Fragmentation Study of Globularin Through Positive and Negative ESI/MS,CID/MS,and Tandem MS/MS

Abstract

The structure of globularin was studied by a mass spectrometric methodology based on the combined use of positive and negative electrospray ionization, collision‐induced dissociation (CID), and tandem mass spectrometry. The mass spectrometry investigation was achieved through in‐source fragmentation of the deprotonated [M?H]^?, protonated [M+H]⁺, lithiated [M+Li]⁺, sodiated [M+Na]⁺, and potassium‐cationized [M+K]⁺ ions. This allowed collision‐induced dissociation spectra of the ionized molecular ions to be obtained to give valuable structural information regarding the nature of both the glycoside and the aglycone moieties and the effect of metal cationization on the CID spectra. Glycosidic fission and ring cleavages of both aglycone and sugar moieties were the major fragmentation pathways observed during collision‐induced dissociation, where the losses of small molecules, the cinnamoyl and the cinnamate parts were also observed. Alkali metal cationization offers additional fragmentation pathways involving cross rings cleavage under CID conditions. Unlike the dissociation of protonated molecular ions, that of metal‐cationized molecules also provides sugar fragments where the C₀ ⁺ fragment corresponding with the glucose ion was obtained as a major daughter peak for all the studied compounds. Even with low abundance, fragment ions coordinated to K⁺ were also observed from [M+K]⁺.     

The key Cl− ligand for metal‐to‐ligand charge transfer in mononuclear terpyridine ruthenium(II) and binuclear ruthenium(II) tetrapyridylpyrazine complexes

Electronic structures of binuclear ruthenium complexes [Ru₂(terpy)₂(tppz)]⁴⁺ ( 1A ) and [Ru₂Cl₂(L)₂(tppz)]²⁺ {L = bpy ( 2A ), phen ( 3A ), and dpphen ( 4A )} were studied by density functional theory calculations. Abbreviations of the ligands (Ls) are bpy = 2,2′‐bipyridine, phen = 1,10‐phenanthroline, dpphen = 4,7‐diphenyl‐1,10‐phenanthroline, terpy = 2,2′:6′,2″‐terpyridine, and tppz = tetrakis(2‐pyridyl)pyrazine. Their mononuclear reference complexes [Ru(terpy)₂]²⁺ ( 1B ) and [RuClL(terpy)]⁺ {L = bpy ( 2B ), phen ( 3B ), and dpphen ( 4B )} were also examined. Geometries of these mononuclear and binuclear Ru(II) complexes were fully optimized. Their geometric parameters are in good agreement with the experimental data. The binuclear complexes were characterized by electrospray ionization mass spectrometry, UV–Vis spectroscopy, and cyclic voltammograms. Hexafluorophosphate salts of binuclear ruthenium complexes of 3A and 4A were newly prepared. The crystal structure of binuclear complex 1A (PF₆)₄ was also determined. Orbital interactions were analyzed to characterize the metal‐to‐ligand charge‐transfer (MLCT) states in these complexes. The Cl^? ligand works to raise the orbital energy of the metal lone pair, which leads to the low MLCT state. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation,Chemical Characterization and Electronic Spectra of 6-(2-Pyridylazo)-3-Acetamidophenol and Its Metal Complexes

The stereochemistry of new iron (III), cobalt (II), nickel (II), copper (II), zinc (II) and cadmium (II) complexes of 6-(2-pyridylazo)-3-acetamidophenol (H2L) was studied on the basis of their analytical, spectroscopic, magnetic and conductance data. the dissociation constant of the ligand, as well as the stability constants of its metal complexes had been determined by spectrophotometric method. on the basis of infrared spectra, the coordination behaviour of the ligand to the metal ions was investigated. Magnetic susceptibility and solid reflectance spectra measurements were used to infer the structure. the isolated complexes were found to have the general formulae [M (HL). xH₂O] (A).yH₂O, M = Cu (II), Zn (II), Cd (II) and Fe (HI); HL = 6-(2-pyridylazo)-3-acetamido-phenol; a = acetate in the case of Cu (II) and Zn (II) or chloride in the case of Cd (II) and Fe (Ill), x = 1-3 and y=0-5. for [M (H₂L).xH₂O]Cl₂.yH₂O, M = Ni (II) and Co (II); HL = 6-(2-pyridyl-azo)-3-acetamidophenol, x=3 and y=5-6).     

