Electrospray Ionization Mass Spectrometry Data Research Articles

Characterizing the Size and Composition of Saposin A Lipoprotein Picodiscs.

Saposin A (SapA) lipoprotein discs, also known as picodiscs (PDs), represent an attractive method to solubilize glycolipids for protein interaction studies in aqueous solution. Recent electrospray ionization mass spectrometry (ESI-MS) data suggest that the size and composition of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)-containing PDs at neutral pH differs from those of N,N-dimethyldodecylamine N-oxide determined by X-ray crystallography. Using high-resolution ESI-MS, multiangle laser light scattering (MALLS), and molecular dynamics (MD) simulations, the composition, heterogeneity, and structure of POPC-PDs in aqueous ammonium acetate solutions at pH 4.8 and 6.8 were investigated. The ESI-MS and MALLS data revealed that POPC-PDs consist predominantly of (SapA dimer + iPOPC) complexes, with i = 23-29, and have an average molecular weight (MW) of 38.2 ± 3.3 kDa at pH 4.8. In contrast, in freshly prepared solutions at pH 6.8, POPC-PDs are composed predominantly of (SapA tetramer + iPOPC) complexes, with i = 37-60, with an average MW of 68.0 ± 2.7 kDa. However, the (SapA tetramer + iPOPC) complexes are unstable at neutral pH and convert, over a period of hours, to (SapA trimer + iPOPC) complexes, with i = 29-36, with an average MW of 51.1 ± 2.9 kDa. The results of molecular modeling suggest spheroidal structures for the (SapA dimer + iPOPC), (SapA trimer + iPOPC), and (SapA tetramer + iPOPC) complexes in solution. Comparison of measured collision cross sections (Ω) with values calculated for gaseous (SapA dimer + 26POPC)8+, (SapA trimer + 33POPC)12+, and (SapA tetramer + 42POPC)16+ ions produced from modeling suggests that the solution structures are largely preserved in the gas phase, although the lipids do not maintain regular bilayer orientations.

Inhibitory effects of IL-6-induced STAT3 activation of bio-active compounds derived from Salvia plebeia R.Br

Abstract Salvia plebeia R.Br. (SPRB) is a natural resource that exhibits various biological activities. However, its effects on inflammatory diseases are not yet well characterized. This study aimed to evaluate the inhibitory effects of a compound derived from SPRB on interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) activation. The chemical structure of active compounds isolated from the EtOAc-soluble fraction of SPRB were elucidated by comparison with spectroscopic nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI–MS) data in the literature, which resulted in the identification of 22 known compounds. All of the isolated compounds were evaluated for potentially higher inhibitory effects on IL-6-induced STAT3 activation in Hep3B cells using a luciferase reporter assay. Furthermore, the protein levels of p-STAT3, p-ERK, and p-JAK2 in IL-6 induced U266 cells were regulated in the presence of cirsimaritin from SPRB by western blot assay. Based on these findings, we suggest that SPRB has the potential to inhibit IL-6-induced STAT3 activation and should be considered in functional food and pharmaceutical applications.

Pteleifolols A-E, acetophenone di-C-glycosides and a benzopyran dimer from the leaves of Melicope pteleifolia.

Four new acetophenone di-C-glycosides, pteleifolols A-D (1-4) and a new dimeric benzopyran, pteleifolol E (5), were isolated from the leaves of Melicope pteleifolia. Seven known compounds, including 2,4,6-trihydroxyacetophenone-3,5-di-C-glucopyranoside (6), were also isolated. Structures of the new compounds (1-5) were established by using spectroscopic and spectrometric techniques, including 1D and 2D nuclear magnetic resonance (NMR), UV, and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) data. Pteleifolols A-D (1-4) were E-p-coumaroyl, Z-p-coumaroyl, E-feruloyl, and benzoyl esters of 6, respectively. Pteleifolol E (5) was a dichromene dimerized through a C2 unit.

Crystal Structure and Theoretical Analysis of Green Gold Au30(S-tBu)18 Nanomolecules and Their Relation to Au30S(S-tBu)18

We report the complete X-ray crystallographic structure as determined through single-crystal X-ray diffraction and a thorough theoretical analysis of the green gold Au30(S-tBu)18. While the structure of Au30S(S-tBu)18 with 19 sulfur atoms has been reported, the crystal structure of Au30(S-tBu)18 without the μ3-sulfur has remained elusive until now, though matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS) data unequivocally show its presence in abundance. The Au30(S-tBu)18 nanomolecule not only is distinct in its crystal structure but also has unique temperature-dependent optical properties. Structure determination allows a rigorous comparison and an excellent agreement with theoretical predictions of structure, stability, and optical response.

