Industrial polymer keeps photosynthetic proteins stable in water
Researchers from the FOM Foundation and Utrecht University in collaboration with British colleagues from Bristol University have discovered that the polymer styrene maleic anhydride (SMA), keeps photosynthetic membrane proteins stable in water. This discovery offers new possibilities for isolating and characterising membrane proteins. The results of the research were published on 11 September 2014 in Angewandte Chemie.
From light to energy
The use of photosynthetic proteins in technological applications is increasing, as these proteins are capable of converting light energy into electricity. They can therefore be put to good use in biosensors, electronic circuits and biosolar cells, for example. In nature, photosynthetic proteins play a role in the energy supply of bacteria, algae and plants. For applications, however, the proteins need to be isolated from their natural host. This is a particularly difficult task because the proteins are contained in lipid membranes. Removing the proteins from the membranes requires the use of chemicals that work like a soap. These substances capture proteins in the same way as fat is removed from clothing using a detergent. Unfortunately though, the protein often loses its characteristics as soon as it is captured in the soap because the membrane breaks. The researchers therefore sought a way of maintaining the membrane structure so that the proteins could be kept stable.
Super soap
The researchers studied a protein from the bacterium Rhodobacter sphaeroides. Instead of standard soap-like molecules they used the polymer SMA to isolate the protein and discovered that this not only led to the successful isolation of the protein but a good stability as well. The membrane was found to be even more stable than when the protein is in its natural environment. "This is because the immediate lipid environment is preserved and each protein is contained in its own polymer packaging. Consequently the protein cannot be influenced by its environment like it is in the membrane", explains FOM PHD researcher Stefan Scheidelaar. This result could bring the application of photosynthetic proteins in solar cells, example, a step closer.
Step to better research
The use of the SMA polymer can improve the research into lipid membranes and the functioning of membrane proteins, because proteins can now be studied in their natural environment. For such research it is also convenient that the SMA polymers dissolve the pieces of membrane in the form of a nanodisc in which the polymer forms a sort of ring around the piece of membrane. As a consequence of this the protein is far more accessible than in its natural environment. In cells, membrane proteins are found isolated in compartments and only the part that sticks outside the membrane can react directly with substances added. With the open structures of the nanodiscs, however, both sides of the protein are accessible.
A better understanding of membrane proteins could also be of great value for the medical world, as these proteins are frequently the targets of medicines. The SMA polymer might therefore help researchers to gain a better understanding of how medicines do their work in our bodies.
To further investigate the highly promising possibilities of the SMA polymer, the researchers have entered into a collaboration with the Dutch polymer company Polyscope from Geleen. This company manufactures the SMA polymer for applications in areas such as the automobile and plastics industries.
Further information
Stefan Scheidelaar, Utrecht University