Syntheses,X‐ray crystal structures,and emission properties of protonated tripyridyltriazines and their ruthenium(II) complexes

A series of metal‐free compounds, ie, planar triprotonated triazine, triazineH₃Cl(PF₆)₂ ( 1 ), planar triprotonated triazineH₃Br(PF₆)₂ ( 2 ), and nonplanar monoprotonated triazineHPF₆ ( 3 ), were prepared. Abbreviations used are triazine = tri‐2‐pyridyltriazine. Ruthenium complexes [RuCl(bpy)(L)](PF₆), [RuCl(bpy)(L)](PF₆)₂, and [Ru(L)₂](PF₆)₂ were also prepared, where bpy is 2,2′‐bipyridine and L's are triazine ( 4 ) and monoprotonated triazine ( 5 ), respectively. Ruthenium complexes [Ru(triazine)₂](PF₆)₂ ( 6 ) were also prepared and crystallized. The X‐ray crystal structures of the 3 compounds 1 , 2 , and 3 and the complex 6 were determined. They were also characterized by electrospray ionization mass spectrometry, UV‐vis spectroscopy, and density functional theory calculations.     

The Role of Metal Ion Polymerization in Beer's Law Deviations Using Extractive-Colorimetric Procedures

Abstract

In the solvent extraction of metal chelates, the presence of polymerized metal ion in either the aqueous or organic layer, can cause the efficiency of extraction to vary throughout a range of metal ion concentrations. Should an extractive-colorimetric determination be employed, a deviation from Beer's Law can result in addition to other intrinsic causes. In this study, the nature of the deviation solely due to polymerization is demonstrated. The absorbances of the extracted metal complexes in the organic phases which are calculated from the analytically determined metal ion concentrations and molar absorptivities are plotted versus the initial metal ion concentrations for some 2,2′-pyridil-mono-and bis-2? and ?2.6 in the plots of log D vs. log [M(II)]_org. are found. At initial metal ion concentratiolns greater than 6 × 10^?5 M, marked negative deviations from the straight line are observed.     

Novel Bioactive Co(II), Cu(II), Ni(II) and Zn(II) Complexes with Schiff Base Ligand Derived from Histidine and 1,3-Indandione: Synthesis,Structural Elucidation,Biological Investigation and Docking Analysis

Novel bioactive complexes of Co(II), Cu(II), Ni(II) and Zn(II) metal ions with Schiff base ligand derived from histidine and 1,3-indandione were synthesized and thoroughly characterized by various analytical and spectral techniques. The biological investigations were carried out to examine the efficiency of the binding interaction of all the complexes with calf thymus DNA (CT-DNA). The binding properties were studied and evaluated quantitatively by K_b and K_sq values using UV-visible, fluorescence spectroscopy and voltammetric techniques. The experimental results revealed that the mode of binding of all the complexes with CT-DNA is via intercalation. It is further verified by viscosity measurements and thermal denaturation experiments. From the results of the cleavage study with pUC19 DNA it is inferred that all the complexes possess excellent cleaving ability. The present investigation proved that the binding interaction of all the complexes are significantly strong and the order of binding strength of the complexes is [Ni(L)₂] (K_b = 3.11 × 10⁶ M^?1) > [Co(L)₂] (K_b = 2.89 × 10⁶ M^?1) > [Cu(L)₂] (K_b = 2.64 × 10⁶ M^?1) > [Zn(L)₂] (K_b = 2.41 × 10⁵ M^?1). The complexes were also screened for antibacterial and anticandidal activity. The in vitro cytotoxicity of the ligand and complexes on the NIH/3 T3 mouse fibroblast cell lines were examined using CellTiter-Blue® (CTB) Cell viability assay, which unveiled that all the complexes exhibit more potent activities against NIH/3 T3 cells. Among all the complexes [Zn(L)₂] complex showed the maximum efficiency.     

