Investigation of the system cobalt(II) bovine carbonic anhydrase B-trichloroacetaldehyde.

The interactions between hydrated trichloroacetaldehyde and cobalt(II)bovine carbonic anhydrase B have been investigated as a function of pH by means of electronic spectroscopy of FT nmr spectroscopy. The hydrated aldehyde is bound to the metal ion and its apparent affinity constant is pH dependent with a bell-shaped profile. The kinetic parameters of the dissociation process have also been determined.     

Spectral characterization of vanadium-transferrin systems

The preparation procedure of vanadium(III) transferrin and its stability are confirmed to be as previously reported. The electronic spectra of vanadium(III), oxovanadium(IV), and vanadium(V) transferrin derivatives are comparatively discussed. A band in the near infrared of the oxovanadium(IV) derivative is observed for the first time.     

Burkholderia pseudomallei γ-carbonic anhydrase is strongly activated by amino acids and amines

Activation of the γ-class carbonic anhydrase (CAs, EC 4.2.1.1) from the pathogenic bacterium Burkholderia pseudomallei (BpsγCA) with a series of natural and non-natural amino acids and aromatic/heterocyclic amines has been investigated. The best BpsγCA activators were d-His, l-DOPA, d-Trp, 4-amino-l-Phe, dopamine, 2-(2-aminoethyl)pyridine, 2-aminoethyl-piparazine/morpholine and l-adrenaline, which showed activation constants ranging between 9 and 86 nM. The least effective activators were l-His, l-Phe and 2-pyridyl-methylamine, with K_As in the range of 1.73–24.7 μM. As little is known about the role of γ-CAs in the lifecycle and virulence of this saprophytic bacterium, this study may shed some light on such phenomena. This is the first CA activation study of a γ-CA from a pathogenic bacterium, the only other such study being on the enzyme discovered in the archaeon Methanosarcina thermophila, Cam.     

CXCR7 contributes to the aggressive phenotype of cholangiocarcinoma cells

Development of cholangiocarcinoma (CCA) is dependent on a cross-talk with stromal cells, which release different chemokines including CXCL12, that interacts with two different receptors, CXCR4 and CXCR7. The aim of the present study was to investigate the role of CXCR7 in CCA cells. CXCR7 is overexpressed by different CCA cell lines and in human CCA specimens. Knock-down of CXCR7 in HuCCT-1 cells reduced migration, invasion, and CXCL12-induced adhesion to collagen I. Survival of CCA was also reduced in CXCR7-silenced cells. The ability of CXCL12 to induce cell migration and survival was also blocked by CCX733, a CXCR7 antagonist. Similar effects of CXCR7 activation were observed in CCLP-1 cells and in primary iCCA cells. Enrichment of tumor stem-like cells by a 3D culture system resulted in increased CXCR7 expression compared to cells grown in monolayers, and genetic knockdown of CXCR7 robustly reduced sphere formation both in HuCCT-1 and in CCLP-1 cells. In HuCCT-1 cells CXCR7 was found to interact with β-arrestin 2, which was necessary to mediate CXCL12-induced migration, but not survival. In conclusion, CXCR7 is widely expressed in CCA, and contributes to the aggressive phenotype of CCA cells, inducing cell migration, invasion, adhesion, survival, growth and stem cell-like features. Cell migration induced by CXCR7 requires interaction with β-arrestin 2.     

Palaeovegetational reconstruction based on pollen and seeds/fruits from a Bronze Age archaeological site in Tuscany (Italy)

Abstract

A reconstruction of the vegetation surrounding the Bronze Age archaeological site of San Lorenzo a Greve (Florence) based on pollen and seed/fruit records is presented. Pollen analysis suggests the presence of prevailingly open and damp landscapes, typically occurring on alluvial soils. Patches of woodland, mostly formed by deciduous Quercus, Ulmus, Salix, were alternated to the grasslands. Vitis also probably grew in these damp thickets together with Alnus and Hedera. The forests on the hilly slopes included deciduous Quercus, Carpinus betulus, Corylus, Cornus mas, and Sambucus nigra. Where the soil was well drained, Ostrya carpinifolia and Mediterranean evergreen elements such as Q. ilex and Viburnum tinus grew. In the landscape scenario reconstructed by pollen analysis, seeds/fruits indicated the presence of specific plants which produce a low amount of pollen: they are seldom recorded in pollen spectra but their fruits were commonly gathered in prehistory.     

