A sterically hindered tetrakis(pyrazolyl)borate: Synthesis, characterization and coordinative behaviour

The sterically hindered tetrakis-(3-(p-tolylpyrazolyl)borate [pz⁰Tp^p-Tol] has been prepared and its reaction with CuX₂.nH₂O (X = Cl or acetate (OAc), M(NO₃)₂.6H₂O (M = Ni, or Co) and MCl₂ (M = Zn or Cd) has been investigated. [M(pz⁰Tp^p-Tol)X(Hpz^p-Tol)] (M = Cu, X = Cl or OAc; M = Ni or Co, X = NO₃) and [M(pz⁰Tp^p-Tol)Cl(Hpz^p-Tol)_2-n(H₂O)_n] have been synthesised and their spectroscopic properties described, the five-coordinated Cu species being also structurally characterized. The methyl groups in the para-tolyl fragments of the ligand strongly influences the stoichiometry and structure of the metal complexes.     

Diverse Evolutionary Histories for β-adrenoreceptor Genes in Humans

In humans, three genes—ADRB1, ADRB2 and ADRB3—encode β-adrenoreceptors (ADRB); these molecules mediate the action of catecholamines in multiple tissues and play pivotal roles in cardiovascular, respiratory, metabolic, and immunological functions. Genetic variants in ADRB genes have been associated with widespread diseases and conditions, but inconsistent results have often been obtained. Here, we addressed the recent evolutionary history of ADRB genes in human populations. Although ADRB1 is neutrally evolving, most tests rejected neutral evolution for ADRB2 in European, African, and Asian population samples. Analysis of inferred haplotypes for ADRB2 revealed three major clades with a coalescence time of 1–1.5 million years, suggesting that the gene is either subjected to balancing selection or undergoing a selective sweep. Haplotype analysis also revealed ethnicity-specific differences. Additionally, we observed significant deviations from Hardy-Weinberg equilibrium (HWE) for ADRB2 genotypes in distinct European cohorts; HWE deviation depends on sex (only females are in disequilibrium), and genotypes displaying maximum and minimum relative fitness differ across population samples, suggesting a complex situation possibly involving epistasis or maternal selection. Overall, our data indicate that future association studies involving ADRB2 will benefit from taking into account ethnicity-specific haplotype distributions and sex-based effects. With respect to ADRB3, our data indicate that the gene has been subjected to a selective sweep in African populations, the Trp64 variant possibly representing the selection target. Given the previous association of the ancestral ADRB3 Arg64 allele with obesity and type 2 diabetes, dietary adaptations might represent the underlying selective force.     

New pyrrole-based histone deacetylase inhibitors: binding mode, enzyme- and cell-based investigations

Aroyl-pyrrolyl-hydroxy-amides (APHAs) are a class of synthetic HDAC inhibitors described by us since 2001. Through structure-based drug design, two isomers of the APHA lead compound 1, the 3-(2-benzoyl-1-methyl-1H-pyrrol-4-yl)-N-hydroxy-2-propenamide 2 and the 3-(2-benzoyl-1-methyl-1H-pyrrol-5-yl)-N-hydroxy-2-propenamide 3 (iso-APHAs) were designed, synthesized and tested in murine leukemia cells as antiproliferative and cytodifferentiating agents. To improve their HDAC activity and selectivity, chemical modifications at the benzoyl moieties were investigated and evaluated using three maize histone deacetylases: HD2, HD1-B (class I human HDAC homologue), and HD1-A (class II human HDAC homologue). Docking experiments on HD1-A and HD1-B homology models revealed that the different compounds selectivity profiles could be addressed to different binding modes as observed for the reference compound SAHA. Smaller hydrophobic cap groups improved class II HDAC selectivity through the interaction with HD1-A Asn89-Ser90-Ile91, while bulkier aromatic substituents increased class I HDAC selectivity. Taking into account the whole enzyme data and the functional test results, the described iso-APHAs showed a behaviour of class I/IIb HDACi, with 4b and 4i preferentially inhibiting class IIb and class I HDACs, respectively. When tested in the human leukaemia U937 cell line, 4i showed altered cell cycle (S phase arrest), joined to high (51%) apoptosis induction and significant (21%) differentiation activity.     

