Substituted Imidazole of 5-Fluoro-2-[4-[(2-phenyl-1H-imidazol-5- yl)methyl]-1-piperazinyl]pyrimidine Inactivates Cytochrome P450 2D6 by Protein Adduction

detected by mass spectrometry indicate that the phenyl group on the imidazole ring of SCH 66712 is one site of oxidation by CYP2D6 and could lead to methylene quinone formation. Three other metabolites were also observed. For understanding the metabolic pathway that leads to CYP2D6 inactivation, metabolism studies with CYP2C9 and CYP2C19 were performed because neither of these enzymes is significantly inhibited by SCH 66712. The metabolites formed by CYP2C9 and CYP2C19 are the same as those seen with CYP2D6, although in different abundance. Modeling studies with CYP2D6 revealed potential roles of various active site residues in the oxidation of SCH 66712 and inactivation of CYP2D6 and showed that the phenyl group of SCH 66712 is positioned at 2.2 Å from the heme iron

Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution

The nanoscopic adhesive and frictional behaviour of end-grafted poly[2-(dimethyl amino)ethyl methacrylate] (PDMAEMA) films (brushes) in contact with gold- or PDMAEMA-coated atomic force microscope tips in potassium halide solutions with different concentrations up to 300 mM is a strong function of salt concentration. The conformation of the polymers in the brush layer is sensitive to salt concentration, which leads to large changes in adhesive forces and the contact mechanics at the tip–sample contact, with swollen brushes (which occur at low salt concentrations) yielding large areas of contact and friction–load plots that fit JKR behaviour, while collapsed brushes (which occur at high salt concentrations) yield sliding dominated by ploughing, with conformations in between fitting DMT mechanics. The relative effect of the different anions follows the Hofmeister series, with I − collapsing the brushes more than Br − and Cl − for the same salt concentration

Caspofungin on ARGET-ATRP grafted PHEMA polymers: enhancement and selectivity of prevention of attachment of Candida albicans

Abstract not availableThomas D. Michl, Carla Giles, Piotr Mocny, Kathryn Futrega, Michael R. Doran, Harm-Anton Klok, Hans J. Griesser, Bryan R. Coa

An acid test: Facile SI-ARGET-ATRP of methacrylic acid

Atom transfer radical polymerization (ATRP) of methacrylic acid (MAA) is challenging. Herein is reported a study of conditions for facile surface‐initiated ATRP by activator regenerated electron transfer (SI‐ARGET‐ATRP) growth of poly‐methacrylic acid (PMAA) chains from a plasma polymer surface bearing surface‐immobilized α‐bromoisobutyryl bromide, with no deoxygenation required. Factors that affect PMAA polymer growth off the surface under ARGET‐ATRP conditions are systematically investigated, such as monomer/catalyst ratio, solvent, and, most importantly, addition of salts and change of pH. While the concentrations of the copper catalyst and acid affect grafting, the most pronounced effect arises from the concentration of chloride ions. Adding 0.1 m NaCl and acidifying the reaction solution to pH 3 offers the best trade‐off between reaction rate and reproducibility; yielding ≈60 nm thick PMAA graft polymers in 1 h under ambient conditions. Using this easily scalable recipe and surface analysis, the grafted polymers are verified to be pure PMAA and the graft coatings to be homogenous across a substrate of 100 mm diameter.Thomas D. Michl, Dimitri Jung, Andrea Pertoldi, Anna Schulte, Piotr Mocny, Harm-Anton Klok, Holger Schönherr, Carla Giles, Hans J. Griesser, and Bryan R. Coa

Novel Hemin Binding Domains in the Corynebacterium diphtheriae HtaA Protein Interact with Hemoglobin and Are Critical for Heme Iron Utilization by HtaA▿

The human pathogen Corynebacterium diphtheriae utilizes hemin and hemoglobin as iron sources for growth in iron-depleted environments. The use of hemin iron in C. diphtheriae involves the dtxR- and iron-regulated hmu hemin uptake locus, which encodes an ABC hemin transporter, and the surface-anchored hemin binding proteins HtaA and HtaB. Sequence analysis of HtaA and HtaB identified a conserved region (CR) of approximately 150 amino acids that is duplicated in HtaA and present in a single copy in HtaB. The two conserved regions in HtaA, designated CR1 and CR2, were used to construct glutathione S-transferase (GST) fusion proteins (GST-CR1 and GST-CR2) to assess hemin binding by UV-visual spectroscopy. These studies showed that both domains were able to bind hemin, suggesting that the conserved sequences are responsible for the hemin binding property previously ascribed to HtaA. HtaA and the CR2 domain were also shown to be able to bind hemoglobin (Hb) by the use of an enzyme-linked immunosorbent assay (ELISA) method in which Hb was immobilized on a microtiter plate. The CR1 domain exhibited a weak interaction with Hb in the ELISA system, while HtaB showed no significant binding to Hb. Competitive binding studies demonstrated that soluble hemin and Hb were able to inhibit the binding of HtaA and the CR domains to immobilized Hb. Moreover, HtaA was unable to bind to Hb from which the hemin had been chemically removed. Alignment of the amino acid sequences of CR domains from various Corynebacterium species revealed several conserved residues, including two highly conserved tyrosine (Y) residues and one histidine (H) residue. Site-directed mutagenesis studies showed that Y361 and H412 were critical for the binding to hemin and Hb by the CR2 domain. Biological assays showed that Y361 was essential for the hemin iron utilization function of HtaA. Hemin transfer experiments demonstrated that HtaA was able to acquire hemin from Hb and that hemin bound to HtaA could be transferred to HtaB. These findings are consistent with a proposed mechanism of hemin uptake in C. diphtheriae in which hemin is initially obtained from Hb by HtaA and then transferred between surface-anchored proteins, with hemin ultimately transported into the cytosol by an ABC transporter

Bordetella pertussis pathogenesis: current and future challenges

Pertussis, or whooping cough, has recently reemerged as a major public health threat despite high levels of vaccination against the etiological agent, Bordetella pertussis. In this Review, we describe the pathogenesis of this disease, with a focus on recent mechanistic insights into virulence factor function. We also discuss the changing epidemiology of pertussis and the challenges of vaccine development. Despite decades of research, many aspects of B. pertussis physiology and pathogenesis remain poorly understood. We highlight knowledge gaps that must be addressed to develop improved vaccines and therapeutic strategies

Protein Design: Toward Functional Metalloenzymes

The scope of this Review is to discuss the construction of metal sites in designed protein scaffolds. We categorize the effort of designing proteins into redesign, which is to rationally engineer desired functionality into an existing protein scaffold,(1-9) and de novo design, which is to build a peptidic or protein system that is not directly related to any sequence found in nature yet folds into a predicted structure and/or carries out desired reactions.(10-12) We will analyze and interpret the significance of designed protein systems from a coordination chemistry and biochemistry perspective, with an emphasis on those containing constructed metal sites as mimics for metalloenzymes