Complexation Equilibria of Zn(II), Pb(II) and Cd(II) with Reduced Glutathione (GSH) and Biologically Important Zwitterionic Buffers

The interaction of zinc(II), lead(II), and cadmium(II) with Glutathione (S‐L‐glutamyl‐Lcysteinylglycine) as primary ligand and zwitterionic buffers (N‐[2‐Hydroxyethyl]piperazine‐N′‐[2‐ethanesulfonic acid]) (HEPES) and (N‐Hydroxyethyl]piperazine‐N′‐[2‐hydroxy‐propanesulfonic acid]) (HEPPSO) as secondary ligands were studied by potentiometric‐pH titration in 1:1:1 ratio at 25.0 °C and I = 0.1 mol.dm^?3 (KNO₃). The formation constants of different normal and protonated binary and ternary complex species were calculated. Formation constants for the monohydroxy, and dihydroxy complexes for the binary systems M(II) + HEPES and M(II) + HEPPSO have been evaluated. The distribution curves for the various complex species as a function of pH were constructed.     

Structure-dependent photophysical properties of singlet and triplet metal-to-ligand charge transfer states in copper(I) bis(diimine) compounds

The photophysical properties of singlet and triplet metal-to-ligand charge transfer (MLCT) states of [Cu(I)(diimine)(2)](+), where diimine is 2,9-dimethyl-1,10-phenanthroline (dmphen), 2,9-dibutyl-1,10-phenanthroline (dbphen), or 6,6'-dimethyl-2,2'-bipyridine (dmbpy), were studied. On 400 nm laser excitation of [Cu(dmphen)(2)](+) in CH(2)Cl(2) solution, prompt (1)MLCT fluorescence with a quantum yield of (2.8 +/- 0.8) x 10(-5) was observed using a picosecond time-correlated single photon counting technique. The quantum yield was dependent on the excitation wavelength, suggesting that relaxation of the Franck-Condon state to the lowest (1)MLCT competes with rapid intersystem crossing (ISC). The fluorescence lifetime of the copper(I) compound was 13-16 ps, unexpectedly long despite a large spin-orbit coupling constant of 3d electrons in copper (829 cm(-1) ). Quantum chemical calculations using a density functional theory revealed that the structure of the lowest (1)MLCT in [Cu(dmphen)(2)](+) (1(1)B(1)) was flattened due to the Jahn-Teller effect in 3d(9) electronic configuration, and the dihedral angle between the two phenanthroline planes (dha) was about 75 degrees with the dha around 90 degrees in the ground state. Intramolecular reorganization energy for the radiative transition of 1(1)B(1) was calculated as 2.1 x 10(3) cm(-1), which is responsible for the large Stokes shift of the fluorescence observed (5.4 x 10(3) cm(-1)). To understand the sluggishness of the intersystem crossing (ISC) of (1)MLCT of the copper(I) compounds, the strength of the spin-orbit interaction between the lowest (1)MLCT (1(1)B(1)) and all (3)MLCT states was calculated. The ISC channels induced by strong spin-orbit interactions (ca. 300 cm(-1)) between the metal-centered HOMO and HOMO - 1 were shown to be energetically unfavorable in the copper(I) compounds because the flattening distortion caused large splitting (6.9 x 10(3) cm(-1)) between these orbitals. The possible ISC is therefore induced by weak spin-orbit interactions (ca. 30 cm(-1)) between ligand-centered molecular orbitals. Further quantum mechanical study on the spin-orbit interaction between the lowest (3)MLCT (1(3)A) and all (1)MLCT states indicated that the phosphorescence borrows intensity from 2(1)B(1). The radiative rate of the phosphorescence was also structure-sensitive. The flattening distortion reduced the transition dipole moment of 2(1)B(1) --> the ground state, and decreased the extent of mixing between 1(3)A and 2(1)B(1), thereby considerably reducing the phosphorescence radiative rate at the MLCT geometry compared to that at the ground state geometry. The theoretical calculation satisfactorily reproduced the radiative rate of ca. 10(3) s(-1) and accounted for the structure-sensitive phosphorescence intensities of copper(I) bis(diimine) compounds recently demonstrated by Felder et al. (Felder, D.; Nierengarten, J. F.; Barigelletti, F.; Ventura, B.; Armaroli, N. J. Am. Chem. Soc. 2001, 123, 6291).     

