Potentiometric studies on the complexation equilibria between some trivalent lanthanide metal ions and biologically active 2-hydroxy-1-naphthaldehyde thiosemicarbazone (HNATS)

Summary The chelation behaviour of some trivalent lanthanide and yttrium metal ion with biologically active 2-hydroxy-1-naphthaldehyde thiosemicarbazone (HNATS) has been investigated by potentiomotric measurements at 20±0.5°C in 75% (v/v) dioxane-water medium at various ionic strengths of sodium perchlorate. The method of Bjerrum and Calvin, as modified by Irving and Rossotti has been used to find out the values of (average number of ligand bound per metal ion) andpL (free ligand exponent). The formation constants of metal chelates have been computed on a PC-XT computer, using a program patterned after that of Sullivan et al. to give _n values using weighted least squares method. TheS _min values (S _min =²) have been calculated. The order of formation constants of chelates was found to be: La³⁺3+3+3+3+3+3+3+3+3+. The formation constants of the chelates formed have been correlated to size and ionization potentials of the metal ions.

---

Potentiometrische Untersuchungen der Komplexierungsgleichgewichte zwischen einigen trivalenten Metallionen und biologisch aktivem 2-Hydroxy-1-naphthaldehyd-thiosemicarbazon (HNATS)

Zusammenfassung Es wurde das Chelierungsverhalten einiger trivalenter Lanthanidenionen mit biologisch aktivem 2-Hydroxy-1-naphthaldehyd-thiosemicarbazon (HNATS) mittels potentiometrischer Messungen bei 20±0.5°C in 75% (v/v) Dioxan-Wasser bei verschiedener Ionenstärke an Natriumperchlorat untersucht. Die Methode nach Bjerrum und Calvin in der Modifikation nach Irving und Rossotti wurde zur Ermittlung der Werte (mittlere Anzahl an Liganden pro Metallion) undpL (Exponent an freiem Liganden) verwendet. Die Komplexbildungskonstanten wurden in Anlehnung an Sullivan et al. an einem PC-XT Computer errechnet. DieS _min-Werte (S _min=²) wurden ebenfalls bestimmt. Die Reihung der Chelatbildungskonstanten war: La³⁺3+3+3+3+3+3+3+3+3+. Die Bildungskonstanten sind mit der Größe und dem Ionisierungspotential der Metallionen zu korrelieren.

     

On the occurrence and role of SnO2, SnS and FeSn2 in coal hydroliquefaction experiments using tin-based catalysts

Mössbauer Spectroscopy, X-Ray Diffraction and Electron Microscopy were applied to the study of solid residues of coal hydroliquefaction, for which tin-based catalysts were used. In the general case hydroliquefaction runs were performed in the presence of added sulphur and of finely dispersed SnO₂ as a catalyst precursor. The only observed tin species were SnO₂ and SnS, the former with percentages higher than expected from XRD, due to its large f factor, the latter as a symmetric doublet, which suggests that any asymmetry should be ascribed to small particle sizes rather than to structure. When the S content was only that of coal and the catalyst precursor β-Sn, FeSn₂ occurred together with Sn sulfides and oxides, while no β-Sn was detected. The main catalytic role is ascribed to SnS.     

Adsorption Equilibrium and Kinetics of Egg-White Proteins on Immobilized Metal Ion Affinity Gels for Designing Fractionation

Designing an Immobilized Metal ion Affinity (IMA) chromatographic process on large scale demands a thorough understanding to be developed regarding the adsorption behaviour of proteins on metal loaded IMA (IMA-M(II)) gels and the characteristic adsorption parameters to be evaluated. This research investigation illustrates the significance of these aspects for the proposed fractionation of chicken egg-white proteins on these gels. Consequently, a systematic investigation of the adsorption characteristics of three chicken egg-white proteins viz., ovalbumin, conalbumin and lysozyme on Cu(II) and Ni(II) loaded IMA gels, iminodiacetate (IDA) and tris(2-aminoethyl)amine (TREN), has been undertaken. These gels differ in their selectivity towards the proteins of interest under the identical sets of experimental conditions. While TREN-Ni(II) was selective only for lysozyme, IDA-Cu(II), IDA-Ni(II) and TREN-Cu(II) showed varying affinities for all the three proteins. The equilibrium and kinetic data were analysed using various theoretical models and adsorption parameters were quantified. On the basis of these investigations, various strategies have been proposed for the efficient large-scale fractionation of chicken egg-white proteins on these gels.     

INDUCIBLE POSTREPLICATION REPAIR IS RESPONSIBLE FOR MINIMAL MEDIUM RECOVERY IN UV-IRRADIATED Escherichia coliK–12

Abstract— Ultraviolet (UV)-irradiated Escherichia coli K–12 uvrA cells showed higher survival if plated on minimal growth medium rather than on rich growth medium, i.e., they showed minimal medium recovery (MMR). A 2-hour treatment of UV-irradiated cells with rifampicin inhibited the subsequent expression of MMR, and produced a large reduction in survival. We have recently isolated a new mutant ( mmrA1 ) that does not show MMR. The mmrA mutation protected UV-irradiated uvrA cells from the effect of rich growth medium on survival, but not from the effect of rifampicin on survival. DNA daughter-strand gap (DSG) repair in UV-irradiated (4 J/m²) uvrA cells was inhibited to the same degree whether rich growth medium was added immediately after irradiation or after 10 min of postirradiation incubation in minimal growth medium. However, chloramphenicol added immediately after irradiation greatly reduced this repair; there was less reduction if it was added 10 min after UV irradiation. These findings suggest that MMR is an inducible repair phenomenon, and that rich growth medium inhibits this repair process itself rather than its induction.     

