125Te Mössbauer spectra of the intercalation compound (Te2)2(I2)

The quadrupole split asymmetric ¹²⁵Te Mössbauer spectrum recorded from the compound (Te₂)₂(I₂), in which monomolecular planar layers of iodine molecules are intercalated between layers of tellurium, is a reflection of the distorted environment of tellurium atoms in a two-dimensional layered compound in which the elongated flat crystals are preferentially orientated. The differences between the Mössbauer parameters recorded from (Te₂)₂(I₂) and those recorded from elemental tellurium and the tellurium(0) species in the compound Te₃Cl₂ are associated with small differences between the environments of tellurium in the three compounds. The Mössbauer spectra recorded from (Te₂)₂(I₂) are consistent with a recently proposed model on which the electronic band structure of (Te₂)₂(I₂) has been derived.     

Resonance Raman studies of the peroxotitanate(IV) complexes K2(Ti(O2)(SO4)2)·5H2O and K2(Ti(O2)(C2O4)2)·3H2O

The resonance Raman spectra of K₂(Ti(O₂)(SO₄)₂)·5H₂O and K₂(Ti(O₂)(C₂O₄)₂)·3H₂O are recorded. The results are consistent with the triangular structure of the peroxotitanium unit, Ti(O₂), with C_2ν symmetry. The ν(OO), ν_s(TiO) and ν_as(TiO) are observed around 890, 610 and 535 cm⁻¹, respectively. The resonance effects are shown to be associated with the 425 nm absorption band. This band is assigned to the O₂²⁻ → Ti(IV) charge-transfer transition. The calculated force constant values for the O₂²⁻ and TiO bonds are 320 and 275 N m⁻¹, respectively.     

Combination of Azidothymidine (AZT) and (E)-5-(2-Bromovinyl)-2′-deoxyuridine (BVDU) Inhibits the Replication of Herpes Simplex Virus Type 1 (HSV-1) and Type 2 (HSV-2) and Varicella Zoster Virus (VZV) Strains That Are Deficient in the Expression of the Viral Thymidine Kinase (tk)

Abstract

Combinations of high concentrations of AZT with BVDU, acyclovir (ACV) or ganciclovir (GCV) show antagonism against TK⁺ HSV-1, but not TK⁺ VZV strains, in cell cultures. When BVDU and AZT were used in combination against TK^? HSV-1, TK^? HSV-2 and TK^? VZV strains, a pronounced inhibition of viral replication was observed. This potentiating effect was not seen if AZT was combined with ACV or GCV.     

Partial structure of the human α2(IV) collagen chain and chromosomal localization of the gene (COL4A2)

Summary We have isolated a 2.1-kb cDNA clone from a human placental library encoding part of the 2 chain of collagen IV, a major structural protein of basement membranes. The DNA sequence encodes 446 amino acids in the triplehelical domain plus the 227 amino acids of the carboxy-terminal globular domain. The latter structure is composed of two homologous subdomains and is highly conserved between the 1 and 2 chains. The triple-helical domain contained seven interruptions of the Gly-X-Y repeat and these interruptions were in general larger than their counterparts in the 1 chain. DNA from human rodent hybrid cell lines was analyzed under conditions in which there was no cross-hybridization of the 2(IV) cDNA probe with the gene for the 1(IV) collagen chain. An Eco RI fragment characteristic of the 2 chain had a concordance of 0.97 with chromosome 13. This result was confirmed and extended with in situ localization of the gene at 13q34. Since the 1(IV) gene has previously been localized to 13q34, the two type IV collagen genes reside in the same chromosome region (13q34), possibly in a gene cluster. The presence of the genes for type IV collagen chains on chromosome 13 excludes a primary role for these genes in adult polycystic kidney disease and X-linked forms of hereditary nephritis.     

