Aqueous solutions of NMA, Na2HPO4, and NaH2PO4 as models for interaction studies in phosphate–protein systems

Effect of ectoine on hydration spheres of peptides-spectroscopic studies

In this paper, we use FTIR spectroscopy to characterize the hydration water of ectoine, its interactions with two peptides-diglycine and NAGMA, and the properties of water molecules in the hydration spheres of both peptides changed by the presence of the osmolyte. We found that the interaction of ectoine with the peptide hydration shells had no effect on its own hydration sphere. However, the enhanced hydration layer of the osmolyte influences the hydration shells of both peptides and does so in a different way for both peptides: (1) the interfacial interaction of the NAGMA peptide and ectoine hydration spheres strengthened the hydration shell of this peptide; (2) the inclusion of water molecules from the ectoine hydration sphere into the diglycine hydration sphere had only a marginally enhancing effect. Since ectoine is being used in more and more biopharmaceutical products and cosmetics, knowledge of the properties of its hydration shell and its effect on the hydration shell of other molecules is extremely relevant to understanding its protective mechanism.

Incorporating the Antioxidant Fullerenol into Calcium Phosphate Bone Cements Increases Cellular Osteogenesis without Compromising Physical Cement Characteristics

Herein, fullerenol (Ful), a highly water-soluble derivative of C60 fullerene with demonstrated antioxidant activity, is incorporated into calcium phosphate cements (CPCs) to enhance their osteogenic ability. CPCs with added carboxymethyl cellulose/gelatin (CMC/Gel) are doped with biocompatible Ful particles at concentrations of 0.02, 0.04, and 0.1 wt v%-1 and evaluated for Ful-mediated mechanical performance, antioxidant activity, and in vitro cellular osteogenesis. CMC/gel cements with the highest Ful concentration decrease setting times due to increased hydrogen bonding from Ful's hydroxyl groups. In vitro studies of reactive oxygen species (ROS) scavenging with CMC/gel cements demonstrate potent antioxidant activity with Ful incorporation and cement scavenging capacity is highest for 0.02 and 0.04 wt v%-1 Ful. In vitro cytotoxicity studies reveal that 0.02 and 0.04 wt v%-1 Ful cements also protect cellular viability. Finally, increase of alkaline phosphatase (ALP) activity and expression of runt-related transcription factor 2 (Runx2) in MC3T3-E1 pre-osteoblast cells treated with low-dose Ful cements demonstrate Ful-mediated osteogenic differentiation. These results strongly indicate that the osteogenic abilities of Ful-loaded cements are correlated with their antioxidant activity levels. Overall, this study demonstrates exciting potential of Fullerenol as an antioxidant and proosteogenic additive for improving the performance of calcium phosphate cements in bone reconstruction procedures.

Assessing the effect of different pH maintenance situations on bacterial SERS spectra

Phenotyping of bacteria with vibrational spectroscopy has caught much attention in bacteria-related research. It is known that many factors could affect this process. Among them, solution pH maintenance is crucial, yet its impact on the bacterial SERS spectra is surprisingly neglected. In this work, we focused on two situations related to pH maintenance: the effect of the same buffer on the SERS spectra of bacteria under different pH values, and the influence of different buffers on the SERS spectra of bacteria under the same pH value. Specifically, Britton-Robison (BR) buffer was used to evaluate the effect of pH value on bacteria SERS spectra thanks to its wide pH range. Four different buffers, namely BR buffer, acetate buffer, phosphate buffer, and carbonate buffer, were used to illustrate the impact of buffer types on SERS spectra of bacteria. The results showed that the intensity and number of characteristic peaks of the SERS spectra of Gram-negative (G -) bacteria changed more significantly than Gram-positive (G +) bacteria with the change of pH value. Furthermore, compared with phosphate buffer and carbonate buffer, BR buffer could bring more characteristic SERS bands with better reproducibility, but slightly inferior to acetate buffer. In conclusion, the influence of the pH and types of the buffer on the SERS spectra of bacteria are worthy of further discussion.

DMSO and TMAO-Differences in Interactions in Aqueous Solutions of the K-Peptide

Interactions between a solvent and their co-solute molecules in solutions of peptides are crucial for their stability and structure. The K-peptide is a synthetic fragment of a larger hen egg white lysozyme protein that is believed to be able to aggregate into amyloid structures. In this study, a complex experimental and theoretical approach is applied to study systems comprising the peptide, water, and two co-solutes: trimethylamide N-oxide (TMAO) or dimethyl sulfoxide (DMSO). Information about their interactions in solutions and on the stability of the K-peptide was obtained by FTIR spectroscopy and differential scanning microcalorimetry. The IR spectra of various osmolyte-water-model-peptide complexes were simulated with the DFT method (B3LYP/6-311++G(d,p)). The FTIR results indicate that both solutes are neutral for the K-peptide in solution. Both co-solutes affect the peptide to different degrees, as seen in the shape of its amide I band, and have different influences on its thermal stability. DFT calculations helped simplify the experimental data for easier interpretation.

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.

Specific Buffer Effects on the Intermolecular Interactions among Protein Molecules at Physiological pH

BSA and lysozyme molecular motion at pH 7.15 is buffer-specific. Adsorption of buffer ions on protein surfaces modulates the protein surface charge and thus protein-protein interactions. Interactions were estimated by means of the interaction parameter k_D obtained from plots of diffusion coefficients at different protein concentrations (D_app = D₀[1 + k_DC_protein]) via dynamic light scattering and nuclear magnetic resonance. The obtained results agree with recent findings confirming doubts regarding the validity of the Henderson-Hasselbalch equation, which has traditionally provided a basis for understanding pH buffers of primary importance in solution chemistry, electrochemistry, and biochemistry.

N-Methylacetamide Aqueous Solutions: A Neutron Diffraction Study

The hydration of N-methylacetamide (NMA) in solution has been determined by neutron diffraction with isotopic Hydrogen/Deuterium substitution (NDIS), augmented by Monte Carlo simulation. This study is representative of the hydration of the peptide bonds characteristic of proteins and might shed light on aggregation phenomena in intrinsically disordered proteins. It is found that NMA forms hydrogen bonds with water at both O and H peptide sites, although of different lengths and strengths. The comparison with the case of tripeptide glutathione evidences differences in both hydration and propensity for aggregation.