Dielectric spectra broadening as a signature for dipole-matrix interactions. V. Water in protein solutions.

In this paper, the fifth of our series focused on the dielectric spectrum symmetrical broadening of water, we consider the solutions of methemoglobin (MetHb) in pure water and in phosphate-buffered saline (PBS). The universal character of the Cole-Cole dielectric response, which reflects the interaction of water dipoles with solute molecules, was described in Paper I [E. Levy et al., J. Chem. Phys. 136, 114502 (2012)]. It enables the interpretation of the dielectric data of MetHb solutions in a unified manner using the previously developed 3D trajectory method driven by the protein concentration. It was shown that protein hydration is determined by the interaction of water dipoles with the charges and dipoles located on the rough surfaces of the protein macromolecules. In the case of the buffered solution, the transition from a dipole-charged to a dipole-dipole interaction with the protein concentration is observed {see Paper III [A. Puzenko et al., J. Chem. Phys. 137, 194502 (2012)]}. A new approach is proposed for evaluating the amount of hydration water molecules bounded to the macromolecule that takes into account the number of positive and negative charges on the protein's surface. In the case of the MetHb solution in PBS, the hydration of the solvent ions and their interaction with charges on the protein's surface are also taken into consideration. The difference in hydration between the two solutions of MetHb is discussed.

Dielectric spectra broadening as a signature for dipole-matrix interaction. IV. Water in amino acids solutions.

In this paper, the fourth one of our series on the dielectric spectrum symmetrical broadening of water, we consider amino acid (AA) aqueous solutions. The developed 3D-trajectory is applied here to the variety of zwitterion amino acids representing both the hydrophobic and hydrophilic nature of their residues. The dipole moment of amino acids due to their zwitterion determines their interaction with the solvent and reflects mostly the dipole-matrix interactions described in our Paper I [E. Levy et al., J. Chem. Phys. 136, 114502 (2012)]. It is also shown that in the case of charged AAs at high concentrations, the shape of the 3D trajectory transforms to the pattern typical of the dipole-charge interactions that were described in our Paper III [A. Puzenko et al., J. Chem. Phys. 137, 194502 (2012)].

Hydration of AMP and ATP molecules in aqueous solution and solid films.

Water enables life and plays a critical role in biology. Considered as a versatile and adaptive component of the cell, water engages a wide range of biomolecular interactions. An organism can exist and function only if its self-assembled molecular structures are hydrated. It was shown recently that switching of AMP/ATP binding to the insulin-independent glucose transporter Human Erythrocyte Glucose Transport Protein (GLUT1) may greatly influence the ratio of bulk and bound water during regulation of glucose uptake by red blood cells. In this paper, we present the results on the hydration properties of AMP/ATP obtained by means of dielectric spectroscopy in aqueous solution and for fully ionized forms in solid amorphous films with the help of gravimetric studies.

Dielectric spectra broadening as the signature of dipole-matrix interaction. I. Water in nonionic solutions.

Whenever water interacts with another dipolar entity, a broadening of its dielectric relaxation occurs. Often this broadening can be described by the Cole-Cole (CC) spectral function. A new phenomenological approach has been recently presented [A. Puzenko, P. Ben Ishai, and Y. Feldman, Phys. Rev. Lett. 105, 037601 (2010)] that illustrates a physical mechanism of the dipole-matrix interaction underlying the CC behavior in complex systems. By considering the relaxation amplitude Δε, the relaxation time τ, and the broadening parameter α, one can construct a set of 3D trajectories, representing the dynamic behavior of different systems under diverse conditions. Our hypothesis is that these trajectories will contribute to a deeper understanding of the dielectric properties of complex systems. The paper demonstrates how the model describes the state of water in aqueous solutions of non-ionic solutes. For this purpose complex dielectric spectra for aqueous solutions of D-glucose and D-fructose are analyzed.

Dielectric spectra broadening as the signature of dipole-matrix interaction. II. Water in ionic solutions.