Characterization of the Distal Polyadenylation Site of the ?-Adducin (Add2) Pre-mRNA

Most genes have multiple polyadenylation sites (PAS), which are often selected in a tissue-specific manner, altering protein products and affecting mRNA stability, subcellular localization and/or translability. Here we studied the polyadenylation mechanisms associated to the beta-adducin gene (Add2). We have previously shown that the Add2 gene has a very tight regulation of alternative polyadenylation, using proximal PAS in erythroid tissues, and a distal one in brain. Using chimeric minigenes and cell transfections we identified the core elements responsible for polyadenylation at the distal PAS. Deletion of either the hexanucleotide motif (Hm) or the downstream element (DSE) resulted in reduction of mature mRNA levels and activation of cryptic PAS, suggesting an important role for the DSE in polyadenylation of the distal Add2 PAS. Point mutation of the UG repeats present in the DSE, located immediately after the cleavage site, resulted in a reduction of processed mRNA and in the activation of the same cryptic site. RNA-EMSA showed that this region is active in forming RNA-protein complexes. Competition experiments showed that RNA lacking the DSE was not able to compete the RNA-protein complexes, supporting the hypothesis of an essential important role for the DSE. Next, using a RNA-pull down approach we identified some of the proteins bound to the DSE. Among these proteins we found PTB, TDP-43, FBP1 and FBP2, nucleolin, RNA helicase A and vigilin. All these proteins have a role in RNA metabolism, but only PTB has a reported function in polyadenylation. Additional experiments are needed to determine the precise functional role of these proteins in Add2 polyadenylation.     

Recent reports about enzymes related to the synthesis of prostaglandin (PG) F(2) (PGF(2α) and 9α, 11β-PGF(2))

Prostaglandin (PG) F(2α) is widely distributed in various organs and exhibits various biological functions, such as luteolysis, parturition, aqueous humor homeostasis, vasoconstriction, rennin secretion, pulmonary fibrosis and so on. The first enzyme reported to synthesize PGF(2) was referred to as PGF synthase belonging to the aldo-keto reductase (AKR) 1C family, and later PGF(2α) synthases were isolated from protozoans and designated as members of the AKR5A family. In 2003, AKR1B5, which is highly expressed in bovine endometrium, was reported to have PGF(2α) synthase activity, and recently, the paper entitled 'Prostaglandin F(2α) synthase activities of AKR 1B1, 1B3 and 1B7' was reported by Kabututu et al. (J. Biochem.145, 161-168, 2009). Clones that had already been registered in a database as aldose reductases (AKR1B1, 1B3, and 1B7) were expressed in Escherichia coli, and these enzymes were found to have PGF(2α) synthase activity. Moreover, in the above-cited article, the effects of inhibitors specific for aldose reductase on the PGF(2α) synthase activity of AKR1B were discussed. Here, I present an overview of various PGF/PGF(2α) synthases including those of AKR1B subfamily that have been reported until now.     

Synthesis of the Selenium Analog of the Cytokinin 6-(3-Methyl-2-Butenylamino)-2-Methylthio-9-(β-D-Ribofuranosyl)Purine

Abstract

6-(3-methyl-2-butenylamino)-2-methylthio-9-(β-D-ribofuranosyl)purine (1) is a naturally occurring nucleoside with potent cytokinin activity. It has been isolated and identified in the t-RNA of E. coli,^1,2 the t-RNA from wheat germ^3,4 and from Staphylococcus epidermidis.⁵ In addition, compound 1 has been found in t-RNA species corresponding to each of six amino acids whose codons start with uridine, i.e., t-RNA^Cys     

Emission polarization study of the interaction of stellacyanin with tris(2, 2′-bipyridine)osmium(II)

The association of Os(bpy)₃²⁺ and stellacyanin was investigated by measuring the emission polarization of the excited state of the complex [*Os-(bpy)₃²⁺]. At high protein concentration (≥1 mM) Os(bpy)₃²⁺ appears to bind weakly to reduced stellacyanin and to oxidized stellacyanin to a lesser extent. These results are consistent with those obtained in a previous kinetic study on the redox quenching of *Ru(bpy)₃²⁺ by stellacyanin [1]. On excitation at 480 nm, the limiting polarization (P_o) of the *Os(bpy)₃²⁺ emission at 715 nm is 0.100. From P_o we concluded that (1) protein-bound Os(bpy)₃²⁺ has considerable rotational freedom independent of the protein-probe complex, and (2) the emission dipole of *Os(bpy)₃²⁺ is at ∼45° to the C₃ molecular axis.     

