Amino acids, peptides and proteins

Abstract

Amino acids, peptides and proteinsPeptides 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 ana...

Improving the Quality of Frozen Lamb by Microencapsulated Apple Polyphenols: Effects on Cathepsin Activity, Texture, and Protein Oxidation Stability

“…On the one hand, microencapsulation of polyphenols may weaken the breaking of hydrogen bond, delay the formation of the intermolecular disulfide bond, and enhance the stability of the MP secondary structure during frozen storage. On the other hand, driven by electrostatic hydrophobic interactions, phenolic compounds interact with protein, improving protein stability; moreover, they maintain a higher α-helix content and lower random coils [ 41 ]. However, the addition of S4 further destroyed the secondary structure of the protein, which is consistent with the observation reported by Jia, Wang, Shao, Liu, and Kong [ 42 ], who observed that high concentrations of catechin could reduce the structural stability of MP under oxidative stress.…”

Recent developments in capillary and microchip electroseparations of peptides (2011–2013)

“…CE and CEC are nowadays accepted as recognized counterparts and/or complements of (ultra‐)HPLC and nano‐LC methods that remain the major tools for peptide analysis and preparation. In addition to the last one of the above reviews , the recent developments of CE and CEC separations of peptides were reported in some other reviews and an Electrophoresis special issue dealing with some particular aspects of CE and CEC of peptides, proteins, amino acids (AAs), and other biomolecules.…”