Temperature dependence of near-resonant vibration ↔ rotation energy transfer

V ? R,T deactivation of the ν₄ (243 cm^?1) level in BCl₃ by HCl has been measured over the range 220–340 K, with an infrared double resonance technique. The deactivation probabilities show an inverse temperature dependence below room temperature, indicating that long-range attractive forces are important in the resonant transfer process. The results are compared with the theory of Sharma and Brau.     

The process\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma as an alternative to\pi ^0 \to v\bar v

The process \(\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma \) is investigated as an alternative to \(\pi ^0 \to v\bar v\) . It is shown that the experimental bound on the branching fraction for missing energy (in the form of \(\lambda _\gamma \bar \lambda _\gamma \) and/or \(v\bar v\) ) may be understood in terms of \(\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma \) for the kinematically allowed photino mass, if the squark mass is >8 GeV.     

Can a single oxidant with two spin states masquerade as two different oxidants? A study of the sulfoxidation mechanism by cytochrome p450

Density functional calculations were performed on the sulfoxidation reaction by a model compound I (Cpd I) of cytochrome P450. By contrast to previous alkane hydroxylation studies, which exhibit a dominant low-spin (LS) pathway, the sulfoxidation follows a dominant high-spin (HS) reaction. Thus, competing hydroxylation and sulfoxidation processes as observed for instance by Jones et al. (Volz, T. J.; Rock, D. A.; Jones, J. P. J. Am. Chem. Soc. 2002, 124, 9724) are the result of a two-state reactivity scenario, whereby the hydroxylation originates from the LS pathway and the sulfoxidation from the HS pathway. In this manner, two spin states of a single oxidant (Cpd I) can be disguised as two different oxidants. The calculations rule out the possibility that a second oxidant (the ferric peroxide, Cpd 0 species) interferes in the observed results of Jones et al.     

Differentiation of Boc- alpha,beta- and beta,alpha-peptides and a pair of diastereomeric beta,alpha-dipeptides by positive and negative ion electrospray tandem mass spectrometry (ESI-MS/MS)

Positive and negative ion electrospray ionization (ESI) tandem mass spectral study of a new series of hybrid peptides, viz, BocN-alpha,beta-peptides and BocN-beta,alpha-peptides, synthesized from C-linked carbo-beta3-amino acids [Caa (S)] and L-Ala has been carried out. The alpha,beta-peptides have been differentiated from beta,alpha-peptides by the collision-induced dissociation (CID) of [M + H]+ and [M - H]- ions in positive and negative ion ESI-MS respectively. The fragment ion [M + H - C(CH3)3 + H]+ formed from [M + H]+ ions by the loss of 2-methyl-prop-2-ene in alpha,beta-peptides with L-Ala at the N-terminus is insignificant or totally absent for beta,alpha-peptides which have the Caa (S) at N-terminus. The fragment ion [M - H-C(CH3)3OH - HNCO]- formed from [M - H]- of beta,alpha-peptide acids is totally absent for alpha,beta-peptide acids. This has been attributed to the absence of the beta-methylene group in alpha,beta-peptides, and the participation of the beta-methylene group in the loss of HNCO in beta,alpha-peptide acids is confirmed by the deuteration experiments. The CID of [M + H-Boc + H]+ ions of these peptides also produce characteristic fragmentation. In the CID spectra of alpha,beta-peptides, the b(n)+ ions and the resulting y(n)+ ions occur at a mass difference of 243 and 71 Da corresponding to the successive losses of Caa and L-Ala, whereas a mass difference of 71 and 243 Da is observed for beta,alpha-peptides. In contrast to the CID of protonated peptides, the CID of [M - H]- ions of the alpha,beta- and beta,alpha-peptide acids do not give b(n)- ions and show abundant z(n) (-) ions. Further, a pair of diastereomeric dipeptide esters and acids have been distinguished by the CID of [M + H]+ ions. The loss of 2-methyl-prop-2-ene is more pronounced for Boc-NH-Caa(R)-D-Ala-OCH3 (21) and Boc-NH-Caa(R)-D-Ala-OH (23) with Caa (R) at the N-terminus, whereas it is totally absent for Boc-NH-Caa (S)-D-Ala-OCH3 (22) and Boc-NH-Caa(S)-D-Ala-OH (24) peptides, which have Caa (S) at the N-terminus. Thus, on the basis of our previous and present studies, we propose that the CID of [M + H]+ ions provides a simple and useful method for distinguishing the configuration of Caa (S or R) at the N-terminus of BocN-carbo beta,alpha- and beta,beta-dipeptides.