文化遗产类历史园林植物景观保护与修复——以国际公约及国内外实践为切入点

针对历史园林遗产中植物景观保护面临的现存问题,从国际公约方面着手分析,指出中国古典园林营造修复的要点与相关国际宪章之间的差异,尤其是如何对待历史园林“真实性”的问题。并借助欧洲、美国、日本与中国相关案例研究,论述国内外在该方面研究实践的共性、差异及其成因。最后在分析国际同行经验基础上,结合中国历史文化背景,总结并提出了可供中国园林遗产保护与修复工作参考的经验及思想。     

Sulfonamide inhibition profile of the γ-carbonic anhydrase identified in the genome of the pathogenic bacterium Burkholderia pseudomallei the etiological agent responsible of melioidosis

A new γ-carbonic anhydrase (CA, EC 4.1.1.1) was cloned and characterized kinetically in the genome of the bacterial pathogen Burkholderia pseudomallei, the etiological agent of melioidosis, an endemic disease of tropical and sub-tropical regions of the world. The catalytic activity of this new enzyme, BpsCAγ, is significant with a k_cat of 5.3 × 10⁵ s^?1 and k_cat/K_m of 2.5 × 10⁷ M^?1 × s^?1 for the physiologic CO₂ hydration reaction. The inhibition constant value for this enzyme for 39 sulfonamide inhibitors was obtained. Acetazolamide, benzolamide and metanilamide were the most effective (K_Is of 149–653 nM) inhibitors of BpsCAγ activity, whereas other sulfonamides/sulfamates such as ethoxzolamide, topiramate, sulpiride, indisulam, sulthiame and saccharin were active in the micromolar range (K_Is of 1.27–9.56 μM). As Burkholderia pseudomallei is resistant to many classical antibiotics, identifying compounds that interfere with crucial enzymes in the B. pseudomallei life cycle may lead to antibiotics with novel mechanisms of action.     

Nickel(II)—bleomycin: spectral investigation of the metal binding site

Bleomycin (blm) solutions containing the nickel(II) ion have been investigated through ¹H nmr, ligand field and circular dichroism spectroscopies. It has been found the blm binds the metal ion in a pH dependent fashion. The spectral data are consistent with the presence of at least two species. It is suggested that in the low pH region blm binds to nickel(II) through the β-aminoalanino residue, whereas in the high pH region, the 4-amino-pyrimidine, imidazole, and amido group of β-hydroxy-histidine are also involved in coordination.     

The reaction of copper-2,9-dimethyl-1,10-phenanthroline with hydrogen peroxide

The copper complex of 2,9-dimethyl-1,10-phenanthroline(2,9-dmp) is accumulated by a variety of organisms and is highly toxic. Bioaccumulation depends on reduction of copper(II) to (I), since only the copper(I)-2,9-dmp complex is lipophilic. In the case of the marine diatom, Nitzschia closterium, it is proposed that hydrogen peroxide, produced by the algae during photosynthesis, is the in vivo reductant. Hydrogen peroxide rapidly reduces copper(II)-2,9-dmp, but an excess of H₂O₂ leads to destruction of the yellow copper(I) complex. Rate constants for the formation and degradation of the yellow complex are reported. Oxygen, light, and a hydroxylating agent are released during the degradation reaction. A reaction mechanism is proposed for the destruction of copper-2,9-dmp by excess H₂O₂, involving attack on the 5, 6 positions of the phenanthroline ring by hydroxyl radical, then further oxidation by singlet oxygen and H₂O₂. These in vivo degradation reactions are believed to be the cause of the extreme toxicity of the complex.