Modification of carbonic anhydrase II with acetaldehyde, the first metabolite of ethanol, leads to decreased enzyme activity

Background

Bacillus thuringiensis Cry1Aa insecticidal protein is the most active known B. thuringiensis toxin against the forest insect pest Lymantria dispar (gypsy moth), unfortunately it is also highly toxic against the non-target insect Bombyx mori (silk worm).

Results

Surface exposed hydrophobic residues over domains II and III were targeted for site-directed mutagenesis. Substitution of a phenylalanine residue (F328) by alanine reduced binding to the Bombyx mori cadherin by 23-fold, reduced biological activity against B. mori by 4-fold, while retaining activity against Lymantria dispar.

Conclusion

The results identify a novel receptor-binding epitope and demonstrate that virtual elimination of binding to cadherin BR-175 does not completely remove toxicity in the case of B. mori.     

Fluorescent system based on bacterial expression of hybrid KcsA channels designed for Kv1.3 ligand screening and study

Human voltage-gated potassium channel Kv1.3 is an important pharmacological target for the treatment of autoimmune and metabolic diseases. Increasing clinical demands stipulate an active search for efficient and selective Kv1.3 blockers. Here we present a new, reliable, and easy-to-use analytical system designed to seek for and study Kv1.3 ligands that bind to the extracellular vestibule of the K⁺-conducting pore. It is based on Escherichia coli spheroplasts with the hybrid protein KcsA-Kv1.3 embedded into the membrane, fluorescently labeled Kv1.3 blocker agitoxin-2, and confocal laser scanning microscopy as a detection method. This system is a powerful alternative to radioligand and patch–clamp techniques. It enables one to search for Kv1.3 ligands both among individual compounds and in complex mixtures, as well as to characterize their affinity to Kv1.3 channel using the “mix and read” mode. To demonstrate the potential of the system, we performed characterization of several known Kv1.3 ligands, tested nine spider venoms for the presence of Kv1.3 ligands, and conducted guided purification of a channel blocker from scorpion venom.

The roles of aldehyde dehydrogenases (ALDHs) in the PDH bypass of Arabidopsis

Background

Three spin-labeled mutant proteins, mutated at the beginning, middle, and end of α-helix 5 of the Bacillus thuringiensisCry1Ab δ-endotoxin, were used to study the involvement of these specific amino acid residues in ion transport and to determine conformational changes in the vicinity of these residues when the protein was translocated into a biological membrane.

Results

Amino acid residue leucine 157, located in the N-terminal portion of α-helix 5, showed no involvement in ion transport, and the environment that surrounds the residue did not show any change when transferred into the biological membrane. Serine 170, located in the middle of the α-helix, showed no involvement in ion transport, but our findings indicate that in the membrane-bound state this residue faces an environment that makes the spin less mobile, as opposed to the mobility observed in an aqueous environment. Serine 176, located in the C-terminal end of the α-helix 5 is shown to be involved in ion transport activity.

Conclusion

Ion transport data for L157, S170, and S176, along with the mobility of the spin-labels, structural characterization of the resulting proteins, and toxicity assays against a target insect, suggest that the toxin undergoes conformational changes upon protein translocation into the midgut membrane. These conformational changes result in the midregion of the α-helix 5 being exposed to a hydrophobic-like environment. The location of these three residues in the toxin suggests that the entire α-helix becomes inserted in the insect midgut membrane.     

A colorimetric sensor for the recognition of biologically important anions

A colorimetric anion sensor 1 based on 3-phthaloyl-N-4-nitrophenylhydrozone was synthesized and characterized. The binding ability evaluated by UV?Cvis experiment reveals that 1 can selectively recognize fluoride. Further insights into the nature of interactions between sensor 1 and anions were investigated by H NMR titrations experiments. In addition, the color changes induced by fluoride can provide a way of detection by ??naked-eye??.     