Hexa­methyl­enetetra­mine–4‐nitro­catechol–water (1/2/1)

In the title adduct, 1,3,5,7‐tetra­aza­tri­cyclo[3.3.1.1^3,7]dec­ane–4‐nitro­benzene‐1,2‐diol–water (1/2/1), C₆H₁₂N₄·2C₆H₅NO₄·H₂O, the hexa­methyl­ene­tetra­mine mol­ecule acts as an acceptor of intermolecular O—H?N hydrogen‐bonding interactions from the water mol­ecule and the hydroxy groups of one of the two symmetry‐independent 4‐nitro­catechol mol­ecules. The structure is built from molecular layers which are stabilized by three intermolecular O—H?O, two intermolecular O—H?N and four intermolecular C—H?O hydrogen bonds. The layers are further interconnected by one additional intermolecular O—H?N and two intermolecular C—H?O hydrogen bonds.     

1‐Acetyl‐3‐[1‐(4‐methoxyphenyl)‐2‐oxopropylidene]‐1H‐indol‐2(3H)‐one: a twinned crystal

The crystal of the title compound, C₂₀H₁₇NO₄, which was used for collecting intensity data was twinned. Each of the two crystallographically independent mol­ecules in the asymmetric unit has a planar indole moiety perpendicular to a planar oxo­propyl moiety. The distribution of the bonds at the central C atom joining the oxo­propyl, phenyl and indole substituents is also planar. The packing is stabilized by intermolecular C—H?O interactions, as well as by dipole–dipole and van der Waals interactions.     

Bis­[hydrogen 1,1′‐bis­(di­phenyl­phos­phinato)­ferrocenium] octa­chloro­diantimony(III)

In the title compound, [Fe(C₃₄H₂₉O₂P₂)]₂[Sb₂Cl₈], the discrete centrosymmetric [Sb₂Cl₈]^2? anions are formed from two edge‐shared square pyramids of Cl atoms about each Sb atom. Within the cation, the two di­phenyl­phosphinate groups share one H atom and the ferrocene cyclo­penta­dienyl rings are in a staggered conformation, with the average value of the twist angle being 46°. In the crystal, each [Sb₂Cl₈]^2? anion is involved in eight C—H?Cl interactions with four surrounding cations and these interactions interconnect the ions to form molecular columns along the a direction.     

Resolution of crystalline ribonuclease by paper electrophoresis

1. Crystalline ribonuclease samples obtained from different commercial sources in addition to one prepared in the laboratory were resolved into their components, RNases I, II, III and IV, by a new two-dimensional electrophoretic technique 2. RNase I and RNase II liberated more uridyhc acid and cytidylic acid from yeast nbonucleic acid, and demonstrated a greater enzymic activity on undine-2', 3'-phosphate and cytidine-2',3'-phosphate, than either RNase III or RNase IV RNase III and RNaso IV liberated more adenylic acid and guanylic acid from yeast ribonucleic acid, and showed a greater enzymic activity on adenosine-2',3'-phosphate and guanosine-2', 3 '-phosphate than cither RNase I and RNase II 3. The degree of heterogeneity of the RNase samples studied revealed the age of the preparation 4. It is thus demonstrated, that certain of the activities of “crystalline nbonucleasc” reside in four different protein entities, and some activity toward punne nucleotidc esters existed in two of the four protein entities     

Synthesis of substituted salicylamines and dihydro-2H-1,3-benzoxazines

Phenols were converted to their magnesium salts with the MgCl₂-Et₃N base system and subsequently reacted with Eschenmoser's salt, affording N,N-dimethyl substituted benzylamines in high to excellent yields. A series of mono N-substituted benzylamines were prepared in one-pot syntheses by ortho-formylation of phenols to corresponding salicylaldehydes, which in turn reacted with amines to imines. The imines were subsequently reduced to mono N-substituted benzylamines. Some of these benzylamines were further converted, without work-up, to mono N-substituted dihydro-2H-1,3-benzoxazines.     

