J. Appl. Cryst.の発刊に際して

The poorly known mechanism of inhibition of cholinesterases by inorganic mercury (HgCl2) has been studied with a view to using these enzymes as biomarkers or as biological components of biosensors to survey polluted areas. The inhibition of a variety of cholinesterases by HgCl2 was investigated by kinetic studies, X-ray crystallography, and dynamic light scattering. Our results show that when a free sensitive sulfhydryl group is present in the enzyme, as in Torpedo californica acetylcholinesterase, inhibition is irreversible and follows pseudo-first-order kinetics that are completed within 1 h in the micromolar range. When the free sulfhydryl group is not sensitive to mercury (Drosophila melanogaster acetylcholinesterase and human butyrylcholinesterase) or is otherwise absent (Electrophorus electricus acetylcholinesterase), then inhibition occurs in the millimolar range. Inhibition follows a slow binding model, with successive binding of two mercury ions to the enzyme surface. Binding of mercury ions has several consequences: reversible inhibition, enzyme denaturation, and protein aggregation, protecting the enzyme from denaturation. Mercury-induced inactivation of cholinesterases is thus a rather complex process. Our results indicate that among the various cholinesterases that we have studied, only Torpedo californica acetylcholinesterase is suitable for mercury detection using biosensors, and that a careful study of cholinesterase inhibition in a species is a prerequisite before using it as a biomarker to survey mercury in the environment.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1742-4658.2007.05732.x

Mechanisms of cholinesterase inhibition by inorganic mercury.

The reactions of meso-1,2-bis(ethylsulfinyl)ethane (meso-L) with Ln(ClO4)3 [Ln(NO3)3 or Ln(NCS)3] in MeOH and CHCl3 gave a series of new lanthanide coordination polymers, {[Ln(μ-meso-L)(rac-L)2(CH3OH)2](ClO4)3}n [Ln:  La (1), Nd (2), Eu (3), Gd (4), Tb (5), Dy (6), and Yb (7)], [Yb(μ-meso-L)1.5(NO3)3]n (8), and [La(μ-meso-L)2.5(NCS)3]n (9). All the structures were established by single-crystal X-ray diffraction. Complexes 1−7 are isostructural with infinite single μ-chain structure, in which the L ligands take two kinds of coordination modes:  bidentate chelating and bis-monodentate bridging. Six sulfur atoms of the sulfoxide groups around each LnIII center adopt alternatively the same R or S configuration in the chain. In addition, the configuration change of partial ligands occurred from the meso to the rac form when reacting with Ln(ClO4)3. To our knowledge, this is the first example of disulfoxide complexes with two kinds of coordination modes and three kinds of configurations (R,R, S,S, and R,S) occu...

Novel lanthanide coordination polymers with a flexible disulfoxide ligand, 1,2-bis(ethylsulfinyl)ethane: structures, stereochemistry, and the influences of counteranions on the framework formations.

Although [Ni(S2CNBui
2)2] is stable at high temperatures in a range of solvents, solvothermal decomposition
occurs at 145 °C in oleylamine to give pure NiS nanoparticles, while in n-hexylamine at 120 °C a mixture of Ni3S4 (polydymite)
and NiS results. A combined experimental and theoretical study gives mechanistic insight into the decomposition process and
can be used to account for the observed differences. Upon dissolution in the primary amine, octahedral trans-
[Ni(S2CNBui
2)2(RNH2)2] result as shown by in situ XANES and EXAFS and confirmed by DFT calculations. Heating to
90−100 °C leads to changes consistent with the formation of amide-exchange products, [Ni(S2CNBui
2){S2CN(H)R}] and/or
[Ni{S2CN(H)R}2]. DFT modeling shows that exchange occurs via nucleophilic attack of the primary amine at the backbone
carbon of the dithiocarbamate ligand(s). With hexylamine, amide-exchange is facile and significant amounts of
[Ni{S2CN(H)Hex}2] are formed prior to decomposition, but with oleylamine, exchange is slower and [Ni(S2CNBui
2){S2CN-
(H)Oleyl}] is the active reaction component. The primary amine dithiocarbamate complexes decompose rapidly at ca. 100 °C to
afford nickel sulfides, even in the absence of primary amine, as shown from thermal decomposition studies of
[Ni{S2CN(H)Hex}2]. DFT modeling of [Ni{S2CN(H)R}2] shows that proton migration from nitrogen to sulfur leads to
formation of a dithiocarbimate (S2CNR) which loses isothiocyanate (RNCS) to give dimeric nickel thiolate complexes
[Ni{S2CN(H)R}(μ-SH)]2. These intermediates can either lose dithiocarbamate(s) or extrude further isothiocyanate to afford
(probably amine-stabilized) nickel thiolate building blocks, which aggregate to give the observed nickel sulfide nanoparticles.
Decomposition of the single or double amide-exchange products can be differentiated, and thus it is the different rates of amideexchange
that account primarily for the formation of the observed nanoparticulate nickel sulfides.