In this, the second part of our series on the dielectric spectrum symmetrical broadening of water, we consider ionic aqueous solutions. If in Part I, dipole-dipole interaction was the dominant feature, now ion-dipole interplay is shown to be the critical element in the dipole-matrix interaction. We present the results of high-frequency dielectric measurements of different concentrations of NaCl/KCl aqueous solutions. We observed Cole-Cole broadening of the main relaxation peak of the solvent in the both electrolytes. The 3D trajectory approach (described in detail in Part I) is applied in order to highlight the differences between the dynamics and structure of solutions of salts on one hand and dipolar solutes on the other hand.

Dielectric spectra broadening as a signature for dipole-matrix interaction. III. Water in adenosine monophosphate/adenosine-5'-triphosphate solutions.

In this, the third part of our series on the dielectric spectrum symmetrical broadening of water, we consider the nucleotide aqueous solutions. Where in Parts I [E. Levy et al., J. Chem. Phys. 136, 114502 (2012)] and II [E. Levy et al., J. Chem. Phys. 136, 114503 (2012)], the dipole-dipole or ion-dipole interaction had a dominant feature, now the interplay between these two types of dipole-matrix interactions will be considered. We present the results of high frequency dielectric measurements of different concentrations of adenosine monophosphate/adenosine-5'-triphosphate aqueous solutions. We observed the Cole-Cole broadening of the main relaxation peak of the solvent in the solutions. Moreover, depending on the nucleotide concentration, we observed both types of dipole-matrix interaction. The 3D trajectory approach (described in detail in Part I) is applied in order to highlight the differences between the two types of interaction.

Water is a biomarker of changes in the cellular environment in live animals.

The biological processes that are associated with the physiological fitness state of a cell comprise a diverse set of molecular events. Reactive oxygen species (ROS), mitochondrial dysfunction, telomere shortening, genomic instability, epigenetic changes, protein aggregation, and down-regulation of quality control mechanisms are all hallmarks of cellular decline. Stress-related and decline-related changes can be assayed, but usually through means that are highly disruptive to living cells and tissues. Biomarkers for organismal decline and aging are urgently needed for diagnostic and drug development. Our goal in this study is to provide a proof-of-concept for a non-invasive assay of global molecular events in the cytoplasm of living animals. We show that Microwave Dielectric Spectroscopy (MDS) can be used to determine the hydration state of the intracellular environment in live C. elegans worms. MDS spectra were correlative with altered states in the cellular protein folding environment known to be associated with previously described mutations in the C. elegans lifespan and stress-response pathways.

The dielectric spectroscopy of human red blood cells during 37-day storage: ß-dispersion parameterization.

This study exploits dielectric spectroscopy to monitor the kinetics of red blood cells (RBC) storage lesions, focusing on those processes linked to cellular membrane interface known as ß-dispersion. The dielectric response of RBC suspensions, exposed to blood-bank cold storage for 37 days, was studied using time-domain dielectric spectroscopy in the frequency range 500 kHz to 200 MHz. The measured dielectric processes are characterized by their dielectric strength (Δε) and their relaxation times (τ). Changes in the dielectric properties of the RBC suspensions, due to storage-related biophysical changes, were evaluated. For a quantitative characterization of RBC vitality, we characterized the shape of fresh and stored RBC and measured their deformability as expressed by their average elongation ratio, which was achieved under a shear stress of 3.0 Pa. During the second week of storage, an increment in the evolution of the relaxation times and in the dielectric permittivity strength of about 25% was observed. We propose that the characteristic increment of ATP, during the second and third weeks of storage, is responsible for the raise of the specific capacitance of cell membrane, which in turn explains the changes observed in the dielectric response when combined with the influence of the shape changes.

Dielectric properties of a novel colloidal oral matrix drug carrier.