Antiproliferative Butyrolactones from Mezilaurus crassiramea

Bioassay-guided fractionation of the ethanol extract from the leaves of Mezilaurus crassiramea, which was toxic to Artemia salina larvae, afforded 3′-acetylrubrenolide (1), 2′,3′-diacetylrubrenolide (2), and rubrenolide (3) from the active dichloromethane soluble fraction. Compound 1 is new, while 2 and 3 are first reported from a natural source and in the Mezilaurus genus, respectively. Compound 3 showed significant cytotoxicity against UACC-62, MCF-7, HT-29, and PC-3 human cancer cell lines, with GI50 values ranging from 3.3 to 9.9 µg/mL, while 1 and 2 exhibited marginal activities against at least five of the six investigated cell lines. The structures of 1–3 were established on the basis of 1D- and 2D-nuclear magnetic resonance analyses, high-resolution electrospray ionization mass spectrometry data and specific optical rotation values.

Antihypertensive Effects of Artemisia scoparia Waldst in Spontaneously Hypertensive Rats and Identification of Angiotensin I Converting Enzyme Inhibitors.

We investigated the antihypertensive effects of Artemisia scoparia (AS) in spontaneously hypertensive rats (SHR). The rats were fed diets containing 2% (w/w) hot water extracts of AS aerial parts for 6 weeks. The AS group had significantly lower systolic and diastolic blood pressure levels than the control group. The AS group also had lower angiotensin I converting enzyme (ACE) activity and angiotensin II content in serum compared to the control group. The AS group showed higher vascular endothelial growth factor and lower ras homolog gene family member A expression levels in kidney compared to the control group. The AS group had significantly lower levels of plasma lipid oxidation and protein carbonyls than the control group. One new and six known compounds were isolated from AS by guided purification. The new compound was determined to be 4′-O-β-d-glucopyranoyl (E)-4-hydroxy-3-methylbut-2-enyl benzoate, based on its nuclear magnetic resonance and electrospray ionization-mass spectroscopy data.

Soft Ionization of Metallo-Mefenamic Using Electrospray Ionization Mass Spectrometry

Detection of mefenamic acid (M, non-steroidal anti-inflammatory drug, NSAIDs) and its metallodrug was investigated using electrospray ionization mass spectrometry (ESI-MS) and fluorescence spectroscopy. ESI-MS data (500 μL, 1×10-3 M) revealed high detection sensitivity for the drug and metallodrug. ESI-MS spectra revealed peaks at 242, 580, and 777 Da corresponding to [M+H]+, [63Cu(M-H)2(H2O)2+H]+, and [56Fe(M-H)3+H]+, respectively. The metal:mefenamic ratios of ESIMS spectra are in complete agreement with the fluorescence spectroscopy results (1:2 for Cu(II) and 1:3 for Fe(III)). ESI is a soft ionization technique that can be used on labile metallo-mefenamic acids and is promising for the detection of these species in environmental samples and biological fluids.

Effect of Cocaine and p21 on the Blood Lipidome

Cocaine is powerfully addictive and induces a breadth of physiological effects, even at low, recreational doses. To begin to discern the full extent of these effects, we used electrospray ionization‐mass spectrometry (ESI‐MS) by direct infusion to investigate drug‐induced alterations on the blood lipidome. Lipids were extracted from the whole blood of mice exposed to cocaine or saline using the Bligh‐Dyer method. ESI‐MS data was analyzed with multivariate principal component analysis to determine changes in lipid profile. Significant m/z features indicated alterations in four categories: fatty acyls, glycerolipids, glycerophospholipids and sphingolipids. Features were further identified into classes within each category, with prominent classes being acyl coenzyme A, triacylglycerol, cardiolipin and ceramide, respectively. While the directionalities varied, the greatest number of altered features were sphingolipids. Remarkably, some features correlated to drug‐seeking behaviors in cocaine‐treated mice, specifically locomotor response. How cocaine‐induced effects occur, including alterations in lipid profile, is not fully understood. Our data using a p21 knockout mouse model suggests a role for the cell cycle regulator in cocaine‐induced response in vivo and the effects of genetic ablation of p21 also extended to the blood lipidome. Knockout mice had distinct lipidomic profiles compared to wild‐type mice, indicating that p21 affects the blood lipidome. Again, the majority of significantly altered features were sphingolipids. Moreover, cocaine exposure also altered the blood lipidome in the knockout mice. Collectively, these results suggest not only a role for cocaine, but also for p21 in regulating the blood lipidome.

