PCCP Blog

More than 50 % of our bodies are water. Plain and simple, we are more water than anything else. Following that statement it must be said that none of the water in our body is simply water. Excluding the content of your bladder, none of the water in your body is water as you have come to know it from your glass, rain, your local river and the oceans. Your body water surrounds cell membranes, microtubule, proteins, sugars, bones; all the smaller and larger biomolecules that make up our bodies. Not to mention the specific concentrations of salts and inorganic molecules that are required to run our bodies. We are beginning to understand the structure of water itself, and when water solvates simple ions. The work of Takis and co-workers increases the stakes and opens our mind to the specific solvations of small protein fragments.

The research from the groups of Troganis and Melissas at the University of Ioannina is focused on simple dipeptides, and exploits molecular dynamic simulations, density functional theory based calculations and advanced nuclear magnetic resonance spectroscopy. This combination allows them to probe the solvation of the small peptide experimentally, and rationalize the findings by the theoretical approach. Specifically the distances between selected carbon atoms in the peptide structure and water molecules can be measured. The challenge in this approach is the continuous and rapid exchange of the water molecules.

To me, the most readily accessible data is the plots showing the probability of finding water oxygen and hydrogen atoms at a specific distance to selected groups in the peptide structure. Here, extracted from MD simulations. When experimental data can yield similar results, we will be able to start directly investigating how more than half of our bodies are made up.

The excellent work on the solvation of dipeptides is published in the PCCP paper titled:

Probing micro-solvation in “numbers”: the case of neutral dipeptides in water
Panteleimon G. Takis, Konstantinos D. Papavasileiou, Loukas D. Peristeras, Vasilios S. Melissas and Anastassios N. Troganis
Phys. Chem. Chem. Phys., 2013, 15, 7354-7362
DOI: 10.1039/C3CP44606A

by Thomas Just Sørensen

Sometimes you just have to sit back, read, and enjoy the ride. This is exactly the case with the work of Kirsten Harth and Ralf Stannarius from the Institute of Experimental Physics at the Otto von Guericke University Magdeburg. The have investigated the interface tension between soapy water and a smectic liquid crystal.

Apparently, thin films of smectic—and only smectic—liquid crystals readily form in water, where they can form bubbles. In an ingenious experimental set-up Harth and Stannarius can measure the surface tension by letting a single air bubble put the smectic film bubble under tension. Amazing as it sounds, it is a viable procedure and the interface tension can be accurately determined.

The generic appeal of this study makes it one of the more enjoyable reads I have had in a while. The images were just so interesting that my curiosity forced me to download and read the paper.

If you are equally enticed, the paper is published in PCCP:

Measurement of the interface tension of smectic membranes in water
Kirsten Harth and Ralf Stannarius
Phys. Chem. Chem. Phys., 2013, 15, 7204-7209
DOI: 10.1039/C3CP44055A

by Thomas Just Sørensen

In the modern world of fast paced research and a stronger focus on when there is enough data for a paper, rather than when we are sure we know the subject under study, it is a pleasure to read the paper “Properties and self-assembled packing morphology of long alkyl-chained substituted polyhedral oligomeric silsesquioxanes (POSS) cages” from the lab of Professor Alan R. Bassindale. In this paper every rock has been turned and you can, either by scrutinizing the data, or by reading the paper, get introduced to polyhedral oligomeric  silsesquioxane cages and the difference in packing between cages with a spacer group and without.

Ellen L. Heeley and co-workers take us through the investigation of the phases of two POSS cages, one with long alkyl chains directly affixes to the corners of the cages, and one where a flexible liner is introduced between the cage and the alkyl chain. A quite drastic effect in the packing of the alkyl chains in the molecular materials is found. There is no room in the cages with directly attached alkyl chains for the molecules to form an interdigitated alkyl layer in the structure. In the system where there is able room to interdigitate, a lamellar-like structure is obtained, with segregated layers of alkyl-grease and layers of glass-boxes.

To see the data first hand go to:

Properties and self-assembled packing morphology of long alkyl-chained substituted polyhedral oligomeric silsesquioxanes (POSS) cages
Ellen L. Heeley, Darren J. Hughes, Youssef El Aziz, Ian Williamson, Peter G. Taylor and Alan R. Bassindale
Phys. Chem. Chem. Phys., 2013, 15, 5518-5529.
DOI: 10.1039/C3CP44356F

by Dr Thomas Just Sørensen