Symmetry-itemized enumeration of quadruplets of RS-stereoisomers: I—the fixed-point matrix method of the USCI approach combined with the stereoisogram approach

The RS-stereoisomeric group $\mathbf{T}_{d\widetilde{\sigma }\widehat{I}}$ is examined to characterize quadruplets of RS-stereoisomers based on a tetrahedral skeleton and found to be isomorphic to the point group $\mathbf{O}_{h}$ of order 48. The non-redundant set of subgroups (SSG) of $\mathbf{T}_{d\widetilde{\sigma }\widehat{I}}$ is obtained by referring to the non-redundant SSG of $\mathbf{O}_{h}$ . The coset representation for characterizing the orbit of the four positions of the tetrahedral skeleton is clarified to be $\mathbf{T}_{d\widetilde{\sigma }\widehat{I}}(/\mathbf{C}_{3v\widetilde{\sigma }\widehat{I}})$ , which is closely related to the $\mathbf{O}_{h}(/\mathbf{D}_{3d})$ . According to the unit-subduced-cycle-index (USCI) approach (Fujita in Symmetry and combinatorial enumeration in chemistry. Springer, Berlin, 1991), the subdution of $\mathbf{T}_{d\widetilde{\sigma }\widehat{I}}(/\mathbf{C}_{3v\widetilde{\sigma }\widehat{I}})$ is examined so as to generate unit subduced cycle indices with chirality fittingness (USCI-CFs). The fixed-point matrix method of the USCI approach is applied to the USCI-CFs. Thereby, the numbers of quadruplets are calculated in an itemized fashion with respect to the subgroups of $\mathbf{T}_{d\widetilde{\sigma }\widehat{I}}$ . After the subgroups of $\mathbf{T}_{d\widetilde{\sigma }\widehat{I}}$ are categorized into types I–V, type-itemized enumeration of quadruplets is conducted to illustrate the versatility of the stereoisogram approach.     

Symmetry-itemized enumeration of RS-stereoisomers of allenes. I. The fixed-point matrix method of the USCI approach combined with the stereoisogram approach

After the RS-stereoisomeric group \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) of order 16 has been defined by starting point group \(\mathbf{D}_{2d}\) of order 8, the isomorphism between \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) and the point group \(\mathbf{D}_{4h}\) of order 16 is thoroughly discussed. The non-redundant set of subgroups (SSG) of \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) is obtained by referring to the non-redundant set of subgroups of \(\mathbf{D}_{4h}\) . The coset representation for characterizing the orbit of the four positions of an allene skeleton is clarified to be \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}(/\mathbf{C}_{s\widetilde{\sigma }\widehat{I}})\) , which is closely related to the \(\mathbf{D}_{4h}(/\mathbf{C}_{2v}^{\prime \prime \prime })\) . According to the unit-subduced-cycle-index (USCI) approach (Fujita, Symmetry and combinatorial enumeration of chemistry. Springer, Berlin 1991), the subduction of \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}(/\mathbf{C}_{s\widetilde{\sigma }\widehat{I}})\) is examined so as to generate unit subduced cycle indices with chirality fittingness (USCI-CFs). Then, the fixed-point matrix method of the USCI approach is applied to the USCI-CFs. Thereby, the numbers of quadruplets are calculated in an itemized fashion with respect to the subgroups of \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) . After the subgroups of \(\mathbf{D}_{2d\widetilde{\sigma }\widehat{I}}\) are categorized into types I–V, type-itemized enumeration of quadruplets is conducted to illustrate the versatility of the stereoisogram approach.     

Quantification of the electrophilicities of dithiocarbenium ions

The reactions of the dithio substituted carbenium ions 2a-c with allylsilanes, allylstannanes (3), and silylated enol ethers (4) which yield dithioacetal protected β, ψ-unsaturated carbonyl compounds (7) and selectively protected 1,3-dicarbonyl compounds (8), have been studied kinetically. The second-order rate constants have been used to determine the electrophilicity parameters for the [1,3]dithiolan-2-ylium ion 2a (E=?6.25) and the [1,3]dithian-2-ylium ions 2b (E=?6.82) and 2c (E=?2.17). It is shown how these parameters can be used to predict the electrophilic potential of 2a-c.     