Synthesis,Spectral Characterization,DNA/ Protein Binding,DNA Cleavage,Cytotoxicity, Antioxidative and Molecular Docking Studies of Cu(II)Complexes Containing Schiff Base-bpy/Phen Ligands

Ternary Cu(II) complexes [Cu(II)(L)(bpy)Cl] 1, [Cu(II)(L)(Phen)Cl] 2 [L = 2,3–dimethyl-1-phenyl-4(2 hydroxy-5-methyl benzylideneamino)-pyrazol-5-one, bpy = 2,2^′ bipyridine, phen =1,10 phenanthroline) were synthesized and characterized by elemental analyses, UV-Visible, FT-IR, ESR, Mass, thermogravimetric and SEM EDAX techniques. The complexes exhibit octahedral geometry. The interaction of the Cu(II) with cailf thymus DNA (CT-DNA) was explored by using absorption and fluorescence spectroscopic methods. The results revealed that the complexes have an affinity constant for DNA in the order of 10⁴ M^?1 and mode of interaction is intercalative mode. The DNA cleavage study showed that the complexes cleaved DNA without any external agent. The interaction of Cu(II) complexes with bovine serum albumin (BSA) was also studied using absorption and fluorescence techniques. The cytotoxic activity of the Cu(II) complexes was probed in HeLa (human breast adenocarcinoma cell line), B16F10 (Murine melanoma cell line) and HEPA1–6 celllines, complex 1 has good cytotoxic activity which is comparable with the doxarubicin drug, with IC₅₀ values ranging from 3 to 12.6 μM. A further molecular docking technique was employed to understand the binding of the complexes towards the molecular target DNA. Investigation of the antioxidative properties showed that the metal complexes have significant radical scavenging activity potency against DPPH radical.     

The Field-Dependent Magnetization of d5–d7 Metal β−Diketonate Complexes and Their Macromolecular Polymers

A vibrating sample magnetometer (VSM) has been used to study the field-dependent magnetization, M(H), of the d⁵?d⁷ metal acetates [M(OAc)₂.nH₂O], metal β?diketonate complexes [M(tba)₂(H₂O)₂] and the macromolecular polymers [M(tba)₂(4,4-bipy)]_n (where, M = Mn(II), Fe(II), and Co(II), OAc = O₂CCH₃, tba = deprotonated 3-benzoyl-1.1.1-trifluoroacetone, and 4,4-bipy = 4,4′-bipyridine). The magnetic field strength (H) was applied in the range of 0?10⁴ O_e at ambient temperature (ca. 23°C). The experimental results showed that the d⁵?d⁷ metal acetate, complexes and polymers exhibit low paramagnetic properties excepting [Fe(tba)₂(4,4-bipy)]_n polymer, which had negative magnetization M(emu/g) showing diamagnetic properties in the range 0?10⁴ O_e. The magnetization was almost equal to zero without an applied magnetic field (H(O_e)) for each d⁵?d⁷ metal acetate, complex, and polymer. The linear M(H) curve had a magnetic saturation for iron and manganese acetate species at the magnetic field strengths of 3.1 × 10³ and 4.7 × 10³ Oe, respectively. The external magnetic field reached 9.0 × 10³ O_e without any saturation magnetization for the cobalt compounds. The coordination effect of 3-benzoyl-1.1.1-trifluoroacetone (H-tba) and 4,4′-bipyridine (4,4′-bipy) ligands on the field-dependent magnetization M(H) and paramagnetic behavior of d⁵?d⁷ metal atoms is discussed. The field-dependent magnetization M(H) curves of metal β?diketonate complexes and the polymers including d⁵?d⁷ metal acetates showed a weak field octahedral geometry.     

Vibrational Spectroscopic Studies of 3,4-Lutidine Metal (II) Tetracyanonickelate Complexes

Infrared and Raman spectra of seven new metal (II) 3,4-lutidine tetracyanonickelate complexes, M(3,4 L)₂ Ni(CN)₄ [where 3,4 L = 3,4 - dimethyl-pyridine or 3,4-lutidine; M = Mn, Fe, Co, Zn, Ni, Cu or Cd] (abbreviated to M - Ni - 3,4 L) have been investigated. Spectroscopic and magnetic susceptibility measurements indicate that the compounds have the structure of Hofmann-type complexes. The copper complex has spectral features different from the other compounds.     

