Amino Acids, Peptides and Proteins

Václav Kašička Together with nucleic acids, peptides and proteins represent the most important biopolymers. They play key roles in biological processes in all living organisms. Their variable functions involve acting as hormones, hormone and drug receptors, enzymes, co-enzymes, enzyme substrates or inhibitors, neurotransmitters, ionophores, ion channels, 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 belong to extremely important biomolecules as well. In the current era of proteomics, peptidomics and metabolomics, the relevance of amino acids, peptides and proteins is ever increasing. Hence, qualitative and quantitative analysis, separation, purification and characterization of these biomolecules are of great importance and the application of capillary electrophoretic (CE), (electro)chromatographic (CEC and nano-LC) and mass spectrometric (MS) methods in the above areas of proteomics, peptidomics and metabolomics belongs to the most challenging tasks of these advanced high-performance separation techniques. A large applicability of CE and CEC methods as well as nano-LC and MS techniques for analysis, isolation, identification and characterization of amino acids, peptides and proteins is demonstrated also in this special issue. All these techniques emerge as fast, high-efficient and high-sensitive techniques for quality control and purity determination of native and (bio)synthetic amino acids, peptides and proteins, for monitoring of their synthesis, isolation, isomerization, chemical derivatization and enzymatic digestion, and for determination of these biomolecules in complex biomatrices. It is shown that from effective electrophoretic mobilities of peptides it is possible to extract important physicochemical parameters, such as acidity constants of their ionogenic groups and slip length in the slipping friction between their molecules and background electrolyte. New advanced methodologies, such as application of carbon nanotubes for sample preparation, microfluidic-based nano-LC-MS/MS approach for proteomic analysis of human epithelial fluid, CZE-ESITOF MS analysis of nitrated major birch pollen allergen, micellar electrokinetic chromatography with a volatile surfactant compatible with ESI-MS detection for analysis of native amino acids and static coatings for CZE analyses of intact monoclonal antibody drugs are presented here. The applications of CE and CEC methods include determination of amino acids and peptides in complex matrices of human urine and saliva, tea samples and seed milks, isolation of sarcosin from urine by modified paramagnetic particles in a microfluidic chip, quantification of proteins in cerebrospinal fluid and inclusion bodies, protein profiling of plant extracts, electrophoretic monitoring of enzymatic activities and investigation of peptide mediated human immunoglobulin bioconjugation with quantum dots. I would like to express my thanks to all authors for their high-quality contributions and to the referees for carefully reviewing 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 the special issue preparation. I do hope that this collection of papers, reflecting and summarizing the recent advances and developments in the area of analysis, isolation and characterization of amino acids, peptides and proteins, will be enjoyable and stimulating for the readers of this special issue.