Dielectric Spectroscopy (DS) was employed to study a novel oral matrix carrier (OMC), composed from silica nano-particles, polysaccharides, biopolymers and natural oils. This composition self-orders to a multi hierarchal structure and as such is amenable to be studied by techniques such as DS. The dielectric properties were measured in the frequency range 1MHz-1GHz and a temperature range 10°C-45°C. The results were dominated by two relaxation processes following CC relaxation and having relaxation times that are Arrhenius in nature. These processes can be traced to structural elements in the OMC and are influenced by the melting point of coconut oil, an essential element in the formulation. Furthermore, the correlations between dipolar entities in the OMC are investigated using Froelich's B function formulation. The results point to DS as an effective tool for the study of these systems.

Dielectric Response of Cytoplasmic Water and Its Connection to the Vitality of Human Red Blood Cells. II. The Influence of Storage.

Maintaining an appropriate inventory of packaged blood products is a critical part of modern medicine. Consequently, the assessment of red blood cell (RBC) functionality is instrumental for the monitoring of the quality of stored RBC (sRBC) in the blood bank. We present a comprehensive study of sRBC lesion kinetics in SAGM (saline, adenine, glucose, mannitol) solution, using microwave dielectric spectroscopy (0.5-50 GHz) and cell deformability. As part of the research, we have isolated the microwave dielectric response of cytoplasmic water in sRBC. The extracted dielectric parameters are sensitive to the age of the cells and, in particular, to the critical moment of transition from discocyte to echinocyte. From the analysis of the dielectric relaxation as a function of storage-duration, we postulate that the behavior is rooted in the delicate interplay between bound and bulk water in the cellular interior. In particular, the microwave dielectric response reflects the moment when the continuous diffusion of oxygen to the cell and the oxygenation of hemoglobin affects the role played by water in the maintenance of cell integrity. These results open a possible new avenue for the noninvasive inspection of stored red blood cells, permitting a true inventory system for the modern blood bank.

The dielectric spectroscopy of human red blood cells: the differentiation of old from fresh cells.

OBJECTIVE: The objective of the study was to gauge the effect of storage lesions on the dielectric response of red blood cells (RBC), in particular those processes linked to deformations of the cellular membrane known as the ß-dispersion. APPROACH: The dielectric response of RBC suspensions, exposed to blood-bank cold storage, was studied using time-domain dielectric spectroscopy (TDDS) in the frequency range of 500 kHz up to 1 GHz. The measured dielectric processes are characterized by their dielectric strength (Δε) and relaxation time (τ). Changes in the dielectric properties of the RBC suspensions due to storage-related lesions were evaluated. For a quantitative characterization of RBC lesions, we measured the deformability of fresh and stored RBC as expressed by their elongation ratio (ER), which was achieved under a shear stress of 3.0 Pa. MAIN RESULT: The results show that the storage of RBC induced a statistically significant decrease of dielectric relaxation times. In addition, a sound correlation between the mean values of ER and the relaxation times was observed (Spearman's correlation coefficient ρ = 0.847). We draw the conclusion that those alterations in the relaxation time are induced by changes in the shape of the RBC that happen during cold-storage. SIGNIFICANCE: The evolution of the ß-dispersion of RBC opens new possibilities in the blood bank inventory management.

Dielectric Response of Cytoplasmic Water and Its Connection to the Vitality of Human Red Blood Cells: I. Glucose Concentration Influence.

The vitality of red blood cells depends on the process control of glucose homeostasis, including the membrane's ability to "switch off" d-glucose uptake at the physiologically specific concentration of 10-12 mM. We present a comprehensive study of human erythrocytes suspended in buffer solutions with varying concentrations of d-glucose at room temperature, using microwave dielectric spectroscopy (0.5 GHz-50 GHz) and cell deformability characterization (the Elongation ratio). By use of mixture formulas the contribution of the cytoplasm to the dielectric spectra was isolated. It reveals a strong dependence on the concentration of buffer d-glucose. Tellingly, the concentration 10-12 mM is revealed as a critical point in the behavior. The dielectric response of cytoplasm depends on dipole-matrix interactions between water structures and moieties, like ATP, produced during glycolysis. Subsequently, it is a marker of cellular health. One would hope that this mechanism could provide a new vista on noninvasive glucose monitoring.