Copper complexes of two isomeric NS2-macrocycles

Two isomeric NS₂-macrocycles incorporating a xylyl group at ortho (o -L) and meta (m -L) positions were employed and their copper complexes (1?C5) were prepared and structurally characterized. The copper(II) nitrate complexes [Cu(L)(NO₃)₂] (1: L = o -L, 2: L = m -L) for both ligands were isolated. In each case, the copper center is five-coordinated with a distorted square pyramidal geometry. Despite the overall geometrical similarity, 1 and 2 show the different ligand conformation due to the discriminated packing pattern. Reaction of o -L with copper(II) perchlorate afforded complex 3 containing two independent complex cations [Cu(o -L)(H₂O)(DMF)(ClO₄)]⁺ and [Cu(o -L)(H₂O)(DMF)]²⁺; the coordination geometry of the former is a distorted octahedron while the latter shows a distorted square pyramidal arrangement. In the reactions of copper(I) halides (I or Br), o -L gave a mononuclear complex [Cu(o-L)I] (4) with a distorted tetrahedral geometry, while m -L afforded a unique exodentate 2:1 (ligand-to-metal) complex [trans-Br₂Cu(m-L)₂] (5) adopting a trans-type square-planar arrangement.     

Synthesis and antimicrobial activity of novel chalcone derivatives

A series of novel 3-[N, N-bis(2-hydroxyethyl)-amino]-chalcone derivatives 3a–3j were synthesized by the aldol condensation of [N, N-bis(2-hydroethyl)-3-amino]-acetophenone 2 with aromatic aldehydes. Their structures were further confirmed by ESI-HRMS, ¹H NMR, IR and elemental analysis. X-ray analysis reveals crystal 3b is a monoclinic system with P2₁/n space group. The antimicrobial activities of the newly synthesized chalcones in vitro were evaluated and the results indicated that most compounds presented moderate to good antimicrobial activities, especially the antifungal capability. Compounds 3a, 3d, 3f and 3g revealed obvious potency against Candida albicans with MIC values of 32 μg/mL, which were better compared with others.     

Spectroscopic Studies of the Complexation of Iodine with Antihistamine Drugs in Solvents of Varying Relative Permittivity

The interaction of oxatomide (OXA), azacyclonol (AZA) and chloropheniramine (ClPA) antihistamine drugs with iodine was studied spectrophotometrically in different solvents and at three different temperatures. The electronic, FT-IR, far-IR, and mass spectra of the resulting charge-transfer (CT) complexes were recorded, in addition to thermal analysis. The results obtained show that the stoichiometries of the reactions are all 1:1. The observed time dependence of the CT band and subsequent formation of $ {\text{I}}_{3}^{ - } $ in solution were related to the slow transformation of the initially formed 1:1 (donor: I₂) outer complex to an inner complex (electron donor?Cacceptor), followed by a fast reaction of the inner complex with iodine to form a triiodide ion. The characteristic strong absorptions of $ {\text{I}}_{3}^{ - } $ are observed around 360?nm. The CT-complexes have the formulae [(OXA)I]⁺ $ {\text{I}}_{3}^{ - } $ , [(AZA)I]⁺ $ {\text{I}}_{3}^{ - } $ and [(ClPA)I]⁺ $ {\text{I}}_{3}^{ - } $ . The formation constants (K), molar absorption coefficients (?? _CT), and thermodynamic parameters ??H ^#, ??S ^# and ??G ^# of these interaction have been determined and discussed.     

Syntheses, characterization and crystal structures of new mono- and bis-Schiff base compounds derived from 1,2,4-triazine and the silver(I) complexes containing mono-Schiff base ligands

