Histone deacetylase inhibitors as a tool to up-regulate new fungal biosynthetic products: isolation of EGM-556, a cyclodepsipeptide, from Microascus sp

The histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) was used to turn on the biosynthesis of EGM-556, a new cyclodepsipeptide of hybrid biosynthetic origin, isolated from the Floridian marine sediment-derived fungus Microascus sp. The absolute configurations of three chiral centers were determined by Marfey's derivatization. EGM-556 represents one of the few examples in which silent biosynthetic genes, encoding a new secondary metabolite, were activated by means of epigenetic manipulation of the fungal metabolome.     

Rh(III)-catalyzed oxidative coupling of unactivated alkenes via C-H activation

Oxime directed aromatic C-H bond activation and oxidative coupling to alkenes is reported using a cationic Rh(III) catalyst. Significantly, the method can be used to oxidatively couple unactivated, aliphatic alkenes.     

Stereoselective rhodium-catalyzed amination of alkenes

The first stereoselective rhodium-catalyzed intermolecular aziridination and C-H amination of alkenes to produce chiral carbamate-protected aziridines and allylic amines is described. Good yields and diastereoselectivities were achieved using a readily available chiral N-tosyloxycarbamate and stoichiometric amount of the alkene substrate. Furthermore the protecting group is easy to cleave under mild reaction conditions.     

A rapid and reversible colorimetric assay for the characterization of aminated solid surfaces

The covalent immobilization of synthetic or natural macromolecular compounds containing amino groups onto polystyrene (PS) solid surfaces is of great interest in diagnostic applications. A sensitive assay allowing the determination of reactive end groups is therefore a powerful tool for predicting the performance of the active surface. Recently, we reported the use of the Coomassie brilliant blue (CBB) colorimetric reagent to quantify protonated groups (N⁺) in linear and dendritic structures in solution (Coussot et al., Polym Int 58(5):511–518, 2009). In this work, a simple method using CBB dye for the characterization of PS aminated solid surfaces is developed. The proposed amino density estimation by colorimetric assay (ADECA) method is based on the reversible complexation of the dye with the N⁺ groups on solid surfaces. The assay measures the released dye thanks to the use of a unique sodium carbonate–methanol buffer. Thereby, for the first time, the same surface can be used for characterization and for further coupling applications. A surface density of four N⁺ groups per square nanometer can be measured in PS microwell format, the whole characterization being done within 30 min. Performances of this new colorimetric-based method are detailed. The ADECA method is further demonstrated to be useful for the characterization of aminated polypropylene and glass materials with various sizes and shapes.     

The possible number of islands on the sea

Let a height function f be a real valued function on R². A connected subset of R² is called an island, if there is a water level such that H is an island in the classical sense. We show that an island system is always laminar. Among others, in this paper we prove that the cardinality of a maximal laminar system is either countable or continuum.     

Essential spectra of quasi-parabolic composition operators on Hardy spaces of analytic functions

In this work we study the essential spectra of composition operators on Hardy spaces of analytic functions which might be termed as “quasi-parabolic.” This is the class of composition operators on H² with symbols whose conjugate with the Cayley transform on the upper half-plane are of the form φ(z)=z+ψ(z), where ψ∈H^∞(H) and ℑ(ψ(z))>?>0. We especially examine the case where ψ is discontinuous at infinity. A new method is devised to show that this type of composition operator fall in a C*-algebra of Toeplitz operators and Fourier multipliers. This method enables us to provide new examples of essentially normal composition operators and to calculate their essential spectra.     

Cholesky decomposition of a positive semidefinite matrix with known kernel

The Cholesky decomposition of a symmetric positive semidefinite matrix A is a useful tool for solving the related consistent system of linear equations or evaluating the action of a generalized inverse, especially when A is relatively large and sparse. To use the Cholesky decomposition effectively, it is necessary to identify reliably the positions of zero rows or columns of the factors and to choose these positions so that the nonsingular submatrix of A of the maximal rank is reasonably conditioned. The point of this note is to show how to exploit information about the kernel of A to accomplish both tasks. The results are illustrated by numerical experiments.     

Toeplitz Operators on Bloch-type Spaces and Classes of Weighted Sobolev Distributions

We study Toeplitz operators between analytic Bloch-type spaces of the unit disk. We construct suitable classes of distributions that generate bounded Toeplitz operators between these spaces. The classes are naturally connected to the corresponding results in the reflexive Bergman space setting and previously known results on A ¹ and the Bloch space. We also study distributional symbols satisfying logarithmic BMO-condition. In addition, sufficient compactness criteria are provided.     

Structure and dynamics of highly PEG-ylated sterically stabilized micelles in aqueous media

Molecular assemblies of highly PEG-ylated phospholipids are important in many biomedical applications. We have studied sterically stabilized micelles (SSMs) of self-assembled DSPE–PEG2000 in pure water and isotonic HEPES-buffered saline solution. The observed SSM sizes of 2–15 nm largely depend on the solvent and the lipid concentration used. The critical micelle concentration of DSPE–PEG2000 is 10 times higher in water than in buffer, and the viscosity of the dispersion dramatically increases with the lipid concentration. To explain the experimentally observed results, we performed atomistic molecular dynamics simulations of solvated SSMs. Our modeling revealed that the observed assemblies have very different aggregation numbers (N(agg) ≈ 90 in saline solution and N(agg) < 8 in water) because of very different screening of their charged PO4(–) groups. We also demonstrate that the micelle cores can inflate and their coronas can fluctuate strongly, thus allowing storage and delivery of molecules with different chemistries.