Influence of stabilizing osmolytes on hen egg white lysozyme fibrillation

Communicated by Ramaswamy H. Sarma.

Interactions in Ternary Aqueous Solutions of NMA and Osmolytes-PARAFAC Decomposition of FTIR Spectra Series

Intermolecular interactions in aqueous solutions are crucial for virtually all processes in living cells. ATR-FTIR spectroscopy is a technique that allows changes caused by many types of such interactions to be registered; however, binary solutions are sometimes difficult to solve in these terms, while ternary solutions are even more difficult. Here, we present a method of data pretreatment that facilitates the use of the Parallel Factor Analysis (PARAFAC) decomposition of ternary solution spectra into parts that are easier to analyze. Systems of the NMA–water–osmolyte-type were used to test the method and to elucidate information on the interactions between N-Methylacetamide (NMA, a simple peptide model) with stabilizing (trimethylamine N-oxide, glycine, glycine betaine) and destabilizing osmolytes (n-butylurea and tetramethylurea). Systems that contain stabilizers change their vibrational structure to a lesser extent than those with denaturants. Changes in the latter are strong and can be related to the formation of direct NMA–destabilizer interactions.

Amyloid fibril formation in the presence of water structure-affecting solutes

The impact of the differently hydrated non-electrolytes (protein structure destabilizers) on the fibrillation of hen egg white lysozyme (HEWL) was investigated. Two isomeric urea derivatives i.e. butylurea (BU) and N,N,N',N'-tetramethylurea (TMU) were chosen as a tested compounds. The obtained results show that butylurea exerts greater impact on HEWL and its fibrillation than tetramethylurea. Both substances decrease the time of induction of the fibrillation (lag time) but only BU increases the efficiency of amyloidogenesis. For the systems with equivalent reduction of the HEWL stability (250mM BU and 500mM TMU) the not-equivalent increase of the protein fibrillation was recorded (higher for BU). This fact suggests that specific interactions with protein, possibly water mediated, are responsible for the action of the tested substances.

Taurine as a water structure breaker and protein stabilizer

The enhancing effect on the water structure has been confirmed for most of the osmolytes exhibiting both stabilizing and destabilizing properties in regard to proteins. The presented work concerns osmolytes, which should be classified as "structure breaking" solutes: taurine and N,N,N-trimethyltaurine (TMT). Here, we combine FTIR spectroscopy, DSC calorimetry and DFT calculations to gain an insight into the interactions between osmolytes and two proteins: lysozyme and ubiquitin. Despite high structural similarity, both osmolytes exert different influence on protein stability: taurine is a stabilizer, TMT is a denaturant. We show also that taurine amino group interacts directly with the side chains of proteins, whereas TMT does not interact with proteins at all. Although two solutes weaken on average the structure of the surrounding water, their hydration spheres are different. Taurine is surrounded by two populations of water molecules: bonded with weak H-bonds around sulfonate group, and strongly bonded around amino group. The strong hydrogen-bonded network of water molecules around the amino group of taurine further improves properties of enhanced protein hydration sphere and stabilizes the native protein form. Direct interactions of this group with surface side chains provide a proper orientation of taurine and prevents the [Formula: see text] group from negative influence. The weakened [Formula: see text] hydration sphere of TMT breaks up the hydrogen-bonded network of water around the protein and destabilizes it. However, TMT at low concentration stabilize both proteins to a small extent. This effect can be attributed to an actual osmophobic effect which is overcome if the concentration increases.

Correction: Are stabilizing osmolytes preferentially excluded from the protein surface? FTIR and MD studies

Correction for 'Are stabilizing osmolytes preferentially excluded from the protein surface? FTIR and MD studies' by P. Bruździak et al., Phys. Chem. Chem. Phys., 2015, 17, 23155-23164.

Are stabilizing osmolytes preferentially excluded from the protein surface? FTIR and MD studies

Stabilizing osmolytes are not always preferentially excluded and can interact with the protein surface in two ways: indirectly or directly.

[Morphological evaluation of postnatal development of the rat ovary]

Follicular development represents one of the essential functions of the ovary. It was done a lot of various classifications including kinetics or morphometry of growing follicles. All these experiments were carried on adult animals and so very little was known about developing follicles in youngs. In the view of this, we decided to investigate the postnatal development of rat ovary. Ovaries from rats between 14-84 days were examined; our own modification was used for classification of follicles, the number of each type of follicles and their diameter was counted, the number of granulosa cells in small growing follicles was noted and diameter of luteal cell and its elements in luteal body in which ovulation took place, were described.