Editorial: advances in therapeutic glycopeptides.

Glycopeptides, peptides containing sugar β-amino acids, have significant impact on medicinal chemistry research and pharmaceutical industr. In 1956, the discovery of one classic glycopeptide, vancomycin, broke the dawn of a new age for antibacterial research. Employing glycopeptides for the therapeutic purposes used to be regarded as proposals. Owing largely to the recent improvements in separation practices, characterization techniques, synthetic methods, and biological research, these proposals have been transformed into ongoing research projects in many laboratories around the world. Previously known as antibiotics, glycopeptides have been used as chemotherapeutic, antiviral, antitubercular, antifungal, antiproliferative and apoptotic agents. Nowadays they are even considered for the development of HIV and cancer vaccines. While several of them are in clinical trials, it could be expected that in the near future, treatment regimen of such difficult diseases might be reformed accordingly. Many interesting preliminary results are being produced in this emerging area. As witnesses and practitioners in this exciting area, however, we notice that the related communication in public domain is still limited due to the relatively small number of researchers involved. Thus, we feel the necessity to compile a timely issue about the special topic "Advances in Therapeutic Glycopeptides", covering state-of-the-art research papers and expert reviews from this area. We are glad that Protein & Peptide Letters is willing to realize the idea with us. The opening paper of this issue by Dr. Voglmeir and coauthor discusses three types of PNGases in respect of their general properties and applications of the commercially available PNGases in glycopeptide and glycoprotein analysis. Dr. Liu and coauthors describe current techniques such as high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and mass spectrometry (MS), for the characterization of glycoproteins, with a focus on available therapeutic glycoproteins. Next three papers discuss the synthetic chemistry of glycopeptides. Dr. Zhu and coauthor describe a facile synthesis of differently protected cystathionines by the reaction of γ-bromohomoalanine with cysteine derivatives in an ethyl acetate/water biphasic system. Dr. Chen et al. report a neoglycopeptides synthesis by aqueous Suzuki-Miyaura reaction between glycosyl boronic acid and iodopeptides. Dr. Zeng et al. developed a novel strategy to prepare glycopeptide-based molecular imaging and therapy agents using fluorine-rich (fluorous) technology. The following review by Dr. Li et al. outlines a sample of mAbs currently approved for cancer treatment by the FDA, as well as antibody platforms in the research pipeline and clinic that have been engineered for greater tumor penetration, binding, and therapy efficacy. The asialoglycoprotein receptor (ASGPR) is a high-capacity C-type lectin receptor expressed on mammalian hepatocytes. Research in this field is summarized by Dr. Lu, Dr. Yin and coauthors. Recent progresses of cationic polysomes and liposomes as effective non-viral delivery system via ASGPR are also presented by these authors. Proteoglycans (PGs), a core protein and glycosaminoglycans (GAGs) chain, play important roles in amyloid-beta protein as well as tau processing, and have potential significance in Alzheimer's disease (AD) therapy. Next, Dr. Zeng and coworkers summarized recent advances of the chemistry and biology of glycopeptides with antibiotic activity. The last review of this issue by Dr. Ding and coworker provide the progress of PGs and GAGs in AD and their therapeutic implication. In summary, experts from different fields of therapeutic glycopeptides have showcased new results and expressed their opinions in this special thematic issue of Protein & Peptide Letters. As the guest editors, we wish that this diverse collection of valuable intellectual contributions will positively influence this emerging area and gain broad readership. At the end, we would like to express our sincerest gratitude to all authors and referees for their invaluable contribution to this issue. We would also like to extend our appreciation to Editor-in-Chief, Professor Ben M. Dunn and the staffs of Protein & Peptide Letters, especially Ms Rukhshanda Rehman, for their excellent support and for providing us with the opportunity to pursue this exciting project.