The spectral studies on the effect of Glu 101 to the metal binding characteristic of Euplotes octocarinatus centrin

Glu is highly conserved as the first amino acid of E-helix of the EF-hand protein. In this paper, Glu 101, the first amino acid of E-helix of the third EF-hand motif in Euplotes octocarinatus centrin (EoCen) was mutated to be Lys by the method of site direct mutation. Tb3+ and TNS were used as fluorescence probes in the study of the effect of this mutation to the metal binding characteristic of EoCen by fluorescence spectra. Results indicate that compared with EoCen, the mutation protein (E101K) displays a different Tb3+ binding characteristic and an increased hydrophobic exposure surface. Polyacrylamide gels electrophoresis indicated that the electrophoretic mobilities of EoCen and E101K are distinctly different. It can be deduced that the conformation of EoCen has been altered by this mutation. The general conditional binding constant of Tb3+ to the three loops of EF-hand sites I-III in E101K was calculated to be (5.64+/-0.57)x10(5)M(-1) according to the modified equation of the single binding process.     

Infrared spectroscopic studies on metal cyanides adsorbed on inorganic support materials

The adsorption of CuCN and KCN onto the surface of inorganic support materials such as silica gel, alumina and charcoal can be conveniently studied by i.r. spectroscopy. The type of support material can have a profound effect on the nature of the adsorbed cyanide.     

New phosphorus-containing metal phthalocyanine complexes. Synthesis and spectral and electrochemical studies

Hitherto unknown phosphorus-containing 4,5-bis(diethoxyphosphorylmethyl)- and 4-methyl-5-diethoxyphosphorylmethylphthalonitriles were synthesized starting from o-xylene. Their tetramerization afforded free phthalocyanine ligands and their complexes with Zn, Ni, Co, and a number of rare-earth metals. The spectral and electrochemical properties of the phthalocyanines synthesized were studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1634–1638, August, 2008.     

Studies on ligand binding of kidney bean leghemoglobin.

Absorption spectra of different ligand derivative;s of kidney bean leghemoglobin alpha have been recorded. The effect of pH on the absorption spectra of kidney bean leghemoglobin alpha has been studied. The pK of the acid-alkaline transition of the heme-linked water molecule is 8.25 and the pK for the acid dissociation of the heme group is 4.03. Affinities of kidney bean leghemoglobin for two different types of ligands have been studied in comparison with soybean leghemoglobins alpha and c and sperm whale myoglobin. All these leghemoglobins have similar affinities for the small anionic ligand fluoride ion, and they are only slightly more accessible to this ligand than is sperm whale myoglobin. Differences in the primary structure or in conformation of these proteins are reflected in the affinity for the bulky ligand imidazole. The accessibility to imidazole increases in the order sperm whale myoglobin less than soybean Lbalpha less than soybean Lbc less than kidney bean Lbalpha, and also low spin Lbalpha less than high spin Lbalpha. The results are discussed with respect to the amino acid sequences of the leghemoglobins.     

Crystal structure of 3-acetylcoumarin-o-aminobenzoylhydrazone and synthesis,spectral and thermal studies of its transition metal complexes

Transition metal [Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)] complexes of a new Schiff base, 3-acetylcoumarin-o-aminobenzoylhydrazone were synthesized and characterized by elemental analyses, magnetic moments, conductivity measurements, spectral [Electronic, IR, ¹H and ¹³C NMR, EPR] and thermal studies. The ligand crystallizes in the monoclinic system, space group P2₁/n with a?=?9.201(5), b?=?16.596(9), c?=?11.517(6)?Å, β?=?101.388(9)°, V?=?1724.2 (17)?ų and Z?=?4. Conductivity measurements indicated Mn(II) and Co(II) complexes to be 1?:?1 electrolytes whereas Ni(II), Cu(II), Zn(II) and Cd(II) complexes are non-electrolytes. Electronic spectra reveal that all the complexes possess four-coordinate geometry around the metal.     

Effects of DNA secondary structure on oligonucleotide probe binding efficiency

Secondary structure motifs in nucleic acid probes generally impair intended hybridization reactions and so efforts to predict and avoid such structures are commonly employed in probe design schemes. Another key facet of probe design that has received much less attention, however, is that secondary structure at targeted probe binding site regions may also impair hybridization. Thus, evaluation of both probe and target site secondary structures together should improve hybridization prediction and design effectiveness. Several challenges confound this goal, including imperfect empirical rules and parameters underlying predictions and the fact that folding algorithms scale poorly with respect to sequence length. Here, we attempt to quantify the consequences of target site structure on predicted hybridization using sequences sampled from the human genome. We also provide a methodology for choosing a reasonable “window size” around target sites that is as small as possible without compromising folding algorithm prediction accuracy.     

Infrared spectroscopic studies of transition metal complexes and polarizability effect

The literature data on substituent influence on the CS, CN, NC, NN, and NO stretching frequencies (ν) in the IR spectra and in specific cases on their respective stretching force constants (k) have been analyzed for 28 series of the transition metal complexes. The ν and k values were first established to depend not only on the inductive and resonance effects but on the polarizability of substituents as well. The contribution of the polarizability effect varies from 0 to 57% with the type of series.     

