Peptide-based molecular gels

Compared to peptide-based molecular gels, studies and applications of saccharide-based molecular gels are still limited. Despite their potential as a matrix for cell immobihzation and encapsulation, saccharide-based gelators usually have complex structures, which have limited their application for tissue engineering [48]. 

Hofsten and Lalasidis (15), however, reported that plasteins subjected to gel exclusion chromatography in 50X acetic acid showed no increase in molecular size over that of the reactants. Monti and dost (29) reached the same conclusion based on gel chromatography in DMSO and on analysis of a-amino nitrogen in plasteins. Hofsten and Lalasidis (15) noted that hydrophobic peptides showed unusual elution behavior on sephadex gels in water or dilute buffers, providing a possible explanation for differences in their results compared to those of Arai et al. 

Viscotoxin, a basic peptide of molecular weight ca. 9000 (Samulsson, 1961), moves unretarded in strongly cross-linked gels such as Sephadex G-25 (Fig. 4a) (in phosphate buffer, ionic strength 0.05, pH 6.8. When filtered under similar conditions in weakly cross-linked dextran, viscotoxin behaves quite differently (Fig. 4b). In fact it moves behind isoleucine. The gel of the first kind can be used to remove solutes of lower molecular size, the purification being based on molecular exclusion. Filtration in the second kind of gel may be used not only for separating solutes of different molecular size but also to separate peptides and other substances of similar molecular size when they differ in certain structural features. 

Psoriatic inhibitor has a molecular mass of 9 kDa based on gel permeation, and is not active against PPE [86]. Due to the limited data available, it is not clear whether psoriatic inhibitor and elafin are different peptides or whether variation in isolation techniques have resulted in partial degradation of the native inhibitor to produce these differences. In this regard, it should be noted that when the molecular mass of elafin is estimated by gel permeation it also yields a value of 9 kDa. 

Becker et al. [64] functionalized a peptide, based on the protein transduction domain of the HIV protein TAT-1, with an NMP initiator while on the resin. They then used this to polymerize f-butyl acrylate, followed by methyl acrylate, to create a peptide-functionahzed block copolymer. Traditional characterization of this triblock copolymer by gel permeation chromatography and MALDI-TOF mass spectroscopy was, however, comphcated partly due to solubility problems. Therefore, characterization of this block copolymer was mainly hmited to ll and F NMR and no conclusive evidence on molecular weight distribution and homopolymer contaminants was obtained. Difficulties in control over polymer properties are to be expected, since polymerization off a microgel particle leads to a high concentration of reactive chains and a diffusion-limited access of the deactivator species. The traditional level of control of nitroxide-mediated radical polymerization, or any other type of controlled radical polymerization, will therefore not be straightforward to achieve. 

The most prominent field of applications for microchip—MS concerns identification and analysis of large molecules in the field of proteomics according to the reduced separation time compared to conventional approaches such as gel-based methods for protein analysis. High-throughput analyses, with lower contamination and disposability, are other features of microfabricated devices that allow the fast screening of proteomic samples in the clinical field. Applications also include the analysis of low-molecular-weight compounds such as peptides or pharmaceutical samples. 

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