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- ItemWater Dynamics in the Hydration Shells of Biomolecules(Washington, DC : ACS Publ., 2017) Laage, Damien; Elsaesser, Thomas; Hynes, James T.The structure and function of biomolecules are strongly influenced by their hydration shells. Structural fluctuations and molecular excitations of hydrating water molecules cover a broad range in space and time, from individual water molecules to larger pools and from femtosecond to microsecond time scales. Recent progress in theory and molecular dynamics simulations as well as in ultrafast vibrational spectroscopy has led to new and detailed insight into fluctuations of water structure, elementary water motions, electric fields at hydrated biointerfaces, and processes of vibrational relaxation and energy dissipation. Here, we review recent advances in both theory and experiment, focusing on hydrated DNA, proteins, and phospholipids, and compare dynamics in the hydration shells to bulk water.
- ItemConcentrations and Uptake of Dissolved Organic Phosphorus Compounds in the Baltic Sea(Lausanne : Frontiers Media, 2018-12-10) Nausch, Monika; Achterberg, Eric P.; Bach, Lennart T.; Brussaard, Corinna P. D.; Crawfurd, Katharine J.; Fabian, Jenny; Riebesell, Ulf; Stuhr, Annegret; Unger, Juliane; Wannicke, NicolaThe dissolved organic phosphorus (DOP) pool in marine waters contains a variety of different compounds. Knowledge of the distribution and utilization of DOP by phyto- and bacterioplankton is limited, but critical to our understanding of the marine phosphorus cycle. In the Baltic Sea, detailed information about the composition of DOP and its turnover is lacking. This study reports the concentrations and uptake rates of DOP compounds, namely, adenosine triphosphate (dATP), deoxyribonucleic acid (dDNA), and phospholipids (dPL), in the Baltic Proper and in Finnish coastal waters in the summers of 2011 and 2012. Both areas differed in their dissolved inorganic phosphorus (DIP) concentrations (0.16 and 0.02–0.04 μM), in the C:P (123–178) and N:P (18–27) ratios, and in abundances of filamentous cyanobacteria and of autotrophic and heterotrophic picoplankton. The mean concentrations of dATP-P, dDNA-P, and dPL-P were 4.3–6.4, 0.05–0.12, and 1.9–6.8 nM, respectively, together contributing between 2.4 and 5.2% of the total DOP concentration. The concentrations of the compounds varied between and within the investigated regions and the distribution patterns of the individual components are not linked to each other. DIP was taken up at rates of 10.1–380.8 nM d-1. dATP-P and dDNA-P were consumed simultaneously with DIP at rates of 6.9–24.1 and 0.09–0.19 nM d-1, respectively, with the main proportion taken up by the size fraction <3 μm and with DIP to be the dominant source. Groups of hydrographical and biological parameters were identified in the multiple regression analysis to impact the concentrations and uptake rates. It points to the complexity of the regulation. Our results indicate that the investigated DOP compounds, particularly dATP-P, can make significant contributions to the P nutrition of microorganisms and their use seems to be not intertwined. Therefore, more detailed knowledge of all DOP components including variation of concentrations and the utilization is required to understand the roles of DOP in marine ecosystems.
- ItemThe interaction of chondroitin sulfate with a lipid monolayer observed by using nonlinear vibrational spectroscopy(Cambridge : RSC Publ., 2021) Szekeres, Gergo Peter; Krekic, Szilvia; Miller, Rebecca L.; Mero, Mark; Pagel, Kevin; Heiner, ZsuzsannaThe first vibrational sum-frequency generation (VSFG) spectra of chondroitin sulfate (CS) interacting with dipalmitoyl phosphatidylcholine (DPPC) at air–liquid interface are reported here, collected at a laser repetition rate of 100 kHz. By studying the VSFG spectra in the regions of 1050–1450 cm−1, 2750–3180 cm−1, and 3200–3825 cm−1, it was concluded that in the presence of Ca2+ ions, the head groups together with the head-group-bound water molecules in the DPPC monolayer are strongly influenced by the interaction with CS, while the organization of the phospholipid tails remains mostly unchanged. The interactions were observed at a CS concentration below 200 nM, which exemplifies the potential of VSFG in studying biomolecular interactions at low physiological concentrations. The VSFG spectra recorded in the O–H stretching region at chiral polarization combination imply that CS molecules are organized into ordered macromolecular superstructures with a chiral secondary structure.
- ItemEffect of head group and lipid tail oxidation in the cell membrane revealed through integrated simulations and experiments([London] : Macmillan Publishers Limited, part of Springer Nature, 2017-7-18) Yusupov, M.; Wende, K.; Kupsch, S.; Neyts, E. C.; Reuter, S.; Bogaerts, A.We report on multi-level atomistic simulations for the interaction of reactive oxygen species (ROS) with the head groups of the phospholipid bilayer, and the subsequent effect of head group and lipid tail oxidation on the structural and dynamic properties of the cell membrane. Our simulations are validated by experiments using a cold atmospheric plasma as external ROS source. We found that plasma treatment leads to a slight initial rise in membrane rigidity, followed by a strong and persistent increase in fluidity, indicating a drop in lipid order. The latter is also revealed by our simulations. This study is important for cancer treatment by therapies producing (extracellular) ROS, such as plasma treatment. These ROS will interact with the cell membrane, first oxidizing the head groups, followed by the lipid tails. A drop in lipid order might allow them to penetrate into the cell interior (e.g., through pores created due to oxidation of the lipid tails) and cause intracellular oxidative damage, eventually leading to cell death. This work in general elucidates the underlying mechanisms of ROS interaction with the cell membrane at the atomic level.