Tiliabisflavan A, a New Flavan‐3‐ol Dimer from Tilia amurensis with Cytotoxic and Anti‐Inflammatory Effects

In the search for anticancer compounds from Korean medicinal plants, themethanolic extract from the trunk ofTilia amurensis Rupr. (Tiliaceae) was found to have significant cytotoxicity against A549 (lung carcinoma), SK-OV-3 (ovary malignant ascites), SK-MEL-2 (skinmelanoma), andHCT-15 (colon adenocarcinoma) in our screening test. T. amurensis is commonly known as “bee tree” and widely distributed in the mountainous areas of Korea, China, and Japan. T. amurensis has been used to treat various diseases as a Korean traditional medicine from ancient times. Its flowers have been applied for alleviating a fever, and its leaves have also been traditionally used for analgesia and rheumatoid arthritis. Importantly, an extract of this tree has been used to treat stomach cancer without any side effects. A recent pharmacological study revealed the potential of T. amurensis as an anticancer agent by evaluating the DNA topoisomerase inhibitory activity. However, only a few constituents associated with the anticancer activity from T. amurensis have been reported. Recently, our phytochemical investigations on T. amurensis revealed the presence of bioactive lignan constituents with antitumor and anti-inflammatory activities. Our continuing interest in further research on the bioactive constituents from T. amurensis led us to investigate bioactive metabolites of T. amurensis trunk. A bioassay-guided fractionation and chemical investigation of its MeOH extract resulted in the isolation and identification of four flavan-3-ols, including a new flavan-3-ol dimer, tiliabisflavanA (1) (Figure 1). The isolated compounds were evaluated for their antiproliferative activities against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines, as well as their inhibitory effects on NO production in a lipopolysaccharide (LPS)-activated BV-2 cell line. Compound 1 was obtained as a colorless gum. The molecular formula of 1 [ α 1⁄2 25 D +31.5 (c 0.35, MeOH)] was determined to be C31H28O12 based on positive high-resolution electrospray ionization mass spectrometry (HR-ESIMS) data (m/z 615.1479 [M +Na], calcd for C31H28NaO12, 615.1478). The infrared (IR) spectrum showed absorption bands for hydroxyl group (3358 cm) and aromatic rings (1614 and 1450 cm). The structure of 1 was further elucidated by detailed analysis of H and C NMR chemical shifts and by heteronuclear multiple-quantum correlation (HMQC) and heteronuclear multiple-bond correlation (HMBC) experiments. The H and CNMR spectra of 1were similar to those of2 except for the particular signals assigned tomethylene carbon [δH 3.88 (s); δC 15.5]. The assigned proton and carbon resonances of 1 in CD3OD are summarized in Table 1. The H, C NMR, and HMQC spectra of 1 displayed the characteristic signals for theC-ring of flavan-3-ol [δH4.75 (br s,H-2), 4.10 (br s, H-3), 2.82 (dd, J = 16.5, 4.5, H-4a), and 2.67 (dd, J = 16.5, 3.5, H-4b); δC 79.2 (C-2), 66.0 (C-3), and 27.7 (C-4)]. In addition, the 1,3,4-trisubstituted B ring signals [δH 6.94 (d, J = 1.5,H-20), 6.72 (overlap,H-50, H-60); δC144.7 (C-30, C-40), 130.5 (C-10), 118.5 (C-60), 114.7 (C-50), and 114.2 (C-20)] were observed, together with the A-ring carbon signals [δC 154.6 (C-5), 154.0 (C-7), 152.4 (C-9), 105.5 (C-8), 99.3 (C10), and 95.6 (C-6)]. The NMR data were closely related to those of 2; however, instead of the two A ring aromatic methines (C-6, C-8) in 2, the NMR spectra of 1 showed only one aromatic methine (δC 95.6, CH) for the A ring and an additional quaternary aromatic carbon (δC 105.5, C) as well as particular benzylic methylene signals [δH 3.88 (s); δC 15.5 (CH2)]. This indicated that compound 1 is comprised symmetrically of two epicatechin units connectingC-6 andC-8 positions through amethylene bridge. In theHMBCspectrum (Figure 2), the CH2 proton signal at δH 3.88 showed HMBC correlations with δC 154.0 (C-7), 152.4 (C-9), and 105.5 (C-8), which revealed that the two epicatechin units in 1 were linked between their C-8 position through amethylenebridge.Theother partial structures of 1 were clearly elucidated by the interpretation of the H–H correlation spectroscopy (COSY) and HMBC, and thus, the gross structure of 1 was established as shown in Figure 1 and named tiliabisflavan A. The relative configurations of C-2 and C-3 in 1 were determined to be cis for (2R,3R) or (2S,3S) configuration [δC 79.2 (C-2)/66.0 (C-3) and J3,4a = 4.5 Hz, J3,4b = 3.5 Hz for 1] on the basis of the comparison with the chemical shifts of C-2/ C-3 [δC 79.9/67.5 for (+)-epicatechin (2) and δC 82.6/68.7 for (+)-catechin (3)] and the coupling constants of H-3/H-4 Note DOI: 10.1002/bkcs.10011 K. H. Kim et al. BULLETIN OF THE KOREAN CHEMICAL SOCIETY