Single and double proton transfer in excited hydroxy derivatives of bipyridyl

Two electronically excited bipyridyl derivatives, [2,2'-bipyridyl]-3,3'-diol (BP(OH)₂) and [2,2'-bipyridyl]-3-ol (BPOH) were compared as examples of fast proton transfer reactions. No primary fluorescence was seen in either case. Temperature effects were measured. Quantum yields of the tautomeric fluorescence at 77 K are 0.56 for BP(OH)₂ and 0.047 for BPOH.In BP(OH)₂ a very efficient double proton transfer (DPT) was observed, in agreement with previous findings [6]. The radiationless are constants of tautomeric BP(OH)₂ is weakly temperature dependent (ΔE = 0.32 kcal/mol.). The photophysical kinetics are insensitive to OH → OD isotopic substitution.In BPOH the single proton transfer (SPT) seems also to be efficient, the decay being strongly controlles by the tentatively identified radiationless mechanism.The probable role of torsional motions in radiations depopulation of the excited for the series bipyridyl (BP)-BPOH-BP(OH)₂.     

Study of Specific Interaction between bis(<Emphasis Type="Italic">p</Emphasis>-phenylene)-34-crown-10-based Substituted Macrocycle and Ni<Superscript>2+</Superscript>

A novel macrocyclic host has been synthesized for the determination of Ni (II) ions in aqueous solution (H₂O-CH₃CN, v/v?=?1:1). Its molecular structure has been verified by ¹H-NMR, ¹³C NMR and mass spectrometry (ESI).This probe shows selectivity towards the presence of Ni (II) ion among various alkali, alkaline earth, and transition metal ions. The formation of a new fluorescence band at 311 nm has been detected due to possible complex formation with increasing Ni²⁺ concentration in the range of 10^?5–10^?4 M. The detection limit is calculated to be 5.22 μM. To our knowledge, it will be the first case for bis(p-phenylene)-34-crown-10 based molecules to recognize Ni²⁺ ions.     

Aftereffects in zeolite‐encapsulated 57Co‐complexes

Tris(2,2'-bipyridyl)-⁵⁷Co^II and bis(2,2':6',2'-terpyridine)-⁵⁷Co^II complexes were synthesised in the supercages of zeolite‐Y in order to study the effect of molecular isolation on the aftereffects of the ⁵⁷Co(EC)⁵⁷Fe decay. As compared to the regular crystalline salts of the complex ions where, according to the emission Mössbauer spectra, the most abundant species is low‐spin Fe^II, the molecular isolation in the zeolite resulted in a larger fraction of low‐spin Fe^III and a varying amount of high‐spin Fe²⁺ species. In the investigated temperature range, 20 K to 295 K, the majority of the changes was observed above 80 K. In the case of tris (2,2'-bipyridyl)-⁵⁷Co^II-Y, the most characteristic change occurred in valence states, while for bis (2,2':6',2'-terpyridine)-⁵⁷Co^II‐Y, the temperature dependence of the spin states was more prominent. The change in the low spin valence states is explained partly by donor-acceptor properties of the zeolite lattice. The variation in the high spin fraction is explained by radiation damage of the ligand sphere and/or fragmentation of the complex ion followed by incomplete recombination in the supercage. Molecular isolation itself did not seem to increase the chance of fragmentation (as a consequence of charge neutralization following Auger ionization) of these highly conjugated complex molecules.     

Study of Infrared and Electronic Spectra Of N-Exadecyl-8-hydroxy-2-quinolinecarboxamide Complexes

The infrared and electronic spectra of twelve amphiphilic complexes of N-hexadecyl-8-hydroxy-2-quinoline carboxamide (HL) have been investigated. In IR spectra a linear relationship between the v (C-O) frequency in C-O-M bond of the complexes and the relative atomic weight of the central metal ions and a linear relationship between the v (C-O) frequency and the ionization potential of the central metal (M →M²⁺(g)+2e) were obtained. These complexes appeared to fall into two groups. One is the complexes of closed-shell metal ions such as Ca(II), Mg(II), Zn(II), Cd(II), Al(III), La(III) and Gd(III) ion, the other is the complexes of transitional metal ions such as Mn(II), Co(II), Ni(II) and Cu(II) ion. All these complexes can form stable monolayer and can be deposited as uniform LB films.     

