Modeling experimental design for proteomics

Toward a Sample Metadata Standard in Public Proteomics Repositories

Metadata is essential in proteomics data repositories and is crucial to interpret and reanalyze the deposited data sets. For every proteomics data set, we should capture at least three levels of metadata: (i) data set description, (ii) the sample to data files related information, and (iii) standard data file formats (e.g., mzIdentML, mzML, or mzTab). While the data set description and standard data file formats are supported by all ProteomeXchange partners, the information regarding the sample to data files is mostly missing. Recently, members of the European Bioinformatics Community for Mass Spectrometry (EuBIC) have created an open-source project called Sample to Data file format for Proteomics (https://github.com/bigbio/proteomics-metadata-standard/) to enable the standardization of sample metadata of public proteomics data sets. Here, the project is presented to the proteomics community, and we call for contributors, including researchers, journals, and consortiums to provide feedback about the format. We believe this work will improve reproducibility and facilitate the development of new tools dedicated to proteomics data analysis.

Label-Free Quantitative Phosphoproteomics for Algae

The unicellular alga Chlamydomonas reinhardtii is a model photosynthetic organism for the study of microalgal processes. Along with genomic and transcriptomic studies, proteomic analysis of Chlamydomonas has led to an increased understanding of its metabolic signaling as well as a growing interest in the elucidation of its phosphorylation networks. To this end, mass spectrometry-based proteomics has made great strides in large-scale protein quantitation as well as analysis of posttranslational modifications (PTMs) in a high-throughput manner. An accurate quantification of dynamic PTMs, such as phosphorylation, requires high reproducibility and sensitivity due to the substoichiometric levels of modified peptides, which can make depth of coverage challenging. Here we present a method using TiO₂-based phosphopeptide enrichment paired with label-free LC-MS/MS for phosphoproteome quantification. Three technical replicate samples in Chlamydomonas were processed and analyzed using this approach, quantifying a total of 1775 phosphoproteins with a total of 3595 phosphosites. With a median CV of 21% across quantified phosphopeptides, implementation of this method for differential studies provides highly reproducible analysis of phosphorylation events. While the culturing and extraction methods used are specific to facilitate coverage in algal species, this approach is widely applicable and can easily extend beyond algae to other photosynthetic organisms with minor modifications.

Interactive Web Tool for Standardizing Proteomics Workflow for Liquid Chromatography-Mass Spectrometry Data

INTRODUCTION

The proteomics experiments involve several steps and there are many choices available for each step in the workflow. Therefore, standardization of proteomics workflow is an essential task for design of proteomics experiments. However, there are challenges associated with the quantitative measurements based on liquid chromatography-mass spectrometry such as heterogeneity due to technical variability and missing values.

METHODS

We introduce a web application, Proteomics Workflow Standardization Tool (PWST) to standardize the proteomics workflow. The tool will be helpful in deciding the most suitable choice for each step of the experimentation. This is based on identifying steps/choices with least variability such as comparing Coefficient of Variation (CV). We demonstrate the tool on data with categorical and continuous variables. We have used the special cases of general linear model, analysis of covariance and analysis of variance with fixed effects to study the effects due to various sources of variability. We have provided various options that will aid in finding the contribution of sum of squares for each variable and the CV. The user can analyze the data variability at protein and peptide level even in the presence of missing values.

AVAILABILITY AND IMPLEMENTATION

The source code for "PWST" is written in R and implemented as shiny web application that can be accessed freely from https://ulbbf.shinyapps.io/pwst/.

Functional proteomics of barley and barley chloroplasts - strategies, methods and perspectives

Barley (Hordeum vulgare) is an important cereal grain that is used in a range of products for animal and human consumption. Crop yield and seed quality has been optimized during decades by plant breeding programs supported by biotechnology and molecular biology techniques. The recently completed whole-genome sequencing of barley revealed approximately 26,100 open reading frames, which provides a foundation for detailed molecular studies of barley by functional genomics and proteomics approaches. Such studies will provide further insights into the mechanisms of, for example, drought and stress tolerance, micronutrient utilization, and photosynthesis in barley. In the present review we present the current state of proteomics research for investigations of barley chloroplasts, i.e., the organelle that contain the photosynthetic apparatus in the plant. We describe several different proteomics strategies and discuss their applications in characterization of the barley chloroplast as well as future perspectives for functional proteomics in barley research.

Engineered biological entities for drug delivery and gene therapy protein nanoparticles

The development of genetic engineering techniques has speeded up the growth of the biotechnological industry, resulting in a significant increase in the number of recombinant protein products on the market. The deep knowledge of protein function, structure, biological interactions, and the possibility to design new polypeptides with desired biological activities have been the main factors involved in the increase of intensive research and preclinical and clinical approaches. Consequently, new biological entities with added value for innovative medicines such as increased stability, improved targeting, and reduced toxicity, among others have been obtained. Proteins are complex nanoparticles with sizes ranging from a few nanometers to a few hundred nanometers when complex supramolecular interactions occur, as for example, in viral capsids. However, even though protein production is a delicate process that imposes the use of sophisticated analytical methods and negative secondary effects have been detected in some cases as immune and inflammatory reactions, the great potential of biodegradable and tunable protein nanoparticles indicates that protein-based biotechnological products are expected to increase in the years to come.