Some new Schiff bases, (Z)-4-amino-3-((E)-(R-methoxybenzylidene)hydrazono)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L2), R?=?3 (L3) and R?=?4 (L4)), were synthesized by the condensation reactions of 4-amino-3-hydrazinyl-6-methyl-1,2,4-triazin-5(4H)-one (L1) and corresponding methoxybenzaldehyde in a molar ratio 1:1.5 in high yields. The reaction of L2 and L4 with an excess amount of the corresponding aldehydes gave the unsymmetrical bis-Schiff bases (E)-3-((E)-(R-methoxybenzylidene)hydrazono)-4-((E)-R-methoxybenzylideneamino)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L22) and R?=?4 (L44)), respectively. Furthermore, the reaction of L2?CL4 with silver(I) nitrate in a molar ratio 2:1 led to the silver(I)-complexes with the general formula [Ag(Lx)₂]NO₃ (Lx?=?L2 (2), L3 (3) and L4 (4)). All synthesized Schiff base compounds and complexes were characterized by a combination of IR-, ¹H-NMR spectroscopy, mass spectrometry and elemental analyses. In addition, the structures of L2, L4·CH₃CN, L22·CH₃OH and L44·CH₃OH and complexes 2 and 4 were determined by X-ray diffraction studies.     

Dacin,one metalloproteinase from <Emphasis Type="Italic">Deinagkistrodon acutus</Emphasis> venom inhibiting contraction of mouse ileum muscle

Background

Mice were bitten by five-pace vipers (Deinagkistrodon acutus), and then envenomed. It was well-known that the snake venom mainly disturbed the blood homeostasis of the envenomed victims. Ocassionally, we found that the venom of D. acutus could inhibit the contraction tension of mouse ileum, so in this study we aimed to identify the active component inhibiting the contraction tension of mouse ileum in the snake venom.

Results

The active component inhibiting the contraction tension of mouse ileum, designated as Dacin, was isolated from D. acutus venom, purified to protein homogeneity and composed of a single peptide chain, about 23 kDa analyzed by SDS-PAGE, and 22, 947. 9 Da measured by MALDI-TOF-MS. Not only the results of its PMF blasted by Mascot indicated that Dacin may be one snake venom metalloproteinase (SVMP), but also the results of the biochemical and in-vivo assays as follow demonstrated that it was one SVMP: it cleaved Aα and Bβ chains, not Cγ of bovine fibrinogen within 1 h, and also hydrolyzed fibrin polymer; besides its fibrino(geno)lytic activities were strongly inhibited by β- mercaptoethanol, EDTA and EGTA; and it could induce a hemorrhagic reaction under the dorsal skin of mouse. In the isolated tissue assays, Dacin caused the concentration-dependent and time-dependent inhibitory actions on the spontaneous contraction tension of the ileum smooth muscle of mouse, and the inhibitory effects were irreversible.

Conclusions

Taken together, for the first time one active component (Dacin, a SVMP) that irreversibly inhibited the spontaneous contraction tension of mouse ileum has been isolated and identified from D. acutus venom. The findings may provide not only a new insight for toxicological researches on SVMPs and venoms of the vipers, but also a reference for clinicians to treat the snake-bitten victims. However, Dacin’s inhibitory molecular mechanism will be further studied in the future.

     

Chemiluminescence microarrays in analytical chemistry: a critical review

Multi-analyte immunoassays on microarrays and on multiplex DNA microarrays have been described for quantitative analysis of small organic molecules (e.g., antibiotics, drugs of abuse, small molecule toxins), proteins (e.g., antibodies or protein toxins), and microorganisms, viruses, and eukaryotic cells. In analytical chemistry, multi-analyte detection by use of analytical microarrays has become an innovative research topic because of the possibility of generating several sets of quantitative data for different analyte classes in a short time. Chemiluminescence (CL) microarrays are powerful tools for rapid multiplex analysis of complex matrices. A wide range of applications for CL microarrays is described in the literature dealing with analytical microarrays. The motivation for this review is to summarize the current state of CL-based analytical microarrays. Combining analysis of different compound classes on CL microarrays reduces analysis time, cost of reagents, and use of laboratory space. Applications are discussed, with examples from food safety, water safety, environmental monitoring, diagnostics, forensics, toxicology, and biosecurity. The potential and limitations of research on multiplex analysis by use of CL microarrays are discussed in this review. Figure

Achievements in the development of CL microarray analysis platforms     

Study of the Gas-Phase Intramolecular Aryltrifluoromethylation of Phenyl(Trifluoromethyl)Iodonium by ESI-MS/MS