Electrolytic Conditioning of a Magnesium Aluminum Chloride Complex for Reversible Magnesium Deposition

We describe in this report the electrochemistry of Mg deposition and dissolution from the magnesium aluminum chloride complex (MACC). The results define the requirements for reversible Mg deposition and definitively establish that voltammetric cycling of the electrolyte significantly alters its composition and performance. Elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDS) results demonstrate that irreversible Mg and Al deposits form during early cycles. Electrospray ionization mass spectrometry (ESI-MS) data show that inhibitory oligomers develop in THF-based solutions. These oligomers form via the well-established mechanism of a cationic ring-opening polymerization of THF during the initial synthesis of the MACC and under resting conditions. In contrast, MACC solutions in 1,2-dimethoxyethane (DME), an acyclic solvent, do not evolve as dramatically at open circuit potential. From these results, we propose a mechanism describing how the conditioning process of the MACC in THF improves its performance by both tuning the Mg:Al stoichiometry and eliminating oligomers.

Mesomeric metallosupramolecular grid architectures

We describe herein the self-assembly processes as well as the structural properties of metallosupramolecular grid-architectures, involving bis-bidentate ligand 1, based on imino-pyridine complexation subunits and tetrahedrally (Cu+, Ag+) and octahedrally (Co2+, Zn2+, Fe2+) coordinated metal ions. The NMR, electrospray ionisation mass spectrometry data and X-ray crystal structure results suggest that in solution corner- and grid-type compounds are present, while in the solid state they adopt very compact and stable [2 × 2] grids arrays. Despite the variable binding behaviours of tetrahedrally coordinated cations (Cu+, Ag+) and the four coordination (lower) number of octahedrally coordinated cations (Co2+, Zn2+, Fe2+), the flexibility of the ligand 1 induce a perfect arrangement of these components, resulting in the formation of metallosupramolecular grids. Examination of such structures suggests that simple conformational rotation around the central phenyl of ligand 1 results in the self-assembly of chiral ligands. This allows the formation of mesomeric grid-type superstructures containing an inversion centre with half-superior and -inferior inner surfaces of opposite chirality.

Mononuclear and Tetranuclear Compounds of Yttrium and Dysprosium Ligated by a Salicylic Schiff-Base Derivative: Synthesis, Photoluminescence, and Magnetism