The α-helical content of the transmembrane domain of the British dementia protein-2 (Bri2) determines its processing by signal peptide peptidase-like 2b (SPPL2b)

Regulated intramembrane proteolysis is a widely accepted concept describing the processing of various transmembrane proteins via ectodomain shedding followed by an intramembrane cleavage. The resulting cleavage products can be involved in reverse signaling. Presenilins, which constitute the active center of the γ-secretase complex, signal peptide peptidase (SPP), and its homologues, the SPP-like (SPPL) proteases are members of the family of intramembrane-cleaving aspartyl proteases of the GXGD-type. We recently demonstrated that Bri2 (itm2b) is a substrate for regulated intramembrane proteolysis by SPPL2a and SPPL2b. Intramembrane cleavage of Bri2 is triggered by an initial shedding event catalyzed by A Disintegrin and Metalloprotease 10 (ADAM10). Additionally primary sequence determinants within the intracellular domain, the transmembrane domain and the luminal juxtamembrane domain are required for efficient cleavage of Bri2 by SPPL2b. Using mutagenesis and circular dichroism spectroscopy we now demonstrate that a high α-helical content of the Bri2 transmembrane domain (TMD) reduces cleavage efficiency of Bri2 by SPPL2b, while the presence of a GXXXG dimerization motif influences the intramembrane cleavage only to a minor extent. Surprisingly, only one of the four conserved intramembrane glycine residues significantly affects the secondary structure of the Bri2 TMD and thereby its intramembrane cleavage. Other glycine residues do not influence the α-helical content of the transmembrane domain nor its intramembrane processing.     

A Supplement to the 《Flora of Xizang》 (2)

The present paper is the Supplement 2 to the Flora of Xizang, based upon a collection in 1980 by Mr. W. L. Chen et al. from Mêdog, the south-eastern part of Xizang. In the paper 11 new species are desribed and 10 new-record species are reported. All the type specimens are kept in the Herbarium of the Institure of Botany, Academia Sinica (PE).     

Class II alcohol dehydrogenase (ADH2) — adding the structure

Class II alcohol dehydrogenase (ADH2) represents a highly divergent class of alcohol dehydrogenases predominantly found in liver. Several species variants of ADH2 have been described, and the rodent enzymes form a functionally distinct subgroup with interesting catalytic properties. First, as compared with other ADHs, the catalytic efficiency is low for this subgroup. Second, the substrate repertoire is unique, e.g. rodent ADH2s are not saturated with ethanol as substrate, and while ω-hydroxy fatty acids are common substrates for the human ADH1–ADH4 isoenzymes, including ADH2, these compounds function as inhibitors rather than substrates. The recently determined structure of mouse ADH2 reveals a novel substrate-pocket topography that accounts for the observed substrate specificity and may, therefore, be important for the exploration of orphan substrates of ADH2. It is possible to improve the catalytic efficiency of mouse ADH2 by an array of mutations at position 47. Residue Pro47 of the wild type ADH2 enzyme seems to strain the binding of coenzyme, which prevents a close approach between the coenzyme and substrate for efficient hydrogen transfer. Based on crystallographic and mechanistic investigations, the effects of residue replacements at position 47 are multiple, affecting the distance for hydride transfer, the pK_a of the bound alcohol substrate as well as the affinity for coenzyme.     

Drosophila memory: will Orb(2) predict the future?

Genetically tractable organisms with relatively simple nervous systems offer a realistic platform to understand how and where memories are formed and stored in defined neural circuits. Recent work in Drosophila provides promise that this analysis may soon reach the resolution of identifiable synapses.     

2-(2-Benzofuranyl)-2-Imidazoline Attenuates the Disruption of the Blood–Brain Barrier in EAE via NMDAR

Blood–brain barrier (BBB) disruption has been recognized as an early hallmark of multiple sclerosis (MS) pathology. Our previous studies have shown that 2-(2-Benzofuranyl)-2-imidazoline (2-BFI) protected against experimental autoimmune encephalomyelitis (EAE), a classic animal model of MS. However, the potential effects of 2-BFI on BBB permeability have not yet been evaluated in the context of EAE. Herein, we aimed to investigate the effect of 2-BFI on BBB permeability in both an animal model and an in vitro BBB model using TNF-α to imitate the inflammatory damage to the BBB in MS. In the animal model, 2-BFI reduced neurological deficits and BBB permeability in EAE mice compared with saline treatment. The Western blot results indicated that 2-BFI not only alleviated the loss of the tight junction protein occludin caused by EAE but also inhibited the activation of the NR1-ERK signaling pathway. In an in vitro BBB model, 2-BFI (100 μM) alleviated the TNF-α-induced increase in permeability and reduction in expression of occludin in monolayer bEnd.3 cells. Similar protective effects were also observed after treatment with the NMDAR antagonist MK801. The Western blot results showed that the TNF-α-induced BBB breakdown and increase in NMDAR subunit 1 (NR1) levels and ERK phosphorylation could be blocked by pretreatment with 2-BFI or MK801. However, no additional effect was observed on BBB permeability or the expression of occludin and p-ERK after pretreatment with both 2-BFI and MK801. Our study indicates that 2-BFI alleviates the disruption of BBB in the context of inflammatory injury similar to that of MS by targeting NMDAR1, as well as by likely activating the subsequent ERK signaling pathway. These results provide further evidence for 2-BFI as a potential drug for the treatment of MS.