The gas-phase reactions of the reactive λ ³-phenyl(trifluoromethyl)iodonium (PhI⁺(III)CF₃, 1 at m/z 273) to the radical cation of iodobenzene (PhI^?+, 2 at m/z 204) via the loss of ·CF₃ and the radical cation of trifluoromethylbenzene (PhCF₃ ^?+, 3 at m/z 146) via the loss of ·I, were studied by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Interestingly, the gas-phase intramolecular coupling reaction of CF₃ with phenyl via the CF₃ migration process of 1 at m/z 273 from iodine to the phenyl to give 3 at m/z 146 could only occur according to an intramolecular aromatic substitution mechanism. Density functional theory (DFT) calculations showed that the gas-phase intramolecular aryltrifluoromethylation of 1 at m/z 273 to 3 at m/z 146 occurred via a Meisenheimer complex intermediate (MC), where the triplevalent I center of 1 was reduced to monovalent I. Most importantly, the structure of 3 at m/z 146 derived from 1 at m/z 273 in ESI-MS/MS process was confirmed by comparison of its MS/MS with that of an authentic PhCF₃ ^?+ at m/z 146 acquired from the electron ionization (EI)-MS/MS analysis of PhCF₃. Thus, our studies revealed the intrinsic reactivity tendencies of λ³-phenyl(trifluoromethyl)iodonium under solvent-free conditions.      

Synthesis, structures, and photoluminescence of heteroligand complexes Ln(L)(iso-Bu2PS2)2(NO3) (Ln = Sm, Tb, Dy; L = Phen, 2,2′-Bipy)

Heteroligand complexes Ln(L)(iso-Bu₂PS₂)₂(NO₃) (Ln = Sm, Tb, Dy; L = Phen, 2,2??-Bipy) (I?CVI) are synthesized. The structure of Dy(Phen)(iso-Bu₂PS₂)₂(NO₃) (III) is determined from the data of X-ray structure analysis. The crystal structure of complex III is based on discrete mononuclear molecules in which the Dy atom has distorted dodecahedral coordination (polyhedron N₂O₂S₄). The ligands Phen, iso-Bu₂PS ₂ ^? and NO ₃ ^? are bidentate-cyclic. According to the X-ray diffraction analysis data, complexes I and II are isostructural to compound III. Complexes I?CVI have photoluminescence in the visible spectral range. The photoluminescence spectra of solid samples of compounds I?CVI exhibit bands corresponding to the radiative electron transitions of the Sm³⁺, Tb³⁺, and Dy³⁺ ions. Among the studied compounds I?CVI, the Tb(III) complexes are characterized by the most intense photoluminescence.     

Über Reaktionen mit Betainen, 18. Mitt. Über Betaine und ihre Beziehungen zu N-Yliden. Trifluoracetyl-N-methylide und ihre Beziehungen zu den entsprechenden Ammoniumbasen

The betaines1b–d were prepared⁴ by systematic variation of the alkyl groups and were reacted with trifluoroacetic acid anhydride (TFA) to give the diacyl-ylides2b,c. The betain1d andTFA afford the trifluoroacetate3d ⁵. The salts3b,c, which result from hydrolysis of2b,c as well as3d (X=I) can be transformed in 75 to 83% yield into the monoacyl-ylides4b–d with the help of silver oxide. Aqueous solutions of4a–d exhibit alkalinepH, which points to the formation of the corresponding ammonium bases. In the case of4b,c the bases5b,c could be isolated. It can be shown, that4b,c and5b,c, respectively, undergo a reversible addition or elimination of one mole wather with great ease.     

Construction of two new 3D supramolecular networks with 3-pyridyl-4-yl-benzoic acid ligands: Synthesis, characterization, and luminescence

Two new coordination polymers with 3-pyridyl-4-yl-benzoic acid (3,4-HPybz), namely, [Zn(3,4-Pybz)₂ · 2H₂O] _n (I) and [Ag(3,4-Pybz)(3,4-HPybz)] _n (II), have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. Compound I crystallizes in the triclinic system and has P1 space group. Complex I is an infinite 1D chain polymer and the infinite chains array uniformly in a 3D supramolecular network which posesses abundant O-H...O hydrogen-bonding interactions among the occupied and unoccupied carboxylate O atoms and the coordinated water molecules; compound II crystallizes in the triclinic system and has $P\bar 1$ space group, II is an infinite chain with the repeat sequence of Ag1(I)-Ag2(I)-Ag1(I), in which weak intermolecular interactions play a key role in forming the final 3D supramolecular architectures. The photoluminescences and lifetime of I and II in the solid state have been investigated.     

