Genetic origin of homopyrones, a rare type of hybrid phenylpropanoid- and polyketide-derived yellow pigments from Aspergillus homomorphus.

In recent years, there has been an increasing demand for the replacement of synthetic food colorants with naturally derived alternatives. Filamentous fungi are prolific producers of secondary metabolites including polyketide-derived pigments, many of which have not been fully characterized yet. During our ongoing investigations of black aspergilli, we noticed that Aspergillus homomorphus turned yellow when cultivated on malt extract agar plates.

Improved NOE fitting for flexible molecules based on molecular mechanics data - a case study with S-adenosylmethionine.

The use of molecular dynamics (MD) calculations to derive relative populations of conformers is highly sensitive to both timescale and parameterisation of the MD. Where these calculations are coupled with NOE data to determine the dynamics of a molecular system, this can present issues if these populations are thus relied upon. We present an approach that refines the highly accurate PANIC NMR methodology combined with clustering approaches to generate conformers, but without restraining the simulations or considering the relative population distributions generated by MD.

Karmitoxin: An Amine-Containing Polyhydroxy-Polyene Toxin from the Marine Dinoflagellate Karlodinium armiger.

Marine algae from the genus Karlodinium are known to be involved in fish-killing events worldwide. Here we report for the first time the chemistry and bioactivity of a natural product from the newly described mixotrophic dinoflagellate Karlodinium armiger. Our work describes the isolation and structural characterization of a new polyhydroxy-polyene named karmitoxin.

S HMBC hetero: Spin-State-Selective HMBC for accurate measurement of long-range heteronuclear coupling constants.

A novel method, Spin-State-Selective (S) HMBC hetero, for accurate measurement of heteronuclear coupling constants is introduced. The method extends the S HMBC technique for measurement of homonuclear coupling constants by appending a pulse sequence element that interchanges the polarization in C-H methine pairs. This amounts to converting the spin-state selectivity from H spin states to C spin states in the spectra of long-range coupled H spins, allowing convenient measurement of heteronuclear coupling constants similar to other S or E.

Specific Electrostatic Molecular Recognition in Water.

The identification of pairs of small peptides that recognize each other in water exclusively through electrostatic interactions is reported. The target peptide and a structure-biased combinatorial ligand library consisting of ≈78 125 compounds were synthesized on different sized beads. Peptide-peptide interactions could conveniently be observed by clustering of the small, fluorescently labeled target beads on the surface of larger ligand-containing beads.

S(3) HMBC: Spin-State-Selective HMBC for accurate measurement of homonuclear coupling constants. Application to strychnine yielding thirteen hitherto unreported J(HH).

A novel method, Spin-State-Selective (S(3)) HMBC, for accurate measurement of homonuclear coupling constants is introduced. As characteristic for S(3) techniques, S(3) HMBC yields independent subspectra corresponding to particular passive spin states and thus allows determination of coupling constants between detected spins and homonuclear coupling partners along with relative signs. In the presented S(3) HMBC experiment, spin-state selection occurs via large one-bond coupling constants ensuring high editing accuracy and unequivocal sign determination of the homonuclear long-range relative to the associated one-bond coupling constant.

Methyl effect in azumamides provides insight into histone deacetylase inhibition by macrocycles.

Natural, nonribosomal cyclotetrapeptides have traditionally been a rich source of inspiration for design of potent histone deacetylase (HDAC) inhibitors. We recently disclosed the total synthesis and full HDAC profiling of the naturally occurring azumamides ( J. Med.

Dereplication guided discovery of secondary metabolites of mixed biosynthetic origin from Aspergillus aculeatus.

Investigation of the chemical profile of the industrially important black filamentous fungus Aspergillus aculeatus by UHPLC-DAD-HRMS and subsequent dereplication has led to the discovery of several novel compounds. Isolation and extensive 1D and 2D NMR spectroscopic analyses allowed for structural elucidation of a dioxomorpholine, a unique okaramine, an aflavinine and three novel structures of mixed biosynthetic origin, which we have named aculenes A-C. Moreover, known analogues of calbistrins, okaramines and secalonic acids were detected.