Subclonal Cancer Driver Mutations Are Prevalent in the Unresected Peritumoral Edema of Adult Diffuse Gliomas.

Adult diffuse gliomas commonly recur regardless of therapy. As recurrence typically arises from the peritumoral edema adjacent to the resected bulk tumor, the profiling of somatic mutations from infiltrative malignant cells within this critical, unresected region could provide important insights into residual disease. A key obstacle has been the inability to distinguish between next-generation sequencing (NGS) noise and the true but weak signal from tumor cells hidden among the noncancerous brain tissue of the peritumoral edema. Here, we developed and validated True2 sequencing to reduce NGS-associated errors to <1 false positive/100 kb panel positions while detecting 97.6% of somatic mutations with an allele frequency ≥0.1%. True2 was then used to study the tumor and peritumoral edema of 22 adult diffuse gliomas including glioblastoma, astrocytoma, oligodendroglioma, and NF1-related low-grade neuroglioma. The tumor and peritumoral edema displayed a similar mutation burden, indicating that surgery debulks these cancers physically but not molecularly. Moreover, variants in the peritumoral edema included unique cancer driver mutations absent in the bulk tumor. Finally, analysis of multiple samples from each patient revealed multiple subclones with unique mutations in the same gene in 17 of 22 patients, supporting the occurrence of convergent evolution in response to patient-specific selective pressures in the tumor microenvironment that may form the molecular foundation of recurrent disease. Collectively, True2 enables the detection of ultralow frequency mutations during molecular analyses of adult diffuse gliomas, which is necessary to understand cancer evolution, recurrence, and individual response to therapy. SIGNIFICANCE: True2 is a next-generation sequencing workflow that facilitates unbiased discovery of somatic mutations across the full range of variant allele frequencies, which could help identify residual disease vulnerabilities for targeted adjuvant therapies.

Shear Stress-Responsive Polymersome Nanoreactors Inspired by the Marine Bioluminescence of Dinoflagellates.

Some marine plankton called dinoflagellates emit light in response to the movement of surrounding water, resulting in a phenomenon called milky seas or sea sparkle. The underlying concept, a shear-stress induced permeabilisation of biocatalytic reaction compartments, is transferred to polymer-based nanoreactors. Amphiphilic block copolymers that carry nucleobases in their hydrophobic block are self-assembled into polymersomes. The membrane of the vesicles can be transiently switched between an impermeable and a semipermeable state by shear forces occurring in flow or during turbulent mixing of polymersome dispersions. Nucleobase pairs in the hydrophobic leaflet separate when mechanical force is applied, exposing their hydrogen bonding motifs and therefore making the membrane less hydrophobic and more permeable for water soluble compounds. This polarity switch is used to release payload of the polymersomes on demand, and to activate biocatalytic reactions in the interior of the polymersomes.

Chromophores of chromophores: a bottom-up Hückel picture of the excited states of photoactive proteins.

Many photoactive proteins contain chromophores based on para-substituted phenolate anions which are an essential component of their electronic structure. Here, we present a reductionist approach to gain fundamental insight into the evolution of electronic structure as the chromophore increases in complexity from phenolate to that in GFP. Using frequency- and angle-resolved photoelectron spectroscopy, in combination with electronic structure theory, the onset of excited states that are responsible for the characteristic spectroscopic features in biochromophores are determined. A comprehensive, yet intuitive picture of the effect of phenolate functionalisation is developed based on simple Hückel theory. Specifically, the first two bright excited states can be constructed from a linear combination of molecular orbitals localised on the phenolate and para-substituent groups. This essential interaction is first observed for p-vinyl-phenolate. This bottom-up approach offers a readily accessible framework for the design of photoactive chromophores.

Sensitivity of Photoelectron Angular Distributions to Molecular Conformations of Anions.

An anion photoelectron imaging study probing the sensitivity of the photoelectron angular distribution (PAD) to conformational changes is presented. The PADs of a series of para-substituted phenolate anions is compared with those calculated using the Dyson orbital formalization. Good agreement was attained for the two observed direct detachment channels of all anions, except for the lowest-energy detachment channel of para-ethyl phenolate for which two conformations exist that yield very different PADs. The conformational freedom leads to an observed PAD that is the incoherent sum of the PADs from all conformers populated under experimental conditions. In contrast, a second detachment channel shows no sensitivity to the conformational flexibility of para-ethyl phenolate. Our results show that PADs can provide detailed information about the electronic structure of the anion and its conformations.