Infrared Spectra of Some Metal (II) Complexes of 2-Aminomethylpyridine

Abstract

Band assignments in the IR spectra (700–150 cm^?1) of [M(amp)₃] (ClO₄)₂ (amp = 2-aminomethylpyridine; M = Mn(II), Fe(II), Co(II), Ni(II), Zn(II), [Zn(amp)₂Cl₂] and [Pt(amp)Cl₂] derived from amp-ND₂, their unlabelled analogues, [Zn(amp)₂X₂] (X = Br, I) and [Pt(amp)Br₂] are discussed.     

Electronic structure and spectra of [Cr(C6H6)2]+ and [Fe(C5H5)2]+

The high-resolution N.M.R. spectra of a series of bicyclo [2.2.1] heptanols are discussed. Three unusual features are observed: (a) relatively large ⁴ J's; (b) unequal J _endo-endo's and J _exo-exo's; and (c) unusual magnetic shieldings.

These are presented as empirical phenomena and only little attempt is made to discuss their implications.     

PMOXA/PAA混合刷用于毛细管电泳在线富集牛血清蛋白

本文发展了一种对蛋白质具有吸附/释放功能的二元混合刷涂层(BBC)毛细管,并将其用于蛋白质的在线富集. 通过阳离子开环聚合可逆加成断裂链转移聚合,分别合成了末端为氨基的聚(2-甲基-2噁唑啉)(PMOXA-NH₂)以及末端为巯基的聚丙烯酸(PAA-SH). 然后通过聚多巴胺黏合层将PMOXA-NH₂和PAA-SH依次接枝到熔融硅毛细管内表面,制备出基于聚(2-甲基-2-噁唑啉)(PMOXA) 和聚丙烯酸(PAA)的BBC毛细管. 利用扫描电镜、X射线光电子能谱分析了在毛细管内表面或毛细管原材料上形成的PMOXA/PAA涂层的厚度及组成. 通过荧光显微镜研究了一定pH及离子强度(I)下,BBC毛细管对蛋白质的吸附/释放功能. 结果表明, pH=5.0 (I=10^-5 mol/L)时,BBC毛细管可以吸附牛血清蛋白(BSA),而当pH=9.0 (I=10^-1 mol/L)时,吸附的BSA可被释放出来. 将这种具有蛋白质吸附/释放功能的涂层管用于毛细管电泳在线富集BSA,以提高BSA的检测灵敏度. 结果表明,在最佳条件下,BSA的灵敏度增强因子超过了5000.     

Calix Receptor Edifice; Scrupulous Turn Off Fluorescent Sensor for Fe(III), Co(II) and Cu(II)

Novel Supramolecular fluorescence receptor derived from calix-system i.e. calix[4]resorcinarene bearing dansylchloride as fluorophore was designed and synthesized. The compound was purified by column chromatography and characterized by elemental analysis, NMR and Mass spectroscopy. Tetradansylated calix[4] resorcinarene (TDCR) shows a boat conformation with C₂v symmetry. The complexation behaviour of metal cations [Ag(I), Cd(II), Co(II), Fe(III), Hg(II), Cu(II), Pb(II), Zn(II), U(VI) (1?×?10^-4?M)] with tetra dansylated calix[4]resorcinarene (1?×?10^-6?M) was studied by spectophotometry and spectrofluorometry. Red shift in the absorption spectra led us to conclude that there is strong complexation Fe(III), Co(II) and Cu(II) with TDCR. These metal cations also produce quenching with red shifts in the emission spectra. The maximum quenching in emission intensity was observed in the case of Fe(III) and its binding constant was also found to be significantly higher than that of Co(II) and Cu(II). Quantum yield of metal complexes of Fe(III) was found to be lower in comparison with Co(II) and Cu(II) complexes. Stern Volmer analysis indicates that the mechanism of fluorescence quenching is either purely dynamic, or purely static.     

