Peptide drug development has made great progress in the last decade thanks to new production, modification, and analytic technologies. Peptides have been produced and modified using both chemical and biological methods, together with novel design and delivery strategies, which have helped to overcome the inherent drawbacks of peptides and have allowed the continued advancement of this field. A wide variety of natural and modified peptides have been obtained and studied, covering multiple therapeutic areas. This review summarizes the efforts and achievements in peptide drug discovery, production, and modification, and their current applications. We also discuss the value and challenges associated with future developments in therapeutic peptides.
The management of bacterial infections is becoming a major clinical challenge due to the rapid evolution of antibiotic resistant bacteria. As an excellent candidate to overcome antibiotic resistance, antimicrobial peptides (AMPs) that are produced from the synthetic and natural sources demonstrate a broad-spectrum antimicrobial activity with the high specificity and low toxicity. These peptides possess distinctive structures and functions by employing sophisticated mechanisms of action. This comprehensive review provides a broad overview of AMPs from the origin, structural characteristics, mechanisms of action, biological activities to clinical applications. We finally discuss the strategies to optimize and develop AMP-based treatment as the potential antimicrobial and anticancer therapeutics.
The epithelial mesenchymal transition (EMT) plays a central role in both normal physiological events (e.g., embryonic development) and abnormal pathological events (e.g., tumor formation and metastasis). The processes that occur in embryonic development are often reactivated under pathological conditions such as oncogenesis. Therefore, defining the regulatory networks (both gene and protein levels) involved in the EMT during embryonic development will be fundamental in understanding the regulatory networks involved in tumor development, as well as metastasis. There are many molecules, factors, mediators and signaling pathways that are involved in the EMT process. Although the EMT is a very old topic with numerous publications, recent new technologies and discoveries give this research area some new perspective and direction. It is now clear that these important processes are controlled by a network of transcriptional and translational regulators in addition to post-transcriptional and post-translational modifications that amplify the initial signals. In this review article, we will discuss some key concepts, historical findings, as well as some recent progresses in the EMT research field.
Long-chain-branched isotactic polypropylenes (LCBed PP) were synthesized by copolymerizing
propylene with a small amount of nonconjugated α,ω-diene (1,9-decadiene or 1,7-octadiene) using
the catalyst system of rac-Me2Si(2-MeBenz[e]Ind)2ZrCl2(MBI)/MMAO. In this approach, the LCB
structures were introduced by the incorporation of in situ generated macromonomers with
pendant 1-octenyl or 1-hexenyl groups during the polymerization. A detailed study on the effects
of diene concentration on polymer properties was conducted. Polymer chain microstructures
were characterized by 13C NMR, GPCV, and DSC. In the propylene/1,9-decadiene copolymerization, a series of LCBed polymer samples with the long-chain-branch density (LCBD) of up to
0.53 branch structures per 1000 carbons were produced with the diene concentrations of 0.177−3.54 mmol/L at 40 and 25 °C. A diene concentration of 35.4 mmol/L yielded cross-linked polymer
gels. In the copolymerization of propylene and 1,7-octadiene, in addition to a small fraction of
LCB structures produced, a cyclic seven-member ring structure was observed due to the
cycloaddition of 1,7-octadiene. The cyclization significantly decreased the LCBD in the polymers.
A small-amplitude oscillatory shear flow measurement was conducted to evaluate the rheological
properties of the LCBed polymers. Compared to the linear samples prepared at the same
polymerization conditions, the LCBed polymers exhibited enhanced low-frequency complex
viscosity, improved shear-thinning, increased dynamic moduli, and reduced phase angle. The
samples also showed thermorheological complexity and enhanced activation energy at low
frequencies. These particular properties are related to the LCB in the polymers and become
more significant with the increase of LCBD. The LCBed polypropylenes were also blended with
their counterpart linear samples and demonstrated the improvement of rheological properties.
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