Alkane hydroxylases involved in microbial alkane degradation

This review focuses on the role and distribution in the environment of alkane hydroxylases and their (potential) applications in bioremediation and biocatalysis. Alkane hydroxylases play an important role in the microbial degradation of oil, chlorinated hydrocarbons, fuel additives, and many other compounds. Environmental studies demonstrate the abundance of alkane degraders and have lead to the identification of many new species, including some that are (near)-obligate alkanotrophs. The availability of a growing collection of alkane hydroxylase gene sequences now allows estimations of the relative abundance of the different enzyme systems and the distribution of the host organism

Poly(amidoamine)s synthesis, characterisation and interaction with BSA

Cationic poly(amidoamine)s (PAAs) were synthesised and characterised by NMR and gel permeation chromatography. Their thermal properties were investigated using thermogravimetric analysis and differential scanning calorimetry. Although poly(amidoamine)s have been used as endosomolytic polymers for protein intracellular delivery, the interaction of the polymers with the proteins still need to be investigated. BSA was used as a model protein and complexation with the different poly(amidoamine) s was investigated using gel retardation assays, fluorescence spectroscopy and high sensitivity differential scanning calorimetry. Our results indicate that the thermal stability of BSA was affected upon interaction and complexation with the poly(amidoamine)s, however these interactions did not seem to modify the structure of the protein. Polymer flexibility seemed to favour polymer/protein complexation and promoted thermal stability

The Possible "Proton Sponge " Effect of Polyethylenimine (PEI) Does Not Include Change in Lysosomal pH.

Polycations such as polyethylenimine (PEI) are used in many novel nonviral vector designs and there are continuous efforts to increase our mechanistic understanding of their interactions with cells. Even so, the mechanism of polyplex escape from the endosomal/lysosomal pathway after internalization is still elusive. The “proton sponge ” hypothesis remains the most generally accepted mechanism, although it is heavily debated. This hypothesis is associated with the large buffering capacity of PEI and other polycations, which has been interpreted to cause an increase in lysosomal pH even though no conclusive proof has been provided. In the present study, we have used a nanoparticle pH sensor that was developed for pH measurements in the endosomal/lysosomal pathway. We have carried out quantitative measurements of lysosomal pH as a function of PEI content and correlate the results to the “proton sponge ” hypothesis. Our measurements show that PEI does not induce change in lysosomal pH as previously suggested and quantification of PEI concentrations in lysosomes makes it uncertain that the “proton sponge ” effect is the dominant mechanism of polyplex escape