The Schiff-base (2-aminoethyl)hydroxybenzoic acid (H(2)L) as a proligand was prepared in situ from 3-formylsalicylic acid and ethanolamine (ETA). The mononuclear {[Y(HL)(4)][ETAH]·H(2)O} (1) and {[Dy(HL)(4)] [ETAH]·3MeOH·H(2)O} (2) and tetranuclear {[Y(4)(HL)(2)(L)(4)(μ(3)-OH)(2)]·4MeOH·4H(2)O} (3), {[Dy4(HL)(2)(L)(4)(μ(3)-OH)(2)]·5(MeOH)(2)·7H(2)O (4), and {[Dy(4)(HL)(8)(L)(2)]·4MeOH·(2)H(2)O}(5) rare-earth metal complexes of this ligand could be obtained as single-crystalline materials by the treatment of H(2)L in the presence of the metal salts [Ln(NO(3))(3)·(H(2)O)m] (Ln = Y, Dy). In the solid state, the tetranuclear compounds 3 and 4 exhibit butterfly structures, whereas 5 adopts a rectangular arrangement. Electrospray ionization mass spectrometry data of the ionic compounds 1 and 2 support single-crystal X-ray analysis. The yttrium compounds 1 and 3 show fluorescence with 11.5% and 13% quantum yield, respectively, whereas the quantum yield of the dysprosium complex 4 is low. Magnetic studies on the dysprosium compounds 4 and 5 suggest the presence of weak antiferromagnetic interactions between neighboring metal centers. Compound 4 shows single-molecule-magnet behavior with two relaxation processes, one with the effective energy barrier U(eff) = 84 K and the preexponential factor τ(0) = 5.1 × 10(-9) s.

Anion Binding Properties of Alkynylplatinum(II) Complexes with Amide-Functionalized Terpyridine: Host-Guest Interactions and Fluoride Ion-Induced Deprotonation.

Molecular sensors able to detect ions are of interest due to their potential application in areas such as pollutant sequestration. Alkynylplatinum(II) terpyridine complexes with an amide-based receptor moiety have been synthesized and characterized. Their anion binding properties based on host–guest interactions have been examined with the use of UV-vis absorption and emission spectral titration studies. Spectral changes were observed for both complexes upon the addition of spherical and nonspherical anions. Their titration profiles were shown to be in good agreement with theoretical results predicting a 1:1 binding model, and the binding constants were determined from the experimental data. Drastic color changes from yellow to orange–red were observed for one of the complexes upon titration with fluoride (F−) ion in acetone. These changes were ascribed to the deprotonation of the amide functionalities induced by F− ion, and this was confirmed by the restoration of spectral changes upon addition of trifluoroacetic acid to the F− ion–complex mixture as well as by electrospray ionization mass spectrometry (ESI-MS) data.

Pyrrolobenzodiazepines (PBDs) do not bind to DNA G-quadruplexes.

The pyrrolo[2,1-c][1,4] benzodiazepines (PBDs) are a family of sequence-selective, minor-groove binding DNA-interactive agents that covalently attach to guanine residues. A recent publication in this journal (Raju et al, PloS One, 2012, 7, 4, e35920) reported that two PBD molecules were observed to bind with high affinity to the telomeric quadruplex of Tetrahymena glaucoma based on Electrospray Ionisation Mass Spectrometry (ESI-MS), Circular Dichroism, UV-Visible and Fluorescence spectroscopy data. This was a surprising result given the close 3-dimensional shape match between the structure of all PBD molecules and the minor groove of duplex DNA, and the completely different 3-dimensional structure of quadruplex DNA. Therefore, we evaluated the interaction of eight PBD molecules of diverse structure with a range of parallel, antiparallel and mixed DNA quadruplexes using DNA Thermal Denaturation, Circular Dichroism and Molecular Dynamics Simulations. Those PBD molecules without large C8-substitutents had an insignificant affinity for the eight quadruplex types, although those with large π-system-containing C8-substituents (as with the compounds evaluated by Raju and co-workers) were found to interact to some extent. Our molecular dynamics simulations support the likelihood that molecules of this type, including those examined by Raju and co-workers, interact with quadruplex DNA through their C8-substituents rather than the PBD moiety itself. It is important for the literature to be clear on this matter, as the mechanism of action of these agents will be under close scrutiny in the near future due to the growing number of PBD-based agents entering the clinic as both single-agents and as components of antibody-drug conjugates (ADCs).