Xylan decomposition by Aspergillus clavatus endo-xylanase

Agricultural and forest waste products are abundant and low-cost biomass sources useful in renewable fuel energy and feedstock preparation. Hydrolysis of a major biomass component, hemicellulose, is accomplished by the action of endo-xylanases. Reaction products vary in composition and degree of polymerization as a function of both feedstock and the enzyme activities utilized, ranging from monomeric sugars to complex branched polysaccharides. The study herein describes heterologous expression in Aspergillus awamori of a ββ-(1-4) endo-xylanase isolated from the whole-genome DNA sequence of A. clavatus along with a comprehensive biochemical and functional analysis of the enzyme, including substrate preference and hydrolysis patterns. The A. clavatus xylanase promotes incomplete hydrolysis of xylan substrates resulting in xylobiose, xylotriose and xylotetraose. Incomplete degradation resulting in xylo-oligomers is appealing for functional foods as the beneficial effect of oligosaccharides on gastrointestinal micro flora includes preventing proliferation of pathogenic intestinal bacteria and facilitating digestion and absorption of nutrients.     

Potential immunoregulatory role of heme oxygenase-1 in human milk: a combined biochemical and molecular modeling approach

Human milk contains biological factors that are involved in a newborn's growth and immune system regulation. By integrating standard biochemical experimental protocols with computational methods, the present study investigates the presence of heme oxygenase-1 (HO-1), a cytoprotective enzyme, in human milk at different levels of maturation and in milk formulae. Furthermore, we evaluated cytokine and glutathione S-transferase (GSH) levels. Samples were collected from colostrum (on Day 1 after birth), from transition milk (on Postdelivery Days 7 and 14) and from mature milk (on Day 30 after delivery) in 14 healthy women. HO-1 protein, GSH and cytokines levels were measured using enzyme-linked immunosorbent assay and flow cytometry. HO-1 protein levels were significantly higher in colostrum (1.33 ng/ml; 5th centile 0.92; 95th centile 2.38) and in transition milk at 14 days (0.97 ng/ml; 5th centile 0.87; 95th centile 1.45) than in mature milk (0.9 ng/ml; 5th centile 0.8; 95th centile 1.38). Levels of HO-1 in milk formulae were similar to those in colostrum. No significant differences in GSH content were observed in mature milk, transition milk and colostrum, whereas significantly higher GSH levels were observed in milk formulae. No significant levels of cytokines, with the exception of interleukin-8, were found. Computational studies on the possible interactions between HO-1 and CD91 were carried out by a battery of softwares, namely, GRAMM (version 1.03), DALI, CLUSTALW (version 2.0), PatchDock and FireDock, mutually counterchecking and validating each other. The computational results, the strong convergence (to the same “solution”) of which finally leads to an “experimental-like” character, showed that HO-1 may bind to CD91, thus suggesting its major role as a new chaperokine in immune response regulation. These findings, which connect and integrate biochemical data and computational data interpretation, represent a synergistic and powerful means of conducting biological research.     

Cytochromes: Reactivity of the "dark side" of the heme

Ligand binding to the heme distal side is a paradigm of heme-protein biochemistry, the proximal axial ligand being in most cases a His residue. NO binds to the ferrous heme-Fe-atom giving rise to hexa-coordinated adducts (as in myoglobin and hemoglobin) with His and NO as proximal and distal axial ligands, respectively, or to penta-coordinated adducts (as in soluble guanylate cyclase) with NO as the axial distal ligand. Recently, the ferrous derivative of Alcaligenes xylosoxidans cytochrome c' (Axcyt c') and of cardiolipin-bound horse heart cytochrome c (CL-hhcyt c) have been reported to bind NO to the "dark side" of the heme (i.e., as the proximal axial ligand) replacing the endogenous ligand His. Conversely, CL-free hhcyt c behaves as ferrous myoglobin by binding NO to the heme distal side, keeping His as the proximal axial ligand. Moreover, the ferrous derivative of CL-hhcyt c binds CO at the heme distal side, the proximal axial ligand being His. Furthermore, CL-hhcyt c shows peroxidase activity. In contrast, CL-free hhcyt c does not bind CO and does not show peroxidase activity. This suggests that heme-proteins may utilize both sides of the heme for ligand discrimination, which appears to be modulated allosterically. Here, structural and functional aspects of NO binding to ferrous Axcyt c' and (CL-)hhcyt c are reviewed.