, 2c and 2e showed anti-inflammatory activity although to a lesser extent as compared to indomethacin, however they were found less toxic than the latter.

Isolation and biochemical characterization of an antifungal peptide from Amaranthus hypochondriacus seeds.

An antifungal peptide, Ay-AMP, was isolated from Amaranthus hypochondriacus seeds by acidic extraction and then purified by reverse-phase high-pressure liquid chromatography. The molecular mass of this peptide, as determined by mass spectrometry, is 3184 Da. The peptide belongs to the superfamily of chitin-binding proteins, containing a single cysteine/glycine-rich chitin-binding domain, and it was found that Ay-AMP degrades chitin. Ay-AMP inhibits the growth, at very low doses, of different pathogenic fungi, such as Candida albicans, Trichoderma sp., Fusarium solani, Penicillium chrysogenum, Geotrichum candidum, Aspergillus candidus, Aspergillus schraceus, and Alternaria alternata. Ay-AMP is very resistant to the effect of proteases and heating; however, it showed an antagonistic effect with CaCl2 and KCl.

Crystal structure of 6-benzylamino-9-[2-tetrahydropyranyl]-9H-purine.

C17H19O2N5 is monoclinic, P2(1)/n. Unit-cell dimensions at 293 K are a = 10.802(1), b = 24.085(2), c = 12.933(1)A, beta = 106.119(6) degrees, V = 3232.4(6)A3, Dx = 1.271 g/cm3, and Z = 8. The R value is 0.068 for 3017 observed reflections. There are two independent molecules in the asymmetric unit, denoted by A and B. In A, the dihedral angle between the adenine moiety and the phenyl ring is 73.2(3)degrees [in B, the angle is 83.9(2)degrees]. For A, the tetrahydropyranyl ring adopts a half-chair conformation [for B, chair conformation]. The packing in the crystal is entirely due to van der Waals forces.

Crystal structure of 2-selenobenzyl-1-benzoic acid.

C14H12O2Se is monoclinic, P2(1)/c. Unit-cell dimensions at 293 K are a = 8.1055(7), b = 5.8403(11), c = 26.0302(17)A, beta = 94.560(5) degrees, V = 1228.3(3)A3, Dx = 1.575 g/cm3, and Z = 4. The R value is 0.048 for 2144 observed reflections. The dihedral angle between the phenyl rings is 74.9(2)degrees. There is an intermolecular hydrogen bond between two symmetry related carboxyl groups with an O1-O2 distance of 2.668(6)A. The molecules in the crystal are packed at normal van der Waals distances.

Crystal structure of 2-Se-(2-methyl-2-propenyl)-1-benzoic acid.

C11H12O2Se is triclinic, P1. Unit-cell dimensions at 293 K are a = 5.8450(10), b = 8.1490(10), c = 11.4620(10)A, alpha = 97.050(10), beta = 90.140(10), gamma = 90.120(10) degrees, V = 541.81(12)A3, Dx = 1.564 g/cm3, and Z = 2. The R value is 0.047 for 1388 observed reflections. The dihedral angle between the phenyl ring and the isobutenyl group is 72.3(2) degrees. There is an intermolecular hydrogen bond between two symmetry-related carbonyl groups with an O1...O2 distance of 2.669(6)A. The molecules in the crystal are packed at normal van der Waals distances.

Crystal structures of N,N'-(m-tolyl)thiourea and N,N'-(p-tolyl)thiourea.

C15H16N2S is monoclinic [orthorhombic], P2(1)/c [Pbcn]. Unit-cell dimensions at 293 K are a = 9.506(1), b = 7.629(1), c = 20.077(1)A, beta = 99.93(1) degrees, V= 1434.2(2)A(3), D(x) = 1.187 g/cm3, and Z = 4 [a = 11.806(2), b = 13.954(2), c = 8.466(1)A, V = 1394.7(3)A(3), D(x) = 1.221 g/cm3, and Z = 8]. The R value is 0.049 [0.045] for 1620 [1229] observed reflections. The dihedral angle between the tolyl rings is 53.6(1) degrees [47.9(1)degrees]. The crystal structures are stabilized by N-H...S hydrogen bonds and van der Waals forces.

Crystal structure of dibenzoyl diselenide.

C14H10O2Se2 is monoclinic, P2(1)/c. The unit-cell dimensions at 293 K are a = 12.795(2), b = 12.126(2), c = 9.0179(13)A, beta = 107.074(6)degrees, V = 1337.5(3)A3, and Z = 4. The R value is 0.048 for 2319 observed reflections. The dihedral angle between the plane C4-C7(O2)-Se1 and C9-C8(O1)-Se2 is 85.6(2)degrees, keeping the Se atom unshared electron pairs in a more stable configuration with the rest of the molecule. The packing in the crystal is entirely due to van der Waals forces.

Amino acid sequence, biochemical characterization, and comparative modeling of a nonspecific lipid transfer protein from Amaranthus hypochondriacus.

Plant nonspecific lipid transfer proteins (nsLTPs) are characterized by their ability to bind a broad range of hydrophobic ligands in vitro. Their biological function has not yet been elucidated, but they could play a major role in plant defense to physical and biological stress. An nsLTP was isolated from Amaranthus hypochondriacus seeds and purified by gel filtration and reversed-phase high-performance liquid chromatography techniques. The molecular mass of the protein as determined by mass spectrometry is 9747.29 Da. Data from amino acid sequence, circular dichroism and binding/displacement of a fluorescent lipid revealed that it belongs to the nsLTP1 family. The protein shows the alpha-helical secondary structure typical for plant nsLTPs 1 and shares 40 to 57% sequence identity with nsLTPs 1 from other plant species and 100% identity with an nsLTP1 from Amaranthus caudatus. A model structure of the protein in complex with stearate based on known structures of maize and rice nsLTPs 1 suggests a protein fold complexed with lipids closely related to that of maize nsLTP1.

Crystal structure of 1beta-hydroxy-beta-homopipitzolone (9-hydroxy-2,6,9-trimethyltricyclo[6,3,1,0(1,6)]dodeca-5,10,11,12-tetraone).

C15H18O5 is orthorhombic, P2(1)2(1)2(1). The unit-cell dimensions at 293 K are a = 6.526(3), b = 10.247(4), c = 21.008(13) A, V = 1404.8(12) A3, Dx = 1.316 g/cm3, and Z = 4. The R value is 0.044 for 1288 observed reflections. The A, B and C rings adopt chair, twist, and half-chair conformations. The absolute configuration is inferred from the C6 stereochemistry of (+)-cedrol. The crystal structure is stabilized by an O-H...O hydrogen bond and van der Waals forces.