Characteristics of Glycation and Glycation Sites of Lysozyme by Matrix-Assisted Laser Desorption/Ionization Time of Flight/Time-of-Flight Mass Spectrometry and Liquid Chromatography—Electrospray Ionization Tandem Mass Spectrometry

Protein glycation with reducing sugars through the Maillard reaction is regarded as one of the most important reactions in food chemistry. Amadori rearrangement products (ARPs) are produced at the initial stage of the Maillard reaction and then advanced glycation products may be formed. We report here that using matrix-assisted laser desorption/ionization mass spectrometry with time-of-flight detection (MALDI-TOF-MS) and electrospray ionization mass spectrometry (ESI-MS) to monitor the glycation process in lysozyme and the D-glucose model system. MALDI-TOF-MS displayed a heterogeneous distribution of glycation via a total mass shift in spectra. However electrospray ionization mass spectrometry (ESI-MS) data showed that a total of four molecules of glucose reacted with lysozyme at an increase in molecular weight by a 162 Da unit. Further, we identified the glycation sites of lysozyme by using MALDI-TOF/TOF-MS and liquid chromatography (LC)-ESI-MS/MS. Besides the two glycation sites of Lys1 and Lys97 identified by MALDI-TOF/TOF-MS, the other two glycation sites of Lys13 and Lys116 were characterized unambiguously by LC-ESI-MS/MS. Both MALDI-TOF/TOF-MS and LC-ESI-MS/MS provided confidence in the study of the glycation by restricting the number of possible residues through (un)modified ions. The study is useful to monitor and characterize glycation in protein systems based on both MALDI-TOF-MS and ESI-MS. Comparatively, LC-ESI-MS/MS provides more fragments with better recovery for the identification of glycation than MALDI-TOF/TOF-MS.

Potential allelopathic indole diketopiperazines produced by the plant endophytic Aspergillus fumigatus using the one strain-many compounds method.

On the basis of the OSMAC (one strain-many compounds) strategy, 14 indole diketopiperazine (DKP) alkaloids, including spirotryprostatins (1-3), tryprostatins (4-6), and cyclotryprostatins (7-14), were isolated from the endophyte Aspergillus fumigatus associated with Melia azedarach L. Their structures were identified by nuclear magnetic resonance and electrospray ionization mass spectrometry data. All the indole DKPs were evaluated for plant growth regulation using the lettuce (Lactuca sativa) seedling growth bioassay, which showed the plant growth influence of the seedling. Among these compounds tested, a tryprostatin-type compound, brevianamide F (6), was identified as a new type of natural potential plant growth inhibitor with a response index (RI) higher than that of the positive control glyphosate, a broad-spectrum systemic herbicide. 6 can also inhibit turnip (Raphanus sativus) shoot and root elongation with RIs of -0.76 and -0.70, respectively, at 120 ppm, and it strongly inhibits amaranth (Amaranthus mangostanus) seedling growth with a high RI of -0.9 at 40 ppm. The structure-allelopathic activity relationship analysis of these isolated alkaloids indicates that tryprostatin-type alkaloids without the C5 prenyl and methoxy group give the most potent inhibition of seedling growth. Brevianamide F (6) could be used to develop a natural eco-friendly herbicide.

Cysteine accessibility during As3+ metalation of the α- and β-domains of recombinant human MT1a

Metallothionein is a ubiquitous metal binding protein that plays an important role in metal ion homeostasis and redox chemistry within cells. Mammalian metallothioneins bind a wide variety of metals including the metalloid As3+ in two domains (β and α) connected by a short linker sequence. Three As3+ bind in each domain for a total of 6 As3+ per protein. In recombinant human metallothionein (rh-MT1a) each As3+ binds three cysteine residues to form As3Cys9(CysSH)2-α-rhMT1a in the 11 Cys α-domain and As3Cys9-β-rhMT1a in the 9 Cys β-domain. This means that there should be 2 free cysteines in the α-domain but no free cysteines in the β-domain. By using benzoquinone, the number and relative accessibility of the free cysteinyl thiols during the metalation reactions were determined. The electrospray ionization mass spectrometry (ESI-MS) data confirmed that each As3+ binds using exactly 3 cysteine thiols and showed that there was a significant difference in the reactivity of the free cysteines during the metalation reaction. After a reaction with two molar equivalents of As3+ to form As2Cys6(CysSH)3-αβ-rhMT1a, the remaining 3 Cys in the 9 Cys β-domain were far less reactive than those in the α-domain. Molecular dynamics calculations for the metalation reactions with As3+ measured by ESI-MS allowed an interpretation of the mass spectral data in terms of the relative location of the cysteine thiols that were not involved in As3+ coordination. Together, these data provide insight into the selection of a specific cysteinyl thiol by the incoming metals during the stepwise metalation of metallothioneins.

