Analysis of anthracycline antitumour drugs in tissues and body fluids using liquid chromatography

Anthracyclines, with doxorubicin as the major representative, are amongst the most important chemotherapeutic agents used in cancer therapy. In order to reduce the severe side effects associated with their use, and to increase therapeutic efficacy, analogue development still continues, and analytical requirements change concomitantly. The available methods for bioanalysis of anthracyclines are summarized, with emphasis on high-performance liquid chromatography. Attention is paid to sample pretreatment, the possibilities of liquid—liquid and solid-phase extraction, and the chromatographic behaviour of the anthracyclines.     

Directed evolution of cyclic peptides for inhibition of autophagy

In recent decades it has become increasingly clear that induction of autophagy plays an important role in the development of treatment resistance and dormancy in many cancer types. Unfortunately, chloroquine (CQ) and hydroxychloroquine (HCQ), two autophagy inhibitors in clinical trials, suffer from poor pharmacokinetics and high toxicity at therapeutic dosages. This has prompted intense interest in the development of targeted autophagy inhibitors to re-sensitize disease to treatment with minimal impact on normal tissue. We utilized Scanning Unnatural Protease Resistant (SUPR) mRNA display to develop macrocyclic peptides targeting the autophagy protein LC3. The resulting peptides bound LC3A and LC3B—two essential components of the autophagosome maturation machinery—with mid-nanomolar affinities and disrupted protein–protein interactions (PPIs) between LC3 and its binding partners in vitro. The most promising LC3-binding SUPR peptide accessed the cytosol at low micromolar concentrations as measured by chloroalkane penetration assay (CAPA) and inhibited starvation-mediated GFP-LC3 puncta formation in a concentration-dependent manner. LC3-binding SUPR peptides re-sensitized platinum-resistant ovarian cancer cells to cisplatin treatment and triggered accumulation of the adapter protein p62 suggesting decreased autophagic flux through successful disruption of LC3 PPIs in cell culture. In mouse models of metastatic ovarian cancer, treatment with LC3-binding SUPR peptides and carboplatin resulted in almost complete inhibition of tumor growth after four weeks of treatment. These results indicate that SUPR peptide mRNA display can be used to develop cell-penetrating macrocyclic peptides that target and disrupt the autophagic machinery in vitro and in vivo.

SUPR peptide mRNA display was used to evolve a cell-permeable, macrocyclic peptide for autophagy inhibition.     

Relativistic four-component calculations of Buckingham birefringence using London atomic orbitals

We present the first relativistic study of the electric-field-gradient induced birefringence (Buckingham birefringence), with application to the series of molecules CX₂ (X?=?O, S, Se, Te). A recently developed atomic-orbital-driven scheme for the calculation of time-dependent molecular properties using one-, two- and four-component relativistic wave functions (Bast et?al. in Chem Phys 356:177, 2009) is extended to first-order frequency-dependent magnetic-field perturbations, using London atomic orbitals to ensure gauge-origin independent results and to improve basis-set convergence. Calculations are presented at the Hartree?CFock and Kohn?CSham levels of theory and results for CO₂ and CS₂ are compared with previous high-level coupled-cluster calculations. Except for the heaviest member of the series, relativistic effects are small??in particular for the temperature-independent contribution to the birefringence. By contrast, the effects of electron correlation are significant. However, the reliability of standard exchange-correlation functionals in describing Buckingham birefringence remains unclear based on the comparison with high-level coupled-cluster singles-and-doubles calculations.     

Parity nonconservation contribution to the nuclear magnetic resonance shielding constants of chiral molecules: a four-component relativistic study

A systematic four-component relativistic study of the parity nonconservation (PNC) contribution to the (isotropic) NMR shielding constants of chiral molecules is presented for the P enantiomers of the series H(2)X(2) (X=(17)O,(33)S,(77)Se,(125)Te,(209)Po). The PNC contributions are obtained within a linear response approach at the Hartree-Fock level. A careful design of the basis sets is necessary. The four-component relativistic results based on the Dirac-Coulomb Hamiltonian are compared with the nonrelativistic Levy-Leblond results and those obtained by the spin-free modified Dirac Hamiltonian. The calculations confirm the nonrelativistic scaling law Z(2.4) of the PNC contribution with respect to nuclear charge Z. However, the calculations also show that the overall scaling is significantly modified by relativistic effects. The scalar relativistic effect scales as Z(4.7) for the selected set of molecules, whereas the spin-orbit effect, of opposite sign, scales better than Z(6) and completely dominates the PNC contribution for the heaviest elements. This opens up the intriguing possibility of the experimental observation of PNC effects on NMR parameters of molecules containing heavy atoms. The presented formalism is expected to be valuable in assisting the search for suitable candidate molecules.     

Large parity violation effects in the vibrational spectrum of organometallic compounds

Large parity violation effects of the order of 1 Hz are predicted for the vibrational spectrum of two organometallic species, Os(eta5-C5H5)(=CCl2)Cl(PH3) and Re(eta5-Cp*)(=O)(CH3)Cl. It should therefore be possible to detect such effects in molecules by high-resolution spectroscopy for the first time.     

Histopathological effects of the herbicide atrazine on gills of the Brazilian endemic bivalve Diplodon expansus

Due to their benthic filter-feeding habits and high bioaccumulation potential of metals and organic compounds, bivalve molluscs have been widely used in studies in the field and laboratory to assess the toxic effects of several compounds discharged in rivers, oceans and estuaries. However, most ecotoxicological studies use invasive exotic species, while the response of native species is poorly known. The Brazilian endemic species Diplodon expansus occurs in rivers near areas of intense agricultural activity, and atrazine is currently one of the main residues of pesticides found in water bodies of the Brazilian territory. This study was aimed at examining the toxicity of different atrazine concentrations to a Brazilian native mollusc by analysing the histology, histochemistry and ultrastructure of its gill filaments. The cells that comprise the frontal and intermediary regions of gill filaments were the most affected by the herbicide and responses associated with damage and protection were observed. The response of tissues and cells were dose-dependent. Higher concentrations of herbicide caused more severe alterations in large areas of the gills. The persistence of the alterations observed might result in severe functional problems in the gills of these animals, negatively affecting their performance and health.