The pressure tunning Raman and IR spectral studies on the multinuclear metal carbyne complexes

The Raman and infrared (IR) spectra of four tungsten metal carbyne complexes I, II, IV and V [Cl(CO)2(L)W[triple bond]CC6H4[triple bond](C[triple bond]CC6H4)n[triple bond]N[triple bond]C[triple bond]]2M (L = TMEDA, n = 0, M = PdI2 or ReCl(CO)3; L = DPPE, n = 1, M = PdI2 or ReCl(CO)3) were studied at high external pressure. Their pressure-induced phase transitions were observed near 20kbar (complexes I), 15 kbar (complexes II), 25 kbar (complex IV) and 30 kbar (complex V). The pressure-induced phase transition likely is first order in complex I and the pressure-induced phase transitions of complexes II, IV and V are mostly second order. The pressure sensitivities d nu/dp of nu(W[triple bond]C) are high in the low-pressure phase area and very low in the high-pressure phase area due to the pressure strengthening pi back-bonding from metal W to pi* orbital of C[triple bond]O in fragment Cl(CO)2(L)W[triple bond]C. The pressure strengthening metal pi back-bonding from metal Re or Pd to pi* orbital of C[triple bond]O or C[triple bond]N also happened to both of central metal centers of NCPd(I2)CN in complex I and NCReCl(CO)3CN in complex II.     

Infrared and quantum-chemical studies of the structure and vibrations of trisilylamine

New infrared spectra are reported for variously labelled trisilylamines. Quantum-chemical (QC) calculations of structure and force field have been made at HF, MP2 and B3LYP levels, each with the 6-31G* and 6-311G** basis sets. At each level, a minimum in the potential surface occurs at the C3h configuration. No evidence was found for a significant variation in SiH bond length with orientation. The appearance of two bands in the infrared spectrum of N(SiH3)3 in the 2nuSiH region is explained by local mode theory in terms of transitions to (200) and (110) levels. In the gas phase, signal averaging appears to occur in the nuSiH region in the infrared spectrum, but not in the Raman. In solid films, both IR and Raman spectra indicate the presence of a range of SiH bond strengths, corresponding to an absence of any site symmetry. Each complete QC calculated force field was fitted to the frequencies observed for N(SiH3)3 and N(SiD3)3, using nine independent scale factors. An interaction force constant between nu(as)NSi3 and delta(s)SiH3 motions required further adjustment. Unobserved frequencies in the d0 and d9 species are predicted. The out-of-plane skeletal bending mode is expected to lie between 170 and 200 cm(-1). Unscaled SiH3 torsional frequencies vary from 64 cm(-1) upwards. The effect of the presence of three internal rotors on the spectra throughout calls for theoretical study.     

Infrared studies of group IIB metal complexes with some imidazole derivatives

The complexes formed by zinc(II), cadmium(II) and mercury(II) halides and perchlorates with N-ethylimidazole and N-propylimidazole have been prepared and characterized by molecular conductance and i.r. spectral data down to 100 cm⁻¹. On the basis of the assignments of the metal—halogen and the metal—ligand vibrations, the stereochemistry of the compounds was inferred.     

Electron impact and molecular dissociation. Part XIX. Mass spectral studies of some binuclear metal complexes

The spectra of certain deuteriated binuclear chromium complexes have been obtained which help to elucidate some of the fragmentation processes of the molecular ion. The effect of the relative strengths of the metal-ligand and metal nitrosyl bonds is also discussed.     

Infrared spectroscopy studies of cation effects on lipopolysaccharides in aqueous solution

The conformation of amphiphilic lipopolysaccharides (LPS) influences the behavior of free and cell-bound LPS in aqueous environments, including their adhesion to surfaces. Conformational changes in Pseudomonas aeruginosa serotype 10 LPS aggregates resulting from changes in solution pH (3, 6, and 9), ionic strength [I] 1, 10, and 100 mmol L⁻¹, and electrolyte composition (NaCl and CaCl₂) were investigated via attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy. ATR-FTIR data indicate that LPS forms more stable aggregates in NaCl relative to CaCl₂ solutions. Time- and cation-dependent changes in ATR-FTIR data suggest that LPS aggregates are perturbed by Ca²⁺ complexation at lipid A phosphoryl groups, which leads to reorientation of the lipid A at the surface of a ZnSe ATR internal reflection element (IRE). Polarized ATR-FTIR investigations reveal orientation of LPS dipoles approximately perpendicular to the IRE plane for both Na- and Ca-LPS. The results indicate that changes in solution chemistry strongly impact the conformation, intermolecular and interfacial behavior of LPS in aqueous systems.     