Active Nature of Primary Amines during Thermal Decomposition of Nickel Dithiocarbamates to Nickel Sulfide Nanoparticles

Nitroxides bearing an α-hydrogen decompose upon heating in a bimolecular reaction. A new mechanism is proposed for the decomposition of t-butylisopropylphenyl nitroxide (TIPNO) involving the formation of a head-to-tail dimer, single electron transfer to form an oxammonium salt, epimerization to the corresponding nitrone, and elimination to form a conjugated oxime. This mechanism may provide insights into designing new nitroxides for use in controlled polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 697–717, 2006

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pola.21207

Nitroxide decomposition: Implications toward nitroxide design for applications in living free-radical polymerization

Formation of Aryl-bis (6-Amino-1,3-Dimethyluracil-5-yl) Methanes by reaction of 6-Amino-1, 3-Dimethyluracil with Aromatic Aldehydes

In the title compound, C(29)H(36)O(2), the outer cyclohexene ring of the steroid nucleus has a conformation that lies about half-way between a half-chair and an envelope, while the central and outer cyclohexane rings of the steroid nucleus have slightly distorted chair conformations. The steroidal cyclopentane ring adopts a 13beta,14alpha-half-chair conformation. The benzylidene moiety has an E configuration with respect to the carbonyl group on the cyclopentane ring. The dihedral angle between the mean planes of the steroid nucleus and the benzylidene moiety is 35.54 (9) degrees. The packing of the molecules is assumed to be dictated mainly by weak intermolecular C-H.O interactions.

16-(4-Isopropylbenzylidene)androst-4-ene-3,17-dione.

The crystal structure of the α form of bis(N,N-diethyldithiocarbamato-S,S')nickel(II), [Ni(C 5 H 10 NS 2 ) 2 ], has been redetermined at 290 K by single-crystal X-ray methods. The Ni atom assumes a four-coordinate square-planar geometry with two isobidentate dithiocarbamate groups. The results confirm those of a previous study [Bonamico, Dessy, Mariani, Vaciago & Zambonelli (1965). Acta Cryst. 19, 619-627] but are more precise

http://journals.iucr.org/c/issues/1995/04/00/mu1109/mu1109.pdf

Redetermination of Bis(N,N-diethyldithiocarbamato)nickel(II)

The title compound, [SnCl2(C18H15OP)2] or SnCl2.2TPPO (TPPO is triphenylphosphine oxide), has been found to be a four-coordinate tin(II) complex by single-crystal X-ray diffraction analysis. The distorted axial arrangement of the two TPPO ligands and the equatorial disposition of the two chlorines around tin(II) are confirmed.

http://journals.iucr.org/c/issues/1998/07/00/vj1080/vj1080.pdf

Dichlorobis(triphenylphosphine oxide)-tin(II)

In both of the title compounds, C(23)H(19)ClN(2)O, (I), and C(23)H(18)Cl(2)N(2)O, (II), the molecular packing is influenced by weak intermolecular C-H.O and C-H.pi interactions, but despite the chemical similarity of the compounds, the packing in (II) is entirely different from that observed in (I).

/pdf/3-4-chlorobenzoyl-7-n-n-dimethylamino-1-phenylindolizine-and-29s5egubp0.pdf

V. Parthasarathi

Papers

Formation of Aryl-bis (6-Amino-1,3-Dimethyluracil-5-yl) Methanes by reaction of 6-Amino-1, 3-Dimethyluracil with Aromatic Aldehydes

16-(4-Isopropylbenzylidene)androst-4-ene-3,17-dione.

Redetermination of Bis(N,N-diethyldithiocarbamato)nickel(II)

Dichlorobis(triphenylphosphine oxide)-tin(II)

3-(4-Chlorobenzoyl)-7-(N,N-dimethylamino)-1-phenylindolizine and 3-(2,4-dichlorobenzoyl)-7-(N,N-dimethylamino)-1-phenylindolizine.