DNA Binding,Cleavage and Antibacterial Activity of Mononuclear Cu(II), Ni(II) and Co(II) Complexes Derived from Novel Benzothiazole Schiff Bases

A series of novel bivalent metal complexes M(L₁)₂ and M(L₂)₂ where M = Cu(II), Ni(II), Co(II) and L₁ = 2-((benzo [d] thiazol-6-ylimino)methyl)-4-bromophenol [BTEMBP], L₂ = 1-((benzo [d] thiazol-6-ylimino)methyl) naphthalen-2-ol [BTEMNAPP] were synthesized. All the compounds have been characterized by elemental analysis, SEM, Mass, ¹H NMR, ¹³C NMR, UV–Vis, IR, ESR, spectral data and magnetic susceptibility measurements. Based on the analytical and spectral data four-coordinated square planar geometry is assigned to all the complexes. DNA binding properties of these complexes have been investigated by electronic absorption spectroscopy, fluorescence and viscosity measurements. It is observed that these binary complexes strongly bind to calf thymus DNA by an intercalation mode. DNA cleavage efficacy of these complexes was tested in presence of H₂O₂ and UV light by gel electrophoresis and found that all the complexes showed better nuclease activity. Finally the compounds were screened for antibacterial activity against few pathogens and found that the complexes have potent biocidal activity than their free ligands.     

Synthesis,Characterization, DNA Binding Properties,Fluorescence Studies and Antioxidant Activity of Transition Metal Complexes with Hesperetin-2-hydroxy Benzoyl Hydrazone

A novel Schiff-base ligand (H₅L), hesperetin-2-hydroxy benzoyl hydrazone, and its copper (II), zinc (II) and nickel (II) complexes (M·H₃L) [M(II) = Cu, Zn, Ni], have been synthesized and characterized. The ligand and Zn (II) complex exhibit green and blue fluorescence under UV light and the fluorescent properties of the ligand and Zn (II) complex in solid state and different solutions were investigated. In addition, DNA binding properties of the ligand and its metal complexes have been investigated by electronic absorption spectroscopy, fluorescence spectra, ethidium bromide displacement experiments, iodide quenching experiments, salt effect and viscosity measurements. Results suggest that all the compounds bind to DNA via an intercalation binding mode. Furthermore, the antioxidant activity of the ligand and its metal complexes was determined by superoxide and hydroxyl radical scavenging methods in vitro. The metal complexes were found to possess potent antioxidant activity and be better than the free ligand alone and some standard antioxidants like vitamin C and mannitol.     

Zn2+-Schiff’s Base Complex as an “On–Off-On” Molecular Switch and a Fluorescence Probe for Cu2+ and Ag+ Ions

The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of Schiff’s base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (H₂L) and its metal complexes with Zn²⁺, Cu²⁺ and Ag⁺ ions. This study aims to investigate the behavior of H₂L and the binuclear Zn²⁺ complex (1) as fluorescent probes for the detection of metal ions (Zn²⁺, Cu²⁺ and Ag⁺) using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The six conformers of the H₂L ligand were optimized using the B3LYP/6–311?+??+?G** level of theory, while the L^?2-metal complexes were optimized by applying the B3LYP functional with the LANL2DZ/6–311?+??+?G** mixed basis set. The gas-phase and solvated Enol-cis isomer (E-cis) was found to be the most stable species. The absorption spectra of the E-cis isomer and its metal complexes were simulated using B3LYP, CAM-B3LYP, M06-2X and ωB97X functionals with a 6–311?+??+?G** basis set for C, O, N and H atoms and a LANL2DZ basis set for the metal ions (Zn²⁺, Cu²⁺ and Ag⁺). The computational results of the B3LYP functional were in excellent agreement with the experimental results. Hence, it was adopted for performing the emission calculations. The results indicated that metal complex (1) can act as a fluorescent chemosensor for the detection of Ag⁺ and Cu²⁺ ions through the mechanism of intermolecular charge transfer (ICT) and as a molecular switch “On–Off-On” via the replacement of Cu²⁺ by Ag⁺ ions, as proved experimentally.