Quantitative analysis of the bacteriophage Qβ infection cycle

In this study, the infection cycle of bacteriophage Qβ was investigated. Adsorption of bacteriophage Qβ to Escherichia coli is explained in terms of a collision reaction, the rate constant of which was estimated to be 4 × 10^− 10 ml/cells/min. In infected cells, approximately 130 molecules of β-subunit and 2 × 10⁵ molecules of coat protein were translated in 15 min. Replication of Qβ RNA proceeded in 2 steps—an exponential phase until 20 min and a non-exponential phase after 30 min. Prior to the burst of infected cells, phage RNAs and coat proteins accumulated in the cells at an average of up to 2300 molecules and 5 × 10⁵ molecules, respectively. An average of 90 infectious phage particles per infected cell was released during a single infection cycle up to 105 min.     

Selective small molecule inhibitors of the potential breast cancer marker,human arylamine N-acetyltransferase 1, and its murine homologue,mouse arylamine N-acetyltransferase 2

The identification, synthesis and evaluation of a series of rhodanine and thiazolidin-2,4-dione derivatives as selective inhibitors of human arylamine N-acetyltransferase 1 and mouse arylamine N-acetyltransferase 2 is described. The most potent inhibitors identified have submicromolar activity and inhibit both the recombinant proteins and human NAT1 in ZR-75 cell lysates in a competitive manner. ¹H NMR studies on purified mouse Nat2 demonstrate that the inhibitors bind within the putative active site of the enzyme.     

Restriction of apical coordination in the square-planar nickel(II) complexes of meso-1,5,8,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane with axially oriented C-methyl groups

Crystal structures of nickel(II) complexes coordinated with cyclam-type macrocyclic tetraamine, meso-1,5,8,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane (L) in two complex salts 1 and 2 have been determined by single-crystal X-ray crystallographic analysis. Complexes in both salts adopted trans-III structure, but the C-methyl groups of L adopted equatorial configuration in 1, while axial in 2. Complex 2 is the first example of complex of cyclam-type tetraamine with only axially oriented C-methyl groups. Complex in 1 adopted six-coordinated octahedral geometry with two water molecules occupying two apical sites, while in 2, apical sites were vacant resulting in four-coordinated square-planar geometry. UV-Vis spectra in various solutions also revealed the formation of octahedral six-coordinated complex for 1 but not for 2. Network of hydrogen bonds involving chloride ion, water, and N-H of L was present in crystals of both 1 and 2. Convenient synthetic paths for 1 and 2 are also presented.     

Novel and potent inhibitors of stearoyl-CoA desaturase-1. Part I: Discovery of 3-(2-hydroxyethoxy)-4-methoxy-N-[5-(3-trifluoromethylbenzyl)thiazol-2-yl]benzamide

A series of structurally novel stearoyl-CoA desaturase-1 (SCD-1) inhibitors has been identified by optimizing a hit from our corporate library. Preliminary structure–activity relationship (SAR) studies led to the discovery of the highly potent and orally bioavailable thiazole-based SCD-1 inhibitor, 3-(2-hydroxyethoxy)-4-methoxy-N-[5-(3-trifluoromethylbenzyl)thiazol-2-yl]benzamide (23a).     

[18F]FEAC and [18F]FEDAC: Two novel positron emission tomography ligands for peripheral-type benzodiazepine receptor in the brain

[¹⁸F]FEAC ([¹⁸F]4a) and [¹⁸F]FEDAC ([¹⁸F]4b) were developed as two novel positron emission tomography (PET) ligands for peripheral-type benzodiazepine receptor (PBR). [¹⁸F]4a and [¹⁸F]4b were synthesized by fluoroethylation of precursors 8a and 8b with [¹⁸F]FCH₂CH₂Br ([¹⁸F]9), respectively. Small-animal PET scan for a neuroinflammatory rat model showed that the two radioligands had high uptakes of radioactivity in the kainic acid-infused striatum, a brain region where PBR density was increased.     

Optimization of a series of 2,4-diaminopyridines as neuropeptide Y Y1 receptor antagonists with reduced hERG activity

The synthesis and evaluation of a series of 2,4-diaminopyridine-based neuropeptide Y Y1 (NPY Y1) receptor antagonists are described. Compound 1 was previously reported by our laboratory to be a potent and selective Y1 antagonist; however, 1 was also found to have potent hERG inhibitory activity. The main focus of this communication is structure–activity relationship development aimed at eliminating the hERG activity of 1. This resulted in the identification of compound 3d as a potent and selective NPY Y1 antagonist with reduced hERG liability.     

Influence of oxidative and osmotic stresses on the structure of the cell wall mannan of Candida albicans serotype A

In this study, we investigated the structural changes in the cell wall mannan of Candida albicans serotype A strain cells cultured under various stress conditions, that is, oxidative stress of 3.5 mM H₂O₂, osmotic stress of 1.5 M NaCl, and heat stress at 37 °C, compared with the normal condition of 30 °C in yeast extract-added Sabouraud liquid medium (YSLM). Based on the ¹H nuclear magnetic resonance (NMR) and fluorophore-assisted carbohydrate electrophoresis (FACE) analyses of the mannans, we showed that the proportion of the terminal β-1,2-linked mannose side chain unit in the mannan increased in the cell proliferation process under both the normal condition and the oxidative stress condition. The osmotic stress induced a slight decrease in the proportion of the β-1,2-linked mannose unit in the acid-labile fraction. The heat stress induced a significant decrease in the proportions of the β-1,2-linked mannose unit in both the acid-labile and acid-stable fractions. Based on these results, we propose that C. albicans significantly changes the mannan structures under various stress conditions and that sufficient attention to the cultural conditions is needed to perform an accurate diagnosis of candidiasis.     

Competition between Folding, Native-State Dimerisation and Amyloid Aggregation in β-Lactoglobulin

We show that a series of peptides corresponding to individual β-strands in native β-lactoglobulin readily form amyloid aggregates and that such aggregates are capable of seeding fibril formation by a full-length form of β-lactoglobulin in which the disulfide bonds are reduced. By contrast, preformed fibrils corresponding to only one of the β-strands that we considered, βA, were found to promote fibril formation by a full-length form of β-lactoglobulin in which the disulfide bonds are intact. These results indicate that regions of high intrinsic aggregation propensity do not give rise to aggregation unless at least partial unfolding takes place. Furthermore, we found that the high aggregation propensity of one of the edge strands, βI, promotes dimerisation of the native structure rather than misfolding and aggregation since the structure of βI is stabilised by the presence of a disulfide bond. These findings demonstrate that the interactions that promote folding and native-state oligomerisation can also result in high intrinsic amyloidogenicity. However, we show that the presence of the remainder of the sequence dramatically reduces the net overall aggregation propensity by negative design principles that we suggest are very common in biological systems as a result of evolutionary processes.