Phytochemistry of Daphne oleoides

Genus Daphne belongs to the Thymelaeaceae family and consists of 70 species. Its various species exist in Europe, Philippine Islands, temperate and subtropical Asia, North Africa, Australia and Pacific. In Pakistan, Daphne is represented by three species. Our focused Daphne oleoides is widely found in diverse climatic conditions from northern cold to central hot regions which creates a rich diversity and novelty in biosynthetic levels of its chemical constituents and hence is a great opportunity. Daphne oeloides is a proven rich source of a variety of unique and interesting nature-made skeletons with a wide range of therapeutic properties. D. oleoides possesses effective therapeutic properties, therefore, has been used in herbal medicines and is still being used to treat various diseases. The modern research by various groups, including ourselves, has resulted in the isolation of a number of natural molecules including some novel tris- and bis- coumarins, daphnane diterpenoids and lignoids. Therefore, due to novelty and richness of the nature-made molecules, and their therapeutic potential combined with our significant work on D. oleoides, this report covers chemical constituents isolated from D. oleoides. The pharmacological activities of the isolated compounds and use of this species in folk medicine have also been reviewed.     

Optical diagnosis of dengue virus infected human blood using Mueller matrix polarimetry

Currently dengue fever diagnosis methods include capture ELISAs, immunofluorescence tests, and hemagglutination assays. In this study optical diagnosis of dengue virus infection in the whole blood is presented utilizing Mueller matrix polarimetry. Mueller matrices of about 50 dengue viral infected and 25 non-dengue healthy blood samples were recorded utilizing light source from 500 to 700 nm with scanning step of 10 nm. Polar decomposition of the Mueller matrices for all the blood samples was performed that yielded polarization properties including depolarization, diattenuation, degree of polarization, retardance and optical activity, out of which, depolarization index clusters up the diseased and healthy in to different separate groups. The average depolarized light in the case of dengue infection in the whole blood at 500 nm is 18%, whereas for the healthy blood samples it is 13.5%. This suggests that depolarization index of polarized light at the wavelengths of 500, 510, 520, 530 and 540 nm, we find that in case of depolarization index values are higher for dengue viral infection as compared to normal samples. This technique can effectively be used for the characterization of the dengue virus infected at an early stage of disease.     

The green synthesis of fine particles of gold using an aqueous extract of <Emphasis Type="Italic">Monotheca buxifolia</Emphasis> (Flac.)

This study deals with the synthesis and physicochemical investigation of gold nanoparticles using an aqueous extract of Monotheca buxifolia (Flac.). On the treatment of aqueous solution of tetrachloroauric acid with the plant extract, gold nanoparticles were rapidly fabricated. The synthesized particles were characterized by UV–Vis spectrophotometry (UV), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX) and Scanning electron microscopy (SEM). The formation of AuNPs was confirmed by noting the change in color through visual observations as well as via UV–Vis spectroscopy. UV?Vis spectrum of the aqueous medium containing gold nanoparticles showed an absorption peak at around 540 nm. FTIR was used to identify the chemical composition of gold nanoparticles and Au-capped plant extract. The presence of elemental gold was also confirmed through EDX analysis. SEM analysis of the gold nanoparticles showed that they have a uniform spherical shape with an average size in the range of 70–78 nm. This green system showed to be better capping and stabilizing agent for the fine particles. Further, the antioxidant activity of Monotheca buxifolia (Flac.) extract and Au-capped with the plant extract was also evaluated using FeCl₃/K₃[Fe(CN)]₆ in vitro assay.