On the stability of single-walled carbon nanotubes and their binding strengths

The series of rhenium (I) tricarbonyl mixed-ligand complexes ReCl(CO)₃(H_nbpydt) (n?=?2, 1; n?=?4, 2; bpy?=?bispyridine, dt?=?1,3-dithiole) and ReCl(CO)₃(H_nbpyTTF) (n?=?2, 3; n?=?3, 4; TTF?=?Tetrathiafulvalene) have been investigated theoretically to explore the effect of COOH functional group on their electronic structures, spectroscopic properties and their properties as dye in a solar cell. The calculated geometry structure and absorption spectrum of 1 and 3 are generally consistent with the experimental results. By attaching the COOH groups on both bpy and dt (TTF in 4) moiety in 2, the nature of LUMO is also contributed by both π*(bpy) and π*(dt) (π*(TTF) in 4), and the absorptions have an obvious red shift compared with 1 and 3. In addition, it can be found that the transition terminates at the orbital populated by the COOH-appended moieties, and the performance of 2 and 4 in the dye-sensitized solar cell can be enhanced as compared with 1 and 3.     

Synthesis and structure of tri-m-tolylbismuth dicarboxylates

Tri-m-tolylbismuth bis(2-methoxybenzoate) (I) (84%), tri-m-tolylbismuth dibenzoate (II) (91%), and tri-m-tolylbismuth bis(trichloroacetate) (III) (92%) have been synthesized via the reaction between tri-m-tolylbismuth, carboxylic acid, and hydrogen peroxide. According to X-ray diffraction data, a bismuth atom in compounds I–III have a distorted trigonal bipyramidal coordination (disregarding the additional coordination of carbonyl oxygen atoms) to m-tolyl ligands in equatorial positions. The Bi-C bonds in compounds I, II, and III range within 2.193(3)–2.228(5) Å, and the Bi-O and Bi…O(=C) distances are 2.267(3), 2.282(3) Å and 2.791(6), 2.895(6) Å in I; 2.293(2), 2.296(3) Å and 2.815, 2.905(5) Å in II; and 2.278(4), 2.300(4) Å and 3.008(9), 3.115(9) Å in III. The equatorial CBiC angles on the side of Bi…O(=C) contacts are considerably enlarged, thus decreasing the other two angles (150.6°, 104.7°, and 104.7° in I, 140.2°, 107.4°, and 112.3° in II, and 138.0°, 110.1°, and 111.0° in III).     

Synthesis of Au13(glutathionato)8@β-cyclodextrin nanoclusters and their use as a fluorescent probe for silver ions

Heating and drying of the mixture of glutathione-etched gold nanoparticles (Au-SG) and β-cyclodextrin (β-CD) results in the formation of β-CD-capped and glutathionate-protected Au₁₃ nanoclusters (Au₁₃(SG)₈@β-CD). Their particle size, composition, and number of gold atoms and the capping molecules were characterized by scanning electron microscopy, fluorescence, UV–vis absorption, FT-IR spectroscopy and mass spectrometry. The fluorescence of these nanoclusters is specifically enhanced by the addition of Ag(I) ions to the aqueous solution. This effect was exploited to develop a selective and sensitive method for the fluorometric determination of Ag(I) in water in the concentration range between 0.5 nM and 0.1 μM, with a detection limit at 0.3 nM (at a signal-to-noise ratio of 3). Graphical Abstract

β-CD-capped Au₁₃ nanoclusters has been synthesized by heating and drying the mixture of glutathione-etched gold nanoparticles and β-CD. A simple, sensitive and selective FL sensing method for Ag⁺ in environmental water has developed using the Au nanoclusters.