Co-culturing of Catharanthus roseus, Vinca major and Rauwolfia serpentina cell suspensions in shake flask and bioreactor: Production of a novel alkaloid with antioxidant potential

Conditions for co-culturing the cell suspensions of Catharanthus roseus, Rauwolfia serpentina and Vinca major in shake flask and bioreactor are described here for the possible complementation of the terpenoid indole alkaloid pathway operating in them. Catharanthus + Rauwolfia or Catharanthus + Vinca cell combinations could be reared on a Murashige and Skoog medium containing 2.0 mg L-1 naphthalene acetic acid (NAA) and 0.2 mg L-1 kinetin (Kn). A 20- and 40-fold increment in the biomass of these co-cultures was achieved within 30 days in a stirred tank bioreactor. Thin layer chromatography (TLC) of the alkaloid extracts of co-cultures of Rauwolfia + Catharanthus showed the presence of two novel compounds (RF1 and RF2) upon staining with Dragendroff’s reagent. Proton nuclear magnetic resonance (1HNMR), electrospray ionization mass spectrometry (ESI-MS) and ultraviolet (UV) spectral analysis data of these compounds suggested an indole alkaloid identity. Out of these two alkaloids, compound RF1 was found to possess strong antioxidant potential. Key words: Catharanthus roseus, Rauwolfia serpentina, Vinca major, co-culture, terpenoid indole alkaloids, pathway complementation.

Heterometallic CoIII4FeIII2Schiff Base Complex: Structure, Electron Paramagnetic Resonance, and Alkane Oxidation Catalytic Activity

The heterometallic complex [Co(4)Fe(2)OSae(8)]·4DMF·H(2)O (1) was synthesized by one-pot reaction of cobalt powder with iron chloride in a dimethylformamide solution of salicylidene-2-ethanolamine (H(2)Sae) and characterized by single crystal X-ray diffraction analysis, magnetic measurements, high frequency electron paramagnetic resonance (HF-EPR), and Mössbauer spectroscopies. The exchange coupling in the Fe(III)-Fe(III) pair is of antiferromagnetic behavior with J/hc = -190 cm(-1). The HF-EPR spectra reveal an unusual pattern with a hardly detectable triplet signal of the Fe(III) dimer. The magnitude of D (ca. 13.9 cm(-1)) was found to be much larger than in related dimers. The catalytic investigations disclosed an outstanding activity of 1 toward oxidation of cycloalkanes with hydrogen peroxide, under mild conditions. The most efficient system showed a turnover number (TON) of 3.57 × 10(3) with the concomitant overall yield of 26% for cyclohexane, and 2.28 × 10(3)/46%, respectively, for cyclooctane. A remarkable turnover frequency (TOF) of 1.12 × 10(4) h(-1) (the highest initial rate W(0) = 3.5 × 10(-4) M s(-1)) was achieved in oxidation of cyclohexane. Kinetic experiments and selectivity parameters led to the conclusion that hydroxyl radicals are active (attacking C-H bonds) species. Kinetic and electrospray ionization mass spectrometry (ESI-MS) data allowed us to assume that the trinuclear heterometallic particle [Co(2)Fe(Sae)(4)](+), originated from 1 in solution, could be responsible for efficient generation of hydroxyl radicals from hydrogen peroxide.

Cytotoxic cordiaquinones from the roots of Cordia polycephala

The chemical investigation of roots of Cordia polycephala resulted in the isolation of two new terpenoid naphtoquinones, 6-[10-(12,12-dimethyl-13α-(22-methyl-21-butenoyloxy)-16-methenylcyclohexyl)ethyl]-naphtalene-1,4-dione and (6-[10-(12,12-dimethyl-13α-(tigloyloxy)-16-methenylcyclohexyl)ethyl]-naphtalene-1,4-dione, named as cordiaquinone N (1) and O (2), respectively. The known cordiaquinones B (3), L (4) and E (5) were also isolated. Their structures were elucidated after detailed 1D and 2D NMR and high resolution electrospray ionization mass spectrometry (HRESIMS) data analysis. All cordiaquinones (1-5) were evaluated against four human cancer cell lines: HCT-8 (colon), HL-60 (leukemia), MDA-MB-435 (melanoma) and SF295 (glioblastoma), showing IC50 values in the range of 1.2 to 11.1 mmol L-1. The new cordiaquinones 1 and 2 were the most active against all cancer cell lines, while compound 3 was selective to leukemia HL-60 cells (IC50 2.2 mmol L-1).