Mass spectrometric studies of alkali metal ion binding on thrombin-binding aptamer DNA

The binding sites and consecutive binding constants of alkali metal ions, (M⁺ = Na⁺, K⁺, Rb⁺, and Cs⁺), to thrombin-binding aptamer (TBA) DNA were studied by Fourier-transform ion cyclotron resonance spectrometry. TBA-metal complexes were produced by electrospray ionization (ESI) and the ions of interest were mass-selected for further characterization. The structural motif of TBA in an ESI solution was checked by circular dichroism. The metal-binding constants and sites were determined by the titration method and infrared multiphoton dissociation (IRMPD), respectively. The binding constant of potassium is 5–8 times greater than those of other alkali metal ions, and the potassium binding site is different from other metal binding sites. In the 1:1 TBA-metal complex, potassium is coordinated between the bottom G-quartet and two adjacent TT loops of TBA. In the 1:2 TBA—metal complex, the second potassium ion binds at the TGT loop of TBA, which is in line with the antiparallel G-quadruplex structure of TBA. On the other hand, other alkali metal ions bind at the lateral TGT loop in both 1:1 and 1:2 complexes, presumably due to the formation of ion-pair adducts. IRMPD studies of the binding sites in combination with measurements of the consecutive binding constants help elucidate the binding modes of alkali metal ions on DNA aptamer at the molecular level.     

Infrared and laser Raman spectral studies of bis(dl-aspartic acid) sulfate

The infrared and Raman spectra of bis(dl-aspartic acid) sulfate in the crystalline state are recorded at room temperature and the vibrational assignments of the observed wavenumbers are made. The presence of two carbonyl (CO) groups has been identified in the title complex and the two carbonyl groups are in different environment. The extensive intermolecular hydrogen bonding in the crystal has been identified by the shifting of bands due to the stretching and bending modes of the various functional groups. The sulfate group forms the anion. Its fundamentals continue to be degenerate except for the asymmetric bending mode and it suggests that the T(d) symmetry of SO(4)(2-) group has not been affected in the crystal.     

Infrared spectral signatures of CDCP1-induced effects in colon carcinoma cells

Metastasis is the major cause of death by cancer. Indeed, metastatic colonies can reactivate and become life threatening, sometimes months or years after the initial diagnosis and surgery of the primary tumor. Therefore, there is a crucial need to develop methods for diagnosis of tumor cells that exhibit high metastatic potential. Here, we addressed the capability of vibrational spectroscopy for investigating the effects induced by CDCP1 expression in colon carcinoma cells. This transmembrane protein has been suggested to play a key role in metastasis by its pleiotropic function. We focused on a cellular model constituted by the cell lines SW480 and SW620 derived respectively from the primary tumor and a lymph node metastasis of the same patient. Induced CDCP1 expression in SW480 led to marked changes in cell morphology. Whereas SW480 form a cell layer, the SW480/CDCP1 cells exhibited reduced cell-to-cell contact. On collagen I, SW480 was more spread and filopodia were observed. In contrast, SW480/CDCP1 cells exhibited lower spreading with no formation of filopodia. Synchrotron Fourier transform infrared microspectroscopy experiments were performed on this cellular model. High quality spectroscopic information at sub-cellular resolution, provided by the use of the synchrotron source in infrared microspectroscopy, was recorded on numerous individual cells. Multivariate analysis of spectra recorded using principal component analysis indicated a highest intensity increase of the 970 and 1080 cm(-1) bands, and a modest intensity increase of the 1240 cm(-1) band in the SW480/CDCP1 cells. These bands were correlated with an increased content of phosphorylated proteins as confirmed by in situ labelling using a monoclonal antibody directed against phosphorylated tyrosines. Altogether, these results demonstrate that the vibrational technique used in this study exhibits the capability to characterize spectral signatures of CDCP1-induced effects in colon carcinoma cells. This study may open new avenues for rapid diagnosis of cells with a metastatic potential.     

Electronic spectral studies of solvent effects on the charge-transfer complex of ethylene thiourea-iodine system

The study of the ethylene thiourea-iodine charge-transfer complex in various solvents like CH₂Cl₂, CHCl₃, CHCl₃:CCl₄ solvent mixtures and 1,2-dichloroethane reveals a good correlation for the equilibrium constants and other thermodynamic quantities with the extinction coefficients in various chlorinated methane solvents.     

Electronic spectral studies and solvent effects on the reaction of iodine with 1,4,8,11-tetraazacyclotetradecane

The reaction between iodine and 1,4,8,11-tetraazacyclotetradecane (TACTD) is studied photometrically in various solvents like CCl₄, CHCl₃, CH₂Cl₂ and 1,2-dichloroethane. The results reveal that in each solvent the (TACTD):I₂ ratio is 1:2 and the iodine complex is formulated as (TACTD)I⁺·I₃⁻. The obtained values of the formation constant (K), extinction coefficient (ε) and oscillator strength (ƒ) for the iodine complex are shown to be strongly dependent on the polarity of the solvent. A linear correlation is obtained between either (ƒ) or (ε) and the dielectric constant (D) of the solvent. The important role of the solvent is mainly suggested to be due to the interaction of the ionic iodine complex with the solvent.