Size exclusion chromatography of polypeptides on Bio-Gel P2 in the dynamic axial compression mode

The effect of dynamic axial compression (DAC) upon the structure of a bed packed with semirigid Bio-Gel P2 and its chromatographic parameters was studied in the separation of peptides of various mass. In the studied range of DAC pressure, 0–5 bar, a decrease in the retention times of the studied substances and the standard deviation of their peaks is observed. In spite of a reduced packed bed height and an increase in the linear velocity of the eluent, the height equivalent to the theoretical plate (HETP) does not rise. The resolution of the separated substances increases throughout the studied range of DAC pressure with the Bio-Gel P2 exclusion limit extended. According to the results obtained, DAC provides more efficient optimisation of the bed parameters in columns packed with Bio-Gel P2 than in columns packed with Sephadex G-25 due to the greater rigidity of the former packing.     

Synthesis and Self‐assembly of a Helical Polymer Grafted from a Foldable Polyurethane Scaffold

Herein a polyurethane graft poly‐l ‐glutamate amphiphilic copolymer was synthesized from a polyurethane (PU)‐based macro‐initiator (containing pendant primary amine groups) through the ring opening polymerization of N‐carboxy anhydride of γ‐benzyl‐l ‐glutamate ( BLG‐NCA ). On average, twenty two l ‐glutamic acids were grafted from each amino group which was pendant on the polyurethane chain with 10 repeating units. The grafted polymer ( PU‐PP‐1 ) exhibits self‐assembly to produce a hydrogel in a wide pH window ranging from pH 5.0 to 8.0 with a critical gelation concentration (CGC) of 5.0 wt % (w/v) at pH 7.4. Furthermore, circular dichroism study revealed the transition of the α‐helix to a random coil upon increasing the pH. Due to the protonation of side chains at pH 4.0, PU‐PP‐1 adopted an α‐helical conformation whereas at pH >8.0 the side‐chain carboxylic acid groups of the PLGAs were ionized, leading to the formation of an extended random coil conformation as a result of charge repulsion. Conformational switching was also supported by FTIR spectroscopy.     

Role of the organic solvent modifier in the reversed phase high-performance liquid chromatography of polypeptides

Summary The retention behaviour of several polypeptide hormones on Bondapak C₁₈ columns has been examined using mobile phases of different acetonitrile percentage compositions containing 15 mM triethylammonium phosphate or 15 mM orthophosphoric acid buffers. Under these elution conditions, the capacity factors and the selectivity parameters of these polypeptide hormones show pronounced dependencies on the volume fraction of the organic solvent modifier. In the range 0–40% acetonitrile, the capacity factors were monotonously attenuated with increasing modifier percentages with the elution order essentially in accord with that hat anticipated for a reversed phase separation mode. At higher concentrations of acetonitrile, retention of the polypeptides to the octadecylsilica support progressively increased with elution order reversals indicative of a normal- or polarphase separation mode. These observations are discussed in terms of the interplay of hydrophobic and silanophilic interactions which occur between the ionised polypeptides and the stationary phase under these changing mobile phase conditions.High Performance Liquid Chromatography of Amino Acids, Peptides and Proteins, XXXII. For previous publication see ref. [1].     

Polypept(o)ide-based bactericides: weapons against antibiotic-resistant bacterial infections

Emerging antibiotic resistance in bacterial pathogens has necessitated the development of alternative ‘outside of the box’ antimicrobial therapeutics. Polypept(o)ide-based bactericides with chemical structures mimicking antimicrobial host defense peptides have emerged as promising candidates for treating antibiotic-resistant and recurring infections. This review summarizes the recent advances in membrane-active polypept(o)ide-based bactericides in the treatment of antibiotic-resistant bacterial infections associated with the physical disruption of bacterial cell walls/cell membranes. Among these polypept(o)ide-based bactericides, nonantibiotic treatment strategies are employed to combat lethal bacterial strains resulting from acquired antibiotic resistance and biofilm formation, featuring the capacity to evade acquired antibiotic resistance-related mechanisms and to alleviate the emergence of drug resistance. Emphasis will focus on the typical polypept(o)ides with diverse molecular conformations (e.g., linear, brush-like, and star-shaped) and various chemical structures of monomers (e.g., α-amino acid, β-amino acid, and N-substituted glycine) that are central to the performance of antimicrobial polypept(o)ides. Finally, a brief discussion of the key challenges and prospects of polypept(o)ide-based bactericides is presented.