Amino acids, peptides and proteins

TLDR: New approaches to the theoretical description of electromigration properties of proteins and peptides show that through the modeling of their CE-determined effective electrophoretic mobilities, the important physicochemical parameters, such as effective charge, Stokes radius, acidity constants of ionogenic groups, hydration and conformations of their molecules can be estimated.

Abstract: Peptides and proteins belong, together with nucleic acids, to the vitally important biopolymers. They play key roles in normal and pathological biological processes in all living organisms. Their variable biological functions involve acting as hormones, hormone and drug receptors, enzymes, co-enzymes, enzyme substrates or inhibitors, neurotransmitters, ionophores, growth factors, structural, locomotive and transport elements, drugs, antibiotics and toxins. Amino acids as building blocks of peptides and proteins, and as compounds ensuring several specific biological functions, also represent extremely important biomolecules. In the current era of proteomics, peptidomics and metabolomics, the relevance of amino acids, peptides and proteins is ever increasing. Hence, qualitative and quantitative analyses, separation, purification and characterization of these biomolecules are of great importance, and the application of different modes of capillary electrophoresis (CE) and capillary electrochromatography (CEC) in the above areas of proteomics, peptidomics and metabolomics belongs to the most exciting challenges for these advanced high-performance separation techniques. The high application potential of CE and CEC for amino acid, peptide and protein analysis, preparation and physicochemical and biochemical characterization is reflected also in the current special issue. CE and CEC emerge as fast, high-efficient and high-sensitive techniques for quality control and purity determination of pharmaceutical and other preparations of native and (bio)synthetic amino acids, peptides and proteins, for monitoring of their synthesis, isolation, chemical derivatization and enzymatic digestion, and also for investigation of their interactions with other (bio)molecules. New approaches to the theoretical description of electromigration properties of proteins and peptides show that through the modeling of their CE-determined effective electrophoretic mobilities, the important physicochemical parameters, such as effective charge, Stokes radius, acidity constants of ionogenic groups, hydration and conformations of their molecules can be estimated. Novel methodologies, e.g. combination of solid phase extraction and field-amplified sample injection for preseparation and preconcentration of peptides from complex biomatrices prior to their CE analyses, preparative-scale isoelectric trapping demonstrated by isolation of amino acids, iron nanoparticles-based separation of phosphorylated and non-phosphorylated proteins, new ways of size separation of proteins by CE with cationic hitchhiking or by fast capillary gel electrophoresis, preparation of monolithic immobilized pH gradients for isoelectric focusing of proteins and two-dimensional separations of complex peptide and protein mixtures by CE-mass spectrometry (MS) and LC-MS, are widely presented in this special issue. Preparation of new capillary coatings suppressing the adsorption of peptides and proteins to the fused silica capillary wall in their CZE analyses and/or increasing the selectivity of their open-tubular CEC separations remains a hot topic in the area of CE and CEC developments. The applications of CE and CEC methods include determination of lowabundant amino acids and peptides in complex matrices of wines and brain microdialysate by using high-sensitive laser induced fluorescence detection, peptide mapping of proteins by CE off-line coupled to MALDI-MS, investigation of peptide interactions with porphyrins by open tubular CEC, estimation of isoelectric point of human carbonic anhydrase isoforms by capillary isoelectric focusing and distinguishing of endogenous human hemoglobin from synthetic hemoglobin-based oxygen carriers by CE in doping control. I would like to express my thanks to all authors for their high-quality contributions and to the referees for careful reviews of the submitted manuscripts. I thank the Editor-in-Chief of Electrophoresis, Professor Ziad El Rassi, for inviting me to edit this special issue and for his help in the editorial work. Last but not least, I would like to thank my coworkers and family for understanding and support during the period of special issue preparation. Václav Kašička