     

Theoretical study of the hydroxylation of phenolates by the Cu2O2(N,N′-dimethylethylenediamine)2 2+ complex

Tyrosinase catalyzes the ortho hydroxylation of monophenols and the subsequent oxidation of the diphenolic products to the resulting quinones. In efforts to create biomimetic copper complexes that can oxidize C–H bonds, Stack and coworkers recently reported a synthetic μ-η²:η²-peroxodicopper(II)(DBED)₂ complex (DBED is N,N′-di-tert-butylethylenediamine), which rapidly hydroxylates phenolates. A reactive intermediate consistent with a bis-μ-oxo-dicopper(III)-phenolate complex, with the O–O bond fully cleaved, is observed experimentally. Overall, the evidence for sequential O–O bond cleavage and C–O bond formation in this synthetic complex suggests an alternative mechanism to the concerted or late-stage O–O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase. In this work, the reaction mechanism of this peroxodicopper(II) complex was studied with hybrid density functional methods by replacing DBED in the μ-η²:η²-peroxodicopper(II)(DBED)₂ complex by N,N′-dimethylethylenediamine ligands to reduce the computational costs. The reaction mechanism obtained is compared with the existing proposals for the catalytic ortho hydroxylation of monophenol and the subsequent oxidation of the diphenolic product to the resulting quinone with the aim of gaining some understanding about the copper-promoted oxidation processes mediated by 2:1 Cu(I)O₂-derived species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Feedback regulation of the α2(1) collagen gene via the Mek-Erk signaling pathway

The extracellular matrix (ECM) provides the microenvironment that is pivotal for cell growth, motility, attachment, and differentiation. Advances in cell culture techniques have led to the development of cell-derived ECM model systems that are more reflective of the in vivo architecture of the ECM in tissue. In this study, a fibroblast-derived ECM (fd-ECM) was used to study the feedback regulation of type I collagen synthesis in fibroblasts. Fibroblasts plated on a preformed fd-ECM showed a significant decrease in the production of type I collagen and pro-α2(1) collagen mRNA compared to cells grown in the absence of a matrix. Function-blocking antibodies showed that this downregulation of type I collagen gene expression is mediated via α2β1 integrin. The use of several kinase inhibitors and a dominant negative ras construct (N17Ras) showed that the matrix-mediated downregulation of COL1A2 occurs via Ras-dependent activation of the MEK/ERK signaling pathway. Deletion analysis of the COL1A2 promoter implicated the region between -375 and -107 as containing a potential matrix responsive element. The use of Sp1 siRNA demonstrated that Sp1 is an important mediator of this feedback inhibition. This study provides some new insights into the feedback regulation of COL1A2 gene expression.     

Binuclear rhodium carbonyl halide complexes containing the 1,1-bis(diphenylphosphino)ethene ligand,and the crystal structure of [Rh2Cl2(μ-CO){Ph2PC(CH2)PPh2}2]

Treatment of [RhCl(CO)₂]₂ with 1,1-bis(diphenylphosphino)ethene (dppee) yields the cationic binuclear rhodium complex [Rh₂(μ-Cl)(CO)₂(μ-CO)(dppee)₂]⁺ which may be isolated as the [RhCl₂(CO)₂]⁻ salt at low temperature (230 K) but which readily forms the Cl⁻ salt on allowing the solution to warm to room temperature. On bubbling nitrogen through a solution of this cationic complex at room temperature, the monocarbonyl species, [Rh₂Cl₂(μ-CO)(dppee)₂] is obtained. The crystal structure of this complex has been determined. The crystals are orthorhombic, space group Pnca, a = 29.98(3), b = 23.70(2), c = 14.78(3) Å, Z = 8. Using 3019 unique reflections the structure was refined to R = 0.091. The rhodium-rhodium distance is 2.650(14) Å. Direct rhodium NMR data are reported for these complexes.