GenPipes: an open-source framework for distributed and scalable genomic analyses.

BACKGROUND: With the decreasing cost of sequencing and the rapid developments in genomics technologies and protocols, the need for validated bioinformatics software that enables efficient large-scale data processing is growing. FINDINGS: Here we present GenPipes, a flexible Python-based framework that facilitates the development and deployment of multi-step workflows optimized for high-performance computing clusters and the cloud. GenPipes already implements 12 validated and scalable pipelines for various genomics applications, including RNA sequencing, chromatin immunoprecipitation sequencing, DNA sequencing, methylation sequencing, Hi-C, capture Hi-C, metagenomics, and Pacific Biosciences long-read assembly. The software is available under a GPLv3 open source license and is continuously updated to follow recent advances in genomics and bioinformatics. The framework has already been configured on several servers, and a Docker image is also available to facilitate additional installations. CONCLUSIONS: GenPipes offers genomics researchers a simple method to analyze different types of data, customizable to their needs and resources, as well as the flexibility to create their own workflows.

Absolute cross section for low-energy-electron damage to condensed macromolecules: a case study of DNA.

Cross sections (CSs) for the interaction of low-energy electrons (LEE) with condensed macromolecules are essential parameters for accurate modeling of radiation-induced molecular decomposition and chemical synthesis. Electron irradiation of dry nanometer-scale macromolecular solid films has often been employed to measure CSs and other quantitative parameters for LEE interactions. Since such films have thicknesses comparable with electron thermalization distances, energy deposition varies throughout the film. Moreover, charge accumulation occurring inside the films shields a proportion of the macromolecules from electron irradiation. Such effects complicate the quantitative comparison of the CSs obtained in films of different thicknesses and limit the applicability of such measurements. Here, we develop a simple mathematical model, termed the molecular survival model, that employs a CS for a particular damage process together with an attenuation length related to the total CS, to investigate how a measured CS might be expected to vary with experimental conditions. As a case study, we measure the absolute CS for the formation of DNA strand breaks (SBs) by electron irradiation at 10 and 100 eV of lyophilized plasmid DNA films with thicknesses between 10 and 30 nm. The measurements are shown to depend strongly on the thickness and charging condition of the nanometer-scale films. Such behaviors are in accord with the model and support its validity. Via this analysis, the CS obtained for SB damage is nearly independent of film thickness and charging effects. In principle, this model can be adapted to provide absolute CSs for electron-induced damage or reactions occurring in other molecular solids across a wider range of experimental conditions.

Measurement of inelastic cross sections for low-energy electron scattering from DNA bases.

PURPOSE: To determine experimentally the absolute cross sections (CS) to deposit various amount of energies into DNA bases by low-energy electron (LEE) impact. MATERIALS AND METHODS: Electron energy loss (EEL) spectra of DNA bases were recorded for different LEE impact energies on the molecules deposited at very low coverage on an inert argon (Ar) substrate. Following their normalisation to the effective incident electron current and molecular surface number density, the EEL spectra were then fitted with multiple Gaussian functions in order to delimit the various excitation energy regions. The CS to excite a molecule into its various excitation modes were finally obtained from computing the area under the corresponding Gaussians. RESULTS: The EEL spectra and absolute CS for the electronic excitations of pyrimidine and the DNA bases thymine, adenine, and cytosine by electron impacts below 18 eV were reported for the molecules deposited at about monolayer coverage on a solid Ar substrate. CONCLUSIONS: The CS for electronic excitations of DNA bases by LEE impact were found to lie within the 10(216) to 10(218) cm(2) range. The large value of the total ionisation CS indicated that ionisation of DNA bases by LEE is an important dissipative process via which ionising radiation degrades and is absorbed in DNA.

Cross sections for low-energy electron scattering from adenine in the condensed phase.

Measurements of the vibrational and electronic excitation of a sub-monolayer up to a monolayer film of adenine were performed with a high resolution electron energy-loss (HREEL) spectrometer. The integral cross sections (over the half-space angle) for excitation of the normal vibrational modes of the ground electronic state and electronically excited states are calculated from the measured reflectivity EEL spectra. Most cross sections for vibrational excitation are of the order of 10(-17) cm(2), the largest being the out-of-plane wagging of the amino-group and the six-member ring deformations. A wide resonance feature appears in the incident energy dependence of the vibrational cross sections at 3-5 eV, while a weak shoulder is present in this dependence for combined ring deformations and bending of hydrogen atoms. For the five excited electronic states, at 4.7, 5.0, 5.5, 6.1 and 6.6 eV, the cross sections are of the order of 10(-18) cm(2), except in the case of the state at the energy of 6.1 eV, for which it is two to three times higher.

Products and reaction sequences in tetrahydrofuran exposed to low-energy electrons.

Electron-stimulated reactions in solid films of tetrahydrofuran (THF), condensed on Kr spacers deposited on a Pt substrate, or directly onto the substrate, were induced and monitored simultaneously with use of high-resolution electron-energy-loss spectroscopy in the ranges of vibrational and electronic excitations. The spectra of the molecular films obtained after a certain time of exposure to electrons at incident energies of 14 and 15.5 eV were analyzed and different products were identified. Besides an aldehyde, which is the main product, olefins, conjugated olefins, as well as CO were identified. Closer investigation of the reactions of propionaldehyde, as a model aldehyde, demonstrates that CO appears in THF as a secondary product (i.e., from the intermediate aldehyde). On the basis of the cross sections for the formation of an aldehyde from THF, of CO from propionaldehyde, and for the loss of propionaldehyde under electron impact, the reaction sequences were evaluated with the help of a kinetic model. This analysis suggests that some CO could also be formed directly from THF (i.